The function of the shoulder joint is multiaxial; flexion and extension, abduction and adduction, and mild inward and outward rotation are possible in it. The bellies of all the muscles acting on the shoulder joint (meaning the main action of the muscle), with the exception of the coracobrachialis, lie proximal to the joint - on the scapula. The extensors of the joint include the prespinatus muscle, assisted by the brachiocephalic and biceps brachii muscles. Flexors are: deltoid, teres major and teres minor. They are assisted by the latissimus dorsi muscle, the long head of the triceps brachii muscle and the deep pectoralis muscle. The abductor is the infraspinatus muscle. The adductors are the subscapularis and coracobrachialis muscles. There are no independent supinators and pronators in the joint. The supination function is performed by the deltoid and teres minor muscles, and the pronation function is performed by the teres major muscle.
Prespinatus muscle- m. supraspinatus is a thick lamellar muscle, feathery in structure, fills the entire prespinatus fossa, ends with two legs on the lateral and medial tuberosities of the humerus, bending around the shoulder joint from the cranial side. Function - extends the shoulder joint.
Deltoid- m. deltoideus is a triangular lamellar muscle that lies on top of the infraspinatus muscle. In cattle and pigs, it is divided into two parts: the scapular and acromial. Blade part begins with a lamellar tendon from the spine of the scapula and from the infraspinatus muscle, acromial part- from the acromion. Both parts end on the deltoid roughness of the humerus. The horse only has a shoulder blade. The muscle is of the dynamostatic type in cattle and pigs, and of the statodynamic type in horses; it becomes more static with age. Function - flexes the shoulder joint and supinates it.
Teres minor muscle- m. teres minor - small fusiform, lies caudal to the infraspinatus muscle under the deltoid muscle. It starts from the lower third of the caudal edge of the scapula and ends on the rounded roughness of the humerus. The internal structure is very different in different animal species: from the dynamic type in the sheep, to the static-dynamic type in the horse. Function - flexes the shoulder joint and supinates it.
Teres major muscle- m. teres major - lamellar, ribbon-shaped, lies behind the scapula along the medial surface of the triceps brachii muscle. It starts from the caudal angle of the scapula and ends on the round roughness of the humerus along with the latissimus dorsi muscle. Belongs to the dynamic type. Function - flexes the shoulder joint and pronates it.
Stiaspinatus muscle- m. infraspinatus - a thick muscle lies in the infraspinatus fossa under the deltoid muscle, with which it partially fuses. It starts from the infraspinous fossa and ends on the greater (lateral) tubercle of the humerus. It belongs to the semi-static-dynamic type, and in the horse - to the static-dynamic type. Function: abductor of the shoulder joint. In herbivores it functions as a lateral ligament of the joint.
Subscapularis muscle- m. subscapularis - multipinnate, fills the subscapular fossa, in which it is fixed. In front it borders with the prespinatus muscle, and behind it borders with the teres major muscle. It ends on the medial (lesser) tubercle of the humerus. It belongs to the semi-static-dynamic type in pigs and sheep, to the static-dynamic type in cattle and to the static type in horses, i.e. is a ligament muscle. Function: adductor of the shoulder joint. In herbivores, it functions as a lateral ligament that limits movement in the joint.
Coracobrachialis muscle- m. coracobrachialis - lies on the medial surface of the shoulder joint and humerus. It begins as a narrow long tendon on the coracoid process of the scapula and ends on the medial surface of the humerus near the teres major muscle. In most farm animals it belongs to the semi-static-dynamic type, in horses - to the static-dynamic type. Function - helps adductors.
The functions of the muscles of the shoulder girdle are related to the functions of the muscles of the chest and partly the back. Therefore, the distinction between the torso and the shoulder girdle is very arbitrary. As the contours of the muscles change, the contours of the back, neck and chest also change.
The muscles of the shoulder girdle include:
- Brachialis muscle
- Subscapularis muscle
- Coracobrachialis muscle
The shoulder joint is ball-and-socket. It is formed by the head of the humerus and the glenoid cavity of the scapula. This joint allows flexion (raising the arm forward) and extension (moving the arm back) of the arm in the shoulder joint, adduction (movement of the arms in a horizontal plane at shoulder level forward) and extension (movement of the arms in a horizontal plane at shoulder level back) of the arms, rotation arms in and out, abduction (to the side) and adduction (to the side of the body) of the arm.
