Skeletal System Quiz

Skeletal System Anatomy and Physiology

• The skeletal system's main functions include support, protection, movement, blood cell production, and storage.
• It supports the body by providing a framework for tissues.
• It protects vital organs like the brain, heart, and lungs.
• It acts as levers for muscular action, facilitating movement.
• Red bone marrow within bones produces blood cells through a process called hemopoiesis.
• Bones serve as a reservoir for minerals (calcium, phosphorus) and fats.

Composition of the Skeletal System

• The skeletal system is composed of bones, cartilage, ligaments, tendons, and joints.
• These components contribute to the strength, flexibility, and support provided by the skeletal system.

Extracellular Matrix

• The extracellular matrix consists of proteins (collagen) and minerals (hydroxyapatite).
• Collagen provides tensile strength, similar to steel bars in a framework/concrete.
• Hydroxyapatite, primarily calcium phosphate, acts as the mineralized concrete providing compression strength.
• Proteoglycans maintain flexibility and water retention within the matrix.

Bone Markings

• Bone markings are not smooth, but rather display features indicative of attachment points for muscles, tendons, ligaments, nerves, and blood vessels.
• Articulations are points where bones meet.
• Projections are parts of the bones that extend above the surface.
• Holes, openings, or grooves are indentations in the bone.

Classification of Bones

• Long bones: Longer than wide; feature a shaft with ends. Examples include the femur and humerus.
• Short bones: Generally cube-shaped; primarily spongy bone. Examples include carpals and tarsals.
• Flat bones: Thin and flattened, usually curved with thin layers of compact bone surrounding a layer of spongy bone. Examples include skull, ribs and sternum.
• Irregular bones: Irregular shape; do not fit neatly into the other categories. Examples include vertebrae and hip bones.
• Sesamoid bones: Small, oval-shaped bones located within tendons. The patella is a common example.
• Sutural bones: Small bones located between flat bones of the skull, typically found at the sutures.

Structure of a Bone (Long Bone)

• Diaphysis: The shaft of the long bone, mainly composed of compact bone.
• Epiphysis: The ends of the bone, primarily composed of spongy bone.
• Metaphysis: The regions between the diaphysis and epiphyses; contains the epiphyseal growth plate.
• Articular cartilage: Covers the epiphyses, reducing friction at joint surfaces; made of hyaline cartilage.
• Periosteum: A fibrous connective tissue membrane covering the outer surface of the diaphysis (shaft).
• Perforating fibers (Sharpey's fibers): Secure the periosteum to the underlying bone.
• Medullary cavity: A cavity within the diaphysis, typically containing yellow marrow (mostly fat) in adults, and red marrow in areas of blood cell production.
• Endosteum: A thin membrane lining the medullary cavity and the internal spaces of spongy bone.

Bone Histology

• Osteoblasts: Bone forming cells.
• Osteocytes: Mature bone cells residing in lacunae.
• Osteoclasts: Bone resorbing cells (breaking down bone tissue).
• Compact bone: Dense bone with osteons (Haversian systems).
• Spongy bone (Cancellous bone): Trabecular structure housing red bone marrow.

Osteoprogenitor Cells

• Undifferentiated cells develop from this stem cell population that are responsible for creating osteoblasts.

Osteoblasts

• Builds bone tissue by creating the organic bone extracellular matrix/framework.

Osteocytes

• Mature bone cells residing within spaces called lacunae, maintaining cellular function in response to metabolic needs.

Osteoclasts

• Break down bone tissue and release minerals into the bloodstream.

Compact Bone Tissue

• Osteons (Haversian systems): Cylindrical structural units of compact bone containing concentric lamellae.
• Concentric lamellae: Ring-like structural units comprised of mineralized matrix around a central canal.
• Central (Haversian) canal: Contains blood vessels and nerves.
• Lacunae: Small spaces that house osteocytes.
• Canaliculi: Tiny channels connecting lacunae to the central canal.
• Interstitial Lamellae: Found between osteons; fragments of older osteons that have been remodeled.
• Circumferential Lamellae: Rings of lamellae surrounding the entire outer and inner surface of bone.

Spongy Bone Tissue

• Trabeculae Irregular patterns of lamellae;contain osteocytes in lacunae connected by canaliculi;provide structural support with minimal weight.
• Bone Marrow: Red bone marrow produces blood cells; yellow bone marrow stores adipose tissue.

Bone Ossification

• Intramembranous ossification: Bone forms directly within mesenchyme; common formation for flat bones of the skull.
• Endochondral ossification: Bone forms within hyaline cartilage; common formation method for long bones.

Bone Growth in Length

• Interstitial growth: Cartilage growth at the epiphyseal side.
• Endochondral ossification: Cartilage replacement by bone on the diaphyseal side.
• Epiphyseal plate: Central structure for length growth, composed of hyaline cartilage.
• Zones of the epiphyseal plate: Resting, Proliferating, Hypertrophic, and Calcified cartilage.

Bone Growth in Thickness

• Appositional growth: Bone thickens through the addition of new layers of bone tissue on the outer surface via bone ridges, tunnels, and new osteons.

Bone Remodeling

• Continuous process of replacing old bone tissue with new tissue.
• Involves bone resorption (osteoclasts) and bone deposition (osteoblasts).

Phases of Bone Fracture Repair

• Reactive phase: Formation of a fracture hematoma.
• Reparative phase: Fibrocartilaginous and bony callus formation.
• Bone remodeling phase: Remodeling to restore the functional structure of the bone.

Healing Time and Factors Affecting Healing

• Healing time depends on fracture severity and bone location.
• Factors affecting healing include blood supply to the bone, age, and overall health, and nutritional intake (calcium and phosphorus).

Common Fractures

• Different types of fractures include open, comminuted, greenstick, impacted, Colles', and Pott's fractures.

Benefits of Bone Remodeling

• Strength enhancement
• Shape adjustment
• Fracture resistance

Factors Affecting Bone Health (Minerals and Vitamins)

• Minerals: Calcium, Phosphorus, Magnesium, Fluoride, and Manganese.
• Vitamins: A, C, D, K, and B12.

Factors Affecting Bone Health (Hormones)

• Insulin-like Growth Factors: Stimulate osteoblasts and promote cell division.
• Thyroid Hormones: Promote bone growth by stimulating osteoblasts.
• Insulin: Promotes bone growth by enhancing bone protein synthesis.
• Sex Hormones: Estrogen and androgen: cause rapid bone growth, promote bone growth by stimulating osteoblasts, and regulate remodeling and resorption in adulthood. They also influence bone development and maturity.
• Other hormones: Parathyroid Hormone, Calcitriol (active Vitamin D), and Calcitonin, influence bone remodeling.

Exercise and Bone Health

• Moderate weight-bearing exercise stimulates bone growth and strengthening, maintaining bone density.
• Exercise helps maintain healthy bones throughout life.