Describe the bones that form the pectdental girdleList the functions of the pectoral girdle

The appendicular skeleton includes all of the limb bones, plus the bones that unite each limb through the axial skeleton ((Figure)). The bones that attach each upper limb to the axial skeleton form the pectoral girdle (shoulder girdle). This is composed of two bones, the scapula and clavicle ((Figure)). The clavicle (collarbone) is an S-shaped bone located on the anterior side of the shoulder. It is attached on its medial finish to the sternum of the thoracic cage, which is part of the axial skeleton. The lateral end of the clavicle articulates (joins) with the scapula simply above the shoulder joint. You have the right to quickly palpate, or feel through your fingers, the entire length of your clavicle.

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The axial skeleton forms the main axis of the body and is composed of the skull, vertebral column, and also thoracic cage. The appendicular skeleton consists of the pectoral and also pelvic girdles, the limb bones, and also the bones of the hands and also feet.


The scapula (shoulder blade) lies on the posterior element of the shoulder. It is sustained by the clavicle, which additionally articulates with the humerus (arm bone) to create the shoulder joint. The scapula is a flat, triangular-shaped bone with a significant ridge running throughout its posterior surface. This ridge extends out laterally, where it develops the bony tip of the shoulder and joins through the lateral end of the clavicle. By complying with alengthy the clavicle, you deserve to palpate out to the bony tip of the shoulder, and from tbelow, you have the right to relocate back across your posterior shoulder to follow the ridge of the scapula. Move your shoulder about and also feel exactly how the clavicle and scapula move together as a unit. Both of these bones serve as essential attachment sites for muscles that aid via activities of the shoulder and arm.

The appropriate and also left pectoral girdles are not joined to each various other, allowing each to operate separately. In addition, the clavicle of each pectoral girdle is anchored to the axial skeleton by a solitary, highly mobile joint. This allows for the comprehensive mobility of the whole pectoral girdle, which in turn boosts motions of the shoulder and top limb.


Clavicle

The clavicle is the just lengthy bone that lies in a horizontal place in the body (watch (Figure)). The clavicle has a number of vital features. First, anchored by muscles from over, it serves as a strut that exoften tends laterally to assistance the scapula. This consequently holds the shoulder joint superiorly and also laterally from the body trunk, permitting for maximal flexibility of motion for the upper limb. The clavicle additionally transmits pressures acting on the top limb to the sternum and also axial skeleton. Finally, it serves to defend the underlying nerves and blood vessels as they pass in between the trunk of the body and the top limb.

The clavicle has actually 3 regions: the medial finish, the lateral finish, and also the shaft. The medial finish, known as the sternal end of the clavicle, has a triangular shape and also articulates with the manubrium percent of the sternum. This forms the sternoclavicular joint, which is the just bony articulation between the pectoral girdle of the top limb and also the axial skeleton. This joint enables considerable mobility, permitting the clavicle and scapula to relocate in upward/downward and also anterior/posterior directions during shoulder motions. The sternoclavicular joint is indirectly sustained by the costoclavicular ligament (costo- = “rib”), which spans the sternal end of the clavicle and the underlying initially rib. The lateral or acromial end of the clavicle articulates via the acromion of the scapula, the portion of the scapula that develops the bony reminder of the shoulder. Tbelow are some sex distinctions in the morphology of the clavicle. In women, the clavicle has a tendency to be shorter, thinner, and also much less curved. In guys, the clavicle is heavier and also much longer, and also has actually a greater curvature and rougher surdeals with wbelow muscles connect, attributes that are even more pronounced in hands-on workers.

The clavicle is the most generally fractured bone in the body. Such breaks frequently happen bereason of the force exerted on the clavicle as soon as a person falls onto his or her outstretched arms, or once the lateral shoulder receives a strong blow. Due to the fact that the sternoclavicular joint is strong and also hardly ever dissituated, extreme force outcomes in the breaking of the clavicle, commonly between the middle and lateral portions of the bone. If the fracture is complete, the shoulder and lateral clavicle fragment will drop because of the weight of the top limb, leading to the perchild to support the sagging limb via their various other hand. Muscles acting across the shoulder will certainly also pull the shoulder and also lateral clavicle anteriorly and medially, bring about the clavicle pieces to override. The clavicle overlies many type of essential blood vessels and nerves for the upper limb, yet fortunately, as a result of the anterior displacement of a damaged clavicle, these structures are seldom impacted once the clavicle is fractured.


Scapula

The scapula is also component of the pectoral girdle and hence plays a vital function in anchoring the upper limb to the body. The scapula is situated on the posterior side of the shoulder. It is surrounded by muscles on both its anterior (deep) and also posterior (superficial) sides, and for this reason does not articulate through the ribs of the thoracic cage.

