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Encyclopedia > Shoulder
Shoulder
Diagram of the human shoulder joint
Capsule of shoulder-joint (distended). Anterior aspect.
Latin articulatio humeri
Gray's subject #81 313
Dorlands/Elsevier a_64/12161240
This article is about the body part. See hard shoulder for the road segment.

In human anatomy, the shoulder comprises the part of the body where the arm attaches to the torso. It is made up of three bones: the clavicle (collarbone), the scapula (shoulder blade), and the humerus (upper arm bone) as well as associated muscles, ligaments and tendons. The articulations between the bones of the shoulder make up the shoulder joints. The shoulder must be flexible for the wide range of motion required in the arms and hands and also strong to allow for actions such as lifting, pushing and pulling. Image File history File links Shoulderjoint. ... Image File history File links Gray327. ... Latin is an ancient Indo-European language originally spoken in Latium, the region immediately surrounding Rome. ... Elseviers logo. ... A hard shoulder or simply shoulder is a reserved area alongside the verge of a road or motorway. ... Human anatomy or anthropotomy is a special field within anatomy. ... Collarbone and collar bone redirect here. ... Left scapula - front view () Left scapula - rear view () In anatomy, the scapula, or shoulder blade, is the bone that connects the humerus (arm bone) with the clavicle (collar bone). ... The humerus is a long bone in the arm or fore-legs (animals) that runs from the shoulder to the elbow. ...

Contents

Joints of the shoulder

There are three joints of the shoulder: The glenohumeral, acromioclavicular, and the sternoclavicular joints. This does not cite its references or sources. ... This article or section does not cite its references or sources. ... The sternoclavicular articulation is a double arthrodial joint. ...


Glenohumeral joint

The glenohumeral joint is the main joint of the shoulder and the generic term "shoulder joint" usually refers to it. It is a ball-and-socket joint that allows the arm to rotate in a circular fashion or to hinge out and up away from the body. It is formed by the articulation between the head of the humerus and the lateral scapula. The "ball" of the joint is the rounded, medial anterior surface of the humerus and the "socket" is formed by the glenoid fossa, the dish-shaped portion of the latter scapula. A joint (articulation) is the location at which two bones make contact (articulate). ... Glenoid fossa redirects here, for the other use of Glenoid fossa please see mandibular fossa. ...


The capsule is a soft tissue envelope that encircles the glenohumeral joint and attaches to the scapula, humerus, and head of the biceps. It is lined by a thin, smooth synovial membrane. This capsule is strengthened by the coracohumeral ligament which attaches the coracoid process of the scapula to the greater tubercle of the humerus. There are also three other ligaments attaching the lesser tubercle of the humerus to lateral scapula and are collectively called the glenohumeral ligaments. The joint capsules or articular capsules form complete envelopes for the freely movable bone joints. ... The synovium or synovial membrane is a thin, weak layer of tissue which lines the non-cartilaginous surfaces within the joint space, sealing it from the surrounding tissue. ...


There is also a ligament called semicirculare humeri which is a transversal band between tuberculum minus and majus of the humerus( between posterior sides of these tuberculi). This band is one of the most important strengtening ligaments of the joint capsule.


Acromioclavicular joint

The acromioclavicular (AC) joint is located between the acromion process of the scapula (part of the scapula that forms the highest point of the shoulder) and the distal end of the clavicle. The acromioclavicular joint, or AC joint, is a joint at the top of the shoulder. ... The acromion process, or simply the acromion, is an anatomical feature on the scapula. ...


The capsule of this joint is reinforced by the coracoclavicular ligament between the scapula and clavicle at the point of articulation.


Sternoclavicular joint

The sternoclavicular occurs at the medial end of the clavicle with the manubrium or top most portion of the sternum. The clavicle is triangular and rounded and the manubrium is convex the two bones articulate. The sternoclavicular articulation is a double arthrodial joint. ... Sternum or breastbone is a long, flat bone located in the center of the thorax (chest). ...


Movements of the shoulder

The shoulder is capable of a wide range of motion. Just the scapula itself is capable of 6 types of movements: lateral and medial movement, elevation (upward motion), depression (downward motion), and rotation which simultaneously move the clavicle. The combination of the movement of the scapula with the arm muscles gives a wide range of motion to the arm. The shoulder joints aid the arm in flexion, extension, abduction, and adduction as well as lateral and medial rotation.


Major muscles

The muscles that are responsible for movement in the shoulder attach to the scapula, humerus, and clavicle.