Deltoid
The deltoid muscle has the shape of a triangle with the apex facing down. The muscle consists of three bundles, each of which is responsible for moving the arm in different directions. Accordingly, there are three parts of the deltoid muscle: clavicular, acromial and scapular. Beginning with the broad tendon located above the shoulder joint, the three bundles of the deltoid muscle converge into one tendon, which attaches to the humerus. Good development of the deltoid muscle affects the width of the shoulders, despite the fact that their bony base can be quite fragile. All three parts of the deltoid muscle can contract independently of each other
Front bun the deltoid muscle is attached to the collarbone and raises the arm forward (flexion of the arm at the shoulder joint), side bun(lateral) attaches to the acromion of the scapula and raises the arm to the side (arm abduction). Posterior bun The deltoid muscle is attached to the shoulder blade and moves the arm back (extension of the arm at the shoulder joint).
Rotator cuff
The rotator cuff is a group of four muscles that form a protective sleeve around the shoulder joint. Although these muscles are hardly visible, they are extremely important for shoulder stability and strength. All four muscles start from the shoulder blade and pass around the shoulder joint, attaching to the humerus.
Supraspinatus muscle Most of it is covered by the trapezius muscle, but since the latter is quite thin in this part, it cannot completely hide the outline of the supraspinatus muscle. The supraspinatus muscle is located in the supraspinatus fossa of the scapula and is attached to the greater tubercle of the humerus and is responsible for abducting the upper limb and rotating it outward.
Infraspinatus muscle starts from the back of the scapula and attaches to the humerus. Teres minor muscle is a synergist of the subscapularis muscle and the scapular part of the deltoid muscle. The infraspinatus and teres minor muscles are located behind the joint. They raise the arm to the side and move it back, rotating the shoulder outward (supination).
Subscapularis muscle extensive, thick, triangular in shape. Occupies almost the entire costal surface of the scapula. Placed in front of the joint and rotates the arm inward (pronation), while simultaneously bringing the shoulder toward the body.
1. Prespinatus muscle. Origin – fills the entire prespinatus fossa, covered by the trapezius and brachioatlas muscles. Bifurcates above the supraglenoid tubercle of the scapula into two tendons - lateral and medial.
Function– extends the shoulder joint.
Blood supply:
2. Deltoid muscle. Located on the lateral (side) surface of the scapula and shoulder joint. Consists of the scapular and acromial parts.
a) The scapular part begins from the scapular spine and from the infraspinatus muscle.
b) The acromial part originates from the infraspinatus joint and ends on the deltoid roughness of the humerus.
Function
Blood supply: posterior circumflex humeral artery, thoracoacromial artery.
3. Infraspinatus muscle. Fills the infraspinatus fossa of the scapula, is covered by the deltoid muscle, and has a tendon bursa proximally.
Function– abduction of the limb.
Blood supply:
4. Teres minor muscle. Lies under the deltoid muscle, runs from the lower third of the caudal edge of the scapula to the lesser round roughness.
Function– flexes and externally rotates the shoulder joint.
Blood supply: artery circumflexing the scapula.
5. Teres major muscle. Runs from the caudal angle of the scapula to the large round roughness.
Function– flexes and rotates the shoulder joint.
Blood supply: subscapular artery.
6. Coracobrachialis muscle. It begins on the coracoid process of the scapula.
Function– helps to straighten the shoulder joint.
Blood supply: Anterior and posterior arteries surrounding the humerus.
7. Subscapularis muscle. It runs from the subscapular fossa to the medial muscular tubercle of the humerus.
Function– adducts the thoracic limb.
Blood supply: subscapular artery.
Muscles of the shoulder girdle, their blood supply, topography and functions.
The muscles of the shoulder girdle connect the torso to the thoracic limb.
1. Trapezius muscle. It comes from the spine to the outer surface of the scapula (spine).
Functions
Blood supply: transverse artery of the neck, suprascapular, occipital arteries, posterior intercostal arteries.
2. Rhomboid muscle. Lies under the trapezius muscle. Goes to the cartilage of the scapula.
Functions: holds the shoulder blade to the body.
Blood supply: deep cervical and transverse cervical arteries.
