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The intercostal muscles are a group of intrinsic rib cage muscles that occupy the 11 intercostal spaces between the ribs. They are divided into three groups: external, internal, and innermost intercostal muscles. These muscles are responsible for supporting the rib cage and aiding in the process of breathing by helping to expand and contract the chest cavity. Intercostal muscle strain can occur due to trauma, overexertion, or repetitive torso twisting and can result in pain, difficulty breathing, and inflammation.
| Characteristics | Values |
|---|---|
| Definition | Muscles that present within the rib cage |
| Location | Between the ribs |
| Number of Intercostal Spaces | 11 |
| Number of Muscle Groups | 3 |
| Muscle Groups | External, Internal, Innermost |
| Function | Support the rib cage and participate in the process of forced breathing |
| Blood Supply | Anterior and posterior intercostal arteries, costocervical trunk, internal thoracic and musculophrenic arteries |
| Nerve Supply | Intercostal nerves |
| Vein Supply | Intercostal veins |
| Injury Causes | Weakened muscles, overexertion, direct trauma, repetitive torso twisting |
| Symptoms of Strain | Worsening pain, difficulty breathing, tenderness, inflammation, swelling |
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What You'll Learn
Intercostal muscle strain
Intercostal muscles are the muscles that lie within the rib cage. They consist of three layers of muscles: external, internal, and innermost. These layers combine to fill the space between the ribs. The outermost layer of external intercostal muscles lies directly under the skin and expands the chest wall during inhalation. The intermediate layer of internal intercostal muscles helps collapse the lungs during exhalation. The innermost intercostal muscles cross more than one intercostal space and assist the internal and external intercostals in their function.
An intercostal muscle strain is an injury to the intercostal muscles between the ribs. It is almost always the result of overexertion or injury. Intercostal muscle strains don't usually happen during daily life activities. They occur when the muscles are weakened, or as a result of direct trauma such as a blow to the rib cage, a fall, or a car accident. Contact sports such as hockey, football, or activities such as yoga or dancing can also cause intercostal muscle strain. Twisting the torso while lifting or engaging in certain sports such as tennis or golf can also cause this injury. Overuse or repetition of movements can also cause intercostal muscle strain. Examples include lifting heavy objects or participating in sports such as golf or tennis. Poor posture can also lead to muscle strain when standing or sitting for an extended period.
The symptoms of an intercostal muscle strain include sharp, direct pain, stiffness, and mobility difficulties. There may be swelling or tenderness in the area where the muscle is strained. The pain can worsen within days or weeks if the intercostal muscles are still under tension from repetitive, gradual stress. This type of strain is common after sports such as baseball. Intercostal muscle strain can also cause difficulty breathing, with the breathing pattern being affected due to pain, resulting in shallow breathing to avoid pain. This may lead to less blood oxygenation and, in the long term, complications such as pneumonia. Pain from intercostal muscle strain may increase with coughing, sneezing, or breathing deeply.
The diagnosis of intercostal muscle strain 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 injuries, such as a fractured rib. Intercostal muscle strain is treated with rest, ice packs, and pain medication. Deep breathing exercises may be recommended to improve shallow breathing. In severe cases, surgery and physical rehabilitation may be required.
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Intercostal muscle anatomy
The intercostal muscles are intrinsic rib cage muscles that occupy the 11 intercostal spaces between the ribs. They are divided into three groups, from superficial to deep: external, internal, and innermost intercostal muscles. These muscles support the rib cage and participate in the process of forced breathing.
The external intercostal muscles, or intercostalis externus, are the most superficial intercostal muscles. They aid in quiet and forced inhalation by facilitating the expansion of the chest cavity. They originate on ribs 1–11 and insert on ribs 2–12, with muscle fibres directed downwards, forwards, and medially. The external intercostals are responsible for elevating and bending the ribs, increasing the transverse dimensions of the thoracic cavity.
The internal intercostal muscles, or intercostalis internus, aid in forced expiration. They originate on ribs 2–12 and extend from the front of the ribs, wrapping around to the back. Their function is to depress the ribs during forced exhalation.
The innermost intercostal muscles, or musculi intercostales intimi, are the deepest intercostal muscles. They originate from the costal groove of one rib and insert into the superior border of the rib below. These muscles assist the internal intercostals in depressing the ribs during forced expiration.
The external and internal intercostal muscles are innervated by the intercostal nerves (the ventral rami of thoracic spinal nerves) and supplied by the intercostal arteries, with drainage provided by the intercostal veins. The innermost intercostals follow the same vascularization and innervation patterns as the internal intercostals.
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Intercostal muscle function
The intercostal muscles are a group of intrinsic rib cage muscles that occupy the 11 intercostal spaces between the ribs. 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 are accessory respiratory muscles that participate in the process of forced breathing.
