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The external intercostal muscles are a group of intrinsic rib cage muscles that occupy the 11 intercostal spaces. They are the most superficial set of muscles and are located superficially to the internal intercostal muscles. 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. In this response, we will explore the innervation of the external intercostal muscles, their function, and their relationship to other muscle groups.
| Characteristics | Values |
|---|---|
| Innervation | Intercostal nerves of corresponding intercostal spaces, which are the anterior rami of thoracic spinal nerves T1-T11 |
| Function | Accessory respiratory muscles that facilitate forced inspiration |
| Location | Superficial to the internal intercostal muscles |
| Structure | 11 pairs of muscles |
| Blood supply | Muscular branches of the anterior and posterior intercostal arteries |
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What You'll Learn
- External intercostals facilitate forced inspiration
- External intercostal muscles are innervated by the intercostal nerves
- The external intercostals are the most superficial intercostal muscles
- External intercostal muscles are accessory respiratory muscles
- Internal and innermost intercostals aid forced expiration
External intercostals facilitate forced inspiration
The external intercostal muscles are a group of intrinsic rib cage muscles that occupy the 11 intercostal spaces. They are the most superficial intercostal muscles and are functionally classified as accessory respiratory muscles.
The external intercostal muscles facilitate forced inspiration by elevating the ribs during forced inhalation. They originate from the inferior border of one rib and insert into the superior border of the rib below. This action of the external intercostals helps to expand the thoracic cavity, aiding in inhalation or inspiration.
The diaphragm is the main inspiratory muscle, and during inspiration, it contracts and moves inferiorly, increasing the vertical diameter of the thoracic cavity and facilitating lung expansion, which draws air in. The external intercostal muscles work alongside the diaphragm as primary inspiratory muscles, and their function in elevating the ribs during forced inhalation contributes to expanding the thoracic cavity, thus facilitating inspiration.
The external intercostal muscles receive their nerve supply from the intercostal nerves of the corresponding intercostal spaces, specifically the anterior rami of spinal nerves T1-T11. Their blood supply comes from the anterior and posterior intercostal arteries, as well as contributions from other arteries such as the internal thoracic and musculophrenic arteries.
In summary, the external intercostal muscles facilitate forced inspiration by elevating the ribs during forced inhalation, which leads to an expansion of the thoracic cavity and aids in the process of inhalation or inspiration.
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External intercostal muscles are innervated by the intercostal nerves
The external intercostal muscles are the most superficial set of muscles that occupy the 11 intercostal spaces. They are found superficially to the internal and innermost intercostals. The external intercostal muscles are innervated by the intercostal nerves of corresponding intercostal spaces. These nerves are the anterior rami of thoracic spinal nerves T1-T11.
The external intercostal muscles consist of 11 pairs of muscles. Every external intercostal originates from the sharp inferior costal border of one rib. The fibres of each muscle course inferomedially and insert along the outer lip of the superior border of the rib below. The external intercostal muscles are separated from the internal intercostal muscles by a thin fascia.
The external intercostal muscles are accessory respiratory muscles. They elevate the ribs during forced inhalation and facilitate inspiration. The internal and innermost intercostals aid forced expiration. All three groups of muscles support the rib cage and participate in the process of forced breathing.
The internal intercostal muscles are the middle layer of the intercostal musculature. They originate from the costal groove of one rib and insert to the superior border of the rib below. They are innervated in the same way as the external intercostals, by the intercostal nerves. The innermost intercostal muscles are the deepest of the three groups of intercostal muscles.
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The external intercostals are the most superficial intercostal muscles
The external intercostal muscles are the most superficial of the intercostal muscles, which occupy the 11 intercostal spaces. They are also known as the intercostalis externus. The external intercostal muscles are located superficially to the internal intercostal muscles, separated by a thin fascia.
The external intercostal muscles consist of 11 pairs of muscles. They originate from the inferior border of one rib and insert along the superior border of the rib below. The muscle fibres are directed downwards, forwards, and medially in the anterior part. The external intercostal muscles are innervated by the intercostal nerves of corresponding intercostal spaces, which are the anterior rami of thoracic spinal nerves T1-T11.
