Enabling Objectives
  1. Describe the anatomy of a typical vertebra and draw a line diagram to show the parts.
  2. Recognise the variations in thoracic, lumbar, sacral and especially the cervical region of the vertebral column.
  3. Outline the joints and ligaments between adjacent vertebrae.
  4. Name the curvatures of the vertebral column and define the normal movements of the spine.
  5. Summarise the normal anatomy and function of the spinal cord and nerves and the effect of injury.

1. Draw and Label the anatomy of a generic vertebrae.

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What are the different types of vertebrae and what are their differences?

The spine consists of the following types of vertebrae: cervical, thoracic, lumbar, sacral and the coccyx.

Cervical: Seven of these vertebrae (C1-C7). Their vertebral body is relatively small in comparison to the other vertebrae, the name of the first cervical is atlas and the second vertebrae’s name is axis, in addition C1 has not spinous process, however the other spinous processes are notched and also known as bifid. The first two vertebrae are seriously different than the c3-c6, however C7 is different again to fit with the thoracic vertebrae. The surface in a cervical vertebra is typically concave from side to side. The transverse processes are fused to the costal processes, these two components encircle the transverse foramina. The foramen protect nerves, veins and arteries, which service the brain, because of these two features cervical vertebrae can be distinguished from the other ones. Cervical vertebrae are more flexible than the other ones and hence give the head a greater mobility than the other vertebrae. The head movement can be very significantly altered through sudden acceleration or decelerations, as the muscles are not ready for the moving of the head. In addition the atlas is not as big in comparison for holding the head, hence the muscles supporting very important for the movement of the head.
C1 or the Atlas hold the head up it can easily be distinguished from the other vertebrae as it is lacking spinous process and the typical body, and the presence of the anterior and posterior arches. The atlas articulates with the second cervical vertebra called the axis, which allows the sidewise head movement.
The axis is very important as the atlas is supported by it, in addition it has the muscles for the movement of the head, the development of the dense causes fusion between the body of atlas and the body of axis, which allows a better control of the head.

The vertebrae Prominens
A vertebrae resembles their following one or previous one, hence the C7 has long slender spinous process, this vertebra is the interface between the cervical and thoracic curve, additional muscles are attached to the transverse process as it is longer than the normal cervical vertebrae. The ligament called ligamentum nuchae, begins at the ligament vertebra prominens and extends to the skull along the occipital crest. It is attached to the other spinous process of the cervical vertebrae, and keeps the head in a upright position.

The thoracic vertebrae

There are in total 12 thoracic vertebrae and their function is to hold the weight of the ribcage and the ribs themselves, a thoracic vertebra is heart shaped and is bigger in size than that of the cervical vertebrae. However the vertebral foramen is smaller in comparison to the cervical, but the spinous process are long and slender, but the last three thoracic vertebrae start to resemble the lumbar vertebrae. Each of the these vertebrae are enclosed by ribs, and The costal facet can articulate with the heads of the ribs and the location and structure can vary from vertebra to vertebra. T1-T8 have two ribs on them, whereas T9-T11 have only one location for the ribs, in addition the T1-T10 have transverse processes and are relatively thick, and they contain transverse costal facets, thus allowing rib 1 to 10 to contact the vertebrae at two points, a costal facet and a transverse costal facet.

Lumbar Vertebrae
There are in total 5 lumbar vertebrae, and their vertebral body is the largest and thickest as they have to hold all the weight of the body, and the surfaces are rather oval shaped, than heart shaped. In addition lumbar vertebrae do not have any costal facets, the slender transverse processes project dorsolaterally, the vertebral foramen is triangular, the stumpy spinous processes project dorsally; the superior articular process face medially (up and in), and the inferior articular processes face laterally (down and out).
As the lumbar vertebrae have to carry the most weight, their spinous process have accordingly the biggest surface area, so the muscles can attach themselves and reinforce and adjust the lumbar curve.

