The Thoracic Cage and Pneumothorax | Real Anatomy

by Robert Tallitsch, PhD | October 25, 2021

Brain Builder with 3D anatomy of the thoracic cage and

Blog and video explanation of the thoracic cage and a pneumothorax with symptoms, causes, treatments and a patient case example!


Written by: Robert Tallitsch, PhD

In this article we are going to discuss the thoracic cage, which consists of the ribs, sternum, and costal cartilages. 

After we complete our discussion of the thoracic cage, we will discuss rib fractures and the complications of fractured and cracked ribs. Finally, we will discuss a life-threatening complication of a fractured rib — a pneumothorax.

Thoracic Cage

The thoracic cage surrounds and protects some of the most vital organs, and supports the pectoral girdle. The ribs of the thoracic cage are comprised of flat bones, and the costal cartilage consist of hyaline cartilage. 


There are 12 pairs of ribs.

  • Ribs 1-7 are termed true or vertebrosternal ribs.  Each of these ribs connects anteriorly to the sternum, with a separate, individual costal cartilage. 
  • Ribs 8, 9 and 10 are termed false, or vertebrochondral, ribs because they do not connect directly to the sternum by separate, individual costal cartilages. The costal cartilages of false ribs fuse before attaching to the sternum.
  • Ribs 11 and 12 are termed floating ribs, and do not attach to the sternum.

The vertebral end of each rib possesses a head, neck, and one or more articular facets. 
The head of each rib articulates with the thoracic region of the vertebral column, either between two adjacent vertebral bodies or with the body of a single thoracic vertebra. 

As you move anteriorly from the head of the rib you will encounter a short neck. Anterior to the neck of ribs 1 through 10 you will find a posteriorly projecting tubercle. This tubercle articulates with the transverse process of a thoracic vertebra. Ribs 11 and 12 do not possess such a tubercle and, therefore, do not articulate with the transverse processes of any thoracic vertebrae. 

The body of the rib begins to curve towards the sternum at the angle of the rib. The costal grove of the rib is found on the internal, inferior surface of the rib. This grove houses the intercostal artery, vein, and nerve.


The sternum is composed of three parts, each of which develops independently. These three parts typically fuse together at or around the age of 25. 

  • The manubrium of the sternum is the most superior of the three parts. It articulates with the clavicles of the appendicular skeleton and the costal cartilages of the first pair of ribs.
  • The body of the sternum articulates with the manubrium superiorly and the costal cartilages of ribs 2 through 10 laterally. Because ribs 8, 9 and 10 are false ribs they typically attach to the manubrium by a single costal cartilage.
  • The xiphoid process is the most inferior and smallest part of the sternum. 

Rib Fracture

A cracked or fractured rib is a common injury. A fracture to one or more of the 4th through 9th ribs is most frequent, due to their more lateral location within the skeleton of the thoracic cavity.

A cracked rib, which is significantly less dangerous than a fractured rib, is most common. Both types of injuries are quite painful, and the pain is typically manifested when one takes a deep breath, bends or twists the trunk of the body, or presses on the injured area. 

If the rib is fractured into two or more pieces injury to blood vessels, nerves, and/or an organ of the thoracic or abdominal cavities are real possibilities. 

Because floating ribs do not attach to the sternum, a fracture of a floating rib is rather uncommon. However, if a floating rib does fracture the sharp, broken ends of the rib may damage the spleen, liver, or a kidney.

A punctured lung or a lacerated aorta, both of which are life-threatening injuries, may occur following a severe fracture to one or more ribs. The chance of internal injuries following a rib fracture increases significantly with the number of broken ribs.


Traumatic, crushing injuries often result in multiple rib fractures. This type of injury sometimes results in a pneumothorax, which is another life-threatening injury. A pneumothorax results when air enters the thoracic cavity through a puncture of the chest wall. The resulting increased intra-thoracic pressure will cause a partial or total collapse of one or both lungs. This type of injury is treated by first sealing the puncture of the chest wall. Then a needle is inserted through the chest wall and into the thoracic cavity. Suction is applied through the needle, removing the excess air from the thoracic cavity. This decrease in intrathoracic pressure typically results in a reinflation of the collapsed lung.

One should always consult a physician if you suspect a cracked or broken rib. Medical attention should be sought immediately if the injured person is experiencing difficulty in breathing and/or is suspected of cardiovascular injury.

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