Overview
This lecture covers the major body cavities (dorsal and ventral), their subdivisions, the membranes that line them, and key terms used to describe these structures.
Major Body Cavities
- The human body has two main cavities: dorsal (toward the back) and ventral (toward the front).
- The dorsal cavity contains the central nervous system and is subdivided into the cranial cavity (brain) and vertebral cavity (spinal cord).
- The ventral cavity is larger and includes the thoracic cavity (chest) and abdominopelvic cavity (abdomen and pelvis), separated by the diaphragm.
Ventral Cavity Subdivisions
- The thoracic cavity contains the heart, lungs, trachea, and esophagus.
- It is further divided into the right pleural cavity (right lung), left pleural cavity (left lung), and mediastinum (middle region containing the heart, thymus, esophagus, and trachea).
- The heart is enclosed in the pericardial cavity within the mediastinum.
- The abdominopelvic cavity includes the abdominal cavity (digestive organs, kidneys, spleen) and pelvic cavity (bladder, reproductive organs, lower large intestine).
Body Membranes
- Cavities are lined with membranes that protect and compartmentalize organs.
- The dorsal cavity is lined by the meninges (dura mater, arachnoid, pia mater).
- The ventral cavity is lined by serous membranes (pleura, pericardium, peritoneum), which secrete serous fluid for lubrication.
Membrane Structure & Terminology
- Serous membranes have two layers: visceral (touches the organ) and parietal (lines the cavity wall).
- Pleura refers to the lung membrane; pericardium to the heart membrane; peritoneum to the abdominal cavity membrane.
- The fluid-filled space within each membrane is called a cavity (e.g., pleural cavity, pericardial cavity, peritoneal cavity).
- Organs behind the peritoneal space are retroperitoneal; inside are intraperitoneal; below are subperitoneal.
Key Terms & Definitions
- Dorsal cavity — body cavity toward the back, housing the central nervous system.
- Ventral cavity — front body cavity, containing thoracic and abdominopelvic cavities.
- Meninges — three protective membranes lining the dorsal cavity.
- Serous membrane — thin tissue lining the ventral cavity and producing fluid.
- Visceral layer — serous membrane layer touching the organ.
- Parietal layer — serous membrane layer lining the cavity wall.
- Pleura — membrane covering lungs.
- Pericardium — membrane enclosing the heart.
- Peritoneum — membrane lining the abdominal cavity.
- Retroperitoneal — behind the peritoneal membrane.
- Intraperitoneal — within the peritoneal space.
- Subperitoneal — below the peritoneal space.
Action Items / Next Steps
- Take the quiz linked to test your knowledge of body cavities and membranes.
- Review videos on directional terms and related anatomy topics for reinforcement.