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Flashcards in Intestines Deck (66):
1

What are the 3 anatomical features that increased the surface area of the small intestines?

-Circular folds
-Villi (mucosa & submucosa)
-Microvilli (intestinal cells)

2

What comprises the brush border of the intestines?

Enterocytes + Microvilli

3

What happens if there is ischemia to the villi of the intestines?

Loss of brush border = lower absorptive capacity

4

What are the five cell types in the surface epithelium?

1. Absorptive enterocytes
2. Goblet cells
3. Secretory enterocytes
4. Endocrine cells
5. Stem cells

5

Why are there stem cells in the small intestinal cells?

Rapid turnover

6

What is the function of Brunner's glands?

Secrete mucus and HCO3

7

What is the function of the secretory enterocytes?

Help facilitate absorption by secreting H2O and electrolytes

"undisturbed water layer"

8

What are the cells in the crypts of Lieberkuhn?

Goblet

Secretory Enterocytes

Absorptive enterocytes

9

What is the function of the absorptive enterocytes?

Expresses a variety of enzymes that facilitate digestion

10

What are the primary regulators of small intestine motility, and do they stimulate of inhibit contractions?

1. Ach (stim)
2. VIP (inhibit)
3. NO (inhibit)

11

What are the three types of intestinal motility?

1. Migrating motor complex
2. Segmental contractions
3. Peristaltic contractions

12

What does distension in the small intestine trigger? What is the function of this?

Local and **distal** peristaltic relayed by a series of reflexes

Function = get things downstream moving

13

What is the stimulus for gastroenteric and gastroileal reflexes?

Distention

14

What regulates emptying of the intestines into the cecum?

Distension of the cecum inhibits relaxation of the sphincter, but distention in the ileum stimulates

15

What mediates the ileocecal sphincter reflex?

Inhibition is mediated through the ENS

16

What causes the haustra of the large intestine?

Organization of the smooth muscle (circular muscles and tenia coli)

17

Why is the smooth muscles organized as it is in the large intestines?

Facilitates mixing of fluids (and thus absorption)

18

Are there villi in the large intestines?

Nope

19

What are the primary sites of nutrient absorption in the large intestines?

Crypts

20

What are the three positive regulators of the Crypts of Lieberkuhn?

Mechanical
PNS
ENS

21

What is the negative regulator of the crypts of Lieberkun?

symp innervation

22

What happens to the Haustra during intestinal smooth muscle contraction? What is the function of this?

Become more prominent

Increases mixing

23

What is the function of symp stimulation in the distal colon?

Relaxas portions of the colon distal to the distension

24

What are the propulsive movements of the large intestines?

Mass peristalsis moves contents toward rectum 3 times /day

25

Where is the coloncolonic reflex initiated?

Where there is distension

26

Distention in what two places along the GI tract will induce mass movement?

Stomach and duodenum

(gastrocolic and duodenocolic reflexes)

27

What are the four key features to the defecation reflex?

1. Intrinsic reflex
2. Parasympathetic reflex
3. Additional afferent signals
4. Desired defecation

28

What is the intrinsic reflex of defecation? What division of the ANS is this initiated by?

Distention in the distal portions of the colon produces peristaltic wave toward the rectum. **This is initiated by the ENS.**

29

What causes the internal anal sphincter to relax?

ENS activity from distension leads to release of NO and VIP

30

What happens to the signal to contract in the external sphincter before defectation?

Increases

31

How strong is the ENS signals in the rectum for the defecation reflex?

Weak--parasymps more important

32

What is the effect of the PNS in the defecation reflex?

Signals from the rectum are relayed to the spinal cord, and back to the descending colon, forcing feces toward the anus

33

What is the role of the additional afferent signals from the rectum to the spinal cord in the defecation response?

Initiates a deep breath, closure of the glottis, and contraction of the abdominal wall to push fecal content downard

34

What happens to the pelvic floor during defecation?

Relaxes

35

What happens during the desired defecation stage of the reflex?

Conscious relaxation of the external sphincter, and evacuation of the feces

36

Which has folds: small or large intestines?

Both

37

Which has villi: small or large intestines?

Small

38

Which has microvilli: small or large intestines?

Both

39

Which has crypts/glands: small or large intestines?

Both

40

Which has nutrient absorption: small or large intestines?

Small

41

Which has water/electrolyte absorption: small or large intestines?

Both

42

What happens to the number of bacteria as you move from the stomach through the intestines?

Increases

43

What are the four factors that change the growth of gastrointestinal bacteria?

1. GI secretions
2. Mucosal immunity
3. Intestinal motility
4. Pharm agents

44

What are the five functions of intestinal bacteria?

1. Conversion or primary bile to secondary bile
2. Deconjugation of compounds conjugated in the liver
3. Nutrient salvage
4. Detox
5. Suppression of pathogens

45

What happens to the effectiveness of oral contraceptives with abx use?

Decreases b/c rely on bacteria to break down estrogen

46

What increases the secretions of the Brunner's glands and the crypt of Lieberkuhn?

Chyme
ENS
CCK
Secretin

47

What decrease the secretions of Brunner's and crypts of Lieberkuhn?

sympathetics

48

Which muscles of the large intestines are tonically contracted: the longitudinal or the circular?

Circular

49

What is the function of the absorptive enterocytes in the large intestines?

Absorb H2O and electrolytes

50

What causes relaxation in the large intestines, as opposed to NO in the rest of the GI tract?

Symp stimulation

51

Goblet and absorptive enterocytes are located primarily (where?); while secretory enterocytes, endocrine cells, and stem cells are (where)?

Goblet and absorptive enterocytes = villi

Secretory enterocytes, endocrine cells, and stem cells= crypts

52

Segmental contractions of the intestines are important for what and are induced by what?

Important for mixing, and induced by distention

53

What type of contractions are utilized to push intestinal contents toward the anus?

Peristaltic

54

What causes the mixing movements in the large intestines?

Circular muscle contraction, resulting in bulging of the intestinal wall

55

What initiates the propulsive movements of the large intestines? How often do these occur?

These mass movements are initiated by a constriction point, causing a large portion of the intestines to contract.

56

What is the intrinsic portion of the defecation reflex?

Distension in the distal colon signals nerves to start peristaltic contraction, forcing fecal matter toward the anus

57

What is the parasympathetic defecation reflex?

After the intrinsic reflex, parasymp nerves to spinal cord cause mass peristalsis, and forcing feces against the anus

58

What is irritable bowel syndrome?

an idiopathic chronic relapsing disorder characterized by abdominal discomfort (pain, bloating, distension, or cramps) in association with alterations in bowel habits (diarrhea, constipation, or both).”

59

What is the treatment for IBS?

Exercise and symptomatic relief

60

What are the two types of inflammatory bowel disease?

Ulcerative colitis
Crohn's disease

61

Which part of the GI tract is Crohn's disease usually associated with?

ileum

62

Skip lesions = ?

Crohn's disease

63

What is the site of origin of the inflammation in crohn's disease?

Submucosa

64

Where does the inflammation of ulcerative colitis originate from?

Crypts of lieberkuhn

65

What are the complications of IBD? (2)

Arthritis
Vit deficiencies

66

What is Hirschsprung's disease?

Congential Agangiolinc colon