15.5 The structure and function of the mammalian kidney Flashcards
What does the renal artery carry
Blood to the kidneys to be filtered
What does the renal vein carry
Filtered blood away from the kidney
What does the ureter carry
Urine from the kidney to the bladder
What’s the pelvis of the kidney
It’s a Central chamber where urine collects before entering ureter
What’s a nephron
TUBULES making up the main FUNCTIONAL STRUCTURES of the KIDNEY.
What’s the bowman’s capsule
A CUP-SHAPED structure containing GLOMERULUS it’s the Site of ULTRAFILTRATION.
What’s a glomerulus
Entangled capillaries found in each Bowman’s capsule
What’s the proximal convoluted tubules and what occurs there
1st twisted section of nephron after Bowman’s capsule, sélective réabsorption occurs here
Outline the process of selective réabsorption in the PCT
Na+ actively transported out of pct cell by sodium pump into tissue fluid
- concentration of ions in pct cell ￬
Na+ & glucose in filtrate move into pct cell by facilitated diffusion using cotransport protein
- concentration of glucose in pct cell ￪
Glucose diffuses from pct cell ⟶ surrounding capillaries
What are the ascending and descending limbs permeable to
DESCENDING: permeable to water molecules only
ASCENDING: permeable to ions only, Na+ Cl-
What’s the role of the ascending limb
to create a water potential gradient
in the tissue fluid
for water to move out of the descending limb by osmosis.
(Done by active transport of Na+ Cl- out, since permeable to ions.)
Which is thinner the afférent or efferent arteriole
The efferent is thinner
Outline the process of ultrafiltration
The glomerulus is supplied with blood from the relatively wide afferent arteriole & leaves through the narrower efferent arteriole - resulting in considerable pressure which forces blood out through the capillary wall, like a sieve
The fluid then passes through the basement membrane (made up of collagen fibres) which acts as a second sieve
Podocytes also act as an additional filter, with pedicels preventing any cells, platelets, or large plasma proteins which made it through the epithelial cells and basement membrane from entering the tubule itself
Adaptions of the glomerulus for ultrafiltration
Epithelial cells
- Basement membrane
- Podocytes/Pedicels
What’s reabsorped into the proximal convoluted tubules
In the PCT all of the glucose, amino acids, vitamins and hormones are moved from the filtrate back into the blood by active transport
Some mineral ions and water are reabsorbed
The filtrate reaching the loop of henle from the PCT is isotonic with the tissue fluid surrounding the tubule and isotonic with the blood
Length of loop of henle in desert animals
Longer so move ions can move out to create more of WPG so more H2O moves out of the blood
Adaptions of the PCT
Microvilli and foldings to increase the surface area
Mitochondria move ATP for transport
What’s the main role of the distil convoluted tubules
The main role of the distal convoluted tubule is to reabsorb water and salts, to make final adjustments to the filtrate that will enter the collecting ducts.
It can also help to control the pH of the blood by selecting which ions to reabsorb.
What does ADH do
Control The permeability of the walls of the distal convoluted tubule
Descending limb vs ascending limb
The descending limb:
Filtrate travels through here first
It is narrow
It has thin walls that are highly permeable to water but impermeable to ions
The ascending limb:
1 Filtrate travels through here after it passes through the descending limb
2 It is wider than the descending limb
3 It has thick walls that are impermeable to water but permeable to ions
The process of selection réabsorption in the loop of Henle
. At the top of the ascending limb, sodium ions are actively pumped into the medulla.
This lowers the water potential of the medulla, causing water to move out of the nephron by osmosis from the descending limb
As water moves out, the filtrate becomes more concentrated. This causes sodium ions to move out of the nephron at the start of the ascending limb, down their concentration gradient by facilitated diffusion
This lowers the water potential of the medulla even further, causing water to move out of the DCT and collecting duct by osmosis.
Water that has moved into the medulla eventually moves into the capillary.
What does ADH do and when
Osmoreceptors in the hypothalamus detect a drop in blood water potential.
The hypothalamus signals to the posterior pituitary gland to secrete ADH.
ADH causes the walls of the DCT and collecting duct to become more permeable to water (by the incorporation of more aquaporins into the membranes of the cells that line these parts of the nephron).
More water moves by osmosis out of the DCT/collecting duct and reabsorbed into the bloodstream, increasing its water potential.
A smaller volume of concentrated urine is produced.
