Exam 3 Review: Bones, Skeleton, and Joints (Chapters 6-8)

Chapter 6: Bones and Bone Structure

Functions of the Skeletal System

The skeletal system provides the structural framework for the body and serves several essential functions:

• Support: Maintains body shape and supports soft tissues.

• Protection: Shields vital organs (e.g., brain, heart, lungs).

• Movement: Acts as levers for muscles to produce movement.

• Mineral Storage: Stores calcium and phosphate ions.

• Blood Cell Production: Houses red bone marrow for hematopoiesis.

• Fat Storage: Yellow bone marrow stores lipids.

Classification of Bones and Examples

Bones are classified by shape and function:

• Long Bones: e.g., femur, humerus

• Short Bones: e.g., carpals, tarsals

• Flat Bones: e.g., skull, ribs, sternum

• Irregular Bones: e.g., vertebrae, facial bones

• Sesamoid Bones: e.g., patella

Bone Cells: Types and Functions

• Osteogenic Cells: Stem cells that differentiate into osteoblasts.

• Osteoblasts: Bone-forming cells; synthesize bone matrix.

• Osteocytes: Mature bone cells; maintain bone tissue.

• Osteoclasts: Bone-resorbing cells; break down bone matrix.

Bone Matrix Composition

• Collagen Fibers: Provide flexibility; constitute about 1/3 of bone weight.

• Calcium Phosphate: Provides strength; constitutes about 2/3 of bone weight.

Osteon Structure

The osteon (Haversian system) is the basic functional unit of compact bone, consisting of concentric lamellae surrounding a central canal.

Long Bones: Structure and Components

• Compact Bone: Dense outer layer.

• Spongy Bone: Inner, porous layer.

• Medullary Cavity: Contains red (hematopoietic) and yellow (fat-storing) bone marrow.

• Periosteum: Membrane surrounding bone; aids in growth and repair.

• Blood Supply: Essential for bone growth and maintenance.

Types of Bone Growth

• Appositional Growth: Increase in bone diameter by adding new layers to the surface.

• Endochondral Ossification: Bone develops from cartilage model; most bones form this way.

• Intramembranous Ossification: Bone develops directly from mesenchymal tissue; forms flat bones.

Abnormalities of Bone Growth and Development

• Pituitary Growth Failure: Reduced growth hormone; short stature.

• Achondroplasia: Defective cartilage growth; dwarfism.

• Clubfoot: Deformity of foot and ankle.

• Gigantism: Excess growth hormone; abnormal height.

• Acromegaly: Excess growth hormone in adults; enlarged bones.

• Fibrodysplasia Ossificans Progressiva: Soft tissues turn into bone.

Fracture Types and Repair

• Transverse: Straight across the bone.

• Spiral: Twisting force; displaced.

• Greenstick: Incomplete break; common in children.

• Compression: Bone crushed; often vertebrae.

• Comminuted: Bone fragments into several pieces.

• Epiphyseal: Involves growth plate.

• Pott’s: Ankle fracture.

• Colles: Distal radius fracture.

Fracture repair involves four steps: hematoma formation, fibrocartilaginous callus formation, bony callus formation, and bone remodeling.

Calcium Regulation

• Calcium: Most abundant mineral in the body; essential for bone strength and physiological functions.

• Parathyroid Hormone (PTH): Increases blood calcium levels by stimulating osteoclasts.

• Calcitonin: Lowers blood calcium levels by inhibiting osteoclasts and promoting calcium deposition in bone.

Chapter 7: The Skeleton

Bone Numbers and Classification

• Total Bones: 206 in adult human body.

• Axial Skeleton: 80 bones; includes skull, vertebral column, and thoracic cage.

• Appendicular Skeleton: 126 bones; includes limbs, pectoral and pelvic girdles.

Names of Bones and Their Locations

• Carpal Bones: Wrist

• Tarsal Bones: Ankle

• Vertebrae: Spine

• Facial Bones: Face

• Other Examples: Sternum (chest), femur (thigh), scapula (shoulder)

Functions of the Axial Skeleton

• Support: Maintains posture and supports head and trunk.

• Protection: Protects brain, spinal cord, and thoracic organs.

Sinuses and Their Functions

• Sinuses: Air-filled cavities in skull bones (e.g., frontal, maxillary, sphenoid, ethmoid).

• Function: Lighten skull, produce mucus, and enhance voice resonance.

