The Mammalian Kidney: Structure (OCR A Level Biology): Revision Note

The Mammalian Kidney: Structure

• Humans have two kidneys

• The kidneys are responsible for carrying out two very important functions:

  • As an osmoregulatory organ - they regulate the water content of the blood (vital for maintaining blood pressure)

  • As an excretory organ - they excrete the toxic waste products of metabolism (such as urea) and substances in excess of requirements (such as salts)

The position of the kidneys and their associated structures

Kidney Function & Structure Table

• The kidney itself is surrounded by a fairly tough outer layer known as the fibrous capsule

• Beneath the fibrous capsule, the kidney has three main areas:

  • The cortex (contains the glomerulus, as well as the Bowman’s capsule, proximal convoluted tubule, and distal convoluted tubule of the nephrons)

  • The medulla (contains the loop of Henle and collecting duct of the nephrons)

  • The renal pelvis (where the ureter joins the kidney)

A cross-section of a kidney (as seen when cut in half vertically)

• Each kidney contains thousands of tiny tubes, known as nephrons

• The nephron is the functional unit of the kidney – the nephrons are responsible for the formation of urine

The location and structure of a nephron

• There is also a network of blood vessels associated with each nephron:

  • Within the Bowman’s capsule of each nephron is a structure known as the glomerulus

  • Each glomerulus is supplied with blood by an afferent arteriole (which carries blood from the renal artery)

  • The capillaries of the glomerulus rejoin to form an efferent arteriole

  • Blood then flows from the efferent arteriole into a network of capillaries that run closely alongside the rest of the nephron

  • Blood from these capillaries eventually flows into the renal vein

The blood supply associated with a nephron