excretion Flashcards
metabolic waste types
nitrogenous, organic acids, sulfates, phosphates, CO2
waste path out of body
cells, interstitial fluid, blood, lungs/kidneys/gills/liver/salt glands (mostly kidneys)
how much body water is ECF
26%
excretory and urogenital development
intermediate mesoderm, nephrotomes (with a nephron in each) segmented under segmented somites
nephron
2-layered cup of epithelium/bowmans capsule surrounds glomerulus (ball of capillaries) = renal corpuscle. attached to epithelial tube (renal tubule uses microvilli - proximal part absorbs, distal concentrates)
blood supply to glomerulus
arterioles both ways, high pressure, afferent is larger
podocytes
cells with finger like extensions which wrap around capillaries for filtration, keep in larger molecules. main body = diagphragma
mesangial cells
regulate blood flow in glomerulus, secrete inflammatory mediators and matrix fluid
capillaries next to renal tubule in diff groups
peritubular capillaries to… efferent renal vein and renal portal vein in birds, reptiles, chondrichthyes, just portal in teleosts and amphibians, just efferent in mammals (in mammals just 1 capillary with countercurrent flow)
nephron position thru orders
ammocoetes and larval amphibians - external glomeruli in coelum and filtrate is moved out by cilia; elasmobranchs, primitive teleosts, and some amphibians - internal but connected to coelum via passage; all other verts- separate compartment
nephron differentiation thru orders
(order of formation) pronephros - head kidneys, 12+ in agnathans, anamniotes, amphibians. 1-3 nonfunctional as adults for amniotes but starts development of archinephric duct for waste disposal in embryos. mesonephros - nonsegmented, have a gap btwn this and pro in amniotes, join with pronephros to form opisthonephros in anamniotes (advanced in fish and amphibians, front makes sperm); metanephros- invented for amniotes, where the ureteric bud forms/end of archinephric duct, grows into renal tubules and ureter.
mammal bladder origin
allantois
osmoregulation
maintenance of ionic balance
osmolarity of cell
300 mOsm. (1000 for seawater)
waste fixation methods
bony fish/water turtles - ammonia flushed out, sharks - urea storage, reptiles - uric acid, mammals - urea
osmoregulation in early chordates/agnathans
interstitial fluid is isosmotic to seawater, similar in hagfish but renal tubules flush water faster for more efficient NH3 disposal
hypoosmotic ECF
not enough solutes, water enters cell
hyperosmotic ECF
too many solutes, water leaves cell
renal corpuscles purpose
remove excess water/solutes from tissue, craniate innovation
osmoreg freshwater teleosts
gills excrete NH3, kidneys osmoregulate (hypoosmotic urine), renal corpuscle is large for flow and has cilia for movement after corpuscle and at intermediate segment. minimize water intake via mucus on skin, absorb salt via ionocytes in skin and gills
osmoreg saltwater teleosts
drink water, excrete salts. smaller corpuscle with no cilia and no intermediate segment to reduce flow. (hyperosmotic urine) many ionocytes to secrete salts. fish like salmon and eels have fresh and saltwater so can do both, regulated by hormones to kidneys
osmoreg in chondrichthyans
minimize water intake. cells isosmotic to seawater using urea buildup. large corpuscles to eliminate water, hyposmotic urine. rectal digitiform gland excretes salt. this urea tolerance character is seen as eggs due to lack of waste exchange, could be reason for evo.
osmoreg in amphibians
as larva, like freshwater fish. as adults, convert to urea and excrete hyposmotic urine bc their tubules are massive a la fish. thus they must stay wet
osmoreg in reptiles
make uric acid, urine is isosmotic to blood. renal corpuscles minimize water loss, small, no glomeruli. marine ones have salt glands. sea turtles no longer do this, they just excrete NH3
