Skeletal System Quiz

Skeletal System Overview

• The skeletal system is the major part of the body's skeleton.
• The matrix of bone is calcified by calcium and phosphate.
• The human skeleton comprises 206 bones.
• Bone is living, vascular connective tissue with a dense, white fibrous tissue matrix embedded in a calcium phosphate complex.
• Bone demonstrates a characteristic growth pattern and has significant regenerative power.
• Bone functions include shape and support; muscular attachment; acting as levers; protecting organs; erythropoiesis; and mineral storage.
• Bone is a hard, highly vascular, dynamic connective tissue.

Learning Outcomes

• Students will be able to list components, classifications, and major bony landmarks of axial and appendicular skeletons.
• Students will be able to describe the macroscopic and microscopic structure of long bones.
• Students will be able to explain ossification of bones and blood supply to long bones.

Classification of Bones

• Bones are classified according to shape, development, regional characteristics, structural features, and microscopic structure.

• According to shape: Long, short, flat, irregular, pneumatic, sesamoid, and accessory bones.

  • Long bones: Elongated shaft with expanded ends; examples: femur, humerus, metacarpals, clavicle.
  • Short bones: Smaller, usually cuboidal; examples: carpal and tarsal bones.
  • Flat bones: Thin, flattened plates; examples: ribs, sternum, scapula, skull bones.
  • Irregular bones: Complex shapes; examples: vertebrae, hip bones.
  • Pneumatic bones: Contain air spaces; examples: maxilla, sphenoid, ethmoid bones.
  • Sesamoid bones: Embedded within tendons; examples: patella, pisiform.
  • Accessory bones: Small, extra bones; examples: sutural bones.

• According to development: Membranous (dermal), cartilaginous, and membranous-cartilaginous bones.

  • Membranous bones: Formed from mesenchymal condensation; examples: skull vault and facial bones.
  • Cartilaginous bones: Develop from pre-existing cartilage models; examples: limb bones, vertebral column, and thoracic cage.
  • Membranous-cartilaginous bones: Ossify partly in membrane and partly in cartilage; examples: clavicle, mandible, and temporal bones.

• Regional classification: Axial skeleton (skull, vertebral column, and thoracic cage) and appendicular skeleton (limb bones).

Division of Skeletal System

• Total number of bones in an adult human body: 206

• Axial skeleton:

  • Skull: Cranium (8) and face (14).
  • Hyoid bone (1)
  • Auditory ossicles (3 in each ear).
  • Vertebral column (26).
  • Sternum (1).
  • Ribs (24).

• Appendicular skeleton:

  • Pectoral girdles: Clavicle (2) and Scapula (2).
  • Upper extremities (60): Humerus, Ulna, Radius, Carpals, Metacarpals, Phalanges.
  • Pelvic girdles: Hip bones (2).
  • Lower extremities (60): Femur, Fibula, Tibia, Patella, Tarsals, Metatarsals, Phalanges.

Structural Classification

• Macroscopic classification:
  • Compact bone: Dense, forms cortex of long bones, adapted to bending and twisting forces.
  • Cancellous bone (spongy bone): Open in texture, made of trabeculae, adapted to compressive forces.
• Microscopic classification:
  • Lamellar bone: Composed of thin plates of bony lamellae, made up of collagen fibers and mineral salts; found in most mature bones.
  • Fibrous bone: Found in young fetal bones, and common in reptiles and amphibians.
  • Dentine: Found in teeth.
  • Cement: Found in teeth.

Gross Structure of an Adult Long Bone

• Shaft (diaphysis): Consists of periosteum, cortex (compact bone), and medullary cavity.
  • Periosteum: Thick fibrous membrane covering the bone, comprising an outer fibrous layer and an inner cellular (osteogenic) layer, rich in blood supply, and with pain receptors.
  • Cortex: Composed of compact bone.
• Medullary cavity: Filled with red bone marrow (active in hematopoiesis) in young individuals; replaced by yellow bone marrow (fatty) later in life.
• Two ends (epiphyses): Composed of cancellous bone (spongy bone) covered by hyaline cartilage.

Functions of Periosteum

• Provides attachment for muscles, tendons, and ligaments.
• Contains a rich blood supply (nutritive function).
• Its inner cellular layer is osteogenic, facilitating bone formation when needed.
• Protects bone tissue by acting as a limiting membrane preventing spills into surrounding tissues.

Bony Landmarks (Axial and Appendicular Skeleton)

• Protuberances
• Sutures
• Notches
• Margins
• Foramina
• Processes
• Fossae
• Tuberosities
• Tubercles
• Grooves
• Sulci
• Cretas

Joints

• Junction between two or more bones or cartilages that allows movement and holds the skeleton together.
• Types of joints:
  • Synarthrosis: Immovable (sutures, gomphoses, synchondroses).
  • Amphiarthrosis: Slightly movable (syndesmoses, symphyses).
  • Diarthrosis: Freely movable (synovial).

Classification of Joints (Structural)

• Fibrous: Bones joined by fibrous tissue (no joint cavity); most are immovable.
• Cartilaginous: Bones joined by cartilage (no or limited joint cavity).
• Synovial: Contains a fluid-filled joint cavity; most are freely movable.

Osteogenesis

• Bone formation (osteogenesis) occurs via two methods:
• Intramembranous ossification: Bone forms within a membrane.
• Endochondral ossification: Bone forms within a cartilage model.

Types of Bone Cells

• Osteoblasts (bone-forming cells, responsible for building bone).
• Osteocytes (mature bone cells, maintain the bone tissue).
• Osteoclasts (bone-resorbing cells).

Bone Formation and Remodeling

• Two major phases of ossification in long bones:

  • Osteoblasts multiply and replace cartilage with bone.
  • Cartilage within the diaphysis is digested, creating the medullary cavity.

• Bone growth and lengthening: Cartilage is continuously formed by chondrocytes in the epiphyseal plates.

• Bone growth and width (appositional growth): Controlled by growth hormones; epiphyseal plates are converted to bone during adolescence.

• Remodeling occurs throughout life, responding to blood calcium levels and the pull of gravity and muscles on the skeleton.

Bone Fractures

• Fractures treated via reduction (manual coaxing into position by hands; surgically secured with pins, screws, or wires) and immobilization.
• Steps of fracture repair: Hematoma formation, fibrocartilage callus formation, bony callus formation, bone remodeling.

Functional Classification of Joints

• Synarthrosis: Immovable joints (Sutures, Gomphoses, Synchondroses)
• Amphiarthrosis: Slightly movable joints (Syndemoses, Symphyses)
• Diarthrosis: Freely movable joints (Synovial)

Test your knowledge on the skeletal system with this quiz covering topics such as bone classification, functions of bones, and joint types. Evaluate your understanding of both axial and appendicular skeleton components. Perfect for students studying anatomy and physiology.