Spina Bifida Argumentative Essay
Spina bifida is an inborn abnormality involving the spine and brain. This part of the body begins to develop in the fetus during the first month of pregnancy from a structure called the neural tube (Kaplan, Spivak and Bendo, 2005).
Cells from the neural tube differentiate to form nervous and bone tissues which make up the spine or vertebral column, the spinal cord and also the brain. The normal neural tube is a closed structure and failure to close results in defects. There are anatomical differences between the vertebral column and spinal cord of a normal person and one suffering from spina bifida.A typical vertebra is composed of a body and a vertebral arch (Tortora and Derrickson, 2005, p. 214). The body of the vertebra is disc-shaped and located anteriorly.
Behind the body are two projections called pedicles. Each pedicle unites with the lamina, a flatter structure which ends in the spinous process located posteriorly. The vertebrae, when stacked on top of each other, becomes the vertebral column. It is divided into the cervical (neck), thoracic (chest), lumbar (lower back) and sacral (into the pelvic cavity) regions (Tortora and Derrickson, 2005, p. 16).
The first cervical vertebra connects to the foramen magnum, the opening at the floor of the cranium or skull. The sacrum connects to the posterior portion of the pelvis. In the middle of the vertebra is an opening called the vertebral foramen. The vertebral foramina of all the vertebrae when they are stacked together form the spinal cavity. This completely encloses and protects the spinal cord and its associated fatty tissues, cerebrospinal fluid circulating from the brain, nerve roots and blood vessels (Kaplan, Spivak and Bendo, 2005).
Spaces between the pedicles also allow individual nerves to branch out from their roots in the spinal cord and provide motor function to the muscles. The spinal cord connects to the brain through the medulla oblongata of the brain stem and ends as the conus medullaris at the lumbar region. From this cone-like structure descends the filum terminale, a connective tissue that serves to secure the spinal cord to the coccyx or the lower end of the vertebral column (Tortora and Derrickson, 2005, p. 214).Arising from the spinal cord are the cervical and lumbar enlargements – bundles of nerves that provide innervation to and from the superior and inferior limbs of the body respectively. In persons suffering from spina bifida, which literally means “split spine”, vertebrae and spinal cord are present.
However, there is an opening in the lamina of the vertebrae, most often in the fifth lumbar spine and the first sacrum, which exposes a portion of the spinal cord (Au, et. al, 2008, p. 692). In some cases, this does not present any health deficiency as the spinal cord and nerves are unaffected.
In this form of spina bifida, there may be a dimpling of the skin in the area of the open vertebral cavity. The non-closure of vertebral laminae permits the meninges of the spinal cord or the spinal cord itself to protrude through the opening rather than following the length of the spinal cavity. These manifest either as a cyst-like sac at the lower back of the baby or as an open lesion exposing the vertebral cord and nerves (Nanigian, Nguyen, Tanaka, Cambio, DiGrande and Kurzrock, 2008, p. 1771).
The severity of nerve damage depends on the number of nerves affected.Partial paralysis of the lower limbs and loss of bladder and bowel control are common consequences (Brislin, 2008, p. 34). Hydrocephalus also occurs in spina bifida because the cerebellum deviates from its position causing the brain stem to ram into the spinal cord (Williams, 2008). This is known as the Arnold Chiari II malformation. The cerebrospinal fluid in the brain circulates along the ventricles then drains into the spinal cord through the brain stem.
When ramming occurs, drainage is blocked and the cerebrospinal fluid accumulates in the brain. The extreme pressure from fluid build-up causes the skull to enlarge.