Histological Images Lab Review

ДНІПРОПЕТРОВСЬКА ДЕРЖАВНА МЕДИЧНА АКАДЕМІЯ
DNIPROPETROVSK STATE MEDICAL ACADEMY
КАФЕДРА ГІСТОЛОГІЇ
DEPARTMENT OF HISTOLOGY
Histological Images
and
Lab Review
Part One – General Histology
Igor V. Tverdokhleb, Ph.D.
(Department of Histology, Dnipropetrovsk State Medical Academy)
Дніпропетровськ - 2013
Dnipropetrovsk - 2013
Epithelium and Simple Glands – 3
Stains, Cells, and Ultrastructure (EM) – 12
Connective Tissue Proper – 27
Connective Tissue Cells – 31
Blood and Capillaries – 35
Neural Tissue – 40
Muscle – 49
Specialized Connective Tissue: Cartilage and Bone – 56
Endochondral Ossification – 61
Bone Marrow and Hemopoiesis – 67
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Part 1: Epithelium and Simple Glands
Slide 1
Mesothelium seen as if looking down on a surface view to see "pavement" effect of the lining
cells. Silver stains the intercellular cement dark
between adjacent cells. Notice how corrugated
the cell membranes are. Mesothelium = the
simple squamous epithelium lining body cavities and mesenteries.
Slide 2
High power view of endothelial cells lining a
small blood vessel cut in cross-section. (You
see just the nuclei - the cytoplasm between
them is extremely flat.) Endothelium = the simple squamous epithelium lining blood vessels.
Slide 3
Low power view of larger vessels, showing endothelial nuclei lining the lumen. The yellowish
cells filling each vessel's lumen are blood cells.
Slide 4
Simple cuboidal epithelium lining a tubule
(longitudinal cut). Some of the cell boundaries
between "blocks" or "cubes" here are quite distinct.
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Slide 5
Simple cuboidal epithelium in Mallory stain
(longitudinal cut). Note the dark chromatin
clumps in the nuclei. Underneath the epithelium
lies a small blood vessel filled with orangecolored blood cells.
Slide 6
Cross-section of tubules. The smaller ones clustered in the center and upper left are lined by
simple squamous epithelium. The larger pink
tubules have simple cuboidal epithelium.
Slide 7
A tubule stained to show the pink basement
membrane underlying the base of the simple
cuboidal epithelium. Stained with periodic acid
Schiff reagent (PAS), which stains mucopolysaccharides.
Slide 8
Simple columnar epithelium with very regular
line-up of nuclei.
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Slide 9
Simple columnar cells cut tangentially to show
how they form a very regular "pavement" when
viewed from the surface. The cells are like tall
blocks arranged very closely to each other with
a small amount of tissue fluid in between.
Slide 10
Detail of simple columnar epithelium with
striated border (microvilli). Notice that the border is quite thin and the striations close together, looking like very regular, closely set brush
bristles.
Slide 11
EM of cells with striated border. Notice the
evenness and regularity of the microvilli. This
is an adaptation of the cell surface for absorption. Notice also the corrugation of the cell
boundaries as they fit next to each other. 1=
nucleus;
2=brush
border
(microvilli);
3=lymphocyte.
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Slide 12
Detail of simple columnar epithelium with a
goblet cell secreting mucus. The thin, clearly
defined band along the top epithelial surface is
the striated border, though the individual striations (or microvilli) are not visible at this magnification. The lower edge of the striated border
is the location of the terminal web; the dots
along the line of the web, seen in between the
individual epithelial cells, are the so-called terminal bars, which are found in EM to consist of
various cell junctions.
Slide 13
EM of apical (top) surface of two epithelial
cells whose cell membranes lie next to each
other. The microvilli (1) of the striated border
are very straight and regimented in appearance.
Microfilaments within them can be seen extending down into the terminal web (2), which
is an aggregate of fine filaments lying in the
cell cytoplasm. Several junctional complexes
are seen including tight junction (zonula occludens =3); intermediate junction (zonula adherens =4); and desmosome (macula adherens
=5).
Slide 14
Four rows of simple columnar epithelium facing each other in pairs (left and right) across a
narrow lumen or channel that lies in the middle
of each pair. (This is a Mallory Trichrome
stain.) The goblet cells are filled with blue mucoid secretion which is being poured into the
narrow lumens. Notice that in all four rows of
epithelium there is a narrow band of striated
border next to the lumen; the dark purple line at
the base of the border is the terminal web. Look
at the right hand rows of epithelial cells and notice the dark dots all along the terminal web
lines; these dots represent the junctional complexes between cells. The central cavity in the
picture is a blood vessel with endothelium, surrounded by a very cellular connective tissue.
Separating this connective tissue from the epi6
thelium is a thin blue layer of connective tissue
fibers.
Slide 15
Pseudostratified ciliated columnar epithelium
from the trachea. Nuclei are at different levels.
All cells touch the basement membrane, but
only the taller cells reach the lumen. The cilia
are longer and less regular than the microvilli of
a striated border.
Slide 16
Pseudostratified ciliated columnar epithelium
with pale goblet cells. The different levels of
nuclei are clearer here. Again, notice the wavylooking cilia.
Slide 17
Surface view of cilia with scanning EM scope.
Notice how "ragged" the surface seems -- cilia
were caught as they moved.
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Slide 18
Transitional epithelium of the urinary bladder,
low power view. It is a stratified epithelium
with several layers of cells.
Slide 19
Transitional epithelium, high power. Notice
many layers of cells -- and the typically puffy
surface cells. The bladder is contracted so the
epithelium is thick. If the bladder were
stretched, the epithelium would be thinner.
Slide 20
Stratified squamous non-cornified epithelium -medium power. This is from the esophagus, so
the surface is moist and living. Surface cells are
squamous and still nucleated. Basal layer is
very distinct; compare this with the less distinct
basal layer of the preceding slide of transitional
epithelium.
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Slide 21
Stratified squamous epithelium with beginning
surface cornification. This section is from thin
skin, which has a dry surface covered with dead
cells. Notice how flat the surface cells are and
how dark and pyknotic their nuclei have become. Again, notice the distinct row of basal
cells.
Slide 22
Thickly cornified stratified squamous epithelium. The cells in the bright red layer and in the
pale layers above it are completely flattened
and dead, and have lost their nuclei.
Slide 23
Diagram of GI wall to show various kinds of
glands -- some within the wall and some without (like the liver). These glands have ducts that
empty into the lumen of the gut. In all cases, the
epithelium lining the ducts and glands is continuous with the epithelium lining the lumen
(cavity) of the gut. (Note: the test-tube-like
glands, labeled "crypts of Lieberkuhn" here, are
the same kind as the intestinal glands you saw
under the microscope in the appendix in lab.)
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Slide 24
Unicellular gland - a goblet cell mucussecreting. (H & E stain.)
Slide 25
Goblet cells (blue) scattered throughout simple
columnar epithelial lining (special quad stain).
Slide 26
Simple tubular glands of gut wall seen in low
power. These glands are lined with epithelium
throughout their whole extent.
Slide 27
Detail of such a gland. Goblet cells are purple
here. -(H & E)
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Slide 28
Low power of wall of esophagus showing duct
at right, leading down to simple tubulo-alveolar
gland with coiled secretory portions.
Slide 29
Drawings of compound tubulo-alveolar glands - showing the branching of their duct system -and a few secretory end-pieces (alveoli). Ducts
and alveoli are lined with epithelium.
Slide 30
High power of typical mucous (pale) and serous
(darker pink) secretory cells. Notice that the
nuclei of mucous cells are dark and flattened at
the base of the cells, while the nuclei of serous
cells are round and more centrally located at
their cells. Mucous secretion is relatively thick
and viscous; serous secretion is watery.
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Part 2: Stains, Cells, and Ultrastructure (EM)
Slide 41
Hematoxvlin and eosin (H&E) is the most common
laboratory stain. Hematoxylin is a blue/purple dye;
eosin is red. Nuclear chromatin has a high nudeic
acid content and therefore is attracted to the blue,
more basic dye (i.e., it is basophilic). Everything else
in this picture is relatively neutral in character and
takes a wash of eosin.
Slide 42
In a low power view of intestinal wall, rows of epithelial nuclei impart a darker, bluer color to linings
of surfaces and glands, as seen to the right of center.
The outer, left-hand layers show the pink of muscle
cytoplasm. The middle layer of dense, irregular connective tissue shows how brightly collagen fibers
can be stained with eosin.
Slide 43
High power of smooth muscle to show that eosinophilic color is mainly due to cytoplasm. Nuclei are
quite scattered and have only small, granular clumps
of blue heterchromatin. Nucleoli (one or two per
nucleus) are stained blue with hematoxylin.
Slide 44
Intestinal wall stained with Mallory's trichrome
stain, which specifically colors collagen fibers blue.
With this stain the connective tissue layer is clearly
distinguished from muscle below and epithelium
above, both of which take the pink/purple stain of
cytoplasm.
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Slide 45
Detail of a group of epithelial cells containing bright
red (eosinophilic) secretory granules. Nuclei are dark
with hematoxylin.
Slide 46
This organ, the thymus, appears very basophilic in
H&E.
Slide 47
At high power, the reason for the basophilia is clear:
the thymus is packed with lymphocytes with darkly
stained nuclei. Isolated structures such as the whorl
of cells in the center, are specifically acidophilic (eosinophilic).
Slide 48
Here are some nerve cells, seen in low power. Their
nuclei are pale and vesicular, containing mainly unstained euchromatin. The nucleolus is dark, however, and the cvtoplasm is filled with clumps of darkly
stained, basophilic material, implying a content of
ribonucleic acid.
