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 with the axial skeleton ((Figure)). The bones that attach each upper limb come the axial skeleton type the pectoral girdle (shoulder girdle). This consists of two bones, the scapula and also clavicle ((Figure)). The clavicle (collarbone) is an S-shaped bone located on the anterior next of the shoulder. That is attached on its 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. Girlfriend can easily palpate, or feel with your fingers, the entire length of your clavicle.

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The axial skeleton forms the central axis the the body and consists that 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 skeletal of the hands and also feet.


The scapula (shoulder blade) lies top top the posterior aspect of the shoulder. That is sustained by the clavicle, which also articulates v the humerus (arm bone) to type the shoulder joint. The scapula is a flat, triangular-shaped bone with a significant ridge running across its posterior surface. This ridge extends the end laterally, wherein it creates the bony tip of the shoulder and joins through the lateral end of the clavicle. By following along the clavicle, you can palpate the end to the bony pointer of the shoulder, and also from there, you deserve to move back throughout your posterior shoulder to follow the ridge that the scapula. Move your shoulder around and feel exactly how the clavicle and scapula relocate together as a unit. Both of these bones offer as essential attachment sites for muscles that help with movements of the shoulder and also arm.

The right and also left pectoral girdles room not join to each other, enabling each to run independently. In addition, the clavicle of each pectoral girdle is anchored come the axial skeleton through a single, extremely mobile joint. This allows for the considerable mobility of the whole pectoral girdle, i m sorry in turn enhances movements of the shoulder and also upper limb.


Clavicle

The clavicle is the only long bone the lies in a horizontal place in the human body (see (Figure)). The clavicle has several necessary functions. First, anchored by muscles from above, the serves as a strut the extends laterally to assistance the scapula. This in turn holds the shoulder share superiorly and laterally native the body trunk, permitting for maximal flexibility of activity for the top limb. The clavicle additionally transmits forces acting ~ above the upper limb to the sternum and axial skeleton. Finally, it serves to defend the underlying nerves and also blood vessels as they pass between the stems of the body and also the upper limb.

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

The clavicle is the most commonly fractured bone in the body. Such breaks often occur since of the force exerted on the clavicle as soon as a person drops onto his or her outstretched arms, or once the lateral shoulder obtain a solid blow. Due to the fact that the sternoclavicular joint is strong and rarely dislocated, extreme force outcomes in the break 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 as result of the load of the top limb, leading to the human to support the sagging limb with their other hand. Muscle acting throughout the shoulder will likewise pull the shoulder and also lateral clavicle anteriorly and medially, causing the clavicle fragments to override. The clavicle overlies plenty of important blood vessels and also nerves for the top limb, yet fortunately, as result of the anterior displacement that a damaged clavicle, this structures space rarely affected when the clavicle is fractured.


Scapula

The scapula is also part of the pectoral girdle and thus plays an important role in anchoring the top limb to the body. The scapula is located on the posterior next of the shoulder. It is surrounded by muscles on both its anterior (deep) and also posterior (superficial) sides, and thus does no articulate v the ribs that the thoracic cage.

The scapula has several vital landmarks ((Figure)). The 3 margins or boundaries of the scapula, named for your positions in ~ the body, space the premium border that the scapula, the medial border of the scapula, and the lateral border that the scapula. The suprascapular notch is located lateral to the midpoint of the premium border. The corners that the triangle scapula, at either finish of the medial border, are the exceptional angle the the scapula, located in between the medial and superior borders, and also the inferior angle of the scapula, located in between the medial and lateral borders. The inferior angle is the many inferior portion of the scapula, and also is specifically important since it serves together the attachment point for several powerful muscles associated in shoulder and also upper limb movements. The remaining edge of the scapula, in between the superior and lateral borders, is the ar of the glenoid cavity (glenoid fossa). This shallow depression articulates with the humerus bone of the eight to kind the glenohumeral share (shoulder joint). The little bony bumps situated immediately above and listed below the glenoid cavity are the supraglenoid tubercle and also the infraglenoid tubercle, respectively. These carry out attachments for muscles that the arm.


