Kidney Structure and Function Study Guide

11.3.U1: Animals are either osmoregulators or osmoconformers (Oxford Biology Course Companion page 485).

1. Define osmoregulator and osmoconformer.Osmoregulators keep their body's osmolarity conditions regardless of the environment or conditions of their surroundings. This requires more energy to ensure that conditions are tightly controlled. Osmoconformers maintain internal conditions equal to the osmolarity of their environment. (conforms environment) This requires less energy but the organism is affected by environmental change.

2. List three example osmoregulator animals and three example osmoconformer animals.Osmoconformer animals: marine animals - echinoderms such as lobsters, jellyfish, mussels, squids, sea squirts,Osmoregulator animals: human, some marine fishes like sharks, freshwater and marine fishes such as salmon

11.3.U2: The Malphigian tubule system in insects and the kidney carry out osmoregulation and removal of nitrogenous wastes (Oxford Biology Course Companion page 486).

3. Define osmoregulation.Osmoregulation is the control of the water balance of the blood, tissue, or cytoplasm of a living organism.

4. State the nitrogenous waste products found in insects and mammals.Insects (and birds): uric acid; Mammals (and marine fish, adults amphibians): urea

5. Outline the structure and function of the Malpighian tubule system.The system consists of branching tubules extending from the alimentary canal that absorbs solutes, water, and wastes from the surrounding hemolymph. Circulatory system of insects uses hemolymph rather than blood. Wastes such as ammonia are thought to diffuse through the walls, while ions such as sodium and potassium are transported by active pump mechanisms. Water follows thereafter. Feces and uric acid leave through the rectum. There sodium and potassium ions are actively pumped actively back to the hemolymph and again water follows via osmosis. Uric acid is left to mix with feces, which are then excreted. By circulating ions and water between hemolymph and hindgut, rectum, malpighian tubule system prevents dehydration and achieves osmoregulation.

11.3.U9: The type of nitrogenous waste in animals is correlates with evolutionary history and habitat (Oxford Biology Course Companion page 495).

6. Outline the production and effect of ammonia in animals.Nitrogenous wastes are produced from the break-down of nitrogen-containing compounds such as amino acids and nucleotides. Ammonia is highly toxic but also very water soluble which can be effectively flushed out by animals in aquatic habitats.

7. State the nitrogenous waste products released by: aquatic organisms, terrestrial organisms, marine mammals, amphibians, birds and insects.Aquatic organisms: NH3Amphibians, birds, insects: Uric acid Terrestrial organisms, marine mammals: Urea

8. Compare urea and uric acid.Urea is colorless, soluble in water, odorless, and neutral. It is not toxic and is widely used in the manufacture of the fertilizers. The uric acid has a crystalline form, forming ions and salts. In general, the water solubility of uric acid is low. Both are products of the metabolic breakdown of purine nucleotides. Nitrogenous wastes in the body tend to form toxic ammonia, which must be excreted.Mammals such as humans excrete urea, while birds, reptiles, and some terrestrial invertebrates produce uric acid as waste.Conversion of ammonia into uric acid is more energy intensive than the conversion of ammonia into urea

Producing uric acid instead of urea is advantageous because it is less toxic and reduces water loss and the subsequent need for water

11.3.S1: Drawing and labelling a diagram of the human kidney (Oxford Biology Course Companion page 487).

9. Draw a diagram of a human kidney.10. Label the renal artery, renal vein, cortex, medulla, renal pelvis and ureter on a diagram of the human kidney.

11.3.S2: Annotations of a diagram of the nephron (Oxford Biology Course Companion page 492).

11. Define nephron.A nephron is a functional unit of the kidney. The structure is a tube with a wall consisting of one layer of cells. There are different parts of the nephrons and each have a different function and structure.

12. Annotate a diagram of the nephron with the following structures and associated functions: Bowman’s capsule, proximal convoluted tubule, Loop of Henle,. distal convoluted tubule, collecting duct, afferent arteriole, glomerulus, efferent arteriole, peritubular capillaries, vasa recta and venules.

