Intestinal epithelial cells

Question 1

list types of intestinal epithelial cells (8)

Answer 1

• undifferentiated crypt cells (stem cells)
• goblet cells
• enteroendocrine cells
• paneth cells
• gobular leukocytes
• m (microfold) cells
• intraepithelial lymphocytes
• intestinal absorptive cells/enterocytes

Question 2

undifferentiated crypt cells (stem cells)

Answer 2

• basal portion of gland

- divide to give rise to other types of epithelial cells

Question 3

goblet cells

Answer 3

• secrete mucin
• increase in numbers caudally in intestine
• type of mucin varies with location

Question 4

enteroendocrine cells

Answer 4

• scattered singly throughout surface and glandular epithelium
• hormonal regulation of GI functions

Question 5

paneth cells

Answer 5

• only in base of gland
• apical membrane bound granules (lysozyme, defensins, peptidase)
• control microflora

Question 6

globular leukocytes

Answer 6

• large eosinophilic globules (granules)
• small heterochromatic nucleus
• intraepithelial and in lamina propria

Question 7

m cells

Answer 7

• located over lymphatic areas or nodules
• blunt microvilli or ridges
• take up antigens by endocytosis and pass to lymphocytes in invaginations of cell membrane
• lymphocytes migrate to initiate immune response

Question 8

intraepithelial lymphocytes

Answer 8

common throughout small and large intestine

Question 9

intestinal absorptive cells/enterocytes

Answer 9

• numerous on surface of villi in SI, luminal surface of LI, glands of both
• columnar with microvilli
• apical tight junctions
• basal nucleus and RER, SER and golgi, mitochondria

Question 10

functions of intestinal enterocyte

Answer 10

• active uptake of small molecules (transport epithelium)
• resynthesis of triglycerides from fatty acids
• neonates: uptake of IgG
• protease resistant IgAs to fight pathogens

Question 11

secretions of enterocytes (3)

Answer 11

• enzymes secreted to glycocalyx for digestion of proteins/carbs
• active movement of ions
• chylomicrons released at lateral membrane by exocytosis

Question 12

innervation of digestive tract (3)

Answer 12

• intramural nerve plexus
• intrinsic interneurons
• extrinsic innervation

Question 13

intramural nerve plexuses

Answer 13

• coordinate activity of GI tract

- fibers innervate smooth muscle and epithelial cells

Question 14

what do intramural nerve plexuses contain (3)

Answer 14

• parasympathetic terminal ganglia and fibers
• sympathetic fibers
• sensory fibers

Question 15

intrinsic interneurons

Answer 15

• entirely within plexus
• coordinate different segments of gut and different layers of the wall
• must be intact for peristalsis
• enteric division of parasympathetic NS

Question 16

2 components of intrinsic interneurons

Answer 16

• submucosal plexus (t submucosa)

- myenteric plexys (t muscularis)

Question 17

extrinsic innervation

Answer 17

• parasympathetic stimulates smooth muscle

- sympathetic depresses smooth muscle

Question 18

functions of large intestine (3)

Answer 18

• microbial action
• absorption/secretion of H2O/electrolytes, secretion of mucus, absorption of fermentation products
• forms fecal mass

Question 19

t mucosa of large intestine

Answer 19

• some longitudinal folds
• no villi
• deep mucosal glands that open into luminal surface
• goblet cells, enterocytes, enteroendocrine cells
• l propria has free cells and lymphatic nodules
• large venous plexuses in rectum

Question 20

t submucosa, t muscularis, t serosa of large intestine

Answer 20

• submucosa: may accumulate fat
• muscularis: outer longitudinal layer forms bands, many elastic fibers
• serosa: most of LI except rectum (adventitia)

Question 21

longitudinal mucosal folds in rectum of ruminants

Answer 21

rectal columns

Question 22

solitary lymphatic nodules with epithelial depressions over them in dogs

Answer 22

rectal pits

Question 23

anorectal line

Answer 23

marks separation between rectum and anal canal –> epithelium changes from simple columnar to stratified squamous

Question 24

anal canal

Answer 24

short terminal segment of digestive tract –> lined by stratified squamous epithelium –> terminates at the anus

Question 25

anal columns

Answer 25

longitudinal folds which alternate with sinuses --> continuous with rectal columns and sinuses in ruminants, not present in horse

Question 26

anocutaneous line

Answer 26

point at which stratified squamous epithelium becomes keratinized --> mucocutaneous junction

Question 27

external/internal anal sphincter

Answer 27

- external: skeletal muscle | - internal: smooth muscle

Question 28

anal sacs/perianal sinuses

Answer 28

- either side of anal canal between sphincters - ducts open into anal canal at anocutaneous line - stratified squamous epithelium

Question 29

anal glands

Answer 29

- modified tubular sudoriferous glands - t submucosa or t muscularis - coiled tubular gland morphology

Question 30

perisaccular glands

Answer 30

- secrete into neck of anal sac or directly into duct | - coiled tubules

Question 31

glands of perianal zone (2+)

Answer 31

- tubular sudoriferous | - circumanal (superficial and deep)

Question 32

circumanal glands

Answer 32

- superficial: large sebaceous glands (hair) | - deep: hepatoid (liver-like) -->deep to sebaceous glands, no ducts

Question 33

gall bladder

Answer 33

- stores and concentrates bile, resorbs Na and water - thin folded wall, highly dispensible - tall columnar cells with microvilli folded into crypts - no muscularis mucosa - may have glands - circular t muscularis - may have goblet cells

Question 34

bile ducts

Answer 34

- connect liver lobes with gall bladder and duodenum - structure similar to gall bladder - t muscularis may be discontinuous