Session 1 - Purpose of the Gut Flashcards
What is the purpose of the gut?
- to provide a port of entry for food into the body
- to mechanically disrupt the food
- to temporarily store the food
- to chemically digest the food
- to kill pathogens in the food
- to move food along the tract
- to absorb nutrients from the resultant solution
- to eliminate residual waste material
Where does mechanical disruption of food occur and how does this happen?
Mouth/teeth - chewing
Stomach - contracts to liquefy food (producing chyme). The upper stomach creates basal tone (slow/sustained contractions) and the lower stomach creates powerful peristaltic contractions that grind food (thicker muscle present more distally).
What is receptive relaxation?
A reflex in which the gastric fundus dilates when food passes down the pharynx and oesophagus. Needed to stop intraluminal pressures rising.
What defences does the GI tract have against pathogens?
Saliva
Hydrochloric acid
Liver (Kupffer cells)
Peyers patches - lymphoid follicles found in the submucosa of mainly the terminal ileum
What are the types of movement along the GI tract?
Peristalsis - oesophagus, stomach, small intestine
Segmentation - stomach, small intestine
Haustral shuttling - large intestine
Mass movements - large intestine
Where does chemical digestion occur and how?
Saliva - amylase
- lipase
Stomach - acid
- pepsin
duodenum/jejunum - bile
- exocrine pancreas (protease,
amylase, lipase)
What is peristalisis?
A series of wave like contractions that moves food along the digestive tract. Occurs in the oesophagus, stomach and small intestine.
What is segmentation?
Relatively weak contractions that thoroughly mix ingested food. Occurs in the stomach, small intestine and partially in the large intestine.
What is mass movement?
A sudden, uniform peristaltic contraction of smooth muscle of the gut which originates at the transverse colon and rapidly moves faeces into the rectum. Mass movement only occurs once or twice a day.
What structural features aid absorption in the gut?
Length of the gut
Folds
Villi/microvilli
What is the gastrocolic reflex?
An increase in motility in the colon due to stretching of the stomach after eating.
Name all the sphincters of the GI tract.
Upper oesophageal sphincter Lower oesophageal sphincter Pyloric sphincter Ileocecal valve Internal anal sphincter External anal sphincter Sphincter of Oddi
Which organs are intraperitoneal viscera?
Stomach Spleen Liver Bulb of duodenum Jejunum Ileum Transverse colon Sigmoid colon
Which organs are retroperitoneal viscera?
Duodenum (except proximal part) Caecum Ascending colon Descending colon Pancreas Kidneys
What is an oesophagogastroduodenoscopy (OGD)?
An endoscopy that can visualise the oesophagus, stomach and first section of the duodenum.
