The Kidney and Osmoregulation

The Kidney & Osmoregulation Kidneys Define excretion Excretion is the removal from the body of the waste products of metabolic activity ………………………………………………………………………………………………………………………………………………….......... ………………………………………………………………………………………………………………………………………………….......... Identify the nitrogenous waste produced by the following animals: Ammonia (which is very toxic but very water soluble) Fish: ……………………………………………………………………………………………………………………………………………….. Uric acid (which requires minimal water to flush) Birds: ……………………………………………………………………………………………………………………………………………... Urea (which is non-toxic and so can be stored at higher concentrations) Mammals: ………………………………………………………………………………………………………………………………………. Distinguish between the excretory systems of insects and mammals Mammals possess autonomous kidneys ………………………………………………………………………………………………………………………………………………….......... Insects possess Malpighian tubules that are connected to the insect’s digestive system ………………………………………………………………………………………………………………………………………………….......... ………………………………………………………………………………………………………………………………………………….......... Label the diagram of a human kidney Medulla 1. ………………………………………………………………………... Renal pelvis 2. ………………………………………………………………………... Cortex 3. ………………………………………………………………………... Renal artery 4. ………………………………………………………………………... Renal vein 5. ………………………………………………………………………... Ureter 6. ………………………………………………………………………... State the functional unit of a kidney Nephron ………………………………………………………………………………………………………………………………………………….......... Annotate a diagram of a nephron Proximal convoluted tubule 1. ……………………………………………………………………….................. Bowman’s capsule 2. ……………………………………………………………………….................. Glomerulus 3. ……………………………………………………………………….................. Loop of Henle 4. ……………………………………………………………………….................. Distal convoluted tubule 5. ……………………………………………………………………….................. Vasa recta 6. ……………………………………………………………………….................. Collecting duct 7. ……………………………………………………………………….................. Osmoregulation Distinguish between osmoconformers and osmoregulators Osmoconformers match their internal osmolarity to that of the environment ………………………………………………………………………………………………………………………………………………….......... Osmoregulators maintain a constant osmolarity (independent of environment) ………………………………………………………………………………………………………………………………………………….......... Identify the three stages of urine formation and where each stage occurs Stage Location 1 Ultrafiltration Glomerulus / Bowman’s capsule 2 Selective reabsorption Convoluted tubules (mainly proximal but some distal) 3 Osmoregulation Loop of Henle / collecting duct Explain the process of ultrafiltration Ultrafiltration is the non-specific filtration of blood under high pressure (separates blood cells and proteins) ………………………………………………………………………………………………………………………………………………….......... Glomerular capillaries are fenestrated and the capsule is lined with podocytes that have extensions (pedicels) ………………………………………………………………………………………………………………………………………………….......... Blood freely enters the capsule by passing between the extensions, so the only barrier is a basement membrane ………………………………………………………………………………………………………………………………………………….......... Blood enters the glomerulus via a wide afferent arteriole and exits via a narrow efferent arteriole ………………………………………………………………………………………………………………………………………………….......... This makes it difficult for blood to exit the glomerulus, increasing the hydrostatic pressure in the glomerulus ………………………………………………………………………………………………………………………………………………….......... Describe the selective reabsorption of glucose, salts and amino acids by the nephron Selective reabsorption involves the reuptake of usable substances from filtrate ………………………………………………………………………………………………………………………………………………….......... Substances are actively transported across apical membrane, before diffusing across basolateral membrane ………………………………………………………………………………………………………………………………………………….......... Tubules are lined by microvilli (⬆ surface area) and reabsorb the following materials: ………………………………………………………………………………………………………………………………………………….......... Glucose & amino acids (symport with Na+), ions & vitamins (via protein pumps), water (follows via osmosis) ………………………………………………………………………………………………………………………………………………….......... ………………………………………………………………………………………………………………………………………………….......... Explain, using the diagram, how the loop of Henle maintains hypertonic conditions in the medulla The loop of Henle creates a salt gradient within the medulla ………………………………………………………………………………………………… • The descending limb is permeable to water but not to salt ………………………………………………………………………………………………… • The ascending limb is permeable to salts but not to water ………………………………………………………………………………………………… This means that as the loop descends into the medulla, the ………………………………………………………………………………………………… interstitial fluid becomes salty (hypertonic) ………………………………………………………………………………………………… Additionally, blood in the vasa recta runs countercurrent to the ………………………………………………………………………………………………… filtrate, so salts in blood move towards the medulla (and water away) ………………………………………………………………………………………………… As the collecting duct passes through the medulla, the salt gradient ………………………………………………………………………………………………… will draw water from the ducts (osmoregulation) ………………………………………………………………………………………………… ………………………………………………………………………………………………… Explain the role of ADH (vasopressin) in maintaining the water balance of the blood The level of water drawn from collecting ducts is controlled by the hormone antidiuretic hormone (ADH) ………………………………………………………………………………………………………………………………………………….......... ADH is released from the pituitary gland (posterior lobe) in response to dehydration ………………………………………………………………………………………………………………………………………………….......... ADH produces water channels (aquaporins) to facilitate water reabsorption via osmosis ………………………………………………………………………………………………………………………………………………….......... This means less water remains in the filtrate and the urine becomes more concentrated ………………………………………………………………………………………………………………………………………………….......... When an individual is suitably rehydrated, ADH levels decrease and less water is reabsorbed ………………………………………………………………………………………………………………………………………………….......... Outline an adaptation to the kidneys of desert mammals that increases water conservation Animals living in arid / dry habitats have long loops of Henle (⬆ water reabsorption) ………………………………………………………………………………………………………………………………………………….......... ………………………………………………………………………………………………………………………………………………….......... Explain the difference in the concentration of molecules within the blood plasma, filtrate and urine Component Blood Protein Present Absent Absent Glucose Present Present Absent Selectively reabsorbed in tubules Urea Present Present Present Eliminated (nitrogen waste product) Water Present Filtrate Present Urine Present Reason Remains in blood due to ultrafiltration Variable excretion to regulate water levels in body (osmoregulation) Identify four substances that can be detected via urinary tests, and the significance of a positive sample Glucose: Presence in urine indicates diabetes 1. …………………………………………………………………………………………………………………………………………………... Protein: Certain diseases / hormonal condition 2. …………………………………………………………………………………………………………………………………………………... Blood cells: Infectious diseases or cancers 3. …………………………………………………………………………………………………………………………………………………... Drugs: For example, performance enhancers 4. …………………………………………………………………………………………………………………………………………………... Outline the consequences of dehydration and overhydration Dehydration Dehydration causes blood pressure to drop and heart rate rises to compensate ………………………………………………………………………………………………………………………………………………….......... ………………………………………………………………………………………………………………………………………………….......... Overhydration Overhydration can potentially lead to tissue damage (cells lyse from osmosis) ………………………………………………………………………………………………………………………………………………….......... ………………………………………………………………………………………………………………………………………………….......... Outline two methods for the treatment of kidney failure Kidney dialysis involves the external filtering of blood in order to remove metabolic wastes ………………………………………………………………………………………………………………………………………………….......... Blood is pumped through a dialyzer, which restricts passage of certain materials and introduces fresh fluid ………………………………………………………………………………………………………………………………………………….......... The best long-term treatment for kidney failure is a kidney transplant: ………………………………………………………………………………………………………………………………………………….......... A transplanted kidney is grafted into the abdomen, but donors must be a close genetic match to minimise rejection …………………………………………………………………………………………………………………………………………………..........