11.3
Describe the relationship between the glomerulus and Bowman's capsule.
(As the blood moves into the kidney via afferent arterioles it enters a knot-like capillary tuft called a glomerulus) This glomerulus is encapsulated by the Bowman's capsule, which is comprised of an inner surface of cells called podocytes (Podocytes have cellular extensions called pedicels that wrap around the blood vessels of the glomerulus Between the podocytes and the glomerulus is a glycoprotein matrix called the basement membrane that filters the blood) Blood is filtered by a mesh called the basement membrane, which lies between the glomerulus and Bowman's capsule (Glomerular blood vessels are fenestrated (have pores) which means blood can freely exit the glomerulus)
State the functions of the kidney.
(Kidneys function in both osmoregulation and excretion). The kidneys are responsible for removing substances from the blood that are not needed or are harmful.
List substances in the glomerular filtrate that are reabsorbed in the proximal convoluted tubule.
(almost all of the filtrate must be reabsorbed into the blood. Most of this reabsorption happens in the first part of the nephron - the proximal convoluted tube). Sodium ions, chloride ions, glucose and water.
Outline the role of interstitial fluid in osmoregulation.
(the energy to create the gradient is expended by wall cells in the ascending limb.) (in the ascending limb sodium ions are pumped out of the filtrate to the fluid between the cells in the medulla called the interstitial fluid.) the wall of the ascending limb is impermeable to water, so water is retained in the filtrate, even though the interstitial fluid is now hypertonic relative to the filtrate (it has a higher solute concentration) As filtrate flows down the descending limb, the increased solute concentration of interstitial fluid in the medulla causes water to be drawn out of the filtrate until it reaches the same solute concentration as the interstitial fluid.
Define osmoregulation.
A form of homeostasis whereby the concentration of the hemolymph, or blood in the case of animals with closed circulatory systems, is kept within a certain range.
Outline the process of kidney transplant.
A kidney from one person is placed in the body of a person whose kidneys aren't functioning. The donor can either be living or deceased. A living donor is possible because a person can survive with one functional kidney. (This approach can result in greater independence of movement and freedom to travel as compared to dialysis. Dialysis also carries with it the risk of infection and other complications. A drawback of transplant is that a recipeient's body can reject the organ.
Outline the use of a urine test strip in detection of diabetes, kidney damage and drug use.
A urine test strip is compared to the result chart on a testing kit bottle. The strip contains three test areas designed to change colour to indicate a positive or negative result after being dipped in urine. The colours displayed can then be compared to a results chart on the testing kit. The test indicates the pH, protein level and glucose level in the urine High levels of glucose and protein in a urine sample can be an indication of diabetes. High protein levels can indicate damage to the kidneys as these do not get through ultrafiltration in a healthy kidney. The panel drug test also uses test strips based on monoclonal antibody technology to look for the presence of traces of banned and controlled drugs in urine.
Outline the relationship between habitat and relative medullary thickness.
Animals adapted to dry habitats will often have long loops of Henle. Loops of Henle are found within the medulla. In order to accommodate long loops of Henle, the medulla must become relatively thicker.
Explain why plasma proteins and blood cells are not part of glomerular filtrate.
Because they are too large to pass through the capillary wall of the glomerulus. All particles with a relative molecule mass below 65,000 atomic mass units can pass through. The permeability to large molecules depends on their shape and charge. Almost all proteins are retained in the blood, along with all the blood cells.
Outline the cause and effect of high blood pressure in the kidney glomerulus.
Blood in capillaries is at high pressure in many of the tissues of the body, and the pressure forces some of the plasma out through the capillary wall, to form tissue fluid. In the glomerulus of the kidney, the pressure in the capillaries is particularly permeable, so the volume of fluid forced out is about 100 times greater than in other tissues.
Compare the relative glucose, oxygen and carbon dioxide concentrations between the renal artery and the renal vein.
