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Kidney in Detail. Standard Grade Biology. Excretion by the Kidney. Urea -nitrogenous waste -made by liver -excess amino acids in blood -toxic Why must nitrogenous waste be excreted?. 1 – Filtration by the Kidney. Supplied with blood from renal artery
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Kidney in Detail Standard Grade Biology
Excretion by the Kidney • Urea -nitrogenous waste -made by liver -excess amino acids in blood -toxic • Why must nitrogenous waste be excreted?
1 – Filtration by the Kidney • Supplied with blood from renal artery • Inside it splits into many fine capillaries • Each capillary supplies blood to hundreds of thousands of tiny filtration units called nephrons Renal artery Lets have a look at a nephron!!! Renal vein Ureter
Blood from renal artery enters wide capillary • Glomerulus brings a large surface area of blood capillaries in close contact with Bowman’s capsule 2. Liquid filtered from blood under pressure (filtration) • Glomerular filtrate produced containing: -water -glucose -salts -urea (Protein molecules and red blood cells do not pass into tubule as they are TOO BIG!!!!) Blood travels through narrow capillary towards renal vein Filtration Glomerular filtrate
Think… • Which feature of the glomerulus helps the process of filtration? • Which 4 components of unfiltered blood appear in the glomerular filtrate? • Why do blood cells and protein molecules not appear in the glomerular filtrate?
Key Words!! Nephron: structure in the kidney that acts as a microscopic filtration unit Glomerulus: dense mass of very fine blood capillaries at the nephron that act as a filter Bowman’s capusle: cup-shaped part of the nephron that holds a glomerulus and collects the products of filtration from it Glomerular filtrate: liquid removed from the blood by filtration in the kidney
2 – Reabsorption by the Kidney • Once the main components of glomerulur filtrate enter the bloodstream -they are no longer in bloodstream • If nothing more happened in the nephron then all the useful stuff would be lost in the urine! • Therefore, glucose, water and some salts need to be reabsorbed!
More water reabsorbed Glucose reabsorbed Final urine containing: -excess water -unneeded salts -waste urea Variable amounts of water and salts reabsorbed and filtrate gradually turning into urine
Think…. • Which three components of the glomerular filtrate are reabsorbed? • Why is it important for these to be reabsorbed? • Which substances are present in the final urine?
2 – Controlling Water Concentration • Blood -important part of internal environment -constantly changing water concentration -e.g. exercising drinking lots of water • The body uses negative feedback control to regulate water content of the blood
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