ventricle in the pons and medulla. The fourth
ventricle continues with the central canal of
the spinal cord. Three openings in the roof of
the fourth ventricle, a pair continues with the
central canal of the spinal cord. Three
openings in the roof of the fourth ventricle, a
pair of lateral apertures (foramina of luschka)
and a median aperture (foramen of Magendie)
allow cerebrospinal fluid to move upward to
the subarachnoid space that surrounds the
brian and spinal cord.
The cerebrospinal fluid is secreted by
anterior choroid plexus and posterior
choroid plexus and is found inside the
ventricles of the brain, the central canal of the
spinal cord. The cerebrospinal fluid acts as a
shock absorber for the brain and spinal cord
and may also nourish brian tissue. It contains
protein, glucose, chloride and water.
The spinal cord
- It is a posterior part of CNS which runs mid
dorsally within the vertebral column. It is
elongated, almost cylindrical part. It extends
from the medulla oblongata within vertebral
column to the level of second lumber vertebra. - 42-45 cm long and 2 cm thick (in mid thoracic
region) and longer in lower cervical and
lumbar regions. It grows till 4-5 yrs. It acts
like a link between brain and various parts of
the body. - Internally, spinal cord is divided into left and
right symmetrical halves. Posterior is median
sulcus and anterior is median fissure. There
is a central canal surrounded by a butterfly
shaped area of grey matter. Around the grey
matter there is white matter.- Grey matter is H-shaped with two dorsal
and ventral horns. Roots of spinal nerve are
originated from the horns. - There are 31 pairs of spinal nerves that arise
from different segments of spinal cords. Each
spinal nerve carries both sensory and motor
impulses. Each spinal nerve connects with
nerve roots.
Dorsal nerve root: It originates from the dorsal
horn of grey matter. It consists of only sensory
fibres. It bears the dorsal root ganglion
containing only sensory cells.
Ventral nerve root: It originates from the ventral
horn of grey matter. It is made up of only
motor fibres. It does not bear ganglion.