3. The latissimus dorsi muscle starts from the first thoracic to the last lumbar vertebrae on the humerus (from the inside).
Functions: pulls back the thoracic limb.
Blood supply: thoracodorsal artery, posterior humeral circumflex artery, posterior intercostal arteries.
4. Atlantoacromial muscle. Located on the lateral surface of the neck between the wing of the atlas and the acromion of the scapula.
Functions: turns his head to the sides and lowers it down.
Blood supply: transverse cervical and common carotid arteries.
5. The superficial and deep pectoral muscles are located between the sternum and the limb.
Functions: bring the limbs to the body.
Blood supply: deep thoracic artery.
6. Serratus ventral muscle. It goes from the ribs and cervical vertebrae to the scapula in the form of a fan.
Functions: The main holder of the torso between the limbs.
Blood supply: dorsal scapular (transverse cervical) and intercostal arteries.
7. Sternopuleucephalic muscle. Extends along the side of the neck from the humerus to the head.
Function: brings the limb forward.
Blood supply: vertebral and common carotid arteries.
Muscle tissue. Chemical composition, physical properties and functions.
Muscles are a typical parenchymal organ. Parenchyma is the first structure, the main working part, characterizing the organ from the functional side. It is represented by bundles of skeletal striated muscle tissue, the function of contraction.
The second structure is the stroma (skeleton), a connective tissue structure, in the form of a shell and performs a protective function. Each muscle is tightly surrounded on the outside by a connective tissue membrane in the form of a case and is called the external perimysium. Contains a small amount of fat. From the external perimysium, blood, lymphatic vessels and nerves penetrate the muscle. They also penetrate into the connective tissue layers - the internal perimysium. Dividing the muscle in the form of partitions into a number of large sections located along the fibers. Layers extend from the internal perimysium - endolysium, which divides it into smaller sections. As a result, the cross-section of the molecules has a mosaic appearance.
In the fusiform muscles, the tendons have a light yellow color, consist of dense connective tissue, the fusiform muscles are located closer to the head, and the location closer to the moving point is the tail. Tendons are a non-tiring part; elasticity softens jerks and makes movements smooth. In some cases, the muscles on the torso pass into wide lamellar tendons, this is called aponeuroses.
Chemical composition:
It consists of 75% water, 25% organic elements, 20% proteins, 2% fats. After slaughter, an obligatory companion is fat, which is deposited in connective tissue formations, is a necessary plastic material, and the main source of water. The melting point of fat varies from animal to animal. Physical properties:
1. stretchability – the ability to change length under the influence of applied force
2. elasticity - the ability of a muscle to restore its original shape after the cessation of the forces causing its deformation.
3. muscle strength - the maximum load that a muscle can still lift.
4. muscle work - the product of the lifted load and the lifting height.
Functions: extensor, rotation - outward, inward, dilator, compressor, adductor, abductor, tensor, elevator.
shoulder joint,articulatio humeri , formed by the head of the humerus and the glenoid cavity of the scapula.
The articular surface of the head of the humerus is spherical, and the glenoid cavity of the scapula is a flattened fossa. The surface of the head of the humerus is approximately 3 times larger than the surface of the glenoid cavity of the scapula. The latter is complemented by the articular labrum, labrum glenoidale.
The joint capsule has the shape of a truncated cone. The upper part of the joint capsule is thickened and forms the coracobrachial ligament, lig. coracohumerale, which begins at the outer edge and base of the coracoid process of the scapula and, passing outward and downward, is attached to the upper part of the anatomical neck of the humerus.
The capsule of the shoulder joint is also strengthened due to the fibers of the tendons of adjacent muscles woven into it (vol.supraspinatus, infraspinatus, teres minor, subscapularis).
The synovial membrane of the articular capsule of the shoulder joint forms two permanent protrusions: the intertubercular synovial sheath and the subtendinous bursa of the subscapularis muscle.
In terms of the shape of the articular surfaces, the shoulder joint is a typical ball-and-socket joint. Movements in the joint are performed around the following axes: sagittal - abduction and adduction of the arm, frontal - flexion and extension, vertical - rotation of the shoulder together with the forearm and hand outwards and inwards. Circular movement is also possible in the shoulder joint.
X-ray examination of the shoulder joint
the head of the humerus, the glenoid cavity of the scapula and the x-ray gap of the shoulder joint are visible.
