Question

Think about the formation of urine. Imagine that you are describing the journey of a drop of blood, from the hepatic artery, to the production of glomerular filtrate, to the excretion of urine. What are the structures that the blood/GFR/urine will pass through, and what processes is the product exposed to? In other words - how is urine produced from the vantage point of a single drop of blood in the hepatic artery? Once you have described the normal process for this, pick one of the pathologies below and describe how the process of urine formation would be different in an individual with your chosen pathology.

Choose one:

Polycystic kidney disease

Urinary tract infection

Glomerulonephritis

Lupus nephritis

Diabetic kidney disease

Answer 1

• Urine formation involves 3 process , Filtration, reabsorption and secretion.
• On an average 1100ml of blood is filtered by kidney About 20% of total cardiac output is reach in kidney, which is know as renal plasma flow
• Glomerular pressure in the glomerulus causing filtration  of blood through 3 layers.
• Epithelial cells of bowmans capsule called podocytes are arranged in an intricate manner so as to leave some space called filtration slits.
• Blood is filtered so finely through the membrane, almost all constituents of plasma except protein pass into the lumen of Bowmans capsule.This process is called ultra filtration.
• Amount of filtrate formed in kidney per minute is called GFR ( Glomerular filtration rate), which is 125 ml/ minute
• Urine released per day is 1.5 L , so it is 99% is reabsorbed, this process is called reabsorption.
• Substance like glucose ,amino acid , sodium ions,in the filtrate are reabsorbed actively where as nitrogenous waste are absorbed passively.
• Reabsorption of water also occur in intial segment of nephron.
• During urine formation , tubular cells secrete Hydrogen ion, potassium ion,ammonia into the filtrate.
• Secretion is an important in maintenance of ionic and acid base balance of body fluids.
• Proximal convoluted tubule (PCT) : Nearly all essential nutrients and 70-80% of electrolytes and water are reabsorbed by this segment.
• Henle's loop: reabsorption in this region is minimum,but it play an important role in maintenance of high osmolarity of medullary interstitial fluid.
• Distal convoluted tubule (DCT); conditional reabsorption of sodium and water takes place in this region.
• Collecting duct: large amount of water is reabsorbed in this region and allow passage of urea into medullary interstitum.
• A counter current pattern of 2 limbs of henle's loop and vasarecta play an important role in concentration of urine.
• from collecting duct , urine flow into kidney and then through ureter into urinary bladder for storage. From the bladder it is micturated out.

Glomerulonephritis

• It is the inflammation of glomerular membrane, which leads to impairment in reabsorption process.
• Hence large amount of protein and red blood cells, are seen in urine
• There will be pain , when micturition, edema etc..
• There will be change in secretion and reabsorption process.