1. Each kidneys contains approximately one to two million tiny functional units (nephrons).
2. Each nephron consists of:
- Bowman’s capsule
- proximal convoluted tubule
- loop of Henle
- distal convoluted tubule
- collecting duct.
- enters kidney through renal artery
- leaves through renal vein.
- afferent arteriole carries blood à to glomerulus
- efferent arteriole carries blood ßout of glomerulus.
5. High blood pressure (in glomerulus) forces blood plasma à into Bowson’s capsule due to:à renal artery is short + close to aorta.
à diameter of the efferent arteriole is smaller than afferent arteriole.
1. Three processes involved in the urine formation are:- ultrafilteration,
2. Ultrafilteration:- a process
- blood plasma is forced out from the glomerulus
- into the Bowman’s capsule
- due to high hydrostatic pressure.
3. Glomerular filtrate contains:- ions,
- nitrogenous waste.
4. Reabsorption of glucose + amino acids- occurs at the proximal convoluted tubule
- an active transport.
5. Reabsorption of water:- occurs at descending limb of loop of Henle.
6. Secretion of hydrogen ions (H+), creatinine, and toxic waste- occurs at distal convoluted tubule.
- reabsorbed at collecting duct.
- composition of urine = ions, urea, water, toxins + creatinine.
1. Osmoreceptors (in hypothalamus) - constantly monitor the amount of water in blood.
è released by the posterior lobe of pituitary
è regulates the reabsorption of the water
è by kidney.
3. When osmotic pressure (OP↑) in blood increase:è ADH is secreted
è increases permeability of collecting duct + distal tubule
è to reabsorb more water.
è Consequently, less more concentrated urine is produces.
4. When osmotic pressure (OP↓) decreases:è adrenal cortex releases aldosterone (2nd hormone)
è stimulates distal convoluted tubule + collecting duct
è to reabsorb more sodium ions (Na+)
è thru active transport,
è increases blood volume ↑.
è regulates blood concentration + volume.
5. rennin-angiotensin mechanismà trigger the release of aldosterone.
è a system
è which brings an imbalance back to normal
è by responding to a condition it controls.
7. Blood pH is maintained - between 7.35 to 7.45.- relative exchange of bicarbonate (HCO3-) + hydrogen ions (H+)
- between blood + tubules
- help adjust acid-base balance of blood.
8. When blood pH ↓ decreases:
- H+ are secreted into distal tubule
- while HCO3- are reabsorbed,
- resulting in blood pH returning to normal.
9. When blood pH ↑ increases:- HCO3- will be removed
- from blood àinto distal tubule.
- few H+ à move into blood capillary.
10. Urine pH vary between 4.5 - 8.2 (normal pH = 6.0).