HISTOLOGY A Microscopic Study of Human Body Tissues and

HISTOLOGY
A Microscopic Study of Human Body Tissues and Mitotic Cells
Introduction:
Histology is the microscopic study of plant and animal tissues. Although all organisms are composed of at least
one cell, we will be concentrating on observing cells and tissues of the human body.
All organisms are composed of cells. Human body cells are grouped by their similarities in structure and function
into tissues. There are more than 200 different types of tissues of the human body and all of these may be
categorized into one of four groups: Epithelial tissue, Connective Tissue, Muscle tissue and Nervous tissue.
In order to view these tissues, samples were taken from organs. Organs are macroscopic structures which are
composed of more than one tissue type and perform a specific function for a multi-cellular organism. Because you
will be observing sections of organs, you will see several different tissues in each slide so it is important to scan
the slide in order to find the tissue of interest.
The thinly sliced sections of organs were mounted and stained with dyes (commonly hematoxylin and eosin) or
stains that provide blue and red color to the tissues. In some cases, differential stains are used to stain specific
structures.
As you view the different slides, it is to your advantage to view all of the slides within each group before observing
slides of a different group. For example, you may start with connective tissues so you would view all of the slides
or tissues that are grouped within this category identifying common characteristics before moving on to the
epithelial tissues.
Note: As a novice microscopist it is important to remember a few things!
You may only have one slide at your bench at a time.
Your single slide should always be placed on the stage and never on your bench or in your notebook.
No slide is ‘created equal’. Each specimen on every slide is unique so if you have problems with one slide after a
few minutes—review the histology photo album and/or return that slide and get a different slide with a different
label. If that does not work, be sure to ask your instructor for advice!
Each slide is labeled with a tissue you can find on the slide. However, the specimen that provided the sample
often includes several different tissues—so you must scan the slide in order to find the tissue identified on the
label.
Lab Exercise: Histology (Revised Spring, 2012), Page 1 of 17
Activity 1: Microscopic Observation of Epithelial Tissue
Epithelial tissue covers body surfaces, lines the lumens of body tubes and lines most of the body cavities. As a
cover, there is ‘free’ space on one side of the tissue and other cells located on the other side of the epithelial
tissue. As we look at these tissues under the microscopic, one key observable characteristic is to find the white or
empty (usually) space on one side and then identify the specific epithelial tissue but the cell shape that is on this
apical surface.
The name of the epithelial tissue describes its general structure: the number of
layers and the individual cell shape. The cell shape on the
apical surface (next to the free space) is used to identify
the tissue without regard to the deeper cell shape. Cells are
described as squamous (flat), columnar (tall), cuboidal
(roughly cube-like or spherical).
Stratified
squamous
squamous
cuboidal
columnar
Microscopically the different epithelial cell shapes can be
identified by the amount of cytoplasm surrounding a
stained nucleus. The squamous cells have very little
cytoplasm and look very similar to an egg ‘sunny side up.’
Cuboidal cells will have about the same amount of
cytoplasm from the nucleus to the edge of the cell
membrane in any direction. While, columnar cells
commonly have a lot of cytoplasm between the nucleus
and the apical surface.
Simple epithelial tissues include a single layer of cells,
while stratified indicates that there are many layers of
epithelial cells. Pseudostratified indicates that the cells
appear many layered, but are actually a single layer of
cells. Individual cells may be squamous (flat), cuboidal or
columnar. Individual cells may also have cellular structures
that contribute to their function, such as, cilia or microvilli.
Epithelial tissues are attached to an underlying connective
tissue by a basement membrane. The basement
membrane is composed of substances which are secreted
by the epithelial cells and connective tissue cells forming a
thin layer marking the margins (boundaries) between the
two tissues.
Lab Exercise: Histology (Revised Spring, 2012), Page 2 of 17
Procedure:
1) Before Lab, complete the definitions and complete the table in your lab notebook identifying common
locations and functions for each of the following tissues. You will need to use your textbook and/or lecture
notes to help you complete this portion of your lab notebook.
