In vertebrate anatomy, ribs (Latin: costae) are the long curved bones which form the rib cage, part of the axial skeleton. In most tetrapods, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the chest cavity. They serve to protect the lungs, heart, and other internal organs of the thorax. In some animals, especially snakes, ribs may provide support and protection for the entire body.

Detail of a single human rib
The human rib cage (Source: Gray's Anatomy of the Human Body, 20th ed. 1918)
Anatomical terminology

Human anatomy

Rib details

Ribs are classed as flat bones which usually have a protective role in the body. Humans have 24 ribs, in 12 pairs. All are attached at the back to the thoracic vertebrae, and are numbered from 1–12 according to the vertebrae they attach to. The first rib is attached to thoracic vertebra 1 (T1). At the front of the body most of the ribs are joined by costal cartilages to the sternum. The ribs connect to the vertebrae with two joints, the costovertebral joints.

The parts of a rib include the head, neck, body (or shaft), tubercle, and angle.

The head of the rib lies next to a vertebra. The ribs connect to the vertebrae with two costovertebral joints, one on the head and one on the neck. The head of the rib has a superior and an inferior articulating region, separated by a crest. These articulate with the superior and inferior costal facets on the connecting vertebrae.[1] The crest gives attachment to the intra-articulate ligament that joins the rib to the vertebra of the same number, at the intervertebral disc. Another ligament, the radiate ligament joins the head of the rib to the both the body of the upper vertebra and to the body of the lower vertebra. The smaller middle part of the ligament connects to the intervertebral disc. This plane joint is known as the articulation of the head of the rib.

The other costovertebral joint is that between the tubercle on the neck and the transverse process of the joining thoracic vertebra of the same rib number, and this is known as the costotransverse joint. The superior costotransverse ligament attaches from the non-articular facet of the tubercle to the transverse process of the vertebra.

The neck of the rib is a flattened part that extends laterally from the head. The neck is about 3 cm long. Its anterior surface is flat and smooth, whilst its posterior is perforated by numerous foramina and its surface rough, to give attachment to the ligament of the neck. Its upper border presents a rough crest (crista colli costae) for the attachment of the anterior costotransverse ligament; its lower border is rounded.

A tubercle of rib on the posterior surface of the neck of the rib, has two facets (surfaces) one articulating and one non-articulating. The articular facet, is small and oval and is the lower and more medial of the two, and connects to the transverse costal facet on the thoracic vertebra of the same rib number.[1] The transverse costal facet is on the end of the transverse process of the lower of the two vertebrae to which the head is connected. The non-articular portion is a rough elevation and affords attachment to the ligament of the tubercle. The tubercle is much more prominent in the upper ribs than in the lower ribs.

Rib cage

Ribs labeled
X-ray image of human chest, with ribs labelled

The first seven sets of ribs, known as "true ribs", are attached to the sternum by the costal cartilages. The first rib is unique and easier to distinguish than other ribs. It is a short, flat, C-shaped bone. The vertebral attachment can be found just below the neck at the first thoracic vertebra, and the majority of this bone can be found above the level of the clavicle. Ribs 2 through 7 have a more traditional appearance and become longer and less curved as they progress downwards.[2] The following five sets are known as "false ribs", three of these sharing a common cartilaginous connection to the sternum, while the last two (eleventh and twelfth ribs) are termed floating ribs. They are attached to the vertebrae only, and not to the sternum or cartilage coming off of the sternum.

In general, human ribs increase in length from ribs 1 through 7 and decrease in length again through rib 12. Along with this change in size, the ribs become progressively oblique (slanted) from ribs 1 through 9, then less slanted through rib 12.[2]

The rib cage is separated from the lower abdomen by the thoracic diaphragm which controls breathing. When the diaphragm contracts, the thoracic cavity is expanded, reducing intra-thoracic pressure and drawing air into the lungs. This happens through one of two actions (or a mix of the two): when the lower ribs the diaphragm connects to are stabilized by muscles and the central tendon is mobile, when the muscle contracts the central tendon is drawn down, compressing the cavity underneath and expanding the thoracic cavity downward. When the central tendon is stabilized and the lower ribs are mobile, a contraction of the diaphragm elevates the ribs, which works in conjunction with other muscles to expand the thoracic indent upward.


