Muscles acting on the shoulder girdle. Shoulder muscles. Muscles that supinate and pronate the shoulder
Deltoid(m. deltoideus) (Fig. 90, 101, 104, 106, 111, 112, 113, 114) moves the shoulder outward to a horizontal plane, while the front muscle bundles pull the arm forward, and the rear ones - back. It is a thick, triangular-shaped muscle that covers the shoulder joint and parts of the shoulder muscles. Its large bunches fan-shapedly converge to the apex of the triangle, directed downward. The muscle starts from the axis of the scapula, acromion and lateral part of the clavicle, and attaches to the deltoid tuberosity humerus. Under the lower surface of the muscle is the subdeltoid bursa (bursa subdeltoidea).
Supraspinatus muscle (m. supraspinatus) (Fig. 102, 114) has a triangular shape and lies in the supraspinatus fossa of the scapula, located directly under trapezius muscle. The supraspinatus muscle lifts the shoulder and retracts the capsule of the shoulder joint, preventing it from pinching. The origin of the muscle is on the surface of the supraspinatus fossa, and the attachment point is on the upper platform of the greater tubercle of the humerus and on the posterior surface of the capsule of the shoulder joint.
Infraspinatus muscle(m. infraspinatus) (Fig. 101, 102, 104, 114) turns the shoulder outward, moves the raised arm back and pulls back the capsule of the shoulder joint. This flat muscle triangular in shape, filling the entire infraspinatus fossa. Its upper part is covered by the trapezius and deltoid muscles, and the lower part is covered by latissimus muscle back and teres major muscle. The infraspinatus muscle starts from the wall of the infraspinatus fossa and the posterior surface of the scapula, and is attached to the middle platform of the greater tubercle of the humerus and the capsule of the shoulder joint. At the point of its attachment to the humerus there is a subtendinous bursa of the infraspinatus muscle (bursa subtendinea mm. infraspinati).
| Rice. 111. 1 - muscle that lifts the scapula; 2 — deltoid; 3 - rhomboid minor muscle; 4 - pectoralis minor muscle; 5 - subscapularis muscle; 6 - rhomboid major muscle; 7 - pectoralis major muscle; 8 - serratus anterior muscle; 9 - latissimus dorsi; 10 - coracobrachialis muscle; 11 — triceps shoulder: a) long head, b) medial head; 12 — biceps shoulder; 13 - brachialis muscle; 14 - pronator teres; 15 - aponeurosis of the biceps brachii muscle; 16 - brachioradialis muscle; 17 - fascia of the forearm |
|
| Rice. 112. Muscles of the shoulder and shoulder girdle front view 1 - biceps brachii muscle: a) short head, b) long head; 2 - deltoid muscle; 3 - subscapularis muscle; 4 - coracobrachialis muscle; 5 - teres major muscle; 6 - triceps brachii muscle: a) long head, b) medial head; 7 - brachialis muscle; 8 - biceps brachii tendon |
 |
| Rice. 113. Muscles of the shoulder and shoulder girdle side view 1 - supraspinatus fascia; 2 - infraspinatus fascia; 3 - teres major muscle; 4 - deltoid muscle; 5 - triceps brachii muscle: a) long head, b) lateral head, c) medial head; 6 - biceps brachii; 7 - brachialis muscle; 8 - triceps brachii tendon; 9 - brachioradialis muscle; 10 - extensor carpi radialis longus; 11 - elbow muscle; 12 - fascia of the forearm |
 |
| Rice. 114. Muscles of the shoulder and shoulder girdle rear view 1 - supraspinatus fascia; 2 - supraspinatus muscle; 3 - infraspinatus fascia; 4 - infraspinatus muscle; 5 - teres minor muscle; 6 - teres major muscle; 7 - deltoid muscle; 8 - triceps brachii muscle: a) long head, b) lateral head, c) medial head; 9 - tendon of the triceps brachii muscle; 10 - brachioradialis muscle; 11 - extensor carpi radialis longus; 12 - elbow muscle; 13 - fascia of the forearm |
 |
Teres minor muscle(m. teres minor) (Fig. 101, 102, 104, 114) turns the shoulder outward, at the same time slightly moving it back, and retracts the capsule of the shoulder joint. An oblong, rounded muscle, top part which is adjacent to the infraspinatus muscle, the anterior part is covered by the deltoid muscle, and the posterior part by the teres major muscle. The origin point is located on the posterior surface of the scapula below the infraspinatus muscle, and the attachment point is on the lower platform of the greater tuberosity of the humerus and the posterior surface of the capsule of the shoulder joint.
