Body Cavities and Membranes

Overview

This lecture covers the major body cavities (dorsal and ventral), their subdivisions, and the membranes that protect and compartmentalize organs.

Major Body Cavities

• The body has two main cavities: the dorsal (back) and ventral (front) cavities.
• The dorsal cavity houses the central nervous system.
• The dorsal cavity is divided into the cranial cavity (brain) and vertebral cavity (spinal cord).
• The ventral cavity is larger and contains the visceral organs (guts).
• The ventral cavity is divided by the diaphragm into the thoracic cavity (chest) and abdominopelvic cavity.

Thoracic and Abdominopelvic Cavities

• The thoracic cavity sits above the diaphragm and contains the heart, lungs, trachea, and esophagus.
• The thoracic cavity has three parts: left pleural cavity (left lung), mediastinum (heart, esophagus, thymus, trachea), right pleural cavity (right lung).
• The heart is in the mediastinum and surrounded by the pericardial cavity.
• The abdominopelvic cavity is made up of the abdominal cavity (liver, stomach, pancreas, spleen, gallbladder, intestines, kidneys) and pelvic cavity (bladder, reproductive organs, distal large intestine).

Membranes of Body Cavities

• Major body cavities are lined with membranes for protection and compartmentalization.
• The dorsal cavity is lined by three meninges: dura mater, arachnoid, pia mater.
• Inflammation of the meninges is called meningitis.
• The ventral cavity contains serous membranes filled with serous fluid for lubrication.

Serous Membranes and Layers

• The pleura lines the pleural cavities (lungs), pericardium lines the pericardial cavity (heart), and peritoneum lines the peritoneal cavity (abdominopelvic region).
• Each serous membrane has a visceral layer (touches organs) and parietal layer (lines cavity wall).
• The space inside serous membranes (with fluid) is called a cavity, e.g., pleural cavity, pericardial cavity, peritoneal cavity.

Directional Terms for Peritoneum

• "Retroperitoneal" refers to organs behind the peritoneal space.
• "Intraperitoneal" refers to organs within the peritoneal space.
• "Subperitoneal" refers to organs below the peritoneal space.

Key Terms & Definitions

• Dorsal cavity — body cavity toward the back housing brain and spinal cord.
• Ventral cavity — body cavity toward the front containing visceral organs.
• Thoracic cavity — chest cavity above diaphragm.
• Abdominopelvic cavity — cavity below diaphragm, including abdominal and pelvic cavities.
• Meninges — three protective membranes (dura mater, arachnoid, pia mater) of the dorsal cavity.
• Serous membrane — thin membrane in ventral cavity producing serous fluid.
• Pleura — serous membrane around the lungs.
• Pericardium — serous membrane around the heart.
• Peritoneum — serous membrane in abdominal-pelvic cavity.
• Visceral layer — layer contacting organs.
• Parietal layer — layer lining the body cavity wall.
• Retroperitoneal — behind peritoneal cavity.
• Intraperitoneal — within peritoneal cavity.
• Subperitoneal — below peritoneal cavity.

Action Items / Next Steps

• Take the quiz linked in the lecture to test your knowledge of body cavities and membranes.
• Review related anatomy and physiology videos as suggested.