The scapula has several important landmarks ((Figure)). The 3 margins or boundaries of the scapula, named for their positions within the body, are the exceptional border of the scapula, the medial border of the scapula, and the lateral border of the scapula. The suprascapular notch is situated lateral to the midallude of the remarkable border. The corners of the triangular scapula, at either finish of the medial border, are the remarkable angle of the scapula, situated between the medial and also premium borders, and the inferior angle of the scapula, located between the medial and also lateral borders. The inferior angle is the the majority of inferior percentage of the scapula, and also is particularly vital bereason it serves as the attachment suggest for numerous effective muscles associated in shoulder and upper limb movements. The staying edge of the scapula, between the superior and lateral borders, is the area of the glenoid cavity (glenoid fossa). This shpermit depression articulates via the humerus bone of the arm to develop the glenohumeral joint (shoulder joint). The small bony bumps situated immediately above and also below the glenoid cavity are the supraglenoid tubercle and the infraglenoid tubercle, respectively. These administer attachments for muscles of the arm.


The isolated scapula is shown right here from its anterior (deep) side and also its posterior (superficial) side.


The scapula also has 2 prominent projections. Toward the lateral finish of the exceptional border, in between the suprascapular notch and glenoid cavity, is the hook-favor coracoid process (coracoid = “shaped choose a crow’s beak”). This process tasks anteriorly and curves laterally. At the shoulder, the coracoid procedure is located inferior to the lateral finish of the clavicle. It is anchored to the clavicle by a solid ligament, and also serves as the attachment website for muscles of the anterior chest and arm. On the posterior facet, the spine of the scapula is a long and also significant ridge that runs throughout its upper percent. Extfinishing laterally from the spine is a flattened and also broadened area called the acromion or acromial process. The acromion forms the bony reminder of the remarkable shoulder region and articulates via the lateral end of the clavicle, creating the acromioclavicular joint (watch (Figure)). Together, the clavicle, acromion, and spine of the scapula kind a V-shaped bony line that gives for the attachment of neck and also ago muscles that act on the shoulder, and also muscles that pass throughout the shoulder joint to act on the arm.

The scapula has 3 depressions, each of which is dubbed a fossa (plural = fossae). Two of these are discovered on the posterior scapula, above and below the scapular spine. Superior to the spine is the narrowhead supraspinous fossa, and inferior to the spine is the wide infraspinous fossa. The anterior (deep) surchallenge of the scapula forms the broad subscapular fossa. All of these fossae administer big surface areas for the attachment of muscles that cross the shoulder joint to act on the humerus.

The acromioclavicular joint transmits pressures from the upper limb to the clavicle. The ligaments about this joint are reasonably weak. A hard loss onto the elbow or outextended hand deserve to stretch or tear the acromioclavicular ligaments, leading to a moderate injury to the joint. However, the primary assistance for the acromioclavicular joint comes from a really solid ligament referred to as the coracoclavicular ligament (view (Figure)). This connective tissue band also anchors the coracoid procedure of the scapula to the inferior surface of the acromial end of the clavicle and hence offers vital indirect support for the acromioclavicular joint. Following a strong blow to the lateral shoulder, such as when a hoccrucial player is moved right into the boards, a finish disarea of the acromioclavicular joint have the right to result. In this case, the acromion is thrust under the acromial end of the clavicle, leading to ruptures of both the acromioclavicular and coracoclavicular ligaments. The scapula then separates from the clavicle, through the weight of the top limb pulling the shoulder downward. This displace injury of the acromioclavicular joint is known as a “shoulder separation” and also is common in contact sports such as hocessential, footsphere, or martial arts.


Chapter Review

The pectoral girdle, consisting of the clavicle and also the scapula, attaches each top limb to the axial skeleton. The clavicle is an anterior bone whose sternal finish articulates through the manubrium of the sternum at the sternoclavicular joint. The sternal end is additionally anchored to the first rib by the costoclavicular ligament. The acromial finish of the clavicle articulates through the acromion of the scapula at the acromioclavicular joint. This end is likewise anchored to the coracoid procedure of the scapula by the coracoclavicular ligament, which provides indirect assistance for the acromioclavicular joint. The clavicle supports the scapula, transmits the weight and pressures from the top limb to the body trunk, and protects the underlying nerves and blood vessels.

