Urinary systemUrinary system

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Anatomical structure

The kidney present in the lower back of t the

abdominal wall

kidney

ureter

Urinary bladder urethra

Adrenal gland

The nephroneBowman’s capsule and glomerulus

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The nephrone

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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

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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

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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)

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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)8

(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

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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)

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• 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)

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• 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

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• 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)

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