The external intercostal muscles, or intercostalis externus, are the outermost layer of intercostal muscles. They lie directly under the skin and originate from the lower border of the rib above, running obliquely and inserting into the upper border of the rib below. During inhalation, they facilitate quiet and forced inspiration by raising the ribs and bending them to expand the chest cavity.
The internal intercostal muscles, or intercostalis internus, are the intermediate layer of intercostal muscles. They originate from the costal groove near the inferior border of the rib above and insert into the upper border of the rib below. During forced expiration, they aid in depressing the ribs to collapse the lungs and shrink the chest cavity.
The innermost intercostal muscles are the deepest intercostal muscles. They also assist in depressing the ribs during forced expiration. These muscles cross more than one intercostal space and help the internal and external intercostals in their function.
The scalene muscles, which move the chest wall and are involved in inhalation, are also considered intercostal muscles, although they are not one of the three principal layers. The blood supply to the intercostal muscles comes from various arteries, including the anterior and posterior intercostal arteries, the costocervical trunk, the internal thoracic arteries, and the musculophrenic arteries.
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Intercostal muscle innervation
The intercostal muscles are a group of muscles that run between the ribs and help form and move the chest wall. They are responsible for changing the volume of the thoracic cavity during respiration, aiding in both inhalation and exhalation. There are three layers of intercostal muscles: external, internal, and innermost.
The external intercostal muscles are the outermost layer and lie directly under the skin. They originate from the lower border of the rib above and insert into the upper border of the rib below, with their muscle fibres directed downwards, forwards, and medially. These muscles are responsible for expanding the chest wall during inhalation by elevating the ribs and bending them to open up the thoracic cavity.
The internal intercostal muscles are the middle layer of the intercostal muscle group. There are 11 pairs of internal intercostal muscles, occupying the 11 intercostal spaces between the ribs. They originate from the inferior margin of costal cartilage and inner lip of the costal groove and insert into the superior border of the immediate inferior rib. These muscles, along with the innermost intercostals, enable forced expiration by depressing the ribs and shrinking the thoracic cavity.
The innermost intercostal muscles are the deepest layer of the intercostal muscles. They cross more than one intercostal space and assist the external and internal intercostals in their functions.
In terms of innervation, there is some disagreement about the exact source of intercostal muscle innervation. Some sources suggest that the intercostal muscles are primarily innervated by the intercostal nerves, which are the anterior rami of the thoracic spinal nerves. The intercostal nerves provide sensory and motor information to the muscles and skin of the thoracic wall. However, other sources suggest that the intercostal muscles may also receive innervation from the external or internal thoracic nerves, or a combination of these sources.
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Intercostal muscle injury causes
Intercostal muscles are the muscles within the rib cage that help expand and contract the chest during breathing. They consist of three layers of muscles: external, internal, and innermost. Strains of these muscles can result in pain and discomfort with breathing, moving, or coughing.
Intercostal muscle injuries are uncommon in daily life and usually happen when the muscles are weakened, overexerted, or experience direct trauma. This can include falling, a car accident, or a blow from contact sports such as hockey. Twisting the torso during activities like dancing, yoga, or sports can also cause intercostal muscle strain if the ribs are moved beyond their normal range. Overhead activities or lifting objects above the shoulder can also place undue stress on the intercostal muscles.
The severity of an intercostal muscle strain can vary from mild to severe. Mild strains may cause discomfort but do not significantly impact daily activities. They usually heal within a few days with home treatments such as ice packs, heat therapy, rest, and over-the-counter pain medications. Moderate strains may take 3-7 weeks to heal, while severe strains involving a complete tear of the muscles can take longer and may require surgery and physical rehabilitation.
In addition to the causes mentioned above, intercostal muscle strains can also be caused by overuse or overstretching of the muscle. This is common in high-thrust sports that involve repeated use of the arm, shoulder, and upper back, putting stress on the intercostal muscles. Contact sports with direct and sudden force to the upper body can also lead to intercostal muscle strain. Symptoms include sudden severe pain in the upper back or rib cage, muscle tension and stiffness, and a gradual worsening of pain within days or weeks.
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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.
There are three groups of intercostal muscles: external, internal, and innermost intercostal muscles.
The external intercostal muscles aid in quiet and forced inhalation. They are responsible for the elevation of the ribs and help to expand the chest cavity.
The internal intercostal muscles aid in forced expiration. They originate from the costal groove near the inferior border of the rib above and help to collapse the lung during exhalation.
The innermost intercostal muscles assist in depressing the ribs during forced expiration. They originate from the costal groove of one rib and insert into the superior border of the rib below.
