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The diaphragm is a thin, dome-shaped muscle that sits below the lungs and heart, and is responsible for helping us breathe. It is the primary muscle of respiration, and its movement during inhalation and exhalation facilitates the entry and exit of air into the lungs. The diaphragm is also believed to be made up of two separate muscles, the crural and costal diaphragm, which act in synchrony during respiration.
| Characteristics | Values |
|---|---|
| Location | Below the lungs, at the inferior-most aspect of the ribcage |
| Shape | Upward curved, C-shaped, dome-shaped |
| Function | Helps you breathe, separates the chest cavity from the abdomen |
| Composition | Muscle and fibrous tissue |
| Peripheral attachments | Lumbar vertebrae, arcuate ligaments, costal cartilages of ribs 7-10, xiphoid process of the sternum |
| Central tendon | Forms the crest of the dome |
| Regions | Costal, crural |
| Innervation | Phrenic nerve, intercostal and subcostal nerves |
| Blood supply | Inferior phrenic arteries, superior phrenic arteries, pericardiacophrenic artery, musculophrenic artery, internal thoracic arteries |
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What You'll Learn
The diaphragm is a muscle that helps you breathe
The diaphragm is a dome-shaped muscle that sits under the lungs, separating the chest cavity from the abdomen. It is the primary muscle of respiration, helping us breathe by undergoing rhythmic contractions and relaxations that alter the volume of the thoracic cavity and the lungs, producing inspiration and expiration.
During inspiration, the diaphragm contracts and flattens, increasing the vertical diameter of the thoracic cavity, which in turn produces lung expansion, and air is drawn in. During expiration, the diaphragm passively relaxes and returns to its original dome shape, reducing the volume of the thoracic cavity. The diaphragm is also important in expulsive actions such as coughing, sneezing, vomiting, crying, and expelling feces, urine, and, in parturition, the fetus.
The diaphragm is composed of two distinct muscle regions: the costal diaphragm, which serves as the driver in the work of breathing, and the crural diaphragm, which serves as an "anchor," attaching the muscle to the lower ribs and lumbar vertebrae. The diaphragm is pierced by many structures, including the esophagus, aorta, and inferior vena cava, and is occasionally subject to herniation (rupture).
Several conditions, diseases, and injuries can damage the diaphragm, causing symptoms such as trouble breathing, chest pain, and acid reflux. Diaphragmatic breathing exercises can help strengthen the diaphragm, improve its efficiency, and reduce stress.
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It separates the chest cavity from the abdomen
The diaphragm is a thin, upward curved, C-shaped structure of muscle and fibrous tissue. It is the primary muscle of respiration, helping you breathe by contracting and flattening to expand the lungs, and passively relaxing to return to its original dome shape to push air out of the lungs.
The diaphragm separates the chest cavity from the abdomen, acting as the floor of the thoracic cavity and the roof of the abdominal cavity. It has three peripheral attachments: lumbar vertebrae and arcuate ligaments, costal cartilages of ribs 7-10, and the xiphoid process of the sternum. The muscle fibres from these attachments converge in a central tendon, which forms the crest of the dome.
The diaphragm is innervated by the phrenic nerve, with separate branches innervating the crural and costal regions. The crural diaphragm serves as an "anchor", attaching the muscle to the lower ribs and lumbar vertebrae, while the costal diaphragm serves as the driver in the work of breathing.
The diaphragm also plays a role in preventing gastric contents from refluxing into the oesophagus. This is achieved by some fibres from the right crus surrounding the oesophageal opening, acting as a physiological sphincter.
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The diaphragm is innervated by the phrenic nerve
The diaphragm is a double-domed sheet of skeletal muscle located at the inferior-most aspect of the rib cage. It separates the thoracic cavity from the abdominal cavity and acts as their floor and roof, respectively. The diaphragm is the primary muscle of respiration. It contracts and relaxes rhythmically, altering the volume of the thoracic cavity and the lungs, thus producing inspiration and expiration.
The diaphragm receives motor innervation from the phrenic nerve. The phrenic nerve is the only nerve in the nervous system that provides motor (movement) function to the diaphragm. It originates from the anterior rami of C3 through C5 and traverses the neck, heart, and lungs to reach the diaphragm. The left phrenic nerve innervates the left hemidiaphragm, and the right phrenic nerve innervates the right hemidiaphragm. Each phrenic nerve is formed in the neck within the cervical plexus and contains fibres from spinal roots C3-C5.
