Diaphragm

The diaphragm is a large muscle separating the thoracic and abdominal cavities and has an important function in normal respiration. The bulk of the diaphragm is innervated by the phrenic nerve but the peripheral part gets its nerve supply from the adjoining intercostal nerves. As the intra-abdominal pressure is greater than that in the chest, a paralytic diaphragm will appear to be higher than a normal diaphragm and does not move appropriately with respiration. In the condition known as eventration of the diaphragm there is deficient muscle and the fibrous part is stretched with poor but normal movement. Large diaphragmatic hernias associated with agenesis of the relevant lung and malrotation of the bowel are a neonatal emergency (see Chapter 21). Smaller hernias characteristically occur anteriorly (Morgagni hernia) and posteriorly (Bochdalek hernia) and are less of a problem unless bowel becomes trapped in them (Fig. 18.5).

The chest is built like a bellows with 12 ribs on each side; the upper ones are articulated at the costotransverse angle

Morgagni

Morgagni

Bochdalek

Congenital

Hiatal diaphragmatic hernia

Figure 18.5. Sites if hernia. IVC: inferior vena cava.

Bochdalek

Congenital

Hiatal diaphragmatic hernia

Figure 18.4. Mediastinum showing divisions.

Figure 18.5. Sites if hernia. IVC: inferior vena cava.

and expand the chest as they rise and fall in a bucket-handle motion. This along with the rise and fall of the diaphragm allows air to be taken in and blown out from the lungs. The lungs have a natural elastic recoil which lessens with age. The normal intrathoracic pressure varies between -5 and

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