The scapula lies on the posterior aspect of the pectdental girdle. It mediates the attachment of the upper limb to the clavicle, and contributes to the formation of the glenohumeral (shoulder) joint. This triangular bone has actually 3 sides called the medial, lateral, and premium boundaries. The suprascapular notch is located on the remarkable border. The scapula additionally has three corners, two of which are the premium and inferior angles. The third edge is populated by the glenoid cavity. Posteriorly, the spine sepaprices the supraspinous and infraspinous fossae, and also then exoften tends laterally as the acromion. The subscapular fossa is situated on the anterior surconfront of the scapula. The coracoid procedure projects anteriorly, passing inferior to the lateral finish of the clavicle.


Which component of the clavicle articulates via the manubrium?

shaftsternal endacromial endcoracoid process

A shoulder separation outcomes from injury to the ________.

glenohumeral jointcostoclavicular jointacromioclavicular jointsternoclavicular joint

Which feature lies in between the spine and also superior border of the scapula?

suprascapular notchglenoid cavitysuperior anglesupraspinous fossa

What structure is an expansion of the spine of the scapula?

acromioncoracoid processsupraglenoid tubercleglenoid cavity

Name the short, hook-prefer bony process of the scapula that projects anteriorly.

acromial processclaviclecoracoid processglenoid fossa

C


Critical Thinking Questions


Describe the shape and palpable line developed by the clavicle and scapula.


The clavicle extends laterally across the anterior shoulder and also can be palpated alengthy its whole length. At its lateral finish, the clavicle articulates with the acromion of the scapula, which creates the bony guideline of the shoulder. The acromion is consistent via the spine of the scapula, which have the right to be palpated medially and also posteriorly along its size. Together, the clavicle, acromion, and also spine of the scapula form a V-shaped line that serves as a critical location for muscle attachment.


Discuss two feasible injuries of the pectdental girdle that might occur adhering to a strong blow to the shoulder or a difficult fall onto an outstretched hand also.

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A blow to the shoulder or falling onto an outextended hand passes solid pressures through the scapula to the clavicle and sternum. A difficult autumn may thus cause a fracture of the clavicle (damaged collarbone) or may injure the ligaments of the acromioclavicular joint. In a significant instance, the coracoclavicular ligament might likewise rupture, bring about complete displace of the acromioclavicular joint (a “shoulder separation”).


Glossary

acromial end of the claviclelateral finish of the clavicle that articulates via the acromion of the scapulaacromial processacromion of the scapulaacromioclavicular jointarticulation between the acromion of the scapula and the acromial end of the clavicleacromionflattened bony procedure that extends laterally from the scapular spine to create the bony pointer of the shoulderclaviclecollarbone; elongated bone that articulates via the manubrium of the sternum medially and also the acromion of the scapula laterallycoracoclavicular ligamentstrong band of connective tissue that anchors the coracoid process of the scapula to the lateral clavicle; provides crucial instraight support for the acromioclavicular jointcoracoid processshort, hook-like procedure that jobs anteriorly and laterally from the remarkable margin of the scapulacostoclavicular ligamentband of connective tproblem that unites the medial clavicle with the initially ribfossa(plural = fossae) shpermit depression on the surconfront of a boneglenohumeral jointshoulder joint; created by the articulation between the glenoid cavity of the scapula and also the head of the humerusglenoid cavity(additionally, glenoid fossa) shallow depression situated on the lateral scapula, between the exceptional and also lateral bordersinferior angle of the scapulainferior edge of the scapula located wbelow the medial and lateral borders meetinfraglenoid tuberclesmall bump or roughened area located on the lateral border of the scapula, near the inferior margin of the glenoid cavityinfraspinous fossabroad depression located on the posterior scapula, inferior to the spinelateral border of the scapuladiagonally oriented lateral margin of the scapulamedial border of the scapulaelongated, medial margin of the scapulapectoral girdleshoulder girdle; the collection of bones, consisting of the scapula and also clavicle, which attaches each upper limb to the axial skeletonscapulashoulder blade bone situated on the posterior side of the shoulderspine of the scapulasignificant ridge passing mediolaterally throughout the top portion of the posterior scapular surfacesternal finish of the claviclemedial end of the clavicle that articulates through the manubrium of the sternumsternoclavicular jointarticulation between the manubrium of the sternum and also the sternal end of the clavicle; forms the just bony attachment between the pectoral girdle of the top limb and the axial skeletonsubscapular fossawide depression situated on the anterior (deep) surface of the scapulapremium angle of the scapulacorner of the scapula between the exceptional and also medial boundaries of the scapulasuperior border of the scapulapremium margin of the scapulasupraglenoid tuberclesmall bump located at the superior margin of the glenoid cavitysuprascapular notchlittle notch situated along the remarkable border of the scapula, medial to the coracoid processsupraspinous fossanarrowhead depression located on the posterior scapula, exceptional to the spine