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Slide 49
Cells take diverse shapes. These are epithelial cords
of block-like cells. As always, nucleoli and nuclear
heterochromatin stain darkly with hematoxylin.
Slide 50
Blood cells are suspended in fluid plasma and therefore are characteristically round in shape.
Slide 51
Muscle cells are arranged parallel to their direction
of contraction and adopt a fusiform or spindle shape.
Nuclei are sparse in relation to large amounts of cytoplasm.
Slide 52
In low power, individual muscle cell groups are
found to be running in different directions, so that
some are cut cross-wise (or transversely) and some
are cut lengthwise (longitudinally). Some, of course,
are running obliquely and therefore are cut tangentially in relation to their full length.
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Slide 53
Nerve cells are typically stellate in shape, with several cytoplasmic extensions or processes. Here
again, notice that the cytoplasm of these cells contains dark, basophilic material. In EM, this material
will turn out to be abundant rough endoplasmic reticulum, which is associated with protein production.
Before leaving this slide, note the many tiny nuclei
in the field, in between the two nerve cells. Their
size is about equal to the nucleolus of a nerve cell!
Slide 54
Another type of nerve cell, to show again its huge
size in relation to the ordinary connective tissue cells
around it. Once again, the nucleolus of the nerve cell
(lying in the rather small, pink nucleus) is about
equal in size to the nuclei of other cells. Look just
below the nerve cell (at about the 5:30 position on a
clock face) for a small capillary containing a single,
quite pink erythrocyte. Figuring that the r.b.c. is
about 7.5 microns in diameter, you can estimate the
size of the neuron!
Slide 55
Silver staining is useful for a variety of purposes.
Here it is used to blacken the reticular fiber network
of reticular tissue.
Slide 56
Here silver has been deposited on nerve cells and
their delicate processes in the brain.
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Slide 57
In this instance, silver has been deposited on the intercellular substance between epithelial cells. You
will notice that silver seems particularly useful for
viewing very thin, fine structures which become visible when impregnated with grains of silver. Incidentally, this particular view is of the surface of mesothelium (simple squamous epithelium lining body
cavities and mesentery).
Slide 58
Now a whole-mount of a small blood vessel has
been stained with silver. The thin black vertical lines
are reticular fibers running around the outside of the
vessel like barrel hoops. The irregular horizontal
lines, running parallel to the length of the vessel are
the silvered outlines of endothelial cells. The intercellular cement has been stained black, making this
surface view of the endothelium look like the pieces
of a puzzle interlocked together. Cell nuclei are not
visible.
Slide 59
EM of a "typical" cell (hepatocyte), showing the organelles common to almost all cells of the body. Notice rod-like mitochondria (M), stacked rough endoplasmic reticulum, and electron-dense lysosomes.
The small dots encrusting the rough ER are ribosomes; compare their size with the particles of glycogen, shown as black, irregular clusters. Notice also
that the nucleus (N) contains very little heterochromatin, and seeming gaps along the nuclear envelope
where the nuclear pores are found (We'll get back to
other features of this cell when we study the liver.)
B=bile canniculus; HS=hepatic sinusoid; SD=space
of Disse.
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Slide 60
Transmission electron micrograph of nucleus similar
to the one in the previous figure. The nucleolus (3)
shows an internal structure. The chromatin is predominately euchromatin with heterochromatin which
is typically located close to the nuclear envelope and
is discontinuous at the nuclear pores. Mitochondria
(2) are seen in the surrounding cytoplasm.
Slide 61
Detailed EM of nucleolar structure, showing fibrillar
(1), granular (2), and amorphous (3) portions.
Slide 61a
A lymphocyte in late prophase. The nuclear
envelope has begun to disappear and is evident in
only a few places. (Arrow) CG = Chromatin granules. M = Mitochondria Rer = Rough endoplasmic
reticulum.
Slide 61b
A lymphocyte in metaphase with the chromosomes
lined up on the equatorial plate. The plane of section
does not include the spindle fibers. 1 = Endoplasmic
reticulum. 2 = Mitochondria.
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Slide 62
EM of the nuclear envelope. Dense chomatin material (heterochromatin) (1) is distributed along the
nuclear envelope except in the region of the nuclear
pores (2). 3=euchromatin; 4=smooth endoplasmic
reticulum; 5=Golgi body.
Slide 62a
Higher magnification micrograph with nucleus to the
left and cytoplasm to the right. A pore in the nuclear
envelope is marked by the arrow. Notice the absence
of heterochromatin at the site of the pore. N = Nucleus.
Slide 62b
EM of an oocyte with its nucleus (5) at the bottom of
the micrograph. The nuclear envelope is sectioned
tangentially so that nuclear pores are clearly visible
(arrows). 1 = Crystalline bodies or plaques (typical
of oocyte cytoplasm); 2 = Mitochondria; 3 = Multi
vesicular body; 4 = Cortical granules (typical of oocyte); 5 = Nucleus.
Slide 63
EM showing the two dense and one pale (or lucent)
layers of the ordinary cell (or plasma) membrane.
Slide 64
A similar membrane coated with a fuzzy-looking
external glycocalvx (arrow). GA=Golgi apparatus.
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Slide 65
Electron micrograph of the basal lamina. The portion
of the basal lamina referred to as the lamina densa
(1) is a thin gray line lying just outside the cell
membrane. Reticular fibers (2) are associated with
the lamina densa. Notice here that the basal lamina
surrounds an epithelial cell. Two odd points to remember: (1) lymphatic capillaries have no basal lamina surrounding their endothelium, and (2) fat cells
do have a basal lamina, which is surprising because
these are connective tissue cells and shouldn't seem
to need a protective layer between themselves and
the surrounding connective tissue ground substance.
The true origin of fat cells is open to question.
Slide 66
Diagram of a block-like cell showing the extent of
various kinds of cell junctions. A macula is a simple
"spot weld". A zonula forms a complete belt of adhesion around the cell. A fascia is a broad, irregular
area of adhesion. Notice that the apical surface of the
cell has several small cytoplasmic protrusions. They
are like microvilli stucturally but are not numerous
enough to form a striated or brush border. Such
small protrusions are common on cells.
Slide 67
Scanning EM view looking down on the apical surface of a whole sheet of epithelial cells. The long,
wavy projections are cilia: the close-cropped ones
are microvilli of a brush border.
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Slide 68
High power EM of microvilli of a brush border. Notice that they are simple extensions of the apical cytoplasm, with unit membrane continuing over their
surface. Very fine actin filaments extend into the microvilli and are rooted in the main mass of cytoplasm
below. Angling down the bottom half of the picture
is the line of contact between two adjacent cells,
each with its own unit membrane. At three points
along the way there are specialized junctions: (1)
zonula occludens or tight junctions, (2) zonula adherens or intermediate junction, and (3) desmosome or
macula adherens. Cytoplasmic filaments (arrow) are
attached to the desmosome, contributing to its density.
Slide 69
Lower magnification EM of junctional complexes
between epithelial cells. The tonofilaments heading
into the desmosomes (5) are particularly prominent.
The continuous bands of zonula occludens (3) and
zonula adherens (4) are seen near the top. Note the
width of the intercellular space along its normal
length and at the points of various kinds of contacts.
1=microvilli; 2=terminal web.
Slide 70
EM detail of several desmosomes, showing the attachment of many tonofilaments. Arrows point to the
density which typically appears in the intercellular
space. The cell membranes of the two neighboring
cells are interlocked in a very complex interdigitation here. You can follow the undulating course of
the intercellular space across the picture.
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Slide 71
EM detail of junctional complexes. In the area of the
tight junction (1) (zonula occludens) the two unit
membranes approach each other and appear to merge
revealing only three dense lines (instead of four). In
the area of the intermediate junction (2) (zonula adherens) the intercellular space narrows to about 20
nm, but there is still a space.
Slide 72
EM of cilia cut longitudinally. (A few microvilli are
on the neighboring cell to the left, for a size comparison.) Notice that each cilium is rooted in a barrellike basal body. The dense lines extending from the
basal bodies and up into the cilia are microtubules.
The unit membrane of the cell continues up over
each cilium.
Slide 73
Cross-cuts of cilia showing the typical 9X2 +2 arrangement of microtubules within the cytoplasm (
ring of 9 doublets plus 2 single microtubules in the
center). The cell membrane envelopes each cilium.
Slide 73a
Tangential section of cilia showing the structural
transitions that occur between the shaft of the cilia
(upper right) and the basal bodies (lower left) which
give rise to the cilia.
Slide 74
EM of hepatocyte illustrating size relationships between glycogen particles (1 and 2) and ribosomes of
the RER (3).
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Slide 75
Typical arrangement of cisterns of rough ER in a
secretory epithelial cell. A few mitochondria (1) are
at the lower right. The presence of ribosomes on the
RER, with all their ribonucleic acid content, render
them basophilic to stains. 2=secretory granule.
Slide 76
Serous secretory acini showing cytoplasmic basophilia toward their bases where a lot of rough ER lies.
The presence of rough ER in such abundance signifies production of protein (in this case, some digestive enzyme). The secretory granules are pale here.
Slide 77
Details of a Golgi apparatus (body) showing the
forming face (1); maturing face (2); saccules (3) and
secretory vesicles (4) budding from the saccules.
The Golgi complex typically lies adjacent to the nucleus. 5= centriole.
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Slide 78
High magnification of a network of smooth endoplasmic reticulum. Unlike rough endoplasmic reticulum, which usually occurs in flat sheets, this organelle comprises interconnected tubules (1). 2 = Mitochondrion; 3 = Free ribosomes, seen either singly
or as Polyribosomes (polysomes).