Teres major muscle(m. teres major) (Fig. 101, 104, 105, 112, 113, 114) turns the shoulder inward and pulls it back, bringing the arm to the body. An oblong flat muscle adjacent to the latissimus dorsi muscle and partially covered by it in the posterior section. In the outer section, the teres major muscle is covered by the deltoid muscle. The starting point is the posterior surface of the scapula at its lower angle, the attachment point is the crest of the lesser tubercle of the humerus. Near the attachment site is the subtendinous bursa of the teres major muscle (bursa subtendinea mm. teretis majoris).
Subscapularis muscle(m. subscapularis) (Fig. 105, 111, 112) rotates the shoulder inward and takes part in its adduction to the body. A flat, triangular-shaped vastus muscle that fills the entire subscapularis fossa. It begins on the surface of the subscapularis fossa and ends on the lesser tubercle of the humerus and on the anterior surface of the capsule of the shoulder joint.
At the attachment site there is a small subtendinous bursa of the subscapularis muscle (bursa subtendinea mm. subscapularis).
One of the most mobile joints in the human musculoskeletal system is the shoulder joint, or articulatio humeri. With the help of this joint a person can perform a variety of active movements. upper limb, which provide the shoulder muscles. A large amplitude is possible due to the special complex structure of the shoulder.
Structural features
The anatomy of the shoulder joint is quite complex. All elements of the joint perform their important functions and provide mobility to the joint. The table for assessing the range of motion in the joints shows that the norm for the shoulder joint is as follows: flexion - 180 degrees, extension - 40, abduction - 180. Thanks to this, the human upper limb can make a full circle. With any damage, a person immediately feels pain in the shoulder and the inability to move the limb.
Shoulder joint belongs to the category of spherical joints. It should not be confused with the shoulder, which starts from the free upper limb to the elbow. It is formed by the humerus and scapula - it belongs to the elements of the upper shoulder girdle. The articular surfaces are represented by the scapula and the head of the humerus. The head itself is several times larger than the articular scapular cavity, but this discrepancy is leveled out by the articular lip - a special plate that exactly copies the bends of the scapular cavity.
The articular capsule is attached along its circumference to the edge of the cartilaginous lip. Inside it is quite free, contains a lot of space, and its walls have different thicknesses. Inside the capsule there is synovial fluid. Since the capsule has the thinnest walls in front, in the event of injury or damage, the integrity of the capsule is disrupted here.
When the hand moves, the tendons are actively involved in the work. They are attached to the surface of the capsule and, during movement, pull it to the side so that it does not become pinched between the articular surfaces of the bones. The ligaments are partially woven into the capsule; they are present here to strengthen it and prevent excessive extension of the arm when making sudden movements.
To reduce friction between the articular planes, synovial bursae, or bursae, are located in the shoulder joint. The main role of the synovial bursae is to soften movements between the articular elements, which are quite densely located in the shoulder. The synovial bursae of the shoulder are the subdeltoid, intertubercular, subcoracoid and subscapular bursae.
REFERENCE. The shoulder joint is endowed with powerful muscular system- corset. the main role shoulder muscles - to protect the joint, but at the same time maintain maximum active movements in it.
The muscles of the shoulder joint allow:
- bring the upper limb towards and away from the body;
- make with hand rotational movements, movement in a circle;
- turn the hand inward or outward;
- raise your hand up and move it back;
- put your hand behind your back.
All these movements are performed due to the fact that the joint is of the spherical type, while its coordinated work is supported by a strong system of ligaments and a muscle corset. Muscle corset divided into anterior and posterior muscle groups. The anterior muscle group of the shoulder consists of the biceps, coracobrachialis and brachialis.
