Exercise Science 6

Discuss the anatomy of bones, joints, and muscles of the spine.
Identify the origin and insertion points of spinal muscles.
Analyze the direction of pull and joint actions of various muscles involved in spinal motion.

General Structure:
- The spinal column consists of a complex arrangement of irregular bones known as vertebrae, which are stacked to form the vertebral column.
Components of the Spinal Column:
- Total Number of Vertebrae: 24 individual vertebrae
- 7 cervical (neck region)
- 12 thoracic (mid-back region)
- 5 lumbar (lower back region)
- Additional structures:
- Sacrum: Large bone situated below the lumbar vertebrae.
- Coccyx: Tailbone formed by 3-5 fused vertebrae.
Functions of the Spine:
- Links upper and lower extremities.
- Protects the spinal cord.
- Enables trunk motion in three planes (sagittal, frontal, transverse).
- Protects internal organs located in the chest region.

C1 Vertebra (Atlas):
- Articulates with the occipital bone of the skull.
L5 Vertebra:
- Articulates with the sacrum.
Variations in Size:
- Vertebrae increase in size from cervical to lumbar regions.
Vertical Elements of a Vertebra:
- Each vertebra consists of anterior and posterior components:
- Anterior Components:
  - Vertebral Body:
  - Shape: Oval with flat superior and inferior surfaces.
  - Function: Articulates with adjacent vertebral bodies.
- Posterior Components:
  - Pedicles and Laminae:
  - These structures join anteriorly at the body and posteriorly at the spinous process to form the vertebral foramen (canal).
  - Vertebral Foramen:
  - Function: Provides a space for the spinal cord.
  - Posterior Features:
  - Facets: Articulations located on each side, top, and bottom for interaction with adjacent vertebrae.
  - Spinous and Transverse Processes: Bony protuberances extending from the vertebra, serving as attachment points for muscles.

Rib Attachment:
- Ribs attach to each of the 12 thoracic vertebrae to form the thoracic cage.
Types of Ribs:
- True Ribs (1-7): Attach directly to the sternum.
- False Ribs (8-12):
- 3 pairs attach indirectly to the sternum via costal cartilage.
- 2 pairs are floating ribs that do not attach to the sternum.

Location: Positioned at the lower spine, inferior to the 5th lumbar vertebra.
Sacrum: Large triangular bone formed from fused vertebrae.
Coccyx: A small bone at the base of the vertebral column formed from 3 to 5 fused vertebrae.

Sagittal Plane: The spine exhibits four distinct curves:
- Lordosis: Anterior convexity of the curve. Present in cervical and lumbar regions.
- Kyphosis: Posterior convexity of the curve. Present in thoracic and sacral regions.

Types of Ligaments:
- Anterior and Posterior Longitudinal Ligaments:
- Function: Attach to vertebral bodies, spanning from upper cervical to lower lumbar regions.
- Ligamentum Flavum:
- Connection between posterior arches forms the posterior border of the vertebral canal. Extends from upper cervical to lower lumbar.
- Interspinous and Supraspinous Ligaments:
- Function: Attach adjacent posterior arch structures, also spanning from upper cervical to lower lumbar regions.

General Characteristics:
- Function: Provide load bearing, shock absorption, and stability.
- Located between vertebral bodies, constituting 20-33% of the height of the vertebral column.
- Exceptions: No intervertebral discs exist between C1 and C2 (atlas and axis).
Components of Intervertebral Discs:
- Nucleus Pulposus:
- Central portion of the disc; gel-like and more liquid compared to the annulus fibrosis.
- Dehydrates with age, contributing to a reduction in body height.
- Annulus Fibrosis:
- Located at the periphery; more rigid and contains a greater amount of collagen.
- Fiber arrangements help resist tensile and compressive forces but make it susceptible to tearing during twisting and bending under load.
- Vertebral Endplates:
- Thin fibrocartilage layers covering the inferior and superior aspects of the vertebral body, anchoring the disc to the vertebrae.

General Capabilities:
- The spine can move in all planes of motion.
- Cervical Spine Movement:
- Flexion, extension, lateral flexion, and rotation.
- Thoracic Spine Movement:
- Moderate flexion, slight extension, and moderate lateral flexion/rotation.
- Lumbar Spine Movement:
- Flexion, extension, lateral flexion, and slight rotation.

Cervical Muscles:
- Anterior:
- Primary Muscles: Sternocleidomastoid, Scalenes, Longus Capitis, Longus Colli.
- Actions:
  - Unilateral Contraction: Lateral flexion and rotation of the head and neck.
  - Bilateral Contraction: Flexes head and neck.
- Posterior:
- Primary Muscles: Suboccipital, Splenius, Erector Spinae.
- Actions:
  - Unilateral Contraction: Lateral bend and rotate head and neck.
  - Bilateral Contraction: Extends head and neck.
- Lateral:
- Primary Muscles: Levator Scapulae, Upper Trapezius.
- Actions:
  - Unilateral Contraction: Lateral bend/rotation of head and neck.
  - Bilateral Contraction: Extends head and neck.
Lumbar Muscles:
- Anterior:
- Primary Muscles: Rectus Abdominus, Internal/External Obliques, Transverse Abdominus.
- Actions:
  - Unilateral Contraction: Rotates the trunk.
  - Bilateral Contraction: Flexes the trunk, stabilizes the lumbar spine.
- Posterior:
- Primary Muscles: Erector Spinae, Multifidus.
- Actions:
  - Unilateral Contraction: Laterally flexes and rotates trunk.
  - Bilateral Contraction: Extends trunk.
- Lateral:
- Primary Muscles: Quadratus Lumborum.
- Actions:
  - Unilateral Contraction: Laterally flexes the trunk.
  - Bilateral Contraction: Stabilizes the trunk.
- Psoas: Responsible for flexing the trunk.