chapter 6 bone and bome tissue

The Skeletal System

  • Components: Bones, joints, and supporting tissues

  • Bones: 206 in adults, consist of osseous tissue, collagenous tissue, irregular connective tissue, and bone marrow.

Functions of the Skeletal System

  • Protection: Shields organs (e.g., skull, ribs)

  • Mineral Storage: Stores calcium, phosphorus, magnesium; crucial for electrolyte balance.

  • Blood Cell Formation: Red bone marrow involved in hematopoiesis.

  • Fat Storage: Yellow bone marrow contains adipocytes.

  • Movement: Skeletal muscles attach to bones for movement.

  • Support: Provides structural framework and supports body weight.

Classification of Bones by Shape

  • Long Bones: Longer than wide (e.g., limbs)

  • Short Bones: Cube-shaped (e.g., wrist/ankle)

  • Flat Bones: Thin and broad (e.g., skull, pelvis)

  • Irregular Bones: Complex shapes (e.g., vertebrae)

  • Sesamoid Bones: Embedded in tendons (e.g., kneecap)

Structure of a Long Bone

  • Periosteum: Dense outer membrane with blood vessels/nerves

  • Diaphysis: Bone shaft with medullary cavity (filled with marrow)

  • Epiphyses: Ends of the bone; contain red marrow and articular cartilage

  • Compact Bone: Resilient outer layer

  • Spongy Bone: Inner framework, location for marrow

Bone Marrow

  • Yellow Marrow: Adipocytes and blood vessels.

  • Red Marrow: Hematopoietic cells; shifts from red to yellow with age.

Bone Cells

  • Osteoblasts: Build bone, mature into osteocytes

  • Osteocytes: Maintain bone matrix

  • Osteoclasts: Resorb bone and release minerals into blood.

Bone Formation: Ossification

  • Ossification: Bone formation process, includes:

    • Intramembranous Ossification: Formation of flat bones from mesenchymal membranes.

    • Endochondral Ossification: Long and short bones formed from a cartilage model.

Bone Remodeling

  • Dynamic Tissue: Continuous bone formation (via osteoblasts) and resorption (via osteoclasts).

  • Stimuli for Remodeling: Calcium homeostasis, repair, mechanical stress.

Hormones Influencing Bone Growth

  • Growth Hormone: Stimulates chondrocytes and osteoblasts.

  • Testosterone & Estrogen: Promote growth; affect closure of epiphyseal plates.

Bone Repair**

  • Healing Steps: 1) Hematoma formation, 2) Soft callus formation by fibroblasts and chondroblasts, 3) Bone callus by osteoblasts, 4) Remodeling to secondary bone.

  • Fracture Types: Simple, compound, spiral, compression, comminuted, avulsion, greenstick.