The rib cage, as an enclosure that comprises the
rib
In vertebrate anatomy, ribs ( la, 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 ches ...
s,
vertebral column
The vertebral column, also known as the backbone or spine, is part of the axial skeleton. The vertebral column is the defining characteristic of a vertebrate in which the notochord (a flexible rod of uniform composition) found in all chordata, ...
and
sternum
The sternum 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 blood vessels from injury. Sh ...
in the
thorax
The thorax or chest is a part of the anatomy of humans, 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 divisions of the cre ...
of most
vertebrate
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, ...
s, protects
vital organ
In biology, an organ is a collection of tissues joined in a structural unit to serve a common function. In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to act together in a ...
s such as the
heart
The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide t ...
,
lung
The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of t ...
s and
great vessels
Great vessels are the large vessels that bring blood to and from the heart. These are:
*Superior vena cava
*Inferior vena cava
*Pulmonary arteries
*Pulmonary veins
*Aorta
Transposition of the great vessels is a group of congenital heart defect ...
.
The sternum, together known as the thoracic cage, is a semi-rigid
bony and
cartilaginous
Cartilage is a resilient and smooth type of connective tissue. In tetrapods, it covers and protects the ends of long bones at the joints as articular cartilage, and is a structural component of many body parts including the rib cage, the neck and ...
structure which surrounds the
thoracic cavity
The thoracic cavity (or chest cavity) is the chamber of the body of vertebrates that is protected by the thoracic wall (rib cage and associated skin, muscle, and fascia). The central compartment of the thoracic cavity is the mediastinum. There ...
and supports the
shoulder girdle
The shoulder girdle or pectoral girdle is the set of bones in the appendicular skeleton which connects to the arm on each side. In humans it consists of the clavicle and scapula; in those species with three bones in the shoulder, it consists of t ...
to form the
core
Core or cores may refer to:
Science and technology
* Core (anatomy), everything except the appendages
* Core (manufacturing), used in casting and molding
* Core (optical fiber), the signal-carrying portion of an optical fiber
* Core, the central ...
part of the
human skeleton
The human skeleton is the internal framework of the human body. It is composed of around 270 bones at birth – this total decreases to around 206 bones by adulthood after some bones get fused together. The bone mass in the skeleton makes up a ...
. A typical human thoracic cage consists of 12 pairs of ribs and the adjoining
costal cartilage
The costal cartilages are bars of hyaline cartilage that serve to prolong the ribs forward and contribute to the elasticity of the walls of the thorax. Costal cartilage is only found at the anterior ends of the ribs, providing medial extension.
...
s, the sternum (along with the
manubrium
The sternum 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 blood vessels from injury. Sha ...
and
xiphoid process
The xiphoid process , or xiphisternum or metasternum, is a small cartilaginous process (extension) of the inferior (lower) part of the sternum, which is usually ossified in the adult human. It may also be referred to as the ensiform process. Both ...
), and the 12
thoracic vertebra
In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebrae and they are intermediate in size between the cervical ...
e articulating with the ribs. Together with the
skin
Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation.
Other cuticle, animal coverings, such as the arthropod exoskeleton, have diffe ...
and associated
fascia
A fascia (; plural fasciae or fascias; adjective fascial; from Latin: "band") is a band or sheet of connective tissue, primarily collagen, beneath the skin that attaches to, stabilizes, encloses, and separates muscles and other internal organs. ...
and
muscle
Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...
s, the thoracic cage makes up the
thoracic wall
The thoracic wall or chest wall is the boundary of the thoracic cavity.
Structure
The bony skeletal part of the thoracic wall is the rib cage, and the rest is made up of muscle, skin, and fasciae.
The chest wall has 10 layers, namely (from s ...
and provides attachments for extrinsic
skeletal muscle
Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...
s of the
neck
The neck is the part of the body on many vertebrates that connects the head with the torso. The neck supports the weight of the head and protects the nerves that carry sensory and motor information from the brain down to the rest of the body. In ...