The shoulder muscles are divided into two groups - the anterior (flexors) and the posterior (extensors).
The anterior group consists of three muscles: the coracobrachialis, biceps brachii and brachialis; posterior - triceps brachii and olecranon.
These two muscle groups are separated from each other by the plates of the shoulder's own fascia: on the medial side - the medial intermuscular septum of the shoulder, on the lateral side - the lateral intermuscular septum of the shoulder
Coracobrachialis muscle
m. coracobrachialis. Function: bends the shoulder at the shoulder joint and brings it to the body. Innervation: m. musculocutaneus. Blood supply: aa. Circumflexae anterior et posterior humeri.
Double-headed muscle shoulder, m. biceps brachii. Function: flexes the shoulder at the shoulder joint, flexes the forearm at the elbow joint. Innervation: n. musculocutaneus. Blood supply: aa. collaterale ulnares superior et inferior, a. brachialis, a. reccurens radialis.
Brachialis muscle, m. brachialis. Function: flexes the forearm in the elbow joint. Innervation: n. musculocutaneus. Blood supply: aa.collaterale ulnares superior et inferior, a. brachialis, a. reccurens radialis.
Triceps brachii muscle, m. triceps brachii, Function: extends the forearm at the elbow joint, the long head acts on the shoulder joint, participating in extension and adduction of the shoulder to the body. Innervation: n. radialis. Blood supply: a. circumflexa posterior humeri, a. profunda brachii, aa, collatera
In the area of the thoracic limbs there are muscles: 1) shoulder girdle; 2) shoulder joint; 3) elbow joint; 4) wrist joint and 5) finger joints.
Rice. 1. Scheme of distribution of muscle groups on the thoracic limb (A – from the lateral surface, B – from the medial):
1 - extensors of the shoulder joint; 2- abductors of the shoulder joint; 3 - extensors of the elbow joint; 4, - wrist extensors; 5 - finger extensors; 6 - flexors of the shoulder joint; 7 - wrist flexors; 8 - finger flexors; 9 - adductors of the shoulder joint; 10 - flexors of the elbow joint.
Muscles of the shoulder joint
In the multiaxial shoulder joint, extension and flexion, abduction and adduction are possible, as well as, although to a weak degree, pronation and supination of the free part of the limb.
Extensors (extensors) pass through the top of the shoulder joint, and flexors (flexors) are located inside the angle of the joint. The abductors lie on the lateral surface of the scapula, the adductors lie on the medial surface of the scapula.
Flexors are assisted by the latissimus dorsi, long head of the triceps brachii, and deep pectoral muscles. The adductors are assisted by the pectoralis muscles, and the abductors are assisted by the rhomboid muscles. The pronators are assisted by the brachiocephalic and pectoralis superficialis muscles and the latissimus dorsi (Figs. 2 and 3).
Extensors:
1. Prespinatus muscle - m. supraspinatus (Fig. 2-4) - pinnate in structure, fills the entire prespinatus fossa, laterally covered by the trapezius muscle. It ends in two legs on the lateral and medial tuberosities of the humerus.
Function - extends the shoulder joint.
Flexors:
1. Deltoid -m. deltoldeus (13) - flat, fleshy, triangular in shape, lies behind the scapular spine. Covers the infraspinatus muscle, with which it is firmly fused with its initial tendon, as well as the teres minor muscle and partially the triceps brachii muscle. Consists of the scapular and acromial parts.
The scapular part begins with a wide lamellar tendon (aponeurosis) from the scapular spine.
The acromial part originates from the acromion. Both parts end on the deltoid roughness of the humerus.
F U N C i I - flexes and supinates the shoulder joint.
2. Teres minor muscle - m. teres minor (6) - lies behind the postospinous; laterally covered by the deltoid muscle. Starts from the distal third of the caudal edge of the scapula. Ends on the ulnar line.
Function - flexes the shoulder joint and supinates it.
3. Teres major muscle - m. teres major (7). Starts from the proximal half of the caudal edge of the scapula. It ends on the rounded roughness of the humerus along with the latissimus dorsi muscle.
FUNCTION - flexes the shoulder joint and pronates it.
Abductors:
1. Stiaspinatus muscle - m. infraspinatus (5) - fills the post-spinous fossa; on the surface it is covered by the deltoid muscle. Begins in the postospinous fossa. It ends on the lateral tubercle of the humerus.
