- Urinary system consists kidney, ureters, urinary bladder and urethra.
- After the kidney filter blood and return most water nd many solutes to the blood history. The remaining water and solutes constitute is urine.
- The kidney regulates blood ioning composition , blood osmolarity, blood volume, blood pressure and blood pH.
- The kidney also performed gluconeogenesis release calcitriole and erythro-poetium, excrete wastage and foreign substances.
Anatomy of kidney:
- The kidney are retroperitoneal organ attest to the posterior abdominal wall.
- Three layers of the tissue surround the kidney renal capsule, edipose capsule and renal fascia.
- Internally the kidney consists of renal cortex, a renal medulla , a renal pyramid, a renal papilla, calyxes and a renal pelvis.
- The blood flow into the kidney by the renal artery and collected the blood from the kidney by renal vein.
- Vaso motar nerve for the sympathetic resion of airless supply blood vessels. They help regulate flow of blood through kidney.
- The nephron is the functional units of the kidney it contain glomerulus , bowman’s capsule and renal tubules.
- The renal tube consists of proximal convoluted duct , a loop of henel and a distal convoluted duct which drain into a collecting duct. The loop of Henley consists descending and ascending limb.
A nephron perform three basic tasks-
- Glomerulus filtration
- Tubular reabsorption
- Tubular secretion
- Fluid that enter into capsular space is glomerulus filtrate.
- The filtration membrane consists of the glomerulur endothelium, vessels lamina and filtration slips between padicel of podocytes.
- Most substance in blood plasma easily passage through the glomerulus filter however blood cells and most protein normally are not filtered.
- Glomerulus filtrate amount to upto 180 liter of fluid per day. This large amount of fluid is filtered because the filter is porous, thin, glomerulus capillary blood pressure is high.
- Glomerulus blood hydrostatic pressure (GBHP) promotfiltration where as capsular hydrostatic pressure (CHP) and blood colloidal osmotic pressure (BCOP) opposed filtration.
- The net filtration pressure and
- NFP= GBHP-CHP-BCOP
- It is about 10 mg Hg.
- Glomerulus filtration rate is the amount of filtrate in both kidney per minute is normally 105-125ml/min.
- The Glomerulus filtration rate depend on renal auto-regulation, neural regulation and hormonal regulation.
Tubular Reabsorption and Tubular Secretion:
- Tubular reabsorption is a selective process that reclaim material from tubular fluid and return than to the blood steam.
- Reabsorption substance include water, glucose, amino acid, urea and ions. Such as sodium, potassium , bicarbonate and phosphate.
- Some substance not need by the body are removed from the blood and discharge into the urine. Via tubular second include paracelluar and transcellular route.
- The maximum amount of substance that can be the absorb per unit time is called transport maximum.
- About 90% of water reabsorb is obligatory it occurs via osmosis together reabsorption of solute.
- The remaining 10% is facultative water reabsorb which varies according to body may and is regulated by ADH.
- Sodium ions are reabsorb through out the baso lateral membrane.
- In the proximal convulet tubes a sodium ions are reabsosrb through the africal membrane via sodium glucose symporter and sodium, hydrogen, antiporter.
- Water is reabsorption via osmosis chloride, potassium ,calcium, magnesium and urea are reabsorb via passive diffusion and ammonia ,ammonium are secreted.
- The loop of henly reabsorb 20-30% of the filtered sodium, potassium, calcium 35% of the filtered chlorides and 15% of filtered water.
- A distal converted tubules reabsorb . So , chlorides ions , via, sodium, potassium symporter.In the collecting ducts principal cells reabsorb sodium.
- Angiotensin-II, aldo sterone, ATH and atrial natriuratic peptide regulate solute and water absorption.