Regional anatomy of thorax Boundaries Superior － jugular notch, sternoclavicular joint, superior border of clavicle, acromion, spinous processes of C7 Inferior － xiphoid process, costal arch, 12th and 11th ribs, vertebra T12 Regions Thoracic wall Thoracic cavity

THORACIC CAGE Thoracic cage is an osteo-cartilagenous conical cage which has a narrow inlet & a wide outlet …

Ant: Sternum, Costal cartilages and Ribs. Post: Thoracic vertebrae and ribs. Lat: Ribs.

Thoracic Inlet/SUPERIOR APERTURE Ant: Upper border of manubrium sterni. Post : sup.sur. 1 st thoracic vertebra. On each side: 1 st rib & 1 st costal cartilage. It is sloping downwards & forward.

OUTLET OF THORAX Def.-the broad lower end of thorax which is continuous with the abdominal cavity is called the outlet of thorax BOUNDARIES : In front-by : the xiphoid process & 7-10 th costal cartilage forming an intrasternal angle Behind - inf.surface of body of T12 On Sides - 11th & 12th ribs Inferiorly : Diaphragm

Thoracic vertebrae. They are 12 vertebra. From 2 to 8 they are called Typical. Character of typical thoracic vertebrae: Body: Heart shape & carries 2 demi-facet at its side. Transverse process: has a facet for rib tubercle of the same number. Spine: Long, pointed & directed downward and backward. Vertebral foramen: Small & circular.

Articulation between Thoracic vertebrae and the ribs

Atypical (Non typical ) thoracic vertebrae. 1 st, 10 th,11 th and 12 th T1: Has a complete Superior costal facet. One very small inferior demifacet. Spine nearly horizontal Has costal facet in transverse process for the tubercle of first rib. It has a small body, looks like a cervical vertebra.

12 pairs. Articulates with thoracic vertebrae. - Number might ↑ or ↓. Uppers ribs – oblique (max at 9 th ). Lower ribs – less oblique. Length – maximum in 7 th and decreases towards both ends.

Classification: True,false,typical and atypical ribs. True and false ribs. -True ribs – 1-7 as they are connected to the sternum through their respective cartilages.(vertebro sternal ribs). - False ribs – 8, 9, 10, 11, 12. Connected to next higher cartilages to reach sternum but 11, 12 are free in the anterior ends, called floating ribs. Typical ribs: 3 – 9 Atypical ribs: 1,2 & 10, 11, 12

Parts of typical rib: Anterior,posterior ends & shaft. - Anterior end : Oval, concave articulates with costal cartilage. -Posterior end: - head with 2 facets articulating with the body of thoracic vertebra. - small neck. - tubercle: junction of neck & shaft; articulates with transverse process of thoracic vertebra.

Shaft: 2 surfaces (outer and inner)& angle - outer surface: convex - inner surface: concave, covered by pleura; & inner costal groove above the inferior border.

TYPICAL RIB

Atypical ribs ● 1st, 2nd, 10th, 11th, 12th ribs. First rib Shortest, flattest and most curved. Articulate with T1 only. 2 groove: -Anterior- subclavian vein -Posterior-lowest trunk of the brachial plexus and subclavian artery 1 tubercle (inner); attachment of scalenus anterior muscle.

Atypical ribs… Second rib -Less curved -2x long as 1 st rib. -tubercle (ext lower border) Tenth rib 1 articular facet on its head. Eleventh rib -1 articular facet on its head. - NO tubercle for articulation with the transverse process. Twelfth rib -1 articular facet on its head. -NO tubercle and subcostal groove.

Forking or duplication of the ribs

Frontal chest radiograph shows a bone bridge joining the right anterior first and second ribs. Pseudoarticulation is also present (arrows). This finding is typical in pseudarthrosis and should not be mistaken for a fracture.

● Cervical ribs:  Bony or fibrous bands between C7 and the 1st rib.  1-2% of subjects.  10% of these cause compressive symptoms, ranging from nerve compression or to subclavian artery post stenotic aneurysm. The remainder are asymptomatic.  May be large or small, single or bilateral, and may articulate with the 1 st rib.  If they consist only of a fibrous band they will not be visible on radiographs. They can be confused with hypoplastic first ribs.

*The 7th cervical transverse processes point downwards, 1st thoracic transverse processes are angled upwards.

Cervical ribs in an asymptomatic patient. Frontal chest radiograph shows bilateral cervical ribs (arrowheads); the left one fuses anteriorly to the first rib (arrow).

● Lumbar ribs: transverse process (costal element of the lumbar vertebra) may fail to fuse with the vertebral body and retain asynovial joint with the neural arch. Asymptomatic.

COSTAL CARTILAGES ● unossified anterior ends of the ribs. ● Slope upwards to the sternum 1 st – 7 th ribs articulate with sternum (sternochondral joints) ● 8th – 10th ribs articulate with the costal cartilages of the ribs above. ● 11th and 12th costal cartilages have pointed ends and end in the muscles of the abdominal wall.

Sternum

Sternum is a flat bone, present in front of the thoracic cage. Parts: Manubrium, Body and Xiphoid process. Manubrium is the - upper part of the sternum. - joins with medial end of clavicle and first costal cartilage. - Jugular or interclavicular or suprasternal notch. Sternum

Body : - larger part of the sternum. - on each side, it receives ribs through their costal cartilages (3rd to 6th rib). Xiphoid process: - the most variable part of the sternum. - cartilaginous structure in adults. Sternum

THE STERNUM ● Manubrium -opposite T3 and T4 -articulates with clavicle and with 1½ costal Cartilages ● Sternal angle - secondary cartilaginous joint,lies opposite T 4/5 disc space ● Body -opposite T 5 -T 9, made up of four stenebrae which articulate with 5 ½ costal cartilages ● Xiphoid process -remains cartilaginous into adult life.

Variation in Sternal configuration: Pectus excavatum, depression of the lower end. Pectus carinatum, prominence of the midportion