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Describe the embryology of the vertebral column, including development of the intervertebral discs. Notochord is a solid cylinder of mesoderm extending in the midline of the trilaminar embryonic disk from the primitive node to the prochordal plate. a. It induces the overlying ectoderm to differentiate into neuroectoderm to form the neural plate. b. It induces the formation of the vertebral body of each of the vertebrae. c. It forms the nucleus pulposus of each intervertebral disk. Notochord- develops by transformation of notochordal process, signals development of many structures
- Defines primitive axis of embryo and gives some rigidity & indicates future site of vertebral column
- Steps in development:
- Primitive pit extends into elongating notochordal process, forming notochordal canal
- Floor of notochordal process fuses with underlying endoderm
- Fused regions undergo degeneration resulting in formation of openings in floor of notochordal process, bringing notochordal canal into communication with yolk sac
- Openings become confluent and notochordal canal disappears; remains of notochordal process form grooved plated called notochordal plate
- Small passage, neurenteric canal temporarily connects amniotic cavity and yolk sac; this obliterates when development of notochord complete
- At cranial end, notochordal cells proliferate and notochordal plate infolds to form notochord
- Notochord becomes detached from endoderm, which again becomes continuous layer, roof of yolk sac
- Developing notochord induces overlying ectoderm to form neural plate, primordium of central nervous system Note: Although the notochord “induces” the development of the central nervous system (process of neuralation), it itself does not become any nerve tissue at all. In this case, the notochord’s important function is to “tell” the overlying ectodermal tissue to “become a neural plate”
- Notochord, though a dramatic structure in early embryology, degenerates as vertebral bodies form, persisting after birth only as miniscule structures, the nucleus pulposus, or pulpy, central area of each intervertebral disc Primitive streak - > primitive node + pit - > primitive groove - > mesenchyme - > notochordal process - > notochord Identify the surface anatomy landmarks for locating the spinous processes of the C2, C7, T3, T7, L4, L5, and S2 vertebrae. C2-first spinous process C7-first big bump T3-spine of the scapula T7-bottom of scapula L4-top of iliac crest L5-superior bone of Lumbrosacral junction S2-posterior superior iliac spine List the functions of the vertebral column.
- Protects spinal cord
- Supports weight of head and trunk
- Movement of rib cage for respiration by articulating with ribs Describe the bony features of typical, atypical, and unique vertebrae and the ligaments and/or muscles that attach to them. Typical
- body: short cylinder, supports weight, separated from each other and bound by intervertebral disks à cartilaginous joints; on thoracic vertebrae there are costal facets to articulate with ribs
- vertebral/neural arch: paired pedicles laterally and paired laminae posteriorly; forms vertebral foramen with body to protect spinal cord Processes:
Atlas: - no spinous process, vertebral body, articular disks ; +anterior arch/posterior arch/transverse processes with transverse foramen (vertebral artery/vein) +widest C vertebrae +supports the skill like atlas supported earth +articulates - superiorly with occipital condyles of skull to form atlanto-occipital joints= (move head up and down yes)
- inferiorly with axis to form atlantoaxial joint: shake head no Axis: - spinous process is not bifid (attachments site for nuchal lig) +has dens=odontoid peg (allows head rotation) Describe the bony features of the scapula and posterior aspects of the ribs. Describe the craniovertebral , intervertebral , and costovertebral joints. Craniovertebral: occiput, atlas, and axis Intervertebral: symphysis between adjacent vertebrae and intervertebral disc costovertebral: head of ribs with bodies of thoracic vertebrae
Differentiate between the primary and secondary curvatures of the spine. Primary: thoracic and sacral; develop during embryonic periods Secondary: cervical and lumbar after birth and infancy Describe the difference between the extrinsic and intrinsic back muscles. Extrinsic: superficial and move the upper extremities and shoulder Intrinsic: deep and control posture and movement of spine and head Describe the muscles of the back, from superficial to deep, and their origins and insertions (ie, proximal and distal attachments). Identify the nerves that innervate the back muscles. Describe the major actions of the muscles mentioned above. Describe the effects of unilateral and bilateral contractions of the erector spinae muscles to produce extension, lateral flexion, and rotation of the vertebral column. Contrast the movements found in the cervical, thoracic, and lumbar regions of the spine.
Ligamentum flavum: connects the lamina of adjacent vertebrae
Nuchal ligament: from occipital protuberance to C7 spinous process, attachment point for trapezius and splenius capitus Describe the structure and function of an intervertebral disc. Form joints between bodies of two vertebrae; shock absorbing
- Nucleus pulposus: remnant of notochord, in central (nucleus)
- Annulus fibrosus: binds vertebral column together and retains the nucleus pulposus to prevent herniating/protrusion à impinge on roots of spinal nerve in intervertebral foramen or vertebral canal; MCC: posterolaterally when not reinforced by posterior longitudinal ligament (lumbar region) Identify the location of the zygopophysial (facet) joints and compare them in the cervical, thoracic, and lumbar regions. Transverse costal facet–connects tubercle of the rib and the transverse process of thoracic vertebrae (via costotransversejoint)
- Describe the major actions of the suboccipital muscles. Blue: rectus capitis—extend and rotate the atlanto-occipital joint Green: Oblique capitis superior muscle-extend and flex head at atlanto-occipital joint Red: obliquues capitius inferior: rotation of head at atlanto-axial joint Contents: 1. Vertebral artery (third part) 2. Dorsal ramus of C1 (suboccipital nerve) 3. Suboccipital venous plexus - Describe the course of the vertebral artery (origin and destination), as well as, its common anatomic variations. origin: branch of the 1st part of the subclavian artery course: ascends posterior to the internal carotid artery in the transverse foramina of the cervical vertebrae branches: posterior inferior cerebellar artery (PICA) termination: combines with the contralateral vertebral artery to form the basilar artery key relationships: posterior to the internal carotid artery; ascends anterior to the roots of the hypoglossal nerve (CN XII)
- V1 (preforaminal): origin to transverse foramen of C
- V2 (foraminal): from the transverse foramen of C6 to the transverse foramen of C
- V3 (atlantic or extradural): from C2 to the dura
- V4 (intradural): from the dura to their confluence to form the basilar artery - Identify the boundaries of the intervertebral foramen and its contents. Superior boundary: Pedicle and inferior vertebral notch of vertebra above Inferior boundary: Pedicle and superior vertebral notch of vertebra below Anterior: Posterolateral aspect of adjacent vertebral bodies, intervening disc
**- List in order the structures and spaces pierced in a lumbar puncture. skin, subcutaneous tissue, supraspinal ligament, interspinal ligament, ligamentum flavum, dura mater, the arachnoid mater and into the subarachnoid space.
- List in order the structures and spaces pierced during epidural anesthesia.** 1 - Skin 2 - Facia and SC fat 3 - Surpaspinous ligament 4 - Interspinous ligament 5 - Ligamentum flavum 6 - Epidural space and fat (epidural anesthesia needle stops here) - Describe the differences between the CNS and PNS.
**- Draw the structure of a typical spinal nerve.
- Describe the difference between a dermatome, myotome, and sclerotome.**
- Describe the vascular supply of the deep back and posterior neck.
- Describe the venous anastomoses associated with the vertebral column and discuss their clinical significance.
- Describe the superficial and deep fascia of the back.