One of the large muscles - the brachialis - is closed in front by the biceps, protecting it from damage. The main role of the brachialis muscle is to flex the upper limb at the forearm. Back group represented by the triceps and ulna, which are designed for extension. The muscles of the upper shoulder girdle are the muscles of the arms, chest, neck and back. Here, for example. The teres major muscle is responsible for adduction and extension of the shoulder.
The rotator cuff is a large muscle of the shoulder. This is not one muscle, but a whole complex of muscle bundles and ligaments that ensure the stable position of the head of the humerus. With the help of the rotator cuff, movements such as rotating the shoulder, raising the arm, and flexing the limb are possible. The rotator cuff includes the following shoulder muscles:
- supraspinatus;
- subscapular;
- infraspinatus;
- round minor muscle.
When you lift your arm up, the rotator cuff slips between the head of the humerus and the articular process of the scapula, which is called the acromion. To make the friction as comfortable as possible, a bursa helps with this. Typically, such movements are coordinated and do not cause problems, but in some cases, when raising the arm up, the cuff may become pinched and impingement syndrome develops. It manifests itself as sharp pain, but it especially increases when you try to move your arm back, behind your back.
The blood supply to the shoulder joint and forearm primarily comes from the axillary artery. This artery is a continuation of the subclavian artery, and itself gives rise to the brachial artery. Starts at the level of the first rib. On three sides, the vessel is surrounded by the nerves of the brachial plexus, and from below, at the point of transition to the brachial vessel, the artery, together with the nerve plexuses, is tightly covered with fascia and subcutaneous fat.
If there are problems with the blood supply to the cartilage of the shoulder joint, arthrosis may develop
In close proximity to the shoulder joint it is divided into smaller vessels. They form two circles: the acromial deltoid and the scapular. These two circles are additional, and if necessary they can redistribute the load. If there is a blockage of a large vascular line, then the shoulder joint and periarticular muscles are provided with nutrition from these circles. Innervation is carried out by the brachial nerve plexus.
The arteries of the shoulder joint consist of the following vessels:
- axillary;
- deltoid;
- acromial;
- thoracoacromial;
- chest;
- posterior envelope;
- lateral thoracic;
- subscapular;
- grospinal;
- front;
- vessel circumflexing the scapula;
- upper ulnar;
- deep;
- shoulder
The vascular system is very branched and complex. It performs all the necessary functions to nourish the muscles and bones of the shoulder joint.
Microanatomy
The surface of the scapular cavity and the head of the humerus are equipped with hyaline cartilage. This is a smooth formation that provides comfortable sliding of the articular elements and protects the bone surface from abrasion. Cartilage consists of a set of collagen fibers that are intertwined but look like arches. This anatomical structure contributes to the correct distribution of pressure and mass that the joint elements feel during movement.
The structure of the joint capsule makes it look like a sac - it tightly covers both bones. On the outside, the capsule has a fibrous layer, which is additionally reinforced with tendon fibers. The superficial layer of the joint capsule also contains nerve fibers and small vessels.
REFERENCE. The inner layer of the capsule is the synovial membrane, consisting of specific cells - synoviocytes. Phagocytic synoviocytes serve to cleanse the intraarticular fluid from the breakdown products it contains, but secretory synoviocytes are responsible for the formation of synovial fluid.
Synovial fluid has a consistency more like egg white - it is transparent and slightly sticky. The key component of synovial fluid is hyaluronic acid. The function of synovial fluid is to lubricate the surfaces of the shoulder joint and also provide nutrition to the cartilage tissue. After all, it is from here that cartilage receives all the necessary nutrients. When there is an excess of synovium, it is absorbed by the vascular network of the membrane.
If a person for some reason does not have enough synovial fluid, then this is considered a pathology. In such a situation, the joints of the shoulder girdle wear out faster, and arthrosis develops on the surface of the joints, since the cartilage tissue does not receive nutrition and slowly wears off and disappears from the surface of the bone.
