Skeletal and Muscular Systems: Study Guide for Anatomy & Physiology

Chapter 6: The Skeletal System

Basic Terminology and Bone Tissue Types

The skeletal system is composed of various types of bone tissue and anatomical structures. Understanding the terminology and classification of bone is essential for studying the human skeleton.

• Types of Bone Tissue:

  • Cancellous (Spongy) Bone: Porous bone found at the ends of long bones and in the interior of other bones. Contains red bone marrow.

  • Compact Bone: Dense, strong bone that forms the outer layer of bones, providing strength and protection.

• Functions of the Skeletal System: Support, protection, movement, mineral storage, and blood cell formation (hematopoiesis).

Bone Markings: Projections and Depressions

Bones have various markings that serve as attachment points for muscles, ligaments, and tendons, or as passageways for nerves and blood vessels.

• Projections: Raised areas such as crests, spines, and tubercles.

• Depressions: Indentations such as fossae, grooves, and notches.

• Openings: Foramina and canals for passage of nerves and vessels.

Cartilage in the Skeleton

Cartilage is a flexible connective tissue found in joints, the rib cage, ear, nose, bronchial tubes, and intervertebral discs.

• Types of Cartilage: Hyaline, elastic, and fibrocartilage.

• Function: Provides support, flexibility, and reduces friction in joints.

Gross Classification of Bones

Bones are classified by their shape and structure.

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

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

• Flat Bones: Thin and broad (e.g., sternum).

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

Bone Development (Ossification)

Ossification is the process of bone formation, which occurs through two main mechanisms.

• Intramembranous Ossification: Bone develops directly from mesenchymal tissue (e.g., flat bones of the skull).

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

Bone Growth and Remodeling

Bones grow in length and diameter during childhood and adolescence, and are continuously remodeled throughout life.

• Epiphyseal Plate (Growth Plate): Layer of cartilage where bone growth occurs in children and adolescents.

• Remodeling: Ongoing replacement of old bone tissue by new bone tissue, involving osteoclasts (bone resorption) and osteoblasts (bone formation).

Hormonal Control of Bone Growth

• Calcitonin: Hormone from the thyroid gland that lowers blood calcium levels by inhibiting bone resorption.

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

Wolff's Law

Wolff's Law states that bone grows and remodels in response to the forces placed upon it.

• Importance: Explains how physical activity and mechanical stress strengthen bones.

Osteoporosis

Osteoporosis is a condition characterized by decreased bone mass and increased risk of fractures.

• Causes: Aging, hormonal changes, lack of calcium or vitamin D.

• Treatment: Medications, dietary supplements, weight-bearing exercise.

Fractures

Fractures are breaks in bones that require specific steps for repair.

• Types of Fractures: Simple, compound, comminuted, greenstick, etc.

• Fracture Healing: Hematoma formation, fibrocartilaginous callus formation, bony callus formation, bone remodeling.

Chapter 7: The Axial Skeleton

Identification of Bones

The axial skeleton includes the bones of the skull, vertebral column, and thoracic cage.

• Major Bones: Skull, vertebrae, ribs, sternum.

Spinal Curvatures

The vertebral column has three abnormal curvatures that can affect posture and health.

• Scoliosis: Lateral curvature of the spine.

• Kyphosis: Exaggerated thoracic curvature (hunchback).

• Lordosis: Exaggerated lumbar curvature (swayback).

Chapter 8: Joints

Classification of Joints

Joints are classified by their structure and function.

• Structural Classification: Fibrous, cartilaginous, synovial.

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

Synovial Joints

• Characteristics: Joint cavity, articular cartilage, synovial fluid, joint capsule.

• Features: Bursae, tendon sheaths, stabilizing factors.

• Movements: Non-angular (gliding), angular (flexion, extension, abduction, adduction).

Homeostatic Imbalances in Joints

• Sprains: Ligament injury.

• Strains: Muscle or tendon injury.

• Arthritis: Inflammation of joints.

Aging and Development of Joints

• Effects of Aging: Decreased flexibility, increased risk of joint disorders.

• Normal Development: Joints form during embryonic development and mature through childhood.

Chapter 9: Muscle Tissue

Muscle Tissue Characteristics

Muscle tissue is specialized for contraction and movement.

• Types of Muscle Tissue:

  • Smooth: Involuntary, non-striated, found in walls of hollow organs.

  • Cardiac: Involuntary, striated, found only in the heart.

  • Skeletal: Voluntary, striated, attached to bones for movement.

Anatomy of Skeletal Muscle

• Gross Anatomy: Muscle belly, tendons, connective tissue coverings (epimysium, perimysium, endomysium).

• Microscopic Anatomy: Muscle fibers, myofibrils, myofilaments (actin and myosin), sarcomere structure, neuromuscular junction.

Physiology of Muscle

• Neurotransmitters: Acetylcholine is the primary neurotransmitter at the neuromuscular junction.

• Excitation-Contraction Coupling: Sequence of events from nerve signal to muscle contraction.

• Role of ATP and Calcium: ATP provides energy for contraction; calcium triggers contraction by binding to troponin.

ATP Synthesis in Muscle

• Methods: Creatine phosphate, anaerobic glycolysis, aerobic respiration.

• Rate-Limiting Steps: Steps that determine the speed of ATP production.

Muscle Contraction Types

• Isometric: Muscle tension without length change.

• Isotonic: Muscle changes length (concentric and eccentric contractions).

Types of Muscle Fibers

• Slow Oxidative: Fatigue-resistant, used for endurance.

• Fast Oxidative: Intermediate properties.

• Fast Glycolytic: Fatigue quickly, used for short bursts of power.

Homeostatic Imbalances in Muscle

• Muscle Fatigue: Inability to contract after prolonged activity.

• Muscle Cramps: Involuntary, painful contractions.

• Muscular Dystrophy: Group of genetic diseases causing muscle weakness.

Chapter 10: The Muscular System

Muscle Identification and Naming

• Identification: Recognize major muscles of the body by location and function.

• Naming: Muscles are named based on location, shape, size, direction of fibers, number of origins, and action.

Muscles that Provide Motion

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

• Antagonist: Opposes the action of the agonist.

• Synergist: Assists the agonist.

• Fixator: Stabilizes the origin of the agonist.

Aging and Development of Muscle

• Effects of Aging: Decreased muscle mass and strength, slower regeneration.

• Normal Development: Muscle fibers grow in size and number during childhood and adolescence.