Chapter II - Vertebral Column

Structure of Bone and Vertebral Column

The center of the bone is called medullary cavity, which contains the bone marrow. This bone marrow looks like blood with gritty and fatty particles and is responsible for the hematopoiesis (the process of formation and development of the various types of blood cells.) Bones of the extremities are the examples of long bones. Only the long bones are responsible for the production of blood.

The axial and appendicular portions of the skeleton, put together, have 206 bones. The axial section includes the bones of the skull, thorax, and vertebrae. The appendicular section comprises the bones of the shoulder, upper extremities, hips, and lower extremities. While the axial section forms the body cavities and provides protection for the internal organs, the appendicular section attaches to the axial section as appendages. The vertebral column of adult human being consists of 26 bones and supports the entire body. It also houses the spinal cord.

Detailed know how of the vertebral column is a must to understand the pathology associated with.

Vertebral Column

The adult vertebral (spinal) column consists of 26 bones that are grouped as follows:

• 7 cervical vertebrae in the neck
• 12 thoracic vertebrae that articulate with the 12 pairs of ribs
• 5 lumbar vertebrae of the lower back
• 1 sacrum which is actually a fusion of 5 sacral vertebrae
• 1 coccyx or "tailbone" which is a fusion of 4 coccygeal vertebrae

Intervertebral discs are located between adjacent vertebrae. These fibrocartilage discs form strong joints and absorb spinal compression shock.

Various spinal disorders include:

• Herniated (slipped) disc - protrusion or rupture of an intervertebral disc
• Scoliosis - exaggerated lateral bending of spinal column
• Kyphosis - "hunchback" exaggerated thoracic curvature
• Lordosis - "swayback" exaggerated lumbar curvature
• Spina bifida - congenital defect with incomplete closure of the vertebral column

The first seven vertebrae referred to as the cervical vertebrae make the support framework for the neck. The first cervical vertebra, called atlas, supports the skull, and the second cervical vertebra, called axis, makes the rotation of the skull possible.

Thoracic vertebrae, 12 in toto, are located below the cervical vertebrae and support the chest while also working as the articulation points for the ribs. The five lumbar vertebrae support most of the weight of the torso. The 5 sacral vertebrae fused in to a single bone are situated below that and are together referred to as the sacrum. The Last 4 or 5 fragments are fused together to form the tail of the spinal column, known as coccyx.

Two adjacent vertebrae are separated by a disk interposed between them known as the intervertebral disk. It is composed of an outer fibrous part that surrounds a central gelatinous material known as the nucleus pulposus.

Epidural anesthesia, often used in obstetrics, is injected into the sacrum at the sacral hiatus.

In a lumbar puncture or spinal tap, spinal fluid is removed using a long needle inserted between L3-L4 or L4-L5.