In order from top to bottom how many vertebrae are in each section of the spinal column

The human spine is a complex anatomic structure that is the scaffolding for the entire body. It provides several important functions, including:

• Protecting the spinal cord and nerves
• Structural support for the body, allowing us to stand upright. The spine supports about half the weight of the body.

The average person is born with 33 individual bones (the vertebrae) that interact and connect with each other through flexible joints called facets. By the time a person becomes an adult most have only 24 vertebrae because some vertebrae at the bottom end of the spine fuse together during normal growth and development. Sometimes a person may have an additional vertebra, which is called a transitional body and is usually found at the sixth level of the lumbar area (labeled L6).

The bottom of the spine is called the sacrum. It is made up of several vertebral bodies usually fused together as one. The remaining small bones or ossicles below the sacrum are also fused together and called the tailbone or coccyx. The spine above the sacrum consists of:

The spinal column combines strong bones, unique joints, flexible ligaments and tendons, large muscles and highly sensitive nerves. While many of us take the benefits of a healthy spine for granted, spinal pain is a sharp reminder of how much we depend on our back in daily life. Some causes of spinal pain include:

• Irritation of the large nerves as they exit the bony confines of the spine leading to the arms and legs
• Irritation of the smaller nerves of the spine that involve innervate or supply the discs between the vertebrae, facets and ligaments
• Strain of the large muscles of the back that hold the spine upright
• Injuries to the bones, ligaments or joints
• Damage or disease to the discs that separate the vertebrae
• Abnormal movement between segments
• Tumors, infection, trauma, deformity or other spinal disorders

The spinal column is made up of many parts, all designed to help the back move flexibly, support body weight and protect the spinal cord and nerves. These parts include the:

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The regions of the spine consist of the cervical, thoracic, lumbar, and sacral.

Cervical Spine

The neck region of the spine is known as the Cervical Spine. This region consists of seven vertebrae, which are abbreviated C1 through C7 (top to bottom). These vertebrae protect the brain stem and the spinal cord, support the skull, and allow for a wide range of head movement.

The first cervical vertebra (C1) is called the Atlas. The Atlas is ring-shaped and it supports the skull. C2 is called the Axis. It is circular in shape with a blunt tooth-like structure (called the Odontoid Process or dens) that projects upward into the Atlas. Together, the Atlas and Axis enable the head to rotate and turn. The other cervical vertebrae (C3 through C7) are shaped like boxes with small spinous processes (finger-like projections) that extend from the back of the vertebrae.

1. Spinous Process
2. Lamina
3. Zygapophysial Joint (Facet)
4. Posterior Tubercle
5. Foramen
6. Pedicle
7. Body

Thoracic Spine

Beneath the last cervical vertebra are the 12 vertebrae of the Thoracic Spine. These are abbreviated T1 through T12 (top to bottom). T1 is the smallest and T12 is the largest thoracic vertebra. The thoracic vertebrae are larger than the cervical bones and have longer spinous processes.

In addition to longer spinous processes, rib attachments add to the thoracic spine’s strength. These structures make the thoracic spine more stable than the cervical or lumbar regions. In addition, the rib cage and ligament system limit the thoracic spine’s range of motion and protects many vital organs.

1. Spinous Process
2. Lamina
3. Zygapophysial Joint (Facet)
4. Posterior Tubercle
5. Foramen
6. Pedicle
7. Body

Lumbar Spine

The Lumbar Spine has 5 vertebrae abbreviated L1 through L5 (largest). The size and shape of each lumbar vertebra is designed to carry most of the body’s weight. Each structural element of a lumbar vertebra is bigger, wider and broader than similar components in the cervical and thoracic regions.

1. Body
2. Spinous Process
3. Articular Process
4. Transverse Process
5. Foramen
6. Pedicle
7. Body

The lumbar spine has more range of motion than the thoracic spine, but less than the cervical spine. The lumbar facet joints allow for significant flexion and extension movement but limits rotation.

