Block 1 - Gross - 8/23/06 - Spinal Cord & Nerves
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- On a cross section view through the T-spine from superficial to deep, what 4 things can you see?
- You can see the lamina, internal vertebral plexus, epidural fatty layer, and meninges
- What does the internal vertebral plexus function as?
- It functions as part of the venous drainage of the spinal cord
- Does the internal vertebral plexus have valves?
- It has no valves, which allows flow in both directions (towards head and towards feet)
- What is the clinical correlation of this lack of valves?
- Infectious material or metastasized tumors can flow in a bidirectional manner towards the brain or lower spinal cord areas
- So, because infection can travel throughout the spinal cord, can metastasized tumors do the same?
- Yes, they both can
- What does the epi, from epidural mean?
- It means outside or around
- Where is the epidural fatty layer in relation to the dura mater?
- It is just superficial to the dura mater
- What are the 3 parts of the meninges?
- The dura mater, the arachoid layer, and the pia mater
- What is the dura mater?
- It's appearance is opaque, and it is a thick, strong structure
- Is it the most external or most internal of the meninges?
- It is most external
- What is the arachnoid layer named after?
- It is named after spiders because the appearance is web or mesh-like
- What is an important feature of the arachnoid layer functionally?
- It is a water-tight membrane
- What is deep to the arachnoid layer?
- The subarachnoid space is directly deep to it
- What is in the subarachnoid space?
- The cerebral spinal fluid is located there
- What is the subarachnoid space also known as?
- It is also known as the thecal space
- What is the clinical correlation?
- When injecting into the CSF, it will sometimes be called an intrathecal injection
- What does CSF bathe?
- It bathes the central nervous system
- What is CSF generated by?
- It is developed by cells in the cranial cavity and circulated around through the thecal space and ventricles
- In a living human, the CSF has a higher hydrostatic pressure than surrounding tissue. What does this do to the Arachnoid layer versus the dura mater?
- The pressure pushes the arachnoid layer against the dura mater
- Why is this not the case in the dura mater?
- In cadavers, the CSF has drained out
- How does the pia mater relate functionally to the spinal cord?
- It is so tightly bound to the spinal cord that you cannot separate it from the spinal cord on the cadavers in most cases
- What is the first exception to this?
- The denticulate ligaments, which will be seen between the ventral and dorsal rootlets of the cadavers
- What is the second exception?
- Filum terminale is found between the end or tip (conus medularis) of the spinal cord and the coccyx
- What is the filum terminale?
- It is a firm attachment ot the coccyx that is taught (anchors the inferior portion of the spinal cord)
- What do we refer to the denticulate and filum terminale as?
- We refer to them as pia specializations
- What do the denticulate and filum terminale do?
- They function to hold the spinal cord in place and prevent it from hitting the sides of the vertebral canal or "bumping" against the dura mater
- Where do the meninges extend laterally?
- They extend out toward the dorsal root ganglion and fuse with the epineurium there
- What is the epineurium?
- It is the outer layer of connective tissue covering nerves
- There are both _____ and _____ dorsal rootlets at each spinal nerve
- dorsal, and ventral
- What is the bulging point of the dorsal root?
- It is the dorsal root ganglion (DRG)
- What type of cell bodies are found in the DRG?
- The afferent cell bodies
- What does the H-pattern appearance on cross sectional views of gray matter refer to?
- The gray matter of the spinal cord indicates the round ventral horn portion and the more pointed dorsal horn portion
- The white matter is internal or external to the gray matter?
- It is external to the gray matter
- Where does the spinal cord end, and what is the name of the structure?
- It ends at the L2 level at the structure called the Conus Medularis
- When the pia mater continues past the conus medularis, what does it form?
- The filum terminale
- The dura mater and arachnoid layer continue unconnected to the filum terminale until what level where they join the filum terminale
- This connection occurs at the S2
- What is the proximal part where the filum terminale is continuing alone called?
- It is called the pars internis
- What is the distal part where the dura mater and arachnoid layer meet called the filum terminale called?
- It is called the pars externis
- What is the pars externis also known as?
- It is also known as the coccygeal ligament
- Where are the 2 swellings of the spinal cord located?
- They are located ain the cervical and lumbar regions
- Why are they swollen?
- Because there are more cells present
- How does the angle of spinal cord rootlets change as we move inferiorly?
- The rootlets are found with more and more of an angle before they exit through their respective intervertebral foramen
- In the cervical region the rootlets are where relative to their respective vertebral bodies?
- They are at the same levels as their vertebral bodies
- When you see the lumbar rootlets starting to come off the spinal cord at the ____ vertebral level, they exit much lower in the lumbar region
- T10
- The spinal cord ends at _____.
- L2
- Why does the arrangement of spinal nerves innervating structures below L2 exist?
- It is like that because at the development level of a child, the spinal cord has reached its maximum size, but the vertebral column has not, and so it will continue to grow
- The spinal nerves that need to exit lower than L2 do so by?
- They "stream" inferior seeking another exit
- The appearance of all these rootlets in the lumbosacral region going inferior before leaving through their respective intervertebral foramen looks like what?
- It looks like a horses tail
- This gives it the name?
- Cauda equina
- How many cervical nerves are there versus how many cervical vertebrae?
- There are 8 nerves and 7 vertebrae
- Where does the C8 spinal nerve exit relative to the vertebrae?
- It exits below the C7 spinal vertebra
- What is a result of this C7/C8 interaction for inferior vertebrae/nerves?
- The remaining spinal nerves exit below their corresponding vertebra
- What is the dorsal root ganglion?
- It is a bulging of the dorsal root where afferent cell bodies are foun
- What does the dorsal root ganglion bifurcate into?
- It bifurcates into the dorsal and ventral rami
- What are dermatomes?
- Patches of skin innervated by a particular spinal nerve
- C5 corresponds to what?
- Shoulder
- T4 corresponds to what?
- Nipples
- T10 corresponds to what?
- Belly
- L1 corresponds to what?
- Groin
- S2-S3 corresponds to what?
- Genitalia
- Review the identification of the intervertebral discs
- Add 1 to the disc number to determine which nerve is involved
- Why is this?
- This is because the intervertebral foramen allows the spinal nerves to exit above the disc of the same number (more of the foramen is formed by the superior notch than the inferior notch)
- Is the intervertebral foramen a large or small space?
- It is a small space (just enough for the nerve to go through)
- What does this mean from a pathological standpoint?
- Even a small evulsion of the disc can cause pathology
- What happens in a dermatome exam?
- The clinician tests patches of skin for sensation, via light touch or pain with a pin
- CNS is?
- Brain and spinal cord
- Both CNS and PNS can be what two things?
- Motor (efferent) or sensory (afferent)
- Somatic involves?
- Voluntary movement (both sensory and motor)
- Visceral movement involves?
- Autonomic nervous system (involuntary or automatic and involves both sensory and motor)
- What is a sensory example of the visceral system?
- Regulation of abdominal organs and blood vessels
- What are motor examples of the visceral system?
- Smooth muscle, heart muscle, glands such as sweat glands