Describe the bones that kind the pectoral girdleList the attributes of the pectoral girdle

The appendicular skeleton includes all of the limb bones, to add the bones that unite each limb v the axial skeleton ((Figure)). The skeletal that affix each top limb come the axial skeleton form the pectoral girdle (shoulder girdle). This consists of two bones, the scapula and clavicle ((Figure)). The clavicle (collarbone) is one S-shaped bone situated on the anterior side of the shoulder. It is fastened on that is medial finish to the sternum the the thoracic cage, i m sorry is component of the axial skeleton. The lateral finish of the clavicle articulates (joins) through the scapula just over the shoulder joint. Friend can easily palpate, or feel with your fingers, the whole length of your clavicle.

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


The scapula (shoulder blade) lies top top the posterior facet of the shoulder. The is supported by the clavicle, which also articulates through the humerus (arm bone) to form the shoulder joint. The scapula is a flat, triangular-shaped bone with a influential ridge running across its posterior surface. This ridge extends out laterally, wherein it forms the bony guideline of the shoulder and also joins through the lateral finish of the clavicle. By complying with along the clavicle, you deserve to palpate the end to the bony reminder of the shoulder, and also from there, you deserve to move back throughout your posterior shoulder to monitor the ridge that the scapula. Move your shoulder around and also feel how the clavicle and also scapula relocate together as a unit. Both of these bones serve as important attachment sites because that muscles that help with movements of the shoulder and arm.

The right and also left pectoral girdles room not joined to every other, enabling each to run independently. In addition, the clavicle of every pectoral girdle is anchored to the axial skeleton by a single, highly mobile joint. This enables for the substantial mobility the the whole pectoral girdle, which in turn boosts movements of the shoulder and also upper limb.


Clavicle

The clavicle is the only lengthy bone the lies in a horizontal position in the human body (see (Figure)). The clavicle has actually several essential functions. First, anchored by muscle from above, that serves together a strut the extends laterally to support the scapula. This subsequently holds the shoulder joint superiorly and also laterally native the body trunk, allowing for maximal liberty of motion for the upper limb. The clavicle additionally transmits forces acting top top the upper limb to the sternum and also axial skeleton. Finally, it offer to defend the underlying nerves and blood vessels together they pass in between the tribe of the body and the top limb.

The clavicle has three regions: the medial end, the lateral end, and the shaft. The medial end, known as the sternal finish of the clavicle, has a triangle shape and also articulates through the manubrium part of the sternum. This develops the sternoclavicular joint, i beg your pardon is the just bony articulation in between the pectoral girdle the the top limb and the axial skeleton. This joint permits considerable mobility, allowing the clavicle and scapula to relocate in upward/downward and anterior/posterior directions throughout shoulder movements. The sternoclavicular joint is indirectly supported by the costoclavicular ligament (costo- = “rib”), i beg your pardon spans the sternal end of the clavicle and also the underlying first rib. The lateral or acromial finish of the clavicle articulates v the acromion that the scapula, the section of the scapula that creates the bony tip of the shoulder. There room some sex distinctions in the morphology the the clavicle. In women, the clavicle has tendency to be shorter, thinner, and less curved. In men, the clavicle is heavier and also longer, and has a higher curvature and also rougher surfaces whereby muscles attach, features that are more pronounced in manual workers.

The clavicle is the many commonly fractured bone in the body. Together breaks often occur since of the force exerted top top the clavicle once a person drops onto his or her outstretched arms, or as soon as the lateral shoulder receives a solid blow. Because the sternoclavicular joint is solid and hardly ever dislocated, too much force results in the breaking of the clavicle, usually in between the middle and also lateral sections of the bone. If the fracture is complete, the shoulder and lateral clavicle fragment will drop due to the load of the upper limb, bring about the person to assistance the sagging limb through their other hand. Muscles acting throughout the shoulder will also pull the shoulder and lateral clavicle anteriorly and medially, causing the clavicle pieces to override. The clavicle overlies countless important blood vessels and nerves for the upper limb, yet fortunately, as result of the anterior displacement that a broken clavicle, this structures room rarely influenced when the clavicle is fractured.


Scapula

The scapula is also part of the pectoral girdle and also thus plays crucial role in anchoring the upper limb come the body. The scapula is situated on the posterior side of the shoulder. The is surrounding by muscles on both that anterior (deep) and also posterior (superficial) sides, and also thus does no articulate with the ribs that the thoracic cage.

