Study Guide: Human Body - Physical Education (HKDSE) (copy) (copy)
A. Body Types and Basic Structures of Human Body
I. Somatotypes
Somatotyping: A system of classifying body types into three categories through a visual evaluation of body shapes.
Endomorphs: Individuals with a rounded body shape and a tendency to store fat.
Characteristics:
Wide hips and narrow shoulders
A lot of fat on the body
Quite slim wrists and ankles
Mesomorphs: Individuals who are more muscular and generally taller.
Characteristics:
Broad shoulders and narrow hips
Muscular body build
Strong forearms and thighs
Ectomorphs: Individuals who tend to be tall and thin.
Characteristics:
Narrow shoulders and hips
Thin legs and arms
Very little muscle or fat
II. Sports Examples
Various body types have different benefits on sports performance depending on limb lengths, height, weight, and body percentage:
Ectomorphic Athletes: Lighter body weight reduces loading during long-distance running.
Longer Limbs: May allow athletes longer strides.
Mesomorphic Athletes: Greater muscle mass provides agility, power, and muscle strength, particularly advantageous in sports like Handball.
Sumo Wrestling: Athletes with a body mass between endomorphic and mesomorphic classifications are at an advantage.
III. Body Mass Index (BMI)
Definition: One of the common indicators to describe body fatness.
Normal range for Asian adults: BMI between 18.5 and 22.9.
Calculation of BMI:
ext{BMI} = rac{ ext{Weight (in kilograms)}}{ ext{Height (in meters)} imes ext{Height (in meters)}}Usage: An inexpensive and easy-to-perform method to gauge body fat, though it cannot reflect the percentage body fat in one's composition.
Overweight and Obesity: Defined as a BMI exceeding the 91st percentile among students of the same sex and age group. For individuals aged 18 and above:
Overweight: BMI between 23 and 24.9
Obesity: BMI of 25 or above
BMI and Age for Overweight and Obesity:
| Age (years) | Male Overweight BMI | Male Obesity BMI | Female Overweight BMI | Female Obesity BMI |
|-------------|----------------------|-------------------|-----------------------|-------------------|
| 6 | 17.6 | 19.7 | 17.2 | 18.9 |
| 7 | 18.2 | 20.7 | 17.6 | 19.7 |
| 8 | 18.8 | 21.9 | 18.2 | 20.6 |
| 9 | 19.6 | 23.2 | 18.9 | 21.7 |
| 10 | 20.4 | 24.4 | 19.7 | 22.8 |
| 11 | 21.2 | 25.5 | 20.5 | 23.9 |
| 12 | 21.9 | 26.6 | 21.3 | 24.9 |
| 13 | 22.6 | 27.5 | 22.1 | 25.8 |
| 14 | 23.3 | 28.4 | 22.8 | 26.6 |
| 15 | 24.0 | 29.2 | 23.5 | 27.4 |
| 16 | 24.7 | 30.0 | 24.1 | 28.1 |
| 17 | 25.3 | 30.7 | 24.7 | 28.7 |Source: Hong Kong 2020 Growth References
IV. Weight for Height
The Department of Health defines:
Overweight as having a body weight exceeding 20% of the median (50th percentile) weight for height.
Underweight as having a body weight lower than 20% of the median weight for height.
Only suitable for children and adolescents aged 18 years or below with heights between 91-165cm (female) or 91-175 cm (male).
V. Body Composition
Refers to the relative compositions of fatty tissues, bones, muscles, and water in the body.
The School Physical Fitness Award Scheme defines optimal body fat ranges as:
Boys: 10.3% - 20.1%
Girls: 15% - 26.8%
Classification of Body Fat:
Level
Boys
Girls
Very Low
< 5.8% | < 12.1% | | Low | 5.9 - 10.2% | 12.2 - 14.9% | | Optimal | 10.3 - 20.1% | 15 - 26.8% | | Moderately High| 20.2 - 25.3% | 26.9 - 31.9% | | High | 25.4 - 30% | 32 - 35% | | Very High | > 30%
> 35%
VI. Basic Structures of Human Body
Cell: A living organism in its simplest form, capable of maintaining bodily functions by taking in nutrients and converting them to energy.
