HISTOLOGY
Samenvatting College 1 + 2 (Epithelia + Gland tissue) (chapter 4 161 to 172)
Tissues are structures with discrete structural and functional properties that combine
to form organs.
1.1 The four tissue types
Tissues are collections of specialized cells and cell products that perform a relatively
limited number of functions.
Four types
1. Epithelial tissue
o Covers exposed surfaces
o Lines internal passageways and chambers
o Form glands
2. Connective tissue
o Fills internal spaces
o Provides structural support
o Stores energy
3. Muscle tissue
o Contracts to produce movement
4. Nervous tissue
o Propagates electrical impulses
o Carries information
Histology is the study of tissues
1.2 Epithelial tissue
Epithelial tissue includes
- (Covering) Epithelia; layers of cells that cover external or line internal surfaces.
- Glands; structures that produce fluid secretions. Attached to or derived from
epithelia.
Functions of epithelial tissue, epithelia
- Provide physical protection; protect surface from abrasion, dehydration and
destruction by chemical or biological agents
- Control permeability; substance that enter or leaves body must cross
epithelium. Epithelia are permeable or not.
- Provide sensation; neuroepithelium is an epithelium that is specialized to
perform a particular sensory function. Provide sensations of smell, taste, sight,
equilibrium and hearing.
- Produce specialized secretions; epithelial cells that produce secretion are
called gland cells. In glandular epithelium most or all of the epithelial cell
produce secretion. Cells discharge their secretion onto surface or release
them into surrounding interstitial fluid and blood.
Characteristics of epithelial tissue, epithelia
- Polarity; presence of differences between attached surfaces.
o Apical surface; exposed to an internal or external environment
Microvilli; increases surface area
, Cytoskelet of actin (microfilaments)
Cilia; movement, sensory function. Bigger than microvilli. In total
= ciliated epithelium.
Cytoskeleton of microtubule (tubulin)
o Basolateral surface; base (basal surface) attaches underlying epithelial
cells and the sides (lateral surfaces) where the cell contacts its
neighbours.
- Cellularity; cells are closely together by interconnections; cell junctions.
- Attachment; base (basal surface) of epithelium is bound to basement
membrane. Basement membrane formed from fusion of layers (basal lamina
and reticular lamina), collagen matrix and proteoglycans. So, basement
membrane attaches epithelia to underlying connective tissues.
- Avascularity; have lack blood vessels, they get nutrients by diffusion or
absorption.
- Regeneration; epithelial cells that are damages or lost are replaced through
stem cell division. In epithelial rates of cell division and replacement high
(huidschilfers)
Specializations of epithelial cells
For epithelium as a whole to perform the functions just listed.
Individual epithelial cells specialized for
1. Movement of fluids over epithelial surface, providing protection and lubrication
2. Movement of fluids through the epithelium, to control permeability
3. Production of secretion that provide physical protection
Maintaining the integrity of Epithelia
Maintain the physical integrity of an epithelium, when it acts as barrier
1. Intercellular connections
Intracellular connections involve extensive areas of opposing (tegengestelde) plasma
membranes or specialized attachment sites (cell junction).
- Cell adhesion molecules (CAMs); areas of opposing plasma membranes are
interconnected by transmembrane proteins CAMs. They bind to each other
and to extracellular materials.
- Cell junctions; are specialized areas of plasma membrane that attach a cell to
another. Or to extracellular materials.
o Gap junctions; allows the passage of
small water-soluble ions and molecules.
2 cells hold together by interlocking
transmembrane proteins; connexons.
o Tight junctions; seals neighboring cell
together in an epithelial sheet to prevent
leakage of molecules between them.
Deep in the tigh junction there is an
adhesion belt, it is tied to (vastgebonden) the microfilaments.
They function like a zipper.
o Desmosomes; here CAMs and proteoglycans link the opposing plasma
membranes.
Spot desmosomes; small dics (schijf) connected to bands of filaments.
