Nephron Structure and Function

Nephron Structure

• Definition: Nephrons are the functional units of the kidney responsible for filtering blood and producing urine.

• Components of Nephron:

  1. Renal Corpuscle:

     • Glomerulus: A network of capillaries where filtration occurs. Blood pressure forces water and solutes out of the blood.
     • Bowman's Capsule: A cup-like structure that encases the glomerulus and collects the filtrate.

  2. Renal Tubule:

     • Proximal Convoluted Tubule (PCT):
       • First segment after Bowman's capsule.
       • Reabsorbs nutrients (glucose, amino acids), ions (Na+, Cl-), and water from the filtrate.
     • Loop of Henle:
       • Has a descending limb (permeable to water) and an ascending limb (permeable to salts).
       • Establishes concentration gradient in the kidney.
     • Distal Convoluted Tubule (DCT):
       • Further modifies filtrate, reabsorbing ions and water based on body needs.
       • Site of secretion for certain ions and substances (e.g., potassium, hydrogen ions).

  3. Collecting Duct:

     • Receives filtrate from multiple nephrons.
     • Final site for water reabsorption, influenced by hormones (e.g., ADH).

• Types of Nephrons:

  1. Cortical Nephrons:
     • Located primarily in the kidney cortex.
     • Shorter loops of Henle.
  2. Juxtamedullary Nephrons:
     • Located near the medulla.
     • Longer loops of Henle, essential for concentrating urine.

• Juxtaglomerular Apparatus:

  • A specialized structure formed by the distal convoluted tubule and afferent arterioles.
  • Regulates blood pressure and filtration rate through the secretion of renin.

• Functionality:

  • Each nephron filters blood, reabsorbs essential substances, and secretes wastes into urine.
  • Approximately 1 million nephrons per kidney, ensuring efficient waste removal and homeostasis.

Nephron Structure

• Nephrons are the kidney's functional units, critical for blood filtration and urine production.

Components of Nephron

• Renal Corpuscle

  • Glomerulus: A capillary network where blood filtration occurs, facilitated by blood pressure that pushes water and solutes out.
  • Bowman's Capsule: A cup-like structure surrounding the glomerulus, responsible for collecting the filtrate.

• Renal Tubule

  • Proximal Convoluted Tubule (PCT):
    • First segment post-Bowman's capsule.
    • Reabsorbs vital nutrients (such as glucose and amino acids), ions (Na+, Cl-), and water.
  • Loop of Henle:
    • Comprises a descending limb (water-permeable) and an ascending limb (salt-permeable).
    • Establishes an osmotic gradient critical for urine concentration.
  • Distal Convoluted Tubule (DCT):
    • Further adjusts filtrate composition, reabsorbing ions and water based on physiological demands.
    • Secretes specific ions and substances like potassium and hydrogen ions.

• Collecting Duct

  • Receives filtrate from multiple nephrons.
  • Serves as the final site for water reabsorption, influenced by hormones like antidiuretic hormone (ADH).

Types of Nephrons

• Cortical Nephrons:
  • Predominantly located in the kidney cortex.
  • Feature shorter loops of Henle.
• Juxtamedullary Nephrons:
  • Positioned near the medulla.
  • Contain longer loops of Henle, crucial for urine concentration.

Juxtaglomerular Apparatus

• A structure formed by the distal convoluted tubule and afferent arterioles.
• Plays a key role in regulating blood pressure and filtration rate by secreting renin.

Functionality

• Each nephron filters blood, reabsorbs essential substances, and secretes waste into urine.
• The human kidney contains approximately 1 million nephrons, ensuring effective waste management and homeostasis.