Pathologies
Most often among all pathologies, the shoulder joint is damaged in the process of dislocation or subluxation. These are severe injuries that are accompanied by other defects. This type of joint injury can also be congenital - such a defect in a child appears as a result of incomplete development of the head of the humerus and scapular processes. They simply don't correspond with each other.
Also, displacement of the elements of the shoulder joint can be caused by muscle weakness, when the muscles do not provide the necessary position to all articular elements, and when the child passes through the birth canal, the shoulders are injured, a dislocation or subluxation occurs. In case of dislocation incorrect position the head of the bone is clearly fixed. At the same time, with subluxation, it can become in the desired position, after which it moves again.
A less common pathology, but still occurring, is muscle hypoplasia. In this case, certain muscles of the shoulder girdle are underdeveloped, which is why a person cannot perform movements in full. Typically, muscle hypoplasia is diagnosed in childhood - the child cannot raise his arms high, cannot place a limb behind his back.
If underdevelopment is diagnosed in ligaments and tendons, then the situation is the opposite. The patient experiences joint hypermobility, which is called laxity. With such a pathology, it is quite difficult to control the articular elements, so a person often experiences dislocations and subluxations.
Shoulder dislocation is a common sports and household injury.
Affects the shoulder joints and arthrosis with arthritis. These are classic diseases of the musculoskeletal system, which cannot but manifest themselves in such a mobile joint as the shoulder. If a person is diagnosed with arthrosis, this means that the surface of his joints loses cartilage tissue. There are four degrees of development of arthrosis, but, unfortunately, painful sensations appear only at the third stage, when significant abrasion of the cartilage is observed.
With this pathology, the bone surface provokes a defensive reaction to pressure from the other side, and the bone becomes covered with osteophytes. Outwardly, they resemble spines or growths that cover the head of the bone. All these processes bring the patient excruciating pain, numbness of the arm, discomfort when turning, during sleep and wakefulness. At the same time, the joint space narrows and movements become limited.
Arthritis is an inflammatory pathology in which the joint elements become inflamed. Arthritis can be triggered by both external infections brought in through the hematogenous route, and autoimmune reactions, when the body, as a result of a malfunction of the immune system, begins to attack its own joint cells, mistaking them for foreign, and an inflammatory process develops. Arthritis also provokes severe pain, the shoulder turns red, body temperature may rise, movements bring severe pain, and patients try to spare the joint.
When shoulder pain occurs, the muscle-ligamentous elements may also be damaged. It is interesting that just by the nature and location of the pain, doctors can almost accurately determine which structure is damaged. For example, if there is pain during abduction of the arm, the injury most likely occurred in the periosteum tendon or in the subacromial bursa.
ADVICE. If a person has problems raising his arm up, then in this case you need to pay attention to the acromial clavicular joint; perhaps the coracobrachial ligament is affected, although the pain will be reflected specifically in the shoulder.
If a person tries to bend the arm inward at the shoulder and experiences pain, this indicates damage to the tendon of the teres minor or infraspinatus muscles. If there is pain when placing your arm behind your back, the problem may lie in damage to the subscapularis muscle. If there is pain when bending the elbow joint, the discomfort may also radiate to the shoulder.
Features in children
The shoulder joint in children has its own characteristics. Firstly, its shape in small patients is different from that in adults. The small and large tubercles in the humerus do not ossify yet, this happens much later - they merge together and form a monolithic bone. Also, due to age-related processes, the distance between the elements of the shoulder in the tendon-ligament apparatus is shortened.
This is why the shoulder joint in children is more vulnerable than in adults. Children often experience shoulder dislocations, especially when the shoulder is hit during play, or when an adult pulls the child's arm too sharply when it is raised up. Sometimes, with a sharp movement of the arm in the shoulder, you can hear a pop, which is emitted by gases dissolved in the synovial fluid. In children, crunching sounds may occur as bones grow. This is fine.
The shoulder joint is an anatomically complex structure that performs the most important functions for a person - it moves the upper limbs, and therefore makes a person functional. The health of the shoulder must be monitored, otherwise diseases and even disability may develop.
