Epithelia

Question 0

What epithelia are derived from ectoderm?

Answer 0

Epidermis, corneal epithelium.

Question 1

Define epithelia

Answer 1

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

Question 2

What epithelia are derived from mesoderm?

Answer 2

Epithelium of urogenital tract.
Endothelium of blood and lymphatic vessels.
Pericardial and pleural dad lining.
Peritoneal lining.

Question 3

What epithelia are derived from endoderm?

Answer 3

Epithelial lining of GI tract.
Epithelial lining of respiratory tract.
Many glands - thymus, salivary, thyroid.
Epithelium of liver.

Question 4

What is basement membrane?

Answer 4

Thin acellular layer, lies between epithelia and subtending connective tissue.
Consists of a basal lamina laid down by epithelial cells - type four collagen and laminin
And lamina reticularis - type three collagen - elaborated by connective tissue

Question 5

What is the function of the basement membrane?

Answer 5

Cellular and molecular filter.

Surface for cells to adhere to.

Question 6

What implication does penetration of the basement membrane by malignant cells have?

Answer 6

Highly relevant to prognosis.

Question 7

Where might simple squamous epithelia be found?

Answer 7

Glomerulus; arteriole, venule, lymphatics, capillaries (endothelium); lining pericardium, peritoneum, pleural sac (mesothelium); alveoli; loop of henle; inner and middle ear.

Question 8

What are the functions is simple squamous epithelia?

Answer 8

Lubrication - pleural sac, pericardium, peritoneum.
Gas exchange
Barrier
Active transport - mesothelium and endothelium. (Pinocytosis)

Question 9

Where is simple cuboidal epithelia found?

Answer 9

Collecting ducts in kidney.
Thyroid follicles
Ducts of many exocrine glands (pancreas)
Surface of ovary (germinal epithelium)

Question 10

What is the function of the epithelium covering the ovary?

Answer 10

Barrier and covering.

Question 11

What is the function of the epithelia in the thyroid?

Answer 11

Hormone secretion, storage and mobilisation.

Question 12

What is the function of the epithelia in the kidney tubules?

Answer 12

Absorption and secretion.

Question 13

What is the function of epithelia in the ducts of exocrine glands?

Answer 13

Absorption and conduit.

Question 14

Where is simple columnar epithelium found?

Answer 14

Lining the crypts of Lieberkuhn, small intestine and colon.
Lining of stomach and gastric glands.
Lining the gall bladder
Striated duct of parotid gland
Fallopian tube - some cells ciliated, and uterus.
Large ducts of exocrine glands including striated duct of parotid gland.
Ductuli efferentes of testes.

Question 15

What is the function of the simple columnar epithelium in the gall bladder?

Answer 15

Removes water and electrolytes, reduces volume of bile.

Question 16

What is a striated duct?

Answer 16

Characterised by infoldings of basal membrane - basal portion of each cell is striated.

Question 17

What makes saliva hypotonic?

Answer 17

Removal of sodium ions

Question 18

What is the zonula occludens?

Answer 18

Two adjacent plasma membranes bound tightly together by occludin.

Question 19

What is the function of the zonula occludens?

Answer 19

Segregation of membrane proteins to apical/lateral/basal surface.
Separate lumen and intercellular space - control the movement of fluid across the epithelium.

Question 20

What can disrupt the zonula occludens?

Answer 20

Cholera toxins.

Question 21

What connective tissue is found in the villi of the small intestine?

Answer 21

Lamina propria.

Question 22

What is a lacteal?

Answer 22

Dilated lymphatic vessel.

Question 23

What is the function of the simple columnar epithelium in the small intestine and colon?

Answer 23

Absorption, secretion, lubrication.

Question 24

What is the function of the simple columnar epithelium in the gall bladder?

Answer 24

Absorption

Question 25

What is the function of the simple columnar epithelium in the stomach and gastric glands?

Answer 25

Secretion

Question 26

What is the function of the simple columnar epithelium in the fallopian tube?

Answer 26

Transport of oocyte (ciliated)

Question 27

Where is pseudostratified epithelium found?

Answer 27

``` Upper respiratory tract - nasal cavity, trachea, bronchi. Epididymis and ductus deferens. Lacrimal sac. Large excretory ducts. Auditory tube and tympanic cavity. ```

Question 28

What cells are present in the epididymis?

Answer 28

Basal cells - stem cells. Proncipal cells - absorb fluid, and secrete substances that promote sperm maturation, phagocytose degenerate sperm and residual bodies.

Question 29

What cell surface modifications are present in the pseudostratified epithelium of the epididymis?

Answer 29

Stereocilia

Question 30

What happens to sperm as they pass through epididymis?

Answer 30

Sperm mature and acquire motility

Question 31

How long is the epididymis?

Answer 31

4-6m - highly coiled!

Question 32

What cell surface modifications are found in the pseudostratified epithelium of the respiratory tract?

Answer 32

Cilia

Question 33

What specialised cells are found in the pseudostratified epithelium f the upper respiratory tract? What is their function?

Answer 33

Goblet cells - secrete mucous.

Question 34

What frequency do the cilia beat at?

Answer 34

12hZ

Question 35

Where is stratified squamous epithelium found?

Answer 35

Vagina, oral cavity, oesophagus, larynx, part of anal canal, surface of cornea, inner surface of eyelid.

Question 36

What is the function of stratified squamous non keratinised epithelium?

Answer 36

Protection. | Reduces water loss but remains moist.

Question 37

How does the vagina maintain a low pH?

Answer 37

Cells are rich in glycogen which is a substrate for lactobacilli, which produce lactate.

Question 38

What happens to the epithelial cells of the vagina in the absence of hormonal stimulation - pre puberty and post menopausal?

Answer 38

Atrophy.

Question 39

Where is stratified squamous keratinised epithelium found?

Answer 39

Skin. | Limited distribution in oral cavity.

Question 40

What is the function of stratified squamous keratinised epithelium?

Answer 40

Protect against UV, abrasion. Prevents water loss. Physical barrier to microbes.

Question 41

Where is transitional epithelium found?

Answer 41

Bladder, ureters, urethra, renal calyces.

Question 42

What is the function of transitional epithelium?

Answer 42

Protect underlying tissues from toxins. | Distends.

Question 43

What is the time from cell division to being sloughed off for a cell in the epidermis?

Answer 43

28 days.

Question 44

What is the time from cell division to being sloughed off for a cell in the small intestine?

Answer 44

4-6 days.

Question 45

What is the function of microvilli?

Answer 45

Increase cell surface area for diffusion/active transport.