Slide 79
EM of microtubules, seen as fine parallel lines when
cut longitudinally (lower panel) or circles when cut
transversely (upper panel). Images are from dendrites and axons of neurons.
Slide 80
EM of plasma membrane infoldings (PF) and mitochondria (M) that are aligned parallel to the membranes. Note the basal lamina (BL) at the base of the
cells.
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Slide 81
Part of a lymphocyte showing a centriole (C) cut
transversely. Note the triplet arrangement of microtubules cut in cross-section. GA = Golgi apparatus
(body); PR = Polyribosomes (polysomes); NS = Perinuclear space (of the nuclear envelope).
Slide 82
Part of a lymphocyte showing continuity of the
rough endoplasmic reticulum (rer) with the nuclear
envelope (at arrow).
Slide 83
Cytoplasmic organelles of a renal collecting duct
cell. TL = Tubular lumen; MV = Microvilli on cell
surface; M = Mitochondrion; PR = Polyribosomes
(polysomes); GA = Golgi apparatus (body); IS = Intercellular space; notice how corrugated the interdigitations of the cell membranes are between the two
cell. (lower right).
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Slide 84
Details of mitochondria. 1 = External envelope; 2 =
Cristae; 3 = Matrix (the more electron-dense material); 4 = Granules within the matrix.
Slide 85
Large lipid droplets (LD) are seen within a cell in
the deeper parts of the adrenal cortex. The lipid matrix has been removed during tissue preparation. M =
Mitochondria (with tubular cristae are typical of steroid producing cells); SER = Smooth endoplasmic
reticulum.
Slide 86
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Detail of secondary lysosome with engulfed material
within it. 1 = Limiting membrane; 2 = Matrix; 3 =
partly digested material.
Slide 87
Different stages of the pinocytosis, an endocytic
process, in an endothelial cell. The vessel lumen is to
the right; the underlying connective tissue is to the
left. Notice the thin gray (electron-dense) line of the
basal lamina immediately along the left border of the
cell. 1 = Vesicle open to the outside of cell, facing
the extracellular matrix; 2 = Vesicle partially enclosed by cell membrane; 3 = Vesicle limited by
membrane and wholly within cytoplasm of cell. The
elongate nucleus lies in the center of the cell.
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Part 3: Connective Tissue Proper
Slide 1
Mesenchyme -- embryonic c.t. with multipotential
cells. The stellate cells are beginning to form fibers.
Sometimes cells are more spindle shaped. Ground
substance material is watery and invisible.
Slide 2
Reticular tissue (silvered, black). A network of very
fine reticular fibers can be seen here, forming the
stroma (framework) of a lymph node. These fibers
are produced by reticular cells. The pale cells seen in
the meshes of the reticular fibers are lymphocytes.
Slide 3
Stellate reticular cells - forming a meshwork of their
own cytoplasmic processes. These are in addition to
the reticular fiber network which these cells produce
-- and which we would see if this tissue were silvered. Notice particularly clear cells in upper left
quadrant of field. This slide is from lymph node.
Slide 4
Detail of lymph node, showing stellate reticular cell
in middle of field.
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Slide 5
Loose (areolar) connective tissue - (in blue) - surrounding the epithelium of tubules. In areas like this,
the finest collagen fibers lying closest to the tubules
would be reticular fibers; the only way to distinguish
them here from heavier collagen fibers would be to
silver them. (The blue here simply stains collagen in
general.) REMEMBER: in an area like this, reticular
fibers (like all other fibers) are produced by fibroblasts. Only in the primitive reticular tissue of bone
marrow, lymph node, and spleen are reticular fibers
produced by reticular cells.
Slide 6
Loose irregular connective tissue (also called areolar
tissue) as seen underlying and supporting epithelium
in an ordinary section. It is rather cellular and supports many small blood vessels which travel through
it.
Slide 7
Areolar c.t. immediately underlying simple columnar
epithelium. This is a very cellular variety of areolar
c.t., with a high population of lymphocytes.
Slide 8
A stretched preparation of areolar connective tissue.
The pink fibers of different thicknesses are collagenous (or white) fibers. The dark, thin, more tortuous
fibers are elastic (or yellow) fibers. Most of the nuclei belong to fibroblasts.
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Slide 9
Dense irregular c. t., with fibers running in all directions. The fibers are mainly collagenous, but keep in
mind that some would be elastic and can be seen only if specifically stained. This kind of c.t. is found
where firmer packing and binding is needed. The
two arrows at top of picture are pointing to elongate,
dark, fibroblast nuclei.
Slide 10
Dense irregular c.t. (blue) packing around a nerve
bundle. The coat immediately surrounding the whole
nerve bundle is particularly dense and consists mainly of collagen fibers. In between the individual pale,
round nerve fibers is a very fine areolar c.t. packing,
with mainly reticular fibers.
Slide 11
Fat cells -- note nucleus and rim of cytoplasm
pushed to one side by the accumulation of fat. The
lipid itself has been dissolved out in fixation. In the
center of the picture, in the space bounded by the
four large fat cells, there is a small, round cross-cut
of a capillary with a dark, shrunken red blood cell
inside.
Slide 12
Fat cells developing in areolar connective tissue.
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Slide 13
Adipose tissue aggregate of fat cells.
Slide 14
Adipose tissue as seen in a regular histological section. The pale pink tissue mixed in with it is skeletal
muscle. The dark purple = serous glands. There is a
small muscular artery in the middle, with a branch
going off it to the left.
Slide 15
Tendon (dense, regular c.t.), cut longitudinally. The
thick collagen fibers (pink) are lined up parallel to
each other, in response to the stress placed on them
by muscle and joint action. Fibroblasts are squeezed
between the fibers and therefore also line up in parallel rows. We often refer to this as a "railroad
train" appearance.
Slide 16
Tendon, cut in cross-section. The pale pink background represents the cut ends of bundles of thick
collagen fibers, very closely packed together. The
wispy lines you see throughout are the "cracks" between fiber bundles. In the cracks lie fibroblasts
which often look triangular or stellate because of
being squeezed between the fibers.
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Part 4: Connective Tissue Cells
Slide 21
Areolar c.t. -- the thin cell running diagonally toward
the lower right from the center is a fibroblast
Slide 22
Another fibroblast -- in the curve of the pink collagen fiber. The long, narrow nucleus is characteristic.
Slide 23
Several fibroblasts, lying among collagen fibers.
Hardly any cytoplasm is visible.
Slide 24
EM of cytoplasm of fibroblast that is actively producing collagen precursors. Since collagen is a protein, we are not surprised to see a prominent rough
endoplasmic reticulum. RER cisterns are packed
with granular synthetic product (1). Two mitochondria (2) are visible. On the upper left-hand surface of
the fibroblast, notice that secreted tropocollagen is
beginning to condense into fibrillar form.
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Slide 25
Two large macrophages (one on either side of the
picture) -- with engulfed particles of blue dye in their
cytoplasm. Their nuclei are pink. Compare the irregular sizes of the blue phagocytized particles here
with the more even-sized granules of the mast cells
in the next two slides. Notice also that the particles
in the macrophage are scattered randomly.
Slide 26
Mast cells in areolar c.t. -- their cytoplasm full of
purple secretory granules , which often seem to be
spilling out. The granules contain precursors of histamine and heparin. The nuclei are hidden by the
granules.
Slide 27
Mast cells -- deep purple metachromatic stain for
granules. Again, granules are spilling out as a result
of the preservation techniques. Notice how round
and seed-like the granules are and how tightly they
are packed in the cell. The cell nuclei are light blue.
Slide 28
Three large, dark mast cells in a stretched preparation of areolar connective tissue. In H & E the secretory granules stain a deep red color. Most of the other nuclei in the field belong to fibroblasts.
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Slide 29
EM of a rat mast cell, showing typically large, homogeneously dense granules in the cytoplasm. On
the left side of the micrograph, notice the presence
of collagen fibrils in the extracellular space. Their
presence is diagnostic for connective tissue.
Slide 30
EM of a human mast cell, showing a different structure for the secretory granules. Instead of being homogenous, the granules contain lamellae, whorls,
and so-called paracrystalline structures. They are
often described as "hair curlers" or "hair rollers"! In
this picture they don't seem very densely packed, but
their function seems to be very similar to that of
mast cells of other species.
Slide 31
Plasma cell -- with somewhat basophilic cytoplasm
and an eccentric nucleus with dark blocks of chromatin in it. Note the pale cytoplasmic area to the left
of the nucleus; this is the negative Golgi body. Note
also the pink collagen fibers scattered irregularly
throughout the pale ground substance of the whole
field, which is typical of areolar connective tissue.
Slide 32
Another plasma cell with eccentric nucleus and
smooth, basophilic cytoplasm. The large, elongate,
pale nucleus to the right of center belongs to a fibroblast; its cytoplasm is not visible.
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Slide 33
Plasma cell in EM -- showing nucleolus and "cartwheel" chromatin configuration in the nucleus. The
cytoplasm is packed with rough endoplasmic reticulum, indicating protein formation. Plasma cells produce antibodies (immunoglobulins).
Slide 34
Eosinophils (bright pink granules) -- in areolar connective tissue. Note the bilobed nucleus in the center
cell. Pale oval nuclei in the upper left hand corner
probably belong to fibroblasts. Small, dark, round
nuclei, such as in the lower right quadrant, probably
belong to lymphocytes. Macrophages are hard to
identify unless their cytoplasm is filled with phagocytized particles.
Slide 35
Wandering tissue eosinophils (bright pink cytoplasmic granules) and neutrophils (with lobed nuclei) -in areolar connective tissue.
