In
human anatomyHuman anatomy, which, with physiology and biochemistry, is a complementary basic medical science is primarily the scientific study of the morphology of the adult human body. Anatomy is subdivided into gross anatomy and microscopic anatomy...
, the
vertebral column (
backbone or
spine) is a column usually consisting of 33
vertebraA vertebra is an individual bone in the flexible column that defines vertebrate animals, e.g. humans. The vertebral column encases and protects the spinal cord, which runs from the base of the cranium down the dorsal side of the animal until reaching the pelvis. From there, vertebra continue into...
e, the
sacrumThe sacrum is a large, triangular bone at the base of the spine and at the upper and back part of the pelvic cavity, where it is inserted like a wedge between the two hip bones. Its upper part connects with the last lumbar vertebra, and bottom part with the coccyx...
,
intervertebral discIntervertebral discs lie between adjacent vertebrae in the spine. Each disc forms a cartilaginous joint to allow slight movement of the vertebrae, and acts as a ligament to hold the vertebrae together.-Structure:...
s, and the
coccyxThe coccyx , commonly referred to as the tailbone, is the final segment of the human vertebral column. Comprising three to five separate or fused vertebrae below the sacrum, it is attached to the sacrum by a fibrocartilaginous joint, the sacrococcygeal symphysis, which permits limited movement...
situated in the
dorsalIn anatomy, the dorsum is the upper side of animals that typically run, fly, or swim in a horizontal position, and the back side of animals that walk upright. In vertebrates the dorsum contains the backbone. The term dorsal refers to anatomical structures that are either situated toward or grow...
aspect of the
torsoTorso is an anatomical term for the central part of the many animal bodies from which extend the neck and limbs. It is sometimes referred to as the trunk. The torso includes the thorax and abdomen.-Major organs:...
, separated by spinal discs. It houses the
spinal cordThe spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain. The brain and spinal cord together make up the central nervous system. It is around 45 cm long in men and around 43 cm long in women. The length of the spinal cord is much shorter than...
in its
spinal canalThe spinal canal is the space in vertebrae through which the spinal cord passes. It is a process of the dorsal human body cavity. This canal is enclosed within the vertebral foramen of the vertebrae...
.
Curves
Viewed laterally the vertebral column presents several curves, which correspond to the different regions of the column, and are called
cervicalIn vertebrates, cervical vertebrae are those vertebrae immediately inferior to the skull.-Variation among species:In some species, some parts of the skull may be composed of vertebra-like elements, e.g...
,
thoracicThe 12 thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. They are intermediate in size between those of the cervical and lumbar regions; they increase in size as one proceeds down the spine, the upper vertebrae being...
,
lumbarThe lumbar vertebrae are the largest segments of the movable part of the vertebral column, and are characterized by the absence of the foramen transversarium within the transverse process, and by the absence of facets on the sides of the body...
, and pelvic.
The cervical curve, convex forward, begins at the apex of the odontoid (
tooth-like) process, and ends at the middle of the second thoracic vertebra; it is the least marked of all the curves.
The thoracic curve, concave forward, begins at the middle of the second and ends at the middle of the twelfth thoracic vertebra. Its most prominent point behind corresponds to the spinous process of the seventh thoracic vertebra. This curve is known as a
tt curve.
The lumbar curve is more marked in the femaleFemale is the sex of an organism, or a part of an organism, which produces mobile ova .- Defining Characteristics :The ova are defined as the larger gametes in a heterogamous reproduction system, while the smaller, usually motile gamete, the spermatozoon, is produced by the male...
than in the maleMale refers to the sex of an organism, or part of an organism, which produces small mobile gametes, called spermatozoa. Each spermatozoon can fuse with a larger female gamete or ovum, in the process of fertilization...
; it begins at the middle of the last thoracic vertebra, and ends at the sacrovertebral angle. It is convex anteriorly, the convexity of the lower three vertebrae being much greater than that of the upper two. This curve is described as a lordotic curve
.
The pelvic curve begins at the sacrovertebral articulation, and ends at the point of the coccyxThe coccyx , commonly referred to as the tailbone, is the final segment of the human vertebral column. Comprising three to five separate or fused vertebrae below the sacrum, it is attached to the sacrum by a fibrocartilaginous joint, the sacrococcygeal symphysis, which permits limited movement...
; its concavity is directed downward and forward. .
The thoracic and pelvic curves are termed primary curves, because they alone are present during fetalA fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth. The plural is fetuses....
life. The cervical and lumbar curves are compensatory
or secondary, and are developed after
birthChildbirth is the culmination of a human pregnancy or gestation period with birth of one or more newborn infants from a woman's uterus...
