Week 4 L1 - Renal Lecture Overview and Functions of the Kidney

Introduction to Renal Lecture

  • Welcome of BMS 2031 students to first renal lecture.

  • Focus areas: functions of the kidney and process of urine formation.

Resources and References

  • Prescribed textbook: 'Vander's Human Physiology', 15th edition.

  • Coverage of renal function scheduled for second workshop in Week 4.

  • Links to supportive resources on Moodle:

    • Khan Academy videos on renal physiology.

    • Renal physiology revision quiz.

Learning Objectives

  • After completion of the lecture and associated reading, students should be able to:

    • List four functions of the kidney and relate symptoms of renal disease to these functions.

    • Identify major anatomical features of the nephron, including renal corpuscle and renal tubules.

    • Describe the glomerular filtration barrier.

    • Draw and label a diagram illustrating solute and fluid renal reabsorption from the tubular lumen to the peritubular capillaries, including the transport maximum concept using glucose as an example.

Overview of the Urinary System

  • The urinary system consists of:

    • Kidneys: Typically two in number (Note: anecdote about an individual with one kidney).

    • Ureters: Tubes that drain urine formed by the kidneys into the bladder.

    • Bladder: Stores urine before it is expelled from the body.

    • Urethra: Leads urine out of the body.

  • Anatomical reference made to the muscular diaphragm.

Personal Anecdote: Kidney Transplant Experience

  • Recommendation to view a video by Brooke Huskas, a former teaching associate and kidney transplant recipient.

  • Video discusses:

    • Effects of failing kidneys on health and lifestyle modifications.

    • Dietary changes (e.g., reduced salt and potassium).

Functions of the Kidneys

  • Common misconception: kidneys only remove waste.

  • Enumerated functions of the kidneys:

    1. Regulation of body water and electrolytes:

    • Maintains fluid volumes and osmolarities.

    • Key ions regulated:

      • Sodium (Na^+)

      • Chloride (Cl^-)

      • Potassium (K^+)

      • Calcium (Ca^2+)

      • Phosphate (PO_4^{3-})

      • Magnesium (Mg^2+)

    1. Regulation of arterial blood pressure:

    • Impact of total body sodium and water regulation.

    1. Acid-base balance:

    • Regulation of pH via hydrogen ion levels.

    1. Excretion of metabolic waste products and foreign substances:

    • Examples include nitrogenous wastes (urea, ammonium), drugs, pesticides.

    1. Endocrine functions:

    • Hormones secreted include:

      • Renin: Involved in angiotensin II formation; plays a role in sodium control and blood pressure regulation.

      • Erythropoietin: Stimulates red blood cell production, secreted by kidneys.

      • 125 Dihydroxyvitamin D3: Involved in calcium homeostasis.

    1. Gluconeogenesis:

    • Conversion of amino acids to glucose in kidneys.

Symptoms of Renal Dysfunction

  • Common symptoms related to kidney function:

    1. Hypertension: High blood pressure resulting from fluid and sodium imbalance.

    2. Oedema: Accumulation of extracellular fluids indicating fluid balance issues.

    3. Metabolic acidosis: Resultant from failure to excrete hydrogen ions and reabsorb bicarbonate.

    4. Anaemia: Low red blood cell count due to decreased erythropoietin production.

    5. Osteoporosis: Associated with improper calcium regulation.

    6. Thirst: Increased thirst due to water imbalance.

    7. Malnutrition: Potentially linked to glucose level changes.

    8. Hyperkalemia: Elevated potassium levels, dangerous due to impact on excitable cells.

    9. Cognitive impairment: Related to abnormalities in sodium and potassium plasma levels.

Anatomy of the Kidney

  • The kidney has distinct regions:

    • Renal Cortex: Outer region of the kidney.

    • Renal Medulla: Inner region with cone-shaped structures called renal papillae.

  • Renal structures function to funnel filtrate into renal pelvis and subsequently into the ureter.

Nephron: Functional Unit of the Kidney

  • Nephrons: At least 1 million per kidney.

    • Two main components:

    1. Renal Corpuscle

    2. Renal Tubules

  • Renal Corpuscle: Comprised of:

    • Glomerulus: Capillary loops fed by afferent renal arteriole, draining via the efferent renal arteriole.

    • Unique structure: arteriole to capillary bed to another arteriole (maintains high pressure).

    • Bowman's Capsule: Fluid-filled capsule surrounding the glomerulus.

Components of Renal Tubules

  • Sequence of renal tubules:

    1. Proximal Tubule: Receives filtrate from Bowman's Capsule.

    2. Loop of Henle: Structure includes thin descending portion and thick ascending portion located in the renal medulla.

    3. Distal Convoluted Tubule: Further processes filtrate before it enters the collecting ducts.

    4. Collecting Ducts: Final pathway for filtrate leading to the ureter.