The phrenic nerve plays a critical role in the respiratory system by aiding breathing. It sends signals that cause the diaphragm to expand and contract. These movements allow the lungs to inhale and exhale air. The nerve also provides touch and pain sensory information to the diaphragm, diaphragmatic pleura, mediastinal pleura, pericardium, and peritoneum.
Damage to the phrenic nerve can lead to diaphragm weakness or paralysis, affecting the lungs' ability to exchange air. Diaphragmatic paralysis can be caused by various factors, including mechanical trauma, compression due to a tumour, myopathies such as myasthenia gravis, and neuropathies like diabetic neuropathy. Depending on the location of the nerve damage, paralysis may affect one or both sides of the diaphragm. People with severe bilateral diaphragm paralysis may require mechanical ventilation to breathe.
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It has peripheral and central attachments
The diaphragm is a sheet of skeletal muscle that separates the thoracic cavity, containing the heart and lungs, from the abdominal cavity. It is located at the inferior-most aspect of the rib cage, acting as the floor of the thoracic cavity and the roof of the abdominal cavity.
The diaphragm has peripheral and central attachments. The peripheral attachments include the lumbar vertebrae and the arcuate ligaments. The diaphragm is attached anteriorly to the xiphoid process and costal margin, laterally to the 11th and 12th ribs, and posteriorly to the lumbar vertebrae. The arcuate ligaments consist of the medial, lateral, and median arcuate ligaments, with the latter arising from the fibrous parts of the right and left crura. The right crus arises from L1-L3 and their intervertebral discs, while the left crus arises from L1-L2 and their intervertebral discs. Some fibres from the right crus surround the oesophageal opening, acting as a physiological sphincter to prevent reflux of gastric contents into the oesophagus.
The diaphragm also has three muscular parts: sternal, costal, and lumbar. These parts have their own origins but all insert into the central tendon of the diaphragm. The central tendon is a thin but strong aponeurosis near the centre of the vault formed by the muscle, closer to the front than to the back of the thorax. The central tendon receives sensory afferents from the phrenic nerve, while the peripheral portions of the diaphragm send sensory afferents via the intercostal and subcostal nerves.
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Conditions, injuries and diseases can affect how the diaphragm works
The diaphragm is a large, dome-shaped muscle located below the lungs. It contracts and flattens during inhalation, creating a vacuum that pulls air into the lungs. During exhalation, it relaxes and returns to its dome shape, forcing air out of the lungs. As the diaphragm sits near the fifth and sixth intercostal space and incompletely separates the thoracic and abdominal cavities, it is susceptible to both thoracic and abdominal trauma.
Conditions, injuries, and diseases can affect how the diaphragm works. For example, a diaphragmatic hernia is a birth defect that creates an opening in the diaphragm, allowing the passage of abdominal contents into the chest cavity. Blunt or penetrating traumas can also cause diaphragm injuries, which are often undiagnosed due to the challenge of detecting small tears. Delayed diagnosis of a diaphragmatic rupture may require surgery to address herniation and extensive adhesions.
Paralysis of the diaphragm can result from various factors, including lung or lymph cancer compressing the phrenic nerve, surgical or birth trauma, injury to the spinal cord or phrenic nerve, and neuromuscular disorders such as ALS and MS. Disorders of the diaphragm can arise from a range of causes, including congenital conditions and major trauma.
To diagnose diaphragm disorders, a physical examination and discussion of symptoms are typically conducted first. This may be followed by imaging techniques such as X-rays, CT scans, and MRIs to identify blockages, fluids, or other abnormalities. Pulmonary function tests, spirometry, peak flow meter measurements, and blood tests can also help evaluate diaphragm function and respiratory health.
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Frequently asked questions
The diaphragm is a thin, upward curved, c-shaped structure of muscle and fibrous tissue that separates the thoracic cavity from the abdomen. It is the primary muscle of respiration, helping you breathe by contracting and flattening to pull air into the lungs, and relaxing and returning to its dome shape to push air out of the lungs.
The diaphragm is the major muscle of respiration and plays a critical role in helping you breathe. It also helps to stop gastric contents from refluxing into the oesophagus.
The diaphragm is composed of two distinct muscle regions: the costal, which serves as the driver in the work of breathing, and the crural diaphragm, which acts as an "anchor" by attaching the muscle to the lower ribs and lumbar vertebrae.
