Introduction:
The diaphragm muscle is located in the thoracic (chest) cavity and is known as the thoracic diaphragm. It is the major respiratory muscle that is located below the lungs and the heart. This muscle separates the thorax from the abdomen. The normal functioning of the diaphragm muscle is essential for the breathing process to take place. This muscle helps in inhalation and exhalation.
What Is Diaphragm?
The diaphragm is a major respiratory muscle that functions during respiration. The diaphragm develops from several embryonic sources, including the septum transversum, pleuro-peritoneal membrane, mesentery of the esophagus, and mesoderm of the body wall. It receives blood supply from the musculophrenic branch of the internal thoracic artery, the superior phrenic branch of the aorta, the inferior phrenic artery, the lower five intercostal arteries, and the subcostal artery. The diaphragm is innervated by the right and left phrenic nerves and the lower six intercostal nerves.
The diaphragm is a respiratory muscle that contracts and flattens during inhalation, and when it contracts, the thoracic cavity enlarges and reduces the intrathoracic pressure to allow the filling of the inspired air in the alveoli (sac-like structures) of the lungs. During exhalation, the diaphragm relaxes, and the air is pushed out of the lungs.
The diaphragm has a convex upper surface that forms the floor of the thoracic cavity and a concave surface that forms the roof of the abdominal cavity. The inferior vena cava, descending aorta, phrenic and vagus surface, and the esophagus pass through the diaphragm muscle between the abdomen and the thorax. This muscle is asymmetric with the left side, which is slightly inferior to the right side, because the liver is present on the right side. The left side of the diaphragm may also be inferiorly located due to the push by the heart.
What Is the Role of Diaphragm in Respiration?
Breathing or respiration is a complex process that relies on the coordinated actions of the respiratory muscles and the control center in the brain. The lungs facilitate gaseous exchange between inspired air and the circulatory system of the body. The respiratory cycle is composed of inspiration and expiration. During each inspiration (inhalation), the diaphragm and the external intercostal muscles contract and allow the expansion of the thoracic cavity. This causes the intrapleural pressure to decrease, and so the alveolar pressure decreases. This fall in pressure forces the lungs to expand and allows the air to move in. Contraction and relaxation of the external intercostal muscles and the diaphragm are responsible for the pressure changes that result in the act of inspiration.
During expiration (exhalation), the diaphragm relaxes and does not play a role. The internal intercostal muscles and the abdominal muscles are essential for expiration. These muscles contract and compress the abdominal organs and push them up into the diaphragm. This raises the pleural pressure and alveolar pressure, which pushes the air out of the lungs.
Why Is Diaphragm Significant for Respiration?
The diaphragm is the major muscle essential for inspiration. The diaphragm contracts and moves down during inspiration into the abdominal cavity and appears flat. It pulls the central tendon down to increase the vertical diameter of the thoracic cavity to allow the inspired air to move in. During respiration, the diaphragm muscle relaxes and becomes dome-shaped due to the contraction of the abdominal muscles and the internal intercostal muscles, which push the abdominal organs up into the diaphragm, resulting in the exhalation of air.
What Does Diaphragmatic Breathing Mean?
Diaphragmatic breathing is a technique that helps to use the diaphragm in the right way to increase the efficiency of the lungs. Diaphragmatic breathing helps strengthen the diaphragm, decreases oxygen demand, decreases the workload by decreasing the heart rate, and also uses less energy to breathe. During diaphragmatic breathing, the diaphragm muscle is used consciously to take deep breaths. During normal breathing, the lungs are not used efficiently. Diaphragmatic breathing allows a person to use the lungs at 100 percent capacity, thereby increasing efficiency.
What Are the Other Functions of the Diaphragm?
Besides respiration, the diaphragm muscle plays several other roles. It functions as a barrier between the abdominal cavity and thorax and prevents herniation (abnormal protrusion from an enclosed cavity) of abdominal organs into the thoracic cavity. The diaphragm muscle also plays a role in hiccups. Hiccups are due to irritation of the diaphragm muscle, resulting in sudden contractions that are uncomfortable and may interfere with breathing if they are persistent. Other important functions of the diaphragm include the following:
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Abdominal Straining - The contraction of the diaphragm muscle assists in the contraction of the anterior abdominal wall muscles and raises intra-abdominal pressure. This helps in normal processes like vomiting, defecation (passing stools), micturition (voiding of urine), and parturition (the act of giving birth). The diaphragm muscle also prevents acid reflux by putting pressure on the esophagus.
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Weightlifting - During weightlifting, when a person takes a deep breath and holds it, the diaphragm will assist the anterior abdominal wall muscles to raise the intra-abdominal pressure. This is known as the Valsalva maneuver. This maneuver is used to determine whether the murmurs are right-sided or left-sided and to augment the heart murmurs.
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Thoracoabdominal Pump - During inhalation, the diaphragm moves down to increase the intrathoracic pressure, which improves intra-abdominal pressure. This causes the compression of the blood in the inferior vena cava and forces it to move upwards into the right atrium (right upper chamber) of the heart and helps fill the heart. When abdominal lymphatic vessels are also compressed, their movement within the thoracic duct is driven by the negative intrathoracic pressure. Further, the backflow of the lymph in the thoracic duct is prevented by the valves in the thoracic duct.
Conclusion:
The diaphragm is the major respiratory muscle that plays a significant role in respiration. Several conditions, injuries, and diseases can damage this muscle and disrupt its function. The diaphragm is one of the crucial muscles of the body due to its role in breathing. Like any other muscle in the body, the diaphragm can be strengthened with exercises like diaphragmatic breathing or abdominal breathing. This helps in strengthening the diaphragm, decreasing oxygen demand, decreasing the workload by decreasing the heart rate, and also decreasing the energy required to breathe. In addition, stress and blood pressure can be reduced.
