GASTRO

Gastroenterology:

Hormones: 

Glucagon Like Peptide 1: 

• SECRETED: L cells (small intestine)
• FUNCTION: Increases sensitivity to glucose => triggered by hexose or fat

GIP (glucose dependant insulinotrophic peptide)

• SECRETED: K cells (mucousal)
• FUNCTION: Insulin secretion

Pancreatic polypeptide

• SECRETED: PP cells (pancreas)
• FUNCTION: Fat stimulates this

Peptide YY

• SECRETED: L cells
• FUNCTION: Inhibitory => red motility and gall bladder contraction

Endocrine hormones

• SECRETED: Enteroendocrine cells (base of intestinal crypts along GI)
• FUNCTION: Hormone secretion

Neurocrine hormones

• SECRETED: Post-ganglionic non-cholinergic neurones ENS
• FUNCTION: Impacts nerves

Examples: NEUROCRINE HORMONES 

• VIP (Vasoactive intestinal peptide) = relax smooth muscle
• GRP (gastrin releasing peptide) = gastrin release
• Enkephalin = increase smooth muscle tone

Somatostatin

• SECRETED: Endocrine D cells (gastric and intestinal mucousa + pancreas)
• ROLE: Inhibits GI tract

Gastrin

• SECRETED: Upper small intestine + gastric antrum (G cells)
• ROLE: Stimulated by vagus nerve, aa or distention => gastric acid secretion

Cholecystokinin (CCK)

• ROLE: Binds to CCK receptor on gall bladder => opens sphincter of oddi and leads to gall bladder ejection of bile

L cells FOUND = ileum, colon and rectum

Gastric secretion:

STAGES: Cephalic => gastric => intestinal

• Cephalic: senses detect food smell etc => release of gastrin and digestive enzymes via PNS stim enteric plexus
• Gastric: food arrives @ stomach => distention => inhibited PNS and ENS => inhibited gastrin and secretion of inhibitory hormones + secretion of secretin in intestine (increase pH)
• Intestinal: drop in pH in duodenum => chemoreceptors generate AP => inhibited PNS and ENS + gastric secretion => secretin + inhibitory hormone release

Hirschsprung’s disease: absence of ganglion in myenteric plexus

Hepatobiliary System:

Components of bile:

• Woah Babe, **** liam innit => water, bile salts, fatty acids, lecithin, inorganic ions

Uses of Bile:

• cholesterol homeostasis, 1o removal of cholesterol, lipids and lipid sol vits absorption + toxic sub

Xenobiotics: a foreign molecule the body does not produce

Production of bile

• 1o => hepatocytes (sec bile acids, lipids and ions)
• 2o => cholangiocytes => alters pH of bile

2o PRODUCTION OF BILE: H2O drawn into bile => luminal glucose + organic acid reabsorbed => HCO3- and Cl- actively transported into bile by CFTR => IgA exocytosed

BILE Transporters

• Basolateral: imports substances to put in bile => hepatocytes
• Apical: exports => bile

basolateral: bile salt uptake

• OATPs (organic anion transporting peptide)
• NTCP (Na+ taurocholate cotransporting peptide)

Apical:

MDRP (multi-drug resistant peptides):

• MDRP1 = +vely charged metabolite
• MDRP 2+3 = -vely charged metabolite
• MDRP 3 = excretes phosphatidylcholine

BSEP (bile salt excretory pump) => converts bile acid to bile

Bile salts:

Structure = planar (hydrophobic and hydrophilic heads => amphipathic)

• hydroPHILLIC = (filly likes foxy ladies + OUT but his chances dissolve like water) => hydroxyl and carboxyl groups and outwards + dissolves in water
• hydroPHOBIC = nucleus and methyl = inwards + dissolves in FAT

bile salts: reabsorbed in terminal ileum by Na+/bile salt cotransport NaK+ATPase => bile and rest converted to 2o bile salts

Primary => prod in liver => cholic…