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14.2 The structure of the kidney - Coggle Diagram
14.2 The structure of the kidney
Passage of blood
Blood enters the kidney via the renal artery into an afferent arteriole
Blood passes through afferent arteriole into the glomerulus
Capillaries of glomerulus rejoin to form an efferent arteriole
Efferent arteriole branches off to form network of capillaries that follows the nephron to absorb other substances
Capillary network joins together to form renal vein
Ultrafiltration
Occurs in the glomerulus and Bowman's capsule
Glomerular capillaries and Bowman's capsule are separated
Endothelium
Made up of endothelial cells
Perforated by thousands of membrane-lined circular holes which are 60-80nm diameter
Basement membrane
Network of collagen and glycoproteins
Epithelium
Made up of epithelial cells called podocytes
Finger-like projections with gaps in between
Basement membrane stops large proteins (>69000Mr) from passing and acts as a filter
Whole cells are blocked by the endothelium as they cannot pass through the perforations
Rate
125cm3/min for all glomeruli in both human kidneys
Afferent arteriole narrows as it nears the glomerulus, increasing the pressure
Large proteins cannot pass through basement membrane so solute concentration is higher in plasma than glomerular filtrate
High pressure outweighs low solute concentration and water moves down pressure gradient into Bowman's capsule
Overall structure
Ureter drains into bladder
Names of regions from outside inwards: capsule, cortex, medulla, pelvis
Selective reabsorption
Proximal convoluted tubule
Cuboidal epithelial cells
Many microvilli to increase surface area for absorption
Many co-transporter proteins on the membrane
Tight junctions between epithelial cells so no fluid can leak between cells
Many mitochondria to provide energy for sodium-potassium pumps
Indirect/secondary active transport
Sodium pumped out, then moves back in and co-transports other molecule
Removal of solutes increases water potential, so water is reabsorbed via osmosis
Loop of Henle
Actively transports solutes to lower the water potential in the medulla and increase the water potential in the loop so more water can move in via osmosis
Some animals have evolved to have large medullas and long loops of Henle to maximise water reabsorption
Distal convoluted tubule
More sodium pumped out of tubule and potassium in to reduce water potential to increase water reabsorption via osmosis
Water uptake regulated by rate of ion pumps