2) Before Lab, update your histology atlas in your lab notebook by (pencil) drawing a sketch of the following
epithelial tissues you will be observing in lab.
a.
b.
c.
d.
e.
simple squamous epithelial tissue
simple cuboidal epithelial tissue
simple columnar epithelial tissue
pseudstratified ciliated columnar epithelial tissue
stratified squamous epithelial tissue
3) Use your textbook and the Histology Photo Album On-Line to draw each epithelial tissue as listed below.
Include the following labels for each epithelial tissue within your histology atlas: (You may use a pencil to label
any drawings).
a. title of the tissue
b. apical surface
c. nucleus
d. basement membrane
e. cell membrane
f. cytoplasm
g. Other cellular features shown in bold-faced type as you read through the lab manual description of
the tissue should also be labeled on the corresponding drawings.
4) Note: Coloring your drawings of the histology atlas is considered optional.
5) Note: There is space provided in your histology atlas for Notes. This area is for you to make notes to yourself
about the tissue you are observing. In some cases, you may wish to give yourself directions on what to look
for in order to find this tissue at a later date.
Lab Exercise: Histology (Revised Spring, 2012), Page 3 of 17
6) Observe the Simple Squamous Epithelial slide using your high power objective lens.
Simple Squamous Epithelial Tissue 10X
Objective Lens
This photograph of a sample of kidney tissue
clearly demonstrates the white space which is
where to look for epithelial tissues under
higher powers.
Simple Squamous Epithelial Tissue 40X
Objective Lens
Simple squamous epithelial tissue is found
making up the capsule that surrounds the
glomerulus, a capillary bed. The cells are
extremely flat, almost line-like with slightly
raised purple bumps of the nuclei.
The arrow is pointing to the nucleus of a
single simple squamous epithelial cell.
Lab Exercise: Histology (Revised Spring, 2012), Page 4 of 17
7) Observe the Simple Cuboidal Epithelial slide using your high power objective lens.
Simple Cuboidal Epithelial Tissue
10X Objective Lens
This photograph of a sample of
kidney tissue clearly demonstrates
the white space which is where to
look for epithelial tissues under
higher powers.
Simple cuboidal cells make up
tubules within the kidney. The lines
of white demonstrate the apical
surface of simple cuboidal while
other tubules are sectioned to see
the lumen lined with cuboidal cells.
Simple Cuboidal Epithelial Tissue
The simple cuboidal cells form
the lumen of the tubule. Cuboidal
cells have approximately the same
amount of cytoplasm surrounding
their nucleus in all directions. You
should be able to identify the line
marking the basement membrane
of the epithelium.
Some cuboidal cells of the kidney
have microvilli; fine-brushlike
extensions of the cell membrane at
the apical surface. Microvilli usually
require light adjustment and/or use
of the oil immersion lens.
The arrow is pointing to the
basement membrane of a simple
cuboidal epithelial cell.
Lab Exercise: Histology (Revised Spring, 2012), Page 5 of 17
8) Observe the Simple Columnar Epithelial slide using your high power objective lens.
Simple Columnar Epithelial
Tissue
The simple columnar
epithelium can be seen next
to the large free surface. The
dark pink nuclei are aligned
in a row. The basement
membrane separates the
single layer of columnar
cells from the deeper
connective tissues.
Under high power, not only
are the simple columnar
epithelial cells identifiable but
there are goblet cells
interspersed in many
specimens. Scan the free
surface and try to identify a
goblet cell on your slide.
Goblet cells produce mucous
and secrete it toe the free
surface.
Lab Exercise: Histology (Revised Spring, 2012), Page 6 of 17
9) Observe the Pseudostratified Ciliated Columnar Epithelial slide using your high power objective lens.
The slide of a specimen from the trachea is the most
common example used for pseudostratified ciliated
columnar tissue. The epithelial tissue is always located at
a free surface, so scan the outer margins of the specimen
to locate it.