,
upper limb
The upper limbs or upper extremities are the forelimbs of an upright-postured tetrapod vertebrate, extending from the scapulae and clavicles down to and including the digits, including all the musculatures and ligaments involved with the shoulde ...
s,
upper abdomen
In anatomy, the epigastrium (or epigastric region) is the upper central region of the abdomen. It is located between the costal margins and the subcostal plane. Pain may be referred to the epigastrium from damage to structures derived from the f ...
and
back
The human back, also called the dorsum, is the large posterior area of the human body, rising from the top of the buttocks to the back of the neck. It is the surface of the body opposite from the chest and the abdomen. The vertebral column run ...
.
The rib cage intrinsically holds the
muscles of respiration
The muscles of respiration are the muscles that contribute to inhalation and exhalation, by aiding in the expansion and contraction of the thoracic cavity. The diaphragm and, to a lesser extent, the intercostal muscles drive respiration during q ...
(
diaphragm
Diaphragm may refer to:
Anatomy
* Thoracic diaphragm, a thin sheet of muscle between the thorax and the abdomen
* Pelvic diaphragm or pelvic floor, a pelvic structure
* Urogenital diaphragm or triangular ligament, a pelvic structure
Other
* Diap ...
,
intercostal muscles
Intercostal muscles are many different groups of muscles that run between the ribs, and help form and move the chest wall. The intercostal muscles are mainly involved in the mechanical aspect of breathing by helping expand and shrink the size ...
, etc.) that are crucial for active
inhalation
Inhalation (or Inspiration) happens when air or other gases enter the lungs.
Inhalation of air
Inhalation of air, as part of the cycle of breathing, is a vital process for all human life. The process is autonomic (though there are exceptions ...
and forced
exhalation
Exhalation (or expiration) is the flow of the breath out of an organism. In animals, it is the movement of air from the lungs out of the airways, to the external environment during breathing.
This happens due to elastic properties of the lungs, ...
, and therefore has a major
ventilatory function in the
respiratory system
The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies grea ...
.
Structure
![Gray 111 - Vertebral column-coloured](https://upload.wikimedia.org/wikipedia/commons/5/54/Gray_111_-_Vertebral_column-coloured.png)
There are thirty-three vertebrae in the human vertebral column. The rib cage is associated with TH1−TH12. Ribs are described based on their location and connection with the sternum. All ribs are attached posteriorly to the
thoracic vertebra
In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebrae and they are intermediate in size between the cervical ...
e and are numbered accordingly one to twelve. Ribs that articulate directly with the sternum are called ''true ribs'', whereas those that do not articulate directly are termed ''false ribs''. The ''false ribs'' include the ''floating ribs'' (eleven and twelve) that are not attached to the sternum at all.
Attachment
![Costillas](https://upload.wikimedia.org/wikipedia/commons/2/27/Costillas.png)
The terms ''true ribs'' and ''false ribs'' describe rib pairs that are directly or indirectly attached to the
sternum
The sternum 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 blood vessels from injury. Sh ...
respectively. The first seven rib pairs known as the ''fixed'' or vertebrosternal ribs are the ''true ribs'' ( la, costae verae) as they connect directly to the sternum; the next five pairs (eighth to twelfth) are the ''false ribs'' ( la, costae spuriae). The false ribs include both vertebrochondral ribs and vertebral ribs. There are three pairs of vertebrochondral ribs (eighth to tenth) that connect indirectly to the sternum via the costal cartilages of the ribs above them.
Their elasticity allows rib cage movement for respiratory activity.
The phrase ''floating rib'' or vertebral rib ( la, costae fluctuantes) refers to the two lowermost, the eleventh and twelfth rib pairs; so-called because they are attached only to the
vertebrae
The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic i ...
–and not to the sternum or cartilage of the sternum. These ribs are relatively small and delicate, and include a cartilaginous tip.
The spaces between the ribs are known as
intercostal space
The intercostal space (ICS) is the anatomic space between two ribs (Lat. costa). Since there are 12 ribs on each side, there are 11 intercostal spaces, each numbered for the rib superior to it.
Structures in intercostal space
* several kinds ...
s; they contain the intercostal
muscles
Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscle ...
