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The subcostal muscles are a group of muscles in the thorax that assist with respiration by pulling the ribs down and towards the central axis of the thorax during forced exhalation. They are thin muscles found on the inner surface of the posterior thoracic wall, stretching across two or three intercostal spaces. The subcostal muscles originate from the inner surface of one rib and are inserted into the inner surface of the second or third rib below. Their fibres run in the same direction as the innermost intercostal muscles, with which they may sometimes fuse.
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What You'll Learn
- Subcostal muscles are intrinsic thoracic muscles
- They are located on the inner surface of the posterior thoracic wall
- They assist in respiration by pulling the ribs during forced exhalation
- The muscles originate from the internal surfaces of the seventh to tenth ribs
- They are supplied by the arteries of the trunk wall
Subcostal muscles are intrinsic thoracic muscles
The subcostal muscles are a group of muscles of the thorax that are found laterally to the thoracic vertebrae. They are thin muscles found on the inner surface of the posterior thoracic wall, filling the intercostal spaces and bridging two or three intercostal spaces. The subcostal muscles are the most developed in the lower part of the thoracic cage and are sometimes fused with the innermost intercostals in their origin.
The subcostal muscles originate from the internal surfaces of the seventh to tenth ribs, in the areas that are located adjacent to the angles of these ribs. They can also originate from the inner surface of one rib near its posterior angle. Their fibres descend inferomedially in the same fashion as those of the innermost and internal intercostals. Each subcostal muscle inserts to the inner surface of the second or third rib below its origin.
The subcostal muscles are innervated by the intercostal nerves (anterior rami of thoracic spinal nerves). They are supplied by the arteries of the trunk wall, namely the muscular branches of the posterior intercostal and musculophrenic arteries. They are drained by the posterior intercostal veins that empty into the superior vena cava via the azygos and the brachiocephalic veins.
The subcostal muscles are part of the accessory respiratory musculature, and their function is to depress the ribs during forced exhalation. This action enables them to pull the ribs towards the central axis of the thorax, which then compresses the lungs, pushing air out of them.
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They are located on the inner surface of the posterior thoracic wall
The subcostal muscles, also known as the subcostales, are a group of muscles located in the thoracic region of the body, specifically on the inner surface of the posterior thoracic wall. This muscle group is situated deep within the thorax, beneath the ribs, and plays a crucial role in respiratory function and thoracic stability.
Being located on the inner surface of the posterior thoracic wall means that the subcostal muscles lie posterior to the sternum and anterior to the vertebral column, with their fibers running in an oblique direction. This placement allows them to provide structural support to the thoracic cavity and facilitate respiratory movements.
Specifically, the subcostal muscles originate from the inner surfaces of the ribs, primarily the first nine pairs, and insert onto the vertebral column. Their attachments to the ribs can be identified by feeling along the inferior borders of the ribs, where the subcostal muscles form a distinct ridge-like structure. This structure can be felt deep to the intercostal muscles, which lie more superficially.
To identify the subcostal muscles, it is important to understand their relationship with the surrounding anatomical structures. These muscles lie deep within the thoracic cavity, providing assistance during quiet respiration and forced expiration. They work in conjunction with other respiratory muscles to ensure proper breathing function. Additionally, the subcostal muscles help to raise the first nine pairs of ribs, contributing to the overall stability and protection of the organs within the thorax.
In summary, the subcostal muscles are located on the inner surface of the posterior thoracic wall, deep to the ribs and intercostal muscles. They play an important role in respiration and thoracic stability, working synergistically with other muscles involved in breathing. By understanding their attachments, actions, and anatomical relationships, one can appreciate the significance of the subcostal muscles in maintaining respiratory function and protecting the vital organs within the thoracic cavity.
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They assist in respiration by pulling the ribs during forced exhalation
The subcostal muscles are thin, narrow muscles found on the inner surface of the posterior thoracic wall. They bridge two or three intercostal spaces, and their fibres descend inferomedially. The subcostal muscles are accessory respiratory muscles, and their function is to assist in respiration by pulling the ribs during forced exhalation.