Today we have boring stuff on our agenda - that’s how I described the new series of articles on the anatomy of muscle groups, which will now be published on Sundays. In it we will not reveal any secret tricks, but will try to examine in as much detail as possible, without watering down all the “muscle insides” and the kinesiology of movements. Today on the agenda is the anatomy of the shoulder muscles.
So, sit down, my dear friends, let’s start making gestures.
Anatomy of the shoulder muscles: what, why and why?
To be honest, I put off writing such notes until the last minute, and all because they smack of theory very much and there is little practice in them, and such publications are rarely liked by readers, because give them bread and circuses :). However, on the other hand, no self-respecting project simply can exist without such a theoretical section, because this is its foundation, the backbone on which it must stand. Therefore, I will try to cover anatomical issues as painlessly and as non-boringly as possible, and I am sure this cycle will become your favorite on the project.
Why are these types of articles important? Well, firstly, they allow the athlete to intelligently approach exercises with a full understanding of the essence of all the processes taking place. This eliminates the possibility of thoughtless pulling of pieces of iron. Secondly, it is always useful to keep the correct movement mechanics in mind and review them as you perform the exercise. Well, thirdly, showing off your intelligence in front of your teammates in the hall is also worth a lot. Actually, stop pouring water, let's get to the point.
The shoulders (delts) are the most mobile joint in the human body, with the widest and most varied range of motion. The shoulder joint is the most unstable joint and is therefore easily dislodged and damaged. It is more correct to talk about the shoulder in the context of not one joint, but a complex complex of bones, ligaments, muscles and tendons called shoulder girdle. The main function of the latter is to provide strength and range of motion to the arms.
Note:
The deltoid muscles are named after the Greek letter delta - due to its triangular shape.
The shoulder girdle consists of three bones:
- shoulder blades (scapula);
- clavicle;
- humerus (humerus).
The deltoid muscle is attached by tendons to the skeleton using the three bones mentioned above, and its contraction results in a wide range of arm movement.
In cross-section, the shoulder joint (delta) consists of layers:
- bone is the deepest layer;
- nerves and blood vessels;
- tendons, ligaments and muscles;
- skin covering.
Nerves carry (in one direction) signals from the brain to the muscles to move the shoulder and (in the opposite direction) carry signals from the muscles to the brain about pain, pressure exerted on them, etc.
The shoulder itself is a ball joint, the ball of which is the head of the humerus. Above the “ball” is the acromion (upper shoulder). Next to them is the acromioclavicular joint.
There are three joints of the shoulder girdle:
- shoulder joint (GH) – connects the humerus (arm) to chest(breast) . The most important and formative of the joints.
- acromioclavicular (AC) ;
- Sternoclavicular (SC) .
The roundness that we see on our shoulder (or we don’t see it yet :)) consist of 3 individual muscles/heads:
- anterior (anterior delt);
- middle (medial delt);
- posterior (posterior delt).
The deltoids are feathery muscles (attached at an angle to the tendons), this promotes better force production and stabilization, but there is a certain loss in flexibility.
Anatomy of the shoulder muscles: features of the joints
No. 1. Shoulder joint
The most mobile joint, providing most of the movements of the shoulder girdle. It allows you to move your arm forward/backward, from side to side to rotate it in and out, move it along the body in front and behind, and carry out rotational movements counterclockwise and clockwise. All of the above is shown in the figure.
Despite such a wide range of motion, there are certain positions in which the shoulder joints feel uncomfortable, in particular, these include putting your hands behind your head (for example, lowering a barbell behind your head).
The shoulder joint has a separate class of tissues called soft tissues that maintain its stability and mobility. These soft tissues are subject to the most wear and tear (their structures become thinner, the lubricant of the synovial fluid, which allows the articular cartilages to slide, is consumed) and are the first to fail leading to shoulder injury.
Soft tissues include:
- joint capsule;
- shoulder ligaments;
- superior articular labrum – increases the depth of the articular capsule by 50% ;
- long head of the biceps tendon;
- rotator cuff muscles;
- Bursa is a small sac of lubricating fluid that protects the rotator cuff tendons.
