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Flashcards in Lower GI Normal Structure/Function Deck (42):
1

What are the 3 divisions of the small intestine?

duodenum
jejunum
ileum

2

What is the function of the small intestine?

digest food and absorb end products

3

What are the plicae circulares?

permanent mucosal folds present in the duodenum, jejunum and proximal ileum that increase the surface area by 2-3X

4

What are the villi?

finger like projections of epithelium covered lamina propria that increase surface area by 10X

5

What are the microvilli?

extensions of the epithelial cell apical plasma membrane that increases surface area by 20X

6

What is contained within the villi lamina propria?

central lymphatic channel and capillaries
smooth muscle fibers, loose CT and lymphoid cells

7

What cell types are contained in the crypts of lieberkuhn?

DNES cells, stem cells, paneth cells

8

What cell types are contained in the SI epithelium?

enterocytes, goblet cells, DNES cells

9

What type of epithelium is in the SI?

columnar

10

What is the main function of the enterocyte?

terminal digestion and absorption of water and nutrients
-reesterify FAs into TGs, form chylomicrons, and transport the bulk of the absorbed nutrients into the lamina propria for distribution to the rest of the body

11

What does the glycocalyx coat over the microvilli do?

protect
involved in digestion of disaccharides and dipeptides into monomers for adsorption through peptide hydrolases andd disaccharidases that are abundant on the apical surface

12

What do goblet cells secrete? What does it's product do?

mucin
lubricates and protects the intestine

13

What does goblet cell mucin contain?

high MW glycoprotein macromolecules

14

What happens to mucin after it was released?

granules become hydrated and expand several hundred fold

15

What is located in the upper half of the crypt of lieberkuhn?

surface absorptive and goblet cells

16

What is located in the basal half of the crypt?

mostly stem cells, DNES cell and paneth cells

17

How often is small intestine epithelium replaced in humans?

every 3-6 days

18

What do paneth cells secrete?

lysozyme & defensins

19

What do defensins do?

neutralize bacterial and viral infections

20

What does shortening of the villi assist with?

emptying the lacteal

21

What is the extensive immune defense system in the form of lymphoid tissue?

GALT

22

What are Peyer's patches?

a coalescence of lymphoid nodules

23

What are brunner's glands?

alkaline mucus that neutralizes the pH of the gastric chyme and protects the duodenum, they also contain epidermal growth factor that may be involved in stem cell proliferation in the crypts

24

Which enteric plexus controls secretion?

submucosal (meissner's)

25

What does the auerbach's (myenteric) plexus control?

motor innervation to muscularis externa
secretomotor innervation to the mucosa

26

What are the two types of movements in the small intestine called?

mixing and propulsion

27

What are distinguishing features of the duodenum?

25cm
villi are broader, taller and more numerous per unit area
brunner's glands

28

What are disinguishing features of the jejunum?

villi are narrower, shorter and sparser
more goblet cells per unit area

29

What are distinguishing features of the ileum?

villi are sparsest, shortest and narrowest
peyer's patches

30

List the regions of the large intestine

cecum
appendix
colon (ascending, transverse, descending, sigmoid)
rectum
anus

31

What does the ileocecal valve do?

prevents reflux of cecal/colonic content back into the ileum

32

What is the surface of the colon like?

smooth, no villi
does have crypts of lieberkuhn

33

What cell type is missing from the colonic crypts that is present in the crypts of the small intestine?

paneth cells

34

What are the differences between small and large intestine crypts?

crypts n the colon are longer and more glandular with an abundance of goblet cells
both have stem cells at the base of the crypts

35

How often is the colonic mucosa replaced?

every 6-7 days

36

What is the taenia coli?

muscularis externa outer longitudinal muscle arranged in three distinct bands that remain partially contracted and cause the large intestine to be puckered in o haustra coli sacculations

37

What are the key features of the appendix?

masses of lymphoid tissues in the mucosa and submucosa
lymphoid tissues often forms follicles with germinal centers

38

What is the terminal 12 cm of the GI tract called?

the rectum

39

What is the rectal mucosa like?

similar to the colon except that the crypts are somewhat deeper and the goblet cells more abundant

40

What change occurs at the recto anal junction?

epithelium transitions from simple to columnar to stratified squamous
(crypts disappear just prior to this junction and are replaced by large circumanal glands

41

What are the two venous plexi found in the submucosa of the anal canal?

internal hemorrhoidal plexus
external hemorrhoidal plexus
*in older people and during pregnancy an increased in the size of the vessels in these plexuses can result in hemorrhoids

42

What is located at the end of the anus?

a ring of thickened smooth muscle called the anal sphincter and distal to this is a circular band of striated muscle called the external anal sphincter