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Renin Angiotensin Mechanism.

Human Brain: Spinal Cord.

 

Spinal Cord.

  • The spinal cord is roughly cylindrical in shape, 

  • Present in the vertebral cavity of the vertebral column. 

  • In adults it extends from the medulla oblongata to the superior border of the second lumbar vertebra. 

  • Its length ranges from 42-45 cm with a diameter of about 2 cm in the thoracic region.

  • The spinal cord is also surrounded by three spinal meninges namely.

    • Dura matter- Superficial layer

    • Arachnoid mater- Middle layer

    • Pia mater- Inner layer.

  • Spinal cord consists of 31 pairs of spinal nerves. 

Cervical Nerves

8 Pairs

Thoracic Nerves

12 Pairs

Lumbar Nerves

5 Pairs

Sacral Nerves

5 Pairs

Coccygeal Nerves

1 Pair

  • At the terminal end of the spinal cord the roots of the spinal nerves go inferiorly in the vertebral cavity which is collectively called as cauda equina (Horse’s tail).

  • The nerve which extends inferiorly up to the coccyx is called a filum terminale.

Internal Anatomy:

  • The cross section of the spinal cord shows H-shaped gray matter present at the centre surrounded by white matter. 

  • A small space present in the centre of the gray matter is called the central canal which consists of CSF. 

  • The gray matter on each side of the spinal cord is subdivided into anterior gray horns and posterior gray horns. 

  • These gray horns divide the white matter into three areas.

    • Anterior white column

    • Posterior white column

    • Lateral white column

  • Anterior part deals with “Somatic” work.

  • Posterior part deals with “Autonomic” work.

  • Posterior horn contains a v- shaped area called “Substantia gelatinosa”.

  • Sensory nerves of the spinal cord consist of axons that conduct impulses towards the brain.

  • Motor nerves consist of axons that carry impulses from the brain to the skeletal muscles.

  • Spinal cord connects the brain to the sensory receptors, muscles and glands present in all parts of the body.

Commonly Asked Questions.

  1. Write a short note on “Spinal Cord”.

  2. Draw a well labelled diagram of T.S. of Spinal Cord.

  3. Explain the internal anatomy of the spinal cord.
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