Examples: Muscle cells, fat cells.
Tissue: A collection of interconnected cells performing a similar function.
Examples: Adipose tissue, skeletal muscle, bone, blood.
Organ: A group of tissues performing one or more specific physiological functions.
Examples: Lungs, heart, blood vessels.
System: Groups of organs working together to carry out complex functions of the human body.
Examples: Skeletal system, nervous system, respiratory system.
VII. Major Systems in Human Body
Organ System and their Physiological Roles
Integumentary System: Covers the body and protects it. Components: Skin, hair, nails, and sweat glands.
Skeletal System: Protects the body and provides support for locomotion and movement. Components: Bones, cartilage, and ligaments.
Nervous System: Receives stimuli, integrates information, and directs the body. Components: Brain, spinal cord, nerves, and sense organs.
Endocrine System: Coordinates and integrates activities of the body. Components: Pituitary, adrenal, thyroid, and other ductless glands.
Muscular System: Produces body movement. Components: Skeletal muscle, smooth muscle, and cardiac muscle.
Digestive System: Absorbs soluble nutrients from ingested food. Components: Teeth, salivary glands, esophagus, stomach, intestines, liver, and pancreas.
Respiratory System: Collects oxygen and exchanges it for carbon dioxide. Components: Lungs, pharynx, trachea, and other air passageways.
Circulatory System: Transports cells and materials throughout the body. Components: Heart, blood vessels, blood, and lymph structures.
Immune System: Removes foreign chemicals and microorganisms from the bloodstream. Components: T-lymphocytes, B-lymphocytes and macrophages: lymph structures.
Urinary System: Removes metabolic wastes from the bloodstream. Components: Kidney, bladder, and associated ducts.
Reproductive System: Produces sex cells for the next generation. Components: Testes, ovaries, and associated reproductive structures.
B. Skeletal System
I. Functions of the Skeleton
The skeletal system consists of 206 bones and accounts for about 20% of body weight. The main functions include:
Support: Provides solid and rigid support to keep the body upright and withstand gravitational forces.
Movement: Serves as attachment surfaces for muscles and helps generate movement using leverage.
Protection: Protects internal organs including the brain, spinal cord, lungs, and heart.
Mineral Storage: Acts as a storage site for calcium and phosphorus.
Production: Red bone marrow in bone cavities produces red blood cells, white blood cells, and platelets.
II. Bones
A bone is a rigid, non-elastic tissue composed of 65% minerals and 35% organic tissue.
Bone Structure:
Surface and inner layers made of compact bone and cancellous bone respectively.
Compact Bone: The hard exterior layer.
Cancellous Bone: A spongy inner layer characterized by a criss-cross matrix.
Total Count: 206 bones of various shapes and sizes in adults.
Divisions:
Axial Skeleton: Comprised of the skull, vertebral column, and thoracic cage.
Appendicular Skeleton: Comprised of limbs and girdles of attachment.
III. Types of Bone
Long Bones: e.g., femur, humerus, tibia, radius.
Short Bones: e.g., carpals, tarsals.
Flat Bones: e.g., some skull bones.
Irregular Bones: e.g., vertebrae, pelvis.
IV. Vertebral Column
Divided into five major regions:
Cervical (7 vertebrae)
Thoracic (12 vertebrae)
Lumbar (5 vertebrae)
Sacral (5 vertebrae)
Coccyx (4 vertebrae)
Cervical Spine:
Most mobile compared to thoracic and lumbar.
Connection between peripheral nervous system and brain.
Injuries can affect neural transmission and possibly cause paralysis.
Thoracic Spine:
Longest section, connects with ribs, protects the heart and lungs.
Least flexible due to rib connections.
Lumbar Spine:
Bears the body’s weight and is the most flexible section.
Poor posture can lead to excessive pressure, herniated discs, and sciatic pain.
V. Joints
Definition: The area where two or more bones are attached.
Classification:
Fibrous Joints:
Immovable, bones fused with tough fibers (e.g., skull).
Cartilaginous Joints:
Slightly movable; bones held by ligaments and cartilage (e.g., intervertebral discs).
Synovial Joints:
Freely movable; characterized by a synovial cavity filled with