The kidney Module 5 Flashcards
Explain the step of blood reaching the site of ultrafiltration in the kidney?
Blood from renal artery enters smaller arterioles in the cortex
Each arteriole splits into a structure called the glomerulus (bundle of capillaries looped inside a hollow ball called the bowman’s capsule where ultrafiltration occurs
Explain the steps in ultrafiltration of the kidney?
The afferent arteriole (takes blood into the glomerulus), and the efferent arteriole (takes blood out of the glomerulus), efferent smaller in diameter, so pressure of blood in glomerulus is higher
The high pressure forces liquid and small molecules in the blood out of the capillary and into the bowman’s capsule
Small substances pass through 3 layers to reach the bowman’s capsule, the capillary wall, the basement membrane, and the epithelium of the bowman’s capsule
Larger molecules such as proteins can’t pass through into bowmans caspule, so stay in the blood
Explain the process absorption in the kidney?
Takes place as the filtrate flows along the Proximal convoluted tubule, the loop of Henle and the distal convoluted tubule
Useful substances leave the tubules of the nephrons and enter the capillary network that wraps around them
Epithelium of PCT has microvilli to increase SA
Useful solutes such as glucose, amino acids, vitamins and some salts reabsorbed along PCT via active transport and facilitated diffusion
Also some urea is reabsorbed via diffusion
Water enters blood by osmosis because water potential of blood lower than that of the filtrate, occurs in loop of Henle, DCT, and the collecting duct
Filtrate that remains is urine, which passes along the ureter to the bladder
What us urine made up of?
Water and dissolved salts
Urea
Hormones and excess vitmamins
What doesn’t urine contain and why?
Proteins and blood cells they’re too big to be filtered out of the blood
Glucose, amino acids and vitamins as have been reabsorbed back into the blood
What’s the loop of Henle made up of?
The descending limb first and then the ascending limb second
Explain the counter current multiplier mechanism in the loop of Henle?
Near the top of the ascending limb, Na+ and Cl- ions are actively pumped out into the medulla. The ascending limb is impermeable to water, so water stays inside the tubule, but creates a low water potential in the medulla
Because there’s lower water potential in the medulla than in the descending limb, water moves from the descending limb and into the medulla by osmosis. This makes the filtrate more concentrated
Water in the medulla is reabsorbed back into the blood via a capillary network
Near the bottom of the ascending limb, Na+ and Cl- ions diffuse out into the medulla further reducing the water potential, as impermeable so water can’t follow
All these stages cause water to move out of the collecting duct via osmosis and into the medulla via osmosis
Why different animals have different length loops of henle?
The longer the loop of Henle, the more water is able to be reabsorbed from the filtrate. As more ions pumped out, creating a lower water potential in the medulla, so more water moves out
Useful for desert animals
What is the water potential of the blood measured by?
Cells called osmoreceptors in the part of the brain called the hypothalamus
What happens when osmoreceptors are stimulated by a low water potential in the blood?
Hypothalamus sends nerve impulses to the posterior pituitary gland to release the hormone ADH
ADH makes the walls of the descending limb more permeable to water, so more water reabsorbed from these tubules into the medulla and into the blood by osmosis
What happens when you are dehydrated?
Water content of the blood drops, so it’s water potential drops
This is detected by osmoreceptors in the hypothalamus
Posterior pituitary gland is stimulated to release more ADH in the blood
More ADH means that the DCT and collecting duct are more permeable, so more water is reabsorbed into the blood by osmosis
A small amount of highly concentrated urine is produced
What happens when your hydrated?
Water content of blood increase, so water water potential increases aswell
Detected by osmoreceptors in the hypothalamus
Posterior pituitary gland is stimulated to release less ADH
Less ADH means that the DCT and collecting duct are less permeable, so less water is reabsorbed into the blood via osmosis
Large amount of dilute urine is produced
How can kidney failure be detected?
Measuring the glomerular filtrate rate (GFR), low rate shows there is a problem
How can kidney infections cause kidney failure?
Causes swelling of the kidneys, which can damage the cells
How can high blood pressure cause kidney failure?
Can damage the glomeruli, as capillaires can get damaged if pressure is too high
This means larger molecules such as proteins can reach the urine
