The articular processes or zygapophyses (Greek ζυγον = "yoke" (because it links two vertebrae) + απο = "away" + φυσις = "process") of a vertebra, are projections of the vertebra that serve the purpose of fitting with an adjacent vertebra. The actual region of contact is called the articular facet.
Articular processes spring from the junctions of the pedicles and laminæ, and there are two right and left, and two superior and inferior. These stick out of an end of a vertebra to lock with a zygapophysis on the next vertebra, to make the backbone more stable.
The articular surfaces are coated with hyaline cartilage.
In the cervical vertebral column, the articular processes collectively form the articular pillars. These are the bony surfaces palpated just lateral to the spinous processes.
A cervical vertebra. (Superior and inferior processes labeled at right.)
A thoracic vertebra. (Superior labeled at top; inferior labeled at bottom.)
|Latin||Processus articularis inferior vertebrae, |
processus articularis superior vertebrae
|Anatomical terms of bone|
The capsules of the atlantooccipital articulation surround the condyles of the occipital bone, and connect them with the articular processes of the atlas: they are thin and loose.Epachthosaurus
Epachthosaurus (meaning "heavy lizard") was a genus of dinosaur from the Late Cretaceous. It was a titanosaurid sauropod. Its fossils have been found in Central and Northern Patagonia in South America.Facet joint
The facet joints, (or zygapophysial joints, zygapophyseal, apophyseal, or Z-joints) are a set of synovial, plane joints between the articular processes of two adjacent vertebrae. There are two facet joints in each spinal motion segment and each facet joint is innervated by the recurrent meningeal nerves.
The biomechanical function of each pair of facet joints is to guide and limit movement of the spinal motion segment. In the lumbar spine, for example, the facet joints function to protect the motion segment from anterior shear forces, excessive rotation and flexion. Facet joints appear to have little influence on the range of side bending (lateral flexion). These functions can be disrupted by degeneration, dislocation, fracture, injury, instability from trauma, osteoarthritis, and surgery.
In the thoracic spine the facet joints function to restrain the amount of flexion and anterior translation of the corresponding vertebral segment and function to facilitate rotation. Cavitation of the synovial fluid within the facet joints is responsible for the popping sound (crepitus) associated with manual spinal manipulation, commonly referred to as "cracking the back."
The facet joints, both superior and inferior, are aligned in a way to allow flexion and extension, and to limit rotation. This is especially true in the lumbar spine.Gigantophis
Gigantophis garstini is an extinct giant snake. Before the Paleocene constrictor genus Titanoboa was described from Colombia in 2009, Gigantophis was regarded as the largest snake ever recorded. Gigantophis lived about 40 million years ago during the Eocene epoch, and in the Paleogene Period within the northern Sahara, where Egypt and Algeria are now located.Graciliraptor
Graciliraptor (meaning "graceful thief") is a genus of theropod dinosaur from the early Cretaceous Period. It is a microraptorine dromaeosaurid.
The type species Graciliraptor lujiatunensis was first named and described in 2004 by Xu Xing and Wang Xiaoling. The generic name is derived from Latin gracilis and raptor. The specific name refers to the village Lujiatun where the fossil site is located. Its fossil, holotype IVPP V 13474, was found in Beipiao, Liaoning Province, China.Jiyuanitectum
Jiyuanitectum is an extinct genus of chroniosuchian tetrapod from the Late Permian Shangshihezi Formation of China. It is known from a single bony scute from Jiyuan in Henan province, ascribed to the type species Jiyuanitectum flatum in 2014. Plate-like scutes, which formed armor-like coverings on the backs of chroniosuchians, are the most commonly found chroniosuchian remains. They are also the most informative when it comes to distinguishing between species due to small variations in scute anatomy between different taxa. For example, a shallow groove along the midline of the scute is unique to Jiyuanitectum. The flatness of the scute is another unusual characteristic, giving it the species name flatum. Jiyuanitectum shares several features in common with the chroniosuchians Synesuchus and Bystrowiella, including the upper surface of the scute being covered in ridges that are mostly oriented perpendicular to the midline, and the absence of a bony projection on the front of the scute called the anteromedial articular processes, which is seen in other chroniosuchians. These features suggest that Jiyuanitectum belongs to the family Bystrowianidae. The narrowness of the scute suggests that it may be one of the most basal members of the group.The scute of Jiyuanitectum was found within a diverse Late Permian fossil assemblage in Jiyuan that includes abundant remains of the pareiasaur Shihtienfenia as well as fossils of two other chroniosuchian species: Bystrowiana sinica and Dromotectum largum. Therapsid remains are also known from the assemblage.Ligamenta flava
The ligamenta flava (singular, ligamentum flavum, Latin for yellow ligament) are ligaments of the spine.
They connect the laminae of adjacent vertebrae, all the way from the second vertebra, axis, to the first segment of the sacrum. They are best seen from the interior of the vertebral canal; when looked at from the outer surface they appear short, being overlapped by the lamina of the vertebral arch.
Each ligament consists of two lateral portions which commence one on either side of the roots of the articular processes, and extend backward to the point where the laminae meet to form the spinous process; the posterior margins of the two portions are in contact and to a certain extent united, slight intervals being left for the passage of small vessels. Each consists of yellow elastic tissue, the fibers of which, almost perpendicular in direction, are attached to the anterior surface of the lamina above, some distance from its inferior margin, and to the posterior surface and upper margin of the lamina below.
In the neck region the ligaments are thin, but broad and long; they are thicker in the thoracic region, and thickest in the lumbar region.Longissimus
The longissimus (Latin for 'the longest one') is the muscle lateral to the semispinalis muscles. It is the longest subdivision of the erector spinae muscles that extends forward into the transverse processes of the posterior cervical vertebrae.Lumbar vertebrae
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 process (since it is only found in the cervical region) and by the absence of facets on the sides of the body (as found only in the thoracic region). They are designated L1 to L5, starting at the top. The lumbar vertebrae help support the weight of the body, and permit movement.Mnyamawamtuka
Mnyamawamtuka (pronounced Mm-nya-ma-wah-mm-too-ka; meaning "beast of the Mtuka river drainage" in Kiswahili) is a genus of lithostrotian titanosaur dinosaur from the Late Cretaceous Galula Formation in Tanzania. The type and only species is M. moyowamkia.Multifidus muscle
The multifidus (multifidus spinae : pl. multifidi ) muscle consists of a number of fleshy and tendinous fasciculi, which fill up the groove on either side of the spinous processes of the vertebrae, from the sacrum to the axis. While very thin, the Multifidus muscle plays an important role in stabilizing the joints within the spine. The multifidus is one of the transversospinales.
Located just superficially to the spine itself, the multifidus muscle spans three joint segments and works to stabilize these joints at each level.
The stiffness and stability makes each vertebra work more effectively, and reduces the degeneration of the joint structures caused by friction from normal physical activity.
These fasciculi arise:
in the sacral region: from the back of the sacrum, as low as the fourth sacral foramen, from the aponeurosis of origin of the sacrospinalis, from the medial surface of the posterior superior iliac spine, and from the posterior sacroiliac ligaments.
in the lumbar region: from all the mamillary processes.
in the thoracic region: from all the transverse processes.
in the cervical region: from the articular processes of the lower four vertebrae.Each fasciculus, passing obliquely upward and medially, is inserted into the whole length of the spinous process of one of the vertebræ above.
These fasciculi vary in length: the most superficial, the longest, pass from one vertebra to the third or fourth above; those next in order run from one vertebra to the second or third above; while the deepest connect two adjacent vertebrae.
The multifidus lies deep relative to the spinal erectors, transverse abdominis, abdominal internal oblique muscle and abdominal external oblique muscle.Pars interarticularis
The pars interarticularis, or pars for short, is the part of a vertebra located between the inferior and superior articular processes of the facet joint.In the transverse plane, it lies between the lamina and pedicle. In other words, in the axial view, it is the bony mass between the facets that is anterior to the lamina and posterior to the pedicle. It is abnormal in spondylolysis, either due to fracture or congenitally. Bilateral C2 pars fractures are known as a variant of the hangman's fracture.
On an anterior oblique radiograph of the lumbar spine, the pars is the neck of the imaginary Scottie dog; the Scottie dog's eye is the pedicle, its hindlegs the spinous process, its nose the transverse process, its ear the superior articular facet and its forelegs the inferior articular facet.Stress fractures of the pars interarticularis are known to be associated with playing sports such as volleyball, although the mechanism is somewhat unclear. Patients with spina bifida occulta have an increased risk for spondylolysis.Posterior branches of the lumbar nerves
The posterior branches of the lumbar nerves branch from the dorsal rami of the lumbar nerves.Process (anatomy)
In anatomy, a process (Latin: processus) is a projection or outgrowth of tissue from a larger body. For instance, in a vertebra, a process may serve for muscle attachment and leverage (as in the case of the transverse and spinous processes), or to fit (forming a synovial joint), with another vertebra (as in the case of the articular processes). The word is used even at the microanatomic level, where cells can have processes such as cilia or pedicels. Depending on the tissue, processes may also be called by other terms, such as apophysis, tubercle, or protuberance.Sacrum
The sacrum ( or ; plural: sacra or sacrums), in human anatomy, is a large, triangular bone at the base of the spine that forms by the fusing of sacral vertebrae S1–S5 between 18 and 30 years of age.The sacrum is situated at the upper, back part of the pelvic cavity, between the two wings of the pelvis. It forms joints with four other bones. The two projections at the sides of the sacrum are called the alae (wings), and articulate with the ilium at the L-shaped sacroiliac joints. The upper part of the sacrum connects with the last lumbar vertebra, and its lower part with the coccyx (tailbone) via the sacral and coccygeal cornua.
The sacrum has three different surfaces which are shaped to accommodate surrounding pelvic structures. Overall it is concave (curved upon itself). The base of the sacrum, the broadest and uppermost part, is tilted forward as the sacral promontory internally. The central part is curved outward toward the posterior, allowing greater room for the pelvic cavity.
In all other quadrupedal vertebrates, the pelvic vertebrae undergo a similar developmental process to form a sacrum in the adult, even while the bony tail (caudal) vertebrae remain unfused. The number of sacral vertebrae varies slightly. For instance, the S1–S5 vertebrae of a horse will fuse, the S1–S3 of a dog will fuse, and four pelvic vertebrae of a rat will fuse between the lumbar and the caudal vertebrae of its tail. The Stegosaurus dinosaur had a greatly enlarged neural canal in the sacrum, characterized as a "posterior brain case”.Semispinalis muscles
The semispinalis muscles are a group of three muscles belonging to the transversospinales. These are the semispinalis capitis, the semispinalis cervicis and the semispinalis thoracis.
The semispinalis capitis (complexus) is situated at the upper and back part of the neck, deep to the splenius, and medial to the longissimus cervicis and longissimus capitis. It arises by a series of tendons from the tips of the transverse processes of the upper six or seven thoracic and the seventh cervical vertebrae, and from the articular processes of the three cervical vertebrae above this (C4-C6).
The tendons, uniting, form a broad muscle, which passes upward, and is inserted between the superior and inferior nuchal lines of the occipital bone. It lies deep to the trapezius muscle and can be palpated as a firm round muscle mass just lateral to the cervical spinous processes.
The semispinalis cervicis (or semispinalis colli), arises by a series of tendinous and fleshy fibers from the transverse processes of the upper five or six thoracic vertebrae, and is inserted into the cervical spinous processes, from the axis to the fifth cervical vertebrae inclusive. The semispinalis cervicis is thicker than the semispinalis thoracis. The fasciculus connected with the axis is the largest, and is chiefly muscular in structure.
The semispinalis thoracis (or semispinalis dorsi) muscle consists of thin, narrow, fleshy fasciculi, interposed between tendons of considerable length. It arises by a series of small tendons from the transverse processes of the sixth to the tenth thoracic vertebrae, and is inserted, by tendons, into the spinous processes of the upper four thoracic and lower two cervical vertebrae.
The semispinalis muscles are innervated by the dorsal rami of the cervical spinal nerves.Smith fracture
A Smith Fracture is a named vertebral fracture occurring most commonly in the lumbar spine. It is similar to that of a Chance fracture and is associated with seat belt injuries. This fracture represents a fracture through the posterior elements including the superior articular processes but not the spinous process, as well as an avulsion fracture of the vertebral body. This fracture is not to be confused with the more commonly referred to Smith's fracture of the wrist.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 vertebrae and they are intermediate in size between the cervical and lumbar vertebrae; they increase in size going towards the lumbar vertebrae, with the lower ones being a lot larger than the upper. They are distinguished by the presence of facets on the sides of the bodies for articulation with the heads of the ribs, as well as facets on the transverse processes of all, except the eleventh and twelfth, for articulation with the tubercles of the ribs. By convention, the human thoracic vertebrae are numbered T1–T12, with the first one (T1) located closest to the skull and the others going down the spine toward the lumbar region.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 chordates has been replaced by a segmented series of bone: vertebrae separated by intervertebral discs. The vertebral column houses the spinal canal, a cavity that encloses and protects the spinal cord.
There are about 50,000 species of animals that have a vertebral column. The human vertebral column is one of the most-studied examples.