Excretion Flashcards
Define excretion
Removing metabolic waste like CO2 and nitrogenous byproducts
Why is excretion important?
Maintains pH balance
Regulates osmotic pressure
Describe the gross structure of the liver
Liver lobules (hepatocytes arranged into rows and separated by connective tissue)
Hepatic vein takes blood AWAY from liver. Its attached to the hepatic portal vein which contains products of digestion
Hepatic artery supplies liver with oxygenated blood through the sinusoids
Bile Duct transports bile to gall bladder
What are the functions of the liver?
Stores glycogen, and site of guconeogenisis, glycolysis and glycogenisis
Deaminates excess amino acids
Ammonia is detoxified by addition of CO2 in ornithine cycle
Also detoxifies other chemicals
State the gross features of the mammalian urinary system
Kidneys
Renal vein
Renal artery
Ureter
Urethra
Bladder
Describe the gross structure of the mammalian kidney
Fibrous capsule protects the kidney
Cortex is the outer region containing bowman’s capsule, convoluted tubules and blood vessels
Medulla is the inner region containing collecting ducts, loop of Henle and blood vessels
Describe the blood vessels associated with the nephron
Wide afferent arteriole from renal capsule, forms glomerulus
Glomerulus is a branched knot of capillaries which combine to form efferent arteriole
Describe the sections of a nephron
The bowman’s capsule- at start of the nephron, surrounds glomerulus and has an inner layer of podocytes
PCT- series of loops surrounded by capillaries
Loop of henle- extending from the cortex into medulla
DCT- similar to PCT but fewer capillaries
Collecting duct- leads into pelvis of kidney
Describe the process of ultrafiltration
High hydrostatic pressure in the glomerulus forces small molecules out of capillaries AGAINST a osmotic gradient
Basement membrane acts as a filter. Blood cells are large molecules like proteins, remain in the capillary.
How is the Bowman’s capsule adapted to it’s function?
Fenestrations between epithelial cells
Fluid can pass between and under the folded membrane of podocytes
What is selective reabsorption in the nephron?
Useful molecules are reabsorbed back into the blood in the PCT
What happens in the loop of Henle?
Active transport of Na+ and Cl- out of ascending limb
Water pot. of interstitial fluid decreases
Osmosis of water out of descending limb
Water pot. of filtrate to decrease going down the descending limb (lowest in the medullary region and highest at the top of the ascending limb)
Define osmoregulation
Control of plasma water potential via negative feedback
Explain the role of the hypothalamus in osmoregulation
Osmosis of water out of the osmoreceptors in the hypothalamus causes them to shrink
This triggers the hypothalamus to produce ADH
Explain the role of ADH in osmoregulation
Forms hormone receptor complex on cell membranes in the collecting duct. Triggering cAMP as secondary messenger.
This triggers processes that increase reabsorption of water so the urine ebcomes more concentrated.
