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Intercostal muscles are a group of muscles that occupy the 11 intercostal spaces between the ribs. They are divided into three groups: external, internal, and innermost intercostal muscles. These muscles play a critical role in the movement of the rib cage and support the respiratory process by helping to expand and shrink the chest cavity. The external intercostals facilitate inhalation, while the internal and innermost intercostals aid in forced exhalation. Intercostal muscle strains can be painful and may require medical attention if breathing difficulties or persistent pain occur.
| Characteristics | Values |
|---|---|
| Definition | The intercostal muscles are a group of muscles intrinsic to the rib cage that occupy the 11 intercostal spaces. |
| Types | External, internal, and innermost intercostal muscles. |
| Function | The intercostal muscles aid in breathing by helping to expand and shrink the chest cavity. |
| Blood Supply | Anterior and posterior intercostal arteries, costocervical trunk, internal thoracic, and musculophrenic arteries. |
| Innervation | Intercostal nerves (the ventral rami of thoracic spinal nerves). |
| Vein Drainage | Intercostal veins. |
| Strain Treatment | Mild to moderate strains can be treated at home with rest, ice packs, and over-the-counter pain or anti-inflammatory medication. Severe cases may require emergency medical care, especially if breathing difficulties or signs of infection are present. |
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What You'll Learn
Intercostal muscle strain
Intercostal muscles occupy the 11 intercostal spaces between the ribs and help form and move the chest wall. They are divided into three groups: external, internal, and innermost intercostal muscles. These muscles are responsible for the mechanical aspect of breathing, helping to expand and shrink the chest cavity. The external intercostal muscles are the outermost layer and run from the back of the rib cage to the front, facilitating forced inspiration. The internal intercostal muscles are responsible for forced expiration. Lastly, the innermost intercostal muscles are the deepest layer and help compress the ribs and stabilise the rib cage.
An intercostal muscle strain is an injury to these muscles between the ribs. It is typically caused by overexertion, trauma, or repetitive torso twisting. Examples include lifting heavy objects, falling, a car accident, or participating in contact or high-thrust sports such as hockey, tennis, or golf. Poor posture can also lead to intercostal muscle strain. Symptoms include sharp pain, swelling, stiffness, tenderness, and difficulty breathing. Diagnosis involves a physical examination to check for limitations of movement and assess areas of tenderness. Imaging tests such as X-rays or MRIs may be ordered to rule out other possible causes of pain, such as a rib fracture.
Treatment for intercostal muscle strain depends on the severity of the injury. Mild cases may only require home treatment, such as applying an ice pack followed by heat therapy and resting for a few days. Pain medications such as acetaminophen or ibuprofen can help reduce swelling and pain. If breathing is painful, it is recommended to hold a pillow against the injured area. More severe cases may require physical therapy, consisting of various stretches and breathing exercises to strengthen the intercostal muscles. Surgery and an extended period of physical rehabilitation may be necessary for complete muscle tears.
To prevent intercostal muscle strain, it is important to stretch before and after physical activity, stay hydrated, and use proper form when lifting or performing overhead activities.
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Types of intercostal muscles
Intercostal muscles are a group of intrinsic rib cage muscles that occupy the 11 intercostal spaces. They are divided into three groups, going from superficial to deep: external, internal, and innermost intercostal muscles.
External Intercostal Muscles
The external intercostals, also known as intercostalis externus, are the most superficial intercostal muscles. They facilitate forced inspiration and aid in quiet inhalation. They originate on ribs 1–11 and have their insertion on ribs 2–12. The external intercostals are responsible for the elevation of the ribs and bending them more open, thus expanding the transverse dimensions of the thoracic cavity. The muscle fibres are directed downwards, forwards, and medially in the anterior part. The blood supply to the external intercostals comes from the anterior and posterior intercostal arteries.
Internal Intercostal Muscles
The internal intercostals, also known as intercostalis internus, form the middle layer of the intercostal musculature. They originate from the costal groove of one rib, course inferolaterally, and insert to the superior border of the immediate rib below. They aid in forced expiration, while quiet expiration is a passive process. The internal intercostal muscles are responsible for depressing the ribs during forced expiration, thus decreasing the transverse dimensions of the thoracic cavity. Their blood supply comes from the anterior and posterior intercostal arteries, as well as from the costocervical trunk, internal thoracic, and musculophrenic arteries.
Innermost Intercostal Muscles
The innermost intercostals, also known as intercostalis intimus, are the deepest intercostal muscles. They originate from the costal groove of one rib, posteriorly to the origin of the internal intercostals, and insert to the superior border of the immediate rib below. The innermost intercostal muscles follow the same vascularization and innervation pattern as the internal intercostals. Their blood supply comes from the anterior and posterior intercostal arteries, as well as the costocervical trunk.
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Function of intercostal muscles
The intercostal muscles are a group of intrinsic rib cage muscles that occupy the 11 intercostal spaces. They are divided into three groups, from superficial to deep: external, internal, and innermost intercostal muscles. All three groups of muscles support the rib cage and participate in the process of forced breathing.
