EUMETAZOA = true animals

EUMETAZOA = true animals
In contrast to sponges and placozoans (PARAZOA=near animals)
Eumetazoans are composed of functionally specialized cells that
are arranged in:
-tissues:
-organs
execute a
nervous…
-collection of cells of a particular type
that are arranged
-primary tissues
-secondary tissues
-tissues that works together to
particular biological function
-can be grouped to organ system for
example circulatory, digestive,
Tissues
Primary tissues
Bindväv=
Secondary tissues
Primary tissues
A. Epithelial tissue
- A cell layer that covers surfaces
- lines internal cavities and spaces
…to maintain a chemical difference between adjacent
compartments
Four characteristics:
-its cells are arranged in a continuous unbroken layer
-have apical-basal polarity
-rest on basal lamina (ECM)
-are joined by intercellular junctions
(cellkontakter/
förbindelser)
förbindelse
A. Epithelial tissues
Are classified on the basis number of layer present
- invertebrates: one layer of cells: simple epithelium (enkelskiktat)
- vertebrates: one, two or more layers: stratified epithelium
(flerskiktat)
and on the basis of form:
-flat: squamous epithelium (skivepitel)
-cube shaped: cuboidal epithelium (kubiskt epitel)
-column like: columnar epithelium (cylinderepitel)
The apical side can have:
-cilia
-microvilli
-cuticle (ECM)
A. Epithelial tissues
Functions:
- protection
- support
- transport
- absorption
- excretion
- respiration
- sensory reception (sensoriskt mottagning)
- production and excretion of ECM…
Modified epithelia cells
Nedsänkt körtelcell, flercellig körtelcell, sekret
Primär sinnescell
Epidermis and gastodermis
Epidermis:
Gastrodermis
- covers the surface of the eumetazoan body
- a barrier to the external environment
- allows internal regulation and homeostasis
-lines the gut cavity
Mouth
Epidermis
Gut
Gastrodermis
Basal lamina
Basal lamina
The epithelial cells secrete and rest on basal lamina that is a thin dense fibrous ECM
Extra cellular matrix (ECM)
-is an network of macromolecules
-can be external (cuticle) or internal
- composed of a variety of proteins and polysaccharides
-  are secreted locally and assembled into an organized meshwork in close
association with the surface of the cell that produced them.
- High diversity of forms: relative amounts and organization of macromolecules adapted to the functional requirements of the particular tissue
- Two main classes of extracellular macromolecules make up the matrix:
- (1) polysaccharide chains of the class called glycosaminoglycans (GAGs),
which are usually found covalently linked to protein in the form of
proteoglycans
- (2) fibrous proteins, including collagen, elastin, fibronectin, and laminin,
which have both structural and adhesive functions
The compartment between epidermis and
gastrodermis (or the two layers of basal lamina)
Mouth
Epidermis
Gut
Compartment
Gastrodermis
Basal lamina
Cells are absent: ECM
Cells are present: connective tissue (bindväv)
Sponges:mesohyl
Metazoan embryo: blastocoel
Most Cnidaria and Ctenophora: mesoglea
Higher organism: connective tissue
Motile ameboid cells that arise from epithelia and enter blastocoel: mesenchymal cells
and connective-tissue cells in adults.
Primary tissues
B. Connective tissue (bindväv)
• Serves to support and bind tissues together
• Consists of widely separated non-adjoining cells in an ECM
• The functional properties of a connective tissue is determine by the
nature of its ECM
Primary tissues
B. Connective tissue (bindväv)
Two general types
A. Areolar (or loose) connective tissue (areolär (lucker) bindväv)
-holds organs and epithelia in place
-has a variety of proteinaceous fibres, including collagen and elastin,
that are loosly packed.
B. Dense (or fibrous) connective tissue (stram bindväv)
-forms ligaments and tendons (ligament och senor)
-Its densely packed collagen fibers have great tensile strength.
