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Tissue in which cells are tightly bound together structurally and functionally to form a sheet or tubular structure with little extracellular space between
What 2 sides do epithelial tissues have?
- Apical side and basal side
- basal side - faces basement membrane and underlying connective tissue
Epithelia side both apical and basal are specialized for what 2 functions mostly (even though they both help with barrier formation)
- Apical - absorbtion
- Basal - exocytosis
Most epithelia exhibit what kind of renewal? Meaning?
- Continuous renewal - replaced on a continuous basis, not in sheets or chunks
- location of stem cells and rates vary
What is the basement membrane? What are its two parts?
- Thin extra cellular layer of specialized proteins
- Basal lamina and reticular lamina
Describe the basal lamina
Thin meshwork of type 4 collagen and laminin produced by epithelial cells
Describe the reticular lamina in more detail. Where do you find the reticular lamina?
Contains type 3 collagen and anchoring fibrils of 7 collagen all secreted by cells of the immediately adjacent connective tissue
The basal lamina is produced by the? While the reticular lamina is produced by the?
- Epithelial cells
- Immediately adjacent connective tissue
The basement membrane connects what to what? What are the 3 main functions of it?
- Epithlia to connective tissue
- Filter substances from connective tissue to epithelia
- Provide guide or scaffolding during tissue regeneration
- compartmentalize epithelia from other tissues
Are intercellular junctions well developed or poorly developed in epithelia tissues? What are our 4 types of intercellular junctions we discuss?
- Very well developed
- Tight (occluding) junctions
- Adherent or anchoring junctions
- Gap or communication junctions
Tight junctions are composed of what proteins and serve what purpose?
Claudin and occludin
Adherent junctions are formed by what proteins and serve what purpose?
- Cadherin family
- hold epithelial cells together
Adherent or anchoring proteins can take 2 forms?
Zonula adherens and desmosomes
What proteins are hemidesomosomes made of and what is their prupose?
- Attach cells to the basal lamina
What are gap junctions composed of and what is their function?
- Allow passage of small molecules from one cell to another for communication
3 types of apical structures we see on the epithelial cells? What are there functions?
- Microvilli - increase SA for absorbtion
- Stereocillia - elongated microvillia with mechanosensory function (inner ear)
- Cilia - larger projection with core of microtubules, propels material along the epithelial surface
Stratified squamous epithelia of the epidermis serve what function?
protect underlying tissues from water loss and microbial invasion
cells of the stratified squamous epithelia move gradually from What layer to what layer? They fill with what on the way?
- basal to surface layer
Describe pseudo stratified epithelia
appear to be thick and have several cell layers, all cells attach to the basal lamina but not all extend to the epithelia surface
Transitional epithelium or urothelium is found where? Describe it? What is its function
- lining of the urinary system
- Large rounded surface cells
- protective against urine
Glands are composed of?
Exocrine glands have?
Ducts for carrying secretions
Endocrine glands are often surrounded by what? Why?
- Capillary bed or blood vessels
- No duct system so easiest way to distribute product to body
Describe the 3 types of secretion
- Merocrine - exocytosis
- Holocrine - terminally differentiated cells explode basically
- apocrine - apical product filled areas of cells are extruded
exocrine gland sproducing mucus or similar individual cells are called what
- Mucous glands
- Goblet cells
What is a serous gland? what colour does it stain mostly?
- Produces mainly proteins and enzymes
What are the surfaces of the cell that ajoin to the cell next to it
What are the 3 components of the basal lamina
- type 4 collagen
- entactin and periecan hold them together
We see a 9 + 2 assembly in what apical surface structure?
While stratified squamous keratinized epithelium lines the epidermis of the skin what lines wet cavities?
Stratified squamous nonkeratinized epithelium
WHat type of gland are salivary glands? Serous or mucous?