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Physio II > Exam 4- Small and Large Intestines > Flashcards

Exam 4- Small and Large Intestines Flashcards

1
Q

What 3 things increase the surface area of the small intestines?

A

Folds of mucosa (Kerckring’s folds), villi on the folds, microvilli on the apical surface of the enterocytes (brush border)

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2
Q

What structures exist between individual villi in the small intestine and produce mucus and other secretions?

A

Crypts of Lieberkuhn

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3
Q

Where are new enterocytes produced from stem cells?

A

Crypts of Lieberkuhn

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4
Q

What is a lacteal within a villi? What is its function?

A

Extension of lymph system used to help with digestion (chylomicron from intestines to lacteal)

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5
Q

Basal electrical rhythym is dependent on location within GI tract. Where is it the fastest and where is it the slowest?

A

Fastest by duodenum and slowest towards end of GI tract (12-9 rhythms/min)

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6
Q

What are the two types of movement within the small intestines?

A

Segmentation and peristalsis

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7
Q

What is the action of segmentation in the small intestintes?

A

Mixes chyme w/ juices and exposed it to mucosa

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8
Q

What is the action of peristalsis in the small intestines?

A

Peristaltic reflex initiated by distention of intestinal lumen and mediated by myenteric plexus, propels chyme towards colon

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9
Q

What are simultaneous contractions of sections of circular muscle that divides the intestine into small segments?

A

Rhythmic segmentation

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10
Q

What causes circular muscle relaxation in front of the bolus during perstalsis? (2)

A

VIP, NO

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11
Q

What causes circular muscle contraction behind the bolus during peristalsis? (1)

A

ACh

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12
Q

PNS preganglionic fibers synapse on neurons where?

A

Within the enteric NS

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13
Q

Sympathetic postganlionic fibers synapse on neurons where?

A

myenteric plexus

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14
Q

Where does vagal stimulation generally elicit contractions?

A

Intestines

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15
Q

Where does sympathetic stimulation inhibit intestinal contractions?

A

Nonsphincteric sites

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16
Q

What intestinal reflex will inhibit gastric emptying due to an increase in H concentratio of duodenal chyme?

A

Enterogastric

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17
Q

What intestinal reflex will increase ileal motility in reponse to gastric secretion and motility (via gastrin & PNS)?

A

Gastroileal (keeps material moving towards rectum)

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18
Q

Distention of the ileum relaxing the ileocecal sphincter occurs via what intestinal reflex?

A

Ileocecal

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19
Q

Distenal of the stomach increasing colonic motility occurs via what intestinal reflex?

A

Gastrocolic

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20
Q

What intestinal neurohumoral agents will increase motility? (4)

A

ACh, gastrin, CCK, motilin

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21
Q

What neurohumoral factors decrease intestinal motility? (5)

A

NE, somatostatin, secretin, VIP, gastric inhibitory polypeptide

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22
Q

How much intestinal juice is secreted by the small intestine per day?

A

1.5-2 L

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23
Q

What 2 structures secrete mucus in the small intestine?

A

Submucosal glands of Lieberkuhn and goblet cells

24
Q

Intestinal secretions are under control of local neural reflexes and triggered by what? (4)

A

Entry of chyme into intestine, secretin, CCK, ACh

25
Q

What is the role of enterokinase in the small intestine?

A

Affects ability to digest protein (peptidase that converts tripsinogen into tripsin > activates inactive pro-proteases released from pancreas)

26
Q

What are the 3 conspicuous bands of muscle that separate the longitudinal muscles of the large intestines?

A

Taeniae coli

27
Q

What type of muscle forms the internal and external anal sphincter?

A

Internal = circular, external = striated

28
Q

What are the pockets formed by the wall of the colon?

A

Haustra

29
Q

What portion of the large intestine is composed of lymphoid tissue and hosues lymphocytes?

A

Appendix

30
Q

Are villi present on the mucosa of the colon?

A

No (little absorption and no secretion of enzymes)

31
Q

How is the mucosa layer in the large intestines different from the small intestines? (3)

A

Mucosa is thicker, crypts are deeper w/ more goblet cells, mucus provides lubrication and protection form irritating gases and acids from bacteria

32
Q

What is the function of the ileocecal valve?

A

Prevent backflow and bacterial contamination

33
Q

What portion of the intestines does not transport glucose or amino acids?

A

Colon

34
Q

What are the main functions of the colon? (2)

A

Absorption of water and electrolytes (most Na from chyme is reabsorbed), stoarge of fecal matter until explusion

35
Q

Of the 500mL of chyme entering the colon per day, how much is absorbed and how much is voided?

A

350mL absorbed and 150mL voided (100mL is water, remainder is solid)

36
Q

What is the oxygen status of the colon environment?

A

Anaerobic environment

37
Q

What are the byproducts of bacterial metabolism in the colon (5)

A

H2, N2, CO2, methane, and H2S gases

38
Q

What substances are synthesized in the colon? (2)

A

B complex vitamins and vit K

39
Q

The vagus nerve of the ANS (extrinsic NS) has an excitatory effect on what portions of the large intestines? (3)

A

Cecum, ascending and transverse colons

40
Q

The pelvic nerve of the ANS (extrinsic NS) has an excitatory effect on what portions of the large intestines? (3)

A

Descending colon, sigmoid colon, rectum

41
Q

The SNS (extrinsic NS) exhibits inhibitory effects via what 3 nerve complexes in the colon?

A

Superior and inferior mesenteric ganglia, hypogastric plexus

42
Q

Intrinsic regulation of the colon occurs via what plexus?

A

Enteric plexus

43
Q

Why is the “sluggish” colonic motility acceptable?

A

Very strong contractions are not necessary (but still engages in mixing and propulsive movements)

44
Q

What movement of the colon is very slow, mostly mixing, and aids in absorption of water and electrolytes?

A

Haustration

45
Q

What is the function of the haustration in the colon? (2)

A

Slow movement allows significant bacterial growth, aids in absorption of water and electrolytes

46
Q

What movement of the colon is stimulaed by the gastrocolic reflex, occurs 1-3x/day, and simultanelously contracts the ascending and trasnverse colons driving feces 1/3-3/4 the length of the colons (in a few seconds)?

A

Mass movements

47
Q

When is the gastrocolic reflex most evident?

A

After first meal of day (strong urge to defecate)

48
Q

What is defecation initated by?

A

Rectal filling by mass movement

49
Q

What 3 things occur when distension increases intraluminal rectal pressure great enough?

A

Active contraction of rectum, reflex relaxation of internal anal sphincter, constriction of external anal sphincter

50
Q

Contraction of what muscles will result in a valsalva maneuver and assist in the elmination of feces?

A

Abdominal muscles

51
Q

During defecation, what enhances contraction of descending and sigmoid colon and inhibits internal anal sphincter?

A

PNS pelvic nerves

52
Q

During defecation, what sphincter voluntarily relaxes?

A

External sphincter

53
Q

Arrival of the first bolus of fecal material causes what kind of increase in wall tension?

A

Passive (stretching of the rectum wall)

54
Q

How does the tone of the internal and external anal sphincters change during filling/ defecation?

A

Internal sphincter progressively decreased tone, external sphincter progressively increased tone

55
Q

Arrival of the second bolus of fecal material causes what kind of increase in wall tension?

A

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Physio II (14 decks)

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