Blood leaving the kidney through the renal vein is deoxygenated relative to the renal artery because kidney metabolism requires oxygen. · 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 not filtered by the kidney so should be present in the same concentration in the renal artery and renal vein.
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.
Bowman's capsule: a cup-shaped structure with a highly porous inner wall, which collects the fluid filtered from the blood. Proximal convoluted tubule: a highly twisted section of the nephron, with cells in the wall having many mitochondria and microvilli projecting into the lumen of the tube. Loop of Henle: a tube shaped like a hairpin, consisting of a descending limb that carries the filtrate deep into the medulla of the kidney, and an ascending limb that brings it back out to the cortex. Distal convoluted tubule: another highly twisted section, but with fewer, shorter microvilli and fewer mitochondria. Collecting duct: a wider tube that carries the filtrate back through the cortex and medulla to the renal pelvis. Blood vessels: associated with the nephron are blood vessels. Blood flows through them in the following sequence: Afferent arteriole: brings blood from the renal artery Glomerulus: a tight, knot-like, high pressure capillary bed that is the site of blood filtration Efferent arteriole: a narrow vessel that restricts blood flow, helping to generate high pressure in the glomerulus. Peritubular capillaries: a low-pressure capillary bed that runs around the convoluted tubules, absorbing fluid from them. Vasa recta: unbranced capillaries that are similar in shape to the loops of Henle, with a descending limb that carries blood deep into the medulla and an ascending limb bringing it back to the cortex. Venules: carry blood to the renal vein.
Compare urea and uric acid.
Converting ammonia to urea requires energy and converting it to uric acid is that it is not water-soluble and therefore does not require water to be released. Uric acid is linked to adaptions for reproduction. Nitrogenous wastes are released by the developing organism within eggs. Uric acid is released as it is not soluble and crystalizes rather than building up to toxic concentrations within the egg.
Outline the causes and consequences of dehydration
Dehydration is a condition that arises when more water leaves the body than comes in. it can arise from a number of factors including exercise, insufficient water intake or diarrhoea. It can lead to the disruption of metabolic processes. One sign of dehydration is darkened urine due to increased solute concentration. Water is necessary to remove metabolic wastes so dehydration can lead to tiredness and lethargy due to decreased efficiency of muscle function and increased tissue exposure to metabolic wastes. Blood pressure can fall due to low blood volume. This can lead to increases in heart rate. Body temperature regulation may be affected because of an inability to sweat.
· Outline the role of fenestration, the basement membrane and podocytes in ultrafiltration. (there are three parts to the ultrafiltration system.)
Fenestrations are found between the cells in the wall of the capillaries. These are about 100 nm in diameter. They allow fluid to escape, but not blood cells. The basement membrane that covers and supports the wall of the capillaries. It is made of negatively-charged glycoproteins, which form a mesh. It prevents plasma proteins from being filtered out, due to their size and negative charges. Podocytes forming the inner wall of the Bowman's capsule. These cells have extensions that wrap around the capillaries of the glomerulus and many short side branches called foot processes. Very narrow gaps between the foot processes help prevent small molecules from being filtered out of blood in the glomerulus. (if particles pass through all three parts they become part of the glomerulus filtrate.)
Define filtrate and ultrafiltration.
Filtrate: the fluid forced out (of the glomerulus) Ultrafiltration: the separation of particles differing in size by a few nanometres
Outline the process of hemodialysis.
Hemodialysis is required when the kidneys are no longer able to filter waste products from the blood properly. During the procedure, a steady flow of blood passes over an artificial semi-permeable membrane in the dialysis machine. The small waste products in the blood pass through the membrane, but the larger blood cells and proteins canot. The purified blood is then returned to the patient via a vein. This procedure takes several hours.
State the nitrogenous waste products released by: aquatic organisms, terrestrial organisms, marine mammals, amphibians, birds and insects.