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


The scapula also has two prominent projections. Toward the lateral finish of the superior border, in between the suprascapular notch and also glenoid cavity, is the hook-like coracoid procedure (coracoid = “shaped like a crow’s beak”). This procedure projects anteriorly and also curves laterally. At the shoulder, the coracoid procedure is located inferior come the lateral end of the clavicle. The is anchored to the clavicle by a solid ligament, and serves together the attachment site for muscle of the anterior chest and also arm. ~ above the posterior aspect, the spine of the scapula is a long and prominent ridge the runs throughout its upper portion. Extending laterally native the spine is a flattened and also expanded an ar called the acromion or acromial process. The acromion forms the bony tip of the superior shoulder an ar and articulates v the lateral end of the clavicle, developing the acromioclavicular joint (see (Figure)). Together, the clavicle, acromion, and also spine of the scapula kind a V-shaped bony heat that provides for the attachments of neck and back muscles the act on the shoulder, as well as muscles the pass throughout the shoulder share to plot on the arm.

The scapula has actually three depressions, each of i m sorry is called a fossa (plural = fossae). Two of these are discovered on the posterior scapula, over and below the scapular spine. Exceptional to the spine is the narrow supraspinous fossa, and inferior to the spine is the vast infraspinous fossa. The anterior (deep) surface of the scapula creates the wide subscapular fossa. All of these fossae provide large surface locations for the attachments of muscles the cross the shoulder share to action on the humerus.

The acromioclavicular share transmits forces from the top limb to the clavicle. The ligaments about this share are relatively weak. A hard fall onto the elbow or outstretched hand can stretch or tear the acromioclavicular ligaments, causing a center injury to the joint. However, the major support because that the acromioclavicular joint originates from a very strong ligament referred to as the coracoclavicular ligament (see (Figure)). This connective tissue band anchors the coracoid process of the scapula come the inferior surface ar of the acromial finish of the clavicle and also thus provides crucial indirect assistance for the acromioclavicular joint. Adhering to a strong blow come the lateral shoulder, together as when a hockey player is driven right into the boards, a complete dislocation of the acromioclavicular joint deserve to result. In this case, the acromion is thrust under the acromial end of the clavicle, leading to ruptures that both the acromioclavicular and also coracoclavicular ligaments. The scapula climate separates native the clavicle, with the load of the top limb pulling the shoulder downward. This dislocation injury the the acromioclavicular joint is recognized as a “shoulder separation” and is typical in call sports such together hockey, football, or martial arts.


Chapter Review

The pectoral girdle, consisting of the clavicle and also the scapula, attaches each top limb come the axial skeleton. The clavicle is one anterior bone who sternal finish articulates through the manubrium that the sternum in ~ the sternoclavicular joint. The sternal finish is additionally anchored to the very first rib by the costoclavicular ligament. The acromial end of the clavicle articulates with the acromion of the scapula in ~ the acromioclavicular joint. This finish is additionally anchored come the coracoid procedure 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 native the top limb come the human body trunk, and also protects the basic nerves and also blood vessels.

The scapula lies ~ above the posterior facet of the pectoral girdle. It mediates the attachment of the top limb to the clavicle, and contributes to the development of the glenohumeral (shoulder) joint. This triangle bone has actually three sides dubbed the medial, lateral, and also superior borders. The suprascapular notch is situated on the superior border. The scapula likewise has 3 corners, two of which room the superior and inferior angles. The third corner is inhabited by the glenoid cavity. Posteriorly, the spine separates the supraspinous and infraspinous fossae, and also then extends laterally as the acromion. The subscapular fossa is located on the anterior surface ar of the scapula. The coracoid process projects anteriorly, passing inferior to the lateral end of the clavicle.


