T1 - Motility of the GI tract

Question 1

what are the four layers of the GI tract from the lumen in?

Answer 1

Mucosa, sub mucosa, muscular externa, serosa

Question 2

what layer of the GI tract is the connective tissue layer?

Answer 2

sub mucosa

Question 3

what is most motility governed by in the GI tract?

Answer 3

contraction of smooth muscle

Question 4

what type of contraction are the oesophagus and anal sphincter governed by and what does this allow?

Answer 4

striated muscles contraction allows voluntary control

Question 5

what are the two interconnected plexi in the gut wall and where are they found

Answer 5

myenteric plexus in the muscular layer and submucosal plexus in the SM layer

Question 6

what do the two plexi in the gut wall control?

Answer 6

myenteric controls motility and submucosal controls secretion and local blood flow

Question 7

what is the parasympathetic innervation up to the TV colon?

Answer 7

vagus

Question 8

what is the parasympathetic innervation after he TV colon?

Answer 8

sacral parasympathetic nerves

Question 9

where does sympathetic innervation of motility come from?

Answer 9

paravertebral symp ganglia - coeliac, sup mesenteric and inf mesenteric

Question 10

where do hormones go after they are secreted from entereoendocrine cells?

Answer 10

into the portal circulation

Question 11

what cells is CCK released from and what does it cause?

Answer 11

released from I cells in SI and inhibits gastric emptying

Question 12

what cells is motion released from and what does it cause?

Answer 12

released by M cells and causes gastric and intestinal motility

Question 13

what are slow waves

Answer 13

cycling waves of negative elec potential that get more positive over time

Question 14

what are spike potentials

Answer 14

take the membrane to threshold and allow contraction to occur

Question 15

what three things inhibit contraction?

Answer 15

sympathetic ANS (NA), hormones eg CCK and hyper polarisation

Question 16

what generates basal metabolic rhythm?

Answer 16

slow waves

Question 17

what type of contraction involves bursts of circular muscle contraction and relaxation?

Answer 17

segmentation - mixing

Question 18

what type of contraction in valves contraction behind a a bolus and relaxation in front (only aborally)

Answer 18

peristalsis

Question 19

what plexus is implicated in hirschprungs disease?

Answer 19

myenteric

Question 20

what type of epithelia line the oesophagus?

Answer 20

stratified squamous

Question 21

what type of muscle is in the muscle layer of the oesophagus?

Answer 21

striated

Question 22

where does striated muscle become smooth muscle in the oesophagus?

Answer 22

after the upper oesophageal sphincter

Question 23

what type of movement occurs in the oes after the junctions of striated and smooth muscle?

Answer 23

slow peristaltic waves

Question 24

what causes receptive relaxation in the oesophagus?

Answer 24

when the lower sphincter relaxes

Question 25

what is achalasia?

Answer 25

when the LOS fails to relax so food stays in the oesophagus

Question 26

what is GORD?

Answer 26

when the LOS loses tone and causes acidic gastric contents in the oesophagus

Question 27

what area of the stomach has a third oblique muscle in the muscle layer?

Answer 27

body

Question 28

what is the response in the stomach when a bolus enters?

Answer 28

receptive relaxation and stimulation from the vasovagal reflex

Question 29

what forces chyme to the duodenum?

Answer 29

powerful peristaltic contractions

Question 30

what hormone causes gastric emptying?

Answer 30

motion

Question 31

what hormones prevent gastric emptying?

Answer 31

cck and secretin

Question 32

what mixes and grinds food in the distal part of the stomach?

Answer 32

antral systole

Question 33

what three hormones slow chyme movement to the duodenum and therefore increasing digestion (inhibit gastric emptying)

Answer 33

CCK, secretin and GIP

Question 34

what is dumping syndrome and when does it occur?

Answer 34

rapid entry of the gastric contents to the SI | - occurs after ingestion of a large meal or post gastrectomy

Question 35

what is gastroparesis and when does it occur?

Answer 35

when the stomach fails to empty | - can be due to impaired vagal stimulation in the stomach due to severe diabetes

Question 36

what three things increase the surface area of the small intestine?

Answer 36

1) circular folds (pilae circulars) 2) villi projections of mucosa 3) brush border microvilli on epithelial surface

Question 37

how long does it take digestion and absorption to occur in the SI?

Answer 37

3-5 hours

Question 38

what predominantly controls motility in the SI?

Answer 38

intrinsic ENS

Question 39

what is propulsive peristalsis initiated by?

Answer 39

stretch and hormones

Question 40

how is segmentation for mixing triggered in the SI?

Answer 40

by stretch receptors that trigger myenteric stimulation of muscle contraction in response to chyme

Question 41

which hormones excite propulsive peristalsis?

Answer 41

gastrin, CCK, insulin, motion, 5HT

Question 42

which hormones inhibit propulsive peristalsis?

Answer 42

secretin and glucagon

Question 43

what is the migrating motor complex and what controls it?

Answer 43

- sweeps the contents of the SI into the colon every 90 mins - peristaltic contractions - ENS control

Question 44

what three things can result from disruptions to peristalsis?

Answer 44

- peristaltic rush (rapid sweeping on contents due to mucosal irritation) - vomiting (reverse peristalsis) - paralytic ileus (loss of peristalsis following mechanical trauma)

Question 45

what two roles does the commensal microbiome in the large intestine play?

Answer 45

- helps digestion | - synthesises vitamin B and K

Question 46

what forms taniae coli?

Answer 46

thickening of longitudinal muscle into three bands

Question 47

what forms from tonic contraction of tanaie coli?

Answer 47

haustral bulges

Question 48

what type of movements allow mixing in the LI?

Answer 48

haustral churning and peristalsis (mass movement and slow waves)

Question 49

what reflex occurs after a meal due to stretching of stomach and duodenal walls?

Answer 49

gastroduodenal colic reflexes

Question 50

what initiates the defection reflex?

Answer 50

mass movement of faecal matter into an empty rectum

Question 51

what does faecal matter in the rectum stimulate?

Answer 51

myenteric plexus and psym ANS

Question 52

what causes the internal anal sphincter to open

Answer 52

involuntary contraction of longitudinal muscle in the the rectum

Question 53

what allows defacation?

Answer 53

voluntary relaxation of the the external anal sphincter via skeletal muscle motor neuron stimulation