Unit 3 Study Guide: Bones, Joints, and Muscles in Anatomy & Physiology

Chapter 6: Bones and Bone Tissue

General Functions of Bone

• Support: Bones provide a structural framework for the body and support soft tissues.

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

• Movement: Bones act as levers for muscles to produce movement.

• Mineral Storage: Bones store minerals, especially calcium and phosphorus, and release them into the blood as needed.

• Blood Cell Production: Hemopoiesis occurs in red bone marrow, producing red and white blood cells and platelets.

• Triglyceride Storage: Yellow bone marrow stores fat as an energy reserve.

Classification of Bones by Shape

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

• Short Bones: Nearly equal in length and width; e.g., carpals, tarsals.

• Flat Bones: Thin and often curved; e.g., sternum, ribs, scapulae.

• Irregular Bones: Complex shapes; e.g., vertebrae, some facial bones.

• Sesamoid Bones: Small, round, and embedded in tendons; e.g., patella.

Structural Components of a Long Bone

• Diaphysis: Shaft of the bone.

• Epiphyses: Ends of the bone, often wider than the shaft.

• Metaphysis: Region between diaphysis and epiphysis; contains the epiphyseal plate (growth plate) in growing bones.

• Medullary Cavity: Central cavity containing bone marrow.

• Periosteum: Dense connective tissue covering the outer surface of bone.

• Endosteum: Thin membrane lining the medullary cavity.

Differences Among Bone Types

• Long Bones: Have a shaft and two ends; primarily compact bone.

• Short, Flat, Irregular Bones: Thin layers of compact bone surrounding spongy bone; no shaft or marrow cavity.

Compact vs. Spongy Bone

• Compact Bone: Dense, forms the outer layer; composed of osteons (Haversian systems).

• Spongy Bone: Porous, found at ends of long bones and inside flat bones; composed of trabeculae.

Bone Marrow

• Red Marrow: Site of hemopoiesis (blood cell formation).

• Yellow Marrow: Stores fat; found in the medullary cavity of adults.

Hemopoiesis: The process of blood cell production in red bone marrow.

Composition of Bone Extracellular Matrix (ECM)

• Organic Component: Collagen fibers provide flexibility and tensile strength.

• Inorganic Component: Hydroxyapatite (calcium phosphate crystals) provides hardness.

Types of Bone Cells

• Osteogenic Cells: Stem cells that differentiate into osteoblasts.

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

• Osteocytes: Mature bone cells; maintain bone tissue.

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

Structure of Compact Bone

• Lamellae: Concentric rings of bone matrix.

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

• Lacunae: Small spaces housing osteocytes.

• Canaliculi: Tiny channels connecting lacunae for nutrient/waste exchange.

Bone Growth and Ossification

• Longitudinal Growth: Occurs at the epiphyseal plate; increases bone length.

• Intramembranous Ossification: Bone develops from a fibrous membrane; forms flat bones (e.g., skull, clavicle).

• Endochondral Ossification: Bone forms by replacing hyaline cartilage; forms most bones of the body.

Steps of Intramembranous Ossification

1. Ossification centers form within thickened regions of mesenchyme.

2. Osteoid is secreted and calcifies.

3. Woven bone and periosteum form.

4. Lamellar bone replaces woven bone; compact and spongy bone form.

Steps of Endochondral Ossification

1. Formation of bone collar around hyaline cartilage model.

2. Cavitation of the hyaline cartilage within the model.

3. Invasion of internal cavities by the periosteal bud and spongy bone formation.

4. Formation of the medullary cavity; appearance of secondary ossification centers.

5. Ossification of epiphyses; hyaline cartilage remains only in the epiphyseal plates and articular cartilages.

Bone Growth & Remodeling

• Interstitial Growth: Growth in length at the epiphyseal plate; involves five zones (resting, proliferative, hypertrophic, calcification, ossification).

• Appositional Growth: Growth in thickness by addition of bone to the surface.

• Bone Remodeling: Ongoing replacement of old bone by new bone tissue; influenced by hormones, mechanical stress, and dietary factors.

Blood Calcium Regulation

• Maintained by hormones such as parathyroid hormone (PTH) and calcitonin.

• Essential for nerve impulse transmission, muscle contraction, and blood clotting.

Fractures and Repair

• Basic Fracture Types: Simple, compound, comminuted, greenstick, spiral, etc.