During forced exhalation, the subcostal muscles depress the ribs at their costovertebral joints, pulling them towards the central axis of the thorax. This action compresses the lungs, pushing air out of them. The subcostal muscles originate from the inner surface of one rib near its posterior angle and insert into the inner surface of the second or third rib below. They are located laterally to the thoracic vertebrae, with their posterior surfaces lying over the inner surface of the ribs and the internal intercostal membranes.
The subcostal muscles are innervated by the intercostal nerves, specifically the anterior rami of the thoracic spinal nerves. They receive their arterial supply from the arteries of the trunk wall, namely the muscular branches of the posterior intercostal and musculophrenic arteries. The subcostal muscles are drained by the posterior intercostal veins, which empty into the superior vena cava.
The subcostal muscles are considered secondary respiratory muscles due to their role in depressing the ribs during forced exhalation. They are a part of the intercostal muscle group and are located in the posterior chest, close to the rib angles. The word "subcostal" refers to their location slightly below the ribs.
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The muscles originate from the internal surfaces of the seventh to tenth ribs
The subcostal muscles are intrinsic thoracic muscles that play a crucial role in respiration. They are thin muscles located on the inner surface of the posterior thoracic wall, stretching across two or three intercostal spaces. Laterally, they are in contact with the innermost intercostal muscles, and their posterior surfaces lie over the inner surface of the ribs.
The subcostal muscles originate specifically from the internal surfaces of the seventh to tenth ribs, near their angles. There can be variations between individuals regarding the origin sites of these muscles. The fibres of the subcostal muscles travel inferomedially and insert onto the second or third rib inferior to their origin sites. For instance, the fibres originating from the ninth rib will insert onto the second or third rib below, i.e., the tenth or eleventh rib.
The subcostal muscles are a group of muscles of the thorax, consisting of short, individual skeletal muscles found in the lower half of the posterior thoracic wall. They are usually well-developed only in the lower part of the thorax. Their function is to depress the ribs during forced exhalation, pulling them towards the central axis of the thorax, which compresses the lungs and facilitates exhalation.
The subcostal muscles work in conjunction with other muscle groups, including the intercostal muscles, serratus posterior, levatores costarum, and transversus thoracis muscles, to comprise the intrinsic musculature of the chest wall. This collective system assists in respiration and provides support to the intercostal spaces and thoracic cage.
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They are supplied by the arteries of the trunk wall
The subcostal muscles are thin muscles found on the inner surface of the posterior thoracic wall. They are part of the intrinsic musculature of the chest wall, along with the intercostal, serratus posterior, levatores costarum, and transversus thoracis muscles. The subcostal muscles play a crucial role in respiration by pulling the ribs inferiorly during forced exhalation and supporting the intercostal spaces and thoracic cage.
These muscles are supplied by the arteries of the trunk wall, specifically the muscular branches of the posterior intercostal and musculophrenic arteries. The posterior intercostal arteries are responsible for supplying the back muscles, vertebral column, spinal cord segments, and the overlying skin in the related area. They are found within the intercostal space and play a vital role in providing oxygenated blood to the muscles and surrounding structures.
The musculophrenic artery, being more laterally placed, supplies several intercostal spaces and pierces the diaphragm. It anastomoses with the deep circumflex iliac artery, ensuring adequate blood supply to the muscles and surrounding tissues. The subcostal muscles also receive their blood supply from the posterior intercostal arteries, which are direct branches of the thoracic aorta.
The blood supply provided by these arteries is essential for the functioning of the subcostal muscles. They ensure that the muscles receive the necessary oxygen and nutrients for their contraction and relaxation during respiration. The arteries of the trunk wall play a crucial role in maintaining the overall health and functionality of the subcostal muscles, allowing them to effectively assist in the respiratory process.
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Frequently asked questions
The subcostal muscles are located on the inner surface of the posterior thoracic wall, found laterally to the thoracic vertebrae.
The subcostal muscles assist in respiration by pulling the ribs towards the central axis of the thorax during forced exhalation, thus compressing the lungs and pushing air out of them.
The subcostal muscles originate from the internal surfaces of the ribs and insert onto the inner surface of the second or third rib below their origin sites (i.e., the ninth to twelfth ribs).
The fibres of the subcostal muscles travel inferomedially in the same direction as the innermost intercostal muscles.
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