Muscles of respiration

Muscles of respiration are a group of muscles that contribute to the process of breathing by aiding in the expansion and contraction of the thoracic cavity. These muscles are essential for the respiratory system to function effectively, allowing for the exchange of oxygen and carbon dioxide in the lungs.

Primary Muscles of Respiration

The primary muscles involved in respiration include the diaphragm and the intercostal muscles.

Diaphragm

The diaphragm is a dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. It is the most important muscle for inhalation. When the diaphragm contracts, it flattens, increasing the volume of the thoracic cavity and allowing air to be drawn into the lungs.

Intercostal Muscles

The intercostal muscles are located between the ribs and are divided into three groups: the external intercostal muscles, the internal intercostal muscles, and the innermost intercostal muscles.

• External Intercostal Muscles: These muscles aid in inhalation by elevating the ribs, which increases the volume of the thoracic cavity.
• Internal Intercostal Muscles: These muscles assist in exhalation by depressing the ribs, which decreases the volume of the thoracic cavity.
• Innermost Intercostal Muscles: These muscles function similarly to the internal intercostal muscles and assist in forced exhalation.

Accessory Muscles of Respiration

Accessory muscles are used during forced breathing or when the primary muscles are not sufficient. These include the sternocleidomastoid, scalene muscles, pectoralis minor, and abdominal muscles.

Sternocleidomastoid

The sternocleidomastoid muscle helps elevate the sternum during forced inhalation, increasing the volume of the thoracic cavity.

Scalene Muscles

The scalene muscles elevate the first and second ribs, aiding in the expansion of the thoracic cavity during deep inhalation.

Pectoralis Minor

The pectoralis minor muscle assists in elevating the ribs during forced inhalation.

Abdominal Muscles

The abdominal muscles, including the rectus abdominis, external oblique, internal oblique, and transversus abdominis, play a role in forced exhalation by compressing the abdominal contents and pushing the diaphragm upward.

Function in Respiration

The coordinated action of these muscles allows for the efficient movement of air into and out of the lungs. During inhalation, the primary muscles contract to increase the volume of the thoracic cavity, creating a negative pressure that draws air into the lungs. During exhalation, the muscles relax, and the elastic recoil of the lungs and thoracic cavity expels air.

Clinical Significance

Dysfunction or weakness in the muscles of respiration can lead to respiratory disorders and difficulty in breathing. Conditions such as chronic obstructive pulmonary disease (COPD), asthma, and neuromuscular diseases can affect the function of these muscles.

See Also

• Respiratory system
• Breathing
• Diaphragm
• Intercostal muscles
• Forced breathing

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