Artlabeling Activity Bones of the Appendicular Skeleton Part 1

The Appendicular Skeleton

The Pectoral Girdle

Learning Objectives

By the end of this section, y'all volition exist able to:

• Depict the bones that form the pectoral girdle
• List the functions of the pectoral girdle

The appendicular skeleton includes all of the limb bones, plus the bones that unite each limb with the axial skeleton ((Figure)). The bones that adhere each upper limb to the axial skeleton form the pectoral girdle (shoulder girdle). This consists 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 cease to the sternum of the thoracic cage, which is role of the axial skeleton. The lateral end of the clavicle articulates (joins) with the scapula just above the shoulder joint. You tin easily palpate, or feel with your fingers, the entire length of your clavicle.

Axial and Appendicular Skeletons

The axial skeleton forms the central axis of the body and consists of the skull, vertebral cavalcade, and thoracic cage. The appendicular skeleton consists of the pectoral and pelvic girdles, the limb basic, and the bones of the hands and feet.

Pectoral Girdle

The pectoral girdle consists of the clavicle and the scapula, which serve to adhere the upper limb to the sternum of the axial skeleton.

The scapula (shoulder blade) lies on the posterior attribute of the shoulder. It is supported past the clavicle, which also articulates with the humerus (arm os) to form the shoulder joint. The scapula is a apartment, triangular-shaped bone with a prominent ridge running across its posterior surface. This ridge extends out laterally, where information technology forms the bony tip of the shoulder and joins with the lateral end of the clavicle. By following forth the clavicle, y'all can palpate out to the bony tip of the shoulder, and from there, you lot can move dorsum across your posterior shoulder to follow the ridge of the scapula. Motility your shoulder around and experience how the clavicle and scapula move together as a unit. Both of these bones serve as of import attachment sites for muscles that aid with movements of the shoulder and arm.

The right and left pectoral girdles are not joined to each other, allowing each to operate independently. In addition, the clavicle of each pectoral girdle is anchored to the centric skeleton by a single, highly mobile articulation. This allows for the all-encompassing mobility of the entire pectoral girdle, which in turn enhances movements of the shoulder and upper limb.

Clavicle

The clavicle is the only long bone that lies in a horizontal position in the body (see (Figure)). The clavicle has several of import functions. Offset, anchored by muscles from to a higher place, it serves equally a strut that extends laterally to support the scapula. This in plough holds the shoulder articulation superiorly and laterally from the body torso, allowing for maximal freedom of motion for the upper limb. The clavicle also transmits forces acting on the upper limb to the sternum and axial skeleton. Finally, it serves to protect the underlying fretfulness and blood vessels as they pass betwixt the torso of the body and the upper limb.

The clavicle has three regions: the medial end, the lateral cease, and the shaft. The medial stop, known as the sternal end of the clavicle, has a triangular shape and articulates with the manubrium portion of the sternum. This forms the sternoclavicular joint, which is the only bony joint betwixt the pectoral girdle of the upper limb and the centric skeleton. This articulation allows considerable mobility, enabling the clavicle and scapula to move in upwardly/downward and anterior/posterior directions during shoulder movements. The sternoclavicular joint is indirectly supported past the costoclavicular ligament (costo- = "rib"), which spans the sternal end of the clavicle and the underlying first rib. The lateral or acromial cease of the clavicle articulates with the acromion of the scapula, the portion of the scapula that forms the bony tip of the shoulder. At that place are some sex differences in the morphology of the clavicle. In women, the clavicle tends to be shorter, thinner, and less curved. In men, the clavicle is heavier and longer, and has a greater curvature and rougher surfaces where muscles attach, features that are more pronounced in manual workers.

The clavicle is the most normally fractured os in the body. Such breaks often occur because of the force exerted on the clavicle when a person falls onto his or her outstretched arms, or when the lateral shoulder receives a stiff blow. Because the sternoclavicular joint is potent and rarely dislocated, excessive force results in the breaking of the clavicle, commonly between the middle and lateral portions of the bone. If the fracture is consummate, the shoulder and lateral clavicle fragment will drop due to the weight of the upper limb, causing the person to support the sagging limb with their other hand. Muscles acting across the shoulder volition too pull the shoulder and lateral clavicle anteriorly and medially, causing the clavicle fragments to override. The clavicle overlies many important blood vessels and fretfulness for the upper limb, only fortunately, due to the anterior displacement of a broken clavicle, these structures are 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 upper limb to the body. The scapula is located on the posterior side of the shoulder. Information technology is surrounded past muscles on both its anterior (deep) and posterior (superficial) sides, and thus does non clear with the ribs of the thoracic muzzle.

