Typical vertebra: General structural plan
Any vertebra (vertebra) is built according to a unified scheme, most clearly expressed in thoracic vertebrae. It features seven mandatory elements, knowledge of which ensures understanding of all other parts of the vertebral column.
- Vertebral body (corpus vertebrae) with superior and inferior intervertebral surfaces and marginal circular epiphysis (anulus epiphysialis).
- Vertebral arch (arcus vertebrae), consisting of a pedicle (pediculus arcus vertebrae) and a lamina (lamina arcus vertebrae).
- Vertebral foramen (foramen vertebrale), which together form the vertebral canal.
- Three types of processes: spinous (processus spinosus), paired transverse (processus transversus), and paired articular processes (processus articulares superiores et inferiores).
- Superior and inferior vertebral notches (incisurae vertebrales superior et inferior), forming the intervertebral foramen for the spinal nerve.
Thoracic vertebrae and their features
The main characteristic of thoracic vertebrae (vertebrae thoracicae) is the presence of articular facets for the ribs. Costal facets (foveae costales) are located on the body: they can be complete or represented by demifacets — superior and inferior, joining when adjacent vertebrae articulate. On the transverse process, there is a costal facet of the transverse process (fovea costalis processus transversi), which articulates with the tubercle of the rib. Thus, the rib connects to the vertebral column at two points: the head connects to the vertebral bodies, and the tubercle connects to the transverse process.
Cervical vertebrae, atlas, and axis
Cervical vertebrae (vertebrae cervicales) are distinguished by the transverse foramen (foramen transversarium), formed by the fusion of the rudimentary rib with the transverse process. The vertebral artery passes through this foramen (except for the VII vertebra). On the transverse process, the groove for the spinal nerve, anterior and posterior tubercles are distinguished. In the VI vertebra, the anterior tubercle is particularly large — this is the carotid tubercle (tuberculum caroticum). The spinous processes of cervical vertebrae are split (bifid), and uncinate processes (processus uncinatus) are present on the bodies.
Atlas (atlas, CI) lacks a body: it has fused with the second vertebra to form the dens. The atlas consists of anterior and posterior arches with corresponding tubercles and lateral masses with superior (for the occipital condyles) and inferior articular surfaces. The anterior arch features the facet for dens (fovea dentis), and the upper surface of the posterior arch features the groove for the vertebral artery (sulcus arteriae vertebralis).
Axis (axis, CII) bears the dens (dens) with an apex, an anterior articular surface for the facet of the atlas, and a posterior one for the transverse ligament of the atlas. Vertebra prominens (CVII) is distinguished by a long, un-split spinous process serving as a clinical landmark.
Lumbar vertebrae, sacrum, and coccyx
Lumbar vertebrae (vertebrae lumbales) are massive; their transverse processes are actually costal processes (processus costalis). The superior articular processes feature the mammillary (processus mamillaris) and accessory processes (processus accessorius) — attachment sites for deep back muscles.
Sacrum (os sacrum) is the result of the fusion of five vertebrae. A base with a promontory (promontorium), wings, and superior articular processes, as well as an apex, are distinguished. Transverse lines and anterior sacral foramina are visible on the pelvic surface, while three crests are visible on the dorsal surface: median, intermediate, and lateral sacral crests, as well as posterior sacral foramina. Auricular surfaces (facies auricularis) and the sacral tuberosity (tuberositas ossis sacri) are located laterally. Inside runs the sacral canal (canalis sacralis), which opens via the sacral hiatus (hiatus sacralis), bounded by the sacral cornua (cornua sacralia). The coccyx (os coccygis) is a rudimentary tail region, possessing coccygeal cornua and reduced transverse processes.
Sternum and ribs
Sternum (sternum) consists of the manubrium, body (corpus), and xiphoid process (processus xiphoideus). The jugular and paired clavicular notches are distinguished on the manubrium, and costal notches are located along the margins of the body. The sternal angle (angulus sterni) is formed between the manubrium and body — a landmark for the second rib.
A distinction is made between true ribs (I–VII), false ribs (VIII–X), and floating ribs (XI–XII, costae fluctuantes). The rib (costa) features a head (caput costae) with a crest (crista capitis costae), a neck (collum), a tubercle (tuberculum costae), and a body with the angle of the rib (angulus costae). The lower margin features the costal groove (sulcus costae) for the intercostal vessels and nerve—which is why puncture is performed along the upper margin of the underlying rib. The 1st rib lacks a costal groove, but has the tubercle for anterior scalene muscle (tuberculum musculi scaleni anterioris), as well as grooves for the subclavian vein and artery. The 2nd rib has a pronounced tuberosity for the serratus anterior muscle.
Pectoral girdle: Clavicle and scapula
Pectoral girdle (cingulum membri superioris) is formed by the clavicle and scapula. The clavicle (clavicula) has a body and two ends: a sternal end (extremitas sternalis) with an articular surface and an impression for the costoclavicular ligament, and an acromial end (extremitas acromialis). On the inferior surface are the groove for the subclavian muscle, the costal tuberosity, and near the lateral end — the conoid tubercle (tuberculum conoideum) and the trapezoid line (linea trapezoidea), which together form the tuberosity for the coracoclavicular ligament.
The scapula (scapula) is a flat bone with three borders (medial, lateral, superior) and three angles. The spine of the scapula runs across the posterior surface, transitioning into the acromion (acromion); the coracoid process (processus coracoideus) projects anteriorly. The lateral angle bears the glenoid cavity (cavitas glenoidalis) for the head of the humerus, bounded by the supraglenoid and infraglenoid tubercles.
Key points
- A typical vertebra includes a body, an arch with pedicles and laminae, a vertebral foramen, three processes, and two notches.
- The thoracic vertebra is distinguished by costal facets of the body and transverse process — a double point of rib fixation.
- The hallmark of a cervical vertebra is the foramen transversarium; CVI has a carotid tubercle, CVII has a long spinous process.
- The atlas lacks a body, has lateral masses and a facet for the dens; the axis bears a dens with two articular surfaces.
- Lumbar vertebrae are large, with costal, mammillary, and accessory processes.
- The sacrum has a base, apex, pelvic and dorsal surfaces with three crests, a canal, and a sacral hiatus.
- The sternum consists of the manubrium, body, and xiphoid process; ribs are divided into true, false, and floating.
- The clavicle connects the sternum to the acromion of the scapula; the scapula bears the glenoid cavity for the humerus.