lecture 7 Kidneys Flashcards
(22 cards)
what is the purpose of the kidney
- Maintaining extracellular fluid composition and volume
- Maintaining mass balance/clearance- everything that comes in the body must be removed.
- Filtration followed by reabsorption
- Secretion of some waste products
- Produce some hormones (erythropoietin)
- The kidneys together filter about 180 litres of fluid a day
they mainly dispose waster products and turn them into urine
external location of kidneys
left kidney is slightly higher than the right. Its near the liver, stomach and located near the spine. it doesn’t exist in isolation but is connected to renal vein, renal artery and ureter
internal location of the kidney and its parts
renal cortex, renal medulla, nephrons, renal artery-unfiltered blood in, renal vein- filtered blood out, renal pelvic, ureter-urine out, renal pyramid
how many layers does he kidney have and what are they
there are 2 layer and it’s the renal cortex and renal medulla.
what is the kidney made-up of (subunit) and where is it mostly located
kidneys are made up of nephrons which are tiny microscopic structures that is mostly in the renal cortex and some in the renal medulla. its bundled together in the renal pyramid and filters its contents in the renal pelvis to the ureter to the bladder
what are nephrons
they are microscopic tubes that fine tunes the composition of blood, keeping nutrients and filtering out anything else we don’t need
parts of the nephron
-renal corpuscle
- proximal convulated tubule
-loop of henle
-distal convoluted tubule
-collecting duct
renal corpuscle components and role
renal corpuscle is the site of the filtration of the blood. as the blood leaves the vessel and into the nephron, 20% of plasma is removed here. it has glomerulus which are a tangle of tiny capillaries and are porous- have holes to allow material to pass through easily. its surrounded by the Bowmans capsule which absorbs the fluid that comes out of the glomerulus. this is called ultrafiltration because there is water pressure pushing material out of the blood vessel. one of the vessel is a bit narrower on the exit which creates a pressure inside and force material out of the glamorous and into the Bowmans capsule to the nephron. it passes through a membrane filter from the membrane to the nephron
discuss how the filtration membrane of the glomerulus works.
it has three layers.
1. capillary lumen-outermost layer of the capillary. empty internal space.
2. capillary basement membrane
3. podocytes foot processes: octopus like that wraps around the glomerulus which has small spaces between them that allows water, glucose, ions to pass through (anything less than 3 nanometers) and keep larger molecules (proteins and blood cells)
measuring how well a material can pass through
introducing a substance around the body by drinking on injecting which goes through the bloodstream to the kidney, to the glomeruli filter and passes through the urine. you then compare the amount of substance in the body and the urine. we can use inulin- plant carbs and creatinine-protein byproduct. they do not interact with the body. we measure this by GFR=concentration in urine x urine flow rate ( ml/min) divided by concentration in blood
proximal convulated tubule purpose and how it does this.
where 70% of the removed plasma is retained back into the system. its covered in microvilli (bigger surface area) for better reabsorption. it does this through active transport to push glucose back into the blood stream through transmembrane protein- cotransport (pumped out with sodium). because its active, there is no glucose left in the urine.
how does water concentration in the loop of henle not reverse if the solute concentration as you go up decreases
the ascending limb has thicker walls to prevent movement of water.
loop of henle
goes down to the medulla of the kidney. has descending limb which is thinner and ascending limb that’s thicker. its function is to reduce the water content of the urine, potassium and sodium. the concentration of the solute outside the henle as you go down increases. this is to allow the water to come out (osmosis) to reach equilibrium. on its way up, on the ascending tube, there are active transports to remove sodium and potassium. loop of henle varies in size. only about 15% of the nephron go right in the medulla. if your dehydrated the long loops of henle will work to concentrate the urine.
what are the hormones that control water
aldosterone and Anti diuretic hormone
describe the hormone aldosterone
its a hormone that control the balance of water. its produced by the adrenal gland (on top of the kidney). released in response to low blood pressure if the blood is not putting enough pressure to the arteries. it acs on the kidney to increase reabsorption of sodium in the distal convoluted tubule and collecting duct. this means water will also flow out to even it out. this increases the water volume of the blood and provides about pressure in the bloodstream
describe the hormone Anti- diuretic hormone/ vasopressin
produced by the hypothalamus and is released in response to High solute concentration in blood stream. it acts on the collecting duct and increase reabsorption of water by inserting aquaporins into the walls of the collecting duct to allow more water to flow into the blood stream, decrease solute and increase blood volume.
how does coffee or alcohol affect ADH
can cause dehydration because alcohol inhibits the effect of it and caffeine inhibits its release.
distal convulate tubule
similar to proximal consulate tubule. similar to proximal convuluted tubule but is shorter and with fewer microvilli. it uses the potassium pump to remove excess potassium into the nephron under the control of aldosterone and sodium into the bloodstream. it also secretes hydrogen ions and protons which balances the ph levels of blood.
collecting duct
delivers urine into the renal pelvis. it also works in balancing water through ADH
what happens to substances that come out of the nephrons
there are blood vessels that are right next door to it
renal threshold
Concentration of blood component above which the kidneys remove in the urine.
Renal threshold of glucose 10mmoles/litre and mean blood glucose is 4.4-7.2mmoles/l. Anymore will come out in the urine.
composition of urine
95% water
Urea.2.5%. Biproduct of protein metabolism. Does not make urine yellow. Its colourless
Na+ largest component after urea.
Urochrome: by product of haemoglobin breakdown, originates in liver. It changes colour because of the water concentration.
