Question

How many laminae are present in the grey matter of the spinal cord?
(a) Four
(b) Six
(c) Eight
(d) Ten

Answer 1

Hint: Spinal cord constitutes a number of the spinal nerves, these spinal nerves present on the second lumbar vertebra of the vertebral column. All these nerve fibres control different functions of the body. The grey matter of the spinal cord also contains a number of the lamina which mainly function for reflex action of the body.

Complete answer:
Spinal cord present at the posterior portion of the Central nervous system within the vertebral column. From the fourth cervical to first thoracic vertebrae, the spinal cord is flattened.
In cross-section, the spinal cord has a butterfly shaped grey matter which consists of nerve cell bodies, dendrites, and synapses. Grey matter is divided into a horn on each side of the spinal cord and these horns are of four types- dorsal horn, intermediate column, lateral horn, and ventral horn. Dorsal horn receives somatosensory information from the body, ventral contain motor neuron, and intermediate and lateral horn regulate visceral and pelvic organs.
In 1950, Bror Rexed identified lamina in the spinal cord which is also called Rexed lamina, this lamina is arranged on the basis of its function. There are a total of 10 laminae are present in the grey matter of the spinal cord and each lamina perform a different function as follow-
Lamina I- Respond to thermal stimuli.
Lamina II-Regulate sensory input.
Lamina III-Respond to the sensation of light.
Lamina IV-Relay sensory information.
Lamina V-Relay sensory information is mainly painful.
Lamina VI- Receive sensory information from muscles.
Lamina VII-Relay motor information to viscera.
Lamina VIII- Involved in the cervical and lumbar enlargement.
Lamina IX- Motor neuron regulating skeletal muscle.
Lamina X- Axon cross over takes place.

Additional Information: The grey matter of the spinal cord is covered with the white matter which contains bundles of the myelinated nerve fibre. Due to the presence of fatty myelinated sheath white colour form. It lies in the deep surface of the brain and produces impulse for different sensations and body activity.

So the correct answer is Ten.

Note: Spinal cord acts as the centre of reflex action due to which the work of the brain reduces. The spinal nerve from the spinal cord arranged in the vertebral is named on the basis of the name of vertebrae like cervical, thoracic, lumbar, sacral, and coccygeal. A total of 31 pairs of spinal nerves are present in the vertebral column.