The scapula has several necessary landmarks ((Figure)). The three margins or boundaries of the scapula, named for their positions in ~ the body, room the superior border of the scapula, the medial border that the scapula, and the lateral border that the scapula. The suprascapular notch is situated lateral to the midpoint the the superior border. The corners of the triangle scapula, in ~ either end of the medial border, room the premium angle of the scapula, located between the medial and also superior borders, and the inferior angle of the scapula, located in between the medial and also lateral borders. The inferior edge is the many inferior part of the scapula, and also is specifically important due to the fact that it serves together the attachment point for several an effective muscles involved in shoulder and also upper limb movements. The remaining edge of the scapula, in between the superior and also lateral borders, is the place of the glenoid cavity (glenoid fossa). This shallow depression articulates with the humerus bone of the eight to type the glenohumeral joint (shoulder joint). The small bony bumps located immediately over and below the glenoid cavity are the supraglenoid tubercle and the infraglenoid tubercle, respectively. These provide attachments because that muscles the the arm.


The isolated scapula is presented here indigenous its anterior (deep) side and its posterior (superficial) side.


The scapula likewise has two prominent projections. Towards the lateral finish of the exceptional border, between the suprascapular notch and glenoid cavity, is the hook-like coracoid procedure (coracoid = “shaped favor a crow’s beak”). This procedure projects anteriorly and also curves laterally. In ~ the shoulder, the coracoid process is located inferior to the lateral end of the clavicle. It is anchored to the clavicle by a solid ligament, and serves together the attachment site for muscle of the anterior chest and arm. Top top the posterior aspect, the spine of the scapula is a long and prominent ridge the runs throughout its top portion. Expanding laterally native the spine is a flattened and expanded an ar called the acromion or acromial process. The acromion forms the bony pointer of the exceptional shoulder region and articulates v the lateral end of the clavicle, forming the acromioclavicular joint (see (Figure)). Together, the clavicle, acromion, and spine that the scapula kind a V-shaped bony heat that offers for the attachment of neck and earlier muscles the act top top the shoulder, as well as muscles the pass throughout the shoulder share to plot on the arm.

The scapula has three depressions, each of which is referred to as a fossa (plural = fossae). 2 of these are uncovered on the posterior scapula, over and listed below the scapular spine. Remarkable to the spine is the narrow supraspinous fossa, and inferior to the spine is the large infraspinous fossa. The anterior (deep) surface of the scapula develops the vast subscapular fossa. All of these fossae provide large surface areas for the attachment of muscles that cross the shoulder share to plot on the humerus.

The acromioclavicular share transmits forces from the top limb come the clavicle. The ligaments approximately this joint are relatively weak. A hard loss onto the elbow or outstretched hand deserve to stretch or tear the acromioclavicular ligaments, leading to a moderate injury to the joint. However, the main support because that the acromioclavicular joint originates from a very solid ligament referred to as the coracoclavicular ligament (see (Figure)). This connective organization band anchors the coracoid procedure of the scapula come the inferior surface of the acromial end of the clavicle and also thus provides important indirect support for the acromioclavicular joint. Complying with a solid blow to the lateral shoulder, together as once a hockey player is driven into the boards, a finish dislocation that the acromioclavicular joint deserve to result. In this case, the acromion is thrust under the acromial finish of the clavicle, leading to ruptures of both the acromioclavicular and also coracoclavicular ligaments. The scapula climate separates from the clavicle, v the weight of the top limb pulling the shoulder downward. This dislocation injury that the acromioclavicular joint is well-known as a “shoulder separation” and also is usual in contact sports such as hockey, football, or martial arts.


Chapter Review

The pectoral girdle, consists of the clavicle and the scapula, attaches each top limb to the axial skeleton. The clavicle is one anterior bone who sternal finish articulates v the manubrium the the sternum at the sternoclavicular joint. The sternal finish is also anchored come the first rib by the costoclavicular ligament. The acromial end of the clavicle articulates v the acromion that the scapula at the acromioclavicular joint. This end is likewise anchored come the coracoid process of the scapula by the coracoclavicular ligament, which provides indirect support for the acromioclavicular joint. The clavicle supports the scapula, transmits the weight and forces from the top limb to the body trunk, and also protects the basic nerves and blood vessels.

