Chapter+7+API

Overview of the Skeletal System

  • The skeletal system is composed of organs and various tissues including:
    • Bone tissue
    • Cartilage
    • Dense connective tissue
    • Blood
    • Nervous tissue
  • Characteristics of the skeletal system:
    • It is alive, multifunctional, providing:
    • Support and protection for softer tissues
    • Facilitation of movement
    • Blood cell formation (function of bone marrow)
    • Mineral storage
  • Divisions of the skeletal system:
    • Axial skeleton
    • Appendicular skeleton

Bone Shape and Structure

  • Variation of bones in terms of:
    • Size
    • Shape
  • Similarities among bones:
    • Structure
    • Development
    • Function

Bone Classification by Shape:

  1. Long Bones:
    • Characteristics: Long and narrow with expanded ends.
    • Examples: Femur, humerus.
  2. Short Bones:
    • Characteristics: Cube-like in shape; length equals width. Includes sesamoid bones (round bones embedded in tendons).
    • Examples: Wrist and ankle bones.
  3. Flat Bones:
    • Characteristics: Plate-like with broad surfaces.
    • Examples: Skull bones, sternum.
  4. Irregular Bones:
    • Characteristics: Variety of shapes and often connected to several other bones.
    • Examples: Vertebrae.

Anatomy of Long Bones

  • Major Parts of a Long Bone:
    • Epiphysis: Expanded end of the bone.
    • Diaphysis: Long shaft of the bone.
    • Metaphysis: Transitional area between diaphysis and epiphysis, often wider.
    • Articular cartilage: Covers the epiphysis, provides cushioning.
    • Periosteum: Dense connective tissue that encloses the bone.
    • Compact (cortical) bone: Dense outer layer of the bone making up the diaphysis.
    • Spongy (cancellous) bone: Light, porous tissue that makes up the epiphyses.
    • Trabeculae: Branching plates of bony tissue in spongy bone.
    • Medullary cavity: Hollow chamber in the diaphysis that contains marrow.
    • Endosteum: Thin membrane lining the medullary cavity and spaces within the spongy bone.
    • Bone marrow:
    • Red marrow: Responsible for blood cell production.
    • Yellow marrow: Primarily stores fat.

Microscopic Structure of Bone

  • Osteocytes: Mature bone cells located within the bone matrix.
  • Lacunae: Chambers that house osteocytes.
  • Canaliculi: Tiny passageways that allow for nutrient and waste exchange between osteocytes.
  • Extracellular Matrix:
    • Mainly composed of collagen fibers and inorganic salts (like calcium phosphate).
    • Collagen: Provides resilience to bones.
    • Inorganic salts: Contribute to the hardness of bone.

Types of Bone Tissue

Compact Bone:

  • Composed of osteons (structural units).
  • Features:
    • Central canal containing blood vessels and nerves.
    • Concentric layers of matrix called lamellae surrounding the central canal.
    • Strong and solid, providing weight-bearing support and resistance to compression.

Spongy Bone:

  • Composed of branching plates called trabeculae.
  • Characteristics:
    • More flexible and lightweight due to the open structure.

Bone Function

Major Functions of Bones:

  1. Provide shape to the body.
  2. Support body structures, including:
    • Weight support from lower limbs, pelvis, and vertebral column.
    • Protection of organs (e.g., skull protects brain, rib cage protects lungs and heart).
  3. Facilitate movement in conjunction with muscles.
  4. Contain tissue that produces blood cells through hematopoiesis.
  5. Store inorganic salts, mainly calcium.

Blood Cell Formation

  • Hematopoiesis: Process of blood cell formation occurring in red bone marrow.
    • Types of cells produced:
    • Red blood cells
    • White blood cells
    • Platelets
  • Yellow bone marrow: Responsible for fat storage and does not produce blood cells.
  • As individuals age, red marrow can be replaced by yellow marrow in certain locations:
    • Remains in adults in areas such as the skull, ribs, sternum