Skeletal

  • Diaphysis:

    • Long, tubular shaft of the bone.

    • Mainly composed of compact bone for strength and support.

  • Epiphysis:

    • Ends of the long bone.

    • Features spongy bone covered by compact bone, involved in joint articulation.

  • Metaphysis:

    • Area between diaphysis and epiphysis.

    • Contains growth plate (epiphyseal plate) in growing bones for lengthening.

  • Articular Cartilage:

    • Smooth, white tissue covering epiphyses.

    • Reduces friction and absorbs shock at joints.

  • Periosteum:

    • Dense layer of vascular connective tissue surrounding bones (except joint surfaces).

    • Contains nerves and blood vessels; crucial for bone growth and repair.

  • Medullary Cavity:

    • Hollow space within the diaphysis.

    • Contains yellow marrow (stores fat) and red marrow (produces blood cells).

  • Endosteum:

    • Thin membrane lining the medullary cavity.

    • Involved in bone growth, repair, and remodeling.

    Name of bone marking Description

    Projections That Are Sites of Muscle and Ligament Attachment Tuberosity: Large, rounded projection; may be roughened Crest: Narrow ridge of bone; usually prominent Trochanter: Very large, blunt, irregularly shaped process (only example is on femur) Line: Narrow ridge of bone; less prominent than a crest Tubercle: Small, rounded projection or process

    Epicondyle: Raised area on or above a condyle

    Spine: Sharp, slender often pointed projection

    Process: Any bony prominence

    Projections: That Help to Form Joints

    Head: Bony expansion carried on a narrow neck

    Facet: Smooth, nearly flat articular surface

    Condyle: Rounded articular projection

    Ramus: Armlike bar of bone

    Depressions and Openings Allowing Blood Vessels and Nerves to Pass

    Meatus: Canal-like passageway

    Sinus: Cavity within a bone, filled with air and lined with mucous membrane

    Fossa: Shallow, basin like depression in a bone, often serving as an articular surface

    Groove: Furrow

    Fissure: Narrow, slit like opening

    Foramen: Round or oval opening through a bone

    There are 2 major divisions of the human skeleton:

    • Axial Skeleton - Skull, Vertebral Column, Thoracic Cage

    • Appendicular Skeleton - Limbs and the “points of attachment”

    Long Bone:

    • Typically longer than wide

    • Feature a shaft with proximal and distal heads

    • Examples: Femur, Humerus

    Short Bone:

    • Generally cube-shaped.

    • They contain mostly spongy bone encased in compact bone.

    • Examples include carpals and tarsals.

    Flat Bone:

    • Thin, flattened, and often curved.

    • They consist of two layers of compact bone enclosing a layer of spongy bone, similar to the structure of short bones.

    • Examples include the skull, ribs, and sternum.

    Irregular Bone:

    • They do not conform to other bone classification categories.

    • Examples include vertebrae and hip bones.

    Exceptions to the Rule of Shape… Sesamoid bones

    • Sesamoid bones are small, round bones found within tendons.

    • They serve to protect tendons and enhance their mechanical function.

    • A notable example of a sesamoid bone is the patella, or kneecap, which differs from a short bone classification.

    Histology - Microscopic Structure of Bone

    1. Compact bone tissue, also called hard or cortical bone tissue

    2. Spongy bone tissue, also called cancellous or trabecular bone.

    Compact Bone Histology

    • Compact bone is a dense and strong tissue forming the outer layer of bones.

    • Functional Organization:

      • Osteons (Haversian Systems) are the key structural units.

      • Comprised of concentric lamellae surrounding a central canal (Haversian canal) with blood vessels and nerves.

      • Bone cells reside in lacunae and are interconnected by canaliculi.

    Spongy Bone Histology

    • Spongy bone is a less dense type of bone tissue located at the ends of long bones and within various other bones and vertebrae.

    • Red marrow, which is involved in blood cell production, is found in the spaces of spongy bone.

    • Trabeculae are the fundamental structural units of spongy bone, featuring thin, rod-like structures that form a three-dimensional lattice.

    • The spaces within the trabeculae are filled with red bone marrow, which plays a crucial role in blood cell production.

    Types of Bone Cells

    • Osteocytes are mature bone cells located within the bone matrix.

    • Osteoblasts are responsible for bone formation.

    • Osteoclasts function to break down bone matrix for remodeling and to release calcium, in response to parathyroid hormone.

    • Bone remodeling involves the collaborative actions of both osteoblasts and osteoclasts.