Early in the developing embryo, somites form and soon subdivide into three mesodermal components – the myotome, dermatome, and the sclerotome. The vertebrae and ribs develop from the sclerotomes.[3]

During the fourth week (fertilization age) costal processes have formed on the vertebral bodies. These processes are small, lateral protrusions of mesenchyme that develop in association with the vertebral arches. During the fifth week the costal processes on the thoracic vertebrae become longer to form the ribs. In the sixth week, the costovertebral joints begin to develop and separate the ribs from the vertebrae. The first seven pairs of ribs, the true ribs join at the front to the sternal bars. By the fetal stage the sternal bars have completely fused.[3]

The ribs begin as cartilage that later ossifies – a process called endochondral ossification. Primary ossification centers are located near the angle of each rib, and ossification continues in the direction away from the head and neck. During adolescence secondary ossification centers are formed in the tubercles and heads of the ribs.[3]

Other animals

Dog anatomy lateral skeleton view
Skeleton of a dog showing the location of the ribs
Eptesicus fuscus ribcage
Rib cage of the big brown bat (Eptesicus fuscus)

In fish, there are often two sets of ribs attached to the vertebral column. One set, the dorsal ribs, are found in the dividing septum between the upper and lower parts of the main muscle segments, projecting roughly sideways from the vertebral column. The second set, the ventral ribs arise from the vertebral column just below the dorsal ribs, and enclose the lower body, often joining at the tips. Not all species possess both types of rib, with the dorsal ribs being most commonly absent. Sharks, for example, have no dorsal ribs, and only very short ventral ribs, while lampreys have no ribs at all. In some teleosts, there may be additional rib-like bones within the muscle mass.[4]

Tetrapods, however, only ever have a single set of ribs which are probably homologous with the dorsal ribs of fishes. In the early tetrapods, every vertebra bore a pair of ribs, although those on the thoracic vertebrae are typically the longest. The sacral ribs were stout and short, since they formed part of the pelvis, connecting the backbone to the hip bones.[4]

In most subsequent forms, many of these early ribs have been lost, and in living amphibians and reptiles, there is great variation in rib structure and number. For example, turtles have only eight pairs of ribs, which are developed into a bony or cartilaginous carapace and plastron, while snakes have numerous ribs running along the full length of their trunk. Frogs typically have no ribs, aside from a sacral pair, which form part of the pelvis.[4]

In birds, ribs are present as distinct bones only on the thoracic region, although small fused ribs are present on the cervical vertebrae. The thoracic ribs of birds possess a wide projection to the rear; this uncinate process is an attachment for the shoulder muscles.[4] Usually dogs have 26 ribs. Mammals usually also only have distinct ribs on the thoracic vertebra, although fixed cervical ribs are also present in monotremes. In marsupials and placental mammals, the cervical and lumbar ribs are found only as tiny remnants fused to the vertebrae, where they are referred to as transverse processes. In general, the structure and number of the true ribs in humans is similar to that in other mammals. Unlike reptiles, caudal ribs are never found in mammals.[4]

Ribs as food

Ribs as food are widely used from many animals. The ribs are the less meaty part of the meat chop and they are often cooked as part of a slab; five or more is known as a rack, as in a rack of lamb. Short ribs are ribs of beef either served singly or several as a plate. A rib steak from beef is a popular choice used in many cuisines. Pork ribs, including spare ribs are popular in European and Asian cuisine.

Additional images

Ribs animation

Human ribs (shown in red). It consists of 24 ribs. Left and right of first rib to twelfth rib.

