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Questions and Answers
What is the orientation of the spinous processes in the thoracic spine?
Which joint is formed by the superior articular facet of T7 and the inferior articular facet of T6?
What is a unique structural characteristic of the lumbar spine compared to the thoracic spine?
The term 'zygapophyseal joint' refers to what specific feature?
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What is the function of the mammillary process in the lumbar spine?
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What is the primary function of the nucleus pulposus in the intervertebral disc?
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Which structural feature of the lumbar spine contributes to the articulation between L1 and L2?
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What primarily composes the annulus fibrosis?
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What commonly occurs when the nucleus pulposus becomes dehydrated?
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What is the primary composition of the vertebral endplate?
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How do collagen fibers in the annulus fibrosis provide structural integrity?
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What role do the vertebral endplates play in relation to the nucleus pulposus?
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What consequence might arise from osteophyte formation due to bone on bone contact?
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Why does the intervertebral disc not slide off the vertebral body during movement?
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What happens to the annulus fibrosis under high compressive loads?
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Study Notes
Thoracic Spine Osteology
- Twelve thoracic segments.
- Spinous processes oriented inferiorly, most prominent at T6-T8.
- Facet joints vertically projected; superior articular facet oriented posteriorly, inferior articular facet oriented anteriorly.
- Apophyseal (or zygapophyseal) joints formed by articulation of superior and inferior articular facets.
Lumbar Spine Osteology
- Five lumbar segments.
- Vertebral bodies larger than those in thoracic or cervical spine to support greater weight.
- Spinous processes project posteriorly without inferior orientation.
- Mammillary process serves as attachment point for multifidi muscles.
- Superior articular facets slightly concave; inferior articular facets slightly convex.
Interbody Joints
- Composed of two vertebral bodies, vertebral endplates, and an intervertebral disc.
- Intervertebral disc includes a nucleus pulposus and annulus fibrosis.
- Nucleus pulposus: gel-like structure of water, type I collagen, and elastin; functions in shock absorption.
- Annulus fibrosis: 15-25 concentric layers of collagen fibers; provides stiffness and support to nucleus pulposus; collagen fibers oriented at approximately 65 degrees.
- Dehydrated discs lose shock absorption, leading to bone-on-bone contact, osteophyte formation, nerve impingement, and radicular symptoms.
Vertebral Endplates
- Connect intervertebral disc to vertebral body, preventing disc slippage.
- Composed of fibrocartilage (disc-facing side) and osseous cartilage (vertebral body-facing side).
- Fibrocartilage binds strongly with annulus fibrosis; osseous cartilage binds with vertebral body, providing weaker adhesion.
- Supply nutrients (glucose, oxygen) to avascular nucleus pulposus and annulus fibrosis.
Pressure Distribution in Intervertebral Discs
- Eighty percent of body weight is transmitted through lumbar vertebrae to interbody joints; remaining 20% distributed to posterior spinal elements.
- Compressive loads push vertebral endplates inward, deforming the nucleus pulposus radially outward against the annulus fibrosis.
- Pressure is uniformly distributed to adjacent vertebrae.
- Activities like bending increase disc pressure; reclining reduces it.
- Poor posture increases disc pressure compared to good posture.
- Lifting improperly significantly increases disc pressure compared to lifting with knees.
Diurnal Variation in Disc Height
- Disc height varies throughout the day; individuals are taller in the morning due to hydration of the nucleus pulposus.
- This variation is more pronounced in younger adults due to age-related dehydration of the nucleus pulposus.
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Description
This quiz covers the anatomical features and functional aspects of the thoracic and lumbar spine. It includes details about vertebral segments, joint articulations, and interbody joints. Test your knowledge on the structure and significance of these spinal regions.
