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Applied anatomy and examination of the Back Week 27 LOs Understand the concepts & associated principles, functional & clinical applications of: 4. The significance of the valveless “internal vertebral venous plexus”. Spinal veins form venous plexuses both inside and outside the vertebral column, the internal venous plexus and the external venous plexus the internal venous plexus consists of a dense network of thin-walled, valveless veins which surround the dura mater veins from the vertebral body (basivertebral veins) drain primarily into the internal vertebral plexus flow may occur in either direction communication with venous plexuses around pelvic viscera provides a pathway for tumour spread (e.g. from the prostate gland) 5. The vulnerability of the arterial supply of the spinal cord (noting the sites of poor anastomoses). three longitudinal arteries which descend from level of foramen magnum: anterior spinal artery – (x1) from vertebral arteries posterior spinal arteries – (x2) paired, from vertebral arteries supplemented at variable levels by anastomoses with radicular arteries spinal arteries are branches of the: – vertebral and ascending cervical arteries in the neck – posterior intercostals arteries in the thoracic region – subcostal and lumbar arteries in the abdomen – iliolumbar and lateral and medial sacral arteries in the pelvis spinal arteries enter the IV foramina and divide mostly into terminal radicular arteries distributed to the dorsal and ventral roots of the spinal nerves and their coverings these are important particularly in lower thoracic region where anterior spinal artery almost non-existent some radicular arteries continue as irregularly spaced medullary segmental arteries that anastamose with arteries of the spinal cord 6. The sites, mechanism and effects of lumbar intervertebral disc “prolapse”. Herniation/protrusion of the nucleus pulposus through the annulus fibrosus is a wellrecognised cause of lower back pain Sites: 95% occur at the L4/L5 or L5/S1 levels usually occur posteriorly where annulus fibrosis is relatively thin and poorly supported by either the posterior or anterior longitudinal ligaments in young people the IV discs are turgid and consist of approximately 90% water Mechanism: violent hyperflexion of the vertebral column may result in IV disc rupture and fracture of adjacent vertebrae flexion of the vertebral column causes compression anteriorly and stretching or tension posteriorly, pushing the nucleus pulposus posteriorly towards the thinnest part of the annulus fibrosis if degeneration of the posterior longitudinal ligament and wearing of the annulus fibrosis has occurred, the nucleus pulposus may herniate into the vertebral canal and compress the spinal cord or the nerve roots of the chorda equina Effects: posterolateral herniated disc is more like to be symptomatic due to proximity of spinal nerve roots localized back pain is caused by pressure on the longitudinal ligaments and periphery of the annulus fibrosis and from local irritation resulting from local inflammation resulting from chemical irritation by substances from the ruptured nucleus pulposus chronic pain from the spinal nerve roots being compressed is referred to the dermatome supplied by that nerve What structures are endangered by an intervertebral disc protrusion? • Dorsal & ventral roots • Dorsal root ganglion • Spinal nerves • Feeder (radicular) vessels