Muscles of the trunk: names and functions

Muscles play a big role in the human body - this is the active part of our motor apparatus. The passive part is formed by fascias, ligaments and bones. From muscle tissue, all the skeletal muscles are composed of : trunk, head and limbs. Their reduction occurs arbitrarily.

Muscles of the trunk and extremities, like the muscles of the head, are surrounded by fasciae - connective tissue membranes. They cover the areas of the body and on them get their name (fascia of the shoulder, chest, hip, forearm, etc.).

About 40% of the total body weight is in the adult human skeletal muscle. In children, they account for about 20-25% of body weight, and in older people - up to 25-30%. There are about 600 different skeletal muscles in the human body. They are divided according to the location of the muscles of the neck, head, lower and upper extremities, as well as the trunk (they include the muscles of the abdomen, chest and back). Let us dwell on the latter in more detail. We will describe the functions of the muscles of the trunk, give the name of each of them.

Muscles of the breast

Segmental structure retains the underlying musculature of the thoracic region, as does the skeleton of this region. In three layers are located here the muscles of the trunk:

1) internal intercostal;

2) external intercostal;

3) transverse muscle of the breast.

The diaphragm is functionally connected with them.

Intercostal external and internal muscles

Intercostal external muscles are located on all intercostal spaces from the costal cartilage to the spine. Their fibers go in a direction from top to bottom and forward. Since the lever of the force (arm of the lever) is longer at the point of attachment of the muscle than at the beginning of it, the muscles lift the ribs when cutting. Thus, in the transverse and anteroposterior directions, the volume of the thorax increases. These muscles are one of the most important ones for inspiration. The most dorsal their fascicles, which originate from the thoracic vertebrae (their transverse processes), stand out as the ribs that lift the ribs.

Internal intercostals occupy about 2/3 of the front intercostal space. Their fibers go in a direction from below upwards and forward. Cutting, they ensure the lowering of the ribs and thus contribute to exhalation, reducing the size of the human chest.

The transverse muscle of the breast

It is located at the chest wall, on its inner side. Its reduction promotes exhalation.

In 3 intersecting directions lie the fibers of the muscles of the chest. This structure helps to strengthen the chest wall.

Diaphragm

The cuticle barrier (diaphragm) separates the abdominal cavity from the chest. Even in the early period of embryonic development this muscle is formed from cervical myotomes. She moves back as the lungs and heart develop, until she takes a permanent place in a 3 month old fetus. The diaphragm, according to the place of the bookmark, is supplied with a nerve, which departs from the cervical plexus. It is domed in shape. The diaphragm consists of muscle fibers starting along the circumference of the lower orifice located in the chest. Then they pass to the tendon center occupying the top of the dome. The heart is located in the middle part of this dome. In the medullary obstruction there are special openings through which esophagus, aorta, lymphatic duct, veins, nerve trunks pass. It is the main respiratory muscle. When the diaphragm contracts, its dome drops and the thorax increases in the vertical dimension. The lungs are mechanically stretched and inhaled.

Functions of the muscles of the chest

As you can see, the main function of the muscles listed above is participation in the respiratory mechanism. Inhale is caused by those of them that increase the volume of the chest. It occurs in different people, or mainly due to the diaphragm (the so-called abdominal type of breathing), or due to the intercostal external muscles (thoracic type of breathing). These types can vary, they are not strictly constant. Muscles that help reduce the volume of the chest, are activated only with increased exhalation. For exhalation, it is usually sufficient to have the plastic properties that the thorax itself has.

Other muscles of the breast

From the edge of the sternum, the sternal part of the clavicle and the cartilages of five or six upper ribs, a large pectoral muscle originates. It is attached to the humerus, the crest of its large tubercle. Between him and the muscular tendon there is a synovial bag. The muscle, cutting, permeates and leads the shoulder, pulls it forward.

Under the large is located a small pectoralis muscle. It starts from the second to the fourth ribs, joins the beak-like process and pulls the scapula in the direction of down and forward with contraction.

The anterior dentate muscle originates on the second-ninth ribs with nine prongs. It connects to the scapula (its medial margin and lower corner). The main part of its bundles is connected with the latter. The muscle, when contracted, pulls forward the scapula, and its lower corner extends outwards. The scapula therefore rotates around the sagittal axis, the lateral angle of the bone rises. If the hand is withdrawn, rotating the scapula, the anterior dentate muscle raises an arm above the shoulder joint.

