Epithelial Tissue Flashcards
What is the general structure of epithelial tissues?
- 1 layer or more of tightly packed cells, with exposed apical surface and cells attached to the basal membrane (like a carpet)
What is the general function of epithelial cells?
- lines surfaces to protect
- forms glands to secrete
What are the 4 characteristics of E tissue?
1) cells have polarity
2) layers of tightly packed cells bound together by cell junctions
3) avascular
4) high rate of cell division to replace lost/damaged cells
What are the characteristics of E cells?
- apical surface is exposed
- unequal distribution of organelles
- basal surface anchored to underlying connective tissues
Why can skin shed off?
- the apical skin has older dead cells which can be rubbed off
Why doesn’t skin come off when pulled?
-basal surface of skin Is connected to underlying tissue
What is underneath the basal surface?
-protein filaments made by epithelial tissue and underlying connective tissue
What are tight junctions?
- interlocking membrane proteins fuse adjacent cell membranes
- prevents molecules moving between cells
eg. need acidity from eating away at stomach and other tissues
What are desmosomes?
- transmembrane proteins reinforced by cytoskeleton
- strong connections resists stretching, twisting
eg. when you burn the top of your mouth –> skin comes off in “sheets”
What are gap junctions?
- channel proteins (connexions) connect cells
- allows for exchange of small molecules, ions
eg. to coordinate cilia beating upward trachea to keep things out of lungs
What does avascular mean?
- no blood vessels present –> never any capillaries or. veins in tissue itself
- exchange of nutrients, waste by diffusion
Why is it important for E tissue to have high rates of cell division? Why is this a downfall?
eg. why your skin cells can rejuvenate
- bad because chemotherapy targets cancerous cells that are dividing quickly but will also kills healthy E cells also travelling quickly
What is the structure of simple squamous epithelial tissue?
-one layer of flat cells = thin and fragile
What is the function of simple squamous E tissue?
-lines protected areas that are not exposed to the outside world
Where are simple squamous E tissue found?
- mesothelium lines body cavities
- endothelium lines heart, blood vessels
- walls of alveoli and capillary for gas exchange
Why don’t you want bigger cells lining the blood vessels?
-they would take up too much space in the vessel and blood would not be able to get through well
What is the structure of simple cuboidal E tissue?
- one layer of cube-shaped cells
- a bit more cytoplasm with spherical nucleus inside the cell
What is the function of simple cuboidal E tissue?
-limited protection with more cytoplasm for secretion and absorption
Where are simple cuboidal E tissue located?
-lines kidney tubules, pancreatic ducts, salivary glands, forms glands
What is the structure of simple columnar E tissue?
- one layer of tall rectangular cells
- lots of cytoplasm with elongated nuclei neat basal surface
What is the function of simple columnar E tissue?
- limited protection
- lots of cytoplasm for lots of secretion, absorption
Where is simple columnar tissue found?
-forms glands, lines stomach, and intestines
What is the structure of stratified squamous tissue?
-many layers of cells, apical layer appears flat
What is the function of stratified squamous tissue?
-protects against abrasion, chemicals, pathogens
What is the structure, function, and location of keratinized stratified squamous epithelium?
(killed)
Struc: apical layers of cells are packed with keratin protein
Func: prevents water loss
Loc: skin
What is the structure, function, and location of non-keratinized stratified squamous epithelium?
(not killed)
Struc: no keratin protein so they will dry out, must keep moist
Loc: lines oral cavities, vagina, anus, pharynx, esophagus
What is the structure of stratified cuboidal E tissue?
-several layers (usually two), apical layer appears cuboidal)
What is the function of stratified cuboidal?
-protection and secretion
Where are stratified cuboidal tissues found?
-they are rare; forms ducts of sweat, mammary glands
What is the structure of stratified columnar?
-several layers of cells, apical layer appears columnar
What is the function of stratified columnar?
-protection and secretion
Where are stratified columnar E tissues found?
-rare; lines pharynx, vas defends, urethra
What is the structure of pseudo stratified ciliated columnar?
- cells vary in size
- position of nucleus varies therefore cells look layered
- but all cells contact basement membrane
What is the function of pseudo stratified ciliated columnar?
-protects, secretes, moves material along passageway
Where are pseudo-stratified ciliated columnar tissues found?
-lines nasal cavity, trachea, bronchi, ovarian tubes
What is the structure of transitional epithelium?
- cells may be crowded into many layers –> looks stratified cuboidal
- cells mat be stretched flat –> looks like simple squamous
What is the function of transitional E?
-tolerates stretching, recoil
What is the location of E?
-empty vs. full bladder
