Muscles play a big role in the human body - this is the active part of our motor apparatus. The passive part is formed by fascia, ligaments and bones. All skeletal muscles are composed of muscle tissue: the trunk, head and limbs. Their reduction is arbitrary.
The muscles of the trunk and limbs, like the muscles of the head, are surrounded by fascia - connective tissue membranes. They cover areas of the body and get their name from them (fascia of the shoulder, chest, thigh, forearm, etc.).
About 40% of the total body weight in an adult is skeletal muscle. In children, they account for about 20-25% of body weight, and in the elderly - up to 25-30%. There are only about 600 different skeletal muscles in the human body. They are divided according to their location into the muscles of the neck, head, lower and upper limbs, as well as the trunk (these include the muscles of the abdomen, chest and back). Let's take a closer look at the latter. We will describe the functions of the muscles of the body, give the name of each of them.
Chest muscles
Segment althe structure is retained by the muscles of the chest region lying in the depths, as well as the skeleton of this region. The muscles of the body are located here in three layers:
1) internal intercostals;
2) external intercostals;
3) transverse chest muscle.
Aperture is functionally related to 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 the direction from top to bottom and forward. Since the lever of force (lever arm) is longer at the point of attachment of the muscle than at its beginning, the muscles raise the ribs during contraction. Thus, in the transverse and anteroposterior directions, the volume of the chest increases. These muscles are among the most important for inhalation. Their most dorsal bundles, which originate from the thoracic vertebrae (their transverse processes), stand out as the levator rib muscles.
Internal intercostals occupy about 2/3 of the anterior intercostal space. Their fibers go in the direction from the bottom up and forward. As they contract, they lower the ribs and thus promote exhalation, reducing the size of the human chest.
Transverse chest muscle
It is located at the chest wall, on the inside of it. Its contraction promotes exhalation.
The fibers of the chest muscles lie in 3 intersecting directions. This structure helps to strengthen the chest wall.
Aperture
Pectoralan obstruction (diaphragm) separates the abdominal cavity from the thoracic cavity. Even in the early period of embryonic development, this muscle is formed from the cervical myotomes. It moves back as the lungs and heart develop, until it takes a permanent place in the 3-month-old fetus. The diaphragm, according to the place of laying, is supplied with a nerve that departs from the cervical plexus. It is domed in shape. The diaphragm consists of muscle fibers starting around the circumference of the lower opening located in the chest. Then they pass into the tendon center occupying the top of the dome. The heart is located in the middle left part of this dome. In the abdominal barrier there are special openings through which the esophagus, aorta, lymphatic duct, veins, and nerve trunks pass. It is the main respiratory muscle. When the diaphragm contracts, its dome descends and the chest increases in vertical size. At the same time, the lungs are mechanically stretched and inspiration occurs.
Chest Muscle Functions
As you can see, the main function of the muscles listed above is to participate in the respiratory mechanism. Inhalation is caused by those that increase the volume of the chest. It occurs in different people either 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 change, they are not strictly constant. Muscles that contribute to a decrease in the volume of the chest are activated only with increased exhalation. For exhalation, the plastic properties of the chest itself are usually sufficient.
Other chest muscles
From the edge of the sternum, the sternal part of the clavicle and the cartilage of five or six upper ribs, the pectoralis major muscle originates. It attaches to the humerus, the crest of its greater tubercle. Between it and the muscle tendon is a synovial bag. The muscle, contracting, penetrates and adducts the shoulder, pulling it forward.
Under the pectoralis major is the pectoralis minor. It originates from the second to fourth ribs, joins with the coracoid process, and pulls the scapula downward and forward as it contracts.
The serratus anterior originates from the second to ninth ribs with nine teeth. It connects to the scapula (its medial edge and lower angle). The main part of her bundles is connected with the latter. During contraction, the muscle pulls the scapula forward, and its lower angle outwards. Due to this, the scapula rotates around the sagittal axis, the lateral angle of the bone rises. If the arm is abducted, rotating the scapula, the serratus anterior raises the arm above the shoulder joint.
Abdominal muscles
We continue to consider the muscles of the body and move on to the next group. Included in it own abdominal muscles form the abdominal wall. Let's take a look at each one.
