Week 2 LO Questions

Explain the anatomical basis of the common findings that disc herniations at the L4/L5 and L5/S1 IV (intervertebral) discs present with symptoms consistent with involvement of the L5 and S1 spinal nerves, respectively.

Lumbar nerves exit inferior to their associated vertebra Lumbar IV disc herniations usually impinge nerve level associated with infra-adjacent vertebra L4/L5 IV disc herniation and L5 spinal nerves L5/S1 IV disc herniation and S1 spinal nerves

Specify the spinal cord level of origin of preganglionic sympathetic neuron cell bodies that innervate 1) thoracic viscera, and 2) abdominopelvic viscera.

Thoracic viscera (e.g. heart) Usually located in spinal cord levels T1-T5 Abdominopelvic viscera Usually located in spinal cord levels T5-L2

Specify the locations of the preganglionic parasympathetic neuron cell bodies whose fibers travel in the vagus nerve and in the pelvic splanchnic nerves.

Vagus nerve / cranial nerve 10 (CN X) Preganglionic parasympathetic neuron cell bodies originate in the gray matter of the brainstem Innervates all thoracic and abdominal viscera Preganglionic fibers bypass cranial nuclei and synapse on terminal ganglia embedded within the organ walls where postganglionic neurons located Pelvic splanchnic nerves Preganglionic parasympathetic neuron cell bodies located in the S2 - S4 spinal segments

Explain the anatomical basis of the dermatomal rash pattern characteristic of a herpes zoster infection.

Varicella zoster virus (VZV) lays dormant in a dorsal root ganglion (DRG) and when it becomes activated causes vesicular rashes (shingles/herpes zoster) in a dermatomal pattern

Identify the adult derivatives of the notochord.

Centrum (body) of each vertebra is formed by sclerotome cells that surround the notochord; as sclerotome cells differentiate, notochordal cells in the region of body of vertebra regress and eventually disappear Notochord persists and enlarges in the space between adjacent vertebral bodies - forming the nucleus pulposus or inner core of intervertebral discs

List the five types of vertebrae and indicate the number of vertebrae of each type.

Cervical (7), thoracic (12), lumbar (5), sacral (5), and coccygeal (4 fused)

Be able to predict the spinal nerve affected by IV disc herniations at specific locations in the cervical and lumbar region of the vertebral column.

Cervical IV disc herniation Usually affects the nerve in that foramen (e.g. C5/C6 IV herniation affects the C6 nerve); nerves exit above associated vertebrae in cervical region Lumbar IV disc herniation Usually impinge nerve level associated with the infra-adjacent vertebrae (e.g. L4/L5 IV herniation affects L5)

Specify the distinguishing features of cervical, thoracic and lumbar vertebrae.

Cervical vertebrae; bifid spinous process, vertebral foramina, atlas vertebra (C1), axis vertebra (C2), uncinate process Thoracic vertebrae; costal facets Lumbar vertebrae; mammillary process, thickest vertebral body

List the four ganglia of the head that house postganglionic parasympathetic neuronal cell bodies.

Ciliary, otic, pterygopalatine, submandibular

Describe the curvatures (normal and abnormal) of the vertebral column and explain their development; be able to identify these curvatures in images of the spine.

Degree of curvature of normal curves of spine varies considerably among individuals and throughout an individual's lifespan Cervical lordosis, thoracic kyphosis, lumbar lordosis

Compare the actions of the intrinsic back muscles on the vertebral column with those of the muscles of the abdominal wall and the deep muscles of the anterior and lateral neck.

Intrinsic back muscles are assisted by muscles of the anterior and posterior abdominal walls to generate movements of thoracolumbar spine; also assist in stabilizing the spine and maintaining posture

List in order from superficial to deep the structures the needle will pass through when performing a lumbar puncture.

Ligamentum flavum, dura mater, arachnoid mater, cisternal subarachnoid space

Specify the spinal cord segments that contain the preganglionic sympathetic neurons involved in the innervation of head and neck structures.

Located in the T1-T4 region of spinal cord; axons ascend in sympathetic chain to synapse in postganglionic sympathetic neurons located in the inferior, middle, or superior cervical ganglia

Identify the adult derivatives of somites.

42 - 44 pairs of somites formed 1 - 4 → structures in the head 5 - 7 caudal most → degenerate as the embryo loses its long tail 31 - 33 remaining → contribute to formation of axial skeleton, skeletal muscles of body wall and limbs, and dermis of skin

Relate the intervertebral foramina of the spinal column to somite differentiation.

Development of vertebral column begins when sclerotome cells on each side of the notochord and developing spinal cord migrate to merge with cells from opposite side Once in place each cluster of sclerotome cells splits to cranial and caudal Caudal half of each sclerotome fuses with cranial half of the sclerotome below to form primordium of single vertebra Each vertebra is formed from two adjacent somites Tough circular exterior of intervertebral disc (annulus fibrosis) is derived from sclerotome as are associated vertebral ligaments

List from external to internal the three spinal meninges.