, and
neurovascular bundle A neurovascular bundle is a structure that binds nerves and veins (and in some cases arteries and lymphatics) with connective tissue so that they travel in tandem through the body.
Structure
There are two types of neurovascular bundles: superficia ...
s containing
nerves
A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system.
A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...
,
arteries
An artery (plural arteries) () is a blood vessel in humans and most animals that takes blood away from the heart to one or more parts of the body (tissues, lungs, brain etc.). Most arteries carry oxygenated blood; the two exceptions are the pul ...
, and
veins
Veins are blood vessels in humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated b ...
.
Parts of rib
Each rib consists of a head, neck, and a shaft. All ribs are attached posteriorly to the
thoracic vertebrae
In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebra (anatomy), vertebrae and they are intermediate in size b ...
. They are numbered to match the vertebrae they attach to – one to twelve, from top (T1) to bottom. The head of the rib is the end part closest to the
vertebra
The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...
with which it
articulates. It is marked by a kidney-shaped articular surface which is divided by a horizontal crest into two articulating regions. The upper region articulates with the
inferior costal facet
The inferior costal facet (or inferior costal fovea) is a site where a rib forms a joint with the inferior aspect of the body of a thoracic vertebra.
In the adjacent picture, the arrow points to an inferior costal facet. The facets are named for ...
on the vertebra above, and the larger region articulates with the
superior costal facet
The superior costal facet (or superior costal fovea) is a site where a rib forms a joint with the top of a vertebra.
Ribs connect to the thoracic vertebrae at two main points, the inferior and superior costal facets. These connection points are l ...
on the vertebra with the same number. The transverse process of a thoracic vertebra also articulates at the
transverse costal facet
The transverse costal facet (or transverse costal fovea) is one of the costal facets, a site where a rib forms a joint with the transverse process of a thoracic vertebra.
References
External links
* - "The costovertebral joint
The costoverteb ...
with the tubercle of the rib of the same number. The crest gives attachment to the
intra-articular ligament.
[http://www.teachmeanatomy.com/osteology-of-the-thorax/]
The neck of the rib is the 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
A costotransverse ligament is a short fibrous band that connects a rib with the transverse process of vertebra. They are some of the ligaments that surround the costovertebral joint.
Types
There are three types of costotransverse ligaments in the ...
; its lower border is rounded.
On the posterior surface at the neck, is an eminence—the tubercle that consists of an articular and a non-articular portion. The articular portion is the lower and more medial of the two and presents a small, oval surface for articulation with the
transverse costal facet
The transverse costal facet (or transverse costal fovea) is one of the costal facets, a site where a rib forms a joint with the transverse process of a thoracic vertebra.
References
External links
* - "The costovertebral joint
The costoverteb ...
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.
The angle of a
rib
In vertebrate anatomy, ribs ( la, 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 ches ...
(costal angle) may both refer to the bending part of it, and a prominent line in this area, a little in front of the tubercle. This line is directed downward and laterally; this gives attachment to a tendon of the
iliocostalis muscle
Iliocostalis muscle is the muscle immediately lateral to the longissimus that is the nearest to the furrow that separates the epaxial muscles from the hypaxial. It lies very deep to the fleshy portion of the serratus posterior muscle. It laterall ...
. At this point, the rib is bent in two directions, and at the same time twisted on its long axis.
The distance between the angle and the tubercle is progressively greater from the second to the tenth ribs. The area between the angle and the tubercle is rounded, rough, and irregular, and serves for the attachment of the
longissimus dorsi muscle.
Bones
Ribs and vertebrae
The first rib (the topmost one) is the most curved and usually the shortest of all the ribs; it is broad and flat, its surfaces looking upward and downward, and its borders inward and outward.
File:Sobo 1909 24.png, First rib seen from above
File:Gray123.png, Costal groove position on a central rib
The ''head'' is small and rounded, and possesses only a single articular facet, for articulation with the body of the first
thoracic vertebra
In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebrae and they are intermediate in size between the cervical ...
. The ''neck'' is narrow and rounded. The ''tubercle'', thick and prominent, is placed on the outer border. It bears a small facet for articulation with the
transverse costal facet
The transverse costal facet (or transverse costal fovea) is one of the costal facets, a site where a rib forms a joint with the transverse process of a thoracic vertebra.
