Describe the length and location of the adult spinal cord. Why is a lumbar puncture performed between L3 and L4?
Understand the Problem
The image presents objectives and review questions related to the spinal cord and peripheral nerves from a textbook or study guide. Specifically, it asks to "Describe the length and location of the adult spinal cord" and "Why is a lumbar puncture performed between L3 and L4?"
Answer
The adult spinal cord is 17 inches long, extending from the foramen magnum to L1. Lumbar punctures are performed between L3 and L4 to avoid spinal cord injury.
The adult spinal cord is approximately 17 inches (43 cm) long, extending from the foramen magnum of the occipital bone to the first lumbar vertebra (L1). A lumbar puncture is performed between L3 and L4 because the spinal cord ends at L1, thus avoiding injury to the cord.
Answer for screen readers
The adult spinal cord is approximately 17 inches (43 cm) long, extending from the foramen magnum of the occipital bone to the first lumbar vertebra (L1). A lumbar puncture is performed between L3 and L4 because the spinal cord ends at L1, thus avoiding injury to the cord.
More Information
The spinal cord serves as a sensory pathway, motor pathway, and reflex center.
Tips
A common mistake is confusing the length of the spinal cord in infants versus adults. In infants, it extends the full length of the spinal cavity, while in adults, it extends only to L1.
Sources
- Nervous System: Spinal Cord and Peripheral Nerves - evolve.elsevier.com
- Lumbar Puncture - StatPearls - NCBI Bookshelf - ncbi.nlm.nih.gov
- Lumbar puncture (spinal tap) - Mayo Clinic - mayoclinic.org
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