Anatomy & Physiology Study Guide: Skeletal System, Articulations, and Muscular System

Chapter 6: Skeletal System

Components and Functions of the Skeletal System

The skeletal system provides the structural framework for the body, protects vital organs, and facilitates movement. It also serves as a reservoir for minerals and is involved in blood cell production.

• Main Components: Bones, cartilage, ligaments, and joints.

• Bony Tissue: Also known as osseous tissue.

• Functions:

  • Support and shape for the body

  • Protection of internal organs (e.g., skull protects brain, rib cage protects heart and lungs)

  • Movement (attachment points for muscles)

  • Mineral storage (calcium and phosphate)

  • Blood cell production (hematopoiesis in bone marrow)

• Types of Bone: Six types: long, short, flat, irregular, sesamoid, and sutural bones.

• Bone Marrow: Yellow marrow (fat storage) and red marrow (hematopoiesis).

Structure of Bone

Bones are composed of compact and spongy tissue, each with distinct functions and locations.

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

• Spongy Bone (Cancellous): Porous, found at the ends of long bones and inside flat bones; contains trabeculae.

• Microscopic Anatomy:

  • Osteon (Haversian system): Structural unit of compact bone.

  • Trabeculae: Lattice-like network in spongy bone.

  • one Cells: Osteoblasts (build bone), osteocytes (maintain bone), osteoclasts (break down bone).

Bone Development and Growth

Bone formation occurs through ossification, which can be intramembranous or endochondral.

• Intramembranous Ossification: Direct formation of bone from mesenchymal tissue (e.g., flat bones of the skull).

• Endochondral Ossification: Bone develops by replacing hyaline cartilage (e.g., long bones).

• Growth Plates (Epiphyseal Plates): Regions of growing cartilage in children; damage can affect bone growth.

Bone Composition and Homeostasis

Bones are composed of organic and inorganic materials, and their mass is regulated by cellular activity and hormones.

• Organic Matrix: Collagen fibers provide flexibility.

• Inorganic Matrix: Hydroxyapatite (calcium phosphate) provides strength.

• Hormonal Regulation:

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

  • Calcitonin: Lowers blood calcium by inhibiting osteoclasts.

  • Vitamin D: Promotes calcium absorption.

• Bone Remodeling: Continuous process of bone resorption and deposition.

Hematopoiesis and Bone Disorders

Bone marrow is the site of blood cell formation, and bones can be affected by various disorders.

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

• Bone Disorders:

  • Osteoporosis: Reduced bone mass, increased fracture risk.

  • Osteomalacia/Rickets: Softening of bones due to vitamin D deficiency.

  • Spina bifida: Congenital defect of the spine.

Chapter 8: Articulations

Joint Structure and Classification

Joints, or articulations, are points where two bones meet, allowing for movement and flexibility.

• Types of Joints:

  • Fibrous Joints: Bones joined by dense connective tissue; little to no movement (e.g., sutures in skull).

  • Cartilaginous Joints: Bones joined by cartilage; limited movement (e.g., intervertebral discs).

  • Synovial Joints: Freely movable; characterized by a joint cavity filled with synovial fluid (e.g., knee, shoulder).

• Functional Classification: Synarthroses (immovable), amphiarthroses (slightly movable), diarthroses (freely movable).

• Examples: Gomphosis (tooth socket), symphysis (pubic symphysis), glenohumeral (shoulder) joint.

Joint Movements and Disorders

Joints allow for various types of movement and can be affected by injuries and disorders.

• Types of Movement: Flexion, extension, abduction, adduction, rotation, circumduction.

• Ligaments: Connect bone to bone; stabilize joints.

• Common Disorders: Sprain (ligament injury), dislocation (bone displacement), bursitis (inflammation of bursa), tendinitis (inflammation of tendon).

Chapter 10: Muscular System

Types and Functions of Muscle Tissue

Muscle tissue is specialized for contraction and movement. There are three main types, each with unique characteristics and functions.

• Skeletal Muscle: Voluntary, striated, attached to bones; responsible for body movement.

• Cardiac Muscle: Involuntary, striated, found in the heart; responsible for pumping blood.

• Smooth Muscle: Involuntary, non-striated, found in walls of hollow organs; controls movement of substances.

• Muscle Similarities/Differences: Skeletal and cardiac are striated; smooth is not. Cardiac and smooth are involuntary.

Muscle Structure and Contraction

Muscle contraction is a complex process involving the interaction of proteins and cellular structures.

• Organization: Muscle → fascicle → muscle fiber → myofibril → sarcomere.

• Sarcomere: Functional unit of muscle contraction; contains actin and myosin filaments.

• Sarcoplasmic Reticulum (SR): Stores and releases calcium ions for contraction.

• Neuromuscular Junction: Site where motor neuron communicates with muscle fiber; releases acetylcholine (ACh).

• Sliding Filament Theory: Muscle contraction occurs as actin and myosin filaments slide past each other.

Mechanisms of Muscle Contraction

Muscle contraction is regulated by electrical and chemical signals, and involves several phases.

• Excitation-Contraction Coupling: Sequence from nerve impulse to muscle contraction.

• ATP Sources: Creatine phosphate (CP), anaerobic glycolysis, aerobic respiration.

• Action Potential: Electrical signal that triggers contraction.

• Resting Membrane Potential (RMP): Difference in charge across the muscle cell membrane.

• Phases of Contraction: Latent period, contraction phase, relaxation phase.

• Summation and Tetany: Increased frequency of stimulation leads to stronger contractions.

• Muscle Fatigue: Decrease in muscle strength due to prolonged activity.

Types of Muscle Contractions and Arrangements

Muscles contract in different ways and are arranged to optimize force and movement.

• Contraction Types: Isometric (no change in length), isotonic (change in length), concentric (shortening), eccentric (lengthening).

• Muscle Fiber Types:

  • Type I (slow-twitch): Endurance, fatigue-resistant.

  • Type II (fast-twitch): Quick, powerful contractions, fatigue quickly.

• Muscle Arrangements: Parallel, pennate, convergent, circular.

Compartment Syndrome

Compartment syndrome is a condition where increased pressure within a muscle compartment impairs blood flow and nerve function.

• Symptoms: Pain, numbness, decreased function.

• Treatment: Surgical intervention to relieve pressure.

Key Tables

Classification of Joints

Type	Structural Classification	Functional Classification	Example
Fibrous	Dense connective tissue	Synarthrosis (immovable)	Sutures of skull
Cartilaginous	Cartilage	Amphiarthrosis (slightly movable)	Intervertebral discs
Synovial	Joint cavity with synovial fluid	Diarthrosis (freely movable)	Knee, shoulder

Types of Muscle Fibers

Type	Contraction Speed	Fatigue Resistance	Example
Type I (Slow-twitch)	Slow	High	Postural muscles
Type II (Fast-twitch)	Fast	Low	Eye muscles, sprinting muscles

Key Equations

• Bone Mass Balance: $\text{Bone Mass} = \text{Bone Formation} - \text{Bone Resorption}$

• ATP Production in Muscle: $\text{ATP}_{\text{total}} = \text{ATP}_{\text{CP}} + \text{ATP}_{\text{anaerobic}} + \text{ATP}_{\text{aerobic}}$

• Resting Membrane Potential: $\text{RMP} = \text{Potential}_{\text{inside}} - \text{Potential}_{\text{outside}}$

Additional info:

• Some content was inferred and expanded for clarity and completeness, such as definitions and examples of bone and muscle types, and the inclusion of tables for joint and muscle fiber classification.

• Clinical applications and disorders were summarized based on standard Anatomy & Physiology curriculum.