The scapula lies ~ above the posterior facet of the pectoral girdle. That mediates the attachment of the top limb to the clavicle, and also contributes to the formation of the glenohumeral (shoulder) joint. This triangular bone has three sides called the medial, lateral, and also superior borders. The suprascapular notch is located on the remarkable border. The scapula additionally has three corners, 2 of which space the superior and also inferior angles. The third corner is lived in by the glenoid cavity. Posteriorly, the spine separates the supraspinous and also infraspinous fossae, and also then extends laterally as the acromion. The subscapular fossa is situated on the anterior surface of the scapula. The coracoid procedure projects anteriorly, passing worse to the lateral finish of the clavicle.


Which component of the clavicle articulates with the manubrium?

shaftsternal endacromial endcoracoid process

A shoulder separation results from injury come the ________.

glenohumeral jointcostoclavicular jointacromioclavicular jointsternoclavicular joint

Which function lies between the spine and superior border of the scapula?

suprascapular notchglenoid cavitysuperior anglesupraspinous fossa

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

acromioncoracoid processsupraglenoid tubercleglenoid cavity

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

acromial processclaviclecoracoid processglenoid fossa

C


Critical reasoning Questions


Describe the shape and also palpable line created by the clavicle and also scapula.


The clavicle expand laterally across the anterior shoulder and can be palpated along its entire length. In ~ its lateral end, the clavicle articulates through the acromion that the scapula, which forms the bony tip of the shoulder. The acromion is constant with the spine of the scapula, which have the right to be palpated medially and posteriorly along its length. Together, the clavicle, acromion, and also spine the the scapula kind a V-shaped line that serves as vital area for muscle attachment.


Discuss two possible injuries of the pectoral girdle that may occur complying with a strong blow come the shoulder or a hard loss onto one outstretched hand.

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A blow to the shoulder or falling top top an outstretched hand passes solid forces v the scapula to the clavicle and also sternum. A hard fall may thus cause a fracture of the clavicle (broken collarbone) or may injure the ligaments the the acromioclavicular joint. In a significant case, the coracoclavicular ligament may also rupture, result in finish dislocation the the acromioclavicular share (a “shoulder separation”).


Glossary

acromial end of the claviclelateral end of the clavicle that articulates with the acromion that the scapulaacromial processacromion the the scapulaacromioclavicular jointarticulation between the acromion the the scapula and the acromial end of the clavicleacromionflattened bony process that extends laterally indigenous the scapular spine to type the bony reminder of the shoulderclaviclecollarbone; elongated bone the articulates with the manubrium that the sternum medially and the acromion of the scapula laterallycoracoclavicular ligamentstrong band of connective tissue that anchors the coracoid procedure of the scapula come the lateral clavicle; provides important indirect assistance for the acromioclavicular jointcoracoid processshort, hook-like process that jobs anteriorly and laterally from the superior margin of the scapulacostoclavicular ligamentband the connective organization that unites the medial clavicle through the an initial ribfossa(plural = fossae) shallow depression ~ above the surface ar of a boneglenohumeral jointshoulder joint; developed by the articulation in between the glenoid cavity that the scapula and also the head that the humerusglenoid cavity(also, glenoid fossa) shallow depression located on the lateral scapula, in between the superior and also lateral bordersinferior edge of the scapulainferior edge of the scapula located where the medial and also lateral borders meetinfraglenoid tuberclesmall bump or roughened area situated on the lateral border the the scapula, near the worse margin of the glenoid cavityinfraspinous fossabroad depression situated on the posterior scapula, inferior to the spinelateral border of the scapuladiagonally oriented lateral margin that the scapulamedial border that the scapulaelongated, medial margin of the scapulapectoral girdleshoulder girdle; the collection of bones, consists of the scapula and also clavicle, i m sorry attaches each upper limb to the axial skeletonscapulashoulder tongue bone situated on the posterior next of the shoulderspine that the scapulaprominent ridge happen mediolaterally across the upper section of the posterior scapular surfacesternal end of the claviclemedial finish of the clavicle the articulates v the manubrium that the sternumsternoclavicular jointarticulation in between the manubrium of the sternum and the sternal end of the clavicle; develops the just bony attachment between the pectoral girdle the the upper limb and the axial skeletonsubscapular fossabroad depression situated on the anterior (deep) surface of the scapulasuperior edge of the scapulacorner of the scapula between the superior and medial borders of the scapulasuperior border that the scapulasuperior margin that the scapulasupraglenoid tuberclesmall bump situated at the exceptional margin the the glenoid cavitysuprascapular notchsmall notch situated along the remarkable border that the scapula, medial come the coracoid processsupraspinous fossanarrow depression located on the posterior scapula, premium to the spine