References
External links
* - "The costovertebral joint
The costoverteb ...
on the transverse process of T1. 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
The scalene tubercle is a small projection that runs along the medial border of the first rib between two grooves, which travel anteriorly for the subclavian artery and posteriorly for the subclavian vein. It projects outward medially, and is the s ...
, for the attachment of the
anterior scalene
The scalene muscles are a group of three pairs of muscles in the lateral neck, namely the anterior scalene, middle scalene, and posterior scalene. They are innervated by the third to the eight cervical spinal nerves (C3-C8).
The anterior and m ...
; the ''anterior groove'' transmits the
subclavian vein
The subclavian vein is a paired large vein, one on either side of the body, that is responsible for draining blood from the upper extremities, allowing this blood to return to the heart. The left subclavian vein plays a key role in the absorption ...
, the ''posterior ''the
subclavian artery
In human anatomy, the subclavian arteries are paired major arteries of the upper thorax, below the clavicle. They receive blood from the aortic arch. The left subclavian artery supplies blood to the left arm and the right subclavian artery supplie ...
and the lowest trunk of the
brachial plexus
The brachial plexus is a network () of nerves formed by the anterior rami of the lower four cervical nerves and first thoracic nerve ( C5, C6, C7, C8, and T1). This plexus extends from the spinal cord, through the cervicoaxillary canal in th ...
. Behind the posterior groove is a rough area for the attachment of the
medial scalene. The ''under surface'' is smooth and without a costal groove. The ''outer border'' is convex, thick, and rounded, and at its posterior part gives attachment to the first digitation of the
serratus anterior
The serratus anterior is a muscle that originates on the surface of the 1st to 8th ribs at the side of the chest and inserts along the entire anterior length of the medial border of the scapula. The serratus anterior acts to pull the scapula fo ...
. The ''inner border'' is concave, thin, and sharp, and marked about its center by the scalene tubercle. The ''anterior extremity'' is larger and thicker than that of any of the other ribs.
The second rib is the second uppermost rib in humans or second most frontal in animals that walk on four limbs. In humans, the second rib is defined as a true rib since it connects with the sternum through the intervention of the
costal cartilage
The costal cartilages are bars of hyaline cartilage that serve to prolong the ribs forward and contribute to the elasticity of the walls of the thorax. Costal cartilage is only found at the anterior ends of the ribs, providing medial extension.
...
anteriorly (at the front). Posteriorly, the second rib is connected with the
vertebral column
The vertebral column, also known as the backbone or spine, is part of the axial skeleton. The vertebral column is the defining characteristic of a vertebrate in which the notochord (a flexible rod of uniform composition) found in all chordata, ...
by the
second thoracic vertebra. The second rib is much longer than the
first rib
The rib cage, as an enclosure that comprises the ribs, vertebral column and sternum in the thorax of most vertebrates, protects vital organs such as the heart, lungs and great vessels.
The sternum, together known as the thoracic cage, is a semi-r ...
, but has a very similar curvature. The non-articular portion of the tubercle is occasionally only feebly marked. The angle is slight and situated close to the tubercle. 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. The body is not flattened horizontally like that of 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 internal surface, smooth, and concave, is directed downward and a little inward: on its posterior part there is a short costal groove between the ridge of the internal surface of the rib and the inferior border. It protects the intercostal space containing the
intercostal veins
The intercostal veins are a group of veins which drain the area between the ribs ("costae"), called the intercostal space.
They can be divided as follows:
* Anterior intercostal veins
* Posterior intercostal veins
** Posterior intercost vein that ...
,
intercostal arteries
The intercostal arteries are a group of arteries that supply the area between the ribs ("costae"), called the intercostal space. The highest intercostal artery (supreme intercostal artery or superior intercostal artery) is an artery in the human ...
, and
intercostal nerves
The intercostal nerves are part of the somatic nervous system, and arise from the anterior rami of the thoracic spinal nerves from T1 to T11. The intercostal nerves are distributed chiefly to the thoracic pleura and abdominal peritoneum, and diffe ...
