Body systems

A. Structure and Functions of the Skeletal System

i. Role of the Skeletal System

The skeletal system provides:

  • Support: Maintains body shape and posture.

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

  • Movement: Works with muscles and joints to allow motion.

  • Blood Cell Production: Red and white blood cells are produced in bone marrow.

  • Mineral Storage: Stores calcium and phosphorus for bone strength and metabolic functions.

ii. Types of Bones and Joints

Types of Bones:

  1. Long Bones – Aid movement and support weight (e.g., femur, humerus).

  2. Short Bones – Provide stability and shock absorption (e.g., carpals, tarsals).

  3. Flat Bones – Protect organs and serve as attachment sites for muscles (e.g., skull, ribs).

  4. Irregular Bones – Have complex shapes for specific functions (e.g., vertebrae).

  5. Sesamoid Bones – Reduce friction and pressure in tendons (e.g., patella).

Types of Joints:

  • Fixed (Fibrous) Joints – No movement (e.g., skull sutures).

  • Cartilaginous Joints – Limited movement (e.g., vertebrae).

  • Synovial Joints – Free movement (e.g., knee, elbow).

Types of Synovial Joints:

  • Hinge – One direction (e.g., knee, elbow).

  • Ball and Socket – Multi-directional (e.g., shoulder, hip).

  • Pivot – Rotational movement (e.g., neck).

  • Gliding – Sliding movement (e.g., wrist, ankle).

  • Saddle – More flexibility than hinge (e.g., thumb).

  • Condyloid – Movement in two planes (e.g., wrist).

B. Structure and Functions of the Muscular System

i. Role of the Muscular System

  • Movement: Muscles contract to create movement with the skeletal system.

  • Posture: Supports body position.

  • Heat Production: Muscle activity generates heat to maintain body temperature.

  • Circulation: The heart (a muscle) pumps blood, and skeletal muscles assist venous return.

  • Digestion: Smooth muscles help move food through the digestive tract.

ii. Structure of Voluntary Muscles

  • Skeletal Muscle: Striated and under voluntary control (e.g., biceps, quadriceps).

  • Structure:

    • Muscle Fibers – Contain contractile proteins (actin and myosin).

    • Fascicles – Bundles of muscle fibers.

    • Tendons – Connect muscles to bones for movement.

C. Structure and Function of the Circulatory System

i. Role of the Circulatory System

  • Transports Oxygen & Nutrients: Delivers essential substances to cells.

  • Removes Waste Products: Carries carbon dioxide and other wastes away.

  • Regulates Body Temperature: Blood flow adjustments help maintain temperature.

  • Protects Against Infection: White blood cells fight pathogens.

ii. Major Components of the Circulatory System

  • Heart: Pumps blood throughout the body.

  • Blood Vessels:

    • Arteries – Carry oxygenated blood away from the heart.

    • Veins – Return deoxygenated blood to the heart.

    • Capillaries – Exchange oxygen, nutrients, and waste with tissues.

  • Blood:

    • Red Blood Cells – Carry oxygen.

    • White Blood Cells – Fight infections.

    • Platelets – Aid blood clotting.

    • Plasma – Transports substances.

D. Structure and Function of the Respiratory System

iii. Role of the Respiratory System

  • Gas Exchange: Oxygen intake and carbon dioxide removal.

  • Oxygen Supply: Provides oxygen for energy production in cells.

  • Speech Production: Airflow enables vocalization.

iv. Major Components of the Respiratory System

  • Nasal Cavity: Warms, filters, and humidifies air.

  • Pharynx & Larynx: Passageways for air; larynx contains vocal cords.

  • Trachea: Airway leading to lungs.

  • Bronchi & Bronchioles: Branch into the lungs for air distribution.

  • Alveoli: Tiny air sacs for gas exchange.

  • Diaphragm: Muscle that controls breathing.

v. Basic Contribution to Efficient Movement

  • Oxygen Supply: Fuels muscles for energy production.

  • Carbon Dioxide Removal: Prevents fatigue and maintains pH balance.

  • Endurance: Efficient breathing improves stamina and athletic performance.

E. Interrelationship Between Body Systems

vi. The Reliance of Body Systems on Each Other for Effective Functioning

  • Muscular & Circulatory System: Muscles require oxygen and nutrients from the blood; circulation removes waste.

  • Respiratory & Circulatory System: Oxygen enters the bloodstream via lungs; carbon dioxide is expelled.

  • Skeletal & Muscular System: Bones provide attachment points; muscles generate movement.

  • Nervous & Muscular System: The brain sends signals to muscles for coordination.

F. Movement Terminology

vii. Directional Terms

  • Anterior (Front) / Posterior (Back)

  • Superior (Above) / Inferior (Below)

  • Medial (Toward Midline) / Lateral (Away from Midline)

  • Proximal (Closer to Attachment Point) / Distal (Farther from Attachment Point)

  • Flexion (Decreasing Joint Angle) / Extension (Increasing Joint Angle)

  • Abduction (Moving Away from Midline) / Adduction (Moving Toward Midline)

viii. How Bones, Joints, and Muscles Interact to Produce Movement

  1. Flexing the Elbow During a Bicep Curl:

    • Bone: Humerus and radius/ulna.

    • Joint: Hinge joint at the elbow.

    • Muscle: Biceps contract (agonist), triceps relax (antagonist).

  2. Extending the Knee During Cycling:

    • Bone: Femur, tibia, patella.

    • Joint: Hinge joint at the knee.

    • Muscle: Quadriceps contract (agonist), hamstrings relax (antagonist