The deltoid muscle is the muscle forming the rounded contour of the human shoulder. It is known as the'common shoulder muscle' in other animals such as the domestic cat. Anatomically, it appears to be made up of three distinct sets of fibers though electromyography suggests that it consists of at least seven groups that can be independently coordinated by the nervous system, it was called the deltoideus and the name is still used by some anatomists. It is called. Deltoid is further shortened in slang as "delt". A study of 30 shoulders revealed an average mass of 191.9 grams in humans, ranging from 84 grams to 366 grams. Previous studies showed that the insertion of the intramuscular tendons of the deltoid muscle formed three discrete sets of muscle fibers referred to as "heads": The anterior or clavicular fibers arise from most of the anterior border and upper surface of the lateral third of the clavicle; the anterior origin lies adjacent to the lateral fibers of the pectoralis major muscle as do the end tendons of both muscles.
These muscle fibers are related and only a small chiasmatic space, through which the cephalic vein passes, prevents the two muscles from forming a continuous muscle mass. The anterior deltoids are called front delts for short. Lateral or acromial fibers arise from the superior surface of the acromion process of the scapula, they are called lateral deltoid. This muscle is called middle delts, outer delts, or side delts for short, they are mistakenly called medial deltoid, wrong, as their origin is the least medial portion of the deltoid. Posterior or spinal fibers arise from the lower lip of the posterior border of the spine of the scapula, they are called posterior deltoid or rear deltoid. Fick divided these three groups of fibers referred to as parts or bands, into seven functional components as did Kapandji and Sakoma Y et al.: the anterior part has two components. In standard anatomical position, the central components lie lateral to the axis of abduction and therefore contribute to abduction from the start of the movement while the other components act as adductors.
During abduction most of these latter components are displaced laterally and progressively start to abduct. From this extensive origin the fibers converge toward their insertion on the deltoid tuberosity on the middle of the lateral aspect of the shaft of the humerus. Though traditionally described as a single insertion, the deltoid insertion is divided into two or three discernible areas corresponding to the muscle's three areas of origin; the insertion is an arch-like structure with strong anterior and posterior fascial connections flanking an intervening tissue bridge. It additionally gives off extensions to the deep brachial fascia. Furthermore, the deltoid fascia contributes to the brachial fascia and is connected to the medial and lateral intermuscular septa; the deltoid is supplied by the posterior circumflex humeral artery and the deltoid branch of the thoracoacromial artery which branches from the axillary artery. The deltoid is innervated by the axillary nerve; the axillary nerve originates from the anterior rami of the cervical nerves C5 and C6, via the superior trunk, posterior division of the superior trunk, the posterior cord of the brachial plexus.
Studies have shown. Three of these lie in the anatomical anterior head of the deltoid, one in the anatomical middle head, three in the anatomical posterior head of the deltoid; these neuromuscular segments are supplied by smaller branches of the axillary nerve, work in coordination with other muscles of the shoulder girdle include pectoralis major and supraspinatus. The axillary nerve is sometimes damaged during surgical procedures of the axilla, such as for breast cancer, it may be injured by anterior dislocation of the head of the humerus. When all its fibers contract the deltoid is the prime mover of arm abduction along the frontal plane; the arm must be medially rotated for the deltoid to have maximum effect. This makes the deltoid an antagonist muscle of the pectoralis major and latissimus dorsi during arm adduction; the anterior fibers assist the pectoralis major to flex the shoulder. The anterior deltoid works in tandem with the subscapularis and lats to internally rotate the humerus; the lateral fibers perform basic shoulder abduction when the shoulder is internally rotated, perform shoulder transverse abduction when the shoulder is externally rotated.
