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The external intercostal muscles are a set of 11 muscles located between each rib, starting from the first rib and extending down to the 11th rib. They are the most superficial set of muscles and are found externally to the internal and innermost intercostals. The external intercostals play a significant role in respiration by elevating the ribs and expanding the chest cavity, allowing the lungs to fill with air during inhalation. These muscles receive nerve signals from the intercostal nerves, which are branches of the spinal cord, and have an extensive vascular supply from three major arteries.
| Characteristics | Values |
|---|---|
| Number | 11 pairs |
| Location | Between each rib, starting at the first rib and extending down to the 11th rib |
| Function | Elevate the rib cage, assist the lungs in expanding to take in air |
| Innervation | Intercostal nerves (T1-T11) |
| Blood supply | Three major arteries |
| Attachment | Originates at the lower border of each rib, inserting onto the superior border of the rib below |
| Layer | Superficial |
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What You'll Learn
External intercostal muscles are located between the ribs
The external intercostal muscles are a set of muscles located between the ribs. They are the most superficial or surface-level muscles of the three groups of intercostal muscles, with the internal and innermost intercostals lying deep to them. There are 11 pairs of external intercostal muscles, extending from the first rib to the 11th rib. These muscles are small but relatively powerful, and they play an important role in respiration.
The external intercostals attach along the shafts of the ribs and extend obliquely from the lower border of one rib to the upper border of the adjacent rib below. They originate from the inferior border of one rib, course inferomedially, and insert into the superior border of the rib below. This positioning allows the external intercostals to lift the ribs upward and spread them apart, making space for the lungs to expand with air. The internal intercostal muscles relax while the external intercostals contract, causing the expansion of the chest cavity and facilitating inhalation.
The external intercostal muscles are thicker than the internal intercostals, and their fibres are directed obliquely downward and laterally on the back of the thorax, and downward, forward, and medially on the front. The external intercostals receive innervation from the intercostal nerves of corresponding intercostal spaces, which are the anterior rami of thoracic spinal nerves. They have an extensive vascular supply, receiving blood from three major arteries: the anterior and posterior intercostal arteries, and the musculophrenic artery.
The external intercostal muscles work in conjunction with other muscles in the upper body to facilitate rib cage adjustments. For example, the serratus posterior and pectoralis minor muscles assist with raising the upper ribs, while the sternocleidomastoid muscle, which originates from the jaw and crosses over the neck, moves the breastbone upward. The health and functioning of the spine are also dependent on the appropriate contraction of the external intercostal muscles, as each rib wraps around the body and ends near the spine.
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They are involved in the process of breathing
The external intercostal muscles are a set of muscles located between adjacent ribs, attaching along the shafts of the ribs and extending from the lower border of one rib to the upper border of the adjacent rib below. They are the most superficial set of muscles that occupy the 11 intercostal spaces. Their name is derived from their spatial relationship with other intercostal muscles, as they are found superficially to the internal and innermost intercostals.
The external intercostals are involved in the process of breathing. They receive innervation from intercostal nerves of corresponding intercostal spaces, which are the anterior rami of thoracic spinal nerves. They facilitate forced inspiration, while the internal and innermost intercostals aid forced expiration. During inhalation, the internal intercostal muscles relax while the external muscles contract, causing the expansion of the chest cavity and allowing air to enter the lungs. This is known as forced breathing, where the external intercostal muscles elevate the ribs, increasing the thoracic volume.
The motions of the external intercostals assist the lungs by raising the ribs and expanding the chest cavity, creating space for the lungs to expand with air. This process is crucial for respiration, and the health and functioning of the spine depend on the appropriate contraction of these muscles. The external intercostals are relatively small but powerful muscles, and their health is vital to overall respiratory health.
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They are the most superficial of the intercostal muscles
The external intercostal muscles are the most superficial set of muscles that occupy the 11 intercostal spaces. They are located superficially to the internal intercostal muscles, and their name is derived from their spatial relationship with other intercostal muscles.
The external intercostal muscles are small but powerful muscles, and they play a crucial role in respiration. They are involved in the motion of the ribs, specifically in elevating the ribs and expanding the chest cavity, allowing the lungs to fill with air during inhalation. These muscles work in unison with the internal intercostal muscles. During inhalation, the external intercostal muscles contract, while the internal intercostal muscles relax, causing the chest cavity to expand and facilitating the influx of air into the lungs.
