• Central Nervous System (CNS): Brain, Spinal cord
• Peripheral Nervous System (PNS): Cranial nerves(12 pair), Spinal nerves (31 pair)

• Cervical nerves (8)
• Thoracic nerves (12)
• Lumbar nerves (5)
• Sacral nerves (5)
• Coccynea nerve (1)

• Dorsal series (Posterior)
• Ventral series (Anterior)

Both part of Peripheral nervous system

• Dura Mater
• Arachnoid
• Pia Mater

They are membrane layers.

The space between the Arachnoid and the Pia Mater

• Primary sensory neurons (afferent neurons)
• Spinal motor neurons (efferent neurons)

• Relay input from the periphery to the spinal cord.
• Pseudounipolar cells.
• Cells body located in clusters(ganglia) OUTSIDE the spinal cord.

• Relat out put from spinal cord to the periphery.
• Multipolar cells
• Cell bodies located in clusters (nuclei) WITHIN spinal cord motor columns.

• General somatic afferent (GSA): Neurons relaying general sensation and muscle proprioception (position sense) from the body wall and limbs.
• General somatic efferent (GSE): Neurons relaying motor innervation to skeletal muscl derived from myotomes.

• General visceral afferent (GVA): Neurons relaying general sensation from viscera (internal organs)
• General visceral efferent (GVE): Neurons relaying motor innervation to viscera. The visceral motor system is referred to as the autonomic nervous system.

GVE

• Neuron #1: Perganglionic(=presynaptic) neuron. Lateral horn of gray matter.
• Neuron #2: Post ganglionic (=postsynaptic) neuron.

Component of Spinal cord.

A deep, longitudinal cleft along the ventral midline

Component of spinal cord.

Component of spinal cord

A shallow groove along the anterior lateral side of the cord, marking the line of attachment of the ventral rootlets

Compnent of spinal cord

§  The H-shaped inner core of tissue, composed largely of nerve cell bodies

·         Dorsal (posterior) horn: Houses mainly cell bodies of interneurons that receive input from afferent neurons and/or other interneurons

·         Ventral (anterior) horn: Houses mainly cell bodies of spinal motor neurons

·         Lateral (intermediolateral) horn:o   Houses cell bodies of preganglionic autonomic neuronso   Restricted to cord levels T1-L2/3 & S2-4

 Peripheral columns of tissue surrounding the gray matter

·         Composed mainly of neuron processes, neuroglia, & blood vessels.

·         The large proportion of myelinated fibers gives a white, glistening color in fresh tissue

·         The lumen of the neural tube, containing cerebrospinal fluid.  This is continuous with the ventricles within the brain

The tapered, terminal end of the spinal cord.

During spinal cord formation

During spinal cord formation

§  fuses together to form a single spinal nerve

·         Cauda equina: Horse’s tail-like bundle of nerve roots extending below the conus medullaris

Dorsal/Ventral Primary Rami

The portion of the spinal cord that gives rise to each paired set of spinal rootlets/roots/nerves

§  Distribute to epaxial tissues

·         Epaxial = above the axis

·         Any muscle that forms out of the epimere is innervated from the dorsal primary rami

·         Intrinsic muscles of the back = deep muscleso   These come from the epimere

• Pachymeninx("thick membrane") 
• Strong, fibrous membrane that forms the most superficial layer of meninges.
• Covers nerve roots. Fuses with the vertebral periosteum and the epinuereum at the intervertebral foramina.
• Lines vertebral canal to the level of about S2.
• Filum terminale externum. Terminal strand continuation of dura that extends down to a final attachment in the coccyx.

Leptomeninge ("thin membrane")

• A delicate membrane that forms the middle layer of the meninges.
• Lines deep aspect of the dura throughout its extent.
• Arachnoid trabeculae: The network of arachnoid fibers that connect the arachnoid and pia mater.

Leptomeninge("thin membranes")

• The delicate membrane that forms the deep layer of meninges.
• Lines the exterior surface of the CNS and spinal nerve rootlets and roots.
• Fuses with epineurium at the intervetebral foramina.
• Dentate(denticulate) ligaments: Lateral tooth-like extensions of pia that attach to the dura between the segmented nerve roots.
• Filum terminale internum: Terminal strand continuation of pia beyond the conus medullaris. Forms the core of the cauda equina. Finally fuses with the filum terminale externum.

• Space surrounding spinal cord.
• Right above Dura mater

• Space surrounding CNS.
• Looks like teeth-shaped opening right between the Arachnoid and the Pia Mater

• Embryonic weeks 3-4

• Thickened surface ectoderm induced by development of notochord.

• A longitudinal midline depression in the neural plate. It progressively deepens to form neural canal.

• The elevated lateral edges of the neural plate.
• Deepening of the neural groove plus growth of the neural plate cause the neural folds to rotate dorsalward around the hinge-like axis of the neural groove.

• The structure formed by the dorsal midline fusion of the neural folds.

• The lumen of the neural tube.

• Temporary open connections between the central canal and the amniotic cavity at the cranial and caudal ends of the neural tube.

• produce a closed, tubular CNS characterized by a boader cephalic portion(brain) and a narrow caudal portion(spinal cord)
• This marks the completion of neurulation

• Dorsal outgrowths: Produce neural arch
• Lateral outgrowths: Produce costal processes (rib primordia)

also called vertebral arch

• The dorsal outgrowths of each mesenchymal vertebral body grow around the neural tube, between the segmental(spinal) nerves, and fuse in the midline, dorsal to the neural tube, thus forming a complete neural arch.
• Neural tube closure induces formation and closure of neural arch during weeks 3-5.

• Congenital anomaly characterized by failure of the neural arch elements to fuse with one another in the dorsal midline, resulting in an open(cleft) vertebral canal.
• Most common in Sacral and Lumbar regions.
• Spina bifida occulta
• Spina bifida cystica

• Paired neural arch elements fail to meet at dorsal midline.
• Get a tuft of hair or a dimple that forms.
• Asymptomatic
• Neural tube is intact and meninges are around it.

• chaacterized by fluid filled sac that pertrudes.
• Meningocele: spinal cord remains in place. Defect in dorsal midline. Enlarged subarachnoid space. May or may not have neurologic effects. Dura/arachnoid become incorporated in skin.
• Meninggomyelocele: Displacement of spinal cord. There will be neurological defects.
• Myelocele: Most severe. Incomplete neural tube. Spinal cord is open and form at the wall of the cyst. (right under surface of skin)

• The terminal end of the spinal cord.
• Around L1

• Formed be dorsal and ventral roots seperated from the end of the spinal cord.
• Roots still exit from their respective intervetebral formamina

• They grow at different rates.
• They start off the same size but the spinal cord seems to shrink as the conus medullaris goes higher.

• Disk herniations tend to affect the next nerve down the chain.(for about C5 and lower)
• For example, c5 herniation affects C6 nerve.

• The Dura mater and Arachnoid are being penetrated to reach the cerebrospinal fluid (CSF) located in the subarachnoid space.

• To get the CSF
• Often done in suspected cases of meningitis. Usually on infants when they have a high temperature without an apparent cause.
• May also be done to inject medications into the CSF. Spinal anesthesia and Chemotherapy are examples.

Usually between L4-L5

Also has nice interlaminar space.

NOT L3, some people may hay spinal cord there.

• Can have problems if there are any significant changes in CSF pressure.