The stability of the joint depends on the preservation of the head of the humerus, located in the center of the joint capsule. The humerus itself is held in place by ligaments, tendons and anterior muscles (mostly rotator cuff).
In general, it is worth saying that many athletes do not pay any attention to training the muscles of the rotator cuff, but the stability of the entire shoulder joint and, as a result, the likelihood of injury while working with weights depends on its strength. The rotator cuff is the primary stabilizer during shoulder movement. Four of its muscles are involved in all rotational and overhead movements of the shoulders. Therefore, it is critical to warm up the rotator cuff before training the deltoids using the following exercises.
No. 2. AC joint
Helps connect the arm to the chest area. The acromioclavicular ligament (superior AC) is the most important horizontal stabilizer. The coracoclavicular ligament helps in the vertical stabilization of the collarbone. A significant part of the rotation occurs in the collarbone and around 10% at the junction of the acromioclavicular joint.
No. 3. Sternoclavicular joint
Most of the rotation occurs at the SC joint and its stability is dependent on soft tissue. The posterior sternoclavicular joint capsule is the most important structure to prevent forward and reverse displacement of the medial clavicle.
Now let's move on to...
Anatomy of the shoulder muscles: what you need to know to build huge shoulders
I put the whole theory into a capacious visual drawing, so let’s stare :).
There is a clear separation at the shoulders muscle fibers, and therefore, to give them a spherical shape, it is necessary to work out all three beams during training.
Well, that’s all in theory, now let’s summarize all this information and draw the appropriate conclusions.
FAQ on deltas
- shoulders are a very mobile joint; they take direct and indirect part in many movements (eg bench press);
- beginners should not train deltoids more 1 once a week (provided that there are only three workouts per week);
- the most appropriate training strategy is to work out each beam 1-2 exercise;
- It is best to start training with the lagging group of deltas, most often this is the rear one;
- shoulders require a good warm-up, so take some time 3-5 minutes to carry out the relevant work;
- Always try to include exercises to strengthen the rotator cuff in your deltoids training, and it’s better to start with them.
That's all I have left, all I have to do is get on a date.
Afterword
Today we mastered a theoretical note called “Anatomy of the shoulder muscles.” I would like to remind you that although the article is unpretentious in appearance, it is extremely important and extremely useful, because it will help you to approach the choice of exercises and their implementation much more thoughtfully.
That's it, in that spirit, that way, see you soon!
PS. Friends, our project is included in the ranking of the best websites for BB and fitness. Vote for ABC of Bodybuilding, we deserve to have more of us!
P.P.S. Did the project help? Then leave a link to it as your status social network- plus 100 points towards karma, guaranteed.
With respect and gratitude, Dmitry Protasov.
The muscles of the upper shoulder girdle include the muscles of the arms, chest, upper back and neck.
As is clear from the name, these muscle groups are somehow connected with the shoulder. The shoulder joint is the most complex in the human body.
I won’t give pictures of the joint and ligaments; they make me shiver. brrrrr look for yourself on the net.
The upper limb is the most mobile part of the motor system of the human body. If you describe a hemisphere with an outstretched hand, like a radius, you will get a space in which distal part of the upper limb, the hand, can move in any direction. The high degree of mobility of the upper limb links is due to well-developed muscles, which are usually divided into: muscles of the upper limb girdle and muscles of the free upper limb. At the same time, many muscles of the trunk take part in the movements of the upper limb, which either originate on its bones or are attached to them.
Muscles of the shoulder girdle and shoulder
Muscles of the upper limb girdle
The muscles of the upper limb girdle include: the deltoid muscle, the supraspinatus and infraspinatus muscles, the teres minor and major muscles, and the subscapularis muscle.
It starts from the lower half of the anterior surface of the humerus and from the intermuscular septa of the shoulder, and is attached to the tuberosity of the ulna and its coronoid process. covered anteriorly by the biceps brachii muscle. The function of the brachialis muscle is to participate in flexion of the forearm.
