GI 09

Question 1

Large intestine anatomy

Answer 1

cecum, colon (ascending, transverse, descending), rectum, anus

Question 2

Purpose of large intestine

Answer 2

digestion and absorption of meal that was not accomplished in small intestine, absorption of wter, storage of waste products for elimination, and commensal bacteria

Question 3

What sphincter separates small intestine from large intestine

Answer 3

ileocecal sphincter

Question 4

when does ileocecal sphincter open

Answer 4

Short range peristalsis in ileum opens sphincter allowing squirting of chyme into cecum

Question 5

does electrical activity from ileum propagate into large intestine

Answer 5

nope

Question 6

regulation of colonic function is primarily controlled by what?

Answer 6

neural pathways

Question 7

local reflexes of colonic control

Answer 7

Activated by passage of a bolus of fecal material - stimulates short bursts of cl and fluid secretion , involves serotonin and Ach

Question 8

Long reflex arcs involved in colonic function

Answer 8

Gastrocolic reflx - distention of stomach increases colonic motility and mass movement of fecal material (involves serotonin and Ach)
Orthocolic reflex - activated on rising from bed and promotes morning urge of defecation in some people

Question 9

What is secreted in response to lipid in lumen of colon

Answer 9

peptide YY (PYY) is secreted from entoerodocrine cells in terminal ileum and colon

Question 10

what is peptide yy (PYY)

Answer 10

“ileal break”

decreases gastric emptying and overall intestinal motility, reduces chloride and thus fluid secretion by intestinal cells, and by reducing fluidity and inhibiting motility it reduces propulsion of chyme, allowing for greater digestion and absorption time in small intestine

Question 11

Two forms of colonic motility

Answer 11

short duration

long duration

Question 12

short duration colonic motility

Answer 12

Contractions ~8s that originate in circular muscles at intervals - divides colon into segments ./ haustra –> these are segmental contractions that mix and circulate contents and optimize absorption of water and salts

Question 13

long duration contractions of colon

Answer 13

20-60s, produced by longitudinal muscles (taeniae coli) - propel bolus (less vigorous than small intestine)
contents are moved back and forward between haustr which maximizes time of contact with epithelium)

HIGH AMPLITUDE PROPAGATING CONTRACTIONS OCCUR IN HEALTHY INDIVIDUALS 10X/DAY FROM CECUM TO RECTUM TO CLEAR THE COLON
this was in red so she wants us to know it

Question 14

What controls descending and sigmoid colons, rectum, and anal canal (neurally speaking)

Answer 14

pelvic nerves from sacral spine

Question 15

SNS activity on colon does what

Answer 15

decreases motility

Question 16

Major role of colonic epithelium is to absorb nutrients, or water and electrolytes?

Answer 16

water and electrolytes

Question 17

What major nutrient DOES the colon absorb

Answer 17

Short chain fatty acids salvaged from non-absorbed carbohydrates by colonic bacteria

Question 18

How are SCFA’s absorbed in the colon

Answer 18

absorbed in luminal side in sodium dependent manner using symporters (sodium monocarboxylate transporters) driven by NKA gradient

Question 19

How is sodium absorbed in distal colon

Answer 19

ENaC

Question 20

What opens ENaC

Answer 20

Neurotransmitters or hormones - driven by NKA gradient

Question 21

What other way can water and chloride flow in colon

Answer 21

tight junctions - maintinas electrical neutrality and prevents water loss in stool

Question 22

What happens if you have reduced ENaC expression

Answer 22

you get bowel inflammation and diarrhea

Question 23

What are the nutrients bacteria can take up and use to make their own shit that we then absorb or excrete

Answer 23

Urea, bilirubin, primary bile acids, cnjugated bile acids, fiber

Question 24

Internal and external sphincters - what muscles are they made of

Answer 24

Inner - thick circular muscle

external - striated muscle wrapping around the canal, innervated by puendal nerves

Question 25

Filling of rectum causes what to internal anal sphincter

Answer 25

Generation of VIP, NO and relaxation of internal sphincter

Question 26

Hirschsprung’s disease

Answer 26

Segment of colon is permanently contracted, causing an obstruction - this can lead to surgical excision of the bad area - usually found in infants