.
[Moore, Dalley & Agur. 2009. ''Clinically Oriented Anatomy'', 6th Edition. 90 Pp. Lippincott, Williams & Wilkins, , ]
The ninth rib has a frontal part at the same level as the
first lumbar vertebra
The lumbar vertebrae are, in human anatomy, the five vertebrae between the rib cage and the pelvis. They are the largest segments of the vertebral column and are characterized by the absence of the foramen transversarium within the transverse ...
. This level is called the
transpyloric plane
The transpyloric plane, also known as Addison's plane, is an imaginary horizontal plane, located halfway between the suprasternal notch of the manubrium and the upper border of the symphysis pubis at the level of the first lumbar vertebrae, L1. It ...
, since the
pylorus
The pylorus ( or ), or pyloric part, connects the stomach to the duodenum. The pylorus is considered as having two parts, the ''pyloric antrum'' (opening to the body of the stomach) and the ''pyloric canal'' (opening to the duodenum). The ''pylori ...
is also at this level.
[Bålens ytanatomi (surface anatomy). Godfried Roomans, Mats Hjortberg and Anca Dragomir. Institution for Anatomy, Uppsala. 2008.]
The tenth rib attaches directly to the body of vertebra T10 instead of between vertebrae like the second through ninth ribs. Due to this direct attachment, vertebra T10 has a complete costal facet on its body.
![Skeleton woman back](https://upload.wikimedia.org/wikipedia/commons/f/f7/Skeleton_woman_back.png)
The eleventh and twelfth ribs, the floating ribs, have a single
articular facet
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- ...
on the head, which is of rather large size. They have no necks or tubercles, and are pointed at their anterior ends. The eleventh has a slight angle and a shallow costal groove, whereas the twelfth does not. The twelfth rib is much shorter than the eleventh rib, and only has a one articular facet.
Sternum
The sternum is a long,
flat bone
Flat bones are bones whose principal function is either extensive protection or the provision of broad surfaces for muscular attachment. These bones are expanded into broad, flat plates,''Gray's Anatomy'' (1918). (See infobox) as in the cranium ...
that forms the front of the rib cage. The cartilages of the top seven ribs (the ''true ribs'') join with the sternum at the sternocostal joints. The costal cartilage of the second rib articulates with the sternum at the sternal angle making it easy to locate.
The
transversus thoracis
The transversus thoracis muscle (), also known as triangularis sterni, lies internal to the thoracic cage, anteriorly. It is usually a thin plane of muscular and tendinous fibers, however on athletic individuals it can be a thick 'slab of meat', ...
muscle is innervated by one of the
intercostal nerves
The intercostal nerves are part of the somatic nervous system, and arise from the anterior rami of the thoracic spinal nerves from T1 to T11. The intercostal nerves are distributed chiefly to the thoracic pleura and abdominal peritoneum, and diffe ...
and superiorly attaches at the posterior surface of the lower sternum. Its inferior attachment is the internal surface of costal cartilages two through six and works to depress the ribs.
Development
Expansion of the rib cage in males is caused by the effects of
testosterone
Testosterone is the primary sex hormone and anabolic steroid in males. In humans, testosterone plays a key role in the development of Male reproductive system, male reproductive tissues such as testes and prostate, as well as promoting secondar ...
during puberty.
[Testosterone causes expansion of rib cage during puberty as one of secondary sex characteristics.] Thus, males generally have broad shoulders and expanded chests, allowing them to inhale more air to supply their muscles with oxygen.
Variation
Variations in the number of ribs occur. About 1 in 200–500 people have an additional
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% to 0.5% (1 in 200 to 500) of the ...
, and there is a female predominance.
Intrathoracic supernumerary ribs are extremely rare.
The rib remnant of the
7th cervical vertebra on one or both sides is occasionally replaced by a free extra rib called a
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% to 0.5% (1 in 200 to 500) of the ...
, which can mechanically interfere with the nerves (
brachial plexus
The brachial plexus is a network () of nerves formed by the anterior rami of the lower four cervical nerves and first thoracic nerve ( C5, C6, C7, C8, and T1). This plexus extends from the spinal cord, through the cervicoaxillary canal in th ...