Pseudostratified ciliated columnar epithelial tissues are an
example of simple columnar shaped cells, but appear
stratified due to the irregular placement of the nuclei in
adjacent cells.
Under high power (below), numerous goblet cells and cilia
are easily viewed. The goblet secrete mucous that traps
inhaled dirt, debris and microbes preventing them from
entering into deeper airways. The cilia propel the mucous
anteriorly toward the pharynx.
Lab Exercise: Histology (Revised Spring, 2012), Page 7 of 17
10) Observe the skin slide and find the Stratified Squamous Epithelial slide using your low power and high
power objective lens.
At the apical surface is the epidermis, darkly stained stratified
squamous epithelial cells show the dermal papillary ridges
which are the ridges of your finger prints.
(The deeper dermal layer, lighter pink stain is composed of
dense irregular connective tissue.)
Under high power, the stratified squamous
epithelium is named for the cell shape at the
apical surface. Toward the basement membrane,
the cells become more rounded but are still part of
the stratified squamous epithelium. The epithelial
cells nearest the basement membrane are highly
mitotic and producing new cells which replace the
dead cells that are constantly sloughed off the
surface.
Lab Exercise: Histology (Revised Spring, 2012), Page 8 of 17
Activity 2: Microscopic Observation of Connective Tissue
Connective tissues include a wide variety of different tissues that function to protect, support and bind together
other body tissues. Connective tissues are found throughout the body and are the most abundant tissue type!
There are two general characteristics common to all connective tissue: (1) an extracellular matrix and (2) unique
cells.
The extracellular matrix is the substance located outside of the connective tissue cells. The ground substance
includes water and adhesion proteins that allow the connective tissue cells to attach. Scattered throughout the
matrix are proteins (fibers) and include collagen (strength), elastin (stretch and recoil) and reticular fibers (fine
collagen fibers). The amount of extracellular matrix and its composition will vary from one connective tissue to
another.
The unique cells of connective tissue are largely responsible for the production and maintenance of the matrix. In
many instances, the cells are separated by large amounts of matrix, while other connective tissue cells lie close
together with very little matrix in between.
Procedure:
1) Before Lab, complete the definitions and complete the table in your lab notebook identifying common
locations and functions for each of the following connective tissues. You will need to use your textbook and/or
lecture notes to help you complete this portion of your lab notebook.
2) Before Lab, update your histology atlas in your lab notebook by (pencil) drawing a sketch of the connective
tissues you will be observing in lab.
a) Your histology atlas should include a labeled diagram of
Compact bone
Hyaline cartilage
Adipose
Blood
b) Each connective tissue will have a variety of unique anatomical features to label. Be sure to read the
descriptions closely and label all (bold faced) anatomical features, including cell types and matrix, for
each connective tissue slide. Refer to your textbook and the On-Line Histology Photo Album to check
your correctly labeling the anatomic features of each connective tissue.
c) Note: Coloring your diagrams is considered optional.
d) There is space provided in your histology atlas for Notes. This area is for you to make notes to yourself
about the tissue you are observing. In some cases, you may wish to give yourself directions on what to
look for in order to find this tissue at a later date.
Lab Exercise: Histology (Revised Spring, 2012), Page 9 of 17
3) Observe the Ground Compact Bone slide using your high power objective lens. Identify the different parts of
the tissue as described.
Compact bone looks very much like a cross section
of a tree—the rings of the tree correspond to rings
of calcium salts and collagen fibers of the matrix.
Each ‘tree’ is an osteon—a cylindrical unit of
compact bone.
At the center of the rings is a space, the central
canal, which may have blood vessels and/or nerves
passing through. Arranged within the concentric
rings of matrix are the bone cells, osteocytes.
Each osteocyte occupies its own small space,
called a lacuna. Extending from the lacuna are tiny
canals, canaliculi, which allow a conduit for
exchange between cells and between the
osteocytes and its blood supply.