The external intercostal muscles, or the most superficial intercostal muscles, aid in quiet and forced inhalation. They elevate the ribs and bend them open, thus expanding the transverse dimensions of the thoracic cavity. They originate on ribs 1–11 and have their insertion on ribs 2–12. The muscle fibres are directed downwards, forwards, and medially in the anterior part.
The internal intercostal muscles, forming the middle layer of the intercostal musculature, aid in forced expiration. They originate from the costal groove of one rib, course inferolaterally, and insert to the superior border of the immediate rib below. They pull the ribs inward and downward, forcing air out of the lungs.
The innermost intercostal muscles are the deepest intercostal muscles. They originate from the costal groove of one rib, posteriorly to the origin of the internal intercostals. They course inferomedially, inserting to the superior border of the immediate rib below. The function of the innermost intercostals is to assist in depressing the ribs during forced expiration.
Deficient intercostal muscles, caused by neuromuscular diseases, may lead to respiratory insufficiency. This is due to the loss of appropriate tension in the intercostal spaces, resulting in internal and external movements of the chest wall during thoracic pressure changes.
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Innervation of intercostal muscles
The intercostal muscles are the muscles that occupy the 11 intercostal spaces between the ribs. There are three groups of intercostal muscles: external, internal, and innermost. The external intercostal muscles aid in quiet and forced inhalation, while the internal and innermost intercostal muscles aid in forced expiration.
The innervation of the intercostal muscles is provided by the intercostal nerves, which are the anterior rami of the first 11 thoracic spinal nerves. The first thoracic nerve divides into a superior part, which joins the brachial plexus, and an inferior part, which becomes the first intercostal nerve. The first six intercostal nerves innervate the nearby intercostal muscles, the cutaneous territory on the side of the thoracic wall, and the thoracic pleura. They also send branches to the intercostal muscles before ending as terminal branches to innervate the skin near the midline of the chest.
The lower intercostal nerves leave their intercostal spaces anteriorly to innervate the anterior abdominal wall, muscles, and the overlying skin. They also send branches to the intercostal muscles, abdominal peritoneum, and skin before innervating these structures. Additionally, near their origin, the intercostal nerves send a posterior branch to the paraspinal muscles and the overlying skin.
The innermost intercostal muscles, being the deepest, arise from the inner margin of the costal groove of the rib above and insert into the superior border of the rib below. The vascularization and innervation of the innermost intercostal muscles follow the same pattern as the internal intercostal muscles. The blood supply for both groups comes from the anterior and posterior intercostal arteries, as well as the costocervical trunk.
The intercostal nerves play a crucial role in normal respiration by innervating the intercostal and abdominal muscles. They are essential for the effectiveness of coughing and sneezing. Lesions of these nerves can lead to abnormal movements of the chest wall during thoracic pressure changes and a decrease in peak expiratory flow.
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Blood supply to intercostal muscles
The intercostal muscles are a group of intrinsic rib cage muscles that occupy the 11 intercostal spaces. They are divided into three groups, from superficial to deep: external, internal, and innermost intercostal muscles. The external intercostal muscles are the most superficial of the intercostal muscles.
The blood supply to the intercostal muscles comes from the anterior and posterior intercostal arteries, as well as from the costocervical trunk, internal thoracic arteries, and musculophrenic arteries. The internal thoracic arteries were once referred to as the internal mammary arteries because they indirectly supply the breasts. They contribute to supplying the intercostal muscles, skin, and parietal pleura associated with the first six intercostal spaces.
The anterior and posterior intercostal arteries travel within the intercostal spaces, bordered by the lower edge of the rib above and the upper border of the rib below. Each of the upper nine intercostal spaces is supplied by a posterior and anterior intercostal artery, while the 10th and 11th intercostal spaces are supplied only by the posterior intercostal arteries. The internal thoracic artery supplies the anterior half of the upper six intercostal spaces, after which it branches into the musculophrenic artery and superior epigastric artery.
The superior intercostal artery (SIA), also known as the highest intercostal artery, is a division of the costocervical trunk, which originates from the subclavian artery. The SIA supplies blood to the upper intercostal spaces of the first and second ribs. The posterior intercostal arteries supply the chest wall, parietal pleura, and, through their dorsal branches, the skin and muscles of the back and spine.
The intercostal nerves originate from the ventral rami of corresponding spinal nerves, innervating the skin of the thoracic wall, the intercostal muscles, the rib periosteum, and the costal parietal pleura.
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Frequently asked questions
Intercostal muscles are the muscles that occupy the 11 intercostal spaces between the ribs. They help form and move the chest wall and are involved in the mechanical aspect of breathing by helping to expand and shrink the size of the chest cavity.
There are three groups of intercostal muscles: external, internal, and innermost intercostal muscles. The external intercostal muscles aid in quiet and forced inhalation, while the internal and innermost intercostals aid in forced expiration.
The innermost intercostal muscles are the deepest intercostal muscles. They originate from the costal groove of one rib and insert onto the superior border of the rib below. Their function is to assist in the depression of ribs during forced expiration.
Intercostal muscle strain can cause sharp rib pain and trouble taking deep breaths. Other symptoms include persistent chest or rib pain, difficulty breathing, and signs of infection such as fever, chills, or redness and swelling in the chest area.
