Describe the bones of the pectoral girdle, and also describe exactly how the girdle hold together the upper limbs through the axial skeleton

including the unique features and duty of each bone and also joint

 The skeleton that connect each upper limb to the axial skeleton type the pectoral girdle (shoulder girdle). This is composed of 2 bones, the scapula and clavicle (Figure 8.1.1). The clavicle (collarbone) is an S-shaped bone situated on the anterior side of the shoulder. It is attached on that medial end 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 above the shoulder joint. Girlfriend can easily palpate, or feel v your fingers, the entire length of your clavicle.

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Figure 8.1.1 – Pectoral Girdle: The pectoral girdle consists of the clavicle and the scapula, which offer to connect the top limb come the sternum of the axial skeleton.

The scapula (shoulder blade) lies top top the posterior element of the shoulder. It articulates through the humerus (arm bone) to type the shoulder joint (the glenohumeral joint). The scapula is a flat, triangular-shaped bone with a influential ridge running across its posterior surface. This ridge extends out laterally, where it forms the bony pointer of the shoulder and joins with the lateral finish of the clavicle. By adhering to along the clavicle, you deserve to palpate out to the bony guideline of the shoulder, and also from there, you deserve to move back across your posterior shoulder to monitor the ridge that the scapula. Relocate your shoulder around and also feel exactly how the clavicle and also scapula move together as a unit. Both of this bones serve as vital attachment sites for muscles that assist with motions of the shoulder and also 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 come the axial skeleton by a single, very mobile joint (the sternoclavicular joint). This permits for the extensive mobility of the entire pectoral girdle, i beg your pardon in turn enhances movements of the shoulder and also upper limb.

Clavicle

The clavicle is the only lengthy bone that lies in a horizontal place in the human body (see number 8.1.1). The clavicle has actually several essential functions. First, anchored by muscle from above, the serves together a strut the extends laterally to support the scapula. This subsequently holds the shoulder share superiorly and also laterally from the body trunk, enabling for maximal liberty of movement for the upper limb. The clavicle likewise transmits pressures acting top top the top limb come the sternum and also axial skeleton. Finally, it serves to protect the basic nerves and blood vessels as they pass in between the stems of the body and the upper limb.

The clavicle has actually three regions: the medial end, the lateral end, and the shaft. The medial end, known as the sternal end of the clavicle, has a triangle shape and articulates v the manubrium portion of the sternum. This develops the sternoclavicular joint, which is the just bony articulation in between the pectoral girdle that the upper limb and the axial skeleton. This joint permits considerable mobility, allowing the clavicle and scapula to move in upward/downward and anterior/posterior directions during 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 the underlying an initial rib. The lateral or acromial end of the clavicle articulates with the acromion of the scapula, the portion of the scapula that creates the bony reminder of the shoulder. There are some sex distinctions in the morphology of the clavicle. In women, the clavicle tends to be shorter, thinner, and also less curved. In men, the clavicle is heavier and also longer, and also has a better curvature and also rougher surfaces whereby muscles attach.

The clavicle is the many commonly broken bone in the body. Such breaks frequently occur because of the force exerted top top the clavicle when a person drops onto his or her outstretched arm, or once the lateral shoulder receives a solid blow. Since the sternoclavicular share is solid and rarely dislocated, too much force outcomes in the breaking of the clavicle, usually between the middle and lateral parts of the bone. If the fracture is complete, the shoulder and also lateral clavicle fragment will certainly drop as result of the weight of the upper limb, bring about the human to assistance the sagging limb v their other hand. Muscles acting across the shoulder will also pull the shoulder and lateral clavicle anteriorly and medially, bring about the clavicle pieces to overlap. The clavicle overlies numerous important blood vessels and nerves because that the top limb, yet fortunately, as result of the anterior displacement that a damaged 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 an essential role in anchoring the upper limb to the body. The scapula is situated on the posterior next of the shoulder. It is surrounded by muscles on both that is anterior (deep) and also posterior (superficial) sides, and also it walk not directly articulate v the ribs of the thoracic cage.

The scapula has several essential landmarks (Figure 8.1.2). The 3 margins or boundaries of the scapula, called for your positions in ~ the body, space the superior border the the scapula, the medial border the the scapula, and also the lateral border the the scapula. The suprascapular notch is situated lateral come the midpoint that the remarkable border. The corners that the triangle scapula, in ~ either end of the medial border, space the superior 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 lateral borders. The inferior angle is the most inferior portion of the scapula, and is specifically important due to the fact that it serves as the attachment allude for several powerful muscles connected in shoulder and also upper body movements. The remaining edge of the scapula, in between the superior and also lateral borders, is the ar of the glenoid cavity (glenoid fossa). This shallow depression articulates through the humerus bone that the eight to form the glenohumeral joint (shoulder joint, watch Chapter 9). The little bony bumps located immediately above and below the glenoid cavity space the supraglenoid tubercle and the infraglenoid tubercle, respectively. These provide attachments for muscles that the arm.

Figure 8.1.2 – Scapula: The diverted scapula is shown here indigenous its anterior (deep) side, lateral side and its posterior (superficial) side.

The scapula likewise has two prominent projections. Towards the lateral finish of the premium border, in between the suprascapular notch and glenoid cavity, is the hook-like coracoid process (coracoid = “shaped choose a crow’s beak”). This procedure projects anteriorly and curves laterally. At the shoulder, the coracoid procedure is situated inferior come the lateral end of the clavicle. The is anchored to the clavicle by a solid ligament, and also serves together the attachment website for muscles of the anterior chest and arm. ~ above the posterior aspect, the spine the the scapula is a long and also prominent ridge that runs across its upper portion. Prolonging laterally indigenous the spine is a flattened and expanded an ar called the acromion or acromial process. The acromion develops the bony tip of the premium shoulder an ar and articulates with the lateral finish of the clavicle, developing the acromioclavicular joint (see number 8.1.1). When visualized native above, the clavicle, acromion, and spine of the scapula type a V-shaped bony heat that provides for the attachments of neck and ago muscles that act top top the shoulder, and also muscles the pass across the shoulder joint to act on the arm.

The scapula has actually three depressions, each of which is dubbed a fossa (plural = fossae). 2 of this are discovered on the posterior scapula, over and listed below the scapular spine. Premium to the spine is the small supraspinous fossa, and inferior to the spine is the wide infraspinous fossa. The anterior (deep) surface of the scapula creates the broad subscapular fossa. All of these fossae provide huge surface areas for the attachments of muscles that cross the shoulder share to plot on the humerus.

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The acromioclavicular share transmits forces from the top limb come the clavicle. The ligaments approximately this share are relatively weak. A hard fall onto the elbow or outstretched hand have the right to stretch or tear the acromioclavicular ligaments, bring about a center injury come the joint. However, the primary support because that the acromioclavicular joint comes from a very strong ligament called the coracoclavicular ligament (see figure 8.1.1). This connective tissue band anchors the coracoid procedure of the scapula come the inferior surface of the acromial finish of the clavicle and thus provides important indirect support for the acromioclavicular joint. Complying with a strong blow to the lateral shoulder, such as once a hockey player is driven into the boards, a finish dislocation of the acromioclavicular joint have the right to result. In this case, the acromion is thrust under the acromial finish of the clavicle, causing ruptures of both the acromioclavicular and also coracoclavicular ligaments. The scapula climate separates indigenous the clavicle, with the load of the upper limb pulling the shoulder downward. This dislocation injury that the acromioclavicular share is well-known as a “shoulder separation” and is usual following a bicycle accident, or during call sports.