, the former when the child is able to hold up its head (at three or four months) and to sit upright (at nine months), the latter at twelve or eighteen months, when the child begins to walk.
Names of individual vertebrae
There are a total of 33 vertebrae in the vertebral column, if assuming 4 coccygeal vertebrae.
The individual vertebrae, named according to region and position, from superior to inferior, are:
- Cervical: 7 vertebrae (C1–C7)
- C1 is known as "atlas" and supports the head, C2 is known as "axis"
- Possesses bifid spinous processes, which is absent in C1 and C7
- Small-bodied
- Thoracic: 12 vertebrae (T1–T12)
- Distinguished by the presence of costal facets for the articulation of the heads of ribs
- Body is intermediate in size between the cervical and lumbar vertebrae
- Lumbar: 5 vertebrae (L1–L5)
- Has a large body
- Does not have costal facets nor transverse process foramina
- Sacral: 5 (fused) vertebrae (S1–S5)
- Coccygeal: 4 (3–5) (fused) vertebrae (Tailbone)
Anterior surface
When viewed from in front, the width of the bodies of the vertebrae is seen to increase from the second cervical to the first thoracic; there is then a slight diminution in the next three vertebrae; below this there is again a gradual and progressive increase in width as low as the sacrovertebral angle. From this point there is a rapid diminution, to the apex of the coccyx.
Posterior surface
The posterior surface of the vertebral column presents in the median line the spinous processes. In the cervical region (with the exception of the second and seventh vertebrae) these are short and horizontal, with bifid extremities. In the upper part of the thoracic region they are directed obliquely downward; in the middle they are almost vertical, and in the lower part they are nearly horizontal. In the lumbar region they are nearly horizontal. The spinous processes are separated by considerable intervals in the lumbar region, by narrower intervals in the neck, and are closely approximated in the middle of the thoracic region. Occasionally one of these processes deviates a little from the median line — a fact to be remembered in practice, as irregularities of this sort are attendant also on fractures or displacements of the vertebral column. On either side of the spinous processes is the vertebral groove formed by the laminae in the cervical and lumbar regions, where it is shallow, and by the laminae and transverse processes in the thoracic region, where it is deep and broad; these grooves lodge the deep muscles of the back. Lateral to the vertebral grooves are the articular processes, and still more laterally the transverse processes. In the thoracic region, the transverse processes stand backward, on a plane considerably behind that of the same processes in the cervical and lumbar regions. In the cervical region, the transverse processes are placed in front of the articular processes, lateral to the pedicles and between the intervertebral foramina. In the thoracic region they are posterior to the pedicles, intervertebral foramina, and articular processes. In the lumbar region they are in front of the articular processes, but behind the intervertebral foramina.
Lateral surfaces
The lateral surfaces are separated from the posterior surface by the articular processes in the cervical and lumbar regions, and by the transverse processes in the thoracic region. They present, in front, the sides of the bodies of the vertebrae, marked in the thoracic region by the facets for articulation with the heads of the ribs. More posteriorly are the intervertebral foramina, formed by the juxtaposition of the vertebral notches, oval in shape, smallest in the cervical and upper part of the thoracic regions, and gradually increasing in size to the last lumbar. They transmit the spinal nerves and are situated between the transverse processes in the cervical region, and in front of them in the thoracic and lumbar regions.
T3 is at level of medial part of
spine of scapulaThe spine of the scapula is a prominent plate of bone, which crosses obliquely the medial four-fifths of the scapula at its upper part, and separates the supra- from the infraspinatous fossa....
. T7 is at
inferior angle of the scapulaThe inferior angle of the scapula, thick and rough, is formed by the union of the vertebral and axillary borders; its dorsal surface affords attachment to the Teres major and frequently to a few fibers of the Latissimus dorsi.-External links:...
. L3 is at highest point of
iliac crestThe crest of the ilium is the superior border of the wing of ilium and the superolateral margin of the greater pelvis.-Anatomy:...
. S2 is at the level of
posterior superior iliac spineThe posterior border of the ala, shorter than the anterior, also presents two projections separated by a notch, the posterior superior iliac spine and the posterior inferior iliac spine...
. T12 can be found by identifying the lowest pair of ribs and tracing them to their thoracic attachment. Furthermore, C7 is easily localized as a prominence at the lower part of the neck.
Vertebral canal
The vertebral canal follows the different curves of the column; it is large and triangular in those parts of the column which enjoy the greatest freedom of movement, such as the cervical and lumbar regions; and is small and rounded in the thoracic region, where motion is more limited.
