Question

what is the diaphragam in human respiration

Answer 1

Diaphragm, dome-shaped, muscular and membranous structure that separates the thoracic (chest) and abdominal cavities in mammals; it is the principal muscle of respiration.

The muscles of the diaphragm arise from the lower part of the sternum (breastbone), the lower six ribs, and the lumbar (loin) vertebrae of the spine and are attached to a central membranous tendon. Contraction of the diaphragm increases the internal height of the thoracic cavity, thus lowering its internal pressure and causing inspiration of air.

Relaxation of the diaphragm and the natural elasticity of lung tissue and the thoracic cage produce expiration. The diaphragm is also important in expulsive actions—e.g., coughing, sneezing, vomiting, crying, and expelling feces, urine, and, in parturition, the fetus. The diaphragm is pierced by many structures, notably the esophagus, aorta, and inferior vena cava, and is occasionally subject to herniation (rupture).
Small holes in the membranous portion of the diaphragm sometimes allow abnormal accumulations of fluid or air to move from the abdominal cavity (where pressure is positive during inspiration) into the pleural spaces of the chest (where pressure is negative during inspiration).

Spasmodic inspiratory movement of the diaphragm produces the characteristic sound known as hiccupping.

Answer 2

Diaphragm's Role in Breathing. When the diaphragm contracts and moves lower, the chest cavity enlarges, reducing the pressure inside the lungs. To equalize the pressure, air enters the lungs. When the diaphragm relaxes and moves back up, the elasticity of the lungs and chest wall pushes air out of the lungs.