OCR A Level Biology

Revision Notes

5.2.5 The Mammalian Kidney: Structure

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 urinary system in humans, IGCSE & GCSE Chemistry revision notes

The position of the kidneys and their associated structures

Kidney Function & Structure Table

The function of the kidneys and their associated structures, downloadable AS & A Level Biology revision notes

  • 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


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