EXCRETION Flashcards
excretion
- removal of wastes made by the body
how is water removed? (3)
- excreted as metabolic waste from respiration
- secreted in tears and saliva
- egested in faeces
functions of the kidney (2)
- excretion - removal of nitrogenous waste
- osmoregulation - controlling water potential of the body’s fluids by regulating water content
how is urea produced (3)
- dietary protein digested into amino acids and transported to liver
- deanimated in the liver and amino group converted to urea
- carried in plasma to liver and excreted in urine
kidney image
- nephron, cortex, medulla, renal artery, renal vein, pelvis, pyramid, renal capsule, ureter
fine structure image
glomerulus, efferent arteriole, bowman’s capsule, distal convoluted tubule, collecting duct, loop of henle (ascending/descending limb), vasa recta, proximal convoluted tubule, afferent arteriole
nephron in the kidney
blood filtering unit
path filtrate travels through kidney (4)
- through the afferent arteriole, from the renal artery, to the nephron
- seperates into capillaries at the glomerulus enclosed in bowman’s capsule
- filtered blood carried by efferent arteriole to capillary network around tubes/vasa recta capillary network around loop of henle
- diverted through nephron to collecting duct, pelvis, ureter
filtering layers of the glomerulus (4)
- thin wall of capillary, single layer of epithelial cells with fenestrae (pores)
- basement membrane with extracellular layer of proteins (glyoproteins/collagen) to act as molecular filter, selective barrier, sieve
- wall of bowman’s capsule make of squamous epithelial cells, podocytes, with pedcials wrapping around capillaries
- filtration slits between pedicals
where occurs in the bowman’s capsule? (2)
- ultrafiltration
- filtration under high pressure
diagram of bowman’s capsule
p235
what makes up filtrate (5)
- water
- glucose
- salts
- urea
- amino acids
what are too big to pass through membrane and remain in blood? (3)
- platelets
- blood cells
- large proteins
selective reabsorption (2)
- occurs along the proximal convoluted tubule/ PCT
- useful products reabsorbed into blood
how is the PCT adapted? (5)
- long w/ large SA and many nephrons
- cuboidal epithelial cells in walls w/ microvilli to increase surface area
- many mitochondria to produce ATP
- close capillaries
- tight junctions between cells preventing molecules diffusing back
selective reabsorption (4)
- salts reabsorbed by mostly active (but some passive) transport
- all glucose and amino acids reabsorbed by co-transport with sodium
- water by osmosis (bc reabsorbed ions lower water pot. of blood)
- urea/small proteins by diffusion, down steep gradient (bc. water loss left high conc.)
co-transport (6)
- glucose molecule + 2 Na+ bind to carrier/transporter protein
- carried across cell by facilitated diffusion
- dissociate from carrier
- diffuse across cell
- sodium diffuses into capillary
- sodium diffusion provides energy for secondary active transport of glucose into blood
glucose threshold (3)
- glucose being lost in the loop of henlé
- pancreas doesn’t secrete enough insulin (type i diabetes)
- insulin receptors damaged so liver does not respond to insulin as much (type ii)
where does water reabsorption occur?
- on the ascending/descending limbs of the loop of henlé
loop of henlé structure (3)
- ascending limb impermeable to water
- descending limb permeable to water, only slightly permeable to ions
- vasa recta, capillaries surrounding loop
- distal convoluted tubule leading into collecting duct
How reabsorption of water occurs (6)
- filtrate flows down descending limb, water flows out by osmosis into tissue fluid, into vasa recta
- simultaneously some Na+/Cl- diffuse into descending limb
- as filtrate gets down descending limb there is progressively less water and most conc. at base of the loop
- on ascending limb Cl-/Na+ actively transported out so water pot. climbs as it climbs from base
- more water diffuses out down the collecting duct (as it passes low water pot. medulla)
- becomes hypertonic (more conc.) than blood and is urine by bottom of collecting duct
counter-current multiplier (2)
- limbs of henle run side by side, flowing in opposite directions
- conc is progressively built up towards the apex
