Question

Size of cord segments:

1. The more superior, the more white matter. why is this?

2. grey matter is larger in cervical and lumbar regions. why is this?

Answer 1

1. White matter consists of myelinated nerve fibers or axons and no dendrites surrounded by myelin which is a white fatty material composed of lipoproteins. This acts as an insulator and increases the speed of transmission of all nerve signals. Grey Matter consists of neuronal cell bodies, neuropil (dendrites and unmyelinated axons), glial cells (astroglia and oligodendrocytes), and capillaries.

Grey matter is associated with processing and cognition, white matter regulates the distribution of action potentials.

2. The Spinal cord is composed of nervous tissue (white matter and grey matter). The spinal cord is divided into four regions 1) Cervical 2) Thoracic 3) Lumbar 4) Sacral.

Out of these four regions, there are two enlargements present in the spinal cord. 1) Cervical enlargement extends from C3 to T1 2) Lumbar enlargement extends from L1 to S2.

The cervical and lumbar enlargements are due to the enlargement of grey matter which contains cell bodies (neurons, dendrites, unmyelinated axons). This function of grey matter is necessary to operate the limbs. Cervical enlargement along with grey matter enlargement corresponds to large nerves to operate upper limbs. Lumbar enlargement along with grey matter enlargement corresponds to large nerves to operate lower limbs.