Diaphragm

The diaphragm is a dome-shaped musculofibrous septum which separates the thoracic cavity from the abdominal cavity, its convex upper surface forming the floor of the former, and its concave under surface the roof of the latter. Its peripheral part consists of muscular fibers which take origin from the circumference of the thoracic outlet and converge to be inserted into a central tendon.

The diaphragm may be divide into two symetrical parts, the right hemidiaphragm and the left hemidiaphragm.

The muscular fibers of each right and left part of diaphragm may be grouped according to their origins into three parts:

• The sternal part arises by two fleshy slips from the back of the xiphoid process

• The costal part arises from the inner surfaces of the cartilages and adjacent portions of the lower six ribs on either side, interdigitating with the Transversus abdominis

• The lumbar part arises from aponeurotic arches, named the arcuate ligaments (lumbocostal arches), and from the lumbar vertebrae by two pillars, the right crura and left crura. There are two arcuate ligaments (lumbocostal arches), a medial and a lateral, on either side of the diaphragm.

The central tendon, a strong aponeurotic structure, is located at the center of the diaphragm and serves as the insertion point for the muscle fibers. This tendon houses the foramen for the inferior vena cava. The diaphragm also contains openings for the esophagus (esophageal hiatus) and the aorta (aortic hiatus).

The diaphragm is innervated by the phrenic nerves, which originate from the cervical spinal cord (C3-C5). The blood supply to the diaphragm is primarily from the inferior phrenic arteries, with contributions from the superior phrenic, pericardiophrenic, and musculophrenic arteries.

Histologically, the diaphragm is composed of skeletal muscle fibers that exhibit transverse striations. These fibers are organized into fascicles that converge towards the central tendon, allowing for efficient contraction and relaxation during respiration