Abdominal muscles

We continue to examine the muscles of the trunk and move on to the next group. Entering her own abdominal muscles form the abdominal wall. Let's consider each of them.

Straight and pyramidal muscles

The rectus abdominis starts from the cartilages of the fifth to seventh ribs, as well as the xiphoid process. It is attached to the symphysis of the outside outside of it. This muscle is intercepted transversely with the help of 3 or 4 tendon bridges. There is a straight muscle in the fibrous vagina, formed by aponeuroses of oblique muscles.

The next, pyramidal muscle, is small, often it is completely absent. It is the vestigial of the baguette muscle found in mammals. It begins near the symphysis of the symphysis. This muscle, tapering upward, is attached to the white line, with contraction pulling it.

Outer and inner oblique muscle

The outer oblique originates from the lower ribs by eight tufts. Its fibers go in a direction from top to bottom and forward. This muscle is attached to the ilium (its crest). From the front, she passes into aponeurosis. The fibers of the latter participate in the formation of the vagina of the rectus muscle. They are intertwined along the middle line with the fibers of the aponeuroses located on the other side of the oblique muscles, thus forming a white line. The free lower edge of the aponeurosis is thickened, tucked inside. It forms the inguinal ligament. Its ends are strengthened on the lumpa tubercle and the ilium (its anteroposterior bone).

The internal oblique muscle originates from the crest of the ilium, as well as from the chest-lumbar fascia and inguinal ligament. Then it follows from below upwards and forwards and joins with the three lower ribs. In the aponeurosis pass the lower fascicles of the muscle.

The transverse muscle originates from the chest-lumbar fascia, the lower ribs, the inguinal ligament and the ilium. It passes in front in the aponeurosis.

Functions of abdominal muscles

Different functions are performed by the abdominal muscles. They form the wall of the abdominal cavity and retain the internal organs due to their tone. These muscles, contracting, narrow the abdominal cavity (basically it affects the transverse muscle) and act as an abdominal press on the internal organs, contributing to the excretion of feces, urine, vomit, a shock on coughing and the birth act, and also bend forward the spine Straight muscles flexing the trunk), turn it around the longitudinal axis and to the sides. As you can see, their role in the human body is very great.

Muscles of the back

Describing the main muscles of the trunk, we approached the last group - the muscles of the back. Let's talk about them. Like on the chest, on the back your own muscles are in the depths. They are covered with muscles, which move the upper limbs into motion and strengthen them on the trunk. Two terminating muscles on the ribs refer to the back muscles (ventral): the lower lower and the upper upper jagged muscles. Both of them take part in the respiratory act. The lower lowers the ribs, and the upper lifts them. These muscles stretch the chest, acting simultaneously.

Along the spinal column , deep muscles of the back pass under the posterior jagged muscles. They have a dorsal origin. They retain a primitive location in man, more or less metameric. They are on both sides of the spine, its spinous processes, extending from the skull to the sacrum.

Between the transverse processes of the adjacent vertebrae are the intertransitory muscles. They are involved in contraction in the direction of the spine.

Intermittent muscles participate in its extension. They are between adjacent vertebrae (their spinous processes).

Occipital-vertebral short muscles (there are 4 of them) are located between the atlas, the occipital bone and the axial vertebra. They rotate and unbend the head.

Functions of the muscles of the back

The fact that a large number of spinal muscles are present in the human body is associated with the differentiation of the whole body and spine in particular. The vertical position of a person provides the power of this musculature. The trunk without it would bend forward. After all, it is in front of the spine that the center of gravity lies. In addition, this group includes some muscles that lift the trunk. Agree, their significance is very great.

In 2 layers the group of muscles of the back connected with the upper limbs is located. The trapezius and the broadest muscle lie in the surface layer. In the second there is a diamond-shaped, as well as lifting shoulder blade.

In addition to the above-described value, the muscles of the upper limb located on the trunk have both. For example, those that attach to the blade do not just set it in motion. They fix the shoulder blade when the antagonistic muscle groups simultaneously contract. In addition, if the limb is immobilized by the tension of other muscles, then when they contract, they no longer act on the limb itself, but on the chest. They expand it, that is, they act as auxiliary muscles of inspiration. These muscles use the body with difficulty and increased breathing, in particular, in physical work, running or respiratory diseases.

So, we looked at the basic muscles of the trunk. Anatomy is a science that requires in-depth study. A superficial examination of individual questions does not allow us to see the entire system as a whole. Meanwhile, the muscles of the trunk and neck are only part of the complex mechanism by which we control our body.