Athena Vale
The human body is a complex structure with many muscles that attach to the ribs. These muscles are essential for respiration and movement of the arm and shoulder. The intercostal muscles, for example, occupy the space between the ribs and are divided into three layers: external, internal, and innermost intercostals. They support the rib cage and assist in forced breathing. The thoracic wall is made up of five muscles, including the intercostals, subcostalis, and transversus thoracis. Other muscles that attach to the thoracic wall include the pectoralis major and minor, subclavius, and serratus anterior. The diaphragm, which serves as the main muscle of inspiration, also attaches to the lower ribs. The serratus posterior inferior muscles attach to the inferior borders of the 9th through 12th ribs, and their main action is to depress the inferior ribs.
Explore related products
What You'll Learn
External intercostal muscles
The external intercostal muscles are the most superficial set of muscles that occupy the 11 intercostal spaces between the ribs. There are 11 pairs of external intercostal muscles on both sides of the body. 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 are located superficially to the internal intercostal muscles, separated from them by a thin fascia.
The external intercostal muscles extend from the lateral border of the costal grooves to the superior margins of the ribs below. The fibres of this muscle pass anteroinferiorly in an oblique manner and extend around the thoracic wall from the tubercles to the costal cartilages of the ribs. They originate from the sharp inferior costal border of one rib and insert along the outer lip of the superior border of the rib below. The most posterior fibres of each muscle fuse with the superior costotransverse ligaments, while the most anterior fibres blend with the external intercostal membrane, which fills the remainder of the corresponding intercostal space from the costochondral junction to the sternum.
The external intercostal muscles work in unison with the internal intercostal muscles during inhalation. The internal intercostal muscles relax while the external intercostal muscles contract, causing the expansion of the chest cavity and an influx of air into the lungs. This increases the transverse and anteroposterior diameter of the lungs, which in turn decreases the intrapleural pressure. This process expands the lungs and facilitates the entry of air into them.
The external intercostal muscles are functionally classified as accessory respiratory musculature. They stabilise the position of the ribs during normal respiration and elevate the ribs during forced inspiration, increasing the thoracic volume.
Muscle Milk Taste Test: Is It Any Good?
You may want to see also
Explore related products
Internal intercostal muscles
The internal intercostal muscles are part of the thoracic wall, located in the intercostal spaces between the ribs. They are one of three layers of intercostal muscles, alongside the external and innermost intercostal muscles. There are 11 internal intercostal muscles, filling 11 intercostal spaces by extending between the inferior margin of the superior rib to the superior margin of the first rib below.
How Muscles Function and Their Purpose
You may want to see also
Explore related products
Innermost intercostal muscles
The innermost intercostal muscles are the deepest layer of the thoracic wall. They are located deep to the internal and external intercostals, filling the 11 intercostal spaces between the ribs. The fibres of these muscles are oriented in an inferior and posterior direction.
The innermost intercostals originate from the medial aspect of the costal groove of the rib above and insert onto the internal aspect of the rib below. They are lined internally by the endothoracic fascia, which appears just superficial to the parietal pleura of the lungs.
The precise function of the innermost intercostal muscles is not yet known, but it is highly likely that it is the same as that of the internal intercostal muscles. It is suggested that these muscles depress the ribs and aid in pushing air out of the lungs during forced expiration. This puts them into the category of accessory respiratory musculature that is active only during forced breathing.
The innermost intercostal muscles are innervated by the intercostal nerves, which are the anterior rami of the thoracic spinal nerves. They are supplied by the vessels of the thoracic wall, including the muscular branches of the anterior and posterior intercostal arteries, and the intercostal branches of the internal thoracic and musculophrenic arteries.
How Biking Sculpts and Tones Your Body
You may want to see also
Explore related products
Subcostalis
The subcostalis muscle is one of the five muscles that make up the thoracic cage, the others being the external intercostal, internal intercostal, innermost intercostal, and transversus thoracis muscles. The subcostalis muscle is also known as the subcostal muscle.
The subcostalis muscle is located within the same plane as the innermost intercostal muscles. They are unique in that they may span one, two, or three ribs and become more numerous within the inferior regions of the posterior thoracic wall. The subcostalis muscle originates from the internal aspect of one of the lower ribs and inserts onto the internal aspect of the second or third rib below. The fibres of the subcostalis muscle descend inferomedially in the same fashion as those of the innermost and internal intercostals.
The subcostalis muscle is part of the accessory respiratory musculature, as it aids in forced exhalation. It depresses the ribs during forced exhalation, pulling them towards the central axis of the thorax, which compresses the lungs and pushes the air out of them. The subcostalis muscle is most developed in the lower portion of the thoracic wall.
The subcostalis muscle is 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.
Swimming for Muscle Tone: Effective Exercise?
You may want to see also
Explore related products
Transversus thoracis
The transversus thoracis muscle, also known as triangularis sterni, is a thin plane of muscle fibres located on the inner surface of the anterior chest wall. It is one of the five muscles that make up the thoracic cage, along with the intercostals, subcostal, levatores costarum, and serratus posterior muscles.
The transversus thoracis originates from three points: the inferior third of the posterior surface of the body of the sternum, the posterior surface of the xiphoid process, and the sternal ends of the costal cartilages of ribs 4 to 7. Its fibres diverge and course superolaterally, forming 4 to 5 slips on each side of the sternum. These slips insert into the inner surfaces of the costal cartilages of ribs 2 to 6. The inferior-most fibres of the transversus thoracis lie in a horizontal plane and are continuous with the transversus abdominis muscle. The intermediate fibres run obliquely in a superolateral direction, while the superior-most fibres lie nearly vertically.
The transversus thoracis is an accessory respiratory muscle that is active during forced expiration. It pulls ribs 2 to 6 towards the sternum, resulting in the depression of those ribs and a decrease in the anteroposterior diameter of the thoracic cavity. This muscle also stiffens the thoracic wall during inspiration, preventing paradoxical movements of the chest wall.
The blood supply to the transversus thoracis comes from the sternal branches of the internal thoracic artery, a branch of the subclavian artery. This muscle is innervated by the second to fifth thoracic intercostal nerves, which are the anterior rami of spinal nerves T2 to T6.
The transversus thoracis plays a significant role in heart surgery due to its proximity to the internal thoracic artery, also known as the internal mammary artery (IMA). This artery is commonly used as a transplant vessel for coronary artery bypass surgery because it only needs to be anastomosed on one side and is easily accessible between the first rib and the highest insertion tendon of the transversus thoracis.
Exploring the Palate Muscles: Their Function and Anatomy
You may want to see also
Frequently asked questions
The intercostal muscles are a group of muscles that occupy the space between the ribs. They are divided into three groups: external, internal, and innermost intercostals. The external intercostals form the superficial layer, while the internal intercostals form the inner layer. The innermost intercostals are the deepest layer of the thorax wall.
The intercostal muscles help to change the thoracic volume during respiration. The external intercostals facilitate forced inspiration, while the internal and innermost intercostals aid forced expiration.
Yes, in addition to the intercostal muscles, the subcostalis and the transversus thoracis also make up the thoracic wall. Muscles of the posterior thorax, such as the levatores costarum and serratus posterior superior and inferior, may also aid in respiration.