See also


  1. ^ a b Netter, Frank (2014). Atlas of human anatomy (Sixth ed.). Saunders. pp. 183–184. ISBN 9781455704187.
  2. ^ a b Saladin, K. S. (2010). Anatomy and Physiology: The Unity of Form and Function (5th ed.). New York, NY: McGraw-Hill.
  3. ^ a b c Larsen, William (2001). Human embryology (3rd ed.). Churchill Livingstone. pp. 80–85. ISBN 0443065837.
  4. ^ a b c d e Romer, Alfred Sherwood; Parsons, Thomas S. (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. pp. 170–173. ISBN 0-03-910284-X.
  • Clinically Oriented Anatomy, 4th ed. Keith L. Moore and Robert F. Dalley. pp. 62–64
Adam's Rib

Adam's Rib is a 1949 American romantic comedy film directed by George Cukor from a screenplay written by Ruth Gordon and Garson Kanin. It stars Spencer Tracy and Katharine Hepburn as married lawyers who come to oppose each other in court. Judy Holliday co-stars as the third lead in her second credited movie role. The music was composed by Miklós Rózsa, except for the song "Farewell, Amanda", which was written by Cole Porter.

The film was well received upon its release and is considered a classic romantic comedy, being nominated for both AFI's 100 Movies and Passions lists, and coming in at #22 on the AFI's 100 Years...100 Laughs.

Amarna letters

The Amarna letters (; sometimes referred to as the Amarna correspondence or Amarna tablets, and cited with the abbreviation EA) are an archive, written on clay tablets, primarily consisting of diplomatic correspondence between the Egyptian administration and its representatives in Canaan and Amurru during the New Kingdom, between c. 1360-1332 BC (see here for dates). The letters were found in Upper Egypt at el-Amarna, the modern name for the ancient Egyptian capital of Akhetaten, founded by pharaoh Akhenaten (1350s – 1330s BC) during the Eighteenth dynasty of Egypt. The Amarna letters are unusual in Egyptological research, because they are mostly written in a script known as Akkadian cuneiform, the writing system of ancient Mesopotamia, rather than that of ancient Egypt, and the language used has sometimes been characterised as a mixed language, Canaanite-Akkadian. The written correspondence spans a period of at most thirty years.The known tablets total 382, of which 358 have been published by the Norwegian Assyriologist Jørgen Alexander Knudtzon's in his work, Die El-Amarna-Tafeln, which came out in two volumes (1907 and 1915) and remains the standard edition to this day. The texts of the remaining 24 complete or fragmentary tablets excavated since Knudtzon have also been made available.The Amarna letters are of great significance for biblical studies as well as Semitic linguistics, since they shed light on the culture and language of the Canaanite peoples in pre-biblical times. The letters, though written in Akkadian, are heavily colored by the mother tongue of their writers, who spoke an early form of Canaanite, the language family which would later evolve into its daughter languages, Hebrew and Phoenician. These "Canaanisms" provide valuable insights into the proto-stage of those languages several centuries prior to their first actual manifestation.

Axial skeleton

The axial skeleton is the part of the skeleton that consists of the bones of the head and trunk of a vertebrate. In the human skeleton, it consists of 80 bones and is composed of six parts; the skull bones, the ossicles of the middle ear, the hyoid bone, the rib cage, sternum and the vertebral column. The axial skeleton together with the appendicular skeleton form the complete skeleton. Another definition of axial skeleton is the bones including the vertebrae, sacrum, coccyx, ribs, and sternum.

Cervical rib

A cervical rib in humans is an extra rib which arises from the seventh cervical vertebra. Their presence is a congenital abnormality located above the normal first rib. A cervical rib is estimated to occur in 0.2% (1 in 500 people) to 0.5% of the population. People may have a cervical rib on the right, left or both sides.Most cases of cervical ribs are not clinically relevant and do not have symptoms; cervical ribs are generally discovered incidentally. However, they vary widely in size and shape, and in rare cases, they may cause problems such as contributing to thoracic outlet syndrome, because of pressure on the nerves that may be caused by the presence of the rib.A cervical rib represents a persistent ossification of the C7 lateral costal element. During early development, this ossified costal element typically becomes re-absorbed. Failure of this process results in a variably elongated transverse process or complete rib that can be anteriorly fused with the T1 first rib below.