Afferent arteriole: Brings blood to the nephron to be filtered

Efferent arteriole: Removes blood from nephron (minus filtered components)

Glomerulus: Capillary tuft where filtration occurs

Bowman's Capsule: First part of nephron where filtrate is collected

Proximal Convoluted Tubule: Where selective reabsorption occurs Loop of Henle: Important for establishing a salt gradient in the medulla Distal Convoluted Tubule: Final site of selective reabsorption Collecting Duct: Feeds into ureter and is where osmoregulation occurs Vasa Recta: Blood network that reabsorbs components from the filtrate

11.3.U3: The composition of blood in the renal artery is different from that in the renal vein (Oxford Biology Course Companion page 487).

13. State the functions of the kidney.The function of the kidney would be osmoregulation and excretion.

14. Distinguish between osmoregulation and excretion. Osmoregulation is the control of the water concentration in the body while excretion is the release of metabolic waste.

15. List 4 substances that are found in higher concentration in the renal artery than in the renal vein.Water, oxygen, glucose, toxins and urea are in higher concentration in the renal artery than in the renal vein.

16. Compare the relative glucose, oxygen and carbon dioxide concentrations between the renal artery and the renal vein.Blood in the renal vein (i.e. after the kidney) will have:Less urea (large amounts of urea is removed via the nephrons to form urine)

Less water and solutes / ions (amount removed will depend on the hydration status of the individual) Less glucose and oxygen (not eliminated, but used by the kidney to generate energy and fuel metabolic

reactions) More carbon dioxide (produced by the kidneys as a by-product of metabolic reactions)

17. State that plasma proteins are not filtered by the kidney so should be present in the same concentration in the renal artery and renal vein. Plasma proteins are found in both the renal artery and the renal vein. Since plasma proteins are not filtered the concentration must be equal and balanced.

11.3.U4: The utrastructure of the glomerulus and Bowman’s capsule facilitate ultrafiltration (Oxford Biology Course Companion page 489).

18. Outline the cause and effect of high blood pressure in the kidney glomerulus.High blood pressure is caused by the proximity to the heart's contractions or the arteriole that leaves the glomerulus is narrower than the one that enters. The effect of high blood pressure is then that high blood pressure pushes molecules through the capillary walls, passing the basement membrane, and into the Bowman's capsule.

19. List solutes found in glomerular filtrate.Solutes found in glomerular tubule would be water, glucose, amino acids, NaCl, urea, since they can be filtered.

20. Define filtrate and ultrafiltration.Filtrate: The fluid in the lumen of the Bowman's capsule of the nephron that has been filtered from the capillaries of the glomerulus (see ultrafiltration). The glomerular filtrate has the same composition as the plasma except that it does not contain any of the larger components, such as plasma proteins or cells.Ultrafiltration: A high pressure filtration through a semipermeable membrane where particles are kept while the small sized solutes and the solvent are forced to move across the membrane by hydrostatic pressure forces.

21. Explain why plasma proteins and blood cells are not part of glomerular filtrate.

Plasma proteins and blood cells cannot pass through the basement membrane. This means that they cannot be part of the glomerular filtrate.

22. On a glomerulus diagram, label the basement membrane, fenestrations, podocyte foot processes, podocytes.

23. Outline the role of fenestration, the basement membrane and podocytes in ultrafiltration.Fenestrations: these are like holes between the cells found in the walls of the capillaries. The fenestrations are about 100 nm in diameter. The fenestrations allow fluid to escape, but not blood cells.

Basement membrane: this covers and supports the walls of the capillaries. The basement membrane is composed of negatively-charged glycoproteins and they form a mesh. The basement membrane prevents plasma proteins from being filtered out because of their size and negative charges

Podocytes: podocytes form the inner wall of the Bowman's capsule. Podocytes have extensions that wrap around the capillaries of the glomerulus and many short side branches called foot processes. The narrow gaps between the foot processes help prevent small molecules from being filtered out of blood in the glomerulus.

