ch_05_lecture_presentation

Chapter 5: The Skeletal System

Overview of the Skeletal System

• Components:

  • Bones (skeleton)

  • Joints

  • Cartilages

  • Ligaments

• Subdivisions of the Skeleton:

  • Axial Skeleton:

  • Appendicular Skeleton

Functions of Bones

• Support:

  • Provides a framework that supports the body.

• Protection:

  • Protects vital organs (e.g., skull protects the brain, rib cage protects thoracic cavity organs).

• Movement:

  • Works with skeletal muscles to allow movement.

• Mineral and Fat Storage:

  • Stores important minerals such as calcium and phosphorus

  • Stores fat in the internal marrow cavity.

• Hematopoiesis:

  • Blood cell formation occurs in the marrow.

Bones of the Human Body

• Total Number of Bones in Adults:

  • 206 bones

• Bone Types:

  • Compact Bone:

    • Homogeneous structure.

  • Spongy Bone:

    • Composed of small needle-like pieces with many open spaces.

Classification of Bones by Shape

• Types of Bones:

  • Long Bones:

    • Longer than they are wide (e.g., femur, humerus).

  • Short Bones:

    • Cube-shaped (e.g., carpals, tarsals).

  • Flat Bones:

    • Thin and curved (e.g., skull, ribs, sternum).

  • Irregular Bones:

    • Irregular shape (e.g., vertebrae, hip bones).

Anatomy of Long Bones

• Diaphysis:

  • Shaft composed of compact bone.

• Epiphysis:

  • Ends of the bone, primarily spongy bone.

• Periosteum:

  • Outside covering of the diaphysis; fibrous connective tissue.

• Articular Cartilage:

  • Covers external surface of epiphyses, made of hyaline cartilage to decrease friction.

• Epiphyseal Plate and Line:

  • Plate is hyaline cartilage in growing bones; line is the remnant in adult bones.

• Marrow Cavity:

  • Cavity within the shaft that contains yellow bone marrow in adults and red marrow for blood cell formation in infants.

Bone Markings

• Types:

  • Projections/Processes:

    • Grow out from the bone surface.

  • Depressions/Cavities:

    • Indentations in bone surfaces.

Microscopic Anatomy of Bone

• Osteon (Haversian System):

  • Unit of bone containing a central canal and matrix rings.

• Lacunae:

  • Cavities containing osteocytes (bone cells).

• Canaliculi:

  • Tiny canals that connect lacunae to the central canal.

Bone Growth (Ossification)

• Epiphyseal Plates:

  • Allow lengthwise growth in childhood.

• Bone Remodeling:

  • Occurs throughout life in response to calcium levels and gravitational pull.

  • Involves osteoblasts (bone-forming cells) and osteoclasts (bone-destroying cells).

Bone Fractures

• Types:

  • Closed (Simple):

    • Does not penetrate the skin.

  • Open (Compound):

    • Penetrates through the skin.

  • Common Fractures:

    • Comminuted, compression, depressed, impacted, spiral, and greenstick fractures.

• Repair Process:

  • Hematoma formation, fibrocartilage callus, bony callus formation, and remodeling.

Axial Skeleton

• Components:

  • Skull, vertebral column, bony thorax.

Skull Anatomy

• Sets of Bones:

  • Cranium and facial bones, joined by sutures.

  • Only the mandible is movable.

Vertebral Column

• Structure:

  • Consists of 24 singular vertebrae and two composite bones (sacrum and coccyx).

• Curvatures:

  • Primary (thoracic and sacral) present at birth, secondary (cervical and lumbar) develop with growth.

Appendicular Skeleton

• Components:

  • Composed of 126 bones, including limb bones and girdles.

Joints

• Functions:

  • Hold bones together and allow movement.

• Classification:

  • Functional (e.g., synarthroses, amphiarthroses, diarthroses) and structural (e.g., fibrous, cartilaginous, synovial).

Synovial Joints

• Characteristics:

  • Articulating bones are separated by a joint cavity filled with synovial fluid, which reduces friction.

Inflammatory Conditions of Joints

• Bursitis:

  • Inflammation of a bursa.

• Tendonitis:

  • Inflammation of tendon sheaths.

• Arthritis:

  • Affects joints, with different forms like osteoarthritis and rheumatoid arthritis.

Developmental Aspects of the Skeletal System

• At Birth:

  • Skull bones incompletely formed with fontanels that allow compression during birth and brain growth.

• Skeletal Changes:

  • Bones develop from cartilage and fibrous membranes, and various ages show distinctive changes in proportional sizes and developmental stages.