The musculoskeletal system of the human body is a real miracle of nature. It supports all parts of the body in the right position, protects the vital organs and provides amazing mobility to the entire body. The girdle of the upper limbs is responsible for attaching the arms to the axial skeleton.
Clavicle and shoulder blade construction
The composition of the girdle of the upper limbs implies a construction of two shoulder blades, two clavicles and the skeleton of the limb itself. It is the belt of the upper limbs that creates the shape of a person's shoulders. The arms are connected to the body by the shoulder blades and collarbones, which form the girdle of the upper limbs. The shoulder blades are located at the top of the back, have a triangular shape, they are connected to the spine and ribs with the help of muscles. The shoulder blade is paired with the clavicle, and the clavicle is connected to the sternum and ribs. The clavicle has the appearance of a curved bone passing between the sternum and the outer angle of the scapula.
The skeleton of the upper limb girdle is built from the followingparts:
- 2 collarbones;
- 2 spatulas;
- shoulder bones;
- radius bones;
- ulna bones;
- wrists;
- metacarpal bones;
- phalanges of fingers.
Function of the upper limb belt
The main function of the belt of the upper limbs of a person is to create a strong and maneuverable support for the hands. Unlike the pelvic girdle, it is not rigidly connected to the axial skeleton. The main bones of the girdle of the upper limbs: the clavicle, which forms a regular joint with the sternum, and the scapula is connected to the bones of the body with powerful muscles. As a result, the shoulders actively participate in the movements of the hands, increasing the amplitude and, accordingly, the efficiency of work.
The bones of the girdle of the upper extremities of a person have a structure similar to that of the skeleton of vertebrates, and consist of 3 sections - the shoulder, forearm and hand. The muscles associated with this belt strengthen the shoulder joint and are responsible for most of the movements of the arms. Shoulder blade - a wide plate in the form of a triangle, located behind the chest from the back, is part of the belt of the upper limbs. It has a flat cavity of the shoulder joint, in which the head of the humerus is placed. The shoulder joint is relatively unstable, providing maximum range of motion, but is susceptible to dislocations and other injuries.
Main arm bones
The humerus is presented in the form of a long tubular bone of the girdle of the upper limbs, two fairly long ulna and radius bones are attached to it. Brachial boneforms the elbow joint with both bones, and the hand connects to only one of them - the wrist joint. The ulna is placed on the inside. All the bones of the hand are connected to each other thanks to the joints.
Main ones:
- shoulder;
- wrist;
- elbow.
Joints are very diverse in movement, with active mobility that led to the transformation of the forelimb, that is, the arm, in the course of evolution into an organ of labor. The bones of the ulna and radius are more stable than the humerus, respectively, the movements are less free. Even stronger knuckles. The arm and leg are very similar in skeletal structure. Their main difference is the device of the hand, in which the thumb is located separately from the rest, which allows the hand to make grasping movements. Between the wrist and the metacarpal bone of this finger is the only saddle joint in the human body, the movements in which are much freer than at the base of the first toe.
The structure of the elbow joint
Girdle of the upper limbs includes the elbow joint, which consists of two parts: block-shaped and spherical. The first connects the protrusion of the humerus with the ulnar notch, it also provides flexion-extension movements with the hands. The spherical part connects the head of the humerus with the radial fossa. This allows for twisting of the forearm. In general, the joint is quite stable due to the large joint surface and strong ligaments. The radius is the main bone in the forearm. It forms a joint with the wrist. Elbow bonetogether with the radius forms the elbow joint.
The structure of the shoulder joint
The upper limb belt includes the shoulder joint. The shoulder joint is the most mobile in the human body. Its almost flat cavity on the shoulder blade is articulated with the hemispherical head of the humerus. This device allows you to freely rotate your hand in all directions. The bone turns almost in a circle, up and down. Such mobility has its drawbacks, due to the fact that the strength of the connection is lowered, dislocations often occur in this joint. The second joint is formed by the scapula and collarbone. It often sprains when falling on an outstretched hand or when hit in front of the shoulder.
Hand
This part of the hand has a rather complex design. The hand consists of 3 sections, which, in turn, have 27 bones. At the base of the palm are 5 metacarpal bones and 8 carpal bones. The skeleton of the fingers themselves is made up of 14 phalanges, 2 bones in the thumb and 3 in each of the four. The hand has a highly specialized structure. In infants, they are only indicated, gradually forming, they will be clearly visible only by the age of seven, and their ossification is completed much later, by about 10-13 years. By the same period, the ossification of the phalanges of the fingers is completed.
Ligaments and muscles of the girdle of the upper limbs
Since the shoulder joint is quite mobile, and the shoulder girdle is not rigidly connected to the axial skeleton, the musclesupper limb belts have a special function. Muscles connect the arm to the body and act as shock absorbers. The deltoid muscle is the largest and strongest in the shoulder, connecting the scapula and the humerus. It is thanks to her that the arm rises and moves back and forth.
The rotator cuff is made up of four smaller muscles:
- infraspinatus;
- supraspinous;
- small round;
- subscapularis.
They also control the rotation of the arm and strengthen the shoulder joint.
The main muscles of the girdle of the upper limb
The upper limb has a pair of main muscles: biceps and triceps, which form a pair of antagonists: if one contracts, the other of them relaxes. The biceps, or biceps brachii, runs from the shoulder blade to the radius. If you bend your arm strongly, you can feel it well. The triceps, or triceps brachii, connects the scapula to the ulna. It is not as noticeable, but larger than the biceps. When moving, they act as one muscle group. For example, when lifting the forearm, the biceps, the muscle that pulls the forearm toward the shoulder, contracts. At the same time, the triceps, an extensor muscle, is also stretched, which allows you to straighten the arm again.
Extensors and flexors
Complex movements of the wrist and hand are provided mainly by the coordinated work of many muscles passing through the forearm. These are flexors and extensors. The flexors bring the palm closer to the forearm and squeeze the fingers. They run along the inside of the arm. The extensors straighten the hand andfingers, bringing their back surface closer to the forearm. To open the palm and take an object with it, the coordinated work of 35 muscles of the forearm and hand is required. In addition, the muscles of the forearm deflect the hand to the left and right, rotate it, turn the palm and fix the wrist and fingers in the desired position. Fine finger movements are controlled by the bone's own muscles, which run from the carpal bones to the base of the first phalanges. The work of the remaining phalanges is provided by long flexor and extensor tendons located in the forearm.
Age and prevention of bone aging
Human upper limb belt needs anti-aging prophylaxis. As we age, bone strength decreases and the risk of fractures increases. Age-related bone loss is almost irreversible, but they can and should be prevented or significantly slowed down. Overstrain of the muscles of the shoulders and back is fraught with a very painful condition. People who spend all day at the computer and desk often slouch or hunch over. This causes stiffness in constantly tense muscles and stretching of the muscles of the shoulders and back, which threatens to cause painful muscle knots and tension headaches.
It is necessary to strengthen the belt of the upper limbs, namely the muscles of the shoulders and back, through exercises that straighten the chest and unload the muscles and ligaments. It is very useful to reduce and dilute the shoulders, as well as shrugging the shoulders. Exercise relieves pain, strengthens muscles and bones, increases flexibilitybody, and hence the mobility and ability to work.