24. Describe the relationship between the glomerulus and Bowman’s capsule.The glomerulus and Bowman's capsule help in the process of creating urine. They both work together to do so. The glomerulus brings the blood to filter out the small molecules into the Bowman's capsule. Blood and plasma proteins aren't part of the glomerular filtrate. The small molecules pass through the fenestrations and through the basement membrane found around the capillaries. The small molecules also pass through podocytes which line the Bowman's capsule and extend to wrap around the glomerulus capillaries. The small molecules are then within the lumen of the Bowman's capsule to get filtrated further into the proximal convoluted tubule.

11.3.U5: The proximal convoluted tubule selectively reabsorbs useful substances by active transport (Oxford Biology Course Companion page 491).

25. List substances in the glomerular filtrate that are reabsorbed in the proximal convoluted tubule.Substances in the glomerular filtrate that are reabsorbed in the proximal convoluted tubule would be: Na+ (sodium), Cl-(chlorine), Glucose, H2O

26. Explain why cells lining the lumen of the proximal convoluted tubule have microvilli and many mitochondria.Cells lining the lumen of the proximal convoluted tubule have microvilli to increase surface area which increases efficiency. More surface area means more substances will be reabsorbed. Many mitochondria is needed to run the pumps for active transport.

27. Outline the mechanism of selective reabsorption of sodium ions, chloride ions, glucose and water.Selective reabsorption of sodium ions, chloride ions, and glucose are done through active transport where only ions can pass through. For water, passive transport is used so that H2O can pass through and be reabsorbed.

11.3.U6: The loop Henle maintains hypertonic conditions in the medulla (Oxford Biology Course Companion page 492).

28. State the overall function of the loop of Henle.The loop of Henle controls the hypertonic conditions in the medulla and controls the water concentration in the body.

29. Outline the role of interstitial fluid in osmoregulation.the hypertonic conditions of the medulla will draw water out by osmosis

30. Describe the structure and function of the descending limb of the loop of Henle.The descending limp of the loop of Henle have cells that are permeable to water. When filtrate flows down the descending limp, the increased solute concentration of interstitial fluid in the medulla causes water to go out until it has the same concentration as the interstitial fluid.

31. Describe the structure and function of the ascending limb of the loop of Henle.The ascending limp of the loop of Henle, on the other hand, have cells that are impermeable to water but permeable to sodium ions. This allows that water remain in the filtrate despite the interstitial fluid being hypertonic relative to the filtrate.

32. Describe why the loop of Henle is a countercurrent multiplier system.The loop of Henle is a countercurrent multiplier system since the fluid flows in opposite directions. The multiplier is explained by the fact that the loop of Henle allows for a steeper gradient of solute concentration to be in the medulla than would be allowed in the concurrent system.

11.3.U8: ADH controls reabsorption of water in the collecting duct (Oxford Biology Course Companion page 494).

33. Outline the tonicity of filtrate entering the distal convoluted tubule from the loop of Henle.Hypotonic – more solutes than water have passed out through the loop of Henle

34. Outline the of low blood solute concentration on the volume of urine produced, solute concentration in the urine, permeability of the distal convoluted tubule and collecting duct to water and volume of water reabsorbed.(low blood osmolarity) with low blood osmolarity indicates that the ADH released will be little as there is no dehydration. This means that the urine produce will be diluted. Low blood solute concentration indicates that there is more water, so, water must be released. The collecting duct is not permeable to water. So low blood solute concentration, where ADH is less present, a large volume of diluted urine is released. When the body finally gets rid of the water, blood osmolarity for homeostasis is reached. Distal convoluted tubule also becomes impermeable to water.

35. Outline the of high blood solute concentration on the volume of urine produced, solute concentration in the urine, permeability of the distal convoluted tubule and collecting duct to water and volume of water reabsorbed.(high blood osmolarity)with high blood solute concentration, this indicates that there is less water relative to the solutes present. Or in other word, dehydrated. Osmoreceptors detect this and ADH is released. ADH triggers thirst. This means also that as more ADH is present, the collecting duct is highly permeable to water This results that more water can return to the body and so, only a small volume of concentrated urine is produced. When body is absorbing water this will result in reaching blood osmolarity for homeostasis. Becomes permeable to water.

