Axial Skeleton: Vertebral Column HESC310 4/23/2017 Axial Skeleton: Vertebral Column Slides by Vince Austin; figures from Marieb & Hoehn 7th & 8th eds.; modifications and some slides by W. Rose Portions copyright Pearson Education Axial Skeleton

Vertebral Column 26 irregular bones (vertebrae) connected to form a flexible curved structure Cervical vertebrae – 7 bones of neck Thoracic vertebrae – 12 bones of torso Lumbar vertebrae – 5 bones of lower back Sacrum – bone inferior to the lumbar vertebrae that articulates with the hip bones (fusion of 5, starts ~> puberty, done mid-20s)

Vertebral Column Spinal nerves C1-C7 exit above vertebrae C1-C7 Lordotic Spinal nerve C8 exits above T1 Kyphotic Spinal nerves T1-T12, L1-L5, S1-S5 exit below vertebrae T1-T12, L1-L5, S1-S5 Lordotic Kyphotic Figure 7.13

Vertebral Column: Curvatures Kyphosis = posteriorly convex curvature. Thoracic and sacral normally kyphotic (but not too much). Lordosis = posteriorly concave curvature. Cervical and lumbar normally lordotic (but not too much). Abnormal spinal curvatures Scoliosis (lateral curve) Excessive kyphosis (hunchback) Excessive lordosis (swayback) What happens in pregnancy?

Vertebral Column: Ligaments Anterior and posterior longitudinal ligaments – continuous bands down the front and back of the spine from the neck to the sacrum Short ligaments connect adjoining vertebrae together

Vertebral Column: Ligaments

Vertebral Column: Intervertebral Discs Cushion-like pad composed of two parts Nucleus pulposus – inner gelatinous nucleus that gives the disc its elasticity and compressibility Annulus fibrosus – surrounds the nucleus pulposus with a collar composed of collagen and fibrocartilage

Vertebral Column: Intervertebral Discs

General Structure of Vertebrae Body or centrum – disc-shaped, weight-bearing region Vertebral arch – composed of pedicles and laminae that, along with the centrum, enclose the vertebral foramen Vertebral foramina – make up the vertebral canal through which the spinal cord passes

General Structure of Vertebrae Spinous processes project posteriorly, and transverse processes project laterally Superior and inferior articular processes – protrude superiorly and inferiorly from the pedicle-lamina junctions Intervertebral foramina – lateral openings formed from notched areas on the superior and inferior borders of adjacent pedicles

General Structure of Vertebrae transverse costal facet for tubercle of rib part of the facet joint superior demifacet; must be a T heart-shaped in Ts, oval in Ls

Cervical Vertebrae Seven vertebrae (C1-C7): smallest, lightest vertebrae C3-C7: Distinguished by oval bodies, short spinous processes, large, triangular vertebral foramina. Articular facets (sup & inf) form joints with vetrebrae above & below. Each transverse process contains a transverse foramen. (Only cervical have transverse foramina.)

Cervical Vertebrae Table 7.2.2

Cervical Vertebrae: Atlas (C1) No body, no spinous process Anterior and posterior arches, and two lateral masses Superior surfaces of lateral masses articulate with occipital condyles

Cervical Vertebrae: The Atlas (C1) Figure 7.16a, b

Cervical Vertebrae: Axis (C2) Body, spine, and vertebral arches, like other cervical vertebrae Unique feature: dens, or odontoid process, projects superiorly from body, cradled in the anterior arch of the atlas The dens is a pivot for the rotation of the atlas The “missing body” of the atlas?

Cervical Vertebrae: The Axis (C2) Figure 7.16c

Cervical Vertebrae: Atlas, Axis (C1, C2) Figure 7.17a

Regional Characteristics of Vertebrae Table 7.2.1

Regional Characteristics of Vertebrae Table 7.2.2

Thoracic Vertebrae Twelve vertebrae (T1-T12), each of which articulates with one or two of the twelve ribs Major markings include: Superior, inferior articular facets (vertebrae above, below) Sup, inf costal facets (“demifacets”) on heart-shaped body (rib heads) (T10, T11, T12 have single costal facets) Circular vertebral foramen Transverse processes with transverse costal facets (rib tubercles) (not T11, T12) Long spinous process Location, orientation of articular facets prevents sagittal plane flexion and extension, but allows rotation and limited lateral flexion, of thoracic spine

Thoracic Vertebrae Figure 7.17b

Lumbar Vertebrae The five lumbar vertebrae (L1-L5) are located in the small of the back and have an enhanced weight-bearing function They have short, thick pedicles and laminae, flat hatchet-shaped spinous processes, and a triangular-shaped vertebral foramen Orientation of articular facets locks the lumbar vertebrae together to provide stability

Lumbar Vertebrae Figure 7.17c

Sacrum Sacrum Consists of five fused vertebrae (S1-S5), which shape the posterior wall of the pelvis It articulates with L5 superiorly, and with the auricular surfaces of the hip bones Major markings include the sacral promontory, transverse lines, alae, dorsal sacral foramina, sacral canal, and sacral hiatus

Coccyx Coccyx (Tailbone) The coccyx is made up of four (in some cases three to five) fused vertebrae that articulate superiorly with the sacrum

Sacrum and Coccyx: Anterior View Figure 7.18a

Sacrum and Coccyx: Posterior View Figure 7.18b