Slide 36
Miscellaneous cells in areolar connective tissue. The
central cluster with beady, dark nuclei are wandering
neutrophils. Any small, round, dark nucleus with no
visible surrounding cytoplasm is a lymphocyte. The
large, pale, oval nuclei scattered around the field belong to fibroblasts. In the lower right corner are two
fairly oval plasma cells with definite cytoplasm and
dark, round, eccentric nuclei. Macrophages are probably in the area but are hard to identify without ingested particles to mark them; the most likely candidate here is a fairly large cell just left of the central
cluster with definite cytoplasm and a small oval nucleus. The rounded space in upper right corner of the
field is a blood vessel with endothelial cells lining it;
inside the lumen is a neutrophil, showing a dark bilobed nucleus.
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Part 5: Blood and Capillaries
Slide 51
Normal cells of blood as seen in a blood smear. This
slide shows many red blood cells and one neutrophil
(or polymorphonuclear leukocyte). Neutrophils characteristically have a multi-lobed nucleus and very
fine, neutral-stained cytoplasmic granules. These
cells migrate out into the connective tissue and become phagocytic and provide a first line of defense
in acute infections.
Slide 52
Eosinophil -- with quite large, regular, refractile, eosinophilic (pink) cytoplasmic granules, and a bilobed
nucleus. Eosinophils congregate in connective tissue
in allergic reactions.
Slide 53
Basophil -- with very dark, coarse, basophilic (purple-blue) granules in the cytoplasm surrounding the
lobed nucleus. The granules contain principally histamine and heparin. Basophils are activated in response to immunologically mediated hypersensitivity reactions.
Slide 54
Small lymphocyte - only a little larger than a red
blood cell, it has only a thin rim of pale cytoplasm
around a darkly stained round nucleus. Its function is
related to the body's immunological defenses. Scattered among the r.b.c.'s are some very small clumps
of platelets, which are necessary for the clotting of
blood.
Slide 55
A large lymphocyte circulating in the blood. The
nucleus is characteristically round and dark, but
there is more cytoplasm than in the typical "small"
blood lymphocyte.
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Slide 56
Monocyte - the largest of the leukocytes, it has quite
a bit of bluish cytoplasm, surrounding a typically
kidney-bean-shaped nucleus. When out in connective tissue, this cell becomes a macrophage (histiocyte).
Slide 57
EM of neutrophil, showing its multi-lobed nucleus.
The many electron dense lysosomes in the cytoplasm are characteristic of a phagocytic cell.
Slide 58
EM of eosinophil cutting through bilobed nucleus.
Notice the typical "cat's-eye" appearance of the cytoplasmic granules with the dark crystalloid band in
the middle of each one. (Such bands do not appear in
human eosinophils.) These granules, banded or not,
contain hydrolytic enzymes and are lysosomal in nature.
Slide 59
EM of basophil showing dense granules reminiscent
of those of mast cells. At one time it was thought
that the basophil of the blood became the mast cell
of connective tissue, but most work now indicates
that these are two different cell lines ... though their
granules contain basically the same secretory substances.
Slide 60
EM of monocyte with many lysosomes in an activelooking cytoplasm. Again, the lysosomes indicate
potential for phagocytic activity.
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Slide 61
EM of lymphocyte -- rather a nondescript looking
cell considering its great functional importance. Notice the cytoplasmic process to the right and relate it
to the appearance of lymphocytes in the next two
pictures.
Slide 62
Scanning electron micrograph of lymphocyte with
many cytoplasmic extensions.
Slide 63
Scanning electron micrograph of lymphocyte with
relatively smooth surface. Differences in cell surface
presumably represent differences in cell activity at
the moment. At one time such visible differences
were thought to provide a distinction between B
cells and T cells, but recent work does not substantiate this.
Slide 64
Scanning EM of red blood cells. Normal ones have
the typical biconcave disc shape. The "spinylooking" ones are crenated because of loss of cytoplasmic fluid to a hypertonic environment.
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Slide 65
Red blood cells lined up in rouleaux (stacks). This
vessel is in bone. Such clumping of cells suggests
rather stagnant flow, as was probably the case in this
postmortem tissue.
Slide 66
Longitudinally cut capillaries running in the connective tissue between cardiac muscle cells. Note the
very thin endothelial lining of the vessels. Notice too
that the capillary diameter is essentially that of the
red blood cell. Several r.b.c.'s can be seen in transit
here. Their shape is plastic, responding to surrounding pressures, but cells are traveling independently.
Compare their appearance with the stacked cells on
the previous slide.
Slide 67
Capillaries in the connective tissue supporting cardiac muscle cells, this time cut in cross-section.
Good examples lie in the upper left and lower left of
the field. Look for a small thin-walled circle with a
dark, crescent-shaped endothelial nucleus on one
side. The rest of the thin circle of wall is composed
of endothelial cytoplasm.
Slide 68
Small blood vessels of various sizes in areolar connective tissue. The two cross-cut capillaries at center
contain erythrocytes and show an endothelial nucleus at the rim. The largest vessel, at extreme center
right, is a venule. All of the vessels shown here are
thin-walled and capable of fluid and ion exchange
with the surrounding connective tissue fluid. In addition, leukocytes can squeeze between endothelial
cells of the walls of such vessels (by diapedesis) and
enter the connective tissue. Only when they leave the
bloodstream do they assume their active roles.
38
Slide 69
EM of cross-cut capillary lying between skeletal
muscle cells. Note a peripheral muscle nucleus at the
top of the micrograph. A thin basal lamina surrounds
the endothelium as well as the muscle cells.
CL=capillary lumen; CJ=cell junction; G=glycogen
particles; M=mitochondria; N=nucleus of endothelial cell; PV=pinocytotic vesicles.
Slide 70
Two EM views of fenestrated endothelium. In the
section at left, through the cytoplasm of an endothelial cell, fenestrations are represented whenever
the inner and outer cell surfaces meet in a thin line.
In the picture at right a tangential cut through the
surface of an endothelial cell shows multiple round
fenestrations.
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Part 6: Neural Tissue
Slide 1
Although details of the structural organization of
the brain and spinal cord will come in the Neuroscience course, it is important from the beginning to
place primary sensory and motor neurons in their
proper relation to the spinal cord. This slide is an
overview of one half of a transverse section of the
spinal cord, along with its ventral and dorsal roots
and a spinal ganglion. At the extreme left (which is
close to the midline of the cord) notice a small central canal lined by a dark layer of ependymal this
contains cerebrospinal fluid in life. Above the canal
lies the narrow slit of the posterior median sulcus,
and below the canal is a wider, bulging separation
called the anterior median fissure. Lateral to all
these spaces lies the gray matter of the cord (quite
pink here), where neuronal cell bodies lie. Surrounding the gray matter is a layer of white matter,
consisting of nerve cell processes, all of them
axons, running up or down the length of the cord
and therefore cut in cross-section here. Outside the
cord, to the right, lies a mass of nerve cell bodies,
the spinal ganglion, interrupting the course of the
dorsal root. Below the ganglion lies the ventral
root. Surrounding the entire complex is a welldefined, pink band of dura mater which consists of
dense collagenous connective tissue. The wedge of
delicate areolar c.t. at the bottom of the anterior
median fissure is the arachnoid; note the round
cross-cut of a blood vessel lying in it. The pia mater, invisible here, is an extremely thin connective
tissue layer immediately investing the spinal cord.
In terms of a simple reflex arc (sensory information comes to the cord and motor information
is sent from the cord) picture some basic nerve cell bodies and processes as follows:
A pseudounipolar, sensory cell body lies within the spinal ganglion. It has one long dendrite
coming in from the extreme right in this picture, from the body periphery (either from muscle
or skin). This dendrite is continuous with the cell body (no synapses are involved here). The
cell's axon leaves along the same "stalk" with the dendrite and then turns to course through
the dorsal root, into the spinal cord. There its axonal endings synapse upon the dendrites of a
small, intermediate multipolar neuron lying in the dorsal horn of the gray matter. This intermediary cell sends its axon to the ventral horn of the, gray matter and synapses upon the dendrites of a large, multipolar, motor neuron lying there. The axon of the motor neuron courses
out of the cord via the ventral root and proceeds out of this picture, to the right, until it ends
Upon voluntary muscle.
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Slide 2
A group of large multipolar neurons, as found in
the gray matter of the anterior horn. Cell nuclei are
pale (or vesicular) and round and contain a large
amount of Nissl substance (RER). The smallest
nuclei in the field belong to glial cells. In an area
like this, glia play a supportive and nutritive role.
They take the place of connective tissue within the
central nervous system (i.e., the brain and spinal
cord).
Slide 3
Higher power of multipolar neuron in gray matter
stained with silver. Notice the meshwork of
processes comprising the neuropil around the cell
Processes may be dendrites of local neurons, or
axons of distant neurons either passing through the
field or ending upon local neurons.
Slide 4
A large, multipolar, motor neuron of the anterior
horn, seen whole, with all its processes stretched
out in a spinal cord smear. Notice the dark clumps
of Nissl substance in the cytoplasm. The axon cannot be identified with certainty in this particular
view. Neuroglial nuclei surround the neuron. Of
these small nuclei, the lightest ones, showing small
clumps of chromatin, belong to astrocytes; any
dark, round ones (such as the one in the upper right
corner) belong to oligodendroglia; and any dark,
thin, cigar-shaped ones to microglia (see possible
one just to right of the neuron).
Slide 5
Glial nuclei seen in white matter of the cord, cut so
that nerve processes are seen running longitudinally. Most of these are round, dark oligodendroglial
nuclei; these are the cells responsible for the myelin
wrapping of axons of the central nervous system.
