Function of kidneys (1)

What is the glomerulus supplied with?

Blood by a relatively wide afferent (incoming) arteriole from the renal artery

How does blood leave and what happens as a result?

Blood leaves through a narrower efferent (outward) arteriole and as a result there is considerable pressure in the capillaries of the glomerulus. This forces blood out through the capillary wall - acts like a sieve

Where does fluid pass through?

Basement membrane - made up of a network of collagen fibres and other proteins that make up a second ‘sieve’. Most of the plasma contents can pass through this membrane, but blood cells and proteins are retained in capillary due to their size

What is the first layer blood has to pass through to get to the bowman’s capsule?

Endothelium,which has pores to allow the passage of small molecules through

What is the second layer blood has to pass through through to get to the bowman’s capsule?

Basement membrane (network of collagen fibres) that stops large molecules and cells from passing through

What is the third layer blood has to pass through through to get to the bowman’s capsule?

Epithelium, they have pedocytes which have extensions called pedicels that wrap around capillaries, forming slits that make sure cells,platelets and large plasma proteins that get thru epithelial cells + basement membrane don’t get thru tubule

Why can’t podocytes undergo mitosis?

Already differentiated, shape is too irregular, cytoskeleton can’t function, would alter number of gaps

What is in the filtrate that enters the capsule?

Glucose, salt, urea and NaCl

How does reabsorption in the proximal convulted tubule occur?

From the bowman’s capsule, the filtrate passes into PCT and sugar, amino acid, vitamins, hormones, salt, water are reabsorbed back into the blood by active transport

How are the cells of the proximal tubule adapted for absorption?

Covered in microvilli (increases SA), many mitochondria to provide ATP for active transport, channels proteins for glucose or amino acids to enter cells with sodium ions by facilitated diffusion

What does the loop of henle act as?

A countercurrent multiplier, uses energy to produce conc gradient that result in the movement of water from 1 area to another

Where does filtrate lead from?

Proximal tubule, and water moves out of the filtrate down a conc gradient. Upper part is impermeable to water, lower part is permeable

What happens to the conc of NA+Cl ions in the medulla tissue fluid?

it originally has a high solute conc, then water movement from the filtrate in the descending limb occurs. water potential is maintained at a lower water potential then due to movement of ions out of ascending limb

What happens to filtrate entering the descending limb of loop of henley?

It is isotonic with the blood, as it travels down water passes out of the limb into the tissue fluid by osmosis down a conc gradient, then moves down a conc gradient into blood of capillaries

What is the descending limb not permeable to?

Na and Cl ions so no active transport occurs in it. Fluid that reaches ascending limb is very concentrated

What happens in the lower part of the ascending limb compared to the upper part?

Na and Cl diffuse out, in the upper part they move out by active transport into the medulla, producing high Na and Cl ion concs in the medulla

Overall, what is the ascending limb impermeable to?

Water, so water can’t follow Na and Cl ions down conc gradient

What happens to fluid left in the ascending limb?

Becomes dilute, and the medulla tissue fluid develops v high conc of ions

What happens when the dilute fluid reaches the top of the ascending limb?

It enters distal tubule and collecting duct