In order to see an osteocyte within a lacuna, it may
be necessary to adjust the light (iris diaphragm
lever) or use the fine focus and take the slide in and
out of focus so that the osteocyte ‘pops’ out
This photo has a different staining technique than
you will view in lab, the matrix is stained black. The
osteocytes (cells) are located within the lacunae
(white space) which are interconnected by small
canals/canaliculi.
Lab Exercise: Histology (Revised Spring, 2012), Page 10 of 17
4) Observe the Hyaline Cartilage slide using your high power objective lens. Identify the different parts of the
tissue as described.
Hyaline cartilage is the most abundant
cartilage—it contributes a flexible structure to
the nose, larynx, trachea, ends of bones and
makes up the fetal skeleton. Hyaline cartilage
is much more flexible and less rigidly arranged
than bone.
Hyaline cartilage may be stained with a pink
or purple stain. (Refer back to the trachea
image for the purple stain).
As you view the slide of hyaline cartilage, the
cells are irregularly spaced apart. Each cell,
chondrocyte, occupies a space within the
matrix called a lacuna.
The matrix contains abundant collagen fibers
but due to the other components of hyaline, it
gives the matrix a ‘glassy’ appearance.
5) Observe the Adipose slide using your high power objective lens. Identify the different parts of the tissue as
described.
Adipose tissue looks like chicken wire
microscopically or each cell looks like a signet
ring.
The cytoplasm of the adipocyte, adipose cell,
is filled with a fat vacuole that stores fat for the
body. The nucleus is often pushed snug
against one side of the cell membrane to allow
the fat vacuole to expand.
Adipose tissue is a modified areolar connective
tissue with all types of fibers between the cells.
However, due to the function as long-term fat
storage, there is very little space between
individual cells so you will not see much matrix
between the adipocytes of adipose tissue.
Blood vessel
Lab Exercise: Histology (Revised Spring, 2012), Page 11 of 17
6) Observe the Blood Smear slide using your high power objective lens. Identify the different parts of the tissue
as described.
Blood is the only fluid or liquid connective tissue.
The extracellular matrix is composed of blood
plasma. The formed elements (cells) of blood
include erythrocytes (red blood cells) and
leukocytes (white blood cells).
The erythrocytes are composed of cell
membrane and their cytoplasm is filled with
hemoglobin which give them their pink
appearance. Upon maturation, erythrocytes eject
their nucleus in order to maximize the intracellular
space for hemoglobin and oxygen carrying.
Leukocytes are only visible when stained. There
are a variety of different types of leukocytes found
in blood. Leukocytes are identified by the shape
of their nucleus, size and presence of granules
(stained storage areas). You will note that the
number of erythrocytes greatly outnumber
leukocytes.
In addition, thrombocytes (blood platelets) are
small cell fragments may be seen between the
formed elements of blood.
Lab Exercise: Histology (Revised Spring, 2012), Page 12 of 17
Activity 3: Microscopic Observation of Muscle Tissue
There are three different types of muscle tissue—each is specialized to contract (shorten) producing movements.
Cardiac muscle is only found in the heart and its contractions are used to pump blood through arteries. Smooth
muscle contractions cause the movement of substances within body tubes food through the esophagus or small
intestine. Contractions of the smooth muscle making up arterial walls contribute to maintaining blood pressure.
Skeletal muscle carries out voluntary contractions of body movement like walking and talking.
Procedure:
1) Before Lab, complete the definitions and complete the table in your lab notebook identifying common
locations and functions for each of the following muscle tissues—skeletal, smooth and cardiac muscle. You
will need to use your textbook and/or lecture notes to help you complete this portion of your lab notebook.
2) Before Lab, update your histology atlas in your lab notebook by (pencil) drawing a sketch of the muscle
tissues you will be observing in lab.
a) Each type of muscle issue will have a variety of unique anatomical features to label. Be sure to read
the descriptions closely and label all anatomical features (bold-faced) for each muscle tissue slide and
use your textbook and On-Line Histology Photo Album to help in your identifications.
b) Note: coloring your diagrams is considered optional.
c) There is space provided in your histology atlas for personal Notes and observations.
