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Nephron: The Functioning Unit of The Kidney

Nephron: The Functioning Unit of The Kidney

Each of our kidneys contains over a million nephrons.  They are the functioning unit of the kidneys. They remove waste from the body and produces urine. Each nephron is made up of two parts: a renal corpuscle and renal tubules (Figure 1).

Figure 1. Schematic diagram of the nephron demonstrating the site of action of diuretics. Source: PostGraduate Medical Journal

Renal Corpuscle

  • This is the head of the nephron and it is where urine first forms.
  • It consists of the glomerulus, which is surrounded by the Bowman’s capsule (figure 2).
  • The glomerulus is like a network of capillaries. It look somewhat like a roll of yarn. The Bowman’s capsule, around the glomerulus, shapes like a funnel.
  • Blood is filtered across the glomerular capillaries into Bowman’s space. This is the first step in the formation of urine. Filtrates then exits the Bowman’s space into the renal tubules
  • Each renal corpuscle has  two poles:

(a) Vascular pole: this is where afferent arteriole enters the glomerulus and where efferent arterioles leave the glomerulus;

(b) Urinary pole: this is the area where filtrates produced by the glomerulus exits and enters the first part of the tubule.

Renal Tubule

  • Filtrates from the glomerulus enters the tubules where urine continually forms.
  • The tubule begins at the Bowman’s capsule and consists of various segments (Figure 1):
    1. Proximal convoluted tubule
    2. Proximal straight tubule
    3. Loop of Henle contains:
        • thin descending limb
        • thin ascending limb
        • thick ascending limb
    4. Distal convoluted tubule
    5. The collecting ducts
    1. Reabsorption
    2. Secretion
    3. Excretion
We will discuss the various section of the tubules in part 2 of the Nephrons.

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