E pluribus unum

E pluribus unum (; Latin: [ˈeː ˈpluːrɪbʊs ˈuːnũː])—Latin for "Out of many, one" (translated as "One out of many" or "One from many")—is a 13-letter traditional motto of the United States, appearing on the Great Seal along with Annuit cœptis (Latin for "he approves the undertaking [lit. 'things undertaken']") and Novus ordo seclorum (Latin for "New order of the ages"), and adopted by an Act of Congress in 1782. Never codified by law, E pluribus unum was considered a de facto motto of the United States until 1956 when the United States Congress passed an act (H. J. Resolution 396), adopting "In God We Trust" as the official motto.

Pork ribs

Pork ribs are a cut of pork popular in Western and Asian cuisines. The ribcage of a domestic pig, meat and bones together, is cut into usable pieces, prepared by smoking, grilling, or baking – usually with a sauce, often barbecue – and then served.

Rib (aeronautics)

In an aircraft, ribs are forming elements of the structure of a wing, especially in traditional construction.

By analogy with the anatomical definition of "rib", the ribs attach to the main spar, and by being repeated at frequent intervals, form a skeletal shape for the wing. Usually ribs incorporate the airfoil shape of the wing, and the skin adopts this shape when stretched over the ribs.

Rib cage

The rib cage is the arrangement of ribs attached to the vertebral column and sternum in the thorax of most vertebrates, that encloses and protects the heart and lungs. In humans, the rib cage, also known as the thoracic cage, is a bony and cartilaginous structure which surrounds the thoracic cavity and supports the shoulder girdle to form the core part of the human skeleton. A typical human rib cage consists of 24 ribs in 12 pairs, the sternum and xiphoid process, the costal cartilages, and the 12 thoracic vertebrae.

Together with the skin and associated fascia and muscles, the rib cage makes up the thoracic wall and provides attachments for the muscles of the neck, thorax, upper abdomen, and back.

The rib cage has a major function in the respiratory system.

Rib eye steak

The rib eye or ribeye is a beef steak from the rib section. The rib section of beef spans from ribs six through twelve. Ribeye steaks are mostly composed of the longissimus dorsi muscle but also contain the complexus and spinalis muscles.

Rib fracture

A rib fracture is a break in a rib bone. This typically results in chest pain that is worse with breathing in. Bruising may occur at the site of the break. When several ribs are broken in several places a flail chest results. Potential complications include a pneumothorax, pulmonary contusion, and pneumonia.Rib fractures usually occur from a direct blows to the chest such as during a motor vehicle collision or from a crush injury. Coughing or metastatic cancer may also result in a broken rib. The middle ribs are most commonly fractured. Fractures of the first or second ribs are more likely to be associated with complications. Diagnosis can be made based on symptoms and supported by medical imaging.Pain control is an important part of treatment. This may include the use of paracetamol (acetaminophen), NSAIDs, or opioids. A nerve block may be another option. While fractured ribs have been wrapped, this may increase complications. In those with a flail chest, surgery may improve outcomes. They are a common injury following trauma.

Rib steak

A rib steak is a beef steak sliced from the rib primal of a beef animal, with rib bone attached. In the United States, the term rib eye steak is used for a rib steak with the bone removed; however in some areas, and outside the U.S., the terms are often used interchangeably. The rib eye or "ribeye" was originally, as the name implies, the center portion of the rib steak, without the bone.

It is considered a more flavorful cut than other steaks, such as the fillet, due to the muscle being exercised by the animal during its life. Its marbling of fat makes this suitable for slow roasting or grilling cooked to different degrees of doneness. Marbling also increases tenderness, which plays a key role in consumers' rib steak purchase choices.

The short ribs: several ribs cut from the rib and plate primals and a small corner of the square-cut chuck.

Rib vault

The intersection of two to three barrel vaults produces a rib vault or ribbed vault when they are edged with an armature of piped masonry often carved in decorative patterns; compare groin vault, an older form of vault construction. While the mechanics of the weight of a groin vault and its transmission outwards to the supporting pillars remained as it had been, the new use of rib vaults demonstrates the skill of the masons and the grandeur of the new ideas circulating at the introduction of Islamic architecture in the eight century, and then adopted in Gothic architecture from the end of the eleventh century. This technique was new in the late eleventh century, for example in the roofs of the choir side-aisles at Durham Cathedral. Romanesque ancestors of the Gothic rib vault can be found in early Gothic constructions at Cefalù, Caen, Durham, and elsewhere.Some ribbed vaults even have six sections in each bay (for example, the sexpartite vault, formed by the intersection of three half "barrels").