) going to the arm.
In several ethnic groups, most significantly the Japanese, the tenth rib is sometimes a
floating rib
The rib cage, as an enclosure that comprises the ribs, vertebral column and sternum in the thorax of most vertebrates, protects vital organs such as the heart, lungs and great vessels.
The sternum, together known as the thoracic cage, is a semi-r ...
, as it lacks a cartilaginous connection to the seventh rib.
Function
![ribcage during inhalation](https://upload.wikimedia.org/wikipedia/commons/a/a0/Ribcage_during_inhalation.jpg)
The human rib cage is a component of the human
respiratory system
The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies grea ...
. It encloses the thoracic cavity, which contains the lungs. An inhalation is accomplished when the muscular
diaphragm
Diaphragm may refer to:
Anatomy
* Thoracic diaphragm, a thin sheet of muscle between the thorax and the abdomen
* Pelvic diaphragm or pelvic floor, a pelvic structure
* Urogenital diaphragm or triangular ligament, a pelvic structure
Other
* Diap ...
, at the floor of the thoracic cavity, contracts and flattens, while the contraction of
intercostal muscles
Intercostal muscles are many different groups of muscles that run between the ribs, and help form and move the chest wall. The intercostal muscles are mainly involved in the mechanical aspect of breathing by helping expand and shrink the size ...
lift the rib cage up and out.
Expansion of the thoracic cavity is driven in three planes; the vertical, the anteroposterior and the transverse. The vertical plane is extended by the help of the diaphragm contracting and the abdominal muscles relaxing to accommodate the downward pressure that is supplied to the abdominal viscera by the diaphragm contracting. A greater extension can be achieved by the diaphragm itself moving down, rather than simply the domes flattening. The second plane is the anteroposterior and this is expanded by a movement known as the '
pump handle'. The downward sloping nature of the upper ribs are as such because they enable this to occur. When the external intercostal muscles contract and lift the ribs, the upper ribs are able also to push the sternum up and out. This movement increases the anteroposterior diameter of the thoracic cavity, and hence aids breathing further. The third, transverse, plane is primarily expanded by the lower ribs (some say it is the 7th to 10th ribs in particular), with the diaphragm's central tendon acting as a fixed point. 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
Bucket-handle is a movement of ribs that results in change in transverse diameter of the thorax.
Definition
One of the most important functions of ribs and diaphragm is the change in volume of thorax that helps inspiration and expiration. In g ...
, facilitated by gliding at the
costovertebral joints
The costovertebral joints are the joints that connect the ribs to the vertebral column. The articulation of the head of the rib connects the head of the rib to the bodies of the thoracic vertebrae.
Structure
The costotransverse joint connects th ...
. In this way, the transverse diameter is expanded and the lungs can fill.
The circumference of the normal adult human rib cage expands by 3 to 5 cm during inhalation.
Clinical significance
Rib fracture
A rib fracture is a break in a rib bone. This typically results in chest pain that is worse with inspiration. Bruising may occur at the site of the break. When several ribs are broken in several places a flail chest results. Potential complicatio ...
s are the most common injury to the rib cage. These most frequently affect the middle ribs. When several adjacent ribs incur two or more fractures each, this can result in a
flail chest
Flail chest is a life-threatening medical condition that occurs when a segment of the rib cage breaks due to trauma and becomes detached from the rest of the chest wall. Two of the symptoms of flail chest are chest pain and shortness of breath.
...
which is a life-threatening condition.
A dislocated rib can be painful and can be caused simply by coughing, or for example by trauma or lifting heavy weights.
One or more costal cartilages can become inflamed – a condition known as
costochondritis
Costochondritis, also known as chest wall pain syndrome or costosternal syndrome, is a benign inflammation of the upper costochondral (rib to cartilage) and sternocostal (cartilage to sternum) joints. 90% of patients are affected in multiple ri ...
; the resulting pain is similar to that of a heart attack.
