Thoracic Cage and Pectoral Girdle

Thoracic Cage

The sternum, 12 pairs of ribs, and thoracic vertebrae

Form peripheral boundary of thoracic cavity

Protect the heart, lungs, and great blood vessels

Sternum

includes 3 portions

manubrium, body, xiphoid process

Manubrium

Superior Suprasternal Notch with lateral Clavicular Notches that articulate with clavicles

Sternum Body

Sternal Angle is the attachment site for the second set of ribs

Xiphoid Process

Site of attachment for some abdominal muscles

Composed of hyaline cartilage initially, it is generally ossified by age 40

Ribs

Includes 12 pairs of ribs and Costal Cartilages, made of hyaline cartilage which provides flexibility

Spaces between ribs are the Intercostal Spaces

True ribs and false ribs

True (Vertebrosternal) Ribs

ribs 1-7

Attach to the sternum via their own costal cartilage

False Ribs

ribs 8-12

Do not attach to the sternum directly

includes vertebrochondral ribs and floating (vertebral) ribs

Vertebrochondral ribs

ribs 8-10

Costal cartilages attach to the cartilage of rib 7 as the Costal Margin

Floating (Vertebral) Ribs

ribs 11-12

do not attach to the sternum

Structure of Ribs

– Rounded Head articulates with the bodies of thoracic vertebrae through Inferior and Superior Articular Facets

– The head connects laterally to a Neck, then a Tubercle, that articulates with the transverse process of the vertebra

– Rib curves at an Angle, into the Shaft (Body) with an internal costal groove for blood vessels and nerves

▪ Ribs 1–10 have square ends for costal cartilage

▪ Ribs 1 and 10–12 lack separate facets because they only attach to the body of 1 thoracic vertebra

▪ Floating ribs lack tubercles

Cardiopulmonary Resuscitation (CPR)

Life-saving technique administered when an individual’s heart has stopped functional contractions and/or breathing has stopped

CPR may restore circulation to the body by the application of repeated compressions to the chest over the sternum

Hands must be placed over the center of the sternum, and not over the xiphoid process, which may break and damage underlying organs, particularly the liver

CPR may still break the sternum and ribs, especially in elderly individuals with low bone mass

Pectoral Girdle

Consists of two bones, the Clavicle and Scapula, that support the upper limb

Clavicle

S-shaped bone

Medial Sternal End articulates with the manubrium forming the sternoclavicular joint

Lateral Acromial End articulates with the acromion process of the scapula forming the acromioclavicular joint

Conoid Tubercle is the site of ligament attachment

Functions like a brace for the upper limb so that it rests laterally to the trunk

Scapula

Sits on the posterosuperior rib cage

Body has Medial, Lateral, and Superior Borders and forms superior, inferior, and lateral angles

Coracoid Process sits over the Subscapular Fossa

Laterally, the Glenoid Cavity is visible

The posterior Spine separates the superior Supraspinous Fossa from the Infraspinous Fossa and terminates in the Acromion, which forms the acromioclavicular (AC) joint

– Injuries to the A C joint are common and are referred to as a separated shoulder