Functions and Divisions of the Skeleton

Provides support as a framework for the body.
Offers protection for vital organs and structures.
Enables movement through attachment of skeletal muscles via tendons.
Acts as a reservoir for mineral storage, primarily calcium and phosphorus.
Facilitates blood cell formation through a process known as hematopoiesis.
Stores triglycerides in yellow marrow, which contains adipose tissue for energy.

Axial Skeleton: Comprises bones around the body's longitudinal axis, such as the sacrum.
Appendicular Skeleton: Includes bones of the upper and lower limbs and the girdles connecting limbs to the axial skeleton, exemplified by the hip bone.

Total count includes 206 named bones, but additional unnamed bones may exist in various individuals.

Pectoral Girdles: Includes 2 clavicles and 2 scapulae.
Upper Limbs: Total of 28 bones including 2 humeri, 2 ulnas, 2 radii, 16 carpals, 10 metacarpals, and 28 phalanges.
Pelvic Girdle: Composed of 2 hip bones.
Lower Limbs: Contains 28 bones including 2 femurs, 2 patellae, 2 fibulas, 2 tibias, 14 tarsals, 10 metatarsals, and 28 phalanges.
Subtotal: The appendicular skeleton totals 126 bones.

Long Bones: Characterized by being longer than wide, with a shaft and two ends; examples include all limb bones except carpals, tarsals, and patella.
Short Bones: Cube-shaped bones found in the wrist and ankle regions.
Flat Bones: Thin, flattened bones such as the sternum, ribs, skull, and scapulae.
Irregular Bones: Bones with complex shapes, including vertebrae and hip bones.
Sesamoid Bones: Specialized short bones formed within tendons, with the patella being the largest; these vary in number among individuals.

Compact Bone: Dense outer layer found in most bones, appearing solid but containing small cavities for nerves and blood vessels.
Spongy Bone: Inner bone structure featuring trabeculae, organized along stress lines, and housing red or yellow marrow.

Diaphysis: Central shaft composed of compact bone surrounding the medullary cavity, which contains yellow/red bone marrow.
Epiphyses: Bone ends made of compact bone outside and spongy bone inside; can contain red or yellow marrow.
Epiphyseal Plate/Line: Growth area in children (plate) that becomes a line in adults as growth ceases.
Membranes:
- Periosteum: Connective tissue covering bone; assists in muscle attachment.
- Endosteum: Delicate inner membrane involved in bone remodeling throughout life.
Articular Cartilage: Covers joint surfaces, cushioning bone ends and absorbing stress.

Simplified structure compared to long bones.
Features two layers of compact bone with a spongy bone layer in between, resembling an Oreo cookie.
External layer covered by periosteum, followed by compact bone, spongy bone, and lined with endosteum; marrow spaces contain red or yellow marrow.