Anatomy of the spinal cord and vertebral column Flashcards
What are the layers of the spinal meninges?
- Dura mater
- Arachnoid mater
- Pia mater
Describe the dura mater
Thick inelastic outer covering
Richly innervated by sensory nerve endings
Surrounds spinal cord from fusion at cranium down to the level of S2 vertebra
Provides maximum protection to the cord
What is the epidural space?
Also known as extradural space
Space between the vertebral canal walls and the spinal dural sac. It contains fat and blood vessels.
Describe the arachnoid mater
Lies beneath dura mater (not connected)
Avascular
Extends to the level of S2 vertebra
Bridges the subarachnoid space with small filaments
Describe the pia mater
thin inner layer
intimately covers the cord
At cervical and thoracic levels = denticulate ligaments
What are the denticulate ligaments?
Small ligaments that extend laterally and help anchor the cord to the dural sac
What happens to the pia mater at the conus medullaris?
Forms the terminal filum, a single cord of tissue that pierces the dural sac at the S2 vertebral level, acquires a dural covering, and then attaches to the coccyx to anchor the spinal cord inferiorly
What is the subarachnoid space?
A space between the arachnoid mater and the pia mater that is filled with CSF
Where is CSF secreted?
Choroid plexus
Where is CSF absorbed?
arachnoid granulations and secondarily by small veins on the surface of the pia mater
How much CSF is produced per day?
~500ml
What is the dorsal root ganglion?
A collection of neurons in the periphery
Usually contains a sensory pseudounipolar neuron
What is the dorsal ramus?
A small ramus that courses dorsally to the back and conveys motor and sensory information to and from the skin and the intrinsic back muscles and suboccipital skeletal muscles
What is the ventral ramus?
A much larger ramus that courses laterally and ventrally and innervates all the remaining skin and skeletal muscles of the neck, limbs and trunk.
What is the cauda equina
The bundle of nerve roots below the level of the conus medullaris.
Cauda equina = horse’s tail
What is the terminal filum?
The pial extension that anchors the spinal cord inferiorly to the coccyx.
Where is the ventral aspect?
Towards the body of the vertebrae (abdominal region)
Where is the dorsal aspect?
Towards the spinous processes of the vertebrae (the back region)
Where is grey matter derived from?
The alar plate
What are the different areas of the grey matter?
- Dorsal horn
- Intermediate horn
- Ventral horn
What are the different areas of the white matter
- Dorsal funiculus
- Lateral funiculus
- Ventral funiculus
What areas of the body does the cervical spine innervate?
The neck, upper chest and most of the forearms
What areas of the body does the thoracic spine innervate?
The trunk, thin strips down both forearms
What areas of the body does the lumbar spine innervate?
The lower limbs
What areas of the body does the sacral spine innervate?
The genitalia
Describe the white/grey matter distribution in the cervical region of the spinal cord
Dorsal and ventral horns within grey matter relatively large as supplying the limbs
Describe the white/grey matter distribution in the thoracic region of the spinal cord
Dorsal and ventral horns within grey matter relatively small as relatively insensitive in chest and abdomen, and muscle groups do not need fine motor control
Describe the white/grey matter distribution in the lumbar region of the spinal cord
Dorsal and ventral horns within grey matter relatively large as supplying the limbs
Describe the white/grey matter distribution in the sacral region of the spinal cord
Dorsal and ventral horns pretty equal in size but smaller relative to cervical and lumbar regions
What is a spinal segment?
The region of the spinal cord that contains a pair of nerve roots that innervates the corresponding dermatome and myotome
What is CSF
A filtrate of blood that affords mechanical and immunological protection to the brain and spinal cord
What are Baston veins?
A venous plexus that runs the entire length of the spinal column within the epidural space
What are the key features of Baston veins?
They do not contain any valves
Name the main arterial supply to the spinal cord
- Vertebral arteries
- Ascending cervical arteries
- Posterior intercostal arteries
- Lumbar arteries
- Lateral sacral arteries
What is the artery of Adamkiewicz?
The largest segmental artery that is found in the lower thoracic or upper lumbar region.
Major blood supply for the lower 2/3 of the cord
Describe the arterial supply to the spinal cord
Largely on a segmental basis.
A single anterior spinal artery and two posterior spinal arteries
The aorta sits anteriorly
You’ll get segmental arteries at the various intercostal levels and these will branch off and fuse to supply the spinal cord itself.
