The Vertebral Column: Functions and Composition

The Vertebral Column

• Functions: SIRENA (Supports the head, Important attachment for muscles, Rib attachment, Encloses and protects the spinal cord, Nagprovide ng flexibility and mobility of the trunk, Ability to transmit weight of head and body to the LE)
• Composition: 33 vertebrae in pediatrics, 26 vertebrae in adults (Cervical: 7, Thoracic: 12, Lumbar: 5, Sacrum: 5 fused in adulthood, Coccyx: 4 fused in adulthood)

Typical Vertebra

• Characteristics:
  • Cervical (C3-C6): Small vertebral body, Short and bifid spinous process, Transverse foramen (passes the vertebral artery, vertebral vein, and sympathetic nerves)
  • Thoracic (T5-T8): Medium vertebral body, Long and inclined spinous process, Conical transverse process
  • Lumbar (L1-L4): Largest vertebral body, Short, flat, and quadrilateral spinous process, Triangular vertebral foramen

Atypical Vertebrae

• C1 (Atlas): No body, no spinous process, Costal facets located on the superior edge of vertebral body
• C2 (Axis/Epistropheus): Odontoid process/dens, Large bifid spinous process, Short transverse process
• C7: Vertebral prominence, Long non-bifid spinous process, Small or no transverse foramen
• T1: Spinous process is horizontal, Costal facets located on the superior edge of vertebral body
• T9: (+) tubercles on transverse process
• T10-T12: (+) tubercles, costal facets are located on the lateral aspect of the vertebral body
• Sacrum: Consists of five rudimentary vertebrae fused together to form a wedge-shaped bone
• Coccyx: Consists of four vertebrae fused together to form a single, small triangular bone that articulates at its base with the lower end of the sacrum

Joints

• Atlanto-Occipital Joint: Condylar joint, 50% flexion-extension
• Atlanto-Axial Joint: Pivot/trochoid joint, 50% rotation

Intervertebral Discs

• Characteristics:
  • Nucleus Pulposus: Gel-like mass in center of disc, 80-90% water, 15-20% collagen, 25% of vertebral column height
  • Annulus Fibrosus: 50-60% collagen, Lamellae: protein that crisscross by 30°, Sharpey's fibers (results to herniated disc if damaged)

Ligaments

• Intersegmental Ligaments: Global Stability
  • Anterior Longitudinal Ligament: Attached anterior of vertebral body, prevents hyperextension
  • Posterior Longitudinal Ligament: Attached posterior of vertebral body inside spinal canal, prevents flexion
  • Supraspinous Ligament: Connects the tips of spinous process from C7-sacrum
• Intrasegmental Ligaments: Segmental Stability
  • Ligamentum Flavum: Connects adjacent lamina
  • Ligamentum Nuchae: Connects the tip of spinous process from C7-occiput
  • Interspinous Ligament: Connects adjacent spinous process
  • Intertransverse Ligament: Connects adjacent transverse process

Muscles of the Back

• Superficial Layer:
  • Trapezius: Upward rotation of scapula, shawl muscle
  • Levator Scapulae: Elevates the scapula, downward rotation of scapula
  • Latissimus Dorsi: Broadest/widest muscle, also known as crutch-walking muscle
  • Rhomboids major/minor: Retract shoulder, downward rotator
• Intermediate Layer:
  • Serratus Posterior
• Deep Layer:
  • Splenius: Bandage muscle
  • Erector Spinae: Longitudinal muscle, chief erector of spine
  • Transversospinalis/Oblique Muscles (SaMuRai)
  • Deepest Muscles: Interspinalis, Intertransversarii

Blood Supply of the Back

• Arteries:
  • Cervical: Branches arise from the occipital artery, vertebral artery, and deep cervical artery
  • Thoracic: Branches arise from the posterior intercostal arteries
  • Lumbar: Branches arise from the subcostal and lumbar arteries
  • Sacral: Branches arise from the iliolumbar and lateral sacral arteries
• Veins:
  • External vertebral venous plexus: Lies external and surrounds the vertebral column
  • Internal vertebral venous plexus: Lies within the vertebral canal but outside the dura mater of the spinal cord

Lymph Drainage of the Back

• Deep lymph vessels follow the veins and drain into the deep cervical, posterior mediastinal, lateral aortic, and sacral nodes
• Superficial lymph vessels drain into the cervical nodes, axillary nodes, and superficial inguinal nodes

Nerve Supply of the Back

• The skin and muscles of the back are supplied in a segmental manner by the posterior rami of the 31 pairs of spinal nerves
• Posterior rami of certain spinal nerves supply the deep muscles of the back and do not supply the skin

Spinal Cord

• Cylindrical mass of neural tissue, occupying the upper 2/3 of the vertebral canal
• Starts at the foramen magnum and ends at L1-L2 vertebrae
• External Structures:
  • Conus Medullaris: Conical inferior end
  • Filum Terminale: Filament extending from the conus and attaches to the 1st segment of the coccyx
  • Cauda Equina: Horsetail composed of rootlets of lumbosacral plexus

Learn about the functions and composition of the vertebral column, including its role in supporting the head, enclosing the spinal cord, and providing flexibility and mobility to the trunk. Understand the different regions of the vertebral column, including the cervical, thoracic, lumbar, sacrum, and coccyx sections.