Surface Anatomy and Skeleton of the Thorax

Facts about rib

- first rib - highest, shortest, broadest, and most sharply curved rib; 1st rib is not palpable - head of a rib usually articulates with two vertebral bodies and their intervertebral disc 5th rib articulates with inferior articular facet of T4 and superior articular facet of T5 - 1st, 10th, 11th, and 12th ribs are exceptions to this rule—their heads articulate with only one vertebral body. - tubercle of a rib articulates with the transverse costal facet on the transverse process of the thoracic vertebra of the same number - costal cartilage is attached to the anterior end of each rib (contribute to the elasticity of the walls of the thorax)

Intercostal space

- interval between adjacent ribs - three layers of muscle fill the intercostal space in the living body and in the cadaver - superficial to deep, the three layers of muscle are external intercostal muscle, internal intercostal muscle, and innermost intercostals muscle - 11 intercostal spaces (fourth intercostals space is located between ribs 4 and 5)

Scapula

Acromion Coracoid process

Rib

Head Neck Tubercle Costal angle Shaft (body) Costal groove

Surface anatomy of the thorax

Jugular notch (suprasternal notch) T2 Clavicle Acromion of the scapula Manubrium T3-4 Sternal angle T4-5 Body of the sternum T5-9 Xiphoid process (approximately at the level of intercostal space 5) T9 Costal margin (ribs 7-10) Anterior axillary fold (lateral border of the pectoralis major muscle)

Sternum

Jugular notch (suprasternal notch) T2 Manubrium (L. manubrium, handle) T3-4 Sternal angle (at the attachment of the second costal cartilage; also at the level of the T4/T5 intervertebral disc) Body T5-9 Xiphoid process (Gr. xiphos, sword) T9

Pectoralis Minor Muscle

Origin - Anterior surfaces of ribs 3-5 - deep fascia overlying the related intercostal spaces Insertion: coracoid process of scapula Innervation: medial pectoral nerve (C8, T1) Action - depresses tip of shoulder - protracts scapula

Pectoralis Major Muscle

Origin: - sternal half of clavicle (clavicular head) - upper half of sternum (sternocostal head) - aponeurosis of external abdominal oblique muscle Insertion: intertubercular groove of humerus Innervation: Medial and lateral pectoral nerves (C5-8 and T1) Action: Flexes, adducts, and medially rotates the humerus

True ribs vs. False ribs

True ribs (ribs 1 to 7) - have a costal cartilage that is attached directly to the sternum False ribs (ribs 8 to 12) - have a costal cartilage that is not directly attached to the sternum. The costal cartilage of ribs 8 through 10 is attached to the costal cartilage of the rib above. The costal cartilage of ribs 11 and 12 is not attached to a skeletal element but ends in the abdominal musculature and, because of this, these two false ribs are also called floating ribs.

Clavicle

clavicle articulates with the manubrium of the sternum (sternoclavicular joint) and the lateral end of the clavicle articulates with the acromion of the scapula (acromioclavicular joint)

Thorax

houses and protects heart and lungs mobility to accommodate volume changes during respiration protection and flexibility are accomplished by the alternating arrangement of the ribs and intercostal muscles.