Costal cartilage, also known as rib cartilage, are bars of hyaline cartilage that serve to prolong the ribs forward and contribute to the elasticity of the walls of the

thorax The thorax (: thoraces or thoraxes) or chest is a part of the anatomy of mammals and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main di ...

. Costal cartilage is only found at the anterior ends of the ribs, providing medial extension.

Differences from ribs 1-12

The first seven pairs are connected with the

sternum The sternum (: sternums or sterna) or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major bl ...

; the next three are each articulated with the lower border of the cartilage of the preceding rib; the last two have pointed extremities, which end in the wall of the

abdomen The abdomen (colloquially called the gut, belly, tummy, midriff, tucky, or stomach) is the front part of the torso between the thorax (chest) and pelvis in humans and in other vertebrates. The area occupied by the abdomen is called the abdominal ...

. Like the ribs, the costal cartilages vary in their

length Length is a measure of distance. In the International System of Quantities, length is a quantity with Dimension (physical quantity), dimension distance. In most systems of measurement a Base unit (measurement), base unit for length is chosen, ...

, breadth, and direction. They increase in length from the first to the seventh, then gradually decrease to the twelfth. Their breadth, as well as that of the intervals between them, diminishes from the first to the last. They are broad at their attachments to the ribs, and taper toward their sternal extremities, excepting the first two, which are of the same breadth throughout, and the sixth, seventh, and eighth, which are enlarged where their margins are in contact. They also vary in direction: the first descends a little to the sternum, the second is horizontal, the third ascends slightly, while the others are angular, following the course of the ribs for a short distance, and then ascending to the sternum or preceding cartilage.

Structure

Each costal cartilage presents two surfaces, two borders, and two extremities.

Surfaces

The ''anterior surface'' is convex, and looks forward and upward: that of the first gives attachment to the costoclavicular ligament and the subclavius muscle; those of the first six or seven at their sternal ends, to the pectoralis major. The others are covered by, and give partial attachment to, some of the flat muscles of the abdomen. The ''posterior surface'' is concave, and directed backward and downward; that of the first gives attachment to the sternothyroideus, those of the third to the sixth inclusive to the transversus thoracis muscle, and the six or seven inferior ones to the transversus abdominis muscle and the diaphragm.

Borders

Of the two borders the ''superior'' is concave, the inferior convex; they afford attachment to the internal intercostals: the upper border of the sixth gives attachment also to the pectoralis major. The ''inferior'' borders of the sixth, seventh, eighth, and ninth cartilages present heel-like projections at the points of greatest convexity. These projections carry smooth oblong facets which articulate with facets on slight projections from the upper borders of the seventh, eighth, ninth, and tenth cartilages, respectively.

Interchondral articulations

The interchondral articulations are the

joint A joint or articulation (or articular surface) is the connection made between bones, ossicles, or other hard structures in the body which link an animal's skeletal system into a functional whole.Saladin, Ken. Anatomy & Physiology. 7th ed. McGraw- ...

s formed between the costal cartilages of the ribs. The contiguous borders of the sixth, seventh, and eighth, and sometimes those of the ninth and tenth, costal cartilages articulate with each other by small, smooth, oblong facets. Each articulation is enclosed in a thin articular capsule, lined by

synovial membrane Synovial () may refer to: * Synovial fluid * Synovial joint A synovial joint, also known as diarthrosis, joins bones or cartilage with a fibrous joint capsule that is continuous with the periosteum of the joined bones, constitutes the outer bou ...

and strengthened laterally and medially by

ligament A ligament is a type of fibrous connective tissue in the body that connects bones to other bones. It also connects flight feathers to bones, in dinosaurs and birds. All 30,000 species of amniotes (land animals with internal bones) have liga ...

ous fibers (interchondral ligaments) which pass from one cartilage to the other. Sometimes the fifth costal cartilages, more rarely the ninth and tenth, articulate by their lower borders with the adjoining cartilages by small oval facets; more frequently the connection is by a few ligamentous fibers.

Extremities

The lateral end of each cartilage is continuous with the osseous tissue of the rib to which it belongs. The medial end of the first is continuous with the sternum; the medial ends of the six succeeding ones are rounded and are received into shallow concavities on the lateral margins of the sternum. The medial ends of the eighth, ninth, and tenth costal cartilages are pointed, and are connected each with the cartilage immediately above. Those of the eleventh and twelfth are pointed and free.

Clinical significance

old age Old age is the range of ages for people nearing and surpassing life expectancy. People who are of old age are also referred to as: old people, elderly, elders, senior citizens, seniors or older adults. Old age is not a definite biological sta ...

, the costal cartilages are prone to superficial

ossification Ossification (also called osteogenesis or bone mineralization) in bone remodeling is the process of laying down new bone material by cells named osteoblasts. It is synonymous with bone tissue formation. There are two processes resulting in t ...

, particularly in women with age of 50 years and over. In costochondritis and Tietze syndrome, inflammation of the costal cartilage occurs. This is a common cause of chest pain. Severe trauma may lead to

fracture Fracture is the appearance of a crack or complete separation of an object or material into two or more pieces under the action of stress (mechanics), stress. The fracture of a solid usually occurs due to the development of certain displacemen ...

of the costal cartilage. Such injuries often go unnoticed during x-ray scans, but can be diagnosed with CT scans.

Surgery Surgery is a medical specialty that uses manual and instrumental techniques to diagnose or treat pathological conditions (e.g., trauma, disease, injury, malignancy), to alter bodily functions (e.g., malabsorption created by bariatric surgery s ...

is typically used to fix the costal cartilage back onto either the rib or sternum. Costal cartilage may be harvested for reparative use elsewhere in the body. Whilst this is typically conducted using a

general anaesthetic General anaesthetics (or anesthetics) are often defined as compounds that induce a loss of consciousness in humans or loss of righting reflex in animals. Clinical definitions are also extended to include an induced coma that causes lack of awaren ...

, IV sedation can also be used. The procedure presents a minor risk of pleural tear.

Additional images

File:Costal cartilages animation.gif, Position of the costal cartilages (shown in red). Animation. File:Gray115.png, Anterior surface of

and costal cartilages.

References

External links

Link to picture
{{DEFAULTSORT:Costal Cartilages Skeletal system Connective tissue Thorax (human anatomy)