Body cavities are membrane-lined spaces containing internal organs: the body cavities are dorsal/posterior, cranial, vertebral, ventral/anterior, thoracic, and abdominopelvic.
The body cavities are organized as follows:
- Dorsal cavity: represents the smaller of two main body cavities (dorsal and ventral). It is located in the posterior (back) part of the body. The dorsal cavity primarily contains organs of the nervous system and is divided into two sections:
- Cranial cavity: the upper section, which houses the brain.
- Vertebral cavity or canal: the lower section, which houses the spinal cord. The brain and spinal cord are encased by the meninges, which are three protective membranes that encase the brain and spinal cord: the dura mater, the arachnoid mater, and the pia mater.
- Ventral cavity: The larger of the two main cavities is the anterior (front) part of the body and contains the remaining organs, called viscera. A serous membrane (thin membrane that secretes lubricating fluid to prevent friction between organs) lines the walls of the ventral cavity and covers the organs within the cavity. The ventral cavity is made up of the following cavities:
Thoracic cavity: The upper ventral, thoracic, or chest cavity contains the heart, lungs, trachea, esophagus, large blood vessels, and nerves. The thoracic cavity is encased by the ribs and the diaphragm, which separates the thoracic cavity from the abdominopelvic cavity. Within the thoracic cavity are three additional cavities:
- Pleural cavities: two cavities, each containing a lung. Pleura are two layers of serous membrane that protect and cushion the lungs. The visceral pleura is the membrane that covers and protects the surface of each lung, and the parietal pleura is the outer membrane that attaches the lungs to the walls of the thoracic cavity.
- Pericardialcavity: located within the mediastinum, which is the region between the lungs that extends from the sternum to the vertebral column. The pericardial cavity contains the heart. The pericardium is a tough membrane that surrounds and protects the heart.
- Abdominopelvic cavity: The lower part of the ventral cavity can be further divided into two portions:
- Abdominal cavity: contains most of the gastrointestinal tract as well as the kidneys and the adrenal glands. The abdominal cavity is bordered by the diaphragm above, the pelvic cavity below, and the body wall along the sides. Tissues and membranes, called the mesentery and peritoneum, surround the abdominal organs within the abdominal cavity. The mesentery is a tissue that attaches organs such as the stomach and the intestines to the abdominal wall. It contains blood vessels, nerves, and lymphatics of the intestines. The peritoneum is a serous membrane that lines walls of the abdominal cavity and covers most organs within the cavity. It is made up of the parietal (outer) layer and the visceral (inner) layer. The parietal peritoneum is a serous membrane that lines the abdominal wall. The visceral peritoneum is a serous membrane that covers the abdominal organs.
- Pelvic cavity: contains the urogenital (urinary and genital) system as well as the rectum. The pelvic cavity is bordered by the abdominal cavity above and the sacrum below, and it is encased by the pelvis
- Thoracic cavity: The upper ventral, thoracic, or chest cavity contains the heart, lungs, trachea, esophagus, large blood vessels, and nerves. The thoracic cavity is encased by the ribs and the diaphragm, which separates the thoracic cavity from the abdominopelvic cavity. Within the thoracic cavity are three additional cavities: