small intestine Flashcards
what vitamins are absorbed in the jejunum
D, E, A,K - these are all fat soluble
whats absorber un the duodenum
calcium, iron and magnesium
whats absorbed in the terminal ileum
bile salts and vitamin B12 (intrinsic factor for absorption, used in making RBC)
whats absorbed in the colon
short chain fatty acids
what is used to absorb glucose and galactose
sodium cotransporter
which vitamin needs intrinsic factor to be absorbed
B12
vomiting reflex
detected by vagal aferent nerve to the medulla oblongata
mechanism:
- phrenic nerve contracts diaphragm
- vagus nerve causes duodenum and pylorus to contract
- antrum contracts and UOS and LOS relax
- pressure increase forces stomach contents out
what does GI mucus act as
bicarbonate barrier, made up of mucin glycopeptides that’s used to trap water, bicarbonate and pathogens from entering the cells
what do GI prostaglandins do
stimulate the release of bicarbonate, inhibit histamine and HCl release, and maintain mucosal blood flow and epithelial restitution
peyer’s patch
tiny lymph nodes that keep intestinal flora at an appropriate level to stop pathogens and prevent infections
what are M cells
found in peyer’s patches and in the ileum and aggregate into little lymphoid tissues
umami
- found in foods with L-amino acids, mono sodium glutamate
- uses TIR1 and TIR3
sweet
- uses TIR2 and TIR3
bitter
- uses T2R
saltiness
- uses ENaC
what is the main immunological gut defence against foreign pathogens
IgA secretion
functions of saliva
- tooth maintenance
- lubrication
- antifungal/antimicrobial
- digestive
innervation of submandibular and sublingual glands
facial nerve (CN VII)
innervation of parotid gland
glossopharyngeal nerve (CN IX)
salivary gland secretions
parotid - mostly serous
submandibular - mix of serous and mucosal
sublingual - mostly mucosal
what stimulates saliva production
mastication
taste
smell
anticipation
what inhibits saliva production
fear
vomiting
what do acinar cells secrete
IgA
layers of GI tract (deep to superficial)
- mucosa
- submucosa (contains submucosal plexus)
- muscularis (circular muscle, myenteric plexus, longitudinal muscle)
- serosa (visceral peritoneum)
what do mucous/epithelial cells secrete
mucous
bicarbonate
gastric lipase
what do cheif cells secrete
pepsinogen
what do parietal cells secrete
HCl, intrinsic factor
what do G-cells secrete
gastrin
what do D-cells secrete
somatostatin
cephalic phase
- upon smelling/seeing/anticipating food, a large amount of gastric acid will be released ror a short amount of time
gastric phase
- stomach received bolus and distends, results in receptive relaxation to accommodate the food
- stomach detects peptides and amino acids by chemoreceptors, stomach releases more acid to compensate
intestinal phase
- duodenal cells can also detect stretch and the acidity of chyme - G cells in duodenum. an release gastrin to act on stomach parietal cells
migrating myoelectric complex phases (cleaning gut from residual contents)
- quiescent - no activities ongoing
- initiates random contractions
- burst of contractions (max amplitude and duration)
- rapid decrease of contraction
cholecystokinin
- made in duodenal I cells
- secreted due to fats and proteins
- act on acinar cells in pancreas, gallbladder and vagal afferent neurones
function of cholecystokinin
- digestive enzyme release
- gallbladder contracts, releasing bile
- inhibit food intake and induces satiety
gastrin
- made in G cells of stomach antrum
- secreted due to stomach distension and Ach release
- act on ECL to activate parietal cells
functions of gastrin
- histamine release
- HCl release
histamine
- made in stomach - ECL cells
- secreted due to gastrin simulation and Ach release
- acts on parietal cells in stomach
function of histamine
HCl release
somatostatin
- made in D cells in islets of pancreas and stomach pylorus duodenum
- secreted due to food in stomach - sympathetic stimuli
- act on - parietal cells in stomach, ECL, G cells, gallbladder, small intestine, exocrine cells in pancreas
functions of somatostatin
decrease HCl, histamine, gastrin, bicarbonate release, GB contractions and bile release, stops GI blood flow and absorption
secretin
- made in S cells in duodenum
- se feted due to low pH of chyme
- act on ductal cells of pancreas, parietal cells in stomach
function of secretin
- bicarbonate release, stops HCl release
gastric inhibitory peptide
- made in K cells in duodenum and jejunum
- secreted due to fatty chyme
- act on B cells in pancreas
function of GIP
insulin secretion
glucagon like peptide
- made in L cells in duodenum
- secreted due to fat and protein in duodenum
- act on B cells in pancreas
functions of GLP
- insulin secretion
- inhibits food intake, induces satiety
peptide YY
- made in L cells in ileum and colon
- secreted after food ingestion
- acts in intestines
functions of peptide YY
- increase water absorption
- inhibits gastric motility
-increases efficiency of digestion
vasoactive intestinal peptide (VIP)
- made in enteric neurones
- act on parietal and chief cells in the stomach, the pancreas and intestine
function of VIP
- stops HCl release
- pepsinogen release
- increase secretion of water in juice
motilin
- made in duodenum
- secreted due to fasting
- act on duodenum
functions of motilin
- increase gastric motility
- starts migrating motor complex
the myenteric plexus is located i between which 2 layers of the GI tract wall
circular muscle and longitudinal muscle
what results in increased gastric secretions
pepsis and amino acids in stomach lumen
what neurotransmitter is responsible for the relaxation of the gut lumen during peristalsis
NO
what cranial nerve senses distension in the gut lumen via baroreceptors and send signals to CNS via afferent nerve fibres
vagus (CN VII)
what does the coeliac trunk supply - T12
foregut : lower oesophagus, stomach, first 1/2 duodenum
what does the superior mesenteric artery supply - L1
midgut : last 1/2 duodenum to 2/3 transverse colon
what does the inferior mesenteric artery supply - L3
hindgut : last 1/3 transverse colon to rectum
