lecture 17/18

Question 1

general plan of the GIT

Answer 1

• mucosa: epithelium, lamina propria, muscularis mucosa
• submucosa: loose or dense CT
• tunica muscularis: 2 sublayer (internal circular and external longitudinal) and 3 in stomach (internal middle)
• serosa (or adventitia)

Question 2

what special feature is found in the esophagus?

Answer 2

esophageal glands (mucous) in the submucosa

Question 3

function of the stomach

Answer 3

• add/produce acidic fluid (pH 2.0) to the ingested food to transform it into a viscou mass called chyme
• secrete intrinsic factor essential to absorb vitamin B12
• prodcue hormones (e.g. gastrin)

Question 4

what is the pit:gland ratio in the cardia, pyloric, and gastric stomach?

Answer 4

• cardia: 1:1
• pylori: 2:1
• gastric 1:3

Question 5

properties/function of the surface mucous cell

Answer 5

• carbohydrate-rich glycoproteins described as the visible mucous b/c of cloudy appearance
• it forms a thick viscous gel-like coat that adheres to the epithelial surface
• high bicarbonate concentration

Question 6

properties/functions of the mucous neck cell

Answer 6

mucous is more soluble (protection)

Question 7

properties of zymogenic cells

Answer 7

has zymogenic granules that conatin pepsinogen and lipase

Question 8

properties of argentaffin cell

Answer 8

granules that contain: gastrin, serotonin, histamine, VIP, glucagon, and somastotatin, which is released into the basememnt membrane (not on the outside)

Question 9

properties of parietal cell

Answer 9

• makes: intrinsic factor and vitamin B12
• is the root of many diseases such as pernicious anemia and atrophic gastritis

Question 10

what are the segments of the small intestine

Answer 10

duodenum, jejunum, ilieum

Question 11

function of the small intestine

Answer 11

• finish digestion of partially digested macromolecules from the stomach via mostly pancreatic enzymes
• terminal digestion occurs at the mucosal surface and the resulting AAs, monosaccharides, FAs, and monoglycerides are absorbed

Question 12

how do we differentiate the duodenum?

Answer 12

brunner’s glands in the submucosa

Question 13

how do we differentate the jejunum?

Answer 13

plicae circularis (invagination of the submucosa into the mucosa), which increase the surface area by about 3x

Question 14

what is the general plan of the small intestine mucosa

layers and cells

Answer 14

• villi: columnar cell with brush border (enterocyte), goblet cell, M cell (microfold cell)
• crypt: columnar cell with brush border (absorptive cell), goblet cell, enteroendocrine cell, paneth cell, stem cell
• lamina propria
• muscularis mucosa

Question 15

what are M cells?

Answer 15

gut associated lymphatic tissue: senses mucous, so when foreign material, sends signal to lymphocytes, which are recruited

Question 16

what do enteroendocrine cells do?

Answer 16

secrete cholecystokinin (CKK), which causes contraction of the gall bladder and pancreatic secretion

Question 17

what protein are present in the small intestine microvilli

Answer 17

• on the outside: glycoproteins, disaccharidases, dipeptidases, alkaline phosphatases, enterokinases (trypsinogen to trypsin)
• at the tip on the inside: dense matrix made of villin
• terminal web, below microvilli: actin and myosin, with actin projecting to the villin

Question 18

what cell types are found in the large intestine?

Answer 18

• goblet cell
• absoprtive cell (enterocyte)
• entero-endocrine cell
• stem cell

Question 19

location and role of paneth cells

Answer 19

bottom of crypts in small intestine and have digestive enzymes and also regulate gut microbiome