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Slide 6
Silvered preparation of astrocytes, showing their
many fine cytoplasmic processes. Note their close
relationship to capillaries, the heavy black structures. Since astrocytes touch both capillaries and
neurons, they are thought to play an important intermediary role in the nutrition and metabolism of
neurons.
Slide 7
Spinal ganglion in Mallory connective tissue stain.
The pseudounipolar cells are in characteristic
groups or clumps, separated by bands of nerve
processes. The processes might be either dendrites
arriving from the body periphery or axons proceeding on to the spinal cord. Either way, the cell bodies
or origin for the processes lie within the spinal ganglion and are sensory neurons. The dark blue sheath
outside the ganglion is the dense collagenous connective tissue dura mater.
Slide 8
Detail of pseudounipolar spinal ganglion each one
encapsulated by a layer of small satellite cells.
Bright blue material is the supportive connective
tissue, which is directly continuous with the endoneurium surrounding the individual nerve processes
entering and leaving the ganglion. Remember that
connective tissue is the supportive tissue of the peripheral nervous system.
Slide 9
Higher power of spinal ganglion stained with H&E.
Satellite cell capsules are clear. The large neuron in
the center of the field has a pale axon hillock where
the seemingly single process enters and leaves. In
such a pseudounipolar cell, the incoming dendrite
and outgoing axon seem to be related to the cell
body by means of a single "stalk". The paleness of
the hillock is due to the absence of RER (Nissl substance) in this area.
Slide 10
Cells of autonomic (sympathetic) ganglion, at same
magnification as previous slide. These motor neurons are actually multipolar in shape and are generally smaller than spinal ganglion neurons; they are
also scattered more randomly and individually in
their ganglion, and have less well defined capsules
of satellite cells. Some of the cells in this picture
contain yellow lipofuscin granules, a sign of age.
(Lipofuscin is sometimes spelled lipofuchsin; these
42
granules represent the undigested residual material
of lysosomal activity.) Autonomic ganglion neurons are the second order neurons in the two cell
autonomic chain; the first order neurons lie in the
central nervous system and send out axons to synapse upon the dendrites of the ganglion neurons.
Slide 11
Autonomic parasympathetic neurons lying between
muscle layers in the intestinal wall. Note their large
size in comparison with surrounding satellite cells.
The neuronal nuclei here are often eccentric. Remember that although autonomic neurons look generally rounded in outline, they are actually multipolar neurons with very fine dendritic processes, and
they are visceral motor neurons, responsible for involuntary control of smooth and cardiac muscle.
Slide 12
Cross-cut of a peripheral nerve showing characteristically round bundles of nerve processes surrounded by pale gray-blue connective tissue
sheaths. The outer connective tissue sheath surrounding the entire nerve is the epineurium. The
connective tissue sheath surrounding each round
bundle is the perineurium. Surrounding each individual nerve process within a bundle is the delicate
connective tissue endoneurium (not visible at this
magnification).
Slide 12A
43
Scanning electron micrograph of a cross-section of
a peripheral nerve showing individual axons surrounded by myelin sheaths. The axons have undergone some shrinkage with specimen preparation
and have receded from the surface of the section.
Myelinated axons are visible beneath the translucent perineurium.
Slide 13
A higher magnification of one bundle of peripheral
nerve, showing cross-cuts of individual processes.
The ones in the center are the truest cut; those on
either side are tangentially cut. The best ones show
a darker axon in the center of the fiber, surrounded
by a paler myelin sheath. Remember that some of
these fibers are axons of motor neurons, whose cell
bodies are in the anterior horn of the spinal cord,
while other fibers are dendrites of the pseudounipolar sensory cells of the spinal ganglion. This is the
one instance where functional dendrites (i.e.,
processes coming into the cell body) are structurallv like axons with myelin sheaths. The dense
sheath at the outer edge of the bundle here is perineurium. The lines of pink surrounding each
process represent endoneurium.
Slide 14
Low power view of longitudinal section of peripheral nerve, again showing distinct division into
bundles of processes. The "'waviness" of the
processes themselves is often typical of nerve.
Slide 15
Higher magnification of longitudinally cut nerve,
showing a clear node of Ranvier in the center of the
field. Note that the axon is continuous through the
node. Notice also the "foamy", grainy appearance
of the myelin sheaths; this represents the proteinaceous material of the cell membrane wrappings of
the sheath, often called "neurokeratin" although this
is a misnomer. The lipid portion of the membranes
has been dissolved out during tissue fixation.
44
Slide 16
Detail of node of Ranvier, with axon continuing
through it. Axons stain deep pink. Myelin is pale
because the lipid material disolves out. The dark
strands of protein neurokeratin give the "foamy"
look to the myelin in light microscopy. Nuclei, seen
here near the bottom of the picture, lie between
nerve processes and belong to either Schwann cells
or endoneurial connective tissue cells (such as fibroblasts).
Slide 17
Drawing of relation of an oligodendrocyte to a neuronal axon in the CNS, as seen in E.M. An extension of cell cytoplasm wraps around the axon, making a multi-layered myelin sheath. Ordinarily there
is one oligodendrocyte between two successive
nodes of Ranvier. Notice that the cell has other cytoplasmic extensions up above, which are free to as
sociate with other axons. This same principle of
lamellated (layered) myelin sheath formation holds
true also for Schwann cells and peripheral nerves.
One difference, however, is that a Schwann cell is
believed to wrap only one axon instead of several.
Notice that the plasma membrane of the axon is
bare at the point of the node; this allows for rapid
saltatory conduction as the impulse jumps from
node to node to node.
Slide 18
EM of myelinated axons of peripheral nerve. The
dark, many-layered myelin sheaths surround pale
axons. At the upper edge of the picture is a nucleus
of a Schwann cell, with its outer rim of cytoplasm
continuous with the outer rim of the myelin sheath
of the axon in the left corner. (Remember that nonmyelinated axons are also closely related to
Schwann cells, but the Schwann cells form no
layered wrappings around them. Note, too, that one
Schwann cell can be related to several axons when
these are non-myelinated.)
Slide 19
Cross-cuts of small peripheral nerve bundles as
seen in ordinary tissue sections. The processes have
a typically wavy appearance.
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Slide 20
Detail of a motor nerve ending upon a skeletal
muscle cell (voluntary muscle). The axon terminal
is highly branched to form an oval motor end plate.
The cell body which sends out this axon is a multipolar motor neuron, such as those in the anterior
horn of the spinal cord.
Slide 21
Diagram of motor end plate (myoneural junction)
as seen with electron microscopy. This drawing
shows a detail of one knob of an end plate as it rests
in a trough on the surface of a muscle cell. The
"subneural clefts" labelled here are also called "gutters" in the sarcolemmal membrane. The label "glycoprotein" indicates the position of the basal lamina
of the muscle cell.
Slide 22
EM detail of neuro-neural synapse in the brain or
spinal cord. The axon terminal contains many seedlike synpatic vesicles containing transmitter substances. The intercellular cleft between the axon
and the contacted dendrite can be seen. Just below
the dendritic cell membrane is a dark, filamentous
post-synaptic density. Other profiles in this field,
most of them very irregular in outline, belong to
both neuronal processes and glial processes. There
is one large and one small mitochondrion just left
of the synaptic vesicles.
Slide 23
Muscle spindle -- a specialized sensory receptor for
muscle stretch and position sense, as related particularly to unconscious maintenance of skeletal muscle tone and proper balance of postural muscle activity. The spindle is the encapsulated group of
muscle fibers lying in the center of the field of regular skeletal muscle fibers, all cut in cross-section.
The sensory nerve endings themselves (not visible
here) wrap around the muscle fibers within the
spindle. Such endings relay sensory information
along dendrites within peripheral nerves, back to
pseudounipolar cell bodies in a spinal ganglion, and
thence to the spinal cord.
46
Slide 24
Pacinian corpuscle -- another specialized sensory
ending, this time for deep pressure. This particular
view is from a whole mount of mesentery, so you
are seeing the corpuscle three-dimensionally. They
are also found in subcutaneous tissue, deep to skin.
Notice the onion-like layers of specialized connective tissue surrounding a dark pink dendritic terminal. Again, the cell body for this dendrite lies in
a spinal ganglion, and the axon of that same cell
then proceeds into the spinal cord.
Slide 25
The following five slides show some specializations of the brain. First is an overview mid-sagittal
cut of the brain, showing the many folds (or gyri)
of the external cerebral cortex, and the much smaller, more delicate folds (or folia) of the cerebellar
cortex seen to the left. As seen in this kind of cut,
the cerebellar folia have a branching, tree-like appearance. (The brain stem is the solid-looking
structure along the base of the brain, and continuous with the spinal cord at lower left.)
Slide 26
Section of cerebral cortex, showing cuts of two gyri. The pale cortex follows along the contours of the
gyri. White matter (composed of nerve processes)
lies below and stains a darker pink. Very little
cytoarchitecture is seen with H&E stain.
Slide 27
Cerebral cortex stained with silver to show silhouettes of pyramidal cells. Now each triangular
cell body can be seen, as well as the ascending
apical dendrite, several basal dendrites, and a very
fine descending axon. These are specialized multipolar neurons with such a definite shape that they
can be recognized as such. You will learn more
about them in Neuroscience.
47
Slide 28
Section of cerebellar cortex, showing several folia.
Each folium has a central core of bright blue white
matter, consisting of nerve processes entering and
leaving the superficial cortex. The cortex has an
external pale layer and a darker staining granular
layer beneath it. Large Purkinje cells lie in a row
between these two layers but are not visible at this
magnification.
