Excretory System Flashcards
What type of waste is eliminated in excretory system?
nitrogenous waste (urea/uric acid)
cnidaria excretion
diffusion into surrounding water
annelids
two nephridia in each body segment; urea passed from small capillaries to nephridia; waste exits worm through nephridia and holes (pores) in the skin
arthropods
Malphighian tubules are bathed in blood (open circ. system), uric acid collects in the tubules from blood and empties into the digestive tract
What happens to urea without water?
It crystallizes into uric acid which is excreted with the solid waste.
transfer of urine in humans
Kidney –> Ureter –> Bladder –> Urethra
nephron
tiny tubule that filters blood within the kidney
passage of blood/filtrate through structures
Blood in through afferent arteriole (type of renal artery) –> Glomerulus (collection of capillaries –> blood leaves through efferent arteriole, filtrate goes through Bowman’s capsule (surrounding glomerulus) into… –> proximal convoluted tubule –> descending loop of Henle –> ascending loop of Henle –> distal convoluted tubule –> collecting duct –> ureter…
What word should we associated with kidney (r….)?
renal!
glomerulus
cluster of capillaries that physically squeezes blood through a “sieve,” resulting in cleaned but much thicker blood and filtrate (urea + water + glucose, salt, amino acids) FILTRATION
Bowman’s capsule
This is where the filtrate gathers after going through the glomerulus “sieve.”
proximal convoluted tubule
REABSORPTION – salt, water, amino acids, glucose re-enter blood; Now it is called URINE and has lost 75% water.
descending loop of Henle
goes from outer region of kidney (cortex) into medulla; walls of this part are water-permeable but not salt-permeable; MEDULLA has high salt concentration, so water from urine is drawn out into medulla because of this concentration gradient – now urine has lost 94% of water
regions of kideny
cortex (outer) & medulla
ascending loop of Henle
salt-permeable, so the salt from urine goes into medulla, leaving only 4% of the original salt behind
distal convoluted tubule
salt is pumped out and water follows, leaving only 3% of original water left and negligible amount of salt (filtration and reabsorption) + SECRETION: Hydrogen and Potassium ions are actively pumped into urine for release.
ALDOSTERONE
collecting duct
extends deep down into the medulla
It is here where the amount of water loss can be controlled. Up to 75% of the remaining water CAN be lost, but levels of ADH control permeability of the duct’s walls
If ADH levels are low, then less water loss, and vice versa.
IN ADDITION, some urea is lost into medulla at the bottom to maintain high ion concentration of medulla.
ADH
antidiuretic hormone, secreted by posterior pituitary gland
aldosterone
produced in adrenal cortex, increases sodium and water reabsorption in distal convoluted tubule
kidney enzymes to control blood pressure
kidneys release renin –> produces angiotensin II –> increases blood pressure and aldosterone amounts, therefore increasing blood volume and therefore pressure
