Lecture 31 - GI pt 2 Flashcards Preview

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Flashcards in Lecture 31 - GI pt 2 Deck (31):
1

function of SI

digestion and absorption of all nutrients

2

key structural features of SI

highly adapted to max surface area
- very long (15-18 ft)
-folds of mucosa/submucosa
-mucosa has fingerlike projections (villi)
-epithelial cells have microvilli
SA is DOUBLE A TENNIS COURT WOOOW

3

villi

fingerlike projections, site of absorption of nutrients and fluids
*lamina propria rich in blood vessels, nerves, lymphatics
-central core in lamina propria contains fibers of muscularis mucosae and a central lacteal

4

crypts

invagination continuous with villi, site of SECRETION, stem cells located near base of crypt; cells mature and differentiate as they migrate up the crypt.

5

paneth cells

only in SI, only at base of crypt. right next to stem cells -- provides protection so that stem cell portion of small bowel is protected

6

lamina propria has

veins, arteries, and lymphatic channel (lacteal)

7

lacteals

things from outside world dont have to work hard to get in here

8

Columnar (absorptive) cells

-also known as enterocytes
-tall, eosinophilic cells with basal nuclei
-numerous microvilli on apical surface (~3,000 per cell)
microvilli form a striated border (“brush border”) covered by a glycocalyx

9

Subcellular Features of Enterocytes:

1) microvilli: each microvillus has a core of actin filaments
2) junctional complexes: attachment to adjacent enterocytes prevents direct access of luminal contents into inter-cellular spaces
3) intercellular clefts: space between cells; at base of cells
4) numerous mitochondria and vesicles

10

where does fat first go

intercellular cleft into chylomichrons into lymphatics

11

where are goblet cells found

in SI and colon - through villus but mostly crypt
mucous cells in other places have a different name

12

paneth cells

almost only in SI
pyramidal cells confined to base of crypt
bright pink (eosinophilic) granules in cytoplasm
secrete lysozyme, defensins (anti-bacterial)
important for protecting stem cell compartment

13

Enteroendocrine cells

in SI
Pyramidal, pale cells sparsely distributed in crypts
Secrete several hormones (secretin, CCK, somatostatin, enteroglucagon, peptide YY, etc…)

14

stem cells found

at base of cryot

15

duodenum main function

neutralizes acidic chyme that exits the stomach

16

brunner's glands

unique to duodenum
located in submucosa
cells contain alkaline mucus with basal nuclei

17

where are most minerals absorbed

duodenum

18

jejenum function

responsible for absorption of most nutrients (proteins, carbohydrates, lipids, vitamins)

19

ileum function

-absorption of many nutrients
-distal main site of absorption of vitamin B12 and bile acids
-Peyer’s patches are prominent (lymphoid aggregates)

20

peyers patches

lymphoid aggregate, prominent in ileum

21

bands of muscle in colon

tinae coli

22

function of colon

-Absorption of water (solidify stool; prevent dehydration)
-Propulsion of feces

23

structural features of colon

Mucosa: flat (crypts only; no villi); mostly goblet cells
Muscularis propria: thick; outer layer arranged as three longitudinal bands called “tenia coli”

24

colon cell types

goblet, columnar (absorptive), enteroendocrine, paneth, stem cells at base of crypts

25

goblet cells in colon

most prominent
-round, clear cytoplasm containing mucus; basal nuclei
-mucus serves as cytoprotection, lubrication

26

columnar cells in colon

similar to small intestine enterocytes but less numerous; poorly developed brush border
absorb water and electrolytes

27

Enteroendocrine cells in colon

Rare in colon (mainly cecum and rectum); neurosecretory granules

28

paneth cells in colon

Rare in colon; mainly cecum and ascending colon

29

what controls continence

anal canal

30

anal canal structural features

Mucosa: stratified squamous epithelium
Sphincter mechanism

31

sphincter mechanism of anal canal

Internal anal sphincter: smooth muscle (involuntary control)
External anal sphincter: skeletal muscle (voluntary control)