Slide 29
Higher magnification of cerebellar cortex, showing
the row of large Purkinje cells lying between the
outer and inner cortical layers. The stubs of the
dendritic trees of the Purkinje cells look rather like
"antlers" arising from the cell bodies. Very complex dendritic branchings actually extend throughout the molecular layer above the Purkinje c ells. A
single axon leaves each Purkinje cell at its base and
descends through the granular layer to deeper relay
stations within the brain. Again, these are neurons
with a very distinctive shape; you'll study their
function and their connections next semester.
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Part 7: Muscle
The cells of muscular tissue lie parallel to each other and, therefore, can be cut in either
cross or longitudinal section and have to be distinguished from each other in both
planes. They must also be distinguished from cuts of nerve and tendon. Watch for diagnostic features as you go along through these slides.
Longitudinal sections:
Slide 41
Smooth muscle - long, slender central nuclei, lying
within narrow, fusiform cells that lie parallel to each
other in a smooth arrangement. (Muscle cells are often referred to as muscle fibers because of their narrowness and length.)
Slide 42
Smooth muscle - with cells more separated so as to
see their extent and shape better, and the central position of their nuclei. A loose, irregular connective
tissue (endomysium) lies between the cells. Nuclei
seen in this c.t. belong to fibroblasts mainly.
Slide 43
Smooth muscle with wrinkled nuclei due to contraction of cells.
Slide 44
EM of smooth muscle showing typical "hairy" look
of primarily filaments in the cytoplasm. Part of the
cytoplasm is clear of filaments and shows mitochondria and polyribosomes. The cell membrane is at the
lower right of the field and shows a few pinocytotic
vesicles toward the extreme right. The left-hand extent of that same membrane seems darker and denser: probably a plaque, where filaments attach. The
fuzzy density just outside the cell membrane is the
basal lamina.
49
Slide 45
Skeletal muscle cells (fibers), with cross-striations
and peripheral nuclei.
Slide 46
Higher power of skeletal muscle for details of crossstriations. Notice thin Z discs and heavy A bands.
From one Z disc to the next is a sarcomere, the unit
of muscle contraction. In the upper muscle cell notice shadowy myofibrils running longitudinally.
Slide 47
EM of several myofibrils running longitudinally
through skeletal muscle cell. Between individual
myofibrils lie the mitochondria (M) and glycogen
(G) of the cytoplasm. Within each myofibril are the
typical striations: A= A band; I= I band; Z= Z line;
and H= H band. The banding is formed by the arrangement of myosin and actin filaments.
Slide 48
Cardiac muscle with cross-striations, dark intercalated discs, and centrally located nuclei. Notice too
that the nuclei are stubby in appearance, and that
they lie in a rather granular cytoplasm. Some of the
intercalated discs form a straight line across muscle
fibers; others make a step-like arrangement.
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Slide 49
EM of intercalated disc between the ends of two cardiac muscle cells. Both desmosomes (1) and fasciae
adheretes (2) are identified. Notice mitochondria and
glycogen particles lying between myofibrils.
Slide 50
Another view of cardiac muscle showing wavy connective tissue (endomysium) between muscle cells.
Also, notice capillaries with r.b.c.'s; muscle is a
highly vascularized tissue. Some yellow granular
cytoplasm can be seen inside the lower muscle cells,
where myofibrils are parted. This picture also gives
some indication of the branching of cardiac fibers.
Slide 51
This is a longitudinal section of peripheral nerve, for
comparison with the three types of muscle. The foamy, pale look is due to the dissolving out of lipids
from the myelin sheath. Note also the rounded constrictions of nodes of Ranvier.
Slide 52
Another comparison, this time with tendon (dense,
regular, collagenous c.t.). Here you see very thin fibroblast nuclei compressed between collagen fibers
and lined up in rows ("box-car").
51
Slide 53
Dense, fairly regular, collagenous tissue with mostly
fibers and very few cells. Not as neatly arranged as
the previous tissues.
Cross-sections:
Slide 54
Smooth muscle. Since the muscle cells are spindleshaped, with tapered ends, the diameters of crosscuts of individual cells vary considerably. Nuclei are
central but appear only when the section goes
through the widest part of the cell. Compare diameters of these cells with those in the next two slides,
which are at the same magnification.
Slide 55
Cardiac muscle, with central nuclei surrounded by
proportionally greater amounts of cytoplasm than
previous smooth muscle. The "graininess" of the cytoplasm is due to cut ends of myofibrils. Remember
that a very fine connective tissue endomysium lies
between the individual muscle cells in all three types
of muscle; often it is not well preserved because it
collapses during fixation.
Slide 56
Skeletal muscle -- large, rounded cross-cuts of muscle cells, packed so full of myofibrils that nuclei are
displaced to the periphery. (There is a capillary filled
with pink rbc's in the upper middle field.)
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Slide 57
A cross-cut of nerve for comparison. The pale central axons are surrounded by myelin sheaths that
seem to have radiating lines in them due to the way
the protein component of the sheath is preserved. All
nuclei lie between nerve processes rather than in
them.
Slide 58
A cross-cut of tendon to show fibroblasts compressed between thick pale collagenous fibers that
they look stellate in shape. The cells look as if they
are lying in "cracks" between the fibers; notice this
on the right side of field particularly.
Further details of muscle:
Slide 59
The inner surface of the heart showing large, palestaining Purkinje fibers lying across the mid-portion
of the picture. They are modified cardiac muscle fibers and seem mostly free of myofibrils except at the
cell periphery, so that each cross-cut seems to have a
darker pink rim and a pale center. The normal cardiac muscle fibers lie below in this micrograph and
appear much smaller and more darkly stained than
the Purkinje fibers.
Slide 60
Cross-cut of skeletal muscle to show connective tissue partitioning of muscle into groups or bundles of
fibers. Endomysium is very delicate and lies between individual fibers, while perimysium is more
visible and lies around a group of fibers. Epimysium
is not seen here but ensheaths a whole muscle. In
this picture notice the presence of small blood vessels in both perimysium and endomysium. Notice
also the cross-cuts of myofibrils within the muscle
cells, making them look grainy.
53
Slide 61
Longitudinal view of skeletal muscle cell with unusually clear cross-striations. This muscle is
stretched, so that the A band is widely split.
•
a)Z disc
•
•
•
•
b)A band, split -- with pale H band in the
middle
c)the line lies right in an H band
•
d)width of I band, with Z disc in the middle
•
•
e)pointing to a practically invisible thin line,
the sarcolemma (or cell membrane), which
lies outside the pale peripheral nucleus seen
to the right.
•
•
Slide 62
Diagram of contraction of skeletal muscle. On the
left is the view with light microscopy. On the right
are the thin actin filaments and thick myosin filaments seen in EM. Notice that the total width of the
A band stays the same throughout and that the sliding in or out of the actin filaments determines the
width of the H band. Consider which filaments you
would see if you cut the muscle cross-wise through
the I band, A band, or H band.
Slide 63
EM of cross-cut cardiac muscle showing thick myosin and thin actin filaments in a highly geometric
arrangement.
54
Slide 64
Drawing of relationship (at EM level) of myofibrils
to sarcoplasmic reticulum (smooth ER) and Ttubules in skeletal muscle. In this drawing the sarcoplasmic reticulum is labelled "sarcotubules" and
"terminal cisternae". Notice that T-tubules are extensions of the sarcolemma (cell membrane, seen at
right-hand edge), so that depolarization can spread
along this part of the sarcolemma as well. (See diagrams and further explanation in your textbook.)
Slide 65
Same kind of diagram, this time for cardiac muscle.
Note differences between the two in:
1. their amount and arrangement of sarcoplasmic reticulum
3. the presence or near-absence of terminal cisterns (next to the T-tubules)
5. the position of T-tubules in relation to the A,
I, and Z bands seen at the left.
A triad consists of two terminal cisterns with a Ttubule in the middle. When the cisterns are not well
developed, a true triad does not exist. A diad means
two elements are together, as with one T-tubule and
a neighboring bit of sarcoplasmic reticulum. NOTE:
sarcoplasmic reticulum is just a form of smooth endoplasmic reticulum (SER). In muscle it is particularly associated with the release of calcium ions
needed for contraction.
2.
4.
6.
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Part 9: Specialized Connective Tissue: Cartilage and Bone
Slide 31
Hyaline cartilage (lavender matrix), with perichondrium (pink) outside it. The latter is a dense regular
collagenous c.t.. There are collagenous and elastic
fibers lying in the cartilage matrix but they are invisible because their refractive index is the same as that
of the matrix. Cartilage cells = chondrocytes, and
they are lying in the lacunae.
Slide 32
Two chondrocytes completely filling their lacunae.
If the cells were to drop out, you would see spaces in
the matrix. The matrix appears very smooth, clear,
and glassy (or "hyaline").
Slide 33
Electron micrograph of a chondrocyte in its lacuna
and almost entirely filling the lacunar space. Notice
that the cell has many fine cytoplasmic projections
when viewed by electron microscopy. There are surrounded by heavily condensed ground substance
which appears less dense on the other side of the
cell.
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Slide 34
Appositional growth of cartilage by conversion of
long, thin perichondrial cells (at the right) into the
round, large chondrocytes. Notice how they change
shape as they lay matrix down around themselves.
The cells of the outer perichondrium are fibroblasts;
the inner perichondrial cells include some primitive
connective tissue cells which differentiate into chondroblasts and then into chondrocytes as they lay
down matrix and become embedded in it.
Slide 35
Hyaline cartilage with quite basophilic matrix immediately surrounding the lacunae. Cells are often
grouped in "nests" (or isogenous groups) as a result
of earlier mitoses and nowhere for cells to move
apart. (This is called interstitial growth). (The "ripple
lines" in the matrix here are due to uneven cutting of
the section.)