The scapula has several important landmarks ((Figure)). The three margins or borders of the scapula, named for their positions inside the torso, are the superior border of the scapula, the medial border of the scapula, and the lateral border of the scapula. The suprascapular notch is located lateral to the midpoint of the superior border. The corners of the triangular scapula, at either end of the medial border, are the superior angle of the scapula, located between the medial and superior borders, and the inferior angle of the scapula, located between the medial and lateral borders. The inferior angle is the most inferior portion of the scapula, and is especially important because it serves as the attachment signal for several powerful muscles involved in shoulder and upper limb movements. The remaining corner of the scapula, between the superior and lateral borders, is the location of the glenoid cavity (glenoid fossa). This shallow low articulates with the humerus bone of the arm to form the glenohumeral joint (shoulder articulation). The small bony bumps located immediately above and below the glenoid cavity are the supraglenoid tubercle and the infraglenoid tubercle, respectively. These provide attachments for muscles of the arm.

Scapula

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

The scapula as well has two prominent projections. Toward the lateral end of the superior border, betwixt the suprascapular notch and glenoid cavity, is the hook-like coracoid process (coracoid = "shaped like a crow's beak"). This process projects anteriorly and curves laterally. At the shoulder, the coracoid procedure is located inferior to the lateral end of the clavicle. It is anchored to the clavicle by a strong ligament, and serves as the zipper site for muscles of the anterior chest and arm. On the posterior aspect, the spine of the scapula is a long and prominent ridge that runs across its upper portion. Extending laterally from the spine is a flattened and expanded region called the acromion or acromial procedure. The acromion forms the bony tip of the superior shoulder region and articulates with the lateral finish of the clavicle, forming the acromioclavicular articulation (see (Effigy)). Together, the clavicle, acromion, and spine of the scapula form a Five-shaped bony line that provides for the attachment of neck and back muscles that act on the shoulder, as well as muscles that pass across the shoulder joint to act on the arm.

The scapula has three depressions, each of which is called a fossa (plural = fossae). Two of these are found on the posterior scapula, in a higher place and below the scapular spine. Superior to the spine is the narrow supraspinous fossa, and junior to the spine is the broad infraspinous fossa. The anterior (deep) surface of the scapula forms the broad subscapular fossa. All of these fossae provide large surface areas for the attachment of muscles that cantankerous the shoulder joint to deed on the humerus.

The acromioclavicular joint transmits forces from the upper limb to the clavicle. The ligaments effectually this articulation are relatively weak. A difficult fall onto the elbow or outstretched hand tin stretch or tear the acromioclavicular ligaments, resulting in a moderate injury to the articulation. Nevertheless, the main support for the acromioclavicular articulation comes from a very strong ligament called the coracoclavicular ligament (see (Effigy)). This connective tissue band anchors the coracoid process of the scapula to the junior surface of the acromial end of the clavicle and thus provides important indirect back up for the acromioclavicular articulation. Following a potent blow to the lateral shoulder, such as when a hockey player is driven into the boards, a complete dislocation of the acromioclavicular joint can outcome. In this example, the acromion is thrust under the acromial end of the clavicle, resulting in ruptures of both the acromioclavicular and coracoclavicular ligaments. The scapula then separates from the clavicle, with the weight of the upper limb pulling the shoulder downward. This dislocation injury of the acromioclavicular articulation is known as a "shoulder separation" and is common in contact sports such as hockey, football game, or martial arts.

Chapter Review

The pectoral girdle, consisting of the clavicle and the scapula, attaches each upper limb to the axial skeleton. The clavicle is an anterior bone whose sternal end articulates with the manubrium of the sternum at the sternoclavicular joint. The sternal end is too anchored to the get-go rib by the costoclavicular ligament. The acromial finish of the clavicle articulates with the acromion of the scapula at the acromioclavicular joint. This end is also anchored to the coracoid process of the scapula past the coracoclavicular ligament, which provides indirect support for the acromioclavicular joint. The clavicle supports the scapula, transmits the weight and forces from the upper limb to the body trunk, and protects the underlying fretfulness and blood vessels.

The scapula lies on the posterior aspect of the pectoral girdle. It mediates the attachment of the upper limb to the clavicle, and contributes to the germination of the glenohumeral (shoulder) joint. This triangular os has three sides called the medial, lateral, and superior borders. The suprascapular notch is located on the superior border. The scapula also has 3 corners, two of which are the superior and inferior angles. The tertiary corner is occupied by the glenoid crenel. Posteriorly, the spine separates the supraspinous and infraspinous fossae, and then extends laterally equally the acromion. The subscapular fossa is located on the anterior surface of the scapula. The coracoid procedure projects anteriorly, passing junior to the lateral cease of the clavicle.

