The axial skeleton comprises the vertical axis of the skeleton; this includes the skull, vertebrae, bones of the thoracic cage, and the sacrum.
The appendicular skeleton comprises the bones that attach to the axial skeleton.
The adult skeleton has 206 bones; 80 of these are in the axial portion and 126 are in the appendicular skeleton.
Helpful directional terms: superior is towards the head and inferior is towards feet; medial is towards the midline of the body, and lateral is away from the midline.
We have 7 cervical vertebrae in the neck, 12 thoracic vertebrae in the thorax, and 5 lumbar vertebrae in the lower back.
Comprises the sternum, aka, breastbone, in the center, and 12 ribs that wrap around the thorax to protect the heart and lungs.
The ribs connect posteriorly to the thoracic vertebrae and anteriorly to the sternum via costal cartilages (the exception are the bottom two "floating ribs" that do not have anterior connections).
- Pectoral girdle (aka, shoulder girdle)
The clavicles (aka, the collarbones) and the scapulae (aka, shoulder blades).
The carpals, metacarpals, and phalanges. Notice that the thumb, which is the shortest finger, is the most lateral.
Sacrum and os coxa
The tarsals, metatarsals, and phalanges; notice that the big toe is most medial.
