11-2D

Kidney Anatomy

  • Renal Structure
    • Pelvis: The cavity in the kidney where urine collects before entering the ureter.
    • Ureter: Tube that carries urine from the kidney to the urinary bladder.
    • Urinary Bladder: Sac-like organ that stores urine until it is excreted.

Development of Urinary Organs

  • Embryonic Development:
    • Week 5 to Week 8:
    • Week 5: Developing digestive tract, Allantois, Urogenital ridge.
    • Week 6: Formation of metanephros (kidney), ureteric bud, and continuation of the mesonephric duct.
    • Week 7: Development of urogenital sinus leading to the formation of the urinary bladder and urethra.
    • Week 8: Formation complete with the establishment of the gonads and anus.

Organs of the Urinary System

  • Key Components:
    • Kidney: Main organ for filtration.
    • Ureter: Conducts urine to the bladder.
    • Urinary Bladder: Functions as a storage reservoir.
    • Urethra: Enables urine to exit the body.
    • Associated Structures:
    • Hepatic Veins and Inferior Vena Cava: Major veins adjacent to the urinary organs.
    • Adrenal Gland: Located above each kidney, part of the endocrine system.

Positioning of the Kidneys

  • Abdominal Location:
    • Kidneys positioned abutting the posterior abdominal wall.
    • Peritoneum: Lining of the abdominal cavity.
    • Renal Fascia: Protective layer surrounding the kidneys.

Internal Anatomy of the Kidney

  • Structural Features:
    • Renal Hilum: Entry and exit point for blood vessels, nerves, and ureter.
    • Renal Cortex and Medulla: Distinct outer and inner regions of the kidney.
    • Renal Pelvis, Calyces: Collect urine from the pyramids and funnel it into the ureter.

Blood Vessels of the Kidney

  • Vascular Anatomy:
    • Renal Arteries and Veins: Major vessels supplying blood to and from the kidneys.
    • Nephron-associated Blood Vessels: Includes afferent and efferent arterioles.
    • Pathway of Blood Flow: Follow from the aorta to renal artery, through interlobar, arcuate, and cortical radiate arteries.

Nephron Structure and Function

  • Components of the Nephron:
    • Renal Corpuscle: Includes Bowman's capsule and glomerulus for filtration.
    • Renal Tubules: Proximal and distal convoluted tubules, nephron loop.
    • Collecting Ducts: Final segment where urine is collected.

Filtration in the Nephron

  • Filtration Membrane Structure:
    • Podocytes: Specialized cells in the glomerular capsule.
    • Fenestrations: Small pores allowing selective filtration of blood plasma.

Histology of the Nephron

  • Tissue Types:
    • Proximal Convoluted Tubule: Lined with microvilli for increased absorption surface.
    • Distal Convoluted Tubule: Clearer lumens due to less surface area for absorption.
    • Collecting Ducts and Vasa Recta: Significant for concentration of urine.

Ureter Structure

  • Microscopic Anatomy:
    • Mucosa: Interior lining of the ureter.
    • Muscularis: Muscle layers responsible for peristalsis in urine transport.

Abdominal Aorta and Venous Drainage

  • Major Branches:
    • Renal Arteries: Supply blood to the kidneys.
    • Tributaries of Inferior Vena Cava: Drain blood from kidneys back to the heart.

Fetal Circulation

  • Key Features:
    • Foramen Ovale: Shunts blood from right to left atrium during fetal development.
    • Ductus Arteriosus: Connects pulmonary trunk to the aorta, diverting blood in fetuses.
    • Postnatal Changes: Closure of fetal shunts (foramen ovale and ductus arteriosus) occurs after birth.

Portal Circulation

  • Hepatic Portal System:
    • Function: Transfers nutrient-rich blood from the gastrointestinal tract to the liver.
    • Structures: Includes portal vein formed by splenic vein, superior mesenteric vein, and inferior mesenteric vein.
    • Clinical Relevance: Conditions such as portal hypertension can arise from blockages within the hepatic portal system.

Microscopic Structure of Liver and Capillaries

  • Liver Microscopy:
    • Composed of hepatocytes arranged into plates.
    • Sinusoids: Specialized capillary structures with a fenestrated lining to facilitate exchange of substances.
  • Capillary Types:
    • Continuous, Fenestrated, and Sinusoidal Capillaries: Varying degrees of permeability based on location and function.

Notes and Considerations

  • Future Considerations for Study:
    • Comparison of tubular structures (e.g., nephron and esophagus) may be relevant for deeper understanding of urinary functions.
    • Continuity with physiological practices in laboratory studies to be integrated into assessment.