The Nephron HSC Biology: Maintaining a Balance Syllabus link: explain how the processes of filtration and reabsorption in the mammalian nephron regulate body fluid composition BEGIN

Instructions and notes The nephron is one of the more difficult concepts to understand in the Maintaining a Balance module of the HSC Biology course. This resource is designed to build upon your knowledge of the kidney, test your understanding of the nephron and be used as a study tool for your exams. Work through the questions slowly and don’t cheat – it’s not going to help you understand the concept! NEXT

Nephrons There are about _______________ in each mammalian kidney

Formation of urine The nephron is a small filtering unit in which urine is produced. The three processes in the formation of urine are: filtration, reabsorption and secretion. The kidneys process a large amount of blood, but produce a relatively small amount of urine. NEXT

Excellent! There are about one million nephrons in each kidney. BOM CHICKA WOW WOW Excellent! There are about one million nephrons in each kidney. NEXT

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Label the nephron A H G D B E C F Label A, B & C Label D, E & F Label G & H

Label the nephron The parts of the nephron labelled A, B and C, respectively, are: Bowman’s capsule, distal convoluted tubule, collecting duct Bowman’s capsule, proximal convoluted tubule, collecting duct Glomerulus, loop of Henle, collecting duct Glomerulus, loop of Henle, urethra Return to diagram

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Label the nephron The parts labelled D, E and F, respectively, are: Bowman’s capsule, loop of Henle, distal convoluted tubule Bowman’s capsule, proximal convoluted tubule, loop of Henle Glomerulus, loop of Henle, collecting duct Glomerulus, proximal convoluted tubule, loop of Henle Return to diagram

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Label the nephron The parts labelled G and H, respectively, are: Afferent arteriole, efferent arteriole Affluent arteriole, efferent arteriole Efferent arteriole, afferent arteriole Efferent duct, afferent duct Return to diagram

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Finito! (except not)

Filtration, Reabsorption and Secretion Filtration is the removal of wastes from blood and other fluids through a semi permeable membrane. Reabsorption is an active process that requires energy. It is the movement of materials being reabsorbed into the blood. Secretion is: The body actively transporting substances from the nephron into the blood The body actively transporting substances from the blood into the nephron

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Blood Blood comes to the kidneys via the: Renal vein Renal artery The ____________ arteriole brings blood to the glomerulus. Efferent Afferent

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The Glomerulus The glomerulus is a ball of capillaries in which blood pressure is so high that some of the liquid from the blood is forced through the walls of the blood vessels into the Bowman’s capsule. This liquid does not have: Blood cells Sodium chloride (NaCl) Large proteins Blood cells AND large proteins

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Great work! The filtrate should not contain large proteins or blood cells but does contain: - Blood plasma Water Solutes: NaCl, K+, HCO3- Glucose and amino acids Other ingested substances like penicillin and aspirin Hormones Nitrogenous waste products such as urea NEXT

Proximal tubule Reabsorption is an active process that requires energy. Click on the different substances to see if they are secreted into the nephron or reabsorbed into the blood. Amino acids Glucose Water K+ NaCl Drugs e.g. aspirin Bicarbonate ions Hydrogen ions NEXT

Amino acids are actively transported into transported from the proximal tubule into the blood. This is reabsorption. BACK

Glucose is actively transported into transported from the proximal tubule into the blood. This is reabsorption. BACK

As salt moves out of the tubule, water passes by osmosis back into the blood. This is reabsorption.

Sodium ions are actively transported back into the blood and chloride ions follow passively. This is absorption. BACK

Most of the bicarbonate ions are actively reabsorbed in the proximal tubule. Some hydrogen ions may be secreted in order to keep the constant pH of blood and body fluids. BACK

Drugs such as aspirin and penicillin and poisons identified by the liver are actively secreted into the tubule. BACK

Some hydrogen ions are secreted into the proximal tubule Some hydrogen ions are secreted into the proximal tubule. This is done to maintain the constant pH of blood and body fluids BACK

Potassium ions are actively transported into the blood Potassium ions are actively transported into the blood. This is absorption. BACK

Reabsorption checkpoint Surrounding each tubule is a large capillary network. As the filtrate travels through the tubules and the loop of Henle, the substances that the body can re-use are reabsorbed into the blood. These substances include glucose, amino acids, vitamins, minerals, bicarbonate and water. NEXT

Loop of Henle The loop of Henle has a descending and an ascending limb. The walls of the loop of Henle are permeable to water but not to salt. Water passes across the membrane by: Diffusion osmosis Diffusion Osmosis

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Loop of Henle In the ascending portion of the loop of Henle, the walls are permeable to salt not water. Salt passes out passively across a thin-walled section and then ____________ across a thick-walled section. _____________ is: actively passively

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Loop of Henle What part of the kidney does the loop of Henle mostly sit? cortex medulla pyramid pelvis Cortex Medulla Pelvis Pyramid Source: http://www.comprehensive-kidney-facts.com/kidney-anatomy.html

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Loop of Henle As water is removed from the loop of Henle in the descending limb, the concentration of salt in the medulla: As salt is removed from the loop of Henle in the ascending limb, the concentration of salt: Decreases Increases Decreases as it moves towards up to the cortex Increases as it moves up towards the cortex

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Source: http://www.colorado.edu/intphys/iphy3410saul/resources/kidney.html As you can see in the diagram above, the concentration of salt is high in the bottom of the loop of Henle in the medullary region of the kidney. This is called an osmolarity gradient, where the solute concentration (sodium and urea in this case) increases from the cortex down to the inner medulla. NEXT

Distal tubule In the distal tubule, the pH of the blood and the level of salts, in particular sodium and potassium, are adjusted by selective absorption and secretion. In the distal tube, small amounts of NaCl and H2O are reabsorbed and K+ and H+ ions are secreted. NEXT

Collecting Duct The collecting duct transports urine to the pelvis of the kidney which leads to the ureter. The walls of the collecting duct are are permeable to water, but not salt which results in water passing out of the duct by osmosis. Urea and salt is also actively reabsorbed in the duct. This results in the formation of of urine. NEXT

FIN! Questions to ask yourself: What do I know? Where are the gaps in my knowledge? What do I need to study in order to understand this concept? This is a resource for you! So feel free to change it up, add things in and build upon your knowledge. This could be a very useful study tool for you!