Physiology of the GI Tract Flashcards
Describe the General organisation of the GI
Mouth Esophagus Stomach Liver Duodenum Pancreas Jujenum Transverse colon Descending colon Ascending colon Ileum Appendix Rectum Anal Canal
Label the GI wall
Label the Gi wall
Describe the structure of the pharynx that allows movement through it
smooth muscle electrically coupled
segmented
peristaltic contractions
what is the main control of motility
intrinsic innervation enteric nervous system
IIENS
what is the role of the myenteric plexus vs the submucosal plexus
myenteric plexus is mainly motility whereas the submucosal is mainly formation of secretions and blood flow
can the IIENS act independently from other signals
yes it is part of the autonomic nervous system
what does parasympathetic increase
mobility and secretion as ach acts on muscarinic receptors increasing salivation mucosa and constriction
what does sympathetic do
reduces GI function as the noradrenaline relaxes the smooth muscle in GIT
what in addition to neurotransmitter influence the GI
hormones
what are two examples of hormones that affect the GI
Endocrine hormones e.g. gastrin
Paracrine e.g. histamine
what is motility
“Motility” is a term used to describe the contraction of the muscles that mix and propel contents in the gastrointestinal (GI) tract.”
what does saliva aid in
swallowing
beginning digestion
killing bacteria
what type of process is saliva controlled by
autnomic process
what does the parasympathetic watery saliva do
increases secretion and blood flow
what does the sympathetic mixed saliva do
increase secretion and reduces blood flow
describe the three steps of swallowing
voluntary swallow
peristalsis - distention triggered under autonomic control, mucous aids movement
enters stomach via esophageal sphincter
label the parts of a stomach
label the parts of a stomach
what is the stomach lined with
gastric glands
what is the role of the gastric glands
they secrete gastric juice
parietal cells secrete acid
chief cells produce pepsinogens and other digestive enzymes
what is contained in gastric juice
salts
HCL
pepsinogens
water
how much gastric juice is produced per day
2-3 litres produced per day
what does the low pH of 1-3 of the stomach help with
aids breakdown of tissue
activates pepsinogen and optimizes pepsin function
absorption of calcium and iron
protects against microorganisms / pathogens
Describe the formation of stomach acid
parietal cell carbonic anhydrase generates H+ and HCO3- from carbon dioxide and water
Cl enters the partietal cell in exchange of the HCO3-
and is transported out via the K+ CL- symport
Proton pump secretes H+ into the stomach lumen
describe the regulation of acid secretion
Gastrin is released from a G cell in response to nerve, hormonal and food stimuli
This activates the CCk2 receptors on ECL cells stimulating histamine release
this is then released from the entero chromaffin cell (ECL)
and it binds to the H2 receptors on parietal cells stimulating acid secretion
meanwhile acetylcholine stimulates the parietal cells from cholinergic nerves
