Anatomy & Physiology

Anatomy & Physiology Study Guide section. A cut parallel to the midsagittal line is a parasagittal section . Unless otherwise noted, all anatomical diagrams that present cross-sectional views of the body are oriented with the subject positioned supine and the observer positioned at the feet looking towards the head.

Body Cavities Body cavities are internal chambers that house vital organs and other body parts. These cavities have two essential functions: (1) protect delicate organs and (2) permit changes in the size and shape of internal organs. As a result, the lungs and many other organs can expand and contract within their body cavities without a disruption in the activities of adjacent organs. The ventral body cavity appears early in embryological development. It contains organs of the respiratory, cardiovascular, digestive, urinary, and reproductive systems. As these internal organs develop, their relative positions change, and the ventral body cavity is gradually subdivided. The diaphragm , a flat muscular sheet, divides the ventral body cavity. This division creates a thoracic cavity superiorly, and an inferior abdominopelvic cavity that is enclosed by the abdominal wall and the musculoskeletal frame of the pelvis. Many of the organs in the thoracic and abdominopelvic cavities change size and shape as they perform their functions. For example, the lungs inflate and deflate with each breath, and the stomach expands when full and shrinks when empty. These organs, called viscera, are surrounded by moist internal spaces that permit expansion and prevent friction. A thin liner, known as a serous membrane , covers the walls of these internal cavities and the surfaces of the enclosed viscera. A watery fluid

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