Urinary system

Anatomical structure urethra The kidney present in the lower back of t the abdominal wall Adrenal gland kidney ureter Urinary bladder urethra

The nephrone Bowman’s capsule and glomerulus

The nephrone

Nepherone Its small functional unit, which is equal one million on each kidney. Its two types: 1) cortical nepheron (85%), responsible for formation of urine 2) medullary nepheron (15%), responsible for concenration of the urine

Structure of the nephron the kidney is composed of about 1 million functional units called nephron. one nephrone consist of : 1-glomerular capsule (Bowman”s capsule & glomerulus) 2- the proximal convoluted tubule 3- loop of Henle ( medullary (long) and cortex (short) loop) 4- distal convoluting tubule 5- collecting duct

function of cortical nephrone ((Urine formation Glumerular filtration (movement of the blood from glumorulus toward Bowman’s capsule) Tubular reabsorption (movement of filtrated fluids from convoluted tubules toward the blood) Secretion (movement of the blood from the blood capillaries around the tubules toward convoluted tubules) excretion (movement of filtrated blood from renal tube to outside the body)

I- Glumerular filtration Glumerular filtration is move the fluid (plasma-protein) from glumorulus toward Bowman’s capsule. Glumerular filtration depends on three pressures. These pressures are: 1) glomerular capillary hydrostatic pressure (60 mmHg) 2) intracapsular pressure (18 mmHg) 3) colloidal pressure (plasma protein pressure) (25mmHg)

(Glomerular filtration rate) GFR Definition: its volume of the blood filtrate from the glomeruli into Bowman`s space per unit time. Normal value: in 70Kg person the volume of filtration equal 125ml\min or 180L\day. plasma volume filtrate by the kidney is about 60 times a day

II- Tubular reabsorbtion (movement of filtrated fluids from convoluted tubules toward the blood) This process help to maintain fluids and electrolyte balance and blood PH Proximal tubule 1- glucose all glucose molecules filtrated in Bowman’s capsule are reabsorbed again toward the blood by active transport process. Tubular maximum absorption for glucose is equal 300mg/ min Normal amount of glucose in the blood is about 100mg/ 100ml If the amount of glucose in the blood is more than 180mg/100ml the glucose molecules will appear the urine (glucouria)

Proximal tubule 2- protein Small amount of protein filtrated from Bowman’s capsule (30-50mg\day), but its reabsorbed again in proximal tubule by active transpose process If the protein molecule not absorbed due to kidney diseases, it will appear in the urine (albuminuria)

Proximal tubule 3- water and electrolyte (Na) 70% of water and Na reabsorbed in proximal tubule by active transport 4- urea 50% of urea absorbed

Lube of Henley 20-30% of water and electrolyte absorbed in lube of Henley by diffusion for the water and active transport for electrolyte (descending lube of Henley is thin and mainly its reabsorbed the water, but ascending lube of Henley is thick and reabsorbed Na and electrolytes)