Outer region of the kidney is called the cortex. The inner region is called the medulla. In the centre is the pelvis which leads into the ureter.
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What is the role of the kidney?
To remove waste products from the blood and to produce urine.
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What happens to the urine in the kidney?
It passes out of the kidney down the ureter to the bladder where it is stored before release.
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What is the nephron divided into?
The proximal convoluted tubule, the distal convoluted tubule, the loop of henle and the collecting duct.
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Describe nephrons and their pathway
Nephrons are tiny tubules. They start in the cortex where the capillaries form a knot called the glomerulus.
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What is the glomerulus surrounded by?
A cup-shaped structure known as the Bowman's capsule. Fluid from the blood is pushed into the Bowman's capsule by ultrafiltration.
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What happens to the fluid as it moves along the nephron?
Its composition changes. This is achieved by selective reabsorption.
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Where are substances reabsorbed and what is the final product?
Reabsorbed into the tissue fluid and blood capillaries. Urine is the final product in the collecting duct.
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What is reabsorbed and where?
All sugars, most salts and some water. 85% of reabsorption takes place in the proximal convoluted tubule.
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Changes in the descending limb of the loop of henle?
Water potential is decreased by the addition of salts and and the removal of water.
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Changes in the ascending limb of the loop of henle?
Water potential is increased as salts are removed by active transport.
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Changes to water potential in the collecting duct?
Decreases by removal of water to ensure urine has a low water potential.
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Describe the flow of blood in ultrafiltration
Blood flows into the glomerulus from the afferent arteriole. The afferent arteriole is wider than the efferent arteriole.
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Describe the pressure in the glomerulus and Bowman's capsule.
The pressure is higher in the glomerulus than the Bowman's capsule.
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Why is it important that the afferent arteriole is a different diameter to the efferent arteriole?
To ensure the blood in the capillaries of the glomerulus is under increased pressure.
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What does the glomerulus do to begin glomerular filtration?
Glomerulus brings a large SA of blood capillaries in close contact with the Bowman's capsule.
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What is filtered from the blood and what conditions are needed?
Liquid and small molecules are filtered from the blood under pressure.
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What is produced and what does it contain?
Glomerular filtrate is produced containing water, glucose, urea, salts, amino acids.
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What cannot pass into the tubule?
Proteins and blood cells as they are too big (over 69000).
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What are the 3 adaptions of the Bowman's capsule for ultrafiltration?
Endothelium of the capillary, basement membrane and the podocytes.
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How is the endothelium of the capillary adapted and why?
It is one cell thick and has narrow gaps. This provides a shorter diffusion distance and the gaps allow blood plasma and substances dissolved in it to pass through.
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Adaption of basement membrane and reasons for this
Made of a fine mesh of collagen fibres and glycoproteins. Acts as a filter to prevent the passage of molecules larger than 69000.
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How are the podocytes adapted and why?
They are specialised epithelial cells of the Bowman's capsule and have finger-like projections (major processes). These ensure there are gaps between cells so fluid from blood can pass into lumen of Bowman's capsule.
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What effect does the presence of proteins left in the capillary have?
Means the blood has very low water potential.
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Why is this good?
It ensures some fluid is retained in the blood and is important to help to reabsorb water later on.
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Other cards in this set
Card 2
Front
What is the role of the kidney?
Back
To remove waste products from the blood and to produce urine.
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