Ch-06-Osseous-Tissue-handout

Chapter 6: Osseous (Bone) Tissue in Human Anatomy

Overview of the Skeletal System

• Components:

  • Skeletal bones

  • Cartilage

  • Ligaments

  • Connective tissue

• Divisions:

  • Axial Skeleton: Skull, spine, ribs

  • Appendicular Skeleton: Limbs, pelvis

• Functions of the Skeletal System:

  • Support: Provides structural support for the body.

  • Protection: Protects vital organs (e.g., heart, brain).

  • Mineral Storage: Stores calcium and phosphate ions.

  • Hematopoiesis: Blood cell production occurs in red bone marrow.

  • Energy Storage: Adipose tissue in yellow bone marrow stores energy.

  • Energy Metabolism: Bones secrete osteocalcin, which plays a role in regulating blood sugar and fat storage.

  • Movement: Bones act as levers for muscles.

Chapter 7: Bone Classification

Six Broad Categories of Bone Types

• Based on Shape:

  • Flat Bones: Ex: Parietal bone

  • Sutural Bones: Ex: Wormian bones

  • Long Bones: Ex: Humerus, femur, phalanges

  • Short Bones: Ex: Carpal bones, tarsal bones

  • Sesamoid Bones: Ex: Patella

  • Irregular Bones: Ex: Vertebrae

Bone Markings

• Depressions:

  • Fossa

  • Sulcus

• Openings:

  • Foramen

  • Meatus/canal

  • Fissures

• Elevations/Projections:

  • Ramus

  • Processes for tendon/ligament attachment

  • Articular surfaces

Chapter 6: Histology of Compact Bone

Basic Functional Unit

• Osteons: Arrangements of structures within compact bone.

Composition of Bone Matrix

• Organic Component:

  • 1/3 is collagen fibers providing flexibility.

• Inorganic Component:

  • 2/3 consist of hydroxyapatite (calcium salts) providing rigidity.

  • Important for resisting compression but contributes to inflexibility.

Bone Cells

• Osteogenic Cells:

  • Stem cells that produce osteoblasts.

• Osteoblasts:

  • Immature bone cells, responsible for producing new bone matrix and secreting osteoid.

• Osteocytes:

  • Mature bone cells maintaining the bone matrix, recycling proteins and minerals.

• Osteoclasts:

  • Derived from immune cells, multinucleated, involved in bone resorption (breaking down bone).

Connective Tissue Coverings

• Periosteum:

  • Two layers: Fibrous (outer) and Osteogenic (inner).

  • Contains perforating fibers attached to bone.

• Endosteum:

  • Contains osteogenic, osteoblasts, and osteoclasts.

Types of Osseous Tissue

• Compact Bone (Dense Bone):

  • Forms the walls of bones; osteons arranged parallel to the bone axis.

  • Contains medullary cavity for marrow; great strength from end to end.

• Spongy Bone:

  • Open network of trabecular plates; less strength compared to compact bone.

  • Lacks central canals; canaliculi open into cavities.

Long Bone Structure

Anatomy of Long Bones

• Epiphysis:

  • Ends of long bones; covered by articular cartilage; contains spongy bone with red marrow.

• Diaphysis:

  • Shaft of long bone; thick compact bone wall; contains yellow bone marrow in medullary cavity.

• Metaphysis:

  • Narrow zone between epiphysis and diaphysis containing growth plate in children (epiphyseal line in adults).

Vascularization and Innervation

• Nutrient Foramen:

  • Site for entry of nutrient vessels, lymphatic vessels, and sensory nerve fibers.

• Metaphyseal Vessels:

  • Supply the metaphysis.

• Periosteal Vessels:

  • Supply outer layers of bone.

Bone Development and Growth

Osteogenesis and Ossification

• Osteogenesis:

  • Bone formation process involving osteoblasts producing osteoids.

• Ossification:

  • Replacement of cartilage or mesenchyme with bone.

Types of Ossification

• Endochondral Ossification:

  • Develops long bones, vertebrae, and hips from a cartilage model.

• Intramembranous Ossification:

  • Forms flat bones of the skull and mandible from embryonic connective tissue (mesenchyme).

Remodeling and Fractures

Bone Remodeling

• Inactivity leads to bone degeneration; physical activity strengthens bones.

Types of Fractures

• Closed (Simple):

  • Does not break skin.

• Open (Compound):

  • Breaks skin surface.

• Types of Breaks:

  • Transverse, oblique, spiral, compression, comminuted.

  • Nondisplaced vs. displaced fractures.

Bone Repair and Aging

Bone Repair Process

• Healing involves:

  1. Fracture hematoma formation

  2. Soft callus formation

  3. Bony callus formation

  4. Bone remodeling

Aging and the Skeletal System

• Changes with age:

  • Osteomalacia (before osteoporosis); associated with Vitamin D deficiency.

  • Bone density changes reflect bone cell activity: osteoblasts vs. osteoclasts.