The Sacrum

The sacrum is a fusion of five sacral vertebrae, the fusing starts shortly after puberty and is complete around 25-30, the sacrum has the function of protection of the reproductive, digestive and urinary organs. Because the surface area of the sacrum is that extensive it provides the maximum area for the muscles to hold themselves onto it. The sacral is the entrance for the nerves which come from the vertebral canal of the spinal cord, its between the articular procces and extends of the length of the sacrum. The medial sacral crest is a ridge which is formed due to the fusion of the sacral vertebrae, the sacral cornua is formed as the fifth vertebra fails to the contact of the lamia. The sacral hiatus is a opening at the inferior end of the sacrum and is the other end of the sacral canal, it is covered by connective tissue.
The sacral foramina are four on each sides and the intervertebral foramina of the fused sacral vertebrae open into these passageways.
The lateral crest are ridges on the sides and represent the fusion of the transverse processes of the sacral vertebrae, these crests provide surface area for muscles.
The sacrum is curved, the degree of curvature is greater in males rather than females. The auricular surface is thickened and flattened. The sacral tuberosity is a roughened area between the lateral sacral crest and the auricular surface. The sacral tuberosity is a roughened area between the lateral crest and the auricular surface. It marks the attachment site of the ligaments that stabilize the sacroiliac joint.
The subdivisions of the sacrum are most clearly seen in the anterior view. The narrow inferior portion is the sacral apex, whereas the broad superior surface forms the base.

The coccyx
The coccyx is made of fusion between three to five however most of the time four coccygeal vertebrae, it starts usually fusing at the age of 26, these are important for the muscles that constrict the anal opening the first coccygeal vertebrae is known as the coccygeal cornua, this laminae is curve and meets the scral cornua. It does not fuse totally until the late adult hood.

Outline the Joints/Ligaments between the vertebrae.

The spine has two types of joints, one is a pivot joint which allows the circular movement between axis and atlas thus allowing the head to move sidewise. In addition the joints on the spine are on intervertebral disks, which allows the sidewise or forward bending of the body. The spine itself consists of many muscles, such as the liagmentum flavum, that goes from the intervertebral foramen of one vertebra to another. Inside the intervertebral foramen the spinal cord runs through. There is a ligament that goes from spine to spine and one side is called interspinous and the other side is called supraspinous ligament. The posterior longitudinal ligament comes from the top of the vertebrae and goes till the sides of the disc below the vertebra. The anterior longitudinal ligament runs on the front side of the vertebral body. The joints are gliding joints.

There are the following muscles the intertransversarii, rotators and interspinales muscles. Which carry the functions of the muscles in the vertebral column.

Why is the spine curved and what sort of movement does it carry out?

The spine has four total curves: Cervical, Thoracic, Lumbar and Sacral.

The initial two curves are the thoracic and the sacral and in infants this makes a c shape of the spine, however after a couple of months the other curves develop as well and this is called the compensation or secondary curve. The shape of the spine becomes like a double-S. The spine is fully developed in its shape when the infant becomes of 10 years of age. The body’s weight needs to be carried on the spine hence the shape of the spine is reason for this. The various curves align the weight along the axis and heavy weigth can be carried if the spine stays in its axis. The reason why woman develop pain during pregnancies is due to the back pain from changes in the lumbar curvature. It allows balance and carrying weights.

What is the normal anatomy and function of the spinal cord and the effects of its damage?

The adult spinal cord is about 45 cm long.
Posteriors median sulcus is is a shallow longitudinal groove, whereas the anterior median fissure is a deeper groove on the other side of the surface on the spinal cord. The central nervous system (CNS) consists of the brain and spinal cord. The peripheral nervous system (PNS) consists of all nervous tissue outside the CNS.

Structures that make up the nervous system include the brain, 12 pairs of cranial nerves and their branches, the spinal cord, 31 pairs of spinal nerves and their branches, ganglia, enteric plexuses and sensory receptors.

The nervous system helps maintain homeostasis and integrates all body activities by sensing changes (sensory function), interpreting them (integrative function) and reacting to them (motor function).

Sensory (afferent) neurons carry sensory information from cranial and spinal nerves into the brain and spinal cord or from a lower to a higher level in the spinal cord and brain. Interneurons have short axons that contract nearby neurons in the brain or spinal cord. Motor (efferent) neurons carry information from the brain toward the spinal cord or out of the brain and spinal cord into cranial or spinal nerves.

Components of the PNS include the somatic nervous system (SNS), autonomic nervous system (ANS), and enteric nervous system (ENS).

The SNS consists of neurons that conduct impulses from somatic and special sense receptors to the CNS and motor neurons form the CNS to skeletal muscles.

The ANS contains sensory neurons from visceral organs and motor neurons that convey impulses from the CNS to smooth muscle tissue, cardiac muscle tissue, and glands.

The ENS consists of neurons in enteric plexuses in the gastronintestinal (GI) tract that function somewhat independently of the ANS and CNS. The ENS monitors sensory changes in and controls operation of the GI tract.