The Urinary System

 

 
13.2

The Urinary System

 
  • Important organs involved in homeostasis are kidney and heart
  • Functions of kidney:
    • Control the composition of water and salts in the body (osmotic pressure) 
    • Controls blood pH
    • Remove and excrete waste by the formation of urine
  • Each kidney consists of millions of nephrons
    • Nephron consists of:
      • Bowman's capsule
      • Loop of Henle
      • Proximal convoluted tubule
      • Glomerulus
      • Distal convoluted tubule
      • Inside the Bowman's capsule, there is a tangled capillary network called glomerulus
 
Formation of urine:
 
Source:[Text Book Biology KSSM Form 4]
 
Process of urine formation:
 

Ultrafiltration:

  • Afferent arteriole has a larger diameter than the efferent arteriole
  • Thus, it results in high pressure on the blood flow in the glomerulus
  • This causes certain blood components to filter out into the Bowman's capsule
  • The glomerulus filtrate inside the Bowman's capsule is the same as the blood plasma, except it does not contain plasma protein, red blood cells, and platelets

Reabsorption:

  • Components in the glomerulus filtrate are water, urea, glucose, amino acids and salt
  • Reabsorption occurs when the substances re-enter the blood capillaries along the renal tubule

Secretion:

  • Secretion occurs when waste substances are secreted out from the blood capillaries and into the renal tubule (distal convoluted tubule)
 

Osmoregulation: A process that regulates water and salt balance in the body in order to maintain a normal blood osmotic pressure

  • When the water content is more, the salt content is low (low blood osmotic pressure)
  • When the salt content is more, water content is low (high blood osmotic pressure)
 

 

The Urinary System

 

 
13.2

The Urinary System

 
  • Important organs involved in homeostasis are kidney and heart
  • Functions of kidney:
    • Control the composition of water and salts in the body (osmotic pressure) 
    • Controls blood pH
    • Remove and excrete waste by the formation of urine
  • Each kidney consists of millions of nephrons
    • Nephron consists of:
      • Bowman's capsule
      • Loop of Henle
      • Proximal convoluted tubule
      • Glomerulus
      • Distal convoluted tubule
      • Inside the Bowman's capsule, there is a tangled capillary network called glomerulus
 
Formation of urine:
 
Source:[Text Book Biology KSSM Form 4]
 
Process of urine formation:
 

Ultrafiltration:

  • Afferent arteriole has a larger diameter than the efferent arteriole
  • Thus, it results in high pressure on the blood flow in the glomerulus
  • This causes certain blood components to filter out into the Bowman's capsule
  • The glomerulus filtrate inside the Bowman's capsule is the same as the blood plasma, except it does not contain plasma protein, red blood cells, and platelets

Reabsorption:

  • Components in the glomerulus filtrate are water, urea, glucose, amino acids and salt
  • Reabsorption occurs when the substances re-enter the blood capillaries along the renal tubule

Secretion:

  • Secretion occurs when waste substances are secreted out from the blood capillaries and into the renal tubule (distal convoluted tubule)
 

Osmoregulation: A process that regulates water and salt balance in the body in order to maintain a normal blood osmotic pressure

  • When the water content is more, the salt content is low (low blood osmotic pressure)
  • When the salt content is more, water content is low (high blood osmotic pressure)