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Flashcards in ToB - Epithelia Deck (19)
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What are epithelia?

Sheets of contiguous cells of varied embryonic origin, that cover the external surfaces of the body and line the internal surfaces.


What epithelia does the ectoderm produce?

That of the skin and cornea.


What epithelia does the mesoderm produce?

Urogenital tract, blood and lymph vessels and pleural/peritoneal/pericardial sac lining.


What epithelia does the endoderm give?

The GI tract, respiratory tract, liver and most glands.


Where is the basal membrane found?

It lies between the layer of epithelial cells and the connective tissue.


What is the structure of the basal membrane?

Thin, flexible and acellular, consisting of the basal lamina laid down by the epithelial cells themselves.
It's thickness can be increased by reticular fibrils elaborated by the connective tissue.


What is the function of the basement membrane?

Serves as a cellular/molecular filter.
It is a strong layer for epithelia to adhere to.


What is the location and function of simple squamous epithelia?

Location - lining capillaries, alveoli and body cavities.

Function - thin for gas exchange, lubrication (secretes fluid).


What is the location and function of simple cuboidal epithelia?

Location - surface of ovary, small ducts of exocrine glands.

Function - secretion and absorption (coupled to synthesise hormone), protection and conduit.


What is the location and function of simple columnar epithelia?

Location - ductuli efferentes of testis, uterus, oviducts, GI tract

Function - Absorption, secretion, lubrication.


What is the location and function of pseudostratified epithelia?

Location - resp tract above trachea, lacrimal sac.

Function - secretion, conduit, absorption.


What is the location and function of non keratinised stratified squamous epithelia?

Location - vagina, larynx, oesophagus, cornea

Function - reduce water loss, protection.


What is the location and function of keratinised stratified squamous epithelia?

Location - skin surface, a little in oral cavity.

Function - protection, reduce water loss, prevent ingress of microbes.


What is the location and function of transitional epithelia?

Location - bladder and rest of urinary tract

Function - distensibility, protection.


What is the location of stratified cuboidal epithelia and stratified columnar?

Location of cuboidal - lining ducts of sweat glands

Location of columnar - conjunctiva of eye


How do epithelial cells renew?

Turnover depends on cell function and location but it still occurs at a constant rate.

Some epithelia aren't renewed but proliferate instead to replace damaged/lost cells.


What are microvilli and where are they found?

Apical extensions of the s.a. that increase absorption, mostly on simple columnar cells of the small intestine.


What are stereocilia and where are they found?

They are very long microvilli, found on the surface of the ductus deferens and epididymis.


What are cillia and where are they found?

They rise from a centriole in a 9+2 configuration, containing micro tubules with ATPase to allow them to beat in coordinated waves.
They are found in the trachea and Fallopian tubes.