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Bio Urinary system Lecture

Introduction to the Urinary System

  • Overview of the renal system and its components.

  • Focus on the nephron as the functional unit of the kidneys.

Nephron Structure

  • Bowman's Capsule:

    • Circular structure containing capillaries involved in blood filtration.

    • Essential for renal function and urine formation.

  • Tubules:

    • Distal Convoluted Tubule (DCT) marked on images.

    • Series of tubes in the nephron that process filtrate into urine.

  • Filtration Process:

    • Blood filtration through nephrons leads to urine production.

    • Reabsorption of water, sodium, and other ions back into the blood.

Anatomy of the Kidney

  • Blood Flow in Kidneys:

    • Renal vein and artery visible; important for blood flow.

    • Hilum: entry/exit point for blood vessels and nerves.

    • Ureters carry urine from kidneys to bladder.

Urinary System Components

  • Includes kidneys, ureters, bladder, and urethra.

  • Functional purpose: maintaining fluid homeostasis, blood composition, and pH levels.

  • Fluid levels significantly affect body physiology.

Fluid Homeostasis

  • Regulation of blood volume and composition.

  • Importance of electrolytes (sodium, potassium, chloride).

  • Regulation of blood pH through urine secretions and reabsorption.

Hormonal Regulation

  • Erythropoietin:

    • Stimulates red blood cell production based on blood oxygen levels.

  • Kidneys also assist in regulating blood glucose levels.

Blood Osmolarity and Pressure Regulation

  • Kidneys maintain osmolarity: concentration of dissolved substances in blood.

  • Hydrostatic pressure and colloid osmotic pressure are crucial for fluid exchange.

Excretion of Metabolic Waste

  • Kidneys filter out urea (from amino acids), drugs, and toxins from blood.

  • Important for body detoxification and waste elimination.

Renal Anatomy Details

  • Retropenitoneal Position:

    • Kidneys are located behind the peritoneal cavity.

  • Supportive Structures:

    • Renal fascia, adipose capsule, and renal capsule protect kidneys.

Functional Units of the Kidney (Nephrons)

  • Each kidney contains ~1.5 million nephrons.

  • Nephrons consist of:

    • Renal Corpuscle: Bowman's capsule + glomerulus for filtration.

    • Renal Tubule: Pathway for filtrate adjustment and processing.

Filtration and Reabsorption Process

  • Glomerular Filtration:

    • High hydrostatic pressure forces substances through filtration membrane.

  • Reabsorption:

    • Useful substances return to blood from nephron tubules.

  • Secretion:

    • Unwanted substances from blood enter nephron to form urine.

Forces in Filtration

  • Glomerular Blood Hydrostatic Pressure (55 mmHg):

    • Drives filtration process.

  • Capsular Hydrostatic Pressure (15 mmHg):

    • Opposes filtration.

  • Blood Colloid Osmotic Pressure (30 mmHg):

    • Also opposes filtration.

  • Resultant net filtration pressure indicates whether substances are pushed into Bowman's capsule.

Composition of Filtrate and Urine

  • Filtrate: includes water and small solutes (ions, glucose) but not large proteins.

  • Urine: waste products left after reabsorption.

Filtration Rate (GFR)

  • Average GFR:

    • Males: 125 ml/min, Females: 105 ml/min.

  • Importance of maintaining GFR for homeostasis.

Regulation of GFR

  • Autoregulation:

    • Myogenic Mechanism: adjusts afferent arteriole diameter based on blood pressure.

    • Tubuloglomerular Feedback: sensitive to ion concentrations in filtrate.

Neural and Hormonal Influences

  • Neural Regulation:

    • Sympathetic fibers cause afferent arteriole constriction during stress.

  • Hormonal Regulation:

    • Angiotensin II and ANP play roles in influencing GFR and blood flow.

Conclusion

  • Overview of the urinary system's function in fluid balance, nutrient reclamation, and waste excretion.

  • Understanding nephron structure and function is crucial for grasping kidney physiology.