5.3 Kidney Structure, Ultrafiltration & Reabsorbtion Flashcards
The kidneys are supplied with blood from which arteries?
Renal arteries from abdominal aorta
Blood is removed from the kidneys by what?
The renal vein draining into the inferior vena cava
How much blood passes through the kidneys every minute?
90 - 120cm3
How much blood does the kidneys filter a day and how much urine is produced?
Blood - 180dm3
Urine - 1-2dm3
Urine leaves the kidneys via what?
The ureters it’s collected in the bladder when full the sphincter opens and urine passes through urethra
What is the cortex?
Dark outer layer
Where filtering of blood takes place
Sense capillary network
What is the medulla?
Lighter region
Contains tubules of nephrons forming pyramids and collecting ducts
What is the pelvis?
Central chamber where urine collects before passing down ureter
What do the nephrons do?
Filter blood
Remove urea
Balance mineral ions and water balance
What is the bowmans capsule and what does it contain?
Cup shaped structure
Contains glomerulus - tangle of capillaries
What is the proximal convoluted tubule?
1st coiled region in cortex where many substances needed are reabsorbed into blood
What is the loop of Henle?
Loop of tubule in the medulla creating a region of high solute conc in tissue fluid
What is the distal convoluted tubule?
2nd twisted tubule controlling water balance of the body, ph regulation and ion balance
ADH permeable walls
What is the collecting duct?
Where urine passes down from medulla to pelvis
Water balance takes place here walls are ADH sensitive
What is ultrafiltration?
Removal of nitrogenous waste and osmoregulation of blood resulting it tissue fluid formation in capillary beds
(Ultrafiltration) 1. The glomerulus is supplied with blood from where?
Arteriolar from Renal artery
(Ultrafiltration) 2. Blood leaves the glomerulus through where? What does this do?
Narrow efferent arteriole
Creates a lot of pressure in the capillaries of the glomerulus
(Ultrafiltration) 3. What does the high pressure do?
Forces blood through capillary wall (sieve)
(Ultrafiltration) 4. Blood then passes through where?
Basement membrane - made up of collagen fibres and proteins (2nd sieve)
(Ultrafiltration) 5. Most plasma contents pass though the basement membrane but what happens to blood cells and proteins?
Retained in capillaries due to their size
(Ultrafiltration) 6. What are the cells in the walls of the bowmans capsule called and what do they have?
Podocytes
Extensions called pedicels
(Ultrafiltration) 7. What do pedicels do?
Wrap around capillaries forming suits ensuring any proteins or blood cells that have managed to get through don’t go into the tubule
(Ultrafiltration) 8. The filtrate entering the capsule contains what?
Glucose, salt, urea and other substances
(Ultrafiltration) 9. What is the vol of blood filtered through known as?
The glomerular filtration rate
(Reabsorption) as well as removing urea what does ultrafiltration remove from blood?
Glucose salt water
Necessary substances
(Reabsorption) what is the main function of the nephron?
To return filtered substances to the blood
In the proximal convoluted tubule what are moved back to the blood by active transport?
Amino acids
Glucose
Vitamins
Hormones
In the proximal convoluted tubule how much sodium chloride and water is reabsorbed?
85%
In the proximal convoluted tubule Na moves out by which process?
Active transport
In the proximal convoluted tubule what do Cl and water do?
Follow Na passively down concentration gradients
The cells lining the proximal convoluted tubule are lined with what? What does this do?
Microvilli
Increases surface area over which substances can be reabsorbed
The cells lining the proximal convoluted tubule have many what and why?
Mitochondria
To provide ATP for active transport
substances removed from nephron diffuse into capillaries down steep conc. gradients maintained by what?
constant flow of blood through the capillaries
filtrate reaching the loop of henle is isotonic to tissue fluid and blood, what does this mean?
same concentration
the loop of henle is the section of the kidney tubule which allows mammals to do what?
produce urine more concentrated than their blood
what is one feature of the loop of henle that is central to its function?
different areas of the loop having different permeabilities to water
the loop acts as a countercurrent multiplier what does this mean?
using energy to create concentration gradients resulting in the movement of substances e.g water
the descending limb is the region where water moves where?
out of the filtrate down a concentration gradient
is the descending limb permeable to water?
upper area is impermeable
lower are is permeable
as filtrate travels down the descending limb what happens to the water?
diffuses into surrounding tissue fluid by osmosis, then diffuses into the blood of surrounding capillaries
what is the descending limb not permeable to and what does this mean?
Na- and Cl- ions so no active transport takes place here
filtrate reaching the bend of the loop of henle is very concentrated, and is what in comparison to blood in capillaries?
hypertonic
is the first section of the ascending limb permeable or impermeable to Na- and Cl- ions?
permeable - they move out the concentrated solution by diffusion down a concentration gradient
in the second section of the ascending limb what happens to Na- & Cl- ions?
they are actively pumped into the medulla tissue, increasing ion concentrations in the medulla tissue
what is the ascending limb impermeable to?
water so H20 cant follow Na and Cl down a concentration gradient
what happens to the fluid left in the ascending limb and the tissue fluid of the medulla?
filtrate left in the ascending limb becomes more dilute
tissue fluid of medulla develops high conc of ions
what is the high conc of ions in the medulla essential for?
the kidney to produce urine more concentrated than the blood
fluid reaching the top of the ascending limb is hypotonic to the blood -what does this mean?
lower osmotic pressure
what happens in the distal convoluted tubule?
balancing of H20 needs of the body
the permeability of the walls of the distal convoluted tubule and collecting duct varies with what?
ADH levels
how is the distal convoluted tubule adapted for active transport?
many mitochondria
if the body lacks salt what can the distal convoluted tubule do?
actively pump Na ions out with CL following passively down a conc gradient
what happens at the collecting duct?
concentration and volume of urine is determined
what does water do as it passes through the collecting duct?
diffuses out down a concentration gradient as it passes through medulla resulting in it becoming more concentrated
why can water be removed from the collecting duct along its length?
because the level of Na ions in the surrounding fluid increases through the medulla
what is one factor the ability to produce concentrated urine depends on?
length of loop of Henle
which mammals tend to have long loops of henle?
desert animals to conserve more water
fish have no loop of henle so they cant do what?
produce urine more concentrated than their blood