The filaments stabilize the shape of the cell
Samenvatting College 1 + 2 (Epithelia + Gland tissue) (chapter 4 161 to 172)
Tissues are structures with discrete structural and functional properties that combine
to form organs.
1.1 The four tissue types
Tissues are collections of specialized cells and cell products that perform a relatively
limited number of functions.
Four types
1. Epithelial tissue
o Covers exposed surfaces
o Lines internal passageways and chambers
o Form glands
2. Connective tissue
o Fills internal spaces
o Provides structural support
o Stores energy
3. Muscle tissue
o Contracts to produce movement
4. Nervous tissue
o Propagates electrical impulses
o Carries information
Histology is the study of tissues
1.2 Epithelial tissue
Epithelial tissue includes
- (Covering) Epithelia; layers of cells that cover external or line internal surfaces.
- Glands; structures that produce fluid secretions. Attached to or derived from
epithelia.
Functions of epithelial tissue, epithelia
- Provide physical protection; protect surface from abrasion, dehydration and
destruction by chemical or biological agents
- Control permeability; substance that enter or leaves body must cross
epithelium. Epithelia are permeable or not.
- Provide sensation; neuroepithelium is an epithelium that is specialized to
perform a particular sensory function. Provide sensations of smell, taste, sight,
equilibrium and hearing.
- Produce specialized secretions; epithelial cells that produce secretion are
called gland cells. In glandular epithelium most or all of the epithelial cell
produce secretion. Cells discharge their secretion onto surface or release
them into surrounding interstitial fluid and blood.
Characteristics of epithelial tissue, epithelia
- Polarity; presence of differences between attached surfaces.
o Apical surface; exposed to an internal or external environment
Microvilli; increases surface area
, Cytoskelet of actin (microfilaments)
Cilia; movement, sensory function. Bigger than microvilli. In total
= ciliated epithelium.
Cytoskeleton of microtubule (tubulin)
o Basolateral surface; base (basal surface) attaches underlying epithelial
cells and the sides (lateral surfaces) where the cell contacts its
neighbours.
- Cellularity; cells are closely together by interconnections; cell junctions.
- Attachment; base (basal surface) of epithelium is bound to basement
membrane. Basement membrane formed from fusion of layers (basal lamina
and reticular lamina), collagen matrix and proteoglycans. So, basement
membrane attaches epithelia to underlying connective tissues.
- Avascularity; have lack blood vessels, they get nutrients by diffusion or
absorption.
- Regeneration; epithelial cells that are damages or lost are replaced through
stem cell division. In epithelial rates of cell division and replacement high
(huidschilfers)
Specializations of epithelial cells
For epithelium as a whole to perform the functions just listed.
Individual epithelial cells specialized for
1. Movement of fluids over epithelial surface, providing protection and lubrication
2. Movement of fluids through the epithelium, to control permeability
3. Production of secretion that provide physical protection
Maintaining the integrity of Epithelia
Maintain the physical integrity of an epithelium, when it acts as barrier
1. Intercellular connections
Intracellular connections involve extensive areas of opposing (tegengestelde) plasma
membranes or specialized attachment sites (cell junction).
- Cell adhesion molecules (CAMs); areas of opposing plasma membranes are
interconnected by transmembrane proteins CAMs. They bind to each other
and to extracellular materials.
- Cell junctions; are specialized areas of plasma membrane that attach a cell to
another. Or to extracellular materials.
o Gap junctions; allows the passage of
small water-soluble ions and molecules.
2 cells hold together by interlocking
transmembrane proteins; connexons.
o Tight junctions; seals neighboring cell
together in an epithelial sheet to prevent
leakage of molecules between them.
Deep in the tigh junction there is an
adhesion belt, it is tied to (vastgebonden) the microfilaments.
They function like a zipper.
o Desmosomes; here CAMs and proteoglycans link the opposing plasma
membranes.
Spot desmosomes; small dics (schijf) connected to bands of filaments.
The filaments stabilize the shape of the cell