3) Observe the Skeletal Muscle slide using your high power objective lens. Identify the different parts of the
tissue as described.
Skeletal muscle is composed of long cylindrical cells. The
individual cells can be as long as the muscle itself. As the
muscle length increases, the individual cells get ready to divide,
double their cytoplasmic contents including nucleus, but they
do not complete cytokinesis thus ending up as long
multinucleate cells.
By finding an area on the slide of the muscle fiber running
longitudinally (lengthwise) you will note that you cannot see the
‘ends’ of the cell.
Running perpendicular to length of the cell you should see
striations (stripes) composed of the proteins actin and myosin.
These proteins carry out the contraction (shortening) of the cell.
Lab Exercise: Histology (Revised Spring, 2012), Page 13 of 17
4) Observe the Smooth Muscle slide using your high power objective lens. Identify the different parts of the
tissue as described.
The cells making up smooth muscle are spindle shaped, long
with narrowed ends. Smooth muscle cells are not nearly as
long as skeletal muscle fibers (cells).
The photograph shows the darker stained nuclei within the
individual smooth muscle cell cytoplasm. Smooth muscle is
often arranged in layers—running in different directions. In
this photograph, there is just one layer running mostly
vertically.
Smooth muscle contains actin and myosin but it is arranged
in the same fashion as skeletal muscle so smooth muscle
cells lack striations
.
5) Observe the Cardiac Muscle slide using your high power objective lens. Identify the different parts of the
tissue as described.
Cardiac muscle cells are much shorter in length and
uninucleate (single nucleus).
As the cardiac muscle cells are arranged, they form
branching patterns.
Connecting adjacent cardiac muscle cells are
specialized cellular junctions called gap junctions
called intercalated discs which are darker pink
than the striations seen throughout the cytoplasm
of the cardiac muscle cell.
Lab Exercise: Histology (Revised Spring, 2012), Page 14 of 17
Activity 4: Microscopic Observation of Nervous Tissue
Nervous tissue is composed of two general cell types: (1) neurons and (2) glial or support cells. Neurons are
specialized to conduct an electrical impulse called an action potential across its length. These action potentials
are responsible for our being able to sense our environment, process this information and carry out an
appropriate response in order to maintain homeostasis
Procedure:
1) Before Lab, complete the definitions and complete the table in your lab notebook identifying functions for the
different parts of a neuron. You will need to use your textbook and/or lecture notes to help you complete this
portion of your lab notebook.
2) Before Lab, update your histology atlas in your lab notebook by (pencil) drawing a sketch of the neuron smear
you will be observing in lab and label the anatomical structures (bold-faced) common to neurons. Use your
text book to aid you in your identifications.
a) There is space provided in your histology atlas for Notes. This area is for you to make notes to yourself
about the tissue you are observing. In some cases, you may wish to give yourself directions on what to
look for in order to find this tissue at a later date.
3) Observe the Neuron Smear slide using your low power objective lens. Identify the different parts of the tissue
as described.
Neurons are large cells surrounded by much and smaller
and numerous glial cells.
The cell body of a nueron includes most of the
cytoplasm and nucleus. The nuclei are large, highly
visible, and often you will find the nucleolus within the
nucleus that looks like an ‘owl’s eye’.
Extending from the cell body are long cellular extensions
called processes. Different processes are responsible for
different parts of the action potential or conduction of the
electrical impulse. Neurons, including their cellular
processes, can be very long—you actually have a
neuron which is up to 3 feet long running from the
terminal end of your spinal cord to your big toe!
Each neuron has one axon. The axon typically identified
because it is the largest process attached to the neuron’s
cell body.
Dendrites are all of the other cellular extensions.
Dendrites are responsible for sensing the environment
and starting an electrical impulse which travels toward
the cell body. Axons are responsible for continuing the
action potential along its length away from the cell body.