Which component of the clavicle articulates through the manubrium?

shaftsternal endacromial endcoracoid process

A shoulder separation outcomes from injury to the ________.

glenohumeral jointcostoclavicular jointacromioclavicular jointsternoclavicular joint

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

suprascapular notchglenoid cavitysuperior anglesupraspinous fossa

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

acromioncoracoid processsupraglenoid tubercleglenoid cavity

Name the short, hook-like bony procedure of the scapula that tasks anteriorly.

acromial processclaviclecoracoid processglenoid fossa

C


Critical reasoning Questions


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


The clavicle expand laterally across the anterior shoulder and also can it is in palpated along its entire length. In ~ its lateral end, the clavicle articulates through the acromion of the scapula, which forms the bony guideline of the shoulder. The acromion is consistent with the spine that the scapula, which can be palpated medially and posteriorly follow me its length. Together, the clavicle, acromion, and spine the the scapula form a V-shaped line that serves as critical area because that muscle attachment.


Discuss two feasible injuries of the pectoral girdle that may occur adhering to a solid blow come the shoulder or a hard autumn onto one outstretched hand.

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A blow to the shoulder or falling onto an outstretched hand passes solid forces with the scapula to the clavicle and also sternum. A hard autumn may thus reason a fracture the the clavicle (broken collarbone) or may injure the ligaments that the acromioclavicular joint. In a severe case, the coracoclavicular ligament may also rupture, resulting in complete dislocation that the acromioclavicular share (a “shoulder separation”).


Glossary

acromial end of the claviclelateral end of the clavicle the articulates v the acromion of the scapulaacromial processacromion the the scapulaacromioclavicular jointarticulation between the acromion the the scapula and also the acromial end of the clavicleacromionflattened bony process that extends laterally native the scapular spine to type the bony guideline of the shoulderclaviclecollarbone; elongated bone that articulates v the manubrium the the sternum medially and also the acromion that the scapula laterallycoracoclavicular ligamentstrong band of connective tissue that anchors the coracoid process of the scapula to the lateral clavicle; provides vital indirect support for the acromioclavicular jointcoracoid processshort, hook-like procedure that tasks anteriorly and laterally native the remarkable margin that the scapulacostoclavicular ligamentband the connective tissue that hold together the medial clavicle with the first ribfossa(plural = fossae) shallow depression on the surface of a boneglenohumeral jointshoulder joint; formed by the articulation between the glenoid cavity of the scapula and also the head of the humerusglenoid cavity(also, glenoid fossa) shallow depression located on the lateral scapula, between the superior and lateral bordersinferior angle of the scapulainferior edge of the scapula located where the medial and lateral boundaries meetinfraglenoid tuberclesmall bang or roughened area located on the lateral border that the scapula, near the worse margin that the glenoid cavityinfraspinous fossabroad depression located on the posterior scapula, inferior to the spinelateral border that the scapuladiagonally oriented lateral margin of the scapulamedial border of the scapulaelongated, medial margin that the scapulapectoral girdleshoulder girdle; the set of bones, consists of the scapula and also clavicle, which attaches each top limb come the axial skeletonscapulashoulder blade bone located on the posterior next of the shoulderspine of the scapulaprominent ridge passing mediolaterally throughout the upper part of the posterior scapular surfacesternal finish of the claviclemedial end of the clavicle the articulates with the manubrium that the sternumsternoclavicular jointarticulation in between the manubrium that the sternum and also the sternal finish of the clavicle; creates the only bony attachment in between the pectoral girdle that the top limb and also the axial skeletonsubscapular fossabroad depression situated on the anterior (deep) surface ar of the scapulasuperior edge of the scapulacorner of the scapula between the superior and medial boundaries of the scapulasuperior border of the scapulasuperior margin that the scapulasupraglenoid tuberclesmall bump situated at the superior margin of the glenoid cavitysuprascapular notchsmall notch situated along the superior border the the scapula, medial to the coracoid processsupraspinous fossanarrow depression located on the posterior scapula, superior to the spine