Anatomi Sistem Saraf-Medulla Spinalis (Sumsum tulang belakang)

Summary

This lecture provides an in-depth exploration of the spinal cord (medulla spinalis) for anatomy students. It covers the structure, development, and protective layers of the spinal cord, including the conus medullaris, filum terminale, and meninges (dura mater, arachnoid, and pia mater). The video highlights the two enlargements (cervical and lumbar) and the internal organization of gray and white matter, including columns and tracts. Ascending sensory pathways and descending motor pathways are explained, along with their functions. Finally, the lecture addresses the vascularization of the spinal cord through anterior and posterior spinal arteries, providing a comprehensive overview essential for understanding spinal anatomy and neurophysiology.

Takeaways

• 🧠 The spinal cord (medulla spinalis) occupies only about two-thirds of the vertebral canal and extends from the first cervical vertebra to the level of the first or second lumbar vertebra.
• 📍 The inferior end of the spinal cord forms the conus medullaris, which continues as the filum terminale that attaches to the coccyx.
• 🐴 The bundle of spinal nerve roots below the conus medullaris is called the cauda equina because it resembles a horse’s tail.
• 👶 During embryonic development, the spinal cord initially fills the vertebral canal, but differential growth causes the spinal cord to end at a higher vertebral level in adults.
• 🔍 The spinal cord has two enlargements called intumescentiae: the cervical enlargement and the lumbosacral enlargement.
• 💪 The cervical enlargement gives rise to the brachial plexus, which innervates the upper limbs.
• 🦵 The lumbosacral enlargement gives rise to the lumbosacral plexus, responsible for innervating the lower limbs.
• 🛡️ The spinal cord is protected by three meninges: dura mater, arachnoid mater, and pia mater, along with cerebrospinal fluid (CSF).
• 💧 The subarachnoid space contains cerebrospinal fluid and is an important site for lumbar puncture procedures.
• 🧵 The pia mater closely adheres to the spinal cord and contributes to the formation of the filum terminale internum.
• 📚 External landmarks of the spinal cord include the anterior median fissure, posterior median sulcus, and various lateral sulci that divide the white matter regions.
• ⚪ White matter (substantia alba) contains ascending and descending nerve tracts, while gray matter (substantia grisea) contains neuron cell bodies and resembles a butterfly shape.
• 📈 The cervical spinal cord contains more white matter because many ascending and descending tracts pass through this region.
• 🚦 Ascending sensory tracts include the fasciculus gracilis and cuneatus, which carry fine touch, vibration, and proprioception information.
• 🔥 The spinothalamic tracts transmit sensory information such as pain, temperature, crude touch, and pressure.
• 🏃 Descending motor tracts include the corticospinal tracts, which control voluntary muscle movement.
• ⚙️ Extrapyramidal tracts such as tectospinal, vestibulospinal, reticulospinal, and rubrospinal tracts coordinate posture, balance, reflexes, and muscle tone.
• 🩸 The spinal cord receives blood supply mainly from the anterior spinal artery and the posterior spinal arteries, which originate from branches of the vertebral arteries.

Q & A

What is the extent of the spinal cord in the vertebral column?

The spinal cord occupies approximately two-thirds of the vertebral canal, extending from the first cervical vertebra (C1) to around the second lumbar vertebra (L2) in adults.

What is the conus medullaris and what structure continues from it?

The conus medullaris is the tapered inferior end of the spinal cord. From it extends the filum terminale, a fibrous extension that attaches to the posterior wall of the coccyx.

What are the two enlargements of the spinal cord and their functions?

The spinal cord has two enlargements: the cervical enlargement (C3–C7) supplying the brachial plexus for upper limb innervation, and the lumbar enlargement (T10–L2) supplying the lumbosacral plexus for lower limb innervation.

How do the meninges protect the spinal cord?

The spinal cord is protected by three meninges: duramater (outer, forms filum terminale externum, with an epidural space), arachnoid mater (middle, thin and impermeable, forming the subarachnoid space containing CSF), and piamater (inner, adheres to the spinal cord surface and forms filum terminale internum).

What is the organization of gray and white matter in the spinal cord?

Gray matter (substantia grisea) is located centrally in a butterfly shape with anterior (motor) and posterior (sensory) horns. White matter (substantia alba) surrounds it and contains longitudinal nerve fibers divided into anterior, lateral, and posterior funiculi.

What is the function of the central canal?

The central canal runs through the center of the gray matter and contains cerebrospinal fluid (CSF), contributing to spinal cord nourishment and cushioning.

Which ascending tracts are responsible for sensory transmission?

The ascending tracts include: the fasciculus gracilis and cuneatus (discriminative touch and proprioception), the spinothalamic tract anterior (crude touch and pressure), and spinothalamic tract lateral (pain and temperature).

Which descending tracts are involved in voluntary and postural motor control?

Descending tracts include: corticospinal tracts (anterior and lateral) for voluntary movement, and extrapyramidal tracts such as tectospinal, vestibulospinal, reticulospinal, and rubrospinal for posture, balance, reflexes, and coordination.

How is the blood supply of the spinal cord organized?

The spinal cord is supplied by two main arteries: the anterior spinal artery, running in the anterior median fissure, and the paired posterior spinal arteries, running in the posterolateral sulci. Both originate from branches of the vertebral arteries.

What is the cauda equina and where is it found?

The cauda equina is a bundle of spinal nerve roots extending from the end of the spinal cord (conus medullaris) downward through the lumbar and sacral vertebral canal, resembling a horse’s tail.

Why is the cervical region of the spinal cord thicker in white matter?

The cervical region has more white matter due to the large number of ascending fibers from the lower regions (sensory input) and descending fibers to lower motor targets, making the tracts thicker compared to thoracic or lumbar regions.

What is the significance of the sulci and fissures in the spinal cord?

The anterior median fissure and posterior median sulcus, along with the posterolateral and anterolateral sulci, serve as anatomical landmarks that separate different funiculi of white matter and help organize ascending and descending nerve tracts.