Rigid-hulled inflatable boat

A rigid-hulled inflatable boat (RHIB) or rigid-inflatable boat (RIB) is a lightweight but high-performance and high-capacity unsinkable boat constructed with a rigid hull bottom joined to side-forming air tubes that are inflated with air to a high pressure so as to give the sides resilient rigidity along the boat’s topsides. The design is stable, light, fast and seaworthy. The inflated collar acts like a life jacket in that the vessel keeps its buoyancy even if much water comes aboard in heavy sea conditions, so is unsinkable. The RIB is an evolutionary development of the inflatable boat with a rubberized fabric bottom that is stiffened with flat boards within the collar to form the deck or floor of the boat.

Uses include work boats (supporting shore facilities or larger ships) in trades that operate on the water, military craft, where they are used in patrol roles and to transport troops between vessels or ashore, and lifeboats.

Short rib – polydactyly syndrome

Short rib – polydactyly syndrome is a family of four closely related dysplasias:

I - "Saldino-Noonan type"

II - "Majewski type"

III - "Verma-Naumoff type" (associated with DYNC2H1)

IV - "Beemer-Langer type"

Short ribs

Short ribs are a cut of beef taken from the brisket, chuck, plate, or rib areas of beef cattle. They consist of a short portion of the rib bone, which is overlain by meat which varies in thickness. There are two major types of cuts: The "flanken", which is cut across the bone and leaves the bone just 1 to 2 inches (2.5 to 5.1 cm) in length, and the "English", which is cut parallel to the bone and leaves the bone up to 6 inches (15 cm) in length. English cut short ribs may be served individually, or three or four may served connected to one another (a style known as the "plate"). Short ribs are popular in many international cuisines.

Spare ribs

Spare ribs (also side ribs or spareribs) are a variety of pork ribs cooked and eaten in various cuisines around the world. They are cut from the lower portion of

the pig specifically the belly and breastbone, behind the shoulder, and include 11 to 13 long bones. There is a covering of meat on top of the bones and also between them. Spare ribs (pork) are distinguished from short ribs, which are beef.

Standing rib roast

A standing rib roast, also known as prime rib, is a cut of beef from the primal rib, one of the nine primal cuts of beef. While the entire rib section comprises ribs six through 12, a standing rib roast may contain anywhere from two to seven ribs.

It is most often roasted "standing" on the rib bones so that the meat does not touch the pan. An alternative cut removes the top end of the ribs for easier carving.

Rib eye steaks are cut from a standing rib, boned with most of the fat and lesser muscles removed.

While often referred to as "prime rib", the USDA does not require the cut to be derived from USDA Prime grade beef.


In anatomy, a tubercle is any round nodule, small eminence, or warty outgrowth found on external or internal organs of a plant or an animal.

Vault (architecture)

In architecture, a vault (French voûte, from Italian volta) is a self-supporting arched form, usually of stone or brick, serving to cover a space with a ceiling or roof. The simplest kind of vault is the barrel vault (also called a wagon or tunnel vault), which is generally semicircular in shape. The barrel vault is a continuous arch, the length being greater than its diameter. As in building an arch, a temporary support is needed while rings of voussoirs are constructed and the rings placed in position. Until the topmost voussoir, the keystone, is positioned, the vault is not self-supporting. Where timber is easily obtained, this temporary support is provided by centering consisting of a framed truss with a semicircular or segmental head, which supports the voussoirs until the ring of the whole arch is completed. With a barrel vault, the centering can then be shifted on to support the next rings.The parts of a vault exert lateral thrust that requires a counter resistance. When vaults are built underground, the ground gives all the resistance required. However, when the vault is built above ground, various replacements are employed to supply the needed resistance. An example is the thicker walls used in the case of barrel or continuous vaults. Buttresses are used to supply resistance when intersecting vaults are employed.


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