According to the McGraw-Hill Applied Science Resource Center, some examples of body parts that begin with the letter "D" are the diaphragm, duodenum and dermis. The diaphragm is a thin, muscular connective tissue that divides the abdomen from the chest and contributes to breathing. The duodenum is the first part of the small intestine. The dermis is the inner layer of skin that is under the epidermis.
The diaphragm is at the bottom of the chest cavity and connects to the spine. It borders the ribs and sternum and contains holes which allow the esophagus and parts of the heart to pass through the chest and abdomen. Inhaling causes the diaphragm to contract and lay flat, and the rib cage rises to expand the lungs so that air can flow in. Exhaling causes the rib cage to lower, and the diaphragm relaxes into a dome-like shape. The stratum basale is the layer that separates the epidermis from the dermis. The dermis nourishes the epidermis, because this outer layer does not have its own blood system. The duodenum is a C-shaped structure that passes near the kidney and the upper portion of the lumbar vertebrae. It connects to the second portion of the small intestine, the jejunum.