Adductors:
1. Subscapularis muscle - t. subscapulars (3 - 9) - multipinnate, fills the subscapular fossa, in which it is fixed. It ends on the medial tuberosity of the humerus.
2. Coracobrachialis muscle - m. coracobrachial (Fig. 3- 8) . It begins on the coracoid process of the scapula. Ends distally in a circular roughness.
Function - helps adductors.
Fig.2. Muscles of the scapula and shoulder from the lateral surface:
A - dogs; B - horses; B - diagram of the attachment of muscles to bones. 1 - brachiocephalic muscle; 2 - trapezoidal m.; 3 - latissimus dorsi m.; 4 - pre-axle m.; 5 - post-spinous m; 6 - small round m.; 7 - large round m; 8 – coracohumeral m.; 9 – subscapularis m.; 10 – ulnar m.; 11 – tensor fascia of the forearm 12 – biceps brachii; 13 - deltoid m., its scapular part; 13" - deltoid m., its acromial part; 14 - triceps m. humerus, its long head; and 14" - its lateral head; 16 – jagged ventral m.; 17 - shoulder m.; 18-radialis flexor carpi.
Rice. 3. Muscles of the scapula and shoulder from the medial surface:
A - dogs; B - horses; D - diagram of the attachment of muscles to bones.
Muscles of the elbow joint
In a uniaxial elbow joint, only flexion and extension are possible, and in a dog, in addition, rotation of the forearm is possible.
Extensors:
1. Triceps brachii - m. triceps brachii (14) - very powerful, fills the triangular space between the scapula, humerus and olecranon. It consists of three heads: long (two-joint), lateral and medial (one-joint).
Long head - caput longum. Starts from the caudal edge of the scapula, ends on the ulnar tubercle, having under himsubtendinous bursa . Helps flex the shoulder joint.
The lateral head - caput laterale and the medial head - caput mediale start from the proximal third of the humerus, each on its own side. They end on the ulnar tubercle.
.2. Elbow muscle - m. anconaeus (10) - lies under the lateral head of the triceps brachii muscle and is firmly fused with it. Begins at the edges of the cubital fossa; ends on the lateral surface of the ulnar tubercle.
3. Tensioner fascia of the forearm - m. tensor fasciae antebrachii (Fig. 3- 11) , lies on the medial surface of the long head of the triceps brachii muscle, along its caudal edge. It starts from the caudal edge of the scapula and ends on the ulnar tubercle and in the fascia of the forearm.
Function - extends the elbow joint, helps flex the shoulder joint.
Flexors:
1. Biceps brachii - m. biceps brachii (20) - lies on the anterior surface of the humerus.
It starts from the tubercle of the scapula and fits into the intertubercular groove of the humerus. In the area of the humerus trochlea under the tendon there is a synovial vagina . The muscle ends on the roughness of the radius.
2. Brachialis muscle -m. brachialis internus (17) -located directly on the humerus. It begins under the neck of the humerus and ends on the roughness of the radius.
Carpal joint muscles
The wrist joint in domestic animals is uniaxial and allows only flexion and extension.
The bellies of the muscles acting on the carpal joint are located proximal to the joint and lie at the ends of the forearm, with the digital extensors located between the wrist extensors and the digital flexors between the wrist flexors. (Fig. 86, 87).
Extensors:
1. Extensor carpi radialis - m. extensor carpi radialis (Fig. 86- 18) - lies on the dorsal surface of the forearm. It forms the dorsomedial contour of the forearm; begins on the crest of the lateral epicondyle of the humerus, ending on the roughness of the third metacarpal bone.
In the area of the distal quarter of the forearm and on the wrist there is synovial tendon sheath - vagina synovialis tendinis.
2. Abductor pollicis longus - m. abductor pollicis longus (3). It begins on the lateral surface of the radius, crossing the extensor carpi radialis tendon from the dorsal surface, and ends on the head of the second metacarpal bone.
Flexors:
1. Elbow extensor wrists - m. extensor carpi ulnaris (5) . It begins on the extensor epicondyle of the humerus (laterally). Ends on the accessory carpal bone.
Function. Only in dogs, the extensor carpi ulnaris extends the carpus, while in ungulates it acts as a carpal flexor.
