Body Cavities and Membranes

Body Cavities and Membranes

• The body cavities are lined with thin sheets of tissue called membranes, which cover and protect the various organs of the body.
• The dorsal body cavity is lined with three layers of protective membranes called the meninges, which are: the dura mater, the arachnoid membrane, and the pia mater.
• The ventral body cavity contains various serous membranes, which are filled with fluid that allows for lubrication and slight movement of the organs.
• Important serous membranes include: the pleura, the pericardium, and the peritoneum.
• Serous membranes line the trunk cavities and cover the organs of these cavities.

Serous Membranes and Organs

• The visceral serous membrane represents the inner balloon wall in contact with the fist (organ), and the outer part of the balloon wall represents the parietal wall serous membrane.
• The cavity or space between the visceral and parietal serous membranes is normally filled with a thin, lubricating film of serous fluid produced by the membranes.
• The serous fluid and smooth serous membranes function to reduce friction as an organ rubs against another organ or against the body wall.

Thoracic Cavity

• The thoracic cavity contains three serous membrane-lined cavities: a pericardial cavity and two pleural cavities.
• The pericardial cavity surrounds the heart, and is covered by the visceral pericardium and contained within a connective tissue sac lined with the parietal pericardium.
• The pericardial cavity contains pericardial fluid, located between the visceral and parietal pericardia.
• Each lung is surrounded by a pleural cavity, covered by visceral pleura, and the inner surface of the thoracic wall is lined by the parietal pleura.
• The pleural cavity is located between the visceral and parietal pleurae and contains pleural fluid.

Abdominopelvic Cavity

• The abdominopelvic cavity contains a serous membrane-lined cavity called the peritoneal cavity.
• Many of the organs of the abdominopelvic cavity are covered by visceral peritoneum, and the wall of the abdominopelvic cavity is lined with parietal peritoneum.
• The peritoneal cavity is located between the visceral and parietal peritoneum and contains peritoneal fluid.

Major Trunk Cavities

• The trunk contains three large cavities: the thoracic cavity, the abdominal cavity, and the pelvic cavity.
• The thoracic cavity is surrounded by the rib cage and is separated from the abdominal cavity by the muscular diaphragm.
• The abdominal cavity is bounded primarily by the abdominal muscles and contains the stomach, intestines, liver, spleen, pancreas, and kidneys.
• The pelvic cavity is a small space enclosed by the bones of the pelvis and contains the urinary bladder, part of the large intestine, and the internal reproductive organs.

Homeostasis

• Homeostasis is the process by which a stable (or steady) internal environment is maintained in the body, so that cellular metabolic functions can proceed at maximum efficiency.