Lab 12 – 5.1: Osteology of the Thorax

Typical Thoracic Vertebrae

Thoracic Vertebrae

Thoracic Vertebrae

Body of Sternum Description: Long flat part of sternum between manubrium and xiphoid process Contributes to sternal angle (angle of Louis) at its superior border Articulates with costal cartilages 2- 7

Manubrium Description: Articulates with costal cartilages 1-2 and clavicle Rib 1 symphasis Other ribs synovial Provides attachment for sternocleidomastoid and pectoralis major muscles

Xiphoid process Description: Connected to sternal body at Xiphisternal joint Provides attachment for anterior abdominal wall muscles Landmark for cardiopulmonary resuscitation (CPR)

Jugular Notch Description: Prominent concavity along superior border of manubrium, between medial ends of clavicles

Sternal Angle Description: Transverse ridge on anterior thoracic wall Formed by junction of manubrium and body of sternum Costal cartilage of rib 2 articulates with sternum at angle “Angle of Louis” Bony landmark to identify Rib 2

Features of Sternum Note: Articular facets for ribs and clavicle

Costal Cartilage Description: Attaches rib to sternum

False Ribs Description: Ribs 8-12 Paired, curved, flat bones Articulate with thoracic vertebrae Attach indirectly to sternum via a shared costal cartilage (ribs 8-10) or not attached to sternum (ribs 11-12)

Floating Ribs Description: Ribs Paired, curved, flat bones Articulate with thoracic vertebrae Not associated with costal cartilage, thus not attached to sternum

True Ribs Description: Ribs 1-7 Paired, curved, flat bones Articulate with thoracic vertebrae Attach directly to sternum by costal cartilages

Rib Features Note: Costal grooves – major arteries and veins line grooves Articular facets – Superior facet articulates with inferior facet on superior vertebrae Inferior facet articulates with superior facet on inferior vertebrae Tubercle facet articulates with transverse process of inferior vertebrae

Articular Facets Articular facets – Superior facet articulates with inferior facet on superior vertebrae Inferior facet articulates with superior facet on inferior vertebrae Tubercle facet articulates with transverse process of inferior vertebrae

Rib Features Description:

External Intercostal M. Superior attachemnt: inferior margin of rib above Inferior Attachment: Superior margin of rib velow Innervation: Intercostal nerves (T1-T11) Function: Inspiration; suports intercostal space; moves ribs superiorly

Internal Intercostal M. Superior Attachment: Lateral edge of costal groove of rib above Inferior Attachment: Superior margin of rib below deep to external intercostal Innervation: Intercostal nerves (T1-T11) Function: Expiration; support intercostal space; moves ribs inferiorly

Innermost Intercostal M. Superior Attachment: Medial edge of costal groove of rib above Inferior Attachment: Internal aspect of superior margin of rib below Innervation: Intercostal Nerves (T1-T11) Function: Acts with internal intercostal muscles

Subcostal M. Superior Attachment: Internal surface of lower ribs Interior Attachment: internal surface of second or third rib below Innervation: Related intercostal nerves Function: depress ribs

Transversus Thoracis M. Superior Attachment: Interior margin and internal surfaces of costal cartilages of second to sixth ribs Interior Attachment: Inferior aspect of deep surface of body of sternum, xiphoid process and costal cartilage ribs IV-VII Innervation: Related intercostal nerves Function: Depresses costal cartilages

Intercostal N. Description: Somatic motor innervation to muscles of thoracis wall Somatic sensory innervation from skin and parietal pleura Postganglionic sympathetic fibers to the periphery

Posterior Intercostal A. Provide blood supply to the thoracic wall Accompany lateral cutaneous branches of intercostal nerves

Anterior Intercostal A. Branches from internal thoracic arteries Supplies upper six intercostal spaces Divides into superior epigastric artery and musculophrenic artery

Superior Epigastric A. Continues inferiorly from internal thoracic artery

Musculophrenic A. Passes along the costal margin, goes through the diaphragm and ends near late intercostal space

Intercostal Veins Drains thoracic wall