the kidney Flashcards
what are the effects of adh on urine production
ADH stimulates the addition of aquaporins into the membranes of the collecting duct cells, increasing the permeability of the collecting duct to water. As a result, more water is reabsorbed from the collecting duct into the blood by osmosis down a water potential gradient. This leads to a smaller volume of urine, which becomes more concentrated.
Explain the process of ultrafiltration in the nephron. What role does blood pressure play in this process?
Ultrafiltration occurs in the glomerulus, where blood is filtered into Bowman’s capsule. High blood pressure in the glomerulus, due to the afferent arteriole being wider than the efferent arteriole, creates a hydrostatic pressure in the glomerulus. This forces water, ions, and small molecules (like urea and glucose) through the capillary walls (endothelium, basement membrane and the gaps of the podocytes) and into Bowman’s capsule while larger molecules (like proteins and blood cells) remain in the blood.
Describe the adaptations of the proximal convoluted tubule (PCT) epithelial cells that facilitate the reabsorption of substances from the glomerular filtrate.
PCT epithelial cells are adapted for reabsorption by having microvilli to increase surface area for reabsorption of water, numerous mitochondria for ATP production for active transport, and specific transport proteins for co-transporting substances (like glucose and amino acids) with sodium ions. These adaptations maximize the efficiency of reabsorption.
What is the significance of the countercurrent mechanism in the Loop of Henle? How does it affect water reabsorption?
The countercurrent mechanism creates a gradient that allows for efficient reabsorption of water and ions. The descending limb is permeable to water so water moves out through osmosis, allowing it to exit into the surrounding medulla, while the ascending limb actively transports sodium and chlorine ions out, due to the impermeability of the ascending limb ( water stays inside the tubule) which lowering the water potential in the medulla and increases the water potential of the ascending limb. This gradient encourages water to move from the filtrate back into the bloodstream. at the bottom of the ascending limb, sodium and chloride ions diffuse out into the medulla and lowers the wp of the medulla
some desert mammals have longer loops of Henle compared to animals that do not live in desert conditions
More sodium and chloride ions are pumped out of the ascending limb into the medulla
this builds up a greater wp
more water is reasbsorbed from the filtrate so more water is returned to the blood from the collecting duct
Discuss the hormonal control of osmoregulation, focusing on the role of ADH (antidiuretic hormone) and its effects on the kidneys.
ADH is produced in the hypothalamus and released from the posterior pituitary gland in response to low blood water potential. It increases the permeability of the distal convoluted tubule (DCT) and collecting duct to water, promoting reabsorption and concentrating urine. When blood water potential is restored, ADH secretion decreases, reducing water reabsorption.
Compare and contrast hemodialysis and peritoneal dialysis. What are the advantages and disadvantages of each method?
Hemodialysis involves filtering blood through a machine with a semi-permeable membrane, effectively removing waste products. Advantages: efficient waste removal; Disadvantages: requires frequent hospital visits, risk of infection. Peritoneal dialysis involves using the peritoneal cavity for filtration with a dialysis fluid. Advantages: can be done at home; Disadvantages: less efficient than hemodialysis, risk of peritonitis.
How does kidney failure affect the Glomerular Filtration Rate (GFR)? Describe the clinical significance of measuring creatinine levels in the blood.
Kidney failure leads to a decreased GFR, indicating reduced kidney function and the inability to filter blood effectively. Elevated creatinine levels in the blood signal that the kidneys are not filtering waste properly, providing a key diagnostic marker for kidney damage or dysfunction.
Describe how pregnancy tests utilize antibodies to detect the presence of HCG in urine. What is the mechanism behind this test?
Pregnancy tests detect HCG through a method involving monoclonal antibodies. When urine is applied to the test, any HCG present binds to these antibodies, which are linked to colored beads. This complex moves to a section with immobilized antibodies specific to HCG, creating a colored line if HCG is present. A control line forms when unbound antibodies bind to different immobilized antibodies, confirming the test’s validity.
the part of the body that releases adh
posterior pituitary gland
some desert mammals secrete large amounts of ADH, explain how this adaptation to their environment
- more channel proteins makes the cells more permeable to water so more water is absorbed from the filtrate and less water is lost from the body
substances that are present in the glomerular filtrate?
water
glucose
urea
ions
explain how the glomerulus is able to carry out its function
- afferent arteriole has a greater diameter than the efferent arteriole so there is a build up of high hydrostatic pressure
- the endothelium wall has small pores to allow ultrafiltration
similarities between formation of tissue fluid and ultrafiltration
- both
