The organs of the body lie mostly within two major cavities: the Ventral cavity and Dorsal cavity. The Dorsal cavity lies within the skull and vertebral column and has two subdivisions: the Cranial cavity and the Spinal cavity. As the names suggest, the cranial cavity hosts the brain and the spinal cord is found within the spinal cavity. These two cavities are lined by a special, continuous, membrane called the Meninges.

The ventral cavity also has two main subdivisions, the Thoracic cavity and the Abdominaopelvic cavity. These two cavities have an obvious division seperating them; The large, dome shaped Diaphragm muscle that sits below the lungs and above the stomach.

The Thoracic cavity is divided into right and left, lung containing sides by a medial partition called the Mediastinum, which contains the heart, trachea and esophogus. The lungs are seperated from each other and the heart into right and left Pleural cavities. Each cavity is lined by a membrane, the Parietal pleura, which is continuous and covers the lungs proper, forming the Visceral pleura. A similar situation exists with the heart, which resides within the Pericardial cavity, which is lined by the Parietal Pericardium, a membrane which is continuous with the Visceral Pericardium, covering the heart.

The abdominopelvic cavity is subdivided in it's own right, although this division is not obvious as it's division with the thoracic cavity. The upper Abdominal cavity is divided from the lower Pelvic cavity by an imaginary line from the pubis up and back to the top of the sacrum.

The abdominal cavity contains the stomach, intestines, liver, kidneys, spleen and pancreas. The pelvic cavity is a small space encased by the pelvic bones and contains the urinary bladder, the lower end of the colon, and the internal reproductive organs (primarily female). The abdominal cavity is lined by a membrane, the Parietal Perotineum, which is continuous with the organs of the abdominal cavity. This membrane is called the Visceral Perotineum. The space between these two is the Peritoneal cavity.