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Physiology II > GI: Small & Large Intestines > Flashcards

GI: Small & Large Intestines Flashcards

1
Q

What three features of the small intestines increase surface area by 600x?

A

mucosal folds, villi, microvilli

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2
Q

What structure has the following characteristics?

  • site of new enterocyte production via stem cells
  • sit between individual villi
  • produce mucus and other secretions
A

crypts of lieberkuhn

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3
Q

Enterocyte microvilli are also called the…

A

brush border

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4
Q

What is the basal electrical rhythm from the duodenum to the ileum?

A

12 to 9/min

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5
Q

What are the two types of movement in the small intestine?

A

segmentation and peristalsis

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6
Q

This method of motility mixes chyme with juices and exposes it to mucosa…

A

segmentation

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7
Q

This method of intestinal motility is reflex initiated and moves chyme towards the colon…

A

peristalsis

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8
Q

The peristaltic reflex is initiated by ________ and mediated by_______

A

initiated by intestinal lumen distension

mediated by myenteric plexus

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9
Q

Rhythmic segmentation occurs via simultaneous contractions of …

A

segments of circular muscle

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10
Q

progressive contraction of successive sections of _______ is responsible for peristalsis in the small intestines

A

circular smooth muscle

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11
Q

In orthograde wave of relaxation/contraction, circular muscle ________ is relaxed while _______ is contracted

A

relaxed in front of bolus

contracted behind bolus

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12
Q

What mediates circular muscle relaxation in front of the bolus in orthograde wave?

A

VIP and NO

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13
Q

What mediates circular muscle contraction behind the bolus in orthograde wave?

A

ACh

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14
Q

This “housekeeping” process occurs with bursts of contractile activity separated by longer periods of quiescence q 75-90 min

A

Migrating motility complex

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15
Q

where does the migrating motility complex run in the GI?

A

stomach to ileum

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16
Q

The migrating motility complex is assoc. with increases in plasma _____

A

motilin

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17
Q

PNS preganglionic fibers synapse with ______ neurons

A

enteric nervous system neurons

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18
Q

SNS postganglionic fibers synapse with neurons of the _______

A

myenteric plexus

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19
Q

SNS stimulation of the myenteric plexus has what effect?

A

inhibit contraction

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20
Q

PNS/Vagal stimulation has what effect on the intestines?

A

stimulates contractions

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21
Q

The enterogastric intestinal reflex has what mechanism and effect?

A

increased H+ in duodenal chyme inhibits gastric emptying

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22
Q

The gastroileal intestinal reflex has what mechanism and effect?

A

Gastric secretion/motility increases ileal motility

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23
Q

What 2 effectors stimulate the gastroileal intestinal reflex?

A

gastrin and PNS

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24
Q

The ileocecal intestinal reflex has what mechanism and effect?

A

distension of ileum relaxes ileocecal sphincter

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25
The gastrocolic intestinal reflex has what mechanism and effect?
stomach distension increases colonic motility
26
4 substances that increase intestinal motility...
ACh, Gastrin, CCK, Motilin
27
5 substances that decrease intestinal motility...
NE, Somatostatin, Secretin, VIP, GIP
28
The duodenal brush border secretes ______ which has what effect on pancreatic secretions?
enterokinase, activate pancreatic zymogens
29
What two structures secret mucus to protect and lubricate the small intestine?
glands of lieberkuhn and goblet cells
30
What three substances stimulate small intestinal secretion, along with local neural reflexes after chyme entry...
secretin, CCK, ACh
31
How long is the human colon?
about 1.3m
32
3 separated bands of longitudinal muscle makes up the...
taeniae coli
33
What forms the internal anal sphincter?
circular muscle
34
The external anal sphincter is made up of...
striated muscle
35
these structures of the wall of the colon form pockets...
haustra
36
T/F: colonic mucosa do not contain villi
T
37
Is mucosa thicker in the colon or small intestine?
colon
38
The colon has deeper crypts with increased presence of what cell type?
more goblet cells
39
What are two functions of the ileocecal valve?
prevent backflow and contamination
40
Gastric activity mediated by gastrin increases ileal motility. This is called the _____ reflex
gastroileal
41
What causes relaxation of the ileocecal sphincter?
ileocecal reflex
42
What two substances are not transported in the colon?
glucose and AAs
43
Most sodium in the GI tract is absorbed where?
colon
44
What volume of chyme does the colon receive every day?
500 ml/day
45
Of the 500 ml entering the colon per day, _____mL is absorbed and ______ is voided
350 ml absorbed 150 ml voided
46
of the 150 ml of chyme voided every day, what volume is water?
100
47
The intestines are an (aerobic/anaerobic) environment...
anaerobic
48
What are the products of intestinal bacterial metabolism?
gases: H2, N2, CO2, methane, hydrogen sulfide
49
intestinal bacteria aid in synthesizing what two substances?
b complex vitamins and vitamin K
50
extrinsic regulation of colonic motility is controlled by the____
PNS (Excitatory) and SNS (Inhibitory)
51
This PNS nerve innervates the cecum, ascending and transverse colon...
vagus
52
This PNS nerve innervates the descending colon, sigmoid colon, and rectum
pelvic nerve
53
What two SNS structures innervate the colon?
superior mesenteric ganglion (distal 1/2) inferior mesenteric ganglion (proximal 1/2)
54
Intrinsic innervation of colonic motility is obtained by...
enteric plexuses
55
What are the 2 principal functions of the colon?
absorb water and lytes store/expel fecal matter
56
Are strong contractions necessary to accomplish the chief functions of the colon?
no
57
Characterize colonic motility...
sluggish
58
What two types of motility are present in the colon?
mixing/haustration propulsion
59
what process is described below? - very slow movement - aids in absorption of water and lytes - no propulsion, mixing action
haustration
60
Slow movement of haustration allows growth of what?
bacteria
61
how many mass movements in the colon are there per day?
1-3
62
What stimulates colonic mass movement?
gastrocolic reflex (gastrin)
63
Gastrocolic reflex is most evident when, causing a strong urge to do what?
evident after 1st meal urge to defecate
64
In mass movement, what two parts of the colon contract simultaneously?
ascending and transverse colon
65
Contraction of the colon during mass movement drives feces how far in just a few seconds?
1/3 to 3/4 length of colon
66
What factor initiates defecation?
rectal filling by mass movement
67
What three things occur when intraluminal rectal pressure increases with colon distension?
active rectal contraction reflex relaxation of internal sphincter constriction of external sphincter
68
When defecation is to occur, the external sphincter is relaxed how?
voluntarily
69
What increases intra-abdominal pressure to assist with defectaion?
valsalva

Physiology II (28 decks)

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