Anatomical Body Cavities and Subdivisions

Overview of Human Body Cavities

  • Definition and Primary Purpose: Internal fluid-filled or membrane-lined spaces within the human body that enclose, protect, cushion, and support internal organs (viscera).
  • Primary Structural Classification: Body cavities are organized into major compartments based on anatomical locations and structural boundaries.

Dorsal (Posterior) Cavity Structures

  • Cranial Cavity:
    • Anatomical Boundary: Formed by the bones of the cranium (skull).
    • Primary Content: Houses and protects the brain.
  • Vertebral Canal (Spinal Cavity):
    • Anatomical Boundary: Formed by the bony vertebrae of the vertebral column.
    • Primary Content: Encloses and protects the spinal cord.
    • Anatomical Continuity: Continuously connects with the cranial cavity at the base of the skull.

Ventral (Anterior) Cavity Structures

  • Thoracic Cavity:

    • Anatomical Boundaries: Superior portion of the ventral body cavity, surrounded by the rib cage, sternum, chest muscles, and thoracic vertebrae.
    • Pleural Cavities:
    • Quantity: Two distinct cavities (right and left pleural cavities).
    • Primary Content: Each pleural cavity individualizes and surrounds one lung.
    • Mediastinum:
    • Anatomical Location: Central tissue space and region situated in the midline between the two pleural cavities (between the lungs).
    • Extent: Extends from the sternum anteriorly to the vertebral column posteriorly, and from the superior thoracic aperture down to the diaphragm.
    • Pericardial Cavity:
    • Anatomical Location: Nestled within the central region of the mediastinum.
    • Primary Content: Encloses and cushions the heart.

  • Abdominopelvic Cavity:

    • Anatomical Boundaries: Inferior portion of the ventral body cavity located below the thoracic diaphragm.
    • Abdominal Cavity:
    • Anatomical Position: Superior region of the abdominopelvic cavity.
    • Primary Contents: Houses major digestive structures and associated organs, including the stomach, liver, gallbladder, spleen, pancreas, small intestine, and most of the large intestine.
    • Pelvic Cavity:
    • Anatomical Position: Inferior region of the abdominopelvic cavity, enclosed by the bones of the pelvis.
    • Primary Contents: Houses the urinary bladder, internal reproductive organs, and the terminal portion of the large intestine (rectum).

Major Internal Boundaries

  • Diaphragm:
    • Structural Description: A dome-shaped sheet of skeletal muscle.
    • Anatomical Function: Serves as the primary physical barrier separating the superior thoracic cavity from the inferior abdominopelvic cavity.