The function of the external intercostal muscles is to aid in quiet and forced inhalation. They elevate the ribs and bend them more open, thus expanding the transverse dimensions of the thoracic cavity. This facilitates forced inspiration and makes the thoracic cage more rigid and convenient for the diaphragm to act upon.
The external intercostal muscles have an extensive vascular supply. They are supplied by the muscular branches of the anterior and posterior intercostal arteries, with the first two posterior intercostal arteries arising from the supreme intercostal artery, a branch of the costocervical trunk.
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External intercostal muscles are accessory respiratory muscles
The external intercostal muscles are the most superficial set of muscles that occupy the 11 intercostal spaces. They are one of the three groups of intercostal muscles, the others being the internal and innermost intercostal muscles. The external intercostal muscles are located superficially to the internal intercostal muscles, separated from them by a thin fascia.
The external intercostal muscles are accessory respiratory muscles. They aid in quiet and forced inhalation by elevating 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. They originate on ribs 1–11 and have their insertion on ribs 2–12.
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. They have an extensive vascular supply and are supplied by the muscular branches of the anterior and posterior intercostal arteries. The anterior intercostal arteries supplying the muscles of the upper 6 intercostal spaces arise from the internal thoracic artery directly, while the lower 3 arise from its branch, the musculophrenic artery.
The internal intercostal muscles, on the other hand, aid in forced expiration by depressing the ribs, thus shrinking the diameter of the thoracic cavity and pushing the air out of the lungs. They originate on ribs 2–12 and have their insertions on ribs 1–11. Their fibres pass anterior and superior from the upper margin of the rib and costal cartilage to the lower margin of the rib below. The internal intercostal muscles are innervated in the same way as the external intercostals, by the intercostal nerves.
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Internal and innermost intercostals aid forced expiration
The intercostal muscles are a group of intrinsic rib cage muscles that occupy the 11 intercostal spaces. They are divided into three groups: external, internal, and innermost intercostal muscles. The external intercostal muscles are the most superficial set of muscles, followed by the internal intercostal muscles, and then the innermost intercostal muscles, which are the deepest.
The internal and innermost intercostals aid forced expiration by depressing the ribs, thus reducing the volume of the thoracic cavity and pushing air out of the lungs. This is often referred to as the expiratory phase of respiratory activity. The internal intercostal muscles originate from the costal groove of one rib and insert into the superior border of the rib below. They receive their innervation from the intercostal nerves of corresponding intercostal spaces, which are the anterior rami of thoracic spinal nerves.
The innermost intercostal muscles arise from the inner margin of the costal groove of the rib above and insert into the superior border of the rib below. Their vascularization and innervation follow the same pattern as the internal intercostals, with blood supply coming from the anterior and posterior intercostal arteries, costocervical trunk, internal thoracic, and musculophrenic arteries.
The external intercostal muscles, on the other hand, aid in forced inspiration, which is the opposite function of the internal and innermost intercostals. They originate from the inferior border of one rib and insert into the superior border of the rib below. These muscles are innervated by the intercostal nerves as well, specifically the anterior rami of spinal nerves T1-T11.
In summary, the internal and innermost intercostal muscles work together to aid forced expiration by depressing the ribs and reducing the volume of the thoracic cavity, while the external intercostal muscles facilitate forced inspiration by elevating the ribs. All three groups of intercostal muscles support the rib cage and are involved in the mechanical aspect of breathing by helping to expand and shrink the chest cavity.
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Frequently asked questions
The external intercostal muscles are the most superficial set of muscles that occupy the 11 intercostal spaces. They are accessory respiratory muscles that aid in quiet and forced inhalation by elevating the ribs and bending them more open, thus expanding the transverse dimensions of the thoracic cavity.
The external intercostal muscles are innervated by the intercostal nerves of corresponding intercostal spaces, which are the anterior rami of thoracic spinal nerves T1-T11.
The external intercostal muscles facilitate forced inspiration. They are responsible for the elevation of the ribs, thus assisting the forced inspirium.