The external intercostal muscles are located between the ribs, extending from the lower border of one rib to the upper border of the adjacent rib below. They are thicker than the internal intercostals, and their fibres are directed obliquely downward and laterally on the back of the thorax, and downward, forward, and medially on the front. The external intercostal muscles receive their nerve supply from the intercostal nerves, which are the anterior rami of the thoracic spinal nerves.
The health and functioning of the spine are dependent on the appropriate contraction of the external intercostal muscles. While these muscles are small, their contraction is essential for rib cage adjustments and plays a significant role in the respiratory system.
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They work in conjunction with the internal and innermost intercostal muscles
The external intercostal muscles are a set of muscles located between adjacent ribs, attaching along the shafts of the ribs and extending from the lower border of one rib to the upper border of the adjacent rib below. They are the most superficial of the three groups of intercostal muscles, which include the internal and innermost intercostal muscles.
The external intercostal muscles work in conjunction with the internal and innermost intercostal muscles to support the rib cage and facilitate respiration. During inhalation, the external intercostal muscles contract, elevating the ribs and expanding the chest cavity to create room for the lungs to fill with air. At the same time, the internal intercostal muscles relax, allowing for the expansion of the chest cavity.
The internal intercostal muscles lie deep to the external intercostals and extend from the rib above to the one below, but in the opposite direction (inferoposteriorly). They are continuous with the internal oblique muscle of the abdominal wall. The innermost intercostal muscles are the deepest intercostal muscles and are similar in structure to the internal intercostals. They are separated from the internal intercostals by the intercostal neurovascular bundle and are found in the most lateral portion of the intercostal spaces.
Together, the external, internal, and innermost intercostal muscles maintain the stability of the thoracic cage during various movements involving the trunk. They also play a role in forced breathing, with the external intercostals facilitating forced inspiration and the internal and innermost intercostals aiding forced expiration. The internal intercostals depress the ribs and decrease thoracic volume during forced expiration, while the external intercostals elevate the ribs and increase thoracic volume during forced inspiration.
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They receive innervation from intercostal nerves
The external intercostal muscles are a group of 11 intrinsic rib cage muscles that occupy the 11 intercostal spaces on both sides. They are the most superficial set of muscles, located superficially to the internal intercostal muscles. The external intercostals are small but relatively powerful muscles that play a significant role in respiration. During inhalation, they contract and elevate the ribs, expanding the chest cavity and facilitating the influx of air into the lungs.
The external intercostal muscles receive innervation from the intercostal nerves of corresponding intercostal spaces, which are the anterior rami of thoracic spinal nerves (T1-T11). These intercostal nerves are responsible for providing nerve signals to the external intercostals, coordinating their contractions and relaxations during the respiratory cycle. The nerves arise from the spinal cord and carry signals that trigger the contraction of the external intercostals, enabling the elevation of the rib cage and assisting the lungs in expanding to take in air.
The external intercostal muscles have an extensive vascular supply and are supplied by three major arteries: the anterior and posterior intercostal arteries, and the internal thoracic artery. The anterior intercostal arteries supply the upper six intercostal spaces, while the lower three are supplied by the musculophrenic artery, a branch of the internal thoracic artery. The posterior intercostal arteries arise from two sources: the supreme intercostal artery, a branch of the costocervical trunk, and the thoracic aorta.
The innervation provided by the intercostal nerves is crucial for the function of the external intercostal muscles in respiration. During forced inspiration, the external intercostals contract and elevate the ribs, increasing thoracic volume. This movement is coordinated by the signals from the intercostal nerves, ensuring the proper timing and coordination of the respiratory muscles.
Any damage or disease affecting the intercostal nerves can have significant consequences for the function of the external intercostal muscles. For example, neuromuscular diseases or trauma can lead to deficiencies in the intercostal muscles, impacting their ability to maintain the appropriate tension of the intercostal spaces. This, in turn, can result in respiratory insufficiency and impaired breathing. Thus, the health and functioning of the external intercostal muscles are closely linked to the proper innervation provided by the intercostal nerves.
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Frequently asked questions
The external intercostal muscles are the most superficial set of muscles that occupy the 11 intercostal spaces between the ribs. They are small but powerful muscles that elevate the ribs during forced inhalation, thus assisting the lungs in expanding to take in air.
The external intercostal muscles work in unison with the internal intercostal muscles during inhalation. While the internal intercostal muscles relax, the external intercostal muscles contract, causing the expansion of the chest cavity and allowing air to enter the lungs.
Strained external intercostal muscles can be caused by too much stress or pressure, or direct injury to the muscles due to assault or respiratory conditions. Symptoms of a strained external intercostal muscle include sharp pain in the upper back and ribs, which worsens with coughing, sneezing, and deep breathing.