Slide 36
Elastic cartilage, with chondrocytes and matrix as
before, but elastic fibers predominate and take a specific stain. They always look very distinct and dark
and show many branchings.
Slide 37
More elastic cartilage. The matrix immediately surrounding each cell is typically not traversed by fibers.
Slide 38
Fibrocartilage, with wispy, broad collagenic fibers
predominating in the matrix. They look "cotton-y",
unlike the sharply defined elastic fibers seen before.
Notice that the cells are lying in lacunae.
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Slide 39
Fibrocartilage, at the point of junction between hyaline cartilage (lavender) above and dense collagenous tissue (pink) below. The combination of chondrocytes, matrix, and visible wispy collagenic
strands or fibers identifies this as fibrocartilage.
Slide 40
Section of compact ground bone - dry and unstained
- showing cross-cuts of Haversian systems. In the
center of each system is an Haversian canal which
carries blood vessels. With so many such systems
per unit volume of bone, we can say that bone is a
well vascularized tissue. (By contrast, cartilage is
avascular.)
Slide 41
Higher power of ground compact bone. You can see
on the left that a central vascular channel (Haversian
canal) is surrounded by concentric lamellae (layers)
of bone. These lamellae are made up of collagenous
fibers and inorganic salt matrix. The lamellae in the
center of the picture are interstitial lamellae, left over
from earlier Haversian systems that have been partially resorbed as new systems were laid down during the constant remodelling of the bone as it
formed. Black spaces air-filled lacunae in which osteocytes once lived.
Slide 42
Detail of Haversian system, showing the tiny, spidery canaliculi extending from one lacuna to the
next. In life these canaliculi held the processes of
osteocytes thus permitting diffusion of nutrients
from the central blood vessels to the outer lamellae
of the Haversian system.
Slide 43
Detail of lacuna, showing radiating canaliculi. Tissue fluid from the capillaries and connective tissue
of the Haversian canal can seep through these spaces
and channels, bringing nutrients to the stellate osteocytes residing there.
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Slide 44
EM of osteocyte in lacuna. The cytoplasm of the cell
contains rough endoplasmic reticulum for the production of protein collagen, some of which can be
seen lying immediately around the cell. The collagen
becomes masked by black apatite (CaPO4) crystals
as the matrix becomes mineralized.
Slide 45
High power EM of contact between two neighboring
osteocytes whose processes have met in a canaliculus. Close examination of the contact shows fused
outer leaflets of cell membrane (note three dark
lines), indicating that this is a tight junction. Osteocytes are also known to make contact by means of
gap junctions.
Slide 46
Low power view of a cross-cut shaft of decalcified
long bone. The bone itself is pink and lies in the center of the field. The pinkness is due to the staining of
collagen fibers in the lamellae. To the left is bone
marrow; to the right is attaching skeletal muscle.
Slide 47
Early compact bone, decalcified so it can be stained.
This has been cut so that the Haversian systems are
cut in cross section. Vascular channels cut longitudinally are parts of Volkmann's canals.
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Slide 48
Vascular elements from bone marrow (on the left)
are continuous with vascular spaces within the bone.
The endosteum lining the marrow cavity is therefore
continuous with the endosteal linning of Haversian
canals.
Slide 49
Detail of bone-forming osteoblasts lined up along
the inner (endosteal) edge of bone next to the marrow cavity. In young bones growth continues in
width, constantly laying down bone and resorbing it
and laying down more. Real width, of course, increases by the laying down of periosteal bone on the
outside of the bone, but activity continues on the endosteal surface also. Notice osteocytes inside the
bony substance, lying in lacunae.
Slide 50
Detail of osteocytes in lacunae. The collagenous fibers of the decalcified matrix are quite acidophilic,
as always. Osteocytes like these are present in both
compact and spongy bone; their arrangement, however, is in concentric lamellae in compact bone and
in randomly arranged lamellae in spongy bone. Remember, too, that osteocytes have processes which
extend out into canaliculi in both kinds of bone.
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Part 10: Endochondral Ossification
Slide 61
All of the long bones and many others of the body,
are preformed embryologically in hyaline cartilage
and then replaced by bone by endochondral ossification. Such a change has begun in the middle of
the shaft of this bone, thanks to the invasion of
blood vessels and their accompanying primitive
connective tissue. Pale pink cartilage is seen in the
head of the bone. A dark pink periosteal bone collar has already formed around the middle of the
shaft, and ossification is proceeding toward both
ends of the cartilage model. The dark pink strands
lying outside the whole bone are dense collagenous tissue of periosteum (around the bony part)
and perichondrium (around the cartilaginous part).
H & E stain.
Slide 62
Endochondral ossification in greater detail. The
cartilage cells (chondrocytes) near the region of
active ossification have enlarged (hypertrophied)
and lined up more or less in columns. The purplish
material in the center of the shaft is primitive bone
marrow, with reticular cells and developing blood
cells. The vascular elements of the marrow tissue
actively invade the cartilage above, leaving spicules of calcified cartilage, upon which bony matrix will be deposited. The dark pink spicules here
are made of bone; the paler pink, small spicules at
the leading edge of the cartilage are made of calcified cartilage.
Slide 63
Endochondral ossification in Mallory stain. Cartilage is light blue and bone is dark blue. A thin
layer of bone has already been laid down on the
surface of the cartilage spicules along the leading
edge of cartilage. Blood cells in the marrow cavity
are red. The very dark blue at the lower left and
right is spongy bone of the periosteal bone collar
of the shaft. This will later be remodeled into Haversian systems of compact bone.
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Slide 64
Head of fetal bone still made of hyaline cartilage.
Near the point where ossification is going on (upper right corner) the cartilage cells become larger
and the cartilage matrix becomes calcified (purple
instead of pale pink here, as stained in H & E). A
small amount of dark pink bone has been laid
down on the surface of the calcified cartilage. Later on, a secondary center of ossification will form
in the head of the bone, and the cartilage that remains between the two centers of ossification will
be the epiphyseal plate for growth of the bone in
length.
Slide 65
Region of ossification at higher magnification -same stain as previous slide. Chondrocytes are
hypertrophied, degenerating, and lined up in columns at the right. As the marrow tissue invades the
cell columns, spicules of cartilage will be left. The
cartilage matrix is calcified (purple), and one small
area of bone deposition, has begun on it (the red
color at the upper right). The small cells caught in
the red matrix are osteocytes.
Slide 66
Another detail of ossification. Calcified cartilage
spicules are purple-blue; bone deposits are purplered. Gradually the cartilaginous portions will be
resorbed as the bone is constantly reshaped, until
finally there will be no trace of cartilage left. The
main purpose of the cartilage in the first place was
to provide a framework upon which bone deposition could begin.
Slide 67
Spicules showing early endochondral ossification.
In H & E stain, the centers of the spicules show the
purple of calcified cartilage; the edges are pink because of the bony matrix laid down upon the cartilage.
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Slide 68
Spicules of spongy bone (bright red) surrounded
by a whole line-up of osteoblasts. The osteoblasts
that have previously been trapped in their own salt
deposits now lie in lacunae within the spicule and
are called osteocytes. The cells of the primitive
bone marrow lie between bone spicules.
Slide 69
Detail of bony spicule with typically acidophilic
(pink in H & E) matrix. Osteoblasts are lined up
along its borders, depositing another layer of matrix. Osteocytes lie within lacunae in the spicule.
Slide 70
EM of active osteoblast laying down the fibers and
salts of bone. The cytoplasm of the cell is to the
left and contains lots of rough endoplasmic reticulum and many mitochondria. In the lower right
corner is mineralized bony matrix containing the
typical black CaPO4 (apatite) crystals. Between
this matrix and the osteoblast lies a pale area of
newly secreted pre-bone (or osteoid) which contains collagen fibrils (note their cross-striations)
lying in an as yet unmineralized ground substance.
Slide 71
Spicules of spongy bone stained with Mallory
stain. Bone stains blue. Note line of osteoblasts
along left hand edge.
Slide 72
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Slide 73
Enlarged area of spongy bone, so called because
there are large, irregular spaces of bone marrow
intermixed with the bony substance.
Slide 74
The large central space is a resorption area where
young compact bone is being actively remodeled.
This is an area where osteoclasts are resorbing the
bony substance; notice to large multinucleated osteoclasts toward the left of the cavity next to the
intact Haversian system that lies in the upper left
corner of the field. Later, osteoblasts will differentiate from the primitive reticular tissue in the resorption cavity and will begin to lay down new
bony lamellae around the edge of the cavity. As
successive lamellae are laid down, the cavity will
gradually grow smaller, until eventually a new Haversian system with a narrow central canal will be
formed.
Slide 75
Detail of an osteoclast, a giant, multinucleated cell
associated with bone resorption. The shallow bay
in which it lies is a Howship's lacuna. The osteoclast is now considered to develop from a separate
stem cell in the bone marrow.
Slide 76
EM of an osteoclast, with its ruffled border next to
the area where bony matrix is being resorbed. The
net effect of a ruffled border is to increase the cell
surface area for contact with the collagen fibrils
and apatite crystals being resorbed.
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Slide 77
Haversian systems of decalcified compact bone,
mostly cut in cross section here. The one channel
cut longitudinally is a Volkmann's canal; these
channels run perpendicular to both the long axis of
the bone and the central canals of the Haversian
systems.
Slide 78
Decalcified bone with Haversian system cut longitudinally. Notice the central blood vessel and the
many concentric bony lamellae around it. As always, osteocytes are trapped in their lacunae.
