Structure + Function of the GI Tract Flashcards
what is aboral movement?
movement from mouth to anus
what is oral movement?
movement from anus to mouth
what are the roles of the mouth?
chops food
starts carbohydrate digestion
propels food to the oesophagus
what is the role of the oesophagus?
propels food to the stomach via peristalsis
what are the roles of the stomach?
stores + churns food
continues carb digestion
initiates protein digestion
regulates delivery of chyme to duodenum
what are the three parts of the small intestine?
duodenum
jejunum
ileum
what is the principal site of digestion and absorption of nutrients?
the small intestine
what are the three parts of the large intestine?
caecum
appendix
colon
what parts is the colon divided into?
ascending
transverse
descending
sigmoid
what are the roles of the colon?
reabsorbs fluid + electrolytes
stores faecal matter
what is the role of the rectum and anus?
regulated expulsion of faeces
what are the accessory structures of the GI tract?
salivary glands
pancreas
liver
gallbladder
what makes up the hepatobiliary system?
the liver and the gallbladder
name the layers of the GI tract wall, from inner to outer
mucosa
submucosa
muscularis externa
serosa
what are the three layers of the mucosa?
mucous membrane (epithelium)
lamina propria
muscularis mucosae
what is the submucosa made of?
connective tissue
what neurone network is found in the submucosa?
the submucous plexus
what are the two layers of the muscularis externa?
inner circular layer
outer longitudinal layer
what does contraction of the inner circular muscle of the muscularis externa do?
narrows and lengthens the lumen
where is the myenteric plexus found?
between the two layers of the muscularis externa
what is the role of the myenteric plexus?
it governs the muscle activity of the GI tract
what does contraction of the outer longitudinal muscle of the muscularis externa do?
shortens and widens the lumen
what is the serosa made of?
connective tissue
contains secretory cells
what are the four major functions of the alimentary canal?
motility
secretion
digestion
absorption
what parts of the GI tract contain skeletal muscle?
mouth
pharynx
upper oesophagus
external anal sphincter
what type of muscle is most common for motility in the GI tract?
smooth
what is chemical digestion?
chemical breakdown of complex foodstuffs into small absorbable units
what are the two types of digestion?
chemical
physical
what is physical digestion and where does it occur?
the chopping and churning of food
in the mouth, stomach and small intestine
what does contraction of the muscularis mucosae cause?
a change in the absorptive and secretory area of the mucosa
also mixes the contents of the lumen, ensuring it is all digested
why are smooth muscle cells in the GI tract electrically coupled, and what couples them?
to allow the slow wave of depolarisation to spread across the muscle
coupled by gap junctions
what are the muscle cells in the digestive system called?
single unit muscle cells
what cell drives the slow wave electrical activity of the GI tract and what type of cell is this?
interstitial cells of cajal (ICCs)
pacemaker cells
when does contraction in the intestine occur?
only when slow wave amplitude is sufficient to reach threshold and triggers smooth muscle cell calcium action potentials
what is the force of intestinal contraction related to?
the number of AP’s discharged
this is driven by the time the slow wave is above threshold
what are slow waves also known as?
the basic electrical rhythm (BER)
