The Kidney and Osmoregulation: Topic 11.3 Flashcards
Label a diagram of the nephron
do it or you’re a bitch
function of each structure of a nephron
bowman's capsule: ultrafiltration proximal tubule: selective reabsorption loop of Henle: osmoregulation distal tubule: selective reabsorption collecting duct: osmoregulation (water retention)
Describe how the structure of the glomerulus and Bowman’s capsule are adapted to their function (of ultrafiltration).
Glomerulus: wide afferent arteriole and narrow efferent arteriole to create high pressure in the glomerulus, highly branched inside of Bowman’s capsule to increase surface area, vessels in the glomerulus contain fenestrations to allow blood contents to ball through vessel membranes and into Bowman’s capsule, basement membrane between glomerulus and bowman’s capsule to prevent large substances from entering into the filtrate, Bowman’s capsule has a single layer of fenestrated cells to decrease filtration distance and allow substances to pass freely into the capsule
Explain the process of ultrafiltration (including which substances become part of the filtrate and which do not become part of the filtrate and why).
Blood from the renal artery enters the capsule through the afferent arteriole which is larger than the efferent creating high pressures, high pressure forces water and blood contents through fenestrations in the glomerulus, filtered contents of the blood then pass through the basement membrane which blocks larger objects from passing through, filtered contents of the blood then pass through fenestrations in the podocytes that line Bowman’s capsule forming a fluid called filtrate which then passes into the proximal convoluted tubule, blood cells, proteins, platelets that don’t go in the filtrate exit through the efferent arteriole
Describe how the structure of the proximal convoluted tubule is adapted to its function.
Epithelial cells that line the PCT contain microvilli which project into the lumen to increase surface area for reabsorption, epithelial wall is only one cell thick to minimize diffusion distance and contain mitochondria for active transport, network of capillaries surrounds the PCT for reabsorption
Describe the transport mechanisms used by the proximal convoluted tubule to selectively reabsorb salt ions and vitamins, amino acids and glucose, and water.
reabsorb salt ions and vitamins, amino acids and glucose, and water.
Salt Ions + Vitamins: actively transported into epithelial cells then passively transported from epithelial cells into the bloodstream
Amino Acids + Glucose: Co transported with Na ions into epithelial cells then actively transported into epithelial cells after 50% reabsorbed until 100%
Water: Reabsorbed passively through osmosis
Describe the role of the loop of Henle and the collecting duct in osmoregulation.
Osmoregulation is the control of water and solute balance in an organism, the amount of water eliminated in the urine each day depends on many things like the amount of water ingested, perspiration rate, and ventilation rate. The loop of Henle consists of two parts; a descending part and an ascending part. Filtrate passes through the PCT into the descending loop (only water is permeable) water passes out of the tubule through osmosis into the hypertonic environment of the medulla and then into the permeable capillaries, Filtrate then passes into the ascending loop which is only permeable to salt ions and sodium ions are actively pumped out of the filtrate and into the medulla which creates a hypertonic environment in the fluid. From the ascending portions of the loop of Henle filtrate moves into the distal convoluted tubule where it’s fine tuned and where toxins are secreted into the filtrate before moving into the collecting duct. The collecting duct reabsorbs water under the control of ADH
Explain the role of ADH in maintaining water and solute balance in the blood.
The amount of water that passes back into the blood from filtrate in the collecting ducts is controlled by ADH which is a hormone that acts on the walls of collecting ducts and produces more aquaporins that make the ducts more permeable to water allowing more to pass through. This makes urine less diluted and hypertonic, once properly hydrated ADH production slows or stops and less water is reabsorbed through the collecting ducts making urine more diluted.
Explain how and why the composition of blood is different in the renal artery and renal vein.
The composition of blood is different in the renal artery than in the renal vein because through all of the kindey’s process many things are removed and filtered out of the blood. For example glucose is selectively reabsorbed into the PCT, it’s co transported with Na ions into epithelial cells until equilibrium is reached and then it’s actively transported into epithelial cells after 50% reabsorbed until 100% reabsorbed. Water passes out of the PCT by osmosis into the hypertonic environment of the fluid in the medulla, the amount of water that passes back into the bloodstream is controlled by adh in the collecting duct. Walls then aquaporins the more water reabsorbed