36. Outline the source and function of ADH in osmoregulation.ADH is a hormone released when osmoreceptors found in the hypothalamus in most homeothermic organisms. These osmoreceptors detect change in osmotic pressure. ADH triggers thirst when blood osmolarity is high. When ADH is not present the distal convoluted tubule and collecting duct become impermeable to water and vice versa happens when ADH is present. With an increase in blood osmolarity, ADH released triggers thirst and so drinking water can help attain blood osmolarity for homeostasis. When less ADH is released, water is then released through dilute urine which indicates that blood osmolarity for homeostasis can be reached.

11.3.A1: Consequences of dehydration and overhydration (Oxford Biology Course Companion page 496).

37. Outline the causes and consequences of dehydration.Dehydration: loss of body fluids, mostly water, exceeds the amount taken in causes: more water is moving out of our cells and bodies than what we take in through drinking. (fever, heat exposure, too much exercise, vomiting, diarrhea, and extreme burns)

consequences: increased thirst, dry mouth, weakness, dizziness, decreased urine, confusion, inability to sweat

38. Outline the causes and consequences of overhydration.causes:-drink more water than it loses (excessive water) and not enough of sodium -but drinking large amounts of water usually doesn't cause overhydration if the pituitary gland, kidneys, liver, and heart are functioning normally. consequences:-when overhydration occurs slowly then brain cells can adapt and only mild symptoms occur: distractibility and lethargy-when overhydration occurs quickly the consequences are confusion, seizures, or coma

11.3.NOS: Curiosity about particular phenomena- investigations were carried out to determine how desert animals prevent water loss in their wastes. (Oxford Biology Course Companion page XXX).

39. State that many scientific discoveries have come from simple curiosity about particular phenomena.

11.3.U7: The length of the loop of Henle is positively correlated with the need for water conservation in animals (Oxford Biology Course Companion page 493).

40. Outline the relationship between habitat and length of the loop of Henle.- for animals that are adapted to dry habitats the loop of henle will be longer- a longer loop of Henle means that the salt gradient will increase which means water will be reabsorbed and urine is concentrated. The medulla will become thicker. - for animals that are adapted to moist environments the loop of Henle will be shorter - a shorter loop of henle means that the salt gradient will decrease which means less water will be reabsorbed and urine will be diluted. The medulla will be thinner.

41. Outline the relationship between habitat and relative medullary thickness.

11.3.A2: Treatment of kidney failure by hemodialysis or kidney transplant (Oxford Biology Course Companion page 496).

42. List two common causes of kidney failure.Diabetes and high blood pressure

43. Outline the process of hemodialysis. In hemodialysis, a machine filters wastes, salts, and fluid from the blood when the kidneys are no longer capable enough to do the work.

44. Outline the process of kidney transplant.

With a kidney transplant, a procedure is done through surgery to place a kidney from a live or deceased donor into a person whose kidneys don't function properly. An advantage would be that the donor can live without two kidneys but one. A disadvantage would be sometimes the body rejects the organ.

45. Outline the treatment of kidney stones by ultrasound. Ultrasonic waves would be targetted towards the kidney stones to fragment it. The kidney stones fragment to tiny pieces which can be released from the body.

11.3.A3: Blood cells, glucose, proteins and drugs are detected in urinary tests (Oxford Biology Course Companion page 497).

46. Define urinalysis.Urinalysis is an indicator of disease but not for kidney disease.

47. Outline the use of a urine test strip in detection of diabetes, kidney damage and drug use.Diabetes:using a urine strip, if there's a high pressure of glucose in the urine, this indicates diabetes. For kidney damage:Prescence of amount of protein, blood, pus, bacteria, and sugar may change and indicate kidney damage. Drug use:Drugs (most) pass through the body and can be detected including performance enhancing drugs.

48. Outline the microscopic examination of urine for detection of infection, kidney stones or kidney tumors.Urine is examined to determine if there are cells present which normally should not be.

Neutrophils – UTI Erythrocytes – kidney stone or tumor