Questions and Answers
What role do the processes emerging from the pia matter play in relation to the spinal cord?
Where does the arachnoid matter terminate?
What is contained within the sub-dural space?
What is the safe site for a lumbar puncture?
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Which factor is NOT involved in fixing the spinal cord?
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What is the average length of the spinal cord in adults?
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At what level does the spinal cord end in adults?
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Which of the following correctly describes the cervical enlargement?
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What structure forms the lower end of the pia mater?
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How many segments does the spinal cord have?
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Which layer of the meninges is the outermost?
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What is the function of the denticulate ligament?
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What occurs to the position of the spinal cord at three months of fetal life?
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Study Notes
Gross Features of the Spinal Cord
- Spinal cord located in the upper two-thirds of the vertebral canal.
- Average length is 45 cm, while the vertebral canal measures 60 cm.
- Begins at the lower border of the foramen magnum, continuing with the medulla oblongata.
- Ends at the lower border of L1, continuing as the filum terminale.
- Lower end expands into the conus medullaris.
- Cylindrical structure with two enlargements:
- Cervical enlargement at C4 to T1 segments (brachial plexus origin).
- Lumbar enlargement at L1 to S3 segments (lumbar and sacral plexuses).
Relations to the Vertebral Column
- Fills entire vertebral canal length at three months of fetal life.
- Extends to L3 level at birth.
- In adults, ends at L1 level.
Segments of the Spinal Cord
- Composed of 31 segments: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal.
- Each segment gives rise to a pair of spinal nerves.
Meninges of the Spinal Cord
- Spinal cord surrounded by three meninges, continuous with those of the brain: pia mater, arachnoid mater, and dura mater.
Pia Mater
- Inner vascular layer following spinal cord contours and fissures.
- Ends with the spinal cord at L1 level, forms the filum terminale.
- Dentate ligaments emerge from its borders for cord fixation.
- Has 21 pointed processes that attach to the dura mater.
Arachnoid Mater
- Thin, transparent, and impermeable middle layer.
- Ends at S2 level.
Dura Mater
- Tough, dense outer layer.
- Also ends at S2 level, continuous with the arachnoid mater.
Spaces Between the Meninges
- Sub-arachnoid Space: Between arachnoid and pia mater; contains cerebrospinal fluid (CSF).
- Sub-dural Space: Between dura and arachnoid; contains serous fluid for lubrication.
- Extra-dural Space: Between dura mater and vertebral canal wall; contains internal vertebral venous plexus.
Lumbar Puncture
- Conducted in the sub-arachnoid space from L2 to S2, known as the lumbar cistern.
- Contains filum terminale and roots of lower spinal nerves.
- Safe needle insertion at L3-L4 or L4-L5 intervertebral discs.
- Purposes include:
- Spinal anesthesia via anesthetics in sub-arachnoid space.
- Obtaining CSF samples for meningitis diagnosis.
- Injection of radio-opaque dye for myelography.
Factors Fixing the Spinal Cord
- Filum terminale attachment to the coccyx.
- Dentate ligaments fastening to dura mater.
- Dura mater connection to foramen magnum.
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Description
This quiz focuses on the gross features of the spinal cord, including its location within the vertebral canal and its structural connections. Understand the anatomy and length of the spinal cord as well as its relationship with the medulla oblongata and the filum terminale.