Abnormalities of the rib cage include
pectus excavatum
Pectus excavatum is a structural deformity of the anterior thoracic wall in which the sternum and rib cage are shaped abnormally. This produces a caved-in or sunken appearance of the chest. It can either be present at birth or develop after pubert ...
("sunken chest") and
pectus carinatum
Pectus carinatum, also called pigeon chest, is a malformation of the chest characterized by a protrusion of the sternum and ribs. It is distinct from the related malformation pectus excavatum.
Signs and symptoms
People with pectus carinatum usua ...
("pigeon chest"). A
bifid rib
A bifid rib is a congenital abnormality of the rib cage and associated muscles and nerves which occurs in about 1.2% of humans. Bifid ribs occur in up to 8.4% of Samoans. The sternal end of the rib is cleaved into two. It is usually unilateral. ...
is a bifurcated rib, split towards the sternal end, and usually just affecting one of the ribs of a pair. It is a
congenital defect
A birth defect, also known as a congenital disorder, is an abnormal condition that is present at childbirth, birth regardless of its cause. Birth defects may result in disability, disabilities that may be physical disability, physical, intellect ...
affecting about 1.2% of the population. It is often without symptoms though respiratory difficulties and other problems can arise.
Rib removal
Rib removal is surgery to remove one or more ribs. Rib resection is the removal of part of a rib. The procedures are done for various medical reasons. A number of celebrities have been falsely rumoured to have had ribs removed as a form of body mod ...
is the surgical removal of one or more ribs for therapeutic or cosmetic reasons.
Rib resection is the removal of part of a rib.
Regeneration
Since the early part of the 20th century, the ability of the human rib to regenerate itself has been appreciated.
However, scientific reports demonstrating repair have been sporadic and anecdotal. Currently, this phenomenon is best taken advantage of by craniomaxillofacial surgeons, who use both cartilage and bone material from the rib for jaw, face, and ear reconstruction.
The perichondrium is a fibrous sheath of vascular connective tissue surrounding the rib cartilage, containing a source of progenitor stem cells required for rib regeneration.
Society and culture
The position of ribs can be permanently altered by a form of
body modification
Body modification (or body alteration) is the deliberate altering of the human anatomy or human physical appearance. In its broadest definition it includes skin tattooing, socially acceptable decoration (''e.g.'', common ear piercing in many s ...
called
tightlacing
Tightlacing (also called corset training) is the practice of wearing a tightly-laced corset. It is done to achieve cosmetic modifications to the figure and posture or to experience the sensation of bodily restriction.
History
Corsets were first ...
, which uses a
corset
A corset is a support garment commonly worn to hold and train the torso into a desired shape, traditionally a smaller waist or larger bottom, for aesthetic or medical purposes (either for the duration of wearing it or with a more lasting effe ...
to compress and move the ribs.
The ribs, particularly their sternal ends, are used as a way of estimating age in
forensic pathology
Forensic pathology is pathology that focuses on determining the cause of death by examining a corpse. A post mortem examination is performed by a medical examiner or forensic pathologist, usually during the investigation of criminal law cases an ...
due to their progressive ossification.
Biblical Story
The number of ribs as 24 (12 pairs) was noted by the
Flemish
Flemish (''Vlaams'') is a Low Franconian dialect cluster of the Dutch language. It is sometimes referred to as Flemish Dutch (), Belgian Dutch ( ), or Southern Dutch (). Flemish is native to Flanders, a historical region in northern Belgium; ...
anatomist
Anatomy () is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old science, having its ...
Vesalius
Andreas Vesalius (Latinized from Andries van Wezel) () was a 16th-century anatomist, physician, and author of one of the most influential books on human anatomy, ''De Humani Corporis Fabrica Libri Septem'' (''On the fabric of the human body'' '' ...
in his key work of anatomy ''
De humani corporis fabrica
''De Humani Corporis Fabrica Libri Septem'' (Latin, lit. "On the fabric of the human body in seven books") is a set of books on human anatomy written by Andreas Vesalius (1514–1564) and published in 1543. It was a major advance in the history ...
