Skeletal System

The human skeleton has a total of 206 bones, divided into two main divisions:
- Axial skeleton (80 bones): skull, vertebrae, sternum, and ribs.
- Appendicular skeleton (126 bones): limbs and girdles.
Functions and Composition:
- The skeleton provides a framework for body movement, made of bones and cartilage (specialized connective tissue).
- Bones have a hard matrix due to calcium salts.
Rib Cage:
- Consists of the thoracic vertebrae, sternum, and 12 pairs of ribs (24 bones).
- True ribs (1–7): directly attached to sternum.
- False ribs (8–10): indirectly attached.
- Floating ribs (11–12): not attached ventrally; protect kidneys.
- Each rib is bicipital (has two ends).
Vertebral Column (26 bones):
- Cervical (7), thoracic (12), lumbar (5), sacrum (1 fused), coccyx (1 small).
- First vertebra: Atlas, second: Axis (supports head rotation).
Pelvic Girdle:
- Formed by two coxal bones (right and left halves), each made of ilium, ischium, and pubis.
- The acetabulum articulates with the femur head to form the hip joint.
- Pubic bones meet at the pubic symphysis (white fibrous cartilage).
Other labeled bones: Clavicle (collarbone), Scapula (shoulder blade), Humerus, and Sternum.