If the organism lives in a marine or freshwater habitat, such as fish, echinoderms or coelenterates, they can release the waste directly as ammonia as it can be easily diluted within that environment. Terrestrial organisms will expend energy to convert ammonia to the less toxic forms of urea or uric acid depending on their habitats and evolutionary history. Marine mammals, despite their habitat, release urea because of their evolutionary history. Some organisms like amphibians release the waste as ammonia when they are larva and after metamorphosis, release the waste as urea. Converting ammonia to urea requires energy and converting it to uric acid requires even more energy. Birds and insects release their nitrogenous waste as uric acid. For birds, not having to carry water for excretion means less energy needs to be expended on flight.
Outline the source and function of ADH in osmoregulation.
If the solute concentration of the blood is too high, the hypothalamus of the brain detects this and causes the pituitary gland to secrete a hormone - antidiuretic hormone or ADH. This hormone causes the walls of the distal convoluted tubule and collecting duct to become much more permeable to water, and most of the water in the filtrate is reabsorbed
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.
If the solute concentration of the blood is too high, the hypothalamus of the brain detects this and causes the pituitary gland to secrete a hormone - antidiuretic hormone or ADH. This hormone causes the walls of the distal convoluted tubule and collecting duct to become much more permeable to water, and most of the water in the filtrate is reabsorbed. This is helped by the solute concentration gradient of the medulla. As the filtrate passes down the collecting duct, it flows deep into the medulla, where the solute concentration of the interstitial fluid is high. Water continues to be reabsorbed along the whole length of the collecting duct and the kidney produces a small volume of concentrated urine.
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.
If the solute concentration of the blood is too low, relatively little water is reabsorbed as the filtrate passes on through the distal convoluted tube and the collecting duct. The wall of these parts of the nephron can have an unusually low permeability to water. A large volume of urine is therefore produced, with a low solute concentration, and as a result the solute concentration of the blood is increased.
State the nitrogenous waste products found in insects and mammals.
In insects, the waste product is usually in the form of uric acid and in mammals it is in the form of urea.
Outline the structure and function of the Malpighian tubule system.
Insects have tubes that branch off from the intestinal tract. These are known as Malpighian tubules. Cells lining the tubules actively transport ions and uric acid from the hemolymph into the lumen of the tubules. This draws water by osmosis from the hemolymph through the walls of the tubules into the lumen. The tubules empty their contents into the gut. In the hindgut most of the water and salts are reabsorbed while the nitrogenous waste is excreted with the feces.
Describe the structure and function of the ascending limb of the loop of Henle
It is impermeable to water.
Define osmoregulation (my own dot point)
Keeping relative amounts of water and solutes in balance and at an appropriate level.
List two common causes of kidney failure.
Kidney failure most commonly occurs as a complication from diabetes or chronic high blood pressure (hypertension) as a result of diabetes.
State that many scientific discoveries have come from simple curiosity about particular phenomena.
Many scientific discoveries have come from simple curiosity about particular phenomena.
Outline the microscopic examination of urine for detection of infection, kidney stones or kidney tumors.
Microscopic examination of urine is carried out to determine if cells are present, as under normal circumstances, these cells should not be present. The presence of 6-10 neutrophils (white blood cells with a nucleus visible) can be a sign of urinary tract infection. The presence of red blood cells (erythrocytes) can be a sign that there is a kidney stone or a tumor in the urinary tract.
Outline the treatment of kidney stones by ultrasound.
One current treatment for kidney stones involves the use of ultrasounds (shock wave lithotripsy). Sound waves from outside the body are used to shatter the kidney stones into smaller fragments. Once disintegrated, the fragments of the kidney stone can be passed normally in the urine.
Define osmoregulator and osmoconformer.
Osmoregulator: maintain a constant internal solute concentration (even when living in marine environments with very different osmolarities) Osmoconformer: animals whose internal solute concentration tends to be the same as the concentration of solutes in the environment
List three example osmoregulator animals and three example osmoconformer animals.
Osmoregulators: all terrestial animals, freshwater animals and some marine organisms Osmoconformers: hagfish, skates and sharks
Outline the causes and consequences of overhydration.
