Neuroanatomy | Corticospinal Tracts: Lateral and Anterior Pathways

Описание: 📚 Summary

We discuss the function and anatomy of the two corticospinal tracts: the lateral corticospinal tract and the anterior corticospinal tract.

The lateral corticospinal tract is responsible for fine motor movements as it controls the delicate distal limb muscles, whilst the anterior corticospinal tract is responsible for gross motor movements as it controls the bulky muscles of the proximal limb and trunk.

When discussing the anatomy of the corticospinal tracts, we begin in the primary motor cortex with our upper motor neurons. These upper motor neurons are organised somatotopically in the motor cortex, according to the motor homunculus. This somatotopy is retained in the posterior limb of the internal capsule, and also in the crus cerebri of the midbrain. The upper motor neurons then continue descending down the base of the pons to reach the pyramids of the medulla oblongata. This is where the upper motor neurons of the lateral corticospinal tract decussate (pyramidal decussation) to give contralateral control. Anterior corticospinal tract fibres instead partially decussate in the spinal cord (via the ventral white commissure) to give bilateral control.

In both corticospinal tracts, the upper motor neurons synapse with lower motor neurons in the ventral horn of the spinal cord. These lower motor neurons then exit the spinal cord via the ventral root and spinal nerve, before taking either the ventral or dorsal ramus to reach their target muscle.

This lesson provides a structured framework for understanding and remembering the corticospinal tracts in detail.

⏳ Timestamps

0:00 - 0:36 Overview
0:36 - 4:48 Function of Corticospinal Tracts
4:48 - 6:36 Upper versus Lower Motor Neurons
6:36 - 8:48 Lateral Corticospinal Tract Contralateral Control
8:48 - 10:32 Anterior Corticospinal Tract Bilateral Control
10:32 - 11:02 Summary of Contralateral versus Bilateral Control
11:02 - 11:34 The 5 Anatomical Sites
11:34 - 16:13 Site 1: Primary Motor Cortex
16:13 - 18:22 Site 2: Internal Capsule
18:22 - 22:08 Site 3: Brainstem (Crus Cerebri, Medullary Pyramids)
22:08 - 28:22 Site 4: Spinal Cord (Funiculi, Ventral Horn)
28:22 - 29:43 Site 5: Ventral Root
29:43 - 30:29 Summary of 5 Anatomical Sites
30:29 - 30:42 Thank You!

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