kidneys&Excretion Flashcards
three processes of the kidneys
ulrtification
selective re absorption
production of urine
what are nephrons
long tubules along with the bundles of capillaries where the blood is filtered, around one million in each kidney
what is ultrafiltration
filtering of substances out of the blood at the molecular level
describe the process of ultrafiltration
blood enters the AFFERENT arteriole under high pressure(arriving at glomerulus)
the difference in diameter of the arterioles increases blood hydrostatic pressure in the glomerulus
so fluid/filtrate is forced out into the bowman’s capsule(low pressure)
differed between affluent effluent arterioles
wider diameter in affluent
smaller diameter in effluent
similarities between ultrafiltration and tissue fluid
-both in capillaries
-larger mols(proteins/erythrocytes)remain in the blood
-many mols(water, sugar, ions) are reabsorbed back into capillaries
-hydrostatic pressure greater than oncotic
-neutrophils can pass through both
what’s the basement membrane
a mass of collagen fibres and glycoprotein filters, which stops erythrocytes and argue molecules (proteins) passing through
purpose of gaps in squamous endothelial cells of capillaries
allow small substances through but stop erythrocytes from passing through
what are podocytes
epithelial cells in bowman’s capsule with extensions called PEDICLES, which ensure gaps to allow some substances through but not cells, platelets &large plasma proteins
differences between tissue fluid and ultrafiltration
ultrafiltration:
-filtrate enters BC then PCT
-blood filtered through 3 layers
-knot of capillaries
tissue fluid:
-tissue fluid enters intracellular space and bathes body tissues
-molecules that are not reabsorbed by capillaries either =enter cells or form lymph
-blood filtered through 1 layer
-network of capillaries
describe the process of selective reabsorption
1.Na ions and glucose(and amino acids) enter the cells of the PCT through co-transport proteins
2)water potential of cell is lowered so water enters the cell by osmosis down a water potential gradient
3)NA ions are pumped out of the cell into the blood and K ions go in (using atp), glucose goes into the blood capillary by facilitated diffusion, sometimes it can be actively transported into blood
4)water potential of blood lowered so water enters blood down water potential gradient by osmosis
5)large molecules are remed by endocytosis
the role of the loop of henle
create a low water potential (high solute conc)in the tissue fluid around the nephron.
descending limb is ermm able to water, so water is removed from here. the ascending limp is impermeable to water, ions leave via facilitated diffusion at her bottom and by active transport at the top
what’s a counter current multiplier
where fluid flows in opposite directions, in two vessels close to one another.
this maximises the concentration gradient that can be built up between the two, all the was along them
what’s osmoregualtion
maintains a constant water potential of the blood, despite changes in the level of water and salt intake
the role of the hypothalamus in thermoregulation
hypothalamus contains osmoreceptors which signal specialised neurosecretory cells. a fall in WP causes the release of hormone ADH from pituitary gland. ADH travels in the blood to the kidneys, attaching to ADH receptors, activating the intracellular enzyme phosphorylase. this causes vesicles containing aquaporins to fuse with the plasma membrane, reducing water loss by increasing the permeability of the collecting duct a the DCT
