Lumbar Intervertebral Discs

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Lumbar Intervertebral Discs
Primary Type	Cartilaginous Joint
Secondary Type	Symphysis
Bones
Ligaments
Muscles
Innervation
Vasculature
ROM
Volume
Conditions

Structure Overview

Structures	Features	Microstructure
Anulus fibrosus	- 10-20 sheets of collagen fibres (lamellae) - Lamellae are thicker anteriorly, laterally - Around half of lamellae extend the entire circumference - collagen fibres in each lamella are oriented in same direction, 65-70° from the vertical - The direction alternates with each lamella - The disc is richly innervated in its outer 1/3	- 60-70% water - Collagen>>PG - PG mostly aggregated - Collagen mainly Type I, some type II throughout anulus - type I mainly outer anulus - some elastic fibres - contains Chondrocytes and fibroblasts
Nucleus pulposis	- Healthy disc: semi fluid mass of mucoid material - Can be deformed but not compressed - Can transmit forces in all directions under pressure.	-70-90% water - PG>>Collagen - PG freely dispersed PG units - Collagen mainly type II - Contains chondrocytes
Vertebral end plate	- 1 mm thick layer of cartilage - consists of hyaline and fibrocartilage - is bounded by the ring apophysis - Collagen fibres of the inner anulus fibrosus enter the end plate and swing centrally within it - Diffusion of nutrients through the end plates is important for the nutrition of the end plate and intervertebral disc
Vertebral body	- Trabecular bone in VB consists of vertical and transverse trabeculae - Allowing VB to resist vertical and horizontal load.
Spine	1.Vertebral body: (have horizontal and vertical oriented trabeculae to distribute load) 2. Posterior elements: - Pedicle - transverse process - Facet joint: IAP, SAP (articular process above and below connect via facet joints. Synovial joint) - Lamina: - Spinous process - Canal (vertebral foramen): - neuroforamen: each nerve root exits - Mamillary process - Accessory process 3.The disc sits between the vertebral bodies -annulus fibrosis - nucleus pulposis. - end plate.	Function of LS individual components Vertebral bodies: resist axial compressive forces via inner trabeculae. Facet joint: can be flat, C shaped, or J shaped, resist forward translation and rotation of L vertebra. Disc: NP evenly distributes compressive force, AF resist twisting plus translation in each direction. Vertebral endplate allow nutrient to transmit through the endplate.

Innervation

Posterior Disc: sinuvertebral nerve from ventral ramus

Anterolateral disc: Grey ramus communicans of the lumbar sympathetic trunk

Anterior disc: sympathetic branches from the sympathetic trunk or ganglion.

Sinuvertebral nerve: also known as recurrent meningeal nerves or recurrent nerves of Luschka. Innervate the meninges, ligaments, and periosteum of the spinal canal and the anulus fibrosus of the intervertebral disk and carry sensory information, including pain, from those structures.