Name Attachments Function
serratus anterior Originates on the surface of the upper eight ribs at the side of the chest and inserts along the entire anterior length of the medial border of the scapula. It fixes the scapula into the thoracic wall and aids in rotation and abduction of the shoulders.
subclavius Located inferior to the clavicle, originating on the first rib and inserting on the subclavian groove of the clavicle. It depresses the lateral clavicle and also acts to stabilize the clavicle.
pectoralis minor Arises from the third, fourth, and fifth ribs, near their cartilage and inserts into the medial border and upper surface of the coracoid process of the scapula. This muscle aids in respiration, medially rotates the scapula, protracts the scapula, and also draws the scapula inferiorly.
sternocleidomastoid Attaches to the sternum (sterno-), the clavicle (cleido-), and the mastoid process of the temporal bone of the skull. Most of its actions flex and rotate the head. In regards to the shoulder, however, it also aids in respiration by elevating the sternoclavicular joint when the head is fixed.
levator scapulae Arises from the transverse processes of the first four cervical vertebrae and inserts into the vertebral border of the scapula. It is capable of rotating the scapula downward and elevating the scapula.
rhomboid major and rhomboid minor (work together) They arise from the spinous processes of the thoracic vertebrae T1 to T5 as well as from the spinous processes of the seventh cervical and first thoracic vertebrae. They insert on the medial border of the scapula, from about the level of the scapular spine to the scapula's inferior angle. They are responsible for downward rotation of the scapula with the levator scapulae, as well as adduction of the scapula.
trapezius Arises from the occipital bone, the ligamentum nuchae, the spinous process of the seventh cervical, and the spinous processes of all the thoracic vertebrae, and from the corresponding portion of the supraspinal ligament. It inserts on the lateral clavicle, the acromion process, and into the spine of the scapula. Different portions of the fibers perform different actions on the scapula: depression, upward rotation, elevation, and adductions.

Serratus anterior Serratus anterior muscle is the surface of upper 9 ribs at side of chest - anterior aspect along entire length of medial border of scapula - (protraction) draws medial border of scapula away from vertebrae (upward rotation). ... This article is about the bones called ribs. ... The medial border of the scapula (vertebral border, medial margin) is the longest of the three borders, and extends from the medial to the inferior angle. ... The Subclavius is a small triangular muscle, placed between the clavicle and the first rib. ... The first rib is the most curved and usually the shortest of all the ribs; it is broad and flat, its surfaces looking upward and downward, and its borders inward and outward. ... On the medial part of the clavicle is a broad rough surface, the costal tuberosity (rhomboid impression), rather more than 2 cm. ... Location The pectoralis minor muscle takes its origin from the 3rd to 5th ribs, near their costal cartilages. ... In human beings, the coracoid process is a small hook-like structure that comes off the scapula to point forward. ... In human anatomy, the sternocleidomastoid muscles are muscles in the neck that acts to flex and rotate the head. ... The sternum or breastbone is a long, flat bone located in the center of the thorax (chest). ... Collarbone and collar bone redirect here. ... The mastoid process (or mastoid bone) is a conical bump of the posterior portion of the temporal bone that is situated behind the ear in humans and many other vertebrates and serves as a site of neck muscle attachment (the Sternocleidomastoid, Splenius capitis, and Longissimus capitis). ... The temporal bones (os temporales) are situated at the sides and base of the skull. ... The levator scapulae is a muscle of the back that affects the scapula. ... A cervical vertebra Cervical vertebrae (Vertebrae cervicales) are the smallest of the true vertebrae, and can be readily distinguished from those of the thoracic or lumbar regions by the presence of a foramen (hole) in each transverse process. ... The medial border of the scapula (vertebral border, medial margin) is the longest of the three borders, and extends from the medial to the inferior angle. ... The rhomboid major is a muscle on the back that connects the scapula with the vertebrae of the spinal column. ... The Rhomboideus minor arises from the lower part of the ligamentum nuchæ and from the spinous processes of the seventh cervical and first thoracic vertebræ. It is inserted into the base of the triangular smooth surface at the root of the spine of the scapula, and is usually separated from... The spinous process of a vertebra is directed backward and downward from the junction of the laminae, and serves for the attachment of muscles and ligaments. ... A typical thoracic vertebra The thoracic vertebrae (vertebrae thoracales) compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. ... The inferior angle of the scapula, thick and rough, is formed by the union of the vertebral and axillary borders; its dorsal surface affords attachment to the Teres major and frequently to a few fibers of the Latissimus dorsi. ... Trapezius In human anatomy, the trapezius is a large superficial muscle on a persons back. ... The occipital bone [Fig. ... The Nuchal ligament is a fibrous membrane, which, in the neck, represents the supraspinal ligaments of the lower vertebræ. It extends from the external occipital protuberance and median nuchal line to the spinous process of the seventh cervical vertebra. ... The supraspinal ligament (supraspinous ligament) is a strong fibrous cord, which connects together the apices of the spinous processes from the seventh cervical vertebra to the sacrum; at the points of attachment to the tips of the spinous processes fibrocartilage is developed in the ligament. ... The acromion process, or simply the acromion, is an anatomical feature on the scapula. ... The spine of the scapula is a prominent plate of bone, which crosses obliquely the medial four-fifths of the dorsal surface of the scapula at its upper part, and separates the supra- from the infraspinatous fossa. ...