• Fracture Repair Steps:

  1. Hematoma formation

  2. Fibrocartilaginous callus formation

  3. Bony callus formation

  4. Bone remodeling

Chapter 7: The Skeletal System

Axial vs. Appendicular Skeleton

• Axial Skeleton: Skull, vertebral column, and thoracic cage.

• Appendicular Skeleton: Limbs and girdles (pectoral and pelvic).

Anatomic Terms for Bone Features

• Terms such as foramen, process, condyle, fossa, etc., describe bone landmarks.

Sutures and the Fetal Skull

• Sutures: Immovable joints between skull bones.

• Fontanels: Soft spots in the fetal skull that allow for growth and flexibility during birth.

Paranasal Sinuses

• Air-filled spaces that lighten the skull and enhance voice resonance.

• Found in the frontal, ethmoid, sphenoid, and maxillary bones.

Hyoid Bone

• U-shaped bone in the neck; supports the tongue and aids in swallowing.

Vertebrae and Spinal Curves

• Types of Vertebrae: Cervical (7), thoracic (12), lumbar (5), sacral (5 fused), coccygeal (4 fused).

• Spinal Curves: Primary (thoracic, sacral) and secondary (cervical, lumbar).

• Abnormalities: Scoliosis (lateral curve), kyphosis (excessive thoracic curve), lordosis (excessive lumbar curve).

Intervertebral Discs

• Annulus Fibrosus: Outer ring of fibrocartilage.

• Nucleus Pulposus: Gel-like center; herniation occurs when this protrudes through the annulus.

Ribs and Sternum

• Types of Ribs: True (1-7), false (8-12), floating (11-12).

• Sternum Parts: Manubrium, body, xiphoid process.

Upper vs. Lower Limbs

• Both have similar structural patterns (single proximal bone, paired distal bones, wrist/ankle, digits), but differ in function and robustness.

Limb Bud Formation

• Limb buds form during embryonic development as outgrowths from the body wall.

Chapter 8: Articulations

Functional Classifications of Joints

• Synarthrosis: Immovable joints.

• Amphiarthrosis: Slightly movable joints.

• Diarthrosis: Freely movable joints.

Structural Classifications of Joints

• Fibrous Joints: Bones joined by dense connective tissue; e.g., sutures, gomphoses, syndesmoses.

• Cartilaginous Joints: Bones joined by cartilage; e.g., synchondroses (hyaline cartilage), symphyses (fibrocartilage).

• Synovial Joints: Bones separated by a fluid-filled cavity; most movable type.

Synovial Joint Structure

• Articular cartilage, joint (synovial) cavity, articular capsule, synovial fluid, reinforcing ligaments, nerves, and blood vessels.

Types of Arthritis

• Osteoarthritis, rheumatoid arthritis, gouty arthritis.

Joint Movements

• Gliding: Flat surfaces slide past each other (e.g., intercarpal joints).

• Angular: Flexion, extension, abduction, adduction, circumduction.

• Rotational: Rotation around a longitudinal axis (e.g., atlas and axis).

• Special Movements: Opposition/reposition (thumb), depression/elevation (jaw), protraction/retraction (scapula), inversion/eversion (foot), dorsiflexion/plantarflexion (ankle), supination/pronation (forearm).

Types of Synovial Joints and Examples

Type	Example
Plane	Intercarpal joints
Hinge	Elbow, knee
Pivot	Atlantoaxial joint
Condylar	Metacarpophalangeal joints
Saddle	Thumb (carpometacarpal joint)
Ball-and-socket	Shoulder, hip

Chapter 9: The Muscular System

Gross Anatomy of Muscle

• Fascicle: Bundle of muscle fibers.

• Tendon: Connects muscle to bone.

• Fascia: Connective tissue surrounding muscles.

• Epimysium: Surrounds entire muscle.

• Perimysium: Surrounds fascicles.

• Endomysium: Surrounds individual muscle fibers.

Muscle Shapes and Fiber Arrangement

• Parallel: Fibers run parallel to long axis (e.g., sartorius).

• Convergent: Broad origin, fibers converge to a single tendon (e.g., pectoralis major).

• Pennate: Short fibers attach obliquely to a central tendon (e.g., rectus femoris).

• Circular: Fibers arranged in concentric rings (e.g., orbicularis oris).

• Fusiform: Spindle-shaped with expanded belly (e.g., biceps brachii).