They are not utilized during strict transverse extension such as in rowing movements, which use the posterior fibers. The posterior fibers assist the latissimus dorsi to extend the shoulder. Other transverse extensors, the infraspinatus and teres minor work in tandem with the posterior deltoid as external rotators, antagonists to strong internal rotators like the pecs and lats. An important function of the deltoid in humans is preventing the dislocation of the humeral head when a person carries heavy loads; the function of abduction means that it would help keep carried objects a safer distance away from the thighs to avoid hitting them, as during a farmer's walk. It ensures a precise a
A condyle is the round prominence at the end of a bone, most part of a joint - an articulation with another bone. It is one of the markings or features of bones, can refer to: On the femur, in the knee joint: Medial condyle Lateral condyle On the tibia, in the knee joint: Medial condyle Lateral condyle On the humerus, in the elbow joint: Condyle of humerus On the mandible, in the temporomandibular joint: Mandibular condyle On the occipital bone, in the atlanto-occipital joint: Occipital condylesAlthough not termed condyles, the trochlea and capitulum of the humerus act as condyles in the elbow, the femur head acts as a condyle in the hip joint
The musculocutaneous nerve arises from the lateral cord of the brachial plexus, opposite the lower border of the pectoralis major, its fibers being derived from C5, C6 and C7. The musculocutaneous nerve arises from the lateral cord of the brachial plexus, courses through the anterior part of the arm, terminates at 2 cm above elbow as lateral cutaneous nerve of the forearm. Musculocutaneous nerve arises from the lateral cord of the brachial plexus with root value of C5 to C7 of the spinal cord, it follows the course of the third part of the axillary artery laterally and enters the frontal aspect of the arm where it penetrates the coracobrachialis muscle. It passes downwards and laterally between the biceps brachii and the brachialis muscles, to the lateral side of the arm. In its course through the arm it innervates the coracobrachialis, biceps brachii, the greater part of the brachialis, its terminal branch, the lateral cutaneous nerve of the forearm, supplies the sensation of the lateral side of the forearm from the elbow to the wrist.
Besides, the musculocutaneous nerve gives articular branches to the elbow joint and to the humerus. The musculocutaneous nerve presents frequent communications with the median nerve, it may adhere for some distance to the median and pass outward, beneath the biceps brachii, instead of through the coracobrachialis. Some of the fibers of the median may run for some distance in the musculocutaneous and leave it to join their proper trunk; the nerve may pass through the biceps brachii. It gives a filament to the pronator teres, it supplies the dorsal surface of the thumb when the superficial branch of the radial nerve is absent. Injury to the musculocutaneous nerve can be caused by three mechanisms: repeated microtrauma, indirect trauma or direct trauma on the nerve. Overuse of coracobrachialis and brachialis muscles can cause the stretching or compression of musculocutaneous nerve; those who have it can complain of pain, tingling or reduced sensation over the lateral side of the forearm. This symptom can be reproduced by pressing over the region below the coracoid process.
Pain can be reproduced by flexing the arm against resistance. Other differential diagnoses that can mimick the symptoms of musculocutaneous palsy are: C6 radiculopathy, long head of biceps tendinopathy, pain of the bicipital groove. Electromyography test shows slight neural damage at the biceps and the brachialis muscles with slower motor and sensory conduction over the Erb's point. In indirect trauma, violent abduction and retroposition of the shoulder can stretch and the musculocutaneous nerve lesion; those with this type of lesion is presented with pain, reduced sensation, tingling at the antero-lateral part of the arm and lateral part of forearm with reduced strength of elbow flexion. Tinel's sign can be positive. Differential diagnosis includes C5 and C6 nerve root lesions of the brachial plexus where the abduction, external rotation, elbow flexion is lost. On the other hand, rupture of the biceps can cause the loss of flexion of the elbow without sensory deficits. Electromyography test is negative.
In direct trauma, fracture of the humerus, gun shot, glass pieces injuries and more, can cause the musculocutaneous nerve lesion. Iatrogenic nerve injuries are common and in a certain percentage of cases inevitable, though an adequate knowledge of the surgical anatomy can help to reduce its frequency. Neurolysis and nerve grafting are the treatment options for the above lesions; this article incorporates text in the public domain from page 935 of the 20th edition of Gray's Anatomy Musculocutaneous_nerve at the Duke University Health System's Orthopedics program Hand kinesiology at the University of Kansas Medical Center
In human anatomy, the axillary vein is a large blood vessel that conveys blood from the lateral aspect of the thorax and upper limb toward the heart. There is one axillary vein on each side of the body, its origin is at a continuation of the brachial vein. This large vein is formed by the basilic vein. At its terminal part, it is joined by the cephalic vein. Other tributaries include the subscapular vein, circumflex humeral vein, lateral thoracic vein and thoraco-acromial vein, it terminates at the lateral margin of the first rib. It is accompanied along its course by a named artery, the axillary artery. Gray's s149 lesson3axillaryart&vein at The Anatomy Lesson by Wesley Norman
The coracobrachialis is the smallest of the three muscles that attach to the coracoid process of the scapula. It is situated at the medial part of the arm, it arises from the apex of the coracoid process, in common with the short head of the biceps brachii, from the intermuscular septum between the two muscles. It is inserted by means of a flat tendon into an impression at the middle of the medial surface and border of the body of the humerus between the origins of the triceps brachii and brachialis, it is innervated by the musculocutaneous nerve. Which arises from the anterior division of middle trunks of the brachial plexus; the action of the coracobrachialis is to adduct the arm at the glenohumeral joint. The coracobrachialis resists deviation of the arm from the frontal plane during abduction. Therefore, the contraction of the coracobrachialis leads to two distinct movements at the shoulder joint, it both draws the humerus forward, causing shoulder flexion, draws the humerus toward the torso, causing shoulder adduction.
