Skeletal System Quiz

Osseous System

• A bone is an organ composed of various tissues working together, including osseous tissue, cartilage, dense connective tissue, epithelium, adipose tissue, and nervous tissue.
• The skeletal system encompasses all bones and their cartilages.
• Osteology is the study of bone structure and bone disorders.

Functions of Bone

• Support: The skeleton provides a framework for soft tissues and attachment points for muscles.
• Protection: Bones safeguard vital organs like the brain (cranial bones) and heart/lungs (rib cage).
• Movement: Skeletal muscles, connected to bones, generate movement through contraction.
• Mineral Homeostasis: Bones store minerals, notably calcium and phosphorus, crucial for maintaining homeostasis and distributing minerals to the body. They store 99% of the body's calcium.

Functions of Bone: Continued

• Blood Cell Production: Red bone marrow within certain bones (hip, ribs, sternum, vertebrae) produces red blood cells, white blood cells, and platelets (hemopoiesis).
• Triglyceride Storage: Yellow bone marrow, primarily composed of adipose cells, stores triglycerides as a chemical energy reserve.

Types of Bones

• Long Bones: Longer than wide, with a shaft and extremities (e.g., femur, tibia, fibula).
• Short Bones: No shafts or extremities; diverse shapes and sizes (e.g., carpals, metacarpals).
• Irregular Bones: Diverse shapes and sizes with no particular features (e.g., vertebrae, some skull bones).
• Flat Bones: Thin, flat surfaces, often broad (e.g., sternum, ribs, majority of skull bones).
• Sesamoid Bones: Shaped like sesame seeds, embedded within tendons (e.g., patella).

Bone Structure

• Diaphysis: The shaft or body of a long bone.
• Epiphyses: The proximal and distal ends of a long bone.
• Metaphyses: The regions connecting the diaphysis and epiphyses; contains epiphyseal plate in growing bones that allows lengthening.
• Articular Cartilage: Hyaline cartilage covering the epiphyses, reducing friction in joints.

Bone Structure: Continued

• Periosteum: A tough connective tissue sheath surrounding the bone (except at articular surfaces), essential for nerve and blood supply, growth, and repair.
• Medullary Cavity: Hollow space within the diaphysis filled with fatty yellow bone marrow in adults.
• Endosteum: A thin membrane lining the medullary cavity, containing bone-forming cells.

Bone Cells

• Osteoprogenitor cells: Stem cells developing into osteoblasts.
• Osteoblasts: Bone-building cells that secrete the organic components of bone matrix and initiate calcification.
• Osteocytes: Mature bone cells maintaining bone metabolism and exchanging nutrients/wastes with the blood.
• Osteoclasts: Bone-resorbing cells breaking down bone matrix.

Compact (Cortical) Bone

• Primarily comprises osteons, cylindrical units of compact bone tissue with concentric lamellae surrounding a central canal with nerves, lymphatics, and blood vessels.
• The arrangement of osteons within the bone helps to provide strength against force vectors.
• Interstitial lamellae fill spaces between osteons.
• Canaliculi connect lacunae to central canals.

Spongy (Cancellous, Trabecular) Bone

• Forms a framework, called trabeculae, where bone marrow is held.
• Lighter than compact bone due to its porous structure, but still strong.
• Contains red bone marrow, responsible for blood cell formation.
• Trabeculae are arranged along stress lines to strengthen the bone.
• Nourished through diffusion because there is no central canal.

Ossification

• Also known as osteogenesis, the process of bone development.
• It occurs throughout life in four main situations: initial bone formation in embryo/fetus, growth, bone remodelling, and fracture repair.
• Long bones lengthen through the activity of the epiphyseal plates, which are replaced by epiphyseal lines during adulthood.
• Secondary ossification centers develop within the epiphyses to continue bone growth.

Development of Long Bones

• Ossification begins at the primary ossification center in the diaphysis, and secondary centers appear later at the epiphyses.
• Cartilage is replaced by bone tissue as ossification progresses.

Bone Remodeling

• Constant turnover of bone, mediated by osteoblasts and osteoclasts.
• Approximately 10% of bone is replaced annually, though rates vary.
• Remodeling adjusts to stress placed on the bone.

Joints

• The sites where two or more bones come together.
• They vary in their degree of movement.

Types of Joints

• Fibrous joints: No synovial cavity, held together by dense irregular connective tissue (e.g., sutures in the skull).
• Cartilaginous joints: No synovial cavity, held together by cartilage (e.g., symphysis pubis, ribs to sternum).
• Synovial joints: Synovial cavity, enclosed by a fibrous capsule lined with synovial membrane and lubricated by synovial fluid. (e.g., the shoulder, knee).

Synovial Joints continued

• Characteristics of Synovial Joints: Articular cartilage, capsule, synovial membrane, synovial fluid, intracapsular, and extracapsular structures.

Disorders of Joints

• Rheumatoid Arthritis (RA): Chronic inflammatory autoimmune disease primarily affecting synovial joints.
• Osteoarthritis (OA): Degenerative disease of articular cartilage occurring gradually, often asymptomatic initially.
• Sprains, strains, and dislocations: Injuries to soft tissues, tendons, and ligaments around the joint, which may or may not include damage to intracapsular structures.
• Penetrating injuries: Injuries that can result in damage to the joint structure, possible healing complications including infection, and long-term effects.
• Gout: Deposition of sodium urate crystals in joints and tendons, causing inflammation.