The Back

Bony anatomy of the vertebral column or spine General vertebral joints or articulations Specific vertebral articulations Physiological curves of the back Muscles of the back Suboccipital Region

Vertebral column Total vertebrae Movable vertebrae Fused vertebrae Sacrum Coccyx Total: 33 Movable 24 Fused: 9

Numbers of vertebrae Cervical: Thoracic: Lumbar: Sacral: Coccygeal:

Variations in numbers of vertebrae Number of cervical vertebrae is very constant in all mammals, including man Variations in numbers of thoracic, lumbar and sacral vertebrae occur in about 5% of otherwise average people

Common variations Sacralization of the 5th lumbar vertebrae The 5th lumbar vertebrae is partly or completely incorporated into the sacrum X-Ray: only 4 lumbar vertebrae L5/S1 joint is strong L4/L5 level can degenerate – often producing painful symptoms

Lumbarization of the 1st sacral vertebrae 1st sacral vertebrae is separated from the sacrum, and incorporated into the lumbar spine In general, the relationship between these variations and back symptoms in the clinic is NOT clear

Intervertebral discs Resilient fibrocartilaginous structures Type of joint – Secondary cartilaginous joint Anterior articulation Connect presacral vertebrae (C2 to S1) No disc between: Occiput and C1 C1 and C2 No discs in sacrum or coccyx

Role of discs Strongest connection between vertebrae Important role in shock absorption

Posterior connection between vertebrae For presacral vertebrae Zygapophyseal joints Gliding/sliding/planar type synovial joints Zygo: yoke -apo-: upon -physeal: growth

Ligaments of the spine There are ligaments that strengthen the connections between the vertebrae Some extend all or most of the length of the vertebral column Some are specific to certain joints between select vertebrae

Ligaments that extend the length of the vertebral column Anterior longitudinal ligament Posterior longitudinal ligament Ligamentum flavum Interspinous ligaments Ligamentum nuchae and supraspinous ligament Intertransverse ligaments

Anterior Longitudinal Ligament Anterior 1/3 to ½ of anterior surface of body of vertebrae Runs length of vertebral column from: Sacrum C1 (atlas) anterior tubercle Occipital bone of skull, anterior to the foramen magnum

Broader and stronger than posterior longitudinal ligament Function Firmly attached to the intervertebral discs and the periosteum of the vertebral bodies Broader and stronger than posterior longitudinal ligament Function Maintain stability of joints between vertebral bodies Help prevent what movement of vertebral column?

Posterior Longitudinal Ligament Wraps around 1/3 to ½ of posterior surface of vertebral body Runs along posterior aspect of vertebral bodies within the vertebral canal Thicker than ALL, but narrower and weaker

Attachment of posterior longitudinal ligament sacrum to C2 C1 Superiorly is continuous with tectorial membrane, which attaches to occipital bone on internal part of foramen magnum

Function Help prevent posterior protrusion of the nucleus pulposus of the intervertebral discs What movement of the vertebral column will this ligament limit?

Ligamentum Flavum Yellow ligament Location of ligament Function Yellow = Elastin Location = adjacent lamina Functions maintain curvature of spine return spine after flexion

Interspinous ligament Location What is the ligament like? Between spinous processes Thin and membranous

Ligamentum nuchae and the supraspinous ligament Attachments Strength Location Ligamentum nuchae Superior extension of supraspinous ligament Supraspinous Tips of spinous processes Strong From c7 to sacrum Ligamentum nuchae From Inion to c7

Intertransverse ligaments Location Description Lumbar region Location – between transverse processes Cervical – few scattered fibers Thoracic – cords with deep muscles of the back Lumbar – thin and membranous

Anatomy of the vertebrae Body - anterior Vertebral Arch - posterior Pedicle Lamina 7 Processes AKA Neural arch

The body of the vertebrae Anterior part of vertebrae AKA centrum (anatomical center) Primary function of the body is to bear weight

Vertebral Arch On posterior part of the vertebrae Function: Protect the spinal cord from injury Formed from: 2 pedicles (little feet) – attach to body 2 lamina (thin plates) – attach to pedicles. Attach to each other at posterior

Vertebral Foramen Vertebral arch encloses the vertebral foramen Vertebral canal: formed by the successive vertebral foramen Contents of vertebral canal Spinal cord Meninges Nerve roots Blood vessels

Pedicles Anterior attachment Posterior attachment Superior vertebral notch Inferior vertebral notch Intervertebral foramen

How are neural structures located within the vertebral canal and intervertebral foramen Dorsal and ventral roots Dorsal root ganglia Spinal nerve

Processes on vertebral arch 3 lever-like 1 spinous process 2 transverse processes 4 articular processes 2 superior articular processes and facets 2 inferior articular processes and facets

Processes Serve as attachment sites for muscles and ligaments to facilitate and help movement of the vertebrae Spinous processes Project : From union of: Transverse processes Project:

