Question

1. Urine formation review

2. What are the factors that influence the net filtration rate?

Answer 1

answer

urine is the end product of blood purification occuring in kidneys . kidneys functional units are known as nephrons , each kidney contain millions of nephrones . each nephron has parts like bowmans capsule , proximal convoluted tubules , loop of henle , distal convoluted tubules . urine forme from each nephrone are collectively reached the collecting duct , from there through the minor and major calyx within kidney reaches rensal pelvis , and from there urine is draine to bladder through muscular tubue structure known as ureter , from bladder urine drained out through urethra.

each nephrones are surrounded by some small cappilaries , which aid in the secretion and reabsorbtion of some substances between these blood vessels and the tubules . GFR (glomerular filtration rate ) is used to check how the kidneys are functioning , it is estimation of how much blood passes through each glomeruli each minute . noomal GFR is around 125 ml/ minute . as the blood flow through the afferent arterioles there is a process of filtration occurs , which allows some substances like water , sodium , sugar , potasium , ammonia , bicarbonate, urea .. to pass into the bowmans capsules and in to the tubules , while passing through these tubules most of the water and electrolytes and other essential nutrients needed for body are reabsorbed into the blood vessels mainly due to the concentration gradient occuring between the renal cortex and medulla . so when urine flows from proximal tubules towards the distal tubules through the loop of henley , most of the water are reabsorbed into the circulation and the end product will be more concentrated with full of bodys unwanted waste products like urea, ammonia , crystals ...

the amount of GFR formation will depond on some forces like hydrostatic pressure of capsule and glomeruli , osmotic pressure of blood and capsule . the net filtration presure will affect the direction of filtration . if the filtration pressure is high or in positive pressure , there will be more filtration of blood occurs and hence GFR increases and vice versa.

increased glomerular hydrostatic pressure ,capsular osmotic pressure and decreased capsular hydrostatic pressure and blood colloid osmotic pressure will increases GFR .

normal values are , glomerular hydrostatic pressure = 55 mmhg

capsular hydrostatic pressure = 15 mmhg

blood colloid osmotic pressure = 30 mmhg

capsular osmotic pressure = 0 mmhg

so net filtration pressure ={ glomerular hydrostatic pressure +capsular osmotic pressure } - {capsular hydrostatic pressure + blood colloid osmotic pressure }

= 55 -{30 +15 mmhg}

= 10 mmhg