Anatomy and Cell Biology 3309 Lecture Notes - Lecture 2: Dura Mater, Cerebrospinal Fluid, Dorsal Root Ganglion
22 May 2018
School
Department
Professor
Histology 3309
Spinal Cord and Ganglia
The Spinal Cord
- Embedded into the vertebrates
- Can be divided into sections
o Cervical
o Thoracic
o Lumbar
o Sacral
- Spinal cord actually ends at the beginning of the lumbar section (so spinal cord only runs
through the cervical and thoracic part of ventral colum
- From there downwards, is called the cauda equina (bundle of nerves)
- Segmentation of spinal cord is according to where its nerves leave the vertebral column to go to
other parts of body
Roots & Nerves
- Spinal cord is embedded in boney structures (protected by the vertebrates
- Ventral (front side) and dorsal (back side)
- Spinal cord gives rise to all these nerves that travel to the periphery of the body and form the
PNS
- Bw each vertebrate, there are little nerves that leave the spinal cord (a bunch of dorsal and
ventral side)
o The nerves on the ventral side are the motor neuron axons leaving the spinal cord
(afferent)
o The nerves on the dorsal side are the incoming sensory fibers (efferent)
o These together form a common joined nerve, called mixed nerve (mix of afferent and
efferent nerves)
- Dorsal root ganglion
o Thickening of nerves
- Spinal cord is solid mass with dorsal and ventral roots , which is also wraps into the meninges
- There is a dura mater that wraps around the spinal cord, which is continuous with the dura
mater that wraps around the brain
- Theres also an arachnoid and the pia mater
- The pia matter around the spinal cord is attached to some denticulate ligament (ligaments that
are dentured – have connections to dura mater and arachnoid)
o This connect the pia matter to the dura mater and arachnoid
o There to stabilize the spinal cord within that area it is located in
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Gray & White Matter
- White matter surrounds gray matter that is central to spinal cord
- White matter has a lot of myelinated axons
- Brown area= grey matter
- DH = dorsal horn
- VH= ventral horn
- Dorsal horn and ventral horn are connected by grey commissure (fiber tract that connects diff
areas within the brain)
o Normally, commissure is white matter, but in the spinal cord the commissure that
connects the left and right parts is grey
o This is bc they are unmyelinated axons (bc its short)
- Spinal cord is about 1 cm thick
o This varies depending on where you look at the spinal cord
o Thicker on upper portion
o Gets thinner on lower portion (this is bc the axons branch off so by the time you get to
the very bottom, there is not that many left)
- Hole in middle= central canal filled with cerebral spinal fluid (continuous with all the ventricles
in the brain)
- Ventral fissure
- Big motor neurons lie in the ventral horns,
- Sensory input comes in through the dorsal horns
o Little nerves come in and reach dorsal horn, makes synapses with interneurons, then big
motor neurons lie in the ventral horn that send their axons out of the spinal cord into
the periphery along some big nerves to any of your muscles
- The biggest neurons in a spinal cord section lie in the ventral horn
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Cell Types in the Spinal Cord
- Depending on what stain you use, you can see the big cell bodies, nucleus, nucleolus and some
proximal parts of the dendrite of the biggest neurons in the ventral horn
- Ependymal cells can also be visible
o One of 4 cavities of CNS
o Ependymal cells line the cavities (ventricles) and the central canal
o Secrete cerebral spinal fluid and keep it moving using their microvilli and stereocili
The Nervous System
- Morphological Divisions
o CNS
▪ Brain
▪ Spinal cord
o PNS
▪ Cranial, spinal and peripheral nerves
▪ Ganglia (outside CNS)
▪ Sensory receptors
o Single cells (ex: motro neuron in spinal cord) can be apart of both PNS and CNS bc their
cell body lies in ventral horn but their axon goes into the nerve
- Functional divisions
o Somatic
▪ Body parts of CNS, PNS (effectors: striated muscles)
o Autonomic
▪ Afferent sensory information from viscera
▪ Motor innervation to smoot muscles, heart, glands
▪ Sympathetic and parasympathetic system
▪ There is a clear division along the spinal cord of the SYN and PSYN
o Somatic and autonomic nervous systems share common nerves and substrates
o Enteric
▪ Gastrointestinal system
Somatic Reflex Arc
- Simpliest form of sensory input and motor output of CNS which does not require the brain
- Stays within one segment of spinal cord
- Only needs 3 serial neurons
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Document Summary
Can be divided into sections: cervical, thoracic, lumbar, sacral. Spinal cord actually ends at the beginning of the lumbar section (so spinal cord only runs through the cervical and thoracic part of ventral colum. From there downwards, is called the cauda equina (bundle of nerves) Segmentation of spinal cord is according to where its nerves leave the vertebral column to go to other parts of body. Spinal cord is embedded in boney structures (protected by the vertebrates. Ventral (front side) and dorsal (back side) Spinal cord gives rise to all these nerves that travel to the periphery of the body and form the. Dorsal root ganglion: thickening of nerves. Spinal cord is solid mass with dorsal and ventral roots , which is also wraps into the meninges. There is a dura mater that wraps around the spinal cord, which is continuous with the dura mater that wraps around the brain. Theres also an arachnoid and the pia mater.