Review Questions

Which part of the clavicle articulates with the manubrium?

1. shaft
2. sternal finish
3. acromial end
4. coracoid process

A shoulder separation results from injury to the ________.

1. glenohumeral joint
2. costoclavicular articulation
3. acromioclavicular articulation
4. sternoclavicular articulation

Which feature lies between the spine and superior edge of the scapula?

1. suprascapular notch
2. glenoid crenel
3. superior angle
4. supraspinous fossa

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

1. acromion
2. coracoid process
3. supraglenoid tubercle
4. glenoid cavity

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

1. acromial process
2. clavicle
3. coracoid process
4. glenoid fossa

Critical Thinking Questions

Draw the shape and palpable line formed by the clavicle and scapula.

The clavicle extends laterally across the anterior shoulder and can be palpated along its entire length. At its lateral end, the clavicle articulates with the acromion of the scapula, which forms the bony tip of the shoulder. The acromion is continuous with the spine of the scapula, which tin can be palpated medially and posteriorly along its length. Together, the clavicle, acromion, and spine of the scapula grade a 5-shaped line that serves as an important area for muscle attachment.

Hash out 2 possible injuries of the pectoral girdle that may occur following a strong blow to the shoulder or a hard fall onto an outstretched manus.

A blow to the shoulder or falling onto an outstretched hand passes potent forces through the scapula to the clavicle and sternum. A hard fall may thus cause a fracture of the clavicle (broken collarbone) or may injure the ligaments of the acromioclavicular articulation. In a severe example, the coracoclavicular ligament may likewise rupture, resulting in consummate dislocation of the acromioclavicular joint (a "shoulder separation").

Glossary

acromial finish of the clavicle

lateral end of the clavicle that articulates with the acromion of the scapula

acromial procedure

acromion of the scapula

acromioclavicular joint

articulation between the acromion of the scapula and the acromial end of the clavicle

acromion

flattened bony process that extends laterally from the scapular spine to grade the bony tip of the shoulder

clavicle

collarbone; elongated bone that articulates with the manubrium of the sternum medially and the acromion of the scapula laterally

coracoclavicular ligament

strong band of connective tissue that anchors the coracoid process of the scapula to the lateral clavicle; provides important indirect support for the acromioclavicular joint

coracoid procedure

brusque, claw-like procedure that projects anteriorly and laterally from the superior margin of the scapula

costoclavicular ligament

band of connective tissue that unites the medial clavicle with the commencement rib

fossa

(plural = fossae) shallow depression on the surface of a os

glenohumeral articulation

shoulder joint; formed by the articulation between the glenoid crenel of the scapula and the caput of the humerus

glenoid crenel

(as well, glenoid fossa) shallow depression located on the lateral scapula, between the superior and lateral borders

inferior angle of the scapula

inferior corner of the scapula located where the medial and lateral borders meet

infraglenoid tubercle

small crash-land or roughened surface area located on the lateral edge of the scapula, well-nigh the inferior margin of the glenoid cavity

infraspinous fossa

broad depression located on the posterior scapula, inferior to the spine

lateral edge of the scapula

diagonally oriented lateral margin of the scapula

medial border of the scapula

elongated, medial margin of the scapula

pectoral girdle

shoulder girdle; the fix of bones, consisting of the scapula and clavicle, which attaches each upper limb to the centric skeleton

scapula

shoulder blade bone located on the posterior side of the shoulder

spine of the scapula

prominent ridge passing mediolaterally across the upper portion of the posterior scapular surface

sternal end of the clavicle

medial cease of the clavicle that articulates with the manubrium of the sternum

sternoclavicular joint

articulation between the manubrium of the sternum and the sternal end of the clavicle; forms the but bony attachment betwixt the pectoral girdle of the upper limb and the axial skeleton

subscapular fossa

wide depression located on the anterior (deep) surface of the scapula

superior angle of the scapula

corner of the scapula between the superior and medial borders of the scapula

superior border of the scapula

superior margin of the scapula

supraglenoid tubercle

pocket-sized bump located at the superior margin of the glenoid cavity

suprascapular notch

small notch located along the superior edge of the scapula, medial to the coracoid process

supraspinous fossa

narrow depression located on the posterior scapula, superior to the spine

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Source: https://opentextbc.ca/anatomyandphysiologyopenstax/chapter/the-pectoral-girdle/

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