Skeletal System: Structure, Function, and Anatomy Study Guide

Skeletal System

I. General Functions of the Skeletal System

• Support: Provides structural framework for the body, supporting soft tissues and giving shape to the body.

• Protection: Shields vital organs (e.g., skull protects the brain, rib cage protects the heart and lungs).

• Movement: Acts as levers for muscles to pull on, facilitating movement.

• Mineral Storage: Stores minerals such as calcium and phosphorus, which can be released into the bloodstream as needed.

• Blood Cell Production: Houses red bone marrow, which produces blood cells (hematopoiesis).

• Triglyceride Storage: Stores fat in yellow bone marrow.

II. Cells of the Skeletal System (Structure/Function)

• Chondrocytes: Mature cartilage cells that maintain the cartilage matrix.

• Osteocytes: Mature bone cells responsible for maintaining bone tissue.

• Osteoblasts: Bone-forming cells that synthesize and secrete the bone matrix.

• Osteoclasts: Large cells that resorb or break down bone matrix.

• Stem Cells: Undifferentiated cells that can develop into osteoblasts or other cell types.

III. Tissues of the Skeletal System (Structure/Function/Location)

• Osseous Tissue: The primary tissue of bone, providing strength and support.

• Fibrocartilage: Found in intervertebral discs and menisci; resists compression and tension.

• Hyaline Cartilage: Covers articular surfaces of bones, supports respiratory structures, and forms the embryonic skeleton.

IV. Microscopic Anatomy of Bone (Structure/Function/Location)

• Osteon (Haversian System): The structural unit of compact bone, consisting of concentric lamellae around a central canal.

• Lamellae: Layers of bone matrix within an osteon.

• Canaliculi: Small channels connecting osteocytes, allowing for nutrient and waste exchange.

• Central Canal (Haversian Canal): Contains blood vessels and nerves.

• Lacunae: Small spaces housing osteocytes.

V. Bone Formation, Growth, and Fracture Repair

• Ossification: The process of bone formation. Two types:

  • Intramembranous Ossification: Forms flat bones (e.g., skull) directly from mesenchyme.

  • Endochondral Ossification: Forms most bones by replacing hyaline cartilage with bone.

• Growth: Bones grow in length at the epiphyseal plate and in thickness by appositional growth.

• Fracture Repair: Involves hematoma formation, fibrocartilaginous callus formation, bony callus formation, and bone remodeling.

• Hematopoiesis: Production of blood cells in red bone marrow.

• Factors Affecting Bone Health: Nutrition (calcium, vitamin D), hormones (growth hormone, sex hormones), and exercise.

VI. Long Bone Structure (Structure/Function/Location)

• Diaphysis: Shaft of a long bone, composed mainly of compact bone.

• Epiphysis: Ends of long bones, mostly spongy bone covered by articular cartilage.

• Epiphyseal Plate: Growth plate made of cartilage, site of bone lengthening during childhood.

• Periosteum: Dense connective tissue covering the bone's outer surface; contains osteoblasts and osteoclasts.

• Endosteum: Thin membrane lining the medullary cavity.

• Medullary Cavity: Central cavity containing yellow bone marrow (fat storage).

• Compact Bone: Dense outer layer providing strength.

• Spongy Bone: Porous bone tissue found in epiphyses; contains red marrow.

• Articular Cartilage: Hyaline cartilage covering joint surfaces for smooth movement.

• Sharpey's Fibers: Collagen fibers anchoring periosteum to bone.

• Volkmann's Canal: Transverse canals connecting blood vessels of periosteum and central canals.

VII. Bone Classification (How to Classify and Examples)

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

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

• Flat Bones: Thin, flattened, and usually curved (e.g., sternum, ribs, skull bones).

• Irregular Bones: Complex shapes (e.g., vertebrae, hip bones).

• Sesamoid Bones: Small, round bones embedded in tendons (e.g., patella).

VIII. Projections of Bones (Distinguish Each with Example and Location)

• Tuberosity: Large, rounded projection (e.g., tibial tuberosity).

• Crest: Narrow, prominent ridge (e.g., iliac crest).

• Trochanter: Large, blunt, irregular surface (e.g., greater trochanter of femur).

• Line: Narrow ridge (e.g., linea aspera of femur).

• Tubercle: Small, rounded projection (e.g., greater tubercle of humerus).

• Epicondyle: Raised area above a condyle (e.g., medial epicondyle of humerus).

• Spine: Sharp, slender projection (e.g., spine of scapula).

• Process: Any bony prominence (e.g., mastoid process of temporal bone).

• Head: Bony expansion on a narrow neck (e.g., head of femur).

• Facet: Smooth, nearly flat articular surface (e.g., articular facet of vertebra).

• Condyle: Rounded articular projection (e.g., condyles of femur).

• Ramus: Armlike bar of bone (e.g., ramus of mandible).

• Fossa: Shallow depression (e.g., olecranon fossa of humerus).

• Foramen: Round or oval opening (e.g., foramen magnum of skull).

• Meatus: Canal-like passageway (e.g., external acoustic meatus).

• Sinus: Cavity within a bone (e.g., maxillary sinus).

• Groove: Furrow (e.g., radial groove of humerus).

• Fissure: Narrow, slit-like opening (e.g., superior orbital fissure).

• Notch: Indentation at the edge of a structure (e.g., greater sciatic notch).

IX. Axial Skeleton Anatomy (Key Bones and Landmarks)

• Skull: Cranial and facial bones.

• Vertebral Column: Cervical, thoracic, and lumbar vertebrae.

• Thoracic Cage: Sternum, true ribs, false ribs, floating ribs.

X. Appendicular Skeleton Anatomy (Key Bones and Landmarks)

• Pectoral Girdle: Clavicle and scapula.

• Upper Limbs: Humerus, radius, ulna, carpals, metacarpals, phalanges.

• Pelvic Girdle: Hip bones (ilium, ischium, pubis).

• Lower Limbs: Femur, patella, tibia, fibula, tarsals, metatarsals, phalanges.

Additional info: This guide covers the structure, function, and anatomy of the skeletal system, including bone classification, microscopic anatomy, and key anatomical landmarks. It is suitable for exam preparation in a college-level Anatomy & Physiology course.