Foramen of the Skull

• Foramen: Openings in bones for nerves and blood vessels (e.g., foramen magnum, optic foramen).

• Function: Allow passage of neurovascular structures.

Curves of the Spinal Column

• Cervical Curve: Secondary; develops after birth.

• Thoracic Curve: Primary; present at birth.

• Lumbar Curve: Secondary; develops after birth.

• Sacral Curve: Primary; present at birth.

Parts of the Vertebral Bone

• Spinous Process: Posterior projection.

• Pedicles: Connect body to arch.

• Transverse Process: Lateral projections.

• Vertebral Body: Main weight-bearing portion.

• Vertebral Foramen: Opening for spinal cord.

Thoracic Cage (Chest) Components

• Vertebrosternal Ribs: True ribs; attach directly to sternum.

• Vertebrochondral Ribs: False ribs; attach indirectly via cartilage.

• Vertebral Ribs: Floating ribs; no anterior attachment.

• Manubrium: Upper part of sternum.

• Sternum Body: Middle part of sternum.

• Xiphoid Process: Inferior tip of sternum.

• Jugular Notch: Superior border of manubrium.

Chapter 8: Joints

Basic Types of Joints and Their Motions

Joints (articulations) connect bones and allow movement. Types include:

• Plane (Gliding) Joint: Sliding movements (e.g., intercarpal joints).

• Hinge Joint: Flexion and extension (e.g., elbow, knee).

• Pivot Joint: Rotation (e.g., atlantoaxial joint).

• Condyloid Joint: Flexion, extension, abduction, adduction (e.g., wrist).

• Saddle Joint: Similar to condyloid, but greater range (e.g., thumb).

• Ball and Socket Joint: Multiaxial movement (e.g., shoulder, hip).

Specific Joints and Articulating Bones

• Sacro-iliac Joint: Sacrum and ilium.

• Sterno-clavicular Joint: Sternum and clavicle.

• Other Examples: Knee (femur and tibia), elbow (humerus and ulna).

Classifications of Joints

Joints are classified functionally and structurally:

• Functional Classification:

  • Synarthrosis: Immovable (e.g., sutures).

  • Amphiarthrosis: Slightly movable (e.g., pubic symphysis).

  • Diarthrosis: Freely movable (e.g., synovial joints).

• Structural Classification:

  • Fibrous: Connected by fibrous tissue (e.g., sutures).

  • Cartilaginous: Connected by cartilage (e.g., intervertebral discs).

  • Bony: Fused bone (e.g., epiphyseal lines).

  • Synovial: Joint cavity with synovial fluid (e.g., knee).

Dislocation: Nursemaid’s Elbow

• Dislocation: Bones forced out of alignment.

• Nursemaid’s Elbow: Common in children; radial head dislocation.

• Most Commonly Dislocated Joint: Diarthrosis (ball and socket).

Types of Synovial Joints

• Plane

• Hinge

• Pivot

• Condyloid

• Saddle

• Ball and Socket

Movements of Joints

• Flexion/Extension: Decrease/increase angle between bones.

• Hyperextension: Extension beyond normal range.

• Dorsiflexion/Plantar Flexion: Upward/downward movement of foot.

• Abduction/Adduction: Move limb away/toward midline.

• Circumduction: Circular movement.

• Rotation: Bone turns around its axis.

• Pronation/Supination: Palm down/up.

• Opposition: Thumb touches fingers.

• Depression/Elevation: Lower/raise body part.

• Inversion/Eversion: Sole of foot turns inward/outward.

Arthritis and Artificial Joints

• Rheumatism: General term for pain and stiffness in joints.

• Arthritis: Inflammation of joints.

• Osteoarthritis (Degenerative Joint Disease, DJD): Most common; wear and tear.

• Artificial Joints: Prosthetic replacements for damaged joints.

Table: Joint Classifications

Classification	Type	Example	Movement
Functional	Synarthrosis	Sutures	Immovable
Functional	Amphiarthrosis	Pubic symphysis	Slightly movable
Functional	Diarthrosis	Knee, shoulder	Freely movable
Structural	Fibrous	Sutures	Immovable
Structural	Cartilaginous	Intervertebral discs	Slightly movable
Structural	Bony	Epiphyseal lines	Immovable
Structural	Synovial	Knee, shoulder	Freely movable

Example: The knee joint is a synovial, diarthrotic, hinge joint allowing flexion and extension.