Body Cavities and Membranes

Introduction

• Body cavity: Space or compartment in the body housing organs or structures.
• Two main body cavities:
  • Dorsal cavity
  • Ventral cavity

Dorsal Cavity

• Located in the back or posterior part of the body.
• Subdivisions:
  • Cranial cavity:
    • Superior part of the dorsal cavity.
    • Enclosed by the cranium (skull).
    • Houses the brain.
    • Contains cerebrospinal fluid (CSF) for protection and cushioning.
    • Lined by three-layer membrane: meninges (dura mater, arachnoid, pia mater).
  • Spinal cavity (vertebral cavity):
    • Inferior part of the dorsal cavity.
    • Enclosed by the vertebral column (spine).
    • Houses the spinal cord.
    • Contains CSF in the subarachnoid space.
    • Lined by meninges similar to the cranial cavity.

Ventral Cavity

• Located in the front or anterior part of the body.
• Subdivisions:
  • Thoracic cavity:
    • Superior portion of the ventral cavity.
    • Above the diaphragm.
    • Enclosed by rib cage, vertebral column, and sternum.
    • Main contents: heart, lungs, trachea, esophagus, great vessels.
    • Subdivisions:
      • Pleural cavities (right and left):
        • Surround the lungs.
        • Contains pleural fluid to lubricate the lungs.
        • Lined by double-layered serous membrane called pleura (visceral and parietal layers).
      • Mediastinum:
        • Middle portion of the thoracic cavity.
        • Contains heart, trachea, esophagus, great vessels, thymus gland.
        • Pericardial cavity within mediastinum:
          • Surrounds the heart.
          • Contains pericardial fluid.
          • Lined by pericardium (visceral and parietal layers).
  • Abdominopelvic cavity:
    • Inferior portion of the ventral cavity.
    • Below the diaphragm.
    • Subdivisions:
      • Abdominal cavity:
        • Middle part of the ventral cavity.
        • Enclosed by rib cage, abdominal muscles, vertebral column.
        • Main contents: liver, stomach, pancreas, spleen, kidneys, intestines.
        • Lined by peritoneum (visceral and parietal layers).
        • Contains peritoneal fluid.
      • Pelvic cavity:
        • Inferior portion.
        • Enclosed by pelvis and pelvic floor muscles.
        • Houses urinary bladder, reproductive organs, pelvic colon, and rectum.
        • Lined by peritoneum.

Summary

• Dorsal cavity: Houses central nervous system (brain and spinal cord).
• Ventral cavity: Includes thoracic and abdominopelvic cavities, containing main thoracic and abdominal organs.

Membranes and Fluids

• Meninges: Line the cranial and spinal cavities (dura mater, arachnoid mater, pia mater).
• Pleura: Surround the lungs in the thoracic cavity.
• Pericardium: Surrounds the heart in the pericardial cavity.
• Peritoneum: Lines the abdominal and pelvic cavities.
• Fluid in spaces: CSF in dorsal cavities, pleural fluid in pleural cavities, pericardial fluid in pericardial cavity, peritoneal fluid in peritoneal cavity.

These notes encapsulate the key points from the lecture on body cavities and membranes, serving as a useful study guide.