Osteology of the Thoracic Vertebrae

Thoracic Vertebraepage 1 of 6ANAT 51212 Lectures 13, 14, & 15Summer 2013I. IntroductionA. Twelve in number (on average)B. Articulate with the ribsOsteology ofthe Thoracic VertebraeII.Typical thoracic vertebrae (T2-T8)A. Vertebral body1. Heart-shaped in superior view2. Posterior height greater than anterior height3. Body increases in size, T3-T124. Costal demi-facets (two on each side, one superior and one inferior) forarticulation with the head (i.e., capitulum) of the riba. Superior costal demi-facet: articulates with same-numbered ribb. Inferior costal demi-facet: articulates with the next rib down5. Aortic impression (T5-T8): flattening on the left side of the vertebral bodyB. Pedicle1. Orientation: primarily posterior, with only a slight lateral angulation2. Arises from the upper third of the vertebral bodya. Superior vertebral notch/incisure: very shallowb. Inferior vertebral notch/incisure: very deep

Thoracic Vertebraepage 2 of 6C. Intervertebral foramen1. Faces directly laterally, lying within a sagittal plane of the bodya. [Upside-down] pear shape in outline2. Specific spinal nerve exiting the intervertebral foramen is identifiedaccording to the vertebra making up the superior border of theintervertebral foramenD. Lamina1. Broad superior to inferior, plate-like2. Shingling: laminae of adjacent vertebrae overlap each other [like shingleson a roof]E. Vertebral foramen1. Circular in shape2. Smaller than in the cervical or lumbar regionsF. Transverse process1. Large and club-shaped, becoming shorter from T1 to T122. Oriented obliquely posterio-laterally: T2-T4 more laterally oriented, whileT5-T8 more posteriorly oriented3. Transverse tubercle contains the transverse costal facet for articulationwith the articular facet of the tubercle of the same-numbered riba. Transverse costal facet oriented anteriorly and laterallyb. In T5-T8, the transverse costal facets also face slightly superiorly aswellG. Articular processes and facets1. Superior articular facet: oriented backward, upward, and lateral (BUL)

Thoracic Vertebraepage 3 of 62. Inferior articular facet: oriented forward, medially, and downward (FMD orForMeD)3. Pars interarticularis: region between the superior and inferior articularprocesses (T1-T12)4. Distance between articular processesa. In T2-T4, the distance between superior articular processes is greaterthan the distance between the inferior articular processesb. In T5-T8, the distances are approximately equalH. Spinous process1. Long, with a distinct spinous tubercle2. Directed posteriorly and inferiorly, overlapping with the spinous processbelow, a phenomenon termed 'imbrication'a. In T2-T4, the spinous process angle from the horizontal ranges from20 o -40 ob. In T5-T8, the spinous process angle from the horizontal ranges from40 o -60 oIII. Atypical thoracic vertebrae (T1, T9, T10, T11, T12)A. T11. Vertebral bodya. Shapei. Rectangular in superior viewii.Superior epiphyseal rim slightly concave from side-to-sideb. Superior costal facet: usually a full facet, not a demi-facet

2. Pedicle: superior vertebral notch/incisure deeper than in the typicalthoracic vertebraeThoracic Vertebraepage 4 of 63. Transverse process: laterally oriented, more horizontal and anterior than inthe typical thoracic4. Spinous processa. Projecting nearly horizontallyb. Quite longi. Vertebral prominence: surface bulge at the posterior-inferioraspect of the neckB. T91. Vertebral bodya. Superior costal demi-facet may be nearly as large as a full facetb. Inferior costal demi-facet is very small or absent2. Spinous process: becoming more horizontalC. T101. Vertebral bodya. Superior costal facet may be a very large demi-facet or a full facetb. Inferior costal demi-facet is absent2. Transverse process: the transverse costal facet may be absent (the tenthrib may not form a synovial joint with the transverse process)3. Spinous process: becoming more horizontal and shorter, causing a slightdimpling of the skin overlying the spinous tubercle4. Lamina: para-articular processes are more common and more welldeveloped on T10 laminae than on other vertebrae

Thoracic Vertebraepage 5 of 6D. T11 (aka, anticlinal vertebra)1. Vertebral bodya. Shape: reniform (i.e., kidney-shaped) in superior view, as seen in thelumbar vertebraeb. Superior costal facet (i.e., a full facet)c. No inferior costal demi-facet2. Transverse process: short, posteriorly oriented, with no transverse costalfacet3. Spinous process: becoming lumbar-like in shape, with a nearly horizontalinferior borderE. T121. Vertebral bodya. Shape: large and reniform in superior viewb. Superior costal facet: lies partly on the vertebral body and partly on thepediclec. No inferior costal demi-facet2. Transverse process: modified into three tubercles, with no transversecostal faceta. Superior tuberclei. Large, projecting superiorly and posteriorlyii.Homologue of the lumbar mamillary processb. Lateral tuberclei. Projects laterally from the region of the lamina-pedicle junction

Thoracic Vertebraepage 6 of 6ii.Homologue of the lumbar transverse processc. Inferior tuberclei. Small, located below the superior tubercle and posterior to thelateral tubercleii.Homologue of the lumbar accessory process3. Articular process and faceta. Superior articular facet: like that of a typical thoracic vertebrab. Inferior articular facet: lumbar-likei. Faces forward, laterally, and downward (FoLD)ii.Facet surface is distinctly convex4. Spinous process: short (anterior to posterior), broad (superior to inferior),and horizontal, like those of the lumbar vertebrae ('hatchet'-shaped)