Week 1 Overview of GI Function and Anatomy Flashcards
what accessory organs assist the GI tract?
salivary glands, pancreas, liver, gallbladder
what are the 4 layers of the gut wall?
mucosa- simple squamous epithelium, lamina propria, muscularis mucosae
submucosa
external muscle layer- muscularis externae- circular inner, longitudinal outer- creates peristalsis
serosa
describe the general structure of the alimentary canal
mouth, tongue, pharynx, oesophagus, stomach, small intestines (duodenum, jejenum, illium), cecum, large intestines (ascending, transverse and descending colon), rectum, anus
what are peyers patches and which layer of the gut wall are they present?
aggregations of lymphocytes in lamina propria
outline the broad functions of the various regions of the GI tract
mouth- port of entry for food teeth- mechanically disrupt food stomach- temporary store food, chemically digest it and kill pathogens within it - acid peristalsis- move food along tract intestines- absorb nutrients rectum- eliminate residual waste
describe the functions, nervous control (2 plaxuses), muscles present of the oesophagus
receives bolus of food from mouth
rapid peristaltic transport to stomach- 8-9 seconds
upper end- voluntary control- striated muscle
lower end- involuntary control- smooth muscle
myenteric plexus between outer muscle layers
submucosal plexus between submucosa and external muscle
describe the digestive processes that continue in the somach
physical disruption- churning- 3 muscle layers and mucosal rugae
chemical disruption- by acid (HCL) and enzymes
what are the overall functions of the stomach and how does this generally work?
- acts as food storage- eat faster than can digest
- wall relaxes so stomach pressure doesnt rise- receptive relaxation
- contracts rhythmically to mix and disrupt
- secretes acid and proteolytic enzymes to break down and disinfect
- secretes mucus to protect epithelia otherwise = ulcers
- produces hypotonic chyme by combining action of acid, enzymes and agitation
- delivers imcompletely digested chyme slowly to duodenum
describe what digestive processes that occur in the mouth
physical disruption- mouth- teeth, tongue, muscle of mastication
chemical disruption- salivary amylase, lipase
what are the functions of saliva?
start digestion- amylase and lipase
bacteriostatic- contains IgA- released through gut and resp
high Ca- protects teeth
assist swallowing- lubrication
what occurs in the duodenum?
DILUTION AND NEUTRALISATION OF CHYME
- dilution as hypertonic - water drawn in from ECF to = isotonic
- liver releases bile via gallbladder- contains water, alkali and bile salts (emulsify fats)
- pancreas also secretes alkali to neutralise
- pancreas, liver and intestine secretes enzymes which act with the bile to complete digestion of chyme
what do the enzymes from the pancreas and intestines do to complete digestion?
cleave peptides to AAs
cleave polysaccharides to monosaccharides
break down and reform lipids
break down nucleic acids
what is required for successful absorption and what is absorbed where?
lots of energy- active process
large SA- folded gut, villi, micro-villi- adequate contact time
good blood supply, drainage
occurs in small intestines- more proximally
duodenum- iron
jejunum- most sugar, AAs and FAs
ilium- vit B12, bile acids and remainders
H2) still to be absorbed
what occurs in the large intestines?
water recovery continues over 20hr transit
by the end content semi solid ready for expulsion in colon
where contains most of the GIs bacteria?
colon- 99% anaerobic and most lost in faeces