2. Flexor carpi radialis - m. flexor carpi radialis (Fig. 87- 11). It begins on the medial (flexor) epicondyle of the humerus and ends on the head of the metacarpal bone.
The tendon in the wrist area is covered with a synovial sheath - vagina synovialis tendinis.
3 . Flexor carpi ulnaris - m. flexor carpi ulnaris (4) - begins on the medial (flexor) epicondyle of the humerus, immediately behind the flexor carpi radialis, ending with a common tendon on the accessory carpal bone.
Muscles of the finger joints
Among the muscles acting on the fingers are: long digital extensors and flexors, and short digital flexors. The long digital extensors include: the common digital extensor and the lateral digital extensor. The bellies of these muscles lie on the dorsolateral surface of the bones of the forearm, between the extensors of the wrist, and their tendons are directed to the fingers: from the common digital extensor to the third phalanges of the fingers, and from the lateral digital extensor to the third and second phalanges of the fingers.
The long flexor fingers are located on the mediovolar surface of the bones of the forearm, also between the flexors of the wrist; these include the superficial and deep digital flexors. Their tendons are directed from the deep flexor digitorum to the third phalanges, and from the superficial flexor digitorum to the second phalanges.
Since the long digital muscles are attached to the epicondyles of the humerus and pass through the ulnar, wrist, metacarpophalangeal, interphalangeal joints, they are multi-articular muscles. Therefore, the finger extensors help the elbow flexors, metacarpal extensors and extend the metacarpophalangeal joints. The finger flexors, on the other hand, help the elbow extensors, metacarpal flexors, and each other.
The short digital flexors are located on the volar surface of the metacarpal bones and act on the metacarpophalangeal joints. In ruminants and horses, these muscles become ligaments that suspend the sesamoid bones.
Extensors:
1. General extensor fingers - m. extensor digitalis communis. It begins on the extensor epicondyle of the humerus and is attached to the extensor process of the distal phalanx.
In the wrist area there is a synovial tendon sheath - vagina tendinis synovitis.
Ruminants have two heads with independent tendons. The medial head is adjacent directly to the extensor carpi radialis and is called the special extensor of the third finger (6).
Function - acts on several joints; it extends the fingers, helps the wrist extensors and the elbow flexors.
2. Lateral extensor digitorum - m. extensor digitalis lateralis (1), or in ruminants - a special extensor of the fourth finger - lies between the common extensor of the digitorum and the extensor carpi ulnaris. Ends on the 2nd phalanx of the fingers.
Function: Extends fingers and wrist.
Flexors:
1. Flexor digitorum superficialis - m. flexor digitalis superficialis (Fig. 87 -9)
Begins directly behind the flexor carpi ulnaris and may have 1 or 2 heads. It ends at the distal end of the first and proximal end of the second phalanx of the corresponding finger.
Function - flexes the fingers and wrist, helps the extensors of the elbow joint.
2. Flexor digitorum profundus - m. flexor digitalis profundus (Fig. 87-8) - lies directly on the volar surface of the bones of the forearm. It begins as a tendon on the medial epicondyle of the humerus, together with the superficial flexor of the digitorum. Under the tendon is the bursa. On a multifingered limb, the tendon gives off separate branches for each finger. In a horse, it is attached to the flexor surface of the coffin bone. It is separated from the navicular bone by a mucous bursa (bursa).
Function - flexes the fingers and wrist, helps the extensors of the elbow joint.
3. Interosseous muscles - m. interosseus (21) - lie on the volar surface of the metacarpal bones. Start from the common volar ligament of the wrist; end in two branches on the sesamoid bones of the metacarpophalangeal joints of each finger.
Muscles of the forearm and paw from the lateral surface.
A – B – dogs; B – pigs; G - cows; D – horses; E – attachment of muscles to bones.
1 - lateral extensor of the fingers, 2 - extensor of the fingers common, 3 - abductor pollicis longus, 4 - flexor carpi ulnaris, 5 - extensor carpi radialis, 6 - extensor of the 3rd finger, 7 - extensor of the 4th finger, 8 - deep flexor digitorum, 9 - superficial flexor digitorum, 10 - ulnaris muscle, 17 - brachialis muscle, 18 - extensor carpi radialis, 21 - interosseous muscle, 21/ - its tendon to the general extensor digitorum.
