Hormonal regulation of renal function ADH and water conservation ADH is synthesised in the cell bodies of hypothalamic nuclei (supraoptic nuclei) and transported to nerve fibre endings in the posterior lobe of the pituitary where it is stored in the secretory granules. Its release in the blood is controlled by osmoreceptors in the hypothalamus that […]

Excretion of dilute and concentrated urine Excretion of dilute urine When there is excess of water in the body and a reduction in plasma osmolarity, kidneys can excrete a dilute urine with a concentration as low as 50 mOsm/L. This can be achieved by reabsorbing only the solutes and not water in the distal parts

Counter current mechanism of kidney A counter current system of tubules or vessels exists where the inflow of fluid runs parallel to, counter to, and in close proximity to the outflow for some distance. These characteristics are common to the anatomical arrangements of the Loops of Henle and vasa recta. In the kidney, two counter

Renal mechanism of urine formation and Permeability of the tubules Renal mechanism of urine formation Renal mechanism of concentrated and dilute urine formation- Concentrated urine is formed by passive water reabsorption from the tubules while many solutes in the tubular fluid are absorbed by active process. Dilute urine is formed by absorption of solutes alone

Renal function tests Renal clearance is the measurement of the kidney’s ability to remove substances from the plasma. Clearance measurements are used to determine Renal Blood Flow (RBF),  Renal Plasma Flow (RPF), Glomerular Filtration Rate (GFR), Filtration Fraction (FF) and how different substances are handled by the kidney tubules (reabsorbed or secreted) and to compare

Uremia or Azotemia Uremia or azotemia, is the elevated level of waste products in the blood, particularly nitrogen-containing compounds like urea and creatinine. Urea is the chief nitrogenous end product of protein metabolism and is excreted by the kidneys in the urine of mammals. It is also found in the blood and lymph. Uremia is

Functions of the urinary bladder Urinary bladder provides an expandable reservoir for urine, which is continuously flowing from pelvis of the kidney through ureters. Micturition Micturition is the process in which the urinary bladder empties when it becomes filled with urine. Passage of Urine from the kidney to the bladder Urine is secreted continuously though

Reabsorption and secretion in different regions of tubules Water transport is by osmotic diffusion. Proximal tubule: 65% reabsorption. Loop of Henle: 15%. Distal tubule: 10%. Collecting duct: 9.3%. Urine: 0.7%. Glucose, proteins, amino acids, vitamins and acetoacetate ions are completely reabsorbed by active process in proximal tubule. 50% of urea is reabsorbed. Creatinine is not reabsorbed

Absorptive capabilities of different tubular segments Proximal tubule 65 % of the reabsorption and secretion take place. Only 35% of the GF leaves the proximal tubule. Thin segment of Loop of Henle Permeability of the epithetical cells of descending limb of Loop of Henle is great and occurs by simple diffusion. It is highly permeable

Tubular secretion Several substances are transported from the peritubular capillaries into the interstitial fluid and then to the tubular lumen via the tubular epithelial cells. Antiport of H+ along with Na2+ reabsorption in the proximal tubule and distal tubule. H­+ is secreted throughout the nephron. K+ transport is unique, in that it is reabsorbed in some parts of the tubule