Distal convoluted tubule : no brush border, forms macula densa
Collecting duct- P & I cells(acid secretion), adjusts volume & concentration of urine
Glomerulus has large pores(4-8 nm)also has sialoproteins in basement membrane âvely charged repel protein & prevent their filtration, allowing filtration of large volumes of fluid
Number of nephrons declines with age, to about 50% at age 60; this causes the GFR to drop to 50% of value in a young person
Kidney receives 1.2-1.3 L/min blood (25% of cardiac output) at rest.
Normal GFR is 125ml/min or 180L/day.
Net filtration pressure (PUF) is 10 mmHg.
Renal plasma flow is measured by p-amino hippuric acid(PAH).
Mesangial cells do not form filtration barrier.
Electrolytes such as sodium (Na+), and small organic compounds such as glucose, inulin are freely filterd (filterability =- 1)
Myoglobin and albumin are not filtered
Negatively charged large molecules are filtered less easily than positively charged molecules of equal molecular size.
Inulin is the standard substance and extensively used to measure GFR.
Juxtaglomerular Apparatus: 1)Juxtaglomerular cells â modified smooth muscle cells in tunica media of the afferent arteriole. Contain renin. Act as volume receptors 2) Macula Densa cells : formed by DCT. Act as Na+ sensor 3) Lacis or mesengial cells : contractile, secrete chemicals.
Renal vasodilation : Dopamine, PGs, Ach, High protein diet
Renal vasoconstriction: angiotensin II (efferent more than afferent arteriole), NE (opposite)
Renal clearance: it is a measurement of the renal excretion ability, it is given by UV/P
U = urinary conc. of a substance V= urine flow rate in ml/min P= plasma conc. of a substance
If renal clearance is more than GFR- tubular secretion, If renal clearance is less than GFR -tubular reabsorption., If no sec and no reabsorption then Clearance = GFR (inulin)
Transport maximum TmG for glucose in normal adult is 375 mg/min., Renal threshold is 180-200 mg%
Water reabsorption in DCT- early part of distal tubular is impermaeable to water. Late part of DCT becomes permeable under the influence of ADH.
The segments of nephron that are impermeable to water: thin ascending limb, thick ascending limb, 1st part of distal tubule (DCT)
Hyperosmolarity is due to high Na+ , K+, Cl- & Urea in renal medulla.
Acidification of tubular fluid starts in distal nephron, maximum the collecting duct (CD), but maximum secretion of acid in PCT (pH remain unchanged due to buffers in PCT , like bicarbonate, phosphate and ammonia (from glutamine)
Concentration of urine depends on the action of ADH and Counter current system.
The minimum volume of urine necessary to remove all products is 500 ml/day and is called obligatory volume.
The amount of protein in urine is normally less than 100 mg/day.
First urge to void is felt at a bladder volume of 150 ml and a marked sense of fullness at about 400mL in adult the volume of urine that normally initiates a reflex contraction is about 300Â-400mL
Concentration and dilution of urine i.e free water and osmotic clearances is regulated by anti diuretic hormone (ADH).
The only physiological stimulus for erythropoietin secretion is hypoxia or decreased partial pressure of oxygen.
Erythropoietin is a plasma protein that act as a hormone. It's a major regulator of human erythropoiesis.
Vasopressin acts by increasing permeability of collecting ducts to water. itopens aquaporin-2 via V2 receptors increasing cAMP.
Anion Gap- Represents unmeasured anions in plasma
High anion gap - lactic acidosis, diabetic ketoacidosis, alcoholic ketoacidosis, starvation, renal failure.
Non- anion gap- Diarrhoea, uretero sigmoidostomy. Normal level of creatinine in serum is 0.6 to 1.2 mg%
Test Your Skills
Test Your Skills Now!
This is only a practice test, it is designed to help you revise your concepts
The test contains questions, only 1 option is correct for each question
This is a timed test.
After you have finished the test, press on the 'Finish Test' button to know your score and get the correct answers