The rib cage or thoracic cage is an endoskeletal enclosure in the thorax of most vertebrates that comprises the ribs, vertebral column and sternum, which protect the vital organs of the thoracic cavity, such as the heart, lungs and great vessels and support the shoulder girdle to form the core part of the axial skeleton.

that are crucial for active inhalation and forced exhalation, and therefore has a major ventilatory function in the respiratory system.

[4] The superficial surface of the rib cage is covered by the thoracolumbar fascia, which provides external attachments for the neck, back, pectoral and abdominal muscles.

The area between the angle and the tubercle is rounded, rough, and irregular, and serves for the attachment of the longissimus dorsi muscle.

The head is small and rounded, and possesses only a single articular facet, for articulation with the body of the first thoracic vertebra.

There is no angle, but at the tubercle, the rib is slightly bent, with the convexity upward, so that the head of the bone is directed downward.

The upper surface of the body is marked by two shallow grooves, separated from each other by a slight ridge prolonged internally into a tubercle, the scalene tubercle, for the attachment of the anterior scalene; the anterior groove transmits the subclavian vein, the posterior the subclavian artery and the lowest trunk of the brachial plexus.

The outer border is convex, thick, and rounded, and at its posterior part gives attachment to the first digitation of the serratus anterior.

The body is not twisted so that both ends touch any plane surface upon which it may be laid; but there is a bend, with its convexity upward, similar to, though smaller than that found in the first rib.

Its external surface is convex, and looks upward and a little outward; near the middle of it is a rough eminence for the origin of the lower part of the first and the whole of the second digitation of the serratus anterior; behind and above this is attached the posterior scalene.

The costal cartilage of the second rib articulates with the sternum at the sternal angle making it easy to locate.

[10] The transversus thoracis muscle is innervated by one of the intercostal nerves and superiorly attaches at the posterior surface of the lower sternum.

[12] Thus, males generally have broad shoulders and expanded chests, allowing them to inhale more air to supply their muscles with oxygen.

The development of the rib cage is influenced by a combination of genetic and environmental factors, as well as specific stages of embryonic growth.

Genetic factors play a critical role, with specific genes regulating the formation of bones and cartilage to ensure the proper development and alignment of the ribs and sternum.

During the embryonic stage, the rib cage begins to form from the mesoderm, one of the three primary germ layers.

Initially, the ribs are composed of cartilage, which gradually ossifies into bone through a process known as endochondral ossification.

Additionally, environmental factors such as maternal health, nutrition, and exposure to certain substances can impact rib cage development.

For instance, deficiencies in essential nutrients like calcium and vitamin D may hinder proper bone growth and development.

When the diaphragm contracts, the ribs are able to evert (meaning turn outwards or inside out) and produce what is known as the bucket handle movement, facilitated by gliding at the costovertebral joints.

The circumference of the normal adult human rib cage expands by 3 to 5 cm during inhalation.

A dislocated rib can be painful and can be caused simply by coughing, or for example by trauma or lifting heavy weights.

[16] One or more costal cartilages can become inflamed – a condition known as costochondritis; the resulting pain is similar to that of a heart attack.

The phenomenon has been appreciated particularly by craniofacial surgeons, who use both cartilage and bone material from the rib for ear, jaw, face, and skull reconstruction.

[6][8] The perichondrium and periosteum are fibrous sheaths of vascular connective tissue surrounding the rib cartilage and bone respectively.

The ribs, particularly their sternal ends, are used as a way of estimating age in forensic pathology due to their progressive ossification.

[19] The number of ribs as 24 (12 pairs) was noted by the Flemish anatomist Vesalius in his key work of anatomy De humani corporis fabrica in 1543, setting off a wave of controversy, as it was traditionally assumed from the Biblical story of Adam and Eve that men's ribs would number one fewer than women's.