To a smaller extent, it turns the humerus inwards, causing internal rotation. Another important function of the coracobrachialis is the stabilization of the humeral head within the shoulder joint when the arm is hanging at a person's side; the overuse of the coracobrachialis can lead to stiffening of the muscle. Common causes of injury include chest workouts or activities that require one to press the arm tight towards the body, e.g. work on the rings in gymnastics. Symptoms of overuse or injury are pain in the arm and shoulder, radiating down to the back of the hand. In more severe cases, the musculocutaneous nerve can get trapped, causing disturbances in sensation to the skin on the radial part of the forearm and weakened flexion of the elbow, as the nerve supplies the biceps brachii and brachialis muscles. Actual rupture to the coracobrachialis muscle is rare. Few case reports exist in the literature, it is reported to be caused by direct trauma to the contracted muscle. Avulsion of the muscle's origin from the coracoid as a result of indirect forces is more unusual.
This article incorporates text in the public domain from page 443 of the 20th edition of Gray's Anatomy. PTCentral
The shoulder girdle or pectoral girdle is the set of bones in the appendicular skeleton which connects to the arm on each side. In humans it consists of the scapula; some mammalian species have only the scapula. The pectoral girdles are to the upper limbs. In humans, the only true anatomical joints between the shoulder girdle and the axial skeleton are the sternoclavicular joints on each side. No anatomical joint exists between the rib cage. In those species having only the scapula, no joint exists between the forelimb and the thorax, the only attachment being muscular; the shoulder girdle is the anatomical mechanism that allows for all upper arm and shoulder movement in humans. The shoulder girdle consists of five muscles that attach to the clavicle and scapula and allow for the motion of the sternoclavicular joint and acromioclavicular joint; the five muscles that comprise the function of the shoulder girdle are the trapezius muscle, levator scapulae muscle, rhomboid muscles, serratus anterior muscle, pectoralis minor muscle.
The shoulder girdle is a complex of five joints. Three of these joints are true anatomical joints. Within each group, the joints are mechanically linked so that both groups contribute to the different movements of the shoulder to variable degrees. In the first group, the scapulohumeral or glenohumeral joint is the anatomical joint mechanically linked to the physiological subdeltoid or suprahumeral joint so that movements in the suprahumeral joint results in movements in the glenohumeral joint. In the second group, the scapulocostal or scapulothoracic joint is the important physiological joint that can not function without the two anatomical joints in the group, the acromioclavicular and sternoclavicular joints, i.e. they join both ends of the clavicle. The glenohumeral joint is the articulation between the head of the humerus and the glenoid cavity of the scapula, it is a ball and socket type of synovial joint with three rotatory and three translatory degree of freedom. The glenohumeral joint allows for adduction, abduction and lateral rotation and extension of the arm.
The acromioclavicular joint is the articulation between the acromion process of the scapula and the lateral end of the clavicle. It is a plane type of synovial joint; the acromion of the scapula rotates on the acromial end of the clavicle. The sternoclavicular joint is the articulation of the manubrium of the sternum and the first costal cartilage with the medial end of the clavicle, it is functions as a plane joint. The sternoclavicular joint accommodates a wide range of scapula movements and can be raised to a 60° angle; the scapulocostal joint is a physiological joint formed by an articulation of the anterior scapula and the posterior thoracic rib cage. It is musculotendinous in nature and is formed predominantly by the trapezius and serratus anterior muscles; the pectoralis minor plays a role in its movements. The gliding movements at the scapulocostal joint are elevation, retraction and superior and inferior rotation of the scapula. Disorders of the scapulocostal joint are not common and restricted to snapping scapula.
The suprahumeral joint is a physiological joint formed by an articulation of the coracoacromial ligament and the head of the humerus. It is formed by the acromion process of the scapula; this space is filled by the subacromial bursa and the tendon of supraspinatus. This joint plays a role during complex movements while the arm is flexed at the glenohumeral joint, such as changing a lightbulb, or painting a ceiling. From its neutral position, the shoulder girdle can be rotated about an imaginary vertical axis at the medial end of the clavicle. Throughout this movement the scapula is rotated around the chest wall so that it moves 15 centimetres laterally and the glenoid cavity is rotated 40–45° in the horizontal plane; when the scapula is moved medially it lies in a frontal plane with the glenoid cavity facing directly laterally. At this position, the lateral end of the clavicle is rotated posteriorly so that the angle at the acromioclavicular joint opens up slightly; when the scapula is moved laterally it lies in a sagittal plane with the glenoid cavity facing anteriorly.