Articular processes Superior and inferior articular processes arise from the junction of the lamina and pedicle The superior articular process of one vertebrae articulates with the inferior articular process of the above vertebrae

Processes help prevent forward moving of an upper vertebrae on a lower one, especially in thoracic and lumbar regions The articular processes allow flexion and extension, as well as varying degrees of lateral bending and rotation in the different regions of the spine

How do we tell the vertebrae apart from the different levels of the spinal cord Size of body Size and shape of processes Special features

Cervical vertebrae Main distinguishing characteristics Transverse foramen Bifid spinous processes Vertebral foramen - triangular

Transverse Foramen Oval foramen Where are they on the vertebrae? What travels through them?

Vertebral artery Comes off subclavian artery Travels through the transverse foramen of C6 through C1 The artery then bends backward above C1, pierces the meninges, and enters the skull through the foramen magnum Supplies rostral spinal cord, brainstem, cerebellum, and posterior cerebral cortex

Transverse Foramen In C7, smaller and occasionally absent The vertebral artery DOES NOT travel through the transverse foramen of C7 If the transverse foramen is present, small accessory vertebral arteries will travel through it

Bifid Spinous Processes From C2 to C6, the spinous process is often split at the end into a fork-like structure

Atlas First Cervical Vertebrae NO spinous process NO body Supports the skull (Atlas in mythology) Superior articular facets Kidney-shaped Concave Articulate with occipital condyles of the skull

Axis Second cervical vertebrae Superior articular facets Atlas rotates on these facets Dens (odontoid process)

Dens Location: Anterior Articulates with facets on anterior arch of atlas Held in place Transverse ligament Prevents horizontal displacement of atlas Skull and atlas rotate on axis as a unit

7th Cervical vertebrae Very long spinous process Recognizable through skin Neck flexion AKA vertebrae prominens

Review of characteristics of cervical vertebrae Transverse foramen Bifid spinous processes C1 – unique C2 – unique C7 – long spinous process

Thoracic vertebrae Long, slender spinous processes which face downward, especially in the midthoracic region Middle thoracic vertebrae have circular vertebral foramen All have facets on vertebral bodies for articulation with the head of a rib Upper 10 have facets on transverse processes to articulate with tubercle of a rib

First thoracic vertebrae Similar to cervical in that the spinous process is almost horizontal How would you then tell C7 from T1

Thoracic vertebral superior articular processes Face posterior and slightly upward Would this restrict any movements? Lateral bending Flexion/Extension Rotation Anterior/Posterior shift

Summary of thoracic vertebrae Spinous processes that face down Rib facets All have on sides of body Upper 10 have on both body and transverse processes Round vertebral foramen or canal Heart-shaped body Superior articular facets that face posterior and slightly upward

Lumbar vertebrae Spinous processes which are squared off Large bodies compared to cervical and thoracic

Vertebral canal is more oval-shaped Where does spinal cord end, and cauda equina begin? L1/L2 canal more rounded than L5 Articular facets face each other in sagittal plane How would this affect movement?

Sacrum 5 fused sacral vertebrae in the adult Many of the vertebral structures exist, but they are fused together

Foramina 4 pairs on both the ventral and dorsal surfaces of the sacrum For exit of the anterior and posterior primary divisions of the sacral nerves Note that the ventral foramina are larger than the dorsal sacral foramina 4 transverse lines on the pelvic (ventral) surface that indicate where fusion of the vertebrae occurred after the 20th year

Superior articulating processes of the sacrum Base of the sacrum Superior surface of 1st sacral vertebrae Superior articulating processes of the sacrum Articulate with inferior articulating facets of the L5 Sacral promontory Projecting anterior edge of the body of the first sacral vertebrae

Sacral hiatus The sacrum Inverted V-shaped structure On dorsal surface Formed on each side by the sacral cornua (horns) The sacrum Supports the vertebral column Forms the posterior part of the pelvis

Articulates with L5 at an angle Sacrum is tilted Articulates with L5 at an angle Lumbosacral angle

Coccyx Degenerated remnant of embryonic tail 4 rudimentary vertebrae Lower three vertebrae are just a body 1st cervical

Ribs Usually 12 on each side of the thorax Each rib has a head, neck, tubercle and shaft Head 2 facets Vertebrae of same number Vertebrae above Neck – between head and tubercle

Ribs 1, 3 and 8

Tubercle Posterior surface of rib Facet: which ribs? Articulates with On which ribs: 1 – 10 Articulates with transverse process of same numbered thoracic vertebrae

Shaft Superior border Inferior border Angle of Rib

True ribs False Ribs Floating Ribs True 1 – 7 – attach directly to sternum through their own cartilage False 8-12 – attach to sternum through cartilage of superior rib or not at all Floating – 11 and 12 – do not attach to sternum at all