Biochem 2 Flashcards
What type of acidosis is renal tubular acidosis ass with?
hyperchloraemic metabolic acidosis (normal anion gap)
What is Type 1 RTA (distal)?
- K?
- complications?
- causes?
- can’t secrete H+ in distal tubule (can’t generate acid urine)
- hypokalaemia
- nephrocalcinosis, renal stones
- idiopathic, RA, SLE, Sjogrens, amphotericin B toxic, analgesic nephropathy
What is Type 2 RTA (proximal)?
- K?
- complications?
- causes?
- decreased HCO3- reabsorption in proximal tubule
- hypokalaemia
- osteomalacia
- idiopathic, part of Fanconi’s, Wilson’s, cystinosis, outdated tetracyclines
What is Type 4 RTA?
- K?
- causes?
- reduced aldosterone leading to reduced excretion of ammonium in proximal tubules
- hyPERkalaemia
- hypoaldosteronism, diabetes
Where is iron absorbed?
What are the types?
What increases/decreases absorption?
- 10% dietary iron absorbed in UPPER SMALL intestine and is regulated according to body’s need
- Fe2+ (ferrous) absorbed better than Fe3+ (ferric)
- inc by vit C, gastric acid
- decreased by PPIs, tetracycline, gastric achlorhydria, tannin (tea)
Iron distribution?
total body iron = 4g Hb = 70% ferritin & haemosiderin = 25% myoglobin = 4% plasma iron = 0.1%
How is iron transported?
Stored?
Excreted?
- transported as Fe3+ bound to transferrin in plasma
- stored as ferritin in tissues
- excreted via intestinal tract following desquamation
Where is gastrin secreted?
What stimulates gastrin secretion?
What are the actions of gastrin?
G cells in stomach antrum secrete gastrin
- stimulated by stomach distension, vagus nerves, luminal peptids & amino acids
- inhibited by low antral pH & somatostatin
Gastrin actions:
- increase HCL, pepsinogen & IF secretion
- increase gastric motility
- stimulates parietal cell maturation
Where is CCK (GI hormone) secreted?
What stimulates CCK secretion?
What are the actions of CCK?
I cells of upper small intestine secrete CCK in response to partially digested proteins & triglycerides
CCK:
- increases secretion of enzyme-rish fluid from the pancreas
- increases gallbladder contraction & relaxation of sphincter of Oddi
- decreases gastric emptying, trophic effect on pancreatic acinar cells
- & induces satiety
Where is secretin secreted?
What stimulates secretin secretion?
What are the actions of secretin?
S cells in upper small intestine secrete secretin
- in response to acidic chyme & fatty acids
- it increases secretion of bicarbonate-rich fluid from the pancreas & hepatic duct cells
- decreases gastric acid secretion & trophic effect on pancreatic acinar cells
secretin stimulation test can be used as a test for pancreatic function e.g. in chronic pancreatitis
Where is VIP secreted?
What stimulates VIP secretion?
What are the actions of VIP?
Small bowel & pancreas secretes VIP in response to neural stomulation
- leading to stimulation of secretion by the pancreas & intestines
- & inhibits acid secretion
Where is somatostatin secreted?
What stimulates somatostatin secretion?
What are the actions of somatostatin?
D cells in the pancreas & stomach secrete somatostatin
- in response to fat, bile salts & glucose in the intestinal lumen
Leading to:
- decreased acid & pepsin secretion
- decreased gastrin secretion
- decreased pancreatic enzyme secretion
- decreased insulin & glucagon secretion
- inhibits trophic effects of gastrin
- stimulates gastric mucous production
A cause of metabolic alkalosis along with excessive loss of sodium, potassium and chloride. Polyhydramnios is typical in the neonatal form??
Bartter’s syndrome