Rotator cuff

The rotator cuff is a structure composed of tendons that, with associated muscles (supraspinatus, infraspinatus, teres minor and subscapularis), holds the ball at the top of the humerus in the glenoid socket and provideoulder joint. The tendons of the rotator cuff muscles also connect to the capsule of the glenohumeral joint. The rotator cuff is an anatomical term given to the group of muscles and their tendons that act to stabilize the shoulder. ... // Supraspinatus muscle The supraspinatus is a relatively small muscle of the upper limb that takes its name from its origin from the supraspinous fossa superior to the spine of the scapula. ... The Infraspinatus muscle is a lateral rotator of the glenohumeral joint. ... The Teres minor is a narrow, elongated muscle of the rotator cuff. ... The Subscapularis is a large triangular muscle which fills the subscapular fossa, and arises from its medial two-thirds and from the lower two-thirds of the groove on the axillary border of the bone. ...


Two filmy sac-like structures called bursae permit smooth gliding between bone, muscle, and tendon. They cushion and protect the rotator cuff from the bony arch of the acromion. A bursa is also a fluid filled sac located between a bone and tendon which normally serves to reduce friction between the two moving surfaces. ...


Measurement of shoulder loads

An instrumented shoulder endoprosthesis, with a 9-channel telemetry transmitter to measure six load components in vivo (http://www.biomechanik.de).
An instrumented shoulder endoprosthesis, with a 9-channel telemetry transmitter to measure six load components in vivo (http://www.biomechanik.de).

For understanding normal and pathologic shoulder function knowledge of forces in the glenohumeral joint is essential. It forms the basis for performing fracture treatment or joint replacement surgery, for optimizing implant design and fixation and for improving and verifying analytical biomechanical models of the shoulder. With instrumented shoulder implants the joint contact forces and moments can be measured in vivo during different activities. Image File history File linksMetadata Download high-resolution version (797x1181, 164 KB) Instrumented shoulder endoprosthesis, Biomechanics Laboratory, Charité - Berlin, Germany, http://www. ... Image File history File linksMetadata Download high-resolution version (797x1181, 164 KB) Instrumented shoulder endoprosthesis, Biomechanics Laboratory, Charité - Berlin, Germany, http://www. ...


Additional images

See also

Each year, shoulder problems account for about 1. ... The armpit (or axilla) is the area on the human body directly under the joint where the arm connects to the shoulder. ...

References

  • Calais-Germain, Blandine. "Anatomy of Movement", Eastland Press, 1993. ISBN 0-939616-17-3
  • Martini, Frederic; Timmons, Michael; McKinnley, Michael. "Human Anatomy", 3rd Edition, Prentice-Hall, 2000. ISBN 0-13-010011-0

External links

Look up Shoulder in
Wiktionary, the free dictionary.

  Results from FactBites:
 
Shoulder - Wikipedia, the free encyclopedia (422 words)
In human anatomy, the shoulder joint is composed of three bones: the clavicle (collarbone), the scapula (shoulder blade), and the humerus (upper arm bone).
The glenohumeral joint, to which the generic term "shoulder joint" usually refers, is a ball-and-socket joint that allows the arm to rotate in a circular fashion or to hinge out and up away from the body.
Tendons are tough cords of tissue that attach the shoulder muscles to bone and assist the muscles in moving the shoulder.
Hard shoulder - Wikipedia, the free encyclopedia (884 words)
In Ireland, the hard shoulder is demarcated by road markings in the form of a single dashed yellow line (solid line on motorways), possibly with the addition of yellow cat's eyes (green when a junction is upcoming and the shoulder is temporarily closing).
In the USA, the right-hand shoulder is separated by a solid white line, and the left-hand shoulder (if the road is a divided highway) is separated from the main road by a solid yellow line.
Hard shoulders are always marked with a reflectorised solid white line which is 20 cm wide and is provided with a rumble strip.
  More results at FactBites »

 
 

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