Anatomy and Physiology: Body Cavities and Membranes

Major Body Cavities

• Purpose: Protect and compartmentalize organs.
• Two Main Cavities:
  • Ventral Cavity:
    • Located at the front (anterior) of the body.
    • Contains visceral organs (guts).
    • Subdivisions:
      • Thoracic Cavity:
        • Contains heart, lungs, trachea, esophagus.
        • Divided into:
          • Left Pleural Cavity: Houses left lung.
          • Mediastinum: Houses heart, esophagus, thymus gland, trachea.
            • Pericardial Cavity: Surrounds the heart.
          • Right Pleural Cavity: Houses right lung.
      • Abdominopelvic Cavity (divided by diaphragm):
        • Abdominal Cavity: Liver, stomach, pancreas, spleen, gallbladder, intestines, kidneys.
        • Pelvic Cavity: Bladder, reproductive organs, distal portions of the large intestine.
  • Dorsal Cavity:
    • Located at the back (posterior) of the body.
    • Houses the central nervous system.
    • Subdivisions:
      • Cranial Cavity: Houses the brain.
      • Vertebral Cavity: Houses the spinal cord.

Body Membranes

• Membranes: Thin sheets of tissue lining cavities, covering and protecting organs.
• Dorsal Cavity Membranes (Meninges):
  • Dura Mater
  • Arachnoid
  • Pia Mater
  • Condition: Meningitis is the inflammation of the meninges (symptom - neck stiffness).
• Ventral Cavity Membranes (Serous Membranes):
  • Pleura: Lines pleural cavity, covers each lung.
  • Pericardium: Lines pericardial cavity, covers the heart.
  • Peritoneum: Lines the peritoneal cavity in the abdominopelvic region.
  • Serous Fluid: Provides lubrication and movement.

Directional Terms for Membrane Layers

• Visceral Layer:
  • Contacts the organ (viscera).
• Parietal Layer:
  • Lines the cavity wall.
• Example Usage:
  • Visceral Pleura: Touches the lung.
  • Parietal Pleura: Lines the thoracic cavity wall.
• Misunderstanding Caution:
  • Don't confuse membrane lining with the cavity it contains.
  • Pleura vs. Pleural Cavity
  • Pericardium vs. Pericardial Cavity
  • Peritoneum vs. Peritoneal Cavity

Additional Terms

• Retroperitoneal: Organs behind the peritoneal space.
• Intraperitoneal: Organs within the peritoneal space.
• Subperitoneal: Organs below the peritoneal space.

Recap

• Two Major Cavities:
  • Dorsal Cavity: Cranial and vertebral cavities.
  • Ventral Cavity: Includes thoracic and abdominopelvic cavities.
• Membranes: Different membranes line these cavities and assist in protecting and cushioning organs.
• Directionality and Naming Conventions: Helps specify membrane locations and differentiate between cavity and lining.

Conclusion

• Understanding of body cavities and membranes helps in grasping the organizational structure that protects and compartmentalizes the organs.
• Suggested to watch supplementary anatomy videos and quizzes for better understanding.