Sacral Spine

The Sacrum is located behind the pelvis. Five bones, abbreviated S1 through S5, fused into a triangular shape, form the sacrum. The sacrum fits between the two hip bones connecting the spine to the pelvis. The last lumbar vertebra (L5) articulates (moves) with the sacrum.

Immediately below the sacrum are five additional bones, fused together to form the Coccyx (tailbone).

The spinal column and vertebrae are made of different elements, all of which protect the spinal cord while communicating with the brain. These elements also provide sensations through the body via a complex interaction of the bones, ligaments and muscle structures of the back and the nerves that surround it.

Sections

The spine is composed of 33 bones, called vertebrae, divided into five sections: the cervical, thoracic, and lumbar spine sections, and the sacrum and coccyx bones.

The cervical section of the spine is made up of the top seven vertebrae in the spine, C1 to C7, and is connected to the base of the skull. The top two vertebrae are also know as the atlas and axis, which form the joint for connecting the skull to the spine. The cervical section is responsible for mobility and normal functioning of the neck, as well as protection of the spinal cord, arteries and nerves that travel from the brain to the body.

The thoracic section of the spine is located at chest level, between the cervical and lumbar vertebrae. The vertebrae in this section are labeled T1 to T12 and serve as attachments for the rib cage.

The lumbar section is located between the thoracic vertebrae and the sacrum. The five lumbar vertebrae, labeled L1 to L5, are the main weight-bearing section of the spinal column.

The sacrum is the section located at the base of the spine. It does not have discs separating the vertebrae, because its five levels, S1 to S5, are fused together. The pelvis is connected to the spinal column at the sacrum section.

The coccyx is at the very base of the spinal column and is made of four vertebrae that are fused together.

Spinal Curvature

Scoliosis

The spine is normally a straight line when viewed from the back. If the spine curves to one side or the other, this indicates a condition named scoliosis.

However, the spine does have some normal, gradual curves when viewed from the side. The neck and lumbar sections of the spine have a lordotic curve, which means that they curve inward.

The thoracic spine has a kyphotic curve, which means that it curves outward.

These spinal curves help maintain balance while upright and support the weight of the head and upper body. However, too much curvature may cause spinal imbalance, causing spinal conditions that may result in pain or loss of mobility.

Normal adult spines are positioned over the pelvis, so upright posture doesn't strain muscles. However, changes of spinal position can stress muscles and cause spinal deformity. If the spine is injured and unable to function properly, it can be very painful or even disabling.

Parts of the Spine

The spine is made of many parts that protect the spinal cord, facilitate movement and support the body.

1 Spinal Cord

The spinal cord has nerve pathways that carry signals, such as pain, from the arms, legs, and the body to the brain.

2 Nerve roots

Nerve roots are used to transmit information between the spinal cord and the other parts of the body, such as arms, legs and organs.

3 Vertebral Body

The cylinder-shaped vertebral body is the weight-bearing structure of the vertebrae.

4 Lamina

The flat plates of the lamina create the outer wall of the vertebral canal and help protect the spinal cord.

5 Vertebral Canal

The spinal cord sits in this channel formed by the lamina and the vertebral body.

6 Pedicles

Pedicles connect the lamina to the vertebral body.

7 Discs

Discs separate the vertebrae. They are made of tough, elastic material that allows the spine to bend and twist naturally.

8 Articular Facet

The articular facets are where two neighboring vertebrae attach.

9 Spinous Process

The spinous process protrudes from the back of each vertebra. Muscles and ligaments that move and stabilize the vertebrae attach to the spinous processes.

10 Transverse Process

Two transverse processes stick out of the sides of each vertebra. Muscles and ligaments that move and stabilize the vertebrae attach to the transverse processes.

Nervous System

All of the above elements of the spinal column and vertebrae protect the spinal cord, which provides communication to the brain.  The spinal cord also transmits sensation and mobility in the body through interaction of ligaments, bones and muscle structures of the back and its surrounding nerves.

The spinal cord ends at the L1 level, where it divides into many different nerve roots that travel to the lower body and legs. This bunch of nerve roots is called the cauda equina, which means "horse's tail."