External and Internal Anatomy of the Spinal Cord LO1, LO2 Flashcards
The spinal cord
External Anatomy of the Spinal Cord
long, thin, delicate tubular structure
- protected by the vertebral column
- ends between L1- L2 of the
vertebral column in adults
and L4 in infants
- terminates with conus medullaris
- anchored to the coccyx by the filum terminale
Spinal cord divided into:
- Cervcal 8
- Thoracic 12
- Lumbar 5
- Sacral 5
- coccygeal
- a pair of spinal nerves connects to each segment
Spinal nerves
Connect to the spinal cord by dorsal & ventral nerve roots
Dorsal - axons of sensory neurons
Dorsal root ganglion - cell bodies of sensory neurons
ventral roots - axons of motor neurons (somatic & autonomic)
Protection of the Spinal Cord
The spinal cord is protected from mechanical forces by:
- vertebral column
- cerebrospinal fluid –> also nourishes the neural tissue & removes waste products
- spinal meninges
Internal Anatomy of the Spinal Cord
The neural tissue (neurons & neuroglia) of the spinal cord:
- posterior (dorsal) median sulcus (top)
- anterior (ventral) median fissure (bottom)
- organised into areas of gray matter (inside) & white matter (outside)
Gray Matter of spinal cord
- Composed of neuron cell bodies (mainly), unmyelinated axons & neuroglia
- Encloses a central canal –> filled with cerebrospinal fluid
- Gray commissure - site where axons cross from one side of the CNS to the other
- divided into grey horns
Grey horns
- Sensory nuclei - Contain the cell bodies of spinal cord interneurons
- Autonomic motor nuclei - Contain the cell bodies of preganglionic neurons
- Somatic motor nuclei - Contain the cell bodies of lower motor neuron
White Matter ”conduction highway” spinal cord
- Superficial to gray matter
- Composed of myelinated (mainly) & unmyelinated axons
- Anterior white commissure –> site where axons cross from one side of the CNS to the other
- White columns contain ascending & descending
- spinal cord tracts = bundles of axons
Spinal Cord Tracts of the White matter
Conduct sensory or motor information between the spinal cord & brain
- ascending tracts –> conduct sensory input to the brain
- descending tracts –> conduct motor output away from the brain
Ascending tract
- Fasciulus gracilis
- Fasciulus cuneatus
- Lateral spinithalamic
- Anterior spinocerrbellar
- Posterior spinocerrbellar
- Anterior spinothalmic
Descending tract
- Lateral corticopsinal tracts
- Anterior corticopsinal tracts
Fasciulus gracilis
Sensory info come inferior part of the body
- Posterior white column
- fine touch, vibration, light pressure, Propicoertion
Fasciulus cuneatus
Sensory info come superior part of the body
- Posterior white column
- fine touch, vibration, light pressure, Propicoertion
Lateral spinithalamic
sensory info to thalamus
Lateral white coloumn
- pain, temperature
Anterior spinocerrbellar
Posterior spinocerbellar
conduct sensory info to cerebellum
Lateral white coloumn
Proprioception