Biceps brachii has two heads, starting on the scapula from the supraglenoid tubercle (long head) and from the coracoid process (short head). The muscle is attached on the forearm to the tuberosity of the radius and to fascia forearms. It belongs to the biarticular muscles. In relation to the shoulder joint it is a flexor of the shoulder, and in relation to the elbow joint it is a flexor and supinator of the forearm.
Since the two heads of the biceps brachii muscle, long and short, are attached to the scapula at some distance from each other, their functions in relation to the movement of the shoulder are not the same: the long head flexes and abducts the shoulder, the short head flexes and adducts it. In relation to the forearm, it is a powerful flexor, since it has a much greater leverage of force than , and, in addition, it is an instep support, much stronger than the actual instep support of the forearm. The supinator function of the biceps muscle decreases somewhat due to the fact that with its aponeurosis the muscle passes into fascia forearms.
The biceps brachii muscle is located on its anterior surface directly under the skin and its own fascia; the muscle is easily palpable both in its muscular part and in the tendon part, at the point of attachment to the radius. The tendon of this muscle is especially noticeable under the skin when the forearm is bent. Under the outer and inner edges of the biceps brachii muscle are clearly visible medial And lateral shoulder grooves.
Located on the back of the shoulder, it has three heads and is a biarticular muscle. It is involved in the movements of both the shoulder and forearm, causing extension and adduction in the shoulder joint and extension in the elbow.
The long head of the triceps muscle begins from the subarticular tubercle of the scapula, and medial And lateral head - from the posterior surface of the humerus ( medial- below, and lateral- above the groove of the radial nerve) and from the internal and external intermuscular septa. All three heads come together to one tendon, which, ending on the forearm, is attached to the olecranon process of the ulna. This large muscle lies superficially under the skin. Compared to its antagonists, the shoulder and forearm flexors, it is weaker.
Between medial And lateral with the heads of the triceps brachii muscle, on the one hand, and the humerus, on the other, there is a brachio-muscular canal; the radial nerve and the deep brachial artery pass through it.
Elbow muscle starts from lateral epicondyle of the humerus and radial collateral ligament, as well as from fascia; it is attached to the upper part of the posterior surface and partly to the olecranon process of the ulna in its upper quarter. The function of the muscle is to extend the forearm.
Considering all the muscles located in the area of the shoulder joint, it is easy to notice that there are no muscles inside or below it. Instead, there is a depression called the axillary cavity, which has important topographical significance, since vessels and nerves pass through it to the upper limb.
The shape of the axillary cavity somewhat resembles a pyramid, with its base facing downwards and outwards, and its apex facing upwards and inwards. It has three walls, of which the anterior one is formed by the large and small pectoral muscles, posterior - subscapularis, teres major and latissimus dorsi, medial- serratus anterior muscle. The following muscles pass through the depression between the anterior and posterior walls: the coracobrachialis and the short head of the biceps brachii. The axillary cavity at its apex has a gap located between the first rib and the clavicle (subclavian muscle). When the shoulder is abducted, the axillary fossa is clearly visible, corresponding to the location of the axillary cavity. The hole is especially well marked if the muscles are tense. During shoulder adduction, it is smoothed out.
40. Muscles of the shoulder girdle. Attachments and functions
The shoulder girdle, which strengthens the free limb on the body, is connected to it by only one sternoclavicular joint. Strengthening the shoulder girdle is carried out by muscles that originate on the torso and were discussed earlier. These are the trapezius, pectoralis minor, rhomboid, serratus anterior and levator scapulae muscles. Here we will describe the muscles located on the shoulder girdle itself, which move and fix the free upper limb in the shoulder joint. These include the deltoid, supraspinatus, infraspinatus, teres minor, teres major and subscapularis muscles (see Atl.).
Deltoid muscle (t. deltoide-us) together with the ball-shaped shoulder joint, it determines the rounded shape of the human shoulder (see Atl.). The muscle originates from the acromial end of the clavicle, the crest and acromial process of the scapula, and is attached to the deltoid roughness of the humerus. Under the muscle there is a synovial bursa, sometimes communicating with the cavity of the shoulder joint. The anterior muscle bundles, contracting, take part in flexing the arm in the shoulder joint, the posterior ones in its extension, and the middle and the entire muscle as a whole abduct the arm to a horizontal position, after which the humerus rests against the humeral arch and movement in the joint is inhibited.
