THE THORAX: BONES AND JOINTS

Thorax

the upper part of the trunk, is a cage composed of bones and cartilages, which affords protection for several very vital organs; the heart with its trunk vessels and the respiratory organs.

* Thoracic vertebra
* Sternum – breast bone
* Ribs or costae – 12 pairs
* Costa cartilages – 12 pairs

The skeleton of the thorax includes

Costovertebral

– between a rib and the body of a vertebra

Costotrasverse

– between a rib and a transverse process of a vertebra

Sternocostal or costosternal

– between a rib cartilage and the sternum

Costochondral

– between a rib and its costal cartilage

Interchondral

– between the adjacent anterior margins of costal cartilages of 6th to 10th ribs.

Sternoclavicular

– between the sternum and the clavicle

Manubriosternal

– between the manubrium and the body of the sternum

Xiphisternal

– between the body of the sternum and its xiphoid process.

Sternum

– flat bone

Sternum parts

* Manubrium
* Body or gladiolus
* Xiphoid process

Manubrium

O Jugular notch (suprasternal notch)

O Clavicular notches

O Costal notches – complete and half

Ribs (costae)

– 12 pairs O Dorsal extremity or vertebral extremity (end) O Body or shaft with an angle O Ventral extremity or sternal extremity

The Sternum

– is a long bone that lies vertically in the midline of the anterior chest wall.

Manubrium

– the upper part and represents the handle of the sword.

Clavicular notches

– depression on the upper surface of the manubrium.

The body or gladiolus

– extends from the manubrium to the xiphoid process and is the largest part of the sternum.

Sternal angle

– (angle of Louis or Ludwig) is marked by a prominent transverse ridge at the junction of the manubrium and the body of sternum.

Xiphoid process

– inferior part of the bone

Costal notches

\- are niches on the lateral margins of the sternum

Ribs

– long, curved, flat bones that form the posterior wall, lateral walls and part of the anterior wall of the thorax.

Head

– slightly expanded posterior end.

Neck

– slightly constricted part connecting the head to the body

Tubercle

– small prominence on the dorsal surface at the junction of the neck and body.

The body

long flat, curved part that extends from the neck around the chest wall. At its lower margin there is a groove- the costal groove – fror an intercostal artery, vein and nerve.

Angle of a rib

is a prominence in front of the neck where the rib becomes bent anteriorly.

The ventral or sternal extremity

– anterior end that articulates with its costal cartilage.

The first rib

has 2 grooves running transversely on its upper anterior surface for the subclavian artery and vein.

The 1st, 10th, 11th and 12th ribs

have a single articular surface on the head, not two.

The 11th and 12th ribs

have no tubercles.

True ribs

– upper seven pairs

False ribs

– lower five pairs

Vertebrosternal

– upper seven pairs

Vertebrochondral

– 8 th, 9th and 10th pairs

Vertebral ribs

– 11th and 12th pairs

Costal Cartilages

– flat plates of cartilages similar in shape to the adjacent rib.

Costal arch

– curved formed by the anterior margins of the 7th, 8th, 9th and 10th costal cartilages on each side and the rounded tip of the xiphoid process.

Costochondral joints

Located at the anterior, or sternal, end of a rib and the adjacent costal cartilage.

Sternocostal or costosternal joints

* sliding synovial joints (except the 1st which is cartilagionous)


* Formed by the sternal (anterior) end of a costal cartilage articulating with a costal notch on the lateral margin of the sternum. (upper 7)

Interchondral joints

Located between adjacent anterior margins of the 7th, 8th, 9th and 10th costal cartilages and the rib cartilage above each one.

Sternoclavicular joints

* gliding joints
* Between the sternal end of the clavicle and clavicular notch of the sternum

Manubriosternal joint

* cartilaginous joint
* Between the inferior margin of the manubrium and the upper margin of the body of the sternum, at the sternal angle.

Xiphesternal or xiphosternal joint

* cartilaginous joint
* Located between the inferior end of the body of the sternum and the xiphoid process of the sternum.

Cervical ribs

– and extra rib may be present on one or both sides above the first rib.

Lumbar ribs

– short extra rib that may be present below the 12th rib.

Absence of ribs

– one or more ribs may be absent on one or both sides.

Forked ribs

– the anterior or sternal end of a rib may divide into two parts.

Pectus excavatum

– the sternum may be depressed so that it lies closer to the thoracic vetrebrae than usual.

Pigeon chest

– prominent sternum may be present.

* Jugular notch
* Sternal Angle
* Xiphisternal joint
* Costal Arch

Landmarks – Prominences of the Bones of the Chest

* Sternum
* Sternoclavicular joints
* The ribs
* Costal cartilages

Radiography of the Thorax