Nephron Physiology Lecture Notes

Overview

• Presenter: Sarah from RegisteredNurstrn.com
• Topic: Nephron physiology as part of the NCLEX review series on the renal system.
• Objective: Understand the process of filtration, reabsorption, secretion, and excretion in nephron physiology.
• Recommendation: Check other videos in the series and take the quiz at the end.

Kidney and Nephron Anatomy Recap

• Function of Kidneys: Filter blood by receiving oxygenated blood from the heart via the renal artery.
• Nephron Structure: Each kidney has millions of nephrons located in the cortex and medulla.
• Urine Flow Pathway: Renal pyramid → Renal papilla → Minor/Major calyx → Renal pelvis → Ureter → Bladder → Urethra.

Nephron Sections

1. Renal Corpuscle:
   • Components: Glomerulus and Bowman's capsule.
   • Function: Filters blood.
2. Renal Tubules:
   • Function: Reabsorption and secretion.
   • Involvement: Peritubular capillaries surround nephron to aid reabsorption and secretion.

Nephron Filtration Process

• Glomerulus:
  • Mesh of circular capillaries causing high pressure for ultrafiltration.
  • Receives blood via afferent arteriole.
  • Filtrate Components: Water, glucose, amino acids, ions (calcium, potassium, magnesium, phosphate, chloride), urea, creatinine.
  • Exclusion: Blood cells and proteins are not filtered.

Tubular Reabsorption and Secretion

1. Proximal Convoluted Tubule:

   • Reabsorbs: Glucose, amino acids, bicarbonate, water, sodium, chloride, various ions, and urea.
   • Secretes: Uric acid, antibiotics, drugs (e.g., diuretics).

2. Loop of Henle:

   • Descending Limb: Permeable to water, reabsorbs water due to hypertonic medulla.
   • Ascending Limb: Permeable to ions (sodium, chloride, potassium), maintains medulla’s osmolarity.
   • Function: Concentrates urine and aids water reabsorption.

3. Distal Convoluted Tubule:

   • Reabsorbs: Sodium, water (influenced by aldosterone), calcium (influenced by parathyroid hormone), bicarbonate.
   • Secretes: Potassium, hydrogen ions.

4. Collecting Tubule:

   • Reabsorbs: Sodium, water (under antidiuretic hormone influence), urea.
   • Final Pathway: Filtrate exits nephron, becomes urine with waste products.

Urine Composition

• End Products in Urine: Urea, water, creatinine, excess ions (sodium, chloride, potassium, magnesium, phosphate, calcium).

Conclusion

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