Abnormalities
Occasionally the coalescence of the laminae is not completed, and consequently a cleft is left in the arches of the vertebrae, through which a protrusion of the spinal membranes (
dura materThe dura mater , or dura, is the outermost of the three layers of the meninges surrounding the brain and spinal cord. The other two meningeal layers are the pia mater and the arachnoid mater. The dura surrounds the brain and the spinal cord and is responsible for keeping in the cerebrospinal fluid...
and arachnoid), and generally of the spinal cordThe spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain. The brain and spinal cord together make up the central nervous system. It is around 45 cm long in men and around 43 cm long in women. The length of the spinal cord is much shorter than...
(medulla spinalis
) itself, takes place, constituting the malformation known as spina bifidaSpina bifida is a developmental birth defect caused by the incomplete closure of the embryonic neural tube. Some vertebrae overlying the spinal cord are not fully formed and remain unfused and open. If the opening is large enough, this allows a portion of the spinal cord to stick out through the...
. This condition is most common in the lumbosacral region, but it may occur in the thoracic or cervical region, or the arches throughout the whole length of the canal may remain incomplete.
The following abnormal curvatures may occur in some people:
- Kyphosis
Kyphosis also called "hunchback", in a general term, is a common condition of a curvature of the upper spine...
is an exaggerated kyphotic (posterior) curvature in the thoracic region. This produces the so-called "humpback" or "dowager's hump", a condition commonly observed in osteoporosis.
- Lordosis
Lordosis is a medical term used to describe an inward curvature of a portion of the vertebral column...
is an exaggerated lordotic (anterior) curvature of the lumbar region, "swayback". Temporary lordosis is common among pregnant women.
- Retrolisthesis
A retrolisthesis is a posterior displacement of one vertebral body with respect to the adjacent vertebrae to a degree less than a luxation . Clinically speaking, retrolisthesis is the opposite of spondylolisthesis . In the past this clinical pathology was also called a "retrospondylolisthesis"...
is a posterior displacement of one vertebral body with respect to the adjacent vertebral segment to a degree less than a luxation (dislocation).
- Scoliosis
Scoliosis is a medical condition in which a person's spine is curved from side to side, shaped like an "s", and may also be rotated. To adults it can be very painful. It is an abnormal lateral curvature of the spine...
, lateral curvature, is the most common abnormal curvature, occurring in 0.5% of the population. It is more common among femaleFemale is the sex of an organism, or a part of an organism, which produces mobile ova .- Defining Characteristics :The ova are defined as the larger gametes in a heterogamous reproduction system, while the smaller, usually motile gamete, the spermatozoon, is produced by the male...
s and may result from unequal growth of the two sides of one or more vertebrae. It can also be caused by pulmonary atelectasis (partial or complete deflation of one or more lobes of the lungs) as observed in asthma or pneumothorax.
See also
- Coccyx
The coccyx , commonly referred to as the tailbone, is the final segment of the human vertebral column. Comprising three to five separate or fused vertebrae below the sacrum, it is attached to the sacrum by a fibrocartilaginous joint, the sacrococcygeal symphysis, which permits limited movement...
- Low back pain
Low back pain is a common symptom of musculoskeletal disorders or of disorders involving the lumbar vertebrae and related soft tissue structures such as muscles, ligaments, nerves and intervertebral discs. It can be either acute, subacute or chronic in its clinical presentation...
- Vertebral subluxation
Vertebral subluxation is a chiropractic term that is used to describe myriad signs and symptoms thought to occur as a result of a misaligned or dysfunctional spinal segment...
- Retrolisthesis
A retrolisthesis is a posterior displacement of one vertebral body with respect to the adjacent vertebrae to a degree less than a luxation . Clinically speaking, retrolisthesis is the opposite of spondylolisthesis . In the past this clinical pathology was also called a "retrospondylolisthesis"...
- Spinal disc herniation
A spinal disc herniation , informally and misleadingly called a "slipped disc", is a medical condition affecting the spine, in which a tear in the outer, fibrous ring of an intervertebral disc allows the soft, central portion to bulge out...
- Scoliosis
Scoliosis is a medical condition in which a person's spine is curved from side to side, shaped like an "s", and may also be rotated. To adults it can be very painful. It is an abnormal lateral curvature of the spine...
- Spinal stenosis
Spinal stenosis is a medical condition in which the spinal canal narrows and compresses the spinal cord and nerves. This is usually due to the common occurrence of spinal degeneration that occurs with aging. It can also sometimes be caused by spinal disc herniation, osteoporosis or a tumor...
External links