…Also Reticular and specialiced connective tissue
Skeleton
Internal or external ECM or connective tissues can be modified to
form a skeleton
A skeleton is any structure that
-supports the body
-transmits the force of muscular contraction
-sometimes provides protection
ECM or connective tissue can be stiffened by
-chemically cross-linking of proteins (as in cartilage)
-mineral secretion (as in bone)
Three basic design of skeleton
1.  Hydrostatic skeleton
2.  Rigid (styvt) skeleton
3.  Pliant (böjligt) skeleton (cartilage)
2 and 3 both exoskeleton and endoskeleton
1. Hydrostatic skeleton or hydrostat
water-filled space surrounded by flexible walls, like a balloon
The body is supported by slightly pressurized water
Volume is constant or can be changed (sea anemone tentacle)
Animals with cylindrical bodies
Covered by fibrous mesh of inelastic fibers- to prevent aneurism (aneurysm)
- orthogonal pattern
-cross-helical pattern -is suitable for body walls
-proteins for example collagen
Fig. 6-3 OH
Hydrostatic skeleton
Coelenteron in Cnidaria
Water-vascular system in Asteroidea
Coelom in Annelida
Hemal system in spiders
Rigid skeleton
solid skeleton that resist any change of shape (shell, bone)
Exoskeleton or endoskeleton
May form
a supportive platform of stony corals (Scleractinia)
a lattice arrangement (gallerverk) as in glass sponges
a framework (stomme) of beams and levers as in the
appendage of insects and vertebrates
More common in
terrestrial animals
animals that move rapidly in water (crustaceans and
fishes)
in exposed sessile and slow-moving animals (snails)
Rigid skeleton
endoskeleton (from syncytium) of glass sponges
exoskeleton in Scleractinia (stony corals)
Lophelia (ögonkorall i Bohuslän)
Spicules ( from sclerocytes) in sponges
Exoskeleton (from mantle epithelium) in Gastropoda
Pliant skeleton
Endoskeleton or exoskeleton
Deform when stressed
Elastic and spring back to their original shapes
In invertebrates:
in the hinge of clams
supportive structures of horny corals (sea
fans)
Composed by proteins, polysaccharides and water
Range in consistency from water gels (as mesohyl in sponges and
mesoglea of a few comb jellies) to stiff.
Advantage: muscle power is required only for the initial change of
shape
Can be made stiffer by the addition of rigid pieces (spicules) or organic
fibers (collagen (spongin), chitin, cellulose)
Pliant skeleton
Gorgonium (axal rod) in Sea fans (Gorgonacea )
Mesophyl in sponges
Cartilage in squids
Hinge ligament of clams
Cnidaria skeleton
Fig 7-4 OH
2. Secondary tissues
A.  Muscle tissues
B.  Nervous tissues
1. Epitheliomuscular cells (epitelmuskelcell)
Muscle fibrils (actin and myosin filaments) in a fixed arrangement
Located within the basal part of epithelial cells
Hydra, sea anemone (fig 7-2,)
2. Myoepithelial cells
Similar but the apical ends of cells is reduced and not exposed
iris of the eyes, human sweat glands, mammary glands
3. Myocytes= true muscle cells
Lost their epithelial characteristics
Connective-tissue compartment
Three basic forms of muscle tissues
Fig 6-5 OH
1.Smooth muscle (glatt muskulatur)
-contract slow
-develop tension over a wide range of lengths
-in extensible body or appendage (tentacle)
Primitive in Cnidaria and Ctenophora
-actin filament anchor directly to cell membrane
Bilaterian in flatworms, molluscs, gut musculture in many animals
- z-dense bodies
2. Cross-striated muscle (tvärstrimmig muskulatur)
-contract fast
-develops tension over a limit of stretch lengths
-associated by a body or appendage that moves quickly
over a fixed distance
-swimming undulation, snapping of jaws or claws
Retraction of tentacles in bryozoans
3. Obliquely striated muscle (skev/indirekt tvärstrimmig muskulatur)
-intermediate
-soft-bodied & extensible animals earthworms, also rapid moves
Smooth muscle
Cross-striated muscle
Antagonistic muscle set
Agonist moves the body/appendage in one way
antagonist moves the body/appendage in opposite way
A muscle can only contract
Biceps-triceps
Sea anemone fig 10-1 OH
Circular-longitudinal muscles
Vissa undantag muskler-böjligt , hydro- skelett
Tendonal attachment of an insect muscle to the skeleton
Tendon (sena) is a fibrious connective tissue (fibrös bindväv,
(collagen) fibers+tendonal cells (tenocytes in vertebrates)
specialised epidermal cells) that connect muscle to skeleton
The molting animal must maintain a mechanical connection
between muscle and skeleton
One bundle is composed of intracellular microtubules
(cytoskeleton, alfa o beta tubuli)
Spans the tendonal cell and links them to the muscle
myofilaments by desmosomes
Extracellular tonofilaments (keratin) is sectreted from the apex
of tendonalcell-attach then to cuticula-not hydrolysed during
molting
Fig 16-6 OH