Motility of the GI Tract

Question 1

Pathway of GI tract ?

Answer 1

oral cavity - pharynx - upper oesophageal sphincter - oesophagus - lower oesophageal sphincter
stomach - pyloric sphincter - small intestine - iliocaecal sphincter - colon - rectum - anal sphincter

Question 2

accessory organs of GI tract ?

Answer 2

parotid salivary gland
teeth
tongue
sublingual and submandibular salivary glands
liver
gall bladder
pancreas

Question 3

layers of the GI wall ?

Answer 3

serosa
muscularis externa
submucosa
mucosa
lumen

Question 4

serosa ?

Answer 4

connective tissue and layer of squamous epithelial cells
referred to as adventitia in the oesophagus

Question 5

muscularis externa ?

Answer 5

outer longitudinal layer of smooth muscle
inner circular layer of smooth muscle
contains myenteric nerve plexus which is part of the enteric nervous system

Question 6

submucosa ?

Answer 6

connective tissue that links the mucosal and muscular layer
contains blood supply and lymph vessels
contains submucosal nerve plexus which is part of the enteric nervous system

Question 7

mucosa ?

Answer 7

muscularis mucosae is a very thin layer of smooth muscle
lamina propria is mostly connective tissue but also includes some lymphatic tissue
epithelium contains both endocrine and exocrine cells

Question 8

region specialisation in the GI tract ?

Answer 8

oesophagus - smooth muscle facilitated transport
stomach - storage, secretion, mixing, and digestion via the inner oblique muscle
small intestine - secretion, mixing, majority of digestion, absorption
large intestine - limited absorption to water and ions, faeces formation, gut microbiota

Question 9

endocrine cells in the GI wall ?

Answer 9

gastrin
cholecystokinin
secretin
gastric inhibitory peptide
motilin

Question 10

what is gastrin secreted by

Answer 10

G cells in the stomach and small intestine

Question 11

what is cholecystokinin secreted by ?

Answer 11

I cells in the small intestine

Question 12

what is secretin secreted by ?

Answer 12

S cells in the small intestine

Question 13

what is gastric inhibitory peptide secreted by ?

Answer 13

K cells in the small intestine

Question 14

what is motilin secreted by ?

Answer 14

M cells in the small intestine

Question 15

function of gastrin

Answer 15

increases gastric acid secretion and mucosal growth

Question 16

function of cholecystokinin

Answer 16

increase pancreatic secretion
decrease gastric emptying

Question 17

function of secretin

Answer 17

increases pancreatic secretion
decreases gastric acid secretions

Question 18

function of gastric inhibitory peptide

Answer 18

increase insulin release
decrease gastric acid secretion

Question 19

function of motilin

Answer 19

increases gastric motility and intestinal motility

Question 20

what is digestion dependent on

Answer 20

coordinated activity of smooth muscle cells

Question 21

specialised pacemaker cells

Answer 21

interstitial cells of Cajal

Question 22

how are cells joined in smooth muscle functional syncytium

Answer 22

with gap junctions to allow electrical coupling

Question 23

function of gap junctions

Answer 23

enables a group of muscle cells to act as a single functional unit or functional syncytium

Question 24

describe basal electrical rhythm

Answer 24

GI smooth muscles have a negative resting membrane potential at around -55mV
interstitial cells of cajal drive cyclical slow waves that form basic electrical rhythm
if a slow wave crosses the threshold potential, spike potentials occur which drive muscle contraction through calcium influx

Question 25

what is enteric nervous innervation

Answer 25

provides a fine tuning of the basic electrical rhythm of the GI tract

Question 26

what triggers ENS activity

Answer 26

nutrients, starch, ph and osmolarity

Question 27

what is the ENS comprised of

Answer 27

two interconnected plexuses
myenteric plexus for motility
submucosal plexus for secretion and blood flow