Slide 79
End of a young long bone, with the pale epiphyseal plate lying between the primary ossification
center of the shaft and the secondary ossification
center of the head. The plate and the pale area continuous with it, up over the head, are composed of
hyaline cartilage. Active ossification is going on
along the lower edge of the epiphyseal plate, allowing growth in length of the bone. There is also
active ossification along the lower edge of the cartilage that surrounds the head, thus allowing for
growth in size of the head of the bone. Bony spicules are seen throughout the centers of ossification, making areas of spongy bone with red marrow between the spicules.
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Slide 80
Diagram of a cross-cut chunk of wall of the shaft
of a long bone. Most of the substance is compact
bone, with Haversian systems cut cross-wise on
the uppermost surface and longitudinally on the
right-side surface. Volkmann's canals carry blood
vessels from the inner and outer bone surfaces to
the vessels of the Haversian canals. The lamellae
of the Haversian systems are pulled out here so
that you can see the lamellar rings. External (or
periosteal) circumferential lamellae are seen surrounding the whole bone. Internal (or endosteal)
lamellae line the inner surface next to the marrow
cavity (to the left). Notice that the inner, endosteal
wall bears many spicules of spongy (cancellous,
trabecular) bone. The dense collagenous connective tissue coat (the periosteum) looks dark here
and surrounds the whole shaft.
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Part 11: Bone Marrow and Hemopoiesis
Slide 1
Bone marrow seen with low power (to the left). This
marrow cavity lies within a shaft of compact bone
(middle, pink band). Attaching muscle is to the right.
Slide 2
Bone marrow surrounding a pink, Y-shaped piece of
spongy bone. Notice the small osteocytes scattered
within the bony matrix. In the marrow there are
clumps of small blood-forming cells scattered
among the large round fat cells. (The lipid content of
the fat cells has been dissolved out in fixation of the
tissue). The elements formed most abundantly in
marrow are r.b.c.'s, granular leukocytes, and platelets. Lymphocytes and monocytes are also formed
here, but go elsewhere to proliferate. Another name
for blood-forming tissue such as this is hemopoietic
or myeloid tissue.
Slide 3
Bone marrow showing the typical cellular masses of
developing blood cells lying between the round,
empty fat cells. There are two large megakaryocytes
in the field, one just about in the center and the other
to the extreme right. Notice orange-colored rbc's in
thin-walled sinusoids.
Slide 4
Bone marrow - higher power - identifiable by the fat
cells, clusters of developing blood cells, and the
large megakaryocytes. Also, in the middle of the
field is a cross section of a sinusoid filled with rbc's.
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Slide 5
Sinusoid of bone marrow seen here in longitudinal
section. There is a good nucleus of a lining endothelial cell near the lower center of the field. Junctions between lining cells are loose so that newly
formed blood cells can enter the vessels.
Slide 6
Megakaryocyte as seen in an H & E stained section.
Note its multilobed nucleus and its comparatively
giant cell size. (Remember that the other giant cell of
bone, the osteoclast, has multiple separate nuclei.
The osteoclast lies next to bone, while the megakaryocyte lies out in the middle of the marrow.)
Slide 7
Another megakaryocyte, this time as seen in a marrow smear with the May-Grunwald-Giemsa blood
stain. In a smear the whole cell is here, though
somewhat flattened. The lobed nucleus seems drawn
together into a compact mass. Fragments of cytoplasm will form platelets.
Slide 8a
In a section like this, stained with H & E, the developing blood cells are hard to identify. However,
about in the middle of the field one can recognize a
nearly mature eosinophil with bright red granules.
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Slide 8b
EM of eosinophil. Notice the crystalloid bar in the
granules.
Slide 9
Identification of cells is somewhat easier in marrow
stained with phloxine - methylene blue - azur II.
Here we see a megakaryocyte near the rim of the fat
cell to the left. Immediately below is a brightly
stained eosinophil. The pale oval nucleus just to the
right of the eosinophil belongs either to a reticular
cell or a hemocytoblast (stem cell); both are primitive cells and similar in appearance in a section like
this.
Slide 10
A reminder that bone marrow is one place where you
find a stroma of reticular tissue. Here the tissue has
been silvered so that you can see the network of fine
reticular fibers that support all the blood forming
cells. Large spaces represent fat cells.
Slide 11
Diagrammatic summary of the events that take place
during maturation of red blood cells (erythropoiesis).
Staining is with special blood stains (Giemsa, etc.).
Primitive status is on the left; mature status is on the
right.
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•
•
•
Top line: there's a decrease in cell size (from
left to right) and a decrease in basophilia
(blueness) of cytoplasm. At the same time,
hemoglobin increases, making the cytoplasm
more and more acidophilic (pink). Basophilia
is due to presence of abundant
polyribosomes.
Second line: there's a decrease in nuclear size
and ultimately extrusion and loss of the nucleus.
Third line: there's increased condensation of
nuclear chromatin and eventual pyknosis of
the nucleus (very dark, compact, dying).
Also the nucleoli, evident at first, are soon
lost.
•
•
•
Slide 12
Maturational stages in development of granular leukocytes:
•
Extreme left - myeloblast (the most primitive
stage)
• Next - promyelocyte (these first two stages
are undifferentiated precursors of all three
granulocyte types)
• Next four: myelocyte, metamyelocyte, band
cell, and mature cell
The top row represents the eosinophilic cell line, the
middle row represents the neutrophilic line, and the
bottom row represents the basophilic line. Note the
decrease in cell size, the decrease in cytoplasmic basophilia (meaning decrease in polyribosomes), the
increase in cytoplasmic granules (these first become
specific and distinguishable as eosinophilic or basophilic at the myelocyte stage), and an increase in lobulation of the nucleus. The next few slides are of
smears of bone marrow stained with modified
Giemsa stains, so we can rely on the color of cells
in identifying their developmental status.
•
•
•
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Slide 13
The cells shown here are all stages in the development of erythrocytes. Generally in the red blood cell
line: (1) the cells become progressively smaller, (2)
the cytoplasm changes from blue to pink, and (3) the
nucleus becomes smaller and more condensed and
ultimately is lost altogether. Cells shown here
include (in developmental order):
•
•
Top cell - proerythroblast
Lower row
o left = basophilic normoblast or erythroblast. It is still blue, but is smaller; the
nucleus is more condensed
o middle = polychromatophilic normoblast or erythroblast. Cytoplasm is grayer
or muddier; nucleus is even more condensed.
o right = orthochromatic (or eosinophilic) normoblast. Cytoplasm is pinker and
cell is smaller; nucleus is pyknotic.
Slide 14
This grouping is similar to the preceding one: c =
proerythroblast, very large and has blue cytoplasm. a
= polychromatophilic erythroblast (muddy colored
cytoplasm). b = eosinophilic (orthochromatic) normoblast - with quite pink cytoplasm, and a small
pyknotic nucleus being extruded.
Slide 15
Reticulocytes with polyribosomal remnants (RNA)
staining dark in their cytoplasm. They are slightly
larger than the completely mature erythrocytes and
are often found in the peripheral bloodstream at
times when blood cells are being formed unusually
rapidly (as during or after certain blood diseases).
Remember not to confuse reticulocytes of the blood
with reticular cells of connective tissue!
Slide 16
A neutrophilic series showing changes in cell size
and nuclear shape:
•
•
•
•
•
•
g = early neutrophilic myelocyte (large cell,
rounded nucleus)
b,e,f = late neutrophilic myelocyte or early
metamyelocyte (nucleus beginning to indent)
d = neutrophilic metamyelocyte (indented
nucleus)
h = neutrophilic band cell (much thinner nucleus)
c = segmented (mature) neutrophil
a = polychromatophilic erythroblast (muddy
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colored cytoplasm and not very much of it)
Slide 17
The young cells in the r.b.c. line all have blue cytoplasm, so you have to consider their size in identifying them.
• a = the larger cell and, therefore, a proerythroblast.
• b = smaller, and therefore a basophilic erythroblast.
• d = still smaller and, therefore, a polychromatophilic erythroblast.
• c = small lymphocyte (too small to be a basophilic erthyroblast).
• e,f,g = all neutrophilic myelocytes
Slide 18
•
•
•
•
a = eosinophilic (orthochromatic) erythroblast - a small cell with pyknotic nucleus and
pink cytoplasm.
f,g = lymphocytes (very small, with dark nucleus and very thin rim of cytoplasm)
d = promyelocyte, with abundant azurophilic (non-specific) granules in the cytoplasm.
A large cell.
b = eosinophilic metamyelocyte (note seedlike, pink, cytoplasmic granules)
• c,e = neutrophilic metamyelocyte
Slide 19
The large cell with blue cytoplasm is a "blast" cell
although simple observation cannot tell us whether
it's a myeloblast or an erythroblast. To the left is a
group of neutrophilic band cells; the Iower two are
probably more advanced, judging by their more
segmented appearance. At bottom center is an orthochromatic normoblast with pyknotic nucleus. In
the upper right corner (and probably lower left corner) is a lymphocyte.
Slide 20
There is a large "blast" cell in the upper left group
and a large promyelocyte at upper center. The latter
is recognizable by the non-specific azurophilic granules in its cytoplasm, foretelling that it is heading
toward one of the granulocyte lines. A basophilic
normoblast with blue cytoplasm is in lower center.
To the right of it are two early orthochromatic normoblasts. At bottom center is a late polychromatophilic normoblast with muddy cytoplasm. A slightly
younger polychromatophilic cell is in the extreme
lower left corner, with a slightly larger and less condensed nucleus. A neutrophilic metamyelocyte with
indented nucleus also lies near the lower edge of the
field.
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