Overhydration is less common than dehydration and occurs when there is an over-consumption of water. The result is a dilution of blood solutes. It might occur when large amounts of water are consumed after intense exercise without replacing the electrolytes lost at the same time. This makes body fluids hypotonic and could result in the swelling of cells due to osmosis. If this occurs, the most notable symptoms are headache and nerve function disruption.
List solutes found in glomerular filtrate.
Sodium ions, chloride ions, glucose, urea, proteins
Outline the mechanism of selective reabsorption of sodium ions, chloride ions, glucose and water.
Sodium ions: are moved by active transport from filtrate to space outside the tubule. They then pass to the peritubular capillaries. Pump proteins are located in outer membrane of tubule cells. Chloride ions: are attracted from filtrate space outside the tubule because of charge gradient set up by active transport of sodium ions. Glucose: is co-transported out of filtrate and into fluid outside the tubule, by co-transporter proteins in outer membrane of tubule cells. Sodium ions move down concentration gradient from outside tubule into tubule cells. This provides energy for glucose to move at the same time to fluid outside the tubule. The same process is used to reabsorb amino acids. Water: pumping solutes out of filtrate and into the fluid outside the tubule creates a solute concentration gradient, causing water to be reabsorbed from filtrate by osmosis
Define nephron.
The basic functional unit of the kidney. It is a tube with a wall consisting of one layer of cells.
Describe the structure and function of the descending limb of the loop of Henle.
The cells in the wall of the descending limb are permeable to water but are impermeable to sodium ions. (As filtrate flows down the descending limb, the increased solute concentration of interstitial fluid in the medulla causes water to be drawn out of the filtrate until it reaches the same solute concentration as the interstitial fluid.)
Outline the relationship between habitat and length of the loop of Henle.
The length of the loop of Henle is positively correlated with the need for water conservation in animals. The longer the loop of Henle, the more water volume will be reclaimed. Animals adapted to dry habitats will often have long loops of Henle.
Describe why the loop of Henle is a countercurrent multiplier system.
The system for raising solute concentration is an example of a countercurrent multiplier system. It is a countercurrent sytstem because of the flows of fluid in the opposite directions. It is a countercurrent multiplier because it causes a steeper gradient of solute concentration to develop in the medulla than would be possible with a concurrent system. There is also a countercurrent system in the vasa recta. (This prevents the blood flowing through this vessel from diluting the solute concentration of the medulla, while still allowing the vasa recta to carry away the water removed from the filtrate in the descending limb, together with sodium ions. )
Explain why cells lining the lumen of the proximal convoluted tubule have microvilli and many mitochondria.
They have many microvilli to increase surface area for absorption. Many mitochondria provide the energy needed for active transport.
State the overall function of the loop of Henle.
To create a gradient of solute concentration (hypertonic) in the medulla.
List 4 substances that are found in higher concentration in the renal artery than in the renal vein.
Toxins and other substances that are ingested and absorbed but are not fully metabolized by the body, for example betain pigments in beets and also drugs. Excretory waste products including nitrogenous waste products, mainly urea. (other things removed from the blood by the kidney that are not excretory products include:) Excess water, produced by cell respiration or absorbed from food in the gut Excess salt, absorbed from food in the gut
Define urinalysis.
Urinalysis is a clinical procedure that examines urine for any deviation from normal composition.
Outline the production and effect of ammonia in animals.
When animals break down amino acids and nucleic acids, nitrogenous waste in the form of ammonia is produced, ammonia is highly basic and can alter the pH balance. It is also toxic as it is a highly reactive chemical.
Outline the tonicity of filtrate entering the distal convoluted tubule from the loop of Henle.
When filtrate enters the distal convoluted tubule from the loop of Henle, its solute concentration is lower than that of normal body fluids - it is hypotonic. This is because proportionately more solutes than water have passed out of the filtrate as it flows through the loop of Henle in the medulla.