Colonic Motility

Question 1

Phasic contractions of the colon are optimized for

Answer 1

Water and electrolyte absorption and storage and evacuation of feces

Question 2

Tenia Coli

Answer 2

3 bands of longitudinal muscle from cecum to rectum

Question 3

Haustra

Answer 3

bulges of colon wall where longitudinal muscle is thin, increases SA of colon

Question 4

IAS

Answer 4

circular smooth muscle

Question 5

EAS

Answer 5

striated muscle

Question 6

Parasympathetic innervation to colon - VAGUS

Answer 6

cecum, ascending colon, and transverse colon

Question 7

Parasympathetic innervation to colon - PELVIC

Answer 7

descending colon, sigmoid colon, rectum

Question 8

PUDENDAL n

Answer 8

somatic motor innervation to EAS

Question 9

Sympathetic innervation to colon

Answer 9

innervate ENTIRE colon

Question 10

Innervation of the IAS

Answer 10

Pelvic n indirectly via enteric neurons

Question 11

5 types of phasic contractions in the colon

Answer 11

Haustral shuttling, haustral propulsion, multihaustral propulsion, haustral retropulsion, mass movement

Question 12

Haustral shuttling

Answer 12

Mixing of contents for absorption of water and electrolytes, (NON-PROPULSIVE), tenia coli and circular muscle contractions cause random appearance and disappearance of haustra

Question 13

Haustral propulsion

Answer 13

few adjacent hausfrau contract sequentially for aboral displacement of contents (5-10cm movement)

Question 14

Multihaustral propulsion

Answer 14

Contraction of many hausfrau, aboral movement of 18-20cm

Question 15

Haustral retropulsion

Answer 15

adjacent haustra contract in an oral direction, and contents move backward 5-20cm

Question 16

Mass movement

Answer 16

gastrocolonic reflex; strong contraction of MANY circular muscle and tenia coli, aboral movement >30cm; after ingestion of meal

Question 17

Common motility pattern of proximal colon

Answer 17

haustral propulsion, multihaustral propulsion, haustral retropulsion

Question 18

Common motility pattern of distal colon

Answer 18

Haustral shuttling, haustral retropulsion

Question 19

Purpose of common motility patterns

Answer 19

slow transmit in distal colon to increase absorption and minimize incontinence

Question 20

Mass movements effect on normal motility patterns

Answer 20

cause strong aboral contractions, initiated by TRANSVERSE, descending or sigmoid colon

Question 21

MMC in colon

Answer 21

DOES NOT EXIST :( :(

Question 22

Rectum motility

Answer 22

fecal material enters during a mass movement, can be stored and sent back to sigmoid via retropulsion

Question 23

Rectoanal inhibitory reflex

Answer 23

distention of the rectal smooth muscle causes IAS relaxation (long and short neural pathways)

Question 24

EAS

Answer 24

HIGH basal tone (pudendal n) - voluntary

Question 25

Gastrocolonic Reflex

Answer 25

food enters stomach and causes increased colonic motility

Question 26

Fast component of Gastrocolonic Reflex

Answer 26

gastric distention - long neural reflex - PNS (vagal and pelvic) activity

Question 27

Slow component of Gastrocolonic Reflex

Answer 27

gastric distention - increased gastrin release - short neural reflex - increased colonic motility

Question 28

The urge to defecate often occurs

Answer 28

30 min after a meal due to gastrocolonic reflex and MASS movements

Question 29

rectum is generally empty because

Answer 29

mass movement and filling leads to defecation (lax IAS), or retropulsion

Question 30

Rectum as temporary storage

Answer 30

if defecation is not appropriate, the rectum can store the feces -> rectal SM relaxes --> rectal pressure decreases --> IAS constricts --> haustral retropulsion into sigmoid colon

Question 31

What causes IAS to relax

Answer 31

PNS to myenteric inhibitory neurons --> increased NO

Question 32

Hirschsprung's Disease

Answer 32

ENS absent in distal colon/rectum, failure of phasic contractions or relaxation of IAS

Question 33

Pressures during defecation

Answer 33

rectum: HIGH, IAS: medium, EAS: low

Question 34

Defecation involves ______________ neural reflex

Answer 34

long and short

Question 35

Short neural reflex functions to

Answer 35

Increase haustral propulsion, increase intra-luminal pressure, and relax the IAS

Question 36

Short neural reflex for defecation is activated by

Answer 36

IPAN activation by rectal distention

Question 37

Long neural reflex functions to

Answer 37

Increase haustral propulsion, increase intra-luminal pressure, and relax IAS

Question 38

Muscles active to defer defecation

Answer 38

puborectalis, EAS contract = narrow anorectal angle and increase pressure

Question 39

Defecation

Answer 39

puborectalis and EAS relaxed via pudendal n, widen the anorectal angle and relieve pressure

Question 40

Somatic and PNS act on various structures during defecation

Answer 40

Valsalva maneuver and relaxation of pelvic muscles

Question 41

Constipation definition

Answer 41

>2 stools/week, straining, hard stools, feeling of incomplete evacuation

Question 42

Slow-Transit Constipation (STC)

Answer 42

increased transit time from proximal to distal colon

Question 43

Cause for Slow-Transit Constipation

Answer 43

weak mass movement contractions, uncoordinated activity in distal colon resisting aboral movement

Question 44

Pelvic Floor Dysfunction

Answer 44

prolonged storage of feces in rectum

Question 45

Casuses of Pelvic Floor Dysfunction

Answer 45

Muscular hypertonicity of EAS (paradoxical contraction or incomplete relaxation), or hypotonicity of rectum

Question 46

transit time in the colon

Answer 46

1.5-4 days

Question 47

Fiber decreases transit time to

Answer 47

<30 hrs

Question 48

How fiber works

Answer 48

draws water into stool, increases stool weight, stretching of colon = motility, absorbs organic materials

Question 49

Fiber can absorb organic materials like

Answer 49

lipids, bile acids, and cholesterol

Question 50

ICC are more active in

Answer 50

a colon of a healthy patient than one who is constipated

Question 51

Hemorrhoids

Answer 51

acute lower GI bleed due to strained passage of hard stools or frequent diarrhea

Question 52

Colonic lesions

Answer 52

acute lower GI bleed due to ulcerative colitis, colon cancer or polyps, or infections

Question 53

Diverticulosis

Answer 53

acute lower GI bleed due to outpouchings of the colon wall