Supraspinatus muscle (i.e. supraspinatus) starts from the supraspinatus fossa of the scapula and the dense fascia covering it, and is attached to the top of the greater tubercle of the humerus (see Atl.). The muscle is a synergist of the deltoid, but is capable of abducting only the unloaded arm, although more quickly.
Infraspinatus muscle (t. infraspinatus) starts from the infraspinatus fossa of the scapula and from the dense fascia covering the muscle, and is attached to the greater tubercle of the humerus (see Atl.). The muscle rotates the shoulder outward.
Teres minor muscle lies under the previous one (see Atl.). It starts from the lateral edge of the scapula, attaches to the greater tubercle of the humerus, and works as a synergist of the infraspinatus muscle.
Teres major muscle starts from the lower angle of the scapula, attaches together with the latissimus dorsi muscle to the crest of the lesser tubercle of the humerus (see Atl.). The muscle rotates the shoulder inward.
Subscapularis muscle (t. subscapularis) starts from the entire costal surface of the scapula, attaches to the lesser tubercle of the humerus (see Atl.). Beneath the muscle lies a small bursa that protrudes from the cavity of the shoulder joint. The muscle rotates the shoulder inward.
The supraspinatus, infraspinatus, teres minor and subscapularis muscles, located in close proximity to the shoulder joint, fuse with its bursa. By contracting, they tighten the bag and prevent it from pinching.
41. Shoulder muscles. Attachments and functions
In the shoulder area there are two groups of muscles: anterior (consists of flexors) and posterior (consists of arm extensors in the shoulder and elbow joints) (see Atl.). These muscles are surrounded by the fascia of the shoulder, which forms separate sheaths around each group, which are separated by intermuscular septa. The latter extend deep from the fascia of the shoulder, where they fuse with the humerus.
The anterior group is formed by the coracobrachialis, biceps and brachialis muscles, and the back - triceps and ulna.
Coracobrachialis muscle (t. coracobrachialis), starting from the coracoid process, attaches to the anterior surface of the middle third of the shoulder, bends the arm at the shoulder joint.
Biceps muscle (biceps brachii) with its short head it begins together with the coracohumeral from the coracoid process. The long head originates inside the joint cavity from the supraglenoid tuberosity of the scapula (see Atl.). Having passed through the bursa, the tendon of the long head lies in the intertubercular groove, surrounded by a process of the synovial layer of the bursa, due to which the tightness of the joint is not broken. Below, both heads are connected. Spreading over the elbow joint, the muscle attaches to the tuberosity of the radius; here, between the tendon and the tuberosity, there is a synovial bursa. Some of the tendon fibers are woven into the fascia of the forearm and significantly strengthen it (see Atl.). The muscle flexes the arm at the shoulder and elbow joints and supinates the forearm (Fig. 1.57).
Brachial muscle (brachialis) starts from the lower two thirds of the anterior surface of the humerus, from the medial and lateral intermuscular septa, and is attached to the tuberosity of the ulna. The muscle flexes the forearm.
Triceps muscle (t. triceps brachii), located on the dorsum of the shoulder, it works as an antagonist of the muscles of the anterior group. Of the three heads of the muscle, the long one originates from the subarticular tuberosity of the scapula; the lateral (more powerful) and medial (weaker) heads start from the back of the humerus and intermuscular septa, located on the sides of the long head. The muscle is attached by a common tendon to the olecranon process of the ulna. The triceps muscle extends the arm at the elbow joint, and its long head also extends the shoulder joint.
The olecranon process remains uncovered by muscles; Between it and the skin there is a subcutaneous synovial bursa.
Elbow muscle (t. anconaeus) – small, triangular. Starting from the external epicondyle of the humerus, it goes obliquely inward; it is covered by dense fascia of the forearm, from which it partially begins; attaches to the posterior edge of the ulna (see Atl.). The muscle, like the triceps, extends the arm at the elbow joint. Fusing with the capsule of the elbow joint, the muscle retracts it.