Functions of Skeletal Muscles

• Agonist (Prime Mover): Main muscle responsible for movement.

• Antagonist: Opposes the action of the agonist.

• Synergist: Assists the agonist.

• Origin: Attachment to stationary bone.

• Insertion: Attachment to movable bone.

Lever Systems

• First-class: Fulcrum between effort and load (e.g., neck extension).

• Second-class: Load between fulcrum and effort (e.g., standing on tiptoe).

• Third-class: Effort between fulcrum and load (e.g., biceps curl).

Muscle Naming

• Based on location, shape, size, direction of fibers, number of origins, location of attachments, and action.

Chapter 10: Muscle Tissue and Physiology

Types of Muscle Tissue

• Skeletal Muscle: Voluntary, striated, multinucleated.

• Cardiac Muscle: Involuntary, striated, branched, intercalated discs.

• Smooth Muscle: Involuntary, non-striated, spindle-shaped cells.

Properties of Muscle Cells

• Excitability, contractility, extensibility, elasticity.

Structure of Muscle

• Sarcoplasm: Cytoplasm of muscle cell.

• Sarcolemma: Plasma membrane of muscle cell.

• Myofibrils: Rod-like contractile elements.

• Sarcoplasmic Reticulum: Stores calcium ions.

Structure of Skeletal Muscle Fiber

• Multinucleated due to fusion of myoblasts during development.

Myofibrils and Myofilaments

• Thick Filaments: Composed of myosin.

• Thin Filaments: Composed of actin, troponin, and tropomyosin.

• Sarcomere: Functional unit; contains A band, I band, H zone, M line, Z disc.

Sliding Filament Mechanism

• Muscle contraction occurs as myosin heads bind to actin and pull thin filaments toward the center of the sarcomere.

Excitability and Action Potentials

• Resting membrane potential is maintained by ion gradients.

• Action potentials are rapid changes in membrane potential that trigger contraction.

Neuromuscular Junction

• Axon Terminal: Releases neurotransmitter (acetylcholine).

• Synaptic Cleft: Space between neuron and muscle fiber.

• Motor End Plate: Region of sarcolemma with acetylcholine receptors.

Events of Muscle Contraction and Relaxation

• Excitation: Action potential arrives at neuromuscular junction.

• Excitation-Contraction Coupling: Action potential triggers calcium release from sarcoplasmic reticulum.

• Crossbridge Cycling: Myosin heads bind to actin, perform power stroke, detach, and reset.

• Relaxation: Calcium is pumped back into sarcoplasmic reticulum, muscle returns to resting state.

Energy Sources for Muscle Contraction

• Immediate: Creatine phosphate.

• Glycolytic: Anaerobic glycolysis.

• Oxidative: Aerobic respiration.

Muscle Twitch and Contraction Types

• Muscle Twitch: Single contraction in response to a single stimulus; consists of latent, contraction, and relaxation periods.

• Tetanus: Sustained contraction from rapid stimuli.

• Wave Summation: Increased force with repeated stimulation.

• Length-Tension Relationship: Optimal sarcomere length produces maximal tension.

Types of Skeletal Muscle Fibers

• Type I (Slow-twitch): Fatigue-resistant, aerobic.

• Type II (Fast-twitch): Fatigue quickly, anaerobic.

Motor Units and Muscle Tone

• Motor Unit: One motor neuron and all the muscle fibers it innervates.

• Recruitment: Increasing the number of active motor units increases force.

• Muscle Tone: Continuous, partial contraction of muscles.

Isometric and Isotonic Contractions

• Isometric: Muscle length does not change (e.g., holding a weight steady).

• Isotonic: Muscle changes length (concentric: shortens; eccentric: lengthens).

Skeletal Muscle Performance

• Endurance Training: Increases oxidative capacity.

• Resistance Training: Increases muscle size and strength.

• Disuse: Leads to atrophy.

Muscular Fatigue and EPOC

• Muscular Fatigue: Inability to maintain contraction; caused by ATP depletion, lactic acid buildup, etc.

• Excess Postexercise Oxygen Consumption (EPOC): Increased oxygen intake after exercise to restore metabolic conditions.

Smooth and Cardiac Muscle

• Smooth Muscle: Found in walls of hollow organs; contracts via sliding filament mechanism; regulated by autonomic nervous system.

• Cardiac Muscle: Found only in the heart; contains intercalated discs for synchronized contraction; autorhythmic (can generate its own action potentials).