Dura (mater), arachnoid (mater), pia (mater)

Explain how the postganglionic sympathetic fibers destined to innervate structures in the head and neck reach travel to reach their target organs.

Either traveling with branches of the cervical spine nerves or by traveling along the surfaces of blood vessels

Describe the relationship between the anatomy of the anterior and posterior longitudinal ligaments of the spine and the typical direction of intervertebral disc herniation; be able to identify disc herniations in MRIs of the spine.

IV disc herniation typically occurs posterolaterally on either side of the posterior longitudinal ligament

Relate sympathetic and parasympathetic motor pathways to the transmission of visceral sensation to the central nervous system (CNS).

In order to send a motor impulse from the CNS to the visceral effector organ in the PNS, a preganglionic neuron synapses on a postganglionic neuron and forms a two-neuron chain. The preganglionic neuron resides with the CNS and its axon synapses on a postganglionic neuron located in a peripheral autonomic ganglion

List the paravertebral (chain) ganglia that contain the postganglionic sympathetic neuronal cell bodies that innervate head & neck structures.

Inferior, middle, and superior cervical ganglia

Explain the relationship of the external abdominal oblique to the inguinal ligament and the inguinal region.

Inguinal ligament is the thickened, unattached inferolateral border of the external oblique muscle Inguinal region is junction between anterior abdominal wall and anterior thigh Two passageways in inguinal region for structures to pass to and from the abdominopelvic cavity

Explain the developmental basis of the medullary cone occurring at the L1 vertebral and its effect on the relationship between the spinal cord level of origin and location of vertebral canal exit for the lower lumbar and sacral spinal nerves.

Medullary cone (L1/L2) is bottom of spinal cord; point of spinal cord termination Cauda equina and CSF are located inferior to medullary cone Vertebral column and spinal cord develop at different rates (spinal cord is slower) L5 spinal cord level is located superior to its associated L5 vertebral level while the nerve root courses below its associated vertebra Lumbar and sacral nerve roots form below conus medullaris

Distinguish the anatomical locations of paravertebral and pre-aortic (prevertebral) sympathetic ganglia.

Paravertebral ganglia (sympathetic chain ganglia) Found adjacent on both sides of vertebral body; beads on a string; approximately 1 ganglia per vertebral level Prevertebral ganglia (preaortic ganglia) Located on top of the aorta

Describe the anatomical locations of the cell bodies of the preganglionic and postganglionic neurons of the parasympathetic division.

Preganglionic → brainstem and grey matter of spinal cord from S2 - S4 Postganglionic → cranial and terminal (inside organ walls) ganglia

Describe the anatomical locations of the cell bodies of the preganglionic and postganglionic neurons of the sympathetic division.

Preganglionic → located in a region called the lateral horn which is found only at T1 - L2/L3 spinal cord levels Postganglionic → located in either paravertebral (sympathetic chain) ganglia or prevertebral (pre-aortic) ganglia

List the subdivisions of a somite.

Sclerotome, dermatome, myotome, epaxial, and hypaxial portions

Categorize each of the following structures as carrying sensory fibers, motor fibers, or both: ventral root, dorsal root, spinal nerve, ventral primary ramus, and dorsal primary ramus.

Sensory fibers → dorsal root Motor fibers → ventral root Both → spinal nerve, ventral primary ramus, dorsal primary ramus

List, in order of their activation, the five components of a reflex arc.

Sensory receptor in periphery Afferent neuron One or more integrating synapses within the CNS Efferent neuron Effector organ

List in correct spatial sequence, the structures through which a somatic efferent axon will pass in projecting to its effector organ in the ventrolateral or dorsal body wall.

Somatomotor pathway Neuron in ventral horn of spinal cord → somatic efferent axon goes to the anterior (ventral) root → spinal nerve → synapse on effector organ

List in correct spatial sequence, the structures through which a somatic afferent axon will pass in returning sensory information to the CNS from a receptor in the ventrolateral or dorsal body wall.

Somatosensory pathway Sensory receptors → information moves through spinal nerve → dorsal root → CNS processing

Explain the anatomical basis of performing a lumbar puncture at the level of the L3/L4 intervertebral disc.

Supracristal plane transects highest point of iliac crest and usually passes through spinous process of the L3 vertebra; little danger of damaging spinal cord at this level

Specify the principle routes of venous blood flow through the dural venous sinuses.

Venous blood from brain drains into the dural venous sinuses Superior sagittal sinus → confluence of sinuses (unites with straight and occipital sinuses) → transverse sinuses → sigmoid sinuses → internal jugular veins Inferior sagittal sinus → straight sinus → confluence of sinuses (unites with superior sagittal sinus and occipital sinus) → transverse sinuses → sigmoid sinuses → internal jugular veins