3.1 the human skeleton

  • Main Functions of the Human Skeleton:

    • Protection: Encapsulates internal organs (e.g., ribs protecting thoracic region).

    • Structural Support: Provides a rigid framework to maintain body shape and prevent collapse.

    • Movement: Muscles span bones and cross joints. When muscles contract, they pull insertion sites toward origin anchors, creating leverage.

    • Mineral Storage: Acts as a reservoir for inorganic minerals, specifically calcium and phosphorus.

    • Blood Cell Production (haematopoiesis): Occurs within the red bone marrow found in the heads of long bones and flat bones.

    • Energy Storage: Found in yellow bone marrow, which consists of adipose tissue rich in ATP.


  • Comparison of Axial and Appendicular Skeleton:

    • Axial Skeleton:

    • Protection of internal viscera (brain, lungs, heart)

    • Anchor site for muscles, acting as core stabilisers

    • Anchor site for muscles acting at limbs

    • Extends from the head down to the coccyx (skull, vertebrae, thoracic cage)

    • Appendicular Skeleton:

    • Enables and facilitates mobility

    • Anchor for muscles that move the limbs, hands, and feet

    • Includes pectoral and pelvic girdles, bones of the limbs


  • Classification of Bones by Shape:

    • Long Bones:

    • Characteristics: Cylindrical, longer than wide.

    • Short Bones:

    • Characteristics: Cube-like/square, similar in length and width.

    • Flat Bones:

    • Characteristics: Thin, plate-like, often curved.

    • Sesamoid Bones:

    • Characteristics: Unique bones formed inside tendons to reduce friction and protect the tendon.

    • Irregular Bones:

    • Characteristics: Complex shapes with various projections or holes (sinuses)


  • Structural Regions of a Typical Long Bone:

    • Epiphysis: Head of the bone at proximal and distal ends, covered in smooth, glossy articular cartilage for pain-free joint movement.

    • Epiphyseal plate or line: Connects Epiphysis to the Metaphysis, a plate of cartilage during adolescent growth

    • Metaphysis: Neck of the bone that connects the head to the shaft.

    • Diaphysis: Long, cylindrical shaft of the bone containing the medullary cavity, covered in periosteum (protective connective tissue)

    • Medullary cavity: internal surface covered in endosteum, protective tissue. contains central neurovascular and yellow bone marrow

    • Membranes:

    • Periosteum: Tough outer membrane covering the external surface (external fibrous, internal cellular), does not cover bone ends/articular cartilage

    • Endosteum: Thin internal cellular layer lining the medullary cavity, maintains cellular environment for growth and repair.