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GI Physiology > Micturition and Colonic Function > Flashcards

Micturition and Colonic Function Flashcards

1
Q

what is the posterior urethra?

A

funnel shaped extension of the body of the bladder that connects to the urethra. includes the internal sphincter

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2
Q

what lies on the posterior wall of the bladder between the ureters? what happens to it during bladder emptying?

A

the smooth trigone area

relaxes during bladder emptying

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3
Q

what is the body of the bladder composed of?

A

the detrusor muscle

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4
Q

describe the bladder emptying reflex.

A

stretch receptors from the posterior urethra usually trigger micturition
response is inhibited and control of this reflex is learned

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5
Q

what structure in the CNS control the detrusor muscle and urinary sphincters? what controls this center?

A

pontine micturition center

it is controlled by suprapontine centers

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6
Q

what does the PNS control in micturition? what inhibits it?

A

control the detrusor muscle contraction and internal sphincter relaxation
inhibited by efferent impulses from the brain

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7
Q

what nerve innervates the external sphincter?

A

the pudendal nerve

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8
Q

describe the SNS control over micturition

A

beta adrenergic receptors inhibit detrusor contraction

alpha adrenergic receptors promote contraction of the internal sphincter

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9
Q

what are the abnormalities of micturition?

A

atonic bladder and incontinence by sensory destruction
automatic bladder by suprasacral spinal injury
neurogenic bladder by lask of inhibitory signals from brain

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10
Q

what are the functions of the large intestine?

A

move material from SI to rectum
eliminate fecal matter through anus
extract water, electrolytes and nutrients

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11
Q

what does the colon secrete and what is its function?

A

mucus to bind feces, aid fecal movement and protect the colonic mucosa

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12
Q

what is the gastroileal reflex?

A

intensifies peristalsis in the ilem to empty its contents into the cecum

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13
Q

what are the comparative dwell times and functions of the large intestine?

A

ascending colon- absorption, short dwell time
transverse colon- absorption, long dwell time (24 hrs)
descending colon- stool storage

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14
Q

what are the two types of diarrhea?

A

osmotic- non absorbable solutes in lumen

secretory- excess secretion of fluids by crypt cells due to bacteria

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15
Q

what delays ileal emptying into the colon? how is this mediated?

A

distension, pressure or irritiation of the cecum

mediated by myenteric plexus and SNS

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16
Q

what are the symptoms of appendicitis? what is the cause?

A

symptoms: gastric pain, vomiting and fever. if not removed- peritonitis and septicemia
cause is obstruction of appendix by calcified fecal matter

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17
Q

what immune tissue is in the colon?

A

lymphatic nodules (no pyer’s patches)

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18
Q

what is absorbned and secreted by the colon?

A

absorbs Na, Cl and water (follows solutes)

secretes K and bicarbonate

19
Q

what apical transporters are in the colon mucosa?

A

Na/H and Cl/HCO3 antiporters (electroneutral) and active K secretion

20
Q

what stimulates K secretion into the lumen of the colon?

A

aldosterone, cAMP and cholera

21
Q

how is electrical conduction in the large intestine similar to the small intestine?

A

there are slow waves that are pace makers

no action potentials unless there are triggers from the PNS, SNS, chemical or stretch

22
Q

what are haustrations?

A

large circular muscle constrictions that allow slow segmental propulsion and mixing- time for fluid and electrolyte reabsorption

23
Q

what are mass movements?

A

large peristaltic movements that force feces towards the rectum. haustrations disappear. signal the urge to defecate

24
Q

what is the gastrocolic reflex?

A

reflexive mass movement after a meal

25
Q

which reflexes are absent with removal of the ANS from the colon?

A

gastrocolic and duodenocolic reflexes

26
Q

what does colonic irritation cause?

A

persistant mass movements like in ulcerative colitis

27
Q

what is hirschsprung’s disease?

A

lack of ENS in the distal GI tract> cannot pass fecal matter
feces build up in the belly
early obstructive syndrome in infants can be life threatening

28
Q

how is hirschsprung’s dieease treated?

A

by removing the affected portion of the colon

29
Q

where does flatus come from? if it is not expelled, what happens to it?

A

swallowed air, bacteria and diffusion from the blood

it is absorbed into the blood or combined with fecal matter

30
Q

what is the composition and net production of flatus caused by?

A

composition of colonic microflora

31
Q

what does excessive flatulence indicate?

A

IBS, lactose intolerance, celiac disease or others

32
Q

what is contained in feces?

A

mucus, cellular debris, bacteria, enzymes, and undigested food

33
Q

what is responsible for the color of feces?

A

stercobilin

34
Q

how does the electrolyte composition of feces relate to that of chyme?

A

higher in K and lower in Na

35
Q

what is IBS and what is it associated with?

A

GI disorder- crampy pain, bloating, gassiness and altered bowel habits
associated with stress

36
Q

how is IBS treated?

A

opioids and serotonin receptor antagonists in diarrhea prominant cases
SSR agonists and soluble fiber in constipation cases

37
Q

why is the rectum normally empty?

A

because of the turn of the colon and a weak sphincter between the rectum and the sigmoid colon

38
Q

what causes fecal incontinence? where is the pathophysiology located?

A

injury to the pelvic floor, trauma, surgery, or prolapsed rectum
problem with external anal sphincter

39
Q

what are the treatments for fecal incontinence?

A

bulking agents, surgery and strengthening the pelvic floor muscles

40
Q

describe the myenteric defecation reflex

A

distention of the rectal wall> peristaltic waves in descending and sigmoid colon and rectum
internal anal sphincter relaxed by inhibitory signals

41
Q

what reflex fortifies the myenteric defecation reflex?

A

the parasympathetic defecation reflex from sacral spine

intensifies all aspects of myenteric reflex

42
Q

what other effects do defecation signals cause?

A

taking deep breath, glottis closure, abdominal wall contraction and pelvic floor relaxation to pull open the anal ring

43
Q

what do destruction to nerves of defecation cause?

A

pathways in spinal cord and cerebrum- loss of control

nerves leading to anorectal region- fecal retention

GI Physiology (7 decks)

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