Rib

Source: Wikipedia, the free encyclopedia.
This article is about the part of the skeleton. For other uses, see Rib (disambiguation).
Rib
Collection of single ribs in the Faculty of Education of Charles University
Animation of all ribs, including the false ones in humans
Details
Identifiers
Latincostae
MeSHD012272
TA98A02.3.01.001
A02.3.02.001
TA21105, 1118
FMA7574
Anatomical terminology

In

vital organs of the thorax. In some animals, especially snakes
, ribs may provide support and protection for the entire body.

Human anatomy

Rib details

Human ribs are flat bones that form part of the rib cage to help protect internal organs. Humans usually have 24 ribs, in 12 pairs.[2] 1 in 500 people have an extra rib known as a cervical rib. People may have a cervical rib on the right, left or both sides.[3] All are attached at the back to the thoracic vertebrae and are numbered from 1 to 12 according to the vertebrae to which they attach. The first rib is attached to thoracic vertebra 1 (T1). At the front of the body, most of the ribs are joined by costal cartilage to the sternum. Ribs connect to vertebrae at the costovertebral joints.[4]

The parts of a rib includes 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.[5] 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 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.[5] 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

Main article: Rib cage
X-ray image of human chest, with ribs labelled

The first seven sets of ribs, known as "

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.[7]

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.

Development

Early in

sclerotome. The vertebrae and ribs develop from the sclerotomes.[8]

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.[8]

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.[8]

Other animals

Skeleton of a dog showing the location of the ribs
Rib cage of the big brown bat (Eptesicus fuscus)

In

jawed 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 ventral ribs, and only very short dorsal ribs. In some teleosts, there may be additional rib-like bones within the muscle mass.[9]

sacral ribs were stout and short, since they formed part of the pelvis, connecting the backbone to the hip bones.[9]

In most true tetrapods, many of these early ribs have been lost, and in living

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.[9]

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.[9]
Usually dogs have 26 ribs. Mammals usually also only have distinct ribs on the thoracic vertebra, although fixed cervical ribs are also present in
caudal ribs are never found in mammals.[9]

Ribs as food

Main article: Ribs (food)

Pork ribs, including spare ribs are popular in European and Asian cuisine
.

Animated images

  • Thoracic cage with spine
    Thoracic cage with spine

See also

Wikimedia Commons has media related to Ribs (skeleton).
Look up rib in Wiktionary, the free dictionary.

References

  1. ISBN 978-0-323-17281-3
    , retrieved 2020-11-03
  2. ^
    ISBN 978-0-323-04048-8
    , retrieved 2020-11-03
  3. S2CID 256899032
    .
  4. ISBN 9781496347213
    .
  5. ^
    ISBN 9781455704187
    .
  6. ISBN 978-0-323-04048-8
    , retrieved 2020-11-03
  7. ^ a b Saladin, K. S. (2010). Anatomy and Physiology: The Unity of Form and Function (5th ed.). New York, NY: McGraw-Hill.
  8. ^
    ISBN 0443065837
    .
  9. ^
    ISBN 0-03-910284-X
    .
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