Direct and pyramidal muscles
The rectus abdominis muscle starts from the cartilage of the fifth-seventh ribs, as well as the xiphoid process. It is attached to the pubic symphysis outside of it. This muscle is intercepted transversely with the help of 3 or 4 tendon jumpers. The rectus muscle is located in a fibrous sheath formed by aponeurosesoblique muscles.
The next muscle, the pyramidal muscle, is small, often absent altogether. It is a vestige of the pouch muscle found in mammals. It begins near the pubic symphysis. This muscle, tapering upward, attaches to the white line, pulling it when contracted.
External and internal obliques
The outer oblique originates from the lower ribs in eight bundles. Its fibers go in the direction from top to bottom and forward. This muscle is attached to the ilium (its crest). In front, it passes into the aponeurosis. The fibers of the latter are involved in the formation of the sheath of the rectus muscle. They intertwine along the midline with the fibers of the aponeuroses located on the other side of the oblique muscles, thereby forming a white line. The free lower edge of the aponeurosis is thickened, turned inside. It forms the inguinal ligament. Its ends are fixed on the pubic tubercle and ilium (its anterior superior bone).
The internal oblique muscle originates from the iliac crest, as well as from the thoracolumbar fascia and inguinal ligament. Then it follows from the bottom up and forward and connects with the three lower ribs. The lower muscle bundles pass into the aponeurosis.
The transverse muscle originates from the thoracolumbar fascia, lower ribs, inguinal ligament and ilium. It passes from the front into the aponeurosis.
Functions of the abdominal muscles
Different functions are performed by the abdominal muscles. They form the wall of the abdominal cavity and hold the internal organs due to their tone. These muscles, contracting, narrow the abdominal cavity (inthis mainly concerns the transverse muscle) and act as an abdominal press on the internal organs, contributing to the excretion of feces, urine, vomit, a push when coughing and childbirth, and also bend the spine forward (mainly the rectus muscles that bend the body), turn it around longitudinal axis and to the sides. As you can see, their role in the human body is very high.
Back muscles
Describing the main muscles of the trunk, we come to the last group - the muscles of the back. Let's talk about them. As on the chest, on the back, your own muscles are in depth. They are covered with muscles that set the upper limbs in motion and strengthen them on the body. Two underdeveloped muscles ending on the ribs belong to the own musculature of the back (ventral): the posterior lower and posterior upper dentate. Both of them take part in the respiratory act. The lower one lowers the ribs, and the upper one raises them. These muscles stretch the chest while acting simultaneously.
The deep muscles of the back pass under the serratus posterior muscles along the spinal column. They are of dorsal origin. They retain a primitive arrangement in humans, more or less metameric. They are located on both sides of the spine, its spinous processes, extending from the skull to the sacrum.
The transverse muscles are located between the transverse processes of the neighboring vertebrae. They are involved in contraction in abduction to the sides of the spine.
The interspinous muscles are involved in its extension. They are located between adjacent vertebrae (their spinous processes).
Occipital-vertebral short muscles (there are 4 in total) are located between the atlas, the occipital bone and the axial vertebra. They rotate and extend the head.
Functions of the back muscles
The fact that such a large number of spinal muscles is represented in the human body is associated with the differentiation of the whole body and the spine in particular. The vertical position of a person provides the power of this muscle. The torso without it would bend forward. After all, it is in front of the spine that the center of gravity lies. In addition, some muscles that raise the body also belong to this group. Agree, their value is very great.
In 2 layers there is a group of back muscles connected with the upper limbs. The trapezius and latissimus dorsi lie in the superficial layer. The second contains a diamond-shaped, as well as levator scapula.
In addition to the above meaning, the muscles of the upper limb located on the body have another. For example, those that attach to the scapula don't just set it in motion. They fix the scapula when 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 are used by the body in case of difficult and increased breathing, in particular, during physical work, running or respiratory diseases.
So, we have considered the main muscles of the body. Anatomy is a science,requiring deep study. Superficial consideration of individual issues does not allow us to see the whole system as a whole. Meanwhile, the muscles of the trunk and neck are only part of a complex mechanism by which we control our body.
