Vertebrae

The spinal column is made up of 33 separate bones that interlock to form the vertebrae. The average human is born with 33 separate bones (vertebrae) that interact and attach via facets, which are flexible joints. Each vertebra is a unique bone with a complex structure made up of bone and hyaline cartilage. The proportions of which vary depending on the backbone segment and vertebrate species. A vertebra's basic configuration varies; the biggest part is the body, and the centrum is the middle part. The intervertebral discs are attached to the upper and lower surfaces of the vertebral body. A vertebral arch is made up of eleven parts: two pedicles, two laminae, and seven processes that make up the posterior part of the vertebra. The back and front portions of the vertebrae articulate with each other to provide the spinal column strength and flexibility, and the shape at their back and front aspects define the range of motion. the vertebral body, which bears weight, and the vertebral arch, which protects the spinal cord. The spinal column is made up of seven cervical, twelve thoracics, and five lumbar vertebrae, as well as five fused sacral vertebrae and four fused coccyx vertebrae.

Types of Vertebrae

There are Three groups of vertebrae that make the spine. The cervical, thoracic, and lumbar spines are commonly divided into three primary regions to describe the normal structure of the spine. Seven cervical vertebrae (called C1 through C7), twelve thoracic vertebrae (designated T1 through T12), and five lumbar vertebrae (named L1 through L5) make up the spine. The size of vertebrae varies, with cervical vertebrae being the smallest and lumbar vertebrae being the largest. Vertebral bodies are the weight-bearing structure of the spinal column. The spine distributes the upper body's weight to the sacrum and pelvic. The kyphotic and lordotic curves in the spine provide resistance and elasticity in dispersing body weight and axial loads during movement.

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Functions of the Vertebral

• The spinal cord is protected and supported by the vertebrae.

• The vertebrae are the base for attachment ligaments, tendons, and muscles.

• Vertebrae provide structural support for the head, shoulder, chest, connecting upper and lower body, balance, and weight distribution. 

• Vertebrae provide flexibility and mobility like flexion(forward bending), extension(backward bending), side bending(left and right), rotation combination of above. 

Cervical Vertebrae: 

The cervical spine is a complicated structure that runs from just below the skull to the first thoracic vertebra, making up the initial portion of the spinal column. The cervical spine is divided into two segments that are structurally and functionally distinct. These segments work together to allow the head and neck to rotate, lateral flexion, flexion, and extension. It consists of seven vertebrae.

The first two, C1 and C2, are very specific and have their names: atlas and axis. The atlas vertebrae(C1) and axis vertebrae(C2) are two bones that make up the craniovertebral junction (CVJ) of the spine. The atlas and axis are responsible for spinal rotation, flexion (bending forward), and extension (bending backward). This is the part of the spine that moves the most. Between the occiput and C1, around half (50%)of the neck's flexion and extension occurs, and between C1 and C2, about half (50%)of the neck's rotation occurs. The movement is supported by a small amount of rotation of the spinal column.

The C3-C7 vertebrae have a body, pedicles, laminae, spinous processes, and facet joints, and are more traditional vertebrae. C3 provides motor function as well as sensation from the top of your scalp to the sides of the face to the head and neck. When we breathe, C4 allows us to shrug the shoulders and causes the diaphragm to contract automatically. The neck, shoulders, and upper arms all receive sensation through the 4th cervical spinal nerve. C5 allows you to lift the shoulders and flex the biceps, as well as feel near the tip of the shoulder. 

C6 controls wrist movement and biceps flexion, as well as providing sensation to the inner (thumb) side of the forearms and hand. The triceps muscle on the back of the upper arms is controlled by C7, which also transmits sensation down the back of the arms and to the middle finger. C8 gives the ability to open and close the hands (handgrip) and also feel the outside (pinky) side of the hands and forearms.

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Thoracic Vertebrae: 

Between the cervical and lumbar vertebrae, thoracic vertebrae are located. In humans, there are 12 thoracic vertebrae, which grow in size as you move down the body. They are larger and thicker than cervical vertebrae, but smaller than lumbar vertebral bones. The increase in size ensures that they can support the body's weight. The thoracic spine is made up of twelve vertebrae, numbered T1 through T12 from top to bottom. When viewed from the side, kyphosis is a typical forward curvature. The purpose of the thoracic vertebrae is to support the back. They create a protective cage around the sensitive organs of the thorax, such as the heart and lungs, thanks to their articulations with the ribs. Because of the design of these joint articulations, this region of the spine has restricted mobility. The back of each vertebra has a pair of thoracic facet joints that allow for limited spinal movement.

The top two thoracic nerves, T1 and T2, supply nerves to the top of the chest, as well as the arm and hand. T3, T4, and T5 are the ones that are fed into the chest wall to support breathing. T6, T7, and T8 can feed into the chest and/or the abdomen. T9, T10, T11, and T12 can feed into the abdomen and/or lower back.

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Lumbar Vertebrae:

The lumbar spine starts below the last thoracic vertebra (T12) and ends at the top of the sacral spine, also known as the sacrum (S1). Most people have five lumbar levels (L1-L5), although having six is not unusual. From top to bottom, the lumbar spinal levels are numbered L1 through L5, or L6. When viewed superiorly, the lumbar vertebral body is kidney-shaped, meaning it is broader from side to side than front to back, and slightly thicker in front than the backside. The lumbar spine is designed to be extremely strong to protect the spinal cord and spinal nerve roots, which are extremely sensitive. In adulthood, the spinal cord forms the conus medullaris around the L1 or L2 vertebrae. The topmost portion of the lumbar spinal column is the L1 vertebra. A segment of the spinal cord is located in this area of the spine. The end of the spinal cord proper is found in the L2 vertebra; all remaining spinal vertebrae below this point just have spinal nerves, not the spinal cord. The L3 is the lumbar spine's middle vertebra and the first to be empty of a segment of the spinal cord. The L4 is the lumbar spinal column's second-to-last segment. The L5 vertebra is the lumbar spine's last segment (at least, it is for most people).

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Sacral Vertebrae:

The sacral vertebrae, commonly known as the sacral spine, are made up of five bones. The sacrum, a shield-shaped bony structure located at the base of the lumbar vertebrae and attached to the pelvis, is formed when these bones fuse together. Segments S1 through S5 make up the sacral vertebrae, which are placed between the lumbar vertebrae and the coccyx (tailbone), the lowest section of the vertebral column. During the first and second months of embryonic development, sacral vertebrae form. The alae are the wide lateral wings formed by the first three vertebrae of the sacral area. The sacrum also supports the rear wall of the pelvis and the sacroiliac joints, which connect the hip bones. The first sacral bone is referred to as S1, the second sacral bone is referred to as S2, and so on. S1 is at the top of the list, while S5 is at the bottom. Each number relates to a certain section of the spinal cord's nerves.

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Coccyx Vertebrae:

The coccyx is the last vertebral column bone that protects the spinal cord. The coccyx, often known as the tailbone, is the last section of the spinal column in all apes, with similar structures in other mammals such as horses. Three, four (most usually), or five fused, rudimentary vertebrae make up the coccyx. The coccyx has a concave curvature that angles anteriorly toward the pelvis. The anterior and posterior transverse grooves of the coccyx are formed by the fusion of the transverse processes of each coccygeal vertebrae, which are not easily apparent.

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