Trunk bones in 3D

Structure of the trunk skeleton

Behind, the thoracic vertebrae carry the ribs, and below them the lumbar vertebrae and the sacrum take the weight of the upper body down to the pelvis. Each rib curves forward from the spine and continues as a costal cartilage. The first seven cartilages reach the sternum directly; ribs 8–10 join the cartilage above, and ribs 11 and 12 end free in the abdominal wall.

The sternum is a flat bone in the midline of the chest. The manubrium joins the clavicles and the first ribs, the body takes the cartilages of ribs 2–7, and the small xiphoid process points down towards the abdomen.

What the 3D model shows

The trunk bones view has 77 parts: thoracic vertebrae T1–T12, lumbar vertebrae L1–L5, the sacrum and the intervertebral discs from C7–T1 to L5–S1; the left and right ribs 1–12; the costal cartilages of the first seven ribs; and the manubrium, body and xiphoid process of the sternum. Each rib, cartilage and vertebra is a separate part you can select, hide or isolate. The cervical vertebrae, shoulder girdle and hip bones belong to other views.

How to study the trunk bones

In the anterior view find the sternal angle and count the ribs downwards from the second costal cartilage, the way it is done on the living chest. Turn to the posterior view and follow a single rib from its head on the vertebral bodies to its tubercle on the transverse process. Isolate the first, seventh, eleventh and twelfth ribs to compare their shapes. Then hide everything except the sternum and the cartilages, and recall from memory which ribs are true, false and floating.