The human adult skeleton typically consists of 206 bones. These bones can be classified into two main categories:
1. Axial Skeleton: This includes the bones along the body's central axis and includes the following bones:
- Skull: The human skull is made up of 22 bones, including the cranial bones that encase the brain and the facial bones that give the face its structure.
- Vertebrae: There are 24 vertebrae in the vertebral column, along with the sacrum and coccyx, which are composed of fused vertebrae.
- Ribcage: The ribcage consists of 12 pairs of ribs, making a total of 24 individual ribs. These ribs are attached to the thoracic vertebrae and the sternum, or breastbone.
2. Appendicular Skeleton: This part of the skeleton includes the bones of the limbs and the girdles that connect them to the axial skeleton. It consists of the following bones:
- Upper Limbs: Each upper limb includes the humerus in the upper arm, the radius and ulna in the forearm, and a series of bones in the hand, including carpals (wrist bones), metacarpals (palm bones), and phalanges (finger bones). In total, there are 64 bones in both upper limbs.
- Lower Limbs: Each lower limb consists of the femur in the thigh, the tibia and fibula in the lower leg, and a series of bones in the foot, including tarsals (ankle bones), metatarsals (sole bones), and phalanges (toe bones). In total, there are 62 bones in both lower limbs.