Thorax Ribs and Sternum

Bony Thorax Include Thoracic vertebrae dorsally Ribs laterally Sternum and costal cartilage anteriorly Function Secure rib to sternum Protective cage around vital organs Supports shoulder girdles and upper limbs Provides attachment points for muscles of back, chest, and shoulder Intercostal spaces provide attachment for intercostal muscles that lift and depresses chest during breathing

Sternum Lies anterior midline of thorax Resembles knife blade, flat, about 15 cm (6in) long Made from 3 fused bones Manubrium (superior) clavicular notches articulates with clavicles and first two pairs of ribs --Body (midline) forms the bulk of sternum articulates with second to seventh rib Xiphoid process (inferior) Attachment site for abdominal muscles

Ribs 12 Pair in males and females Each rib articulate with both the body and the transverse process of its corresponding thoracic vertebra From vertebral attachment, rib curve outward, then forward and downward

True Rib 1st 7 pairs Join costal cartilage anteriorly Connect directly to sternum

False rib Last 5 pairs of ribs attach indirectly to sternum Last two pairs of false ribs called floaters because they do not attach to sternum at all