Lab Exercise: Histology (Revised Spring, 2012), Page 15 of 17
Activity 5: Mitosis
In order to increase in body size, we need to increase our cell number; or, tissue repair involves replacing cells
with new cells. Creating new cells is achieved through cell division. Cell division includes nuclear division
(mitosis) and cytoplasmic division (cytokinesis). Mitosis is the type of cell division that creates new cells
involved in both growth and tissue repair. Mitosis results in genetically identical cells called clones. These cells
have the same number and kind of DNA, as the parent cell.
The cell cycle which includes all of the phases a cell undergoes from its formation until it divides. Most of a cell
cycle, the cell is in Interphase. Where the cell is undergoing normal metabolic activities—carrying out its
designated function, making proteins, synthesizing ribosomes, accessing the genetic code stored in DNA and
replicating DNA. The DNA is accessible to nuclear proteins to make cytoplasmic proteins and ribosomes, it
appears granular microscopically and is called chromatin. Within the nucleus are darkened condensed areas
where ribosomes are being synthesized so the nucleoli are clearly visible. Separating the chromatin from the
cytoplasm is the nuclear envelope.
Mitosis, nuclear division, describes how the two sets of DNA which is formed during interphase are divided so
that each daughter cell has its own complete set of genetic instructions. Mitosis includes the following phases:
Prophase, Metaphase, Anaphase and Telophase.
Prophase is the stage where the strands of DNA are packaged into chromosomes. During prophase, centrioles
are assembled from cytoplasmic proteins, the nucleolus disappears, and the nuclear membrane is disassembled.
Metaphase is identified by the alignment of the chromosomes at the cells equator. An animal cells, centrioles
have migrated to opposite poles and connecting the centrioles to the chromosomes are long proteins fibers
called the spindle apparatus.
Anaphase occurs as the chromosomes
are moved by the spindle apparatus
towards the centrioles. One DNA
molecule and it’s replicate (copy) are
moved so that each new daughter cell has
the same genetic information to begin
metabolism immediately upon cytoplasmic
division.
Telophase is marked by the unpackaging
of the chromosomes back into its
accessible form, chromatin. The nuclear
membrane is reassembled, nucleoli
reappear and both the centrioles and
spindle apparatus is disassembled.
Lab Exercise: Histology (Revised Spring, 2012), Page 16 of 17
Procedure: Mitosis
1) Before Lab, complete the descriptions of the cellular events that occur during all stages of the cell cycle. Label
the diagram for each mitotic phase.
2) Before Lab, prepare your lab notebook, by drawing interphase and each stage of mitosis for an onion cell
in your histology atlas. Label the anatomical structures that are visible during each phase.
3) During lab, observe an onion mitosis slide has several different root tip specimens on it; each root tip has
many cells which are in various stages of division. So, as you view a root tip microscopically, you will most
likely find several different mitotic phases in one field of view.
Using your scanning objective you will note that one end of the onion root tip is pointed
while the other is level or torn. The area of mitosis will be best viewed toward the root tip.
See the red boxed area.
INTERPHASE
The nucleus has a granular appearance where the DNA is called chromatin. In many
cases one or more darkened areas of the nucleoli and nuclear membrane. Remember,
the cell membrane of a plant cell is also surrounded by a thick cell wall.
PROPHASE
The nuclear membrane has been disassembled and the chromatin is condensing into
chromosomes.
METAPHASE
The chromosomes have aligned at the cells equator and the spindle apparatus can be
seen. (Note there are no centrioles).
ANAPHASE
The chromosomes are being separated and moving by the spindle apparatus to
opposite poles. (On the right hand side are two onion cells in interphase, while the upper
left hand cell is in prophase).
TELOPHASE
The chromosomes are being unpackaged and losing the linear (noodle) appearance. At
the cell’s equator a new cell wall is being laid down, so cytokinesis is a concurrent event.
Lab Exercise: Histology (Revised Spring, 2012), Page 17 of 17
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Title:
HISTOLOGY
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