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The trunk of the body is the central, main part of the body that houses all the internal organs. It includes the chest, abdominal, and pelvic regions of the body. The trunk muscles are all of the muscles of the axial skeleton, including the muscles that make up the head, neck, abdomen, chest, pelvis, and back. The trunk muscles are responsible for maintaining posture, protecting underlying organs, and moving the vertebral column. They also play a crucial role in respiration. The diaphragm, a dome-shaped muscle, is a key muscle in controlling respiration. The trunk muscles can be categorized into anterior, posterior, and abdominal muscles.
| Characteristics | Values |
|---|---|
| Definition | The trunk muscles are all of the muscles of the axial skeleton. |
| Location | The trunk of the body is the central, main part of the body that houses all of the internal organs. It includes the chest, abdominal, and pelvic regions. |
| Function | The muscles in the trunk are responsible for making and keeping the body erect, sitting and standing up, and maintaining that posture. They are also involved in movements of the trunk, mainly flexion and rotation. |
| Number of muscles | While the exact number of trunk muscles is unknown, more than half of the 650-800 muscles in the body are found in the trunk. |
| Types of muscles | Anterior trunk muscles include chest and abdominal muscles. Posterior trunk muscles include intrinsic, superficial, and intermediate muscles. |
| Examples of anterior chest muscles | Pectoral muscles, intercostal muscles, subcostal muscles, transversus thoracis, and diaphragm. |
| Examples of abdominal muscles | Rectus abdominis, external oblique muscles, internal oblique muscles, and transversus abdominis muscle. |
| Examples of posterior trunk muscles | Intrinsic posterior muscles, superficial posterior muscles, and intermediate posterior muscles. |
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What You'll Learn
- The trunk contains over half of the body's 650+ muscles
- Trunk muscles include chest, abdominal, pelvic, back, and pectoral muscles
- The diaphragm is a dome-shaped muscle that separates the thorax and abdomen
- The rectus abdominis muscle is often referred to as the 'six-pack'
- Trunk muscles help protect underlying organs and move the vertebral column
The trunk contains over half of the body's 650+ muscles
The trunk of the body is the central, main part of the body that houses all the internal organs. It includes the chest, abdominal, and pelvic regions. The trunk contains over half of the body's 650+ muscles. The exact number of trunk muscles is unknown.
The trunk muscles are all the muscles of the axial skeleton, which includes the muscles that make up the head, neck, abdomen, chest, pelvis, and back. The muscles found in the trunk help to protect the underlying organs and move the vertebral column. They are also involved in movements of the upper limb and respiration.
The chest muscles include the pectoral muscles, intercostal muscles, subcostal muscles, transversus thoracis, and diaphragm. The intercostal muscles are located in the spaces between the ribs and play a key role in respiration. The diaphragm is a dome-shaped muscle that forms a partition between the thorax and the abdomen, and it is the main muscle of breathing.
The abdominal muscles include the rectus abdominis or "six-pack abs," and the obliques. The rectus abdominis is a long, strap-like, paired muscle that passes vertically over the entire length of the abdomen. It acts as a flexor of the trunk and an accessory muscle of expiration. The obliques assist during bending and twisting of the torso. The abdominal oblique muscles include the external and internal oblique muscles, which are involved in trunk flexion, ipsilateral rotation, and compression of abdominal viscera.
The pelvic muscles include the pelvic outlet, which is formed by two muscular sheets and their associated fascia.
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Trunk muscles include chest, abdominal, pelvic, back, and pectoral muscles
The trunk, or torso, is the central part of the body to which the head and limbs are attached. Trunk muscles include chest, abdominal, pelvic, back, and pectoral muscles.
The trunk muscles support the thoracic cage and attach to the axial skeleton of the trunk. They also support the body and enable movement. They are divided into two large groups, depending on their location.
The chest muscles include the pectoralis major, pectoralis minor, serratus anterior, subclavius, and subcostal muscles. The pectoralis major is a large, fan-shaped, superficial muscle located on the anterior thoracic wall. It forms the bulk of the chest area and can be easily seen on the surface in some people, for example, weightlifters.
The abdominal muscles include the rectus abdominis, pyramidalis, external abdominal oblique, internal abdominal oblique, and transversus abdominis. The rectus abdominis is a long, strap-like, paired muscle that passes vertically over the entire length of the abdomen. It acts as a flexor of the trunk and an accessory muscle of expiration. It can sometimes be seen beneath the skin in athletic individuals, resulting in what is commonly referred to as a 'six-pack'.
The pelvic outlet is formed by two muscular sheets and their associated fascia.
The back muscles include the erector spinae, which is a large muscle mass that extends from the sacrum to the skull. These muscles are primarily responsible for extending the vertebral column to maintain erect posture.
