Spinal Cord – Class 11 | Chapter – 21 | Biology Short Notes Series PDF

Spinal Cord: It is a long, tube-like tissue band. It is the link between your brain and your lower back. The spinal cord transmits nerve signals from the brain to the body and vice versa. These nerve signals assist you in feeling sensations and moving your body. Any damage to your spinal cord can impair your ability to move or function.


Anatomy of Spinal Cord

In adults it is usually 40cm long and 2cm wide and forms an important connection between the brain and the body.

It is divided into five different parts.

  • Sacral cord
  • Lumbar cord
  • Thoracic cord
  • Cervical cord
  • Coccygeal

There exist many spinal nerves that emerge out of each segment of the spinal cord. There are 8 pairs of cervical, 5 lumbar, 12 thoracics, 5 sacral and 1 coccygeal pair of spinal nerves. It helps in the primary processing of information as it carries sensory signals from all parts of the body to the Central Nervous System through afferent fibres. Additionally, nerve tissue comprises the grey and white matter spread across uniformly. The smooth muscles as well as the skeletal system carrying nerve fibres liaise different reflexes when ventral horn projects axons which carry motor neurons. It also helps arbitrate autonomic control for visceral functions which consist of neurons with descending axons. It is a sensitive site, which is severely affected in case of a traumatic injury.

Functions of Spinal Cord

The primary function is to transport nerve signals throughout your body. These nerve messages serve three important purposes. They are:

  • Control the movements and functions of the body: Your movements are controlled by signals sent from your brain to other parts of your body. They also control autonomic (involuntary) functions such as breathing rate, heart rate, and bowel and bladder function.
  • Senses should be reported to your brain: Other parts of your body send signals to your brain, which helps it record and process sensations like pressure or pain.
  • Control your reflexes: Some reflexes (involuntary movements) are controlled by your spinal cord without the involvement of your brain. Your spinal cord, for example, controls your patellar reflex (involuntarily moving your leg when someone taps your shin in a certain spot).

Structure of Spinal Cord

The length of the spinal cord varies between individuals. Females, according to some estimates, have a spinal cord length of about 43 centimetres (cm), while males have a spinal cord length of about 45 cm. It is divided into three sections: the cervical (neck), thoracic (chest), and lumbar (lower back).

Structure of Spinal Cord
  • The dura mater, arachnoid mater, and pia mater are three layers of tissue that protect the spinal cord. These layers are referred to as “meninges” by doctors. These are the layers:
  • Dura mater: The outermost layer of the meninges of the spinal cord. It’s a tough, protective layer.
  • The epidural space is located between the dura and the arachnoid space. This is where doctors may inject local anaesthetic to alleviate pain during childbirth and some surgical procedures, such as those to repair a lung or abdominal aneurysm.
  • Mater arachnoidum: The arachnoid mater is the spinal cord’s middle layer of protection.
  • Subarachnoid space (SAS): This is found between the arachnoid and pia maters. This space contains cerebrospinal fluid (CSF). A doctor may need to take a CSF sample to test for the presence of an infection, such as meningitis. For some surgical procedures, such as a caesarean section, they can also inject local anaesthetic into this space.
  • The vertebral column, or spinal bones, protects the spinal cord and its protective layers. These bones extend from the base of the skull to the sacrum, a bone that fits into the pelvis.
  • The number of bones in the cervical, thoracic, and lumbar regions varies. Most people have seven cervical vertebrae, twelve thoracic vertebrae, and five lumbar vertebrae.

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By Team Learning Mantras