At this position, the lateral end of the clavicle is rotated anteriorly so that the clavicle lies in a frontal plane. While this closes the angle between the clavicle and the scapula, it widens the shoulder; the scapula can be elevated and depressed from the neutral position to a total range of 10 to 12 centimetres. During this tilting, the scapula rotates to a maximum angle of 60° about an axis passing perpendicularly through the bone below the spin
Anatomical terms of motion
Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints and specific sections of the body; the terminology used describes this motion according to its direction relative to the anatomical position of the joints. Anatomists use a unified set of terms to describe most of the movements, although other, more specialized terms are necessary for describing the uniqueness of the movements such as those of the hands and eyes. In general, motion is classified according to the anatomical plane. Flexion and extension are examples of angular motions, in which two axes of a joint are brought closer together or moved further apart. Rotational motion may occur at other joints, for example the shoulder, are described as internal or external. Other terms, such as elevation and depression, describe movement above or below the horizontal plane. Many anatomical terms derive from Latin terms with the same meaning. Motions are classified after the anatomical planes they occur in, although movement is more than not a combination of different motions occurring in several planes.
Motions can be split into categories relating to the nature of the joints involved: Gliding motions occur between flat surfaces, such as in the intervertebral discs or between the carpal and metacarpal bones of the hand. Angular motions occur over synovial joints and causes them to either increase or decrease angles between bones. Rotational motions move a structure in a rotational motion along a longitudinal axis, such as turning the head to look to either side. Apart from this motions can be divided into: Linear motions, which move in a line between two points. Rectilinear motion is motion in a straight line between two points, whereas curvilinear motion is motion following a curved path. Angular motions occur when an object is around another object decreasing the angle; the different parts of the object do not move the same distance. Examples include a movement of the knee, where the lower leg changes angle compared to the femur, or movements of the ankle; the study of movement is known as kinesiology.
A categoric list of movements of the human body and the muscles involved can be found at list of movements of the human body. The prefix hyper- is sometimes added to describe movement beyond the normal limits, such as in hypermobility, hyperflexion or hyperextension; the range of motion describes the total range of motion. For example, if a part of the body such as a joint is overstretched or "bent backwards" because of exaggerated extension motion it can be described as hyperextended. Hyperextension increases the stress on the ligaments of a joint, is not always because of a voluntary movement, it may be other causes of trauma. It may be used in surgery, such as in temporarily dislocating joints for surgical procedures; these are general terms. Most terms have a clear opposite, so are treated in pairs. Flexion and extension describe movements; these terms come from the Latin words with the same meaning. Flexion describes a bending movement that decreases the angle between a segment and its proximal segment.
For example, bending the elbow, or clenching a hand into a fist, are examples of flexion. When sitting down, the knees are flexed; when a joint can move forward and backward, such as the neck and trunk, flexion refers to movement in the anterior direction. When the chin is against the chest, the head is flexed, the trunk is flexed when a person leans forward. Flexion of the shoulder or hip refers to movement of the leg forward. Extension is the opposite of flexion, describing a straightening movement that increases the angle between body parts. For example, when standing up, the knees are extended; when a joint can move forward and backward, such as the neck and trunk, extension refers to movement in the posterior direction. Extension of the hip or shoulder moves the leg backward. Abduction is the motion of a structure away from the midline while adduction refer to motion towards the center of the body; the centre of the body is defined as the midsagittal plane. These terms come from Latin words with similar meanings, ab- being the Latin prefix indicating "away," ad- indicating "toward," and ducere meaning "to draw or pull".
Abduction refers to a motion that pulls a part away from the midline of the body. In the case of fingers and toes, it refers to spreading the digits apart, away from the centerline of the hand or foot. Abduction of the wrist is called radial deviation. For example, raising the arms up, such as when tightrope-walking, is an example of abduction at the shoulder; when the legs are splayed at the hip, such as when doing a star jump or doing a split, the legs are abducted at the hip. Adduction refers to a motion that pulls a structure or part toward the midline of the body, or towards the midline of a limb. In the case of fingers and toes, it refers to bringing the digits together, towards the centerline of the hand or foot. Adduction of the wrist is called ulnar deviation. Dropping the arms to the sides, bringing the knees together, are examples of adduction. Ulnar deviation is the hand moving towards the ulnar styloid. Radial deviation is the hand moving towards the radial styloid; the terms elevation and depression refer to movement below the horizontal.
They derive from the Latin terms with similar meaningsElevation refers to movement in a superior direction. For example