The diaphragm is a large, dome-shaped muscle located within the trunk. It separates the thoracic and abdominal cavities and is the main muscle of breathing, responsible for inspiration.
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The diaphragm is a dome-shaped muscle that separates the thorax and abdomen
The diaphragm has a crucial role in respiration. When the diaphragm contracts, it increases the internal height of the thoracic cavity, resulting in a decrease in intrathoracic pressure. This allows the lungs to expand and facilitates inspiration. Conversely, when the diaphragm relaxes, along with the natural elasticity of the lung tissue and thoracic cage, expiration occurs.
In addition to its respiratory function, the diaphragm assists in increasing intra-abdominal pressure, which is essential for various expulsive actions such as vomiting, defecation, urination, and childbirth. It also provides a passageway for structures passing between the thorax and abdomen, including the inferior vena cava, esophagus, and aorta. These structures pass through openings in the diaphragm called hiatuses.
The diaphragm is composed of three parts: the sternal, costal, and lumbar. The sternal part originates from the posterior aspect of the xiphoid process, while the costal part arises from the internal surfaces of the lower costal cartilages and ribs 7-12. The lumbar part, on the other hand, originates from the bodies of vertebrae L1-L3, intervertebral discs, anterior longitudinal ligament, and arcuate ligaments.
The diaphragm is subject to various conditions, one of which is herniation. Herniation occurs when there is a congenital malformation, and the diaphragm fails to act as an effective barrier between the thorax and abdomen. This can lead to the presence of abdominal contents, such as the intestines, in the thorax, impacting the development of the lungs. Herniation typically requires immediate surgical repair, especially in cases of large herniation, which have a high mortality rate.
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The rectus abdominis muscle is often referred to as the 'six-pack'
The trunk of the body is the central, main part of the body that houses all the internal organs. It includes the chest, abdominal, and pelvic regions. The trunk muscles are all the muscles of the axial skeleton, including the muscles that make up the head, neck, abdomen, chest, pelvis, and back.
The rectus abdominis muscle is a pair of segmented skeletal muscles on the ventral aspect of a person's abdomen. It is also known as the abdominal muscle or simply the "abs". The rectus abdominis is contained in the rectus sheath, which consists of the aponeuroses of the lateral abdominal muscles. The rectus abdominis is the top layer of the abdominal muscles, commonly referred to as the "six-pack".
The rectus abdominis muscle is a long, strap-like, paired muscle that passes vertically over the entire length of the abdomen. The muscle originates from the pubic crest and pubic symphysis and inserts onto the xiphoid process of the sternum and the costal cartilages of the 5th to 7th ribs. The muscle is separated at the midline by a band of dense connective tissue called the linea alba.
The rectus abdominis muscle acts as a flexor of the trunk and an accessory muscle of expiration. It also helps to keep the internal organs intact and in creating intra-abdominal pressure, such as when exercising or lifting heavy weights. It assists with breathing and plays an important role in respiration when forcefully exhaling, as seen after exercise or in conditions where exhalation is difficult.
The rectus abdominis muscle can be targeted and isolated through specific exercises. For instance, the sit-up exercise requires raising the trunk against gravity to the midline and slowly lowering it down repeatedly in multiple sets. To isolate the rectus abdominis, the exercise can be performed while bending the knees to minimize the engagement of hip flexors.
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Trunk muscles help protect underlying organs and move the vertebral column
The trunk of the body is the central, main part of the body that houses all the internal organs. It includes the chest, abdominal, and pelvic regions. The trunk muscles are all of the muscles of the axial skeleton, including the muscles that make up the head, neck, abdomen, chest, pelvis, and back. The trunk muscles are responsible for making and keeping the body erect, as well as maintaining posture. They also help protect the underlying organs and move the vertebral column.
The trunk muscles can be grouped into chest or thoracic cavity muscles and stomach or abdominal cavity muscles. The chest muscles include the pectoral muscles, intercostal muscles, subcostal muscles, transversus thoracis, and diaphragm. The diaphragm is a large, dome-shaped muscle that separates the thoracic and abdominal cavities and facilitates the passage of anatomical structures. It is the main muscle responsible for breathing and inspiration. The intercostal muscles are located in the spaces between the ribs and play a key role in respiration.
The abdominal muscles include the rectus abdominis or straight muscles, and the obliques or not straight muscles. The rectus abdominis is a long, strap-like muscle that passes vertically over the entire length of the abdomen. It acts as a flexor of the trunk and an accessory muscle of expiration. It also helps to compress the abdominal contents to protect them. The obliques assist during bending and twisting of the torso. The abdominal oblique muscles are involved in trunk flexion, ipsilateral rotation, and compression of abdominal viscera.
The trunk muscles, with their various groups and functions, play a crucial role in protecting the underlying organs and facilitating movement of the vertebral column, thus contributing to the overall stability and functionality of the human body.
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