'' in 1543, setting off a wave of controversy, as it was traditionally assumed from the Biblical story of
Adam and Eve
Adam and Eve, according to the creation myth of the Abrahamic religions, were the first man and woman. They are central to the belief that humanity is in essence a single family, with everyone descended from a single pair of original ancestors. ...
that men's ribs would number one fewer than women's. This false belief is still commonly believed today. However, thirteenth or “cervical rib” occurs in 1% of humans
and this is more common in females than in males.
Other animals
![Wankel Tyrannosaurus cast rib cage UCMP](https://upload.wikimedia.org/wikipedia/commons/c/c0/Wankel_Tyrannosaurus_cast_rib_cage_UCMP.JPG)
In
herpetology
Herpetology (from Greek ἑρπετόν ''herpetón'', meaning "reptile" or "creeping animal") is the branch of zoology concerned with the study of amphibians (including frogs, toads, salamanders, newts, and caecilians (gymnophiona)) and rept ...
, costal grooves refer to lateral indents along the integument of
salamander
Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All ten ...
s. The grooves run between the
axilla
The axilla (also, armpit, underarm or oxter) is the area on the human body directly under the shoulder joint. It includes the axillary space, an anatomical space within the shoulder girdle between the arm and the thoracic cage, bounded superior ...
to the
groin
In human anatomy, the groin (the adjective is ''inguinal'', as in inguinal canal) is the junctional area (also known as the inguinal region) between the abdomen and the thigh on either side of the pubic bone. This is also known as the medial comp ...
. Each groove overlies the myotomal septa to mark the position of the internal rib.
[J. W. Petranka. 1998. Salamanders of the United States and Canada. 587 Pp. Smithsonian Institution Press, , ]
Birds
Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...
and
reptiles
Reptiles, as most commonly defined are the animals in the Class (biology), class Reptilia ( ), a paraphyletic grouping comprising all sauropsid, sauropsids except birds. Living reptiles comprise turtles, crocodilians, Squamata, squamates (lizar ...
have bony
uncinate processes on their ribs that project caudally from the vertical section of each rib.
These serve to attach
sacral
Sacral may refer to:
*Sacred
Sacred describes something that is dedicated or set apart for the service or worship of a deity; is considered worthy of spiritual respect or devotion; or inspires awe or reverence among believers. The property ...
muscles and also aid in allowing greater inspiration.
Crocodile
Crocodiles (family (biology), family Crocodylidae) or true crocodiles are large semiaquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. The term crocodile is sometimes used even more loosely to inclu ...
s have cartilaginous uncinate processes.
Additional images
File:Thoracic Cage with Spine - Anatomy.gif, Thoracic cage with spine
File:Gray115.png, Anterior surface of sternum and costal cartilages
File:Ribs labeled.png, X-ray image of a human chest, with ribs labelled
File:BodyParts3D Rib cage.stl, 3D model of rib cage
File:Surface projections of the organs of the trunk.png, Surface projections of the trunk, including each rib, and the costal margin
File:Thoracic Cage with Both Humerii.gif, Thoracic cage with both humerii
See also
*
Articulation of head of rib
The articulations of the heads of the ribs (or costocentral articulations) constitute a series of gliding or arthrodial joints, and are formed by the articulation of the heads of the typical ribs with the costal facets on the contiguous margins ...
*
Rachitic rosary
The prominent knobs of bone at the costochondral joints of rickets patients are known as a rachitic rosary or beading of the ribs. The knobs create the appearance of large beads under the skin of the rib cage, hence the name by analogy with the bea ...
*
Terms for anatomical location
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...
*
Terms for bones
Notes
References
* ''Orientation of the intercostal muscle fibers in the human rib cage'', Subit D., Glacet A., Hamzah M., Crandall J., Computer Methods in Biomechanics and Biomedical Engineering, 2015, 18, pp. 2064–2065
* ''Clinically Oriented Anatomy'', 4th ed. Keith L. Moore and Robert F. Dalley. pp. 62–64
* ''Principles of Anatomy Physiology'', Tortora GJ and Derrickson B. 11th ED. John Wiley and Sons, 2006.
*
De Humani Corporis Fabrica': online English translation of Vesalius' books on human anatomy.
External links
{{DEFAULTSORT:Rib cage
Bones of the thorax