Classification of Skeleton: Axial-2

Sutures of the Skull

The sutures, which keep the skull bones together, are immovable joints between the skull bones. There are four major sutures in the skull.

• Coronal suture: The frontal bone and the two parietal bones are connected by the coronal suture. The suture runs downhill and is produced as it crosses the cranial vault from side to side.
• Sagittal suture: The two parietal bones are joined by the sagittal suture.
• Frontal suture: Between 3 and 8% of people occasionally have this. It unites the two parts of the frontal bone and is located in the midline region.
• Lambdoid suture: The lambdoid suture connects the two parietal bones to the occipital bone in the back. It crosses the cerebral vault moving forward and downward.

Vertebral Column:

The vertebrae, or individual bones that make up the vertebral (spinal) column, or spine (singular vertebra). There are 26 vertebrae in an adult's vertebral column. There are 33 vertebrae altogether before the sacral and coccygeal vertebrae fuse. It can be rotated on itself and is both robust and flexible. It supports the head, encloses and safeguards the spinal cord, and acts as an attachment point for the back's ribs and muscles. It makes up 2/5 of the body's height and is an average of 61 cm for women and 71 cm for men. It physically supports the skull and trunk, enables movement, and takes the strain of lifting large objects, sprinting, and walking. Additionally, it offers a point of attachment for the muscles that support posture, the thoracic cage, and the extremities. 24 distinct, moveable, uneven bones make up the vertebral column, together with a sacrum (five fused bones), and a coccyx (four fused bones).

• Cervical vertebrae in the neck -7
• Thoracic vertebrae in the chest -12
• Lumber vertebrae in the lower back-5
• Sacrum (fused)-5
• Coccyx(fused)-4

Characteristics of Typical Vertebra:

All vertebrae share similar structural characteristics, with the exception of the first two cervical vertebrae. As the spinal column descends to the sacrum, the vertebrae gradually enlarge, before gradually shrinking as they approach the top of the coccyx. A vertebral arch, a body, and many processes make up a vertebrate.

Each vertebra is made up of a body in the front and a vertebral arch in the back. The vertebral body is substantial and essentially cylindrical. The area that supports weight is the disc-shaped body. The vertebral arch is located behind the body and is made up of laminae and two pedicles, one on each side (right and left). In the midline, pedicles and laminae combine. The vertebral foramen is an aperture created by the body and vertebral arch. The vertebral canal, which serves as the spinal cord's route, is formed by all of the vertebral foramen. A bony neural arch with two segments on each side surrounds the foramen. The intervertebral foramen, which is present when two vertebrae are connected, is a space between their pedicles. The spinal nerve can pass through as a result. The vertebral arch of normal vertebrae gives rise to a number of processes. They consist of four articular processes, two transverse processes, and one median spinous process (two superior and two inferior). The names of the vertebrae identify where they are along the spinal column.

There are 5 lumber vertebrae, 5 sacral vertebrae fused into 1 sacrum, 7 cervical vertebrae, 12 thoracic vertebrae, 4 to 5 small coccygeal vertebrae fused into 1 соссуx.

• Cervical Vertebrae:
  • The shortest and lightest vertebrae are those in the cervical region (C1–C7). The unique structural features of the first two, C1 and C2, enable head motions. The atlas, a bony ring, is the first cervical vertebra. The dens is a projection on the second cervical vertebra, which has a tiny body and the name axis (which means pivot). The dens (odontoid process) forms the axis of rotation for the skull and C1 when it passes through a canal in the first cervical vertebrae. A transverse ligament separates the atlas cavity into two portions: the larger, posterior portion transmits the spinal cord, while the smaller, anterior portion receives the axis dens.
  • The vertebral prominent, a very noticeable spinous process, is found on the seventh vertebra. Each transverse process of each of the seven cervical vertebrae has a noticeable circular transverse foramen. The vertebral anterior, which supplies blood to the brain, can travel through and is protected by these foramina. The body of the cervical vertebrae is narrower and wider than the anterio-posterior (A-P) plane, with a concave superior surface and convex inferior surface. The C3-C7 spine has a bifid spinous process. The cervical vertebrae C1, C2, and C7 are unusual.
• Thoracic Vertebrae:
  • The thoracic vertebrae number 12 (T1 and T12). Compared to cervical vertebrae, they are stronger and bigger. The ribs are partially attached by their transverse processes. The laminae are extremely thick and broad, and the bodies and transverse processes feature facets that articulate T1–T12 with ribs. They allow some movement of the spine in the thoracic ar by articulating with the ribs. T1-T4 and T9-T12 are atypical thoracic vertebrae, while T5-T8 are usual. Atypical thoracic vertebrae share several characteristics with cervical and lumbar vertebrae.
  • Typical features of thoracic vertebrae:
  • Heart-shaped body.
  • Circular and smaller than cervical and lumbar, the vertebral foramen is round.
  • The transverse process is robust and lengthy.
  • The sipnous process is lengthy and slopes backward.

• Lumber Vertebrae:
  • The largest and most powerful vertebrae, the lumber vertebrae (L1-L5) are designed for the connection of the back muscles. They enable the spine to flex forward and backward and support the back muscles. Lumber vertebrae are larger than thoracic vertebrae and do not have articular costal surfaces for rib attachment. L1 and L5 are abnormal lumbar vertebrae, whereas L2-L4 are usual.
  • Typical feature of lumbar vertebrae:
  • Massive and kidney-shaped body.
  • The triangular vertebral foramen is larger than the thoracic vertebrae.
  • Long and slender transverse processes are present.
  • Spinous processes are strong, brief processes.

• Sacrum:
  • The sacrum is a triangle bone with a downward-pointing apex that is located below the fifth lumber vertebra. Five sacral vertebrae combine to form the sacrum (S1 - S5). Between the two hip bones is the sacrum. The sacral promontory is the name for the protruding tip at the upper anterior edge of the body. It provides strength and stability to the pelvis and supports the spinal column. The vertebral canal continues as the sacral canal in the sacrum. The cauda equina, a bundle of spinal nerve roots ascending below the L1 vertebra, is contained inside it. There are normally four pairs of sacral foramina for the departure of spinal nerve rami on the pelvic and posterior sides of the sacrum, in between its vertebral components. The base of the sacrum is formed by the superior surface of the S1 vertebra. The apex of the sacrum, its tapering inferior end, has an oval facet for articulation with the coccyx.
• Coccyx:
  • The coccyx is connected to the tip of the sacrum and is made up of the fusion of four primitive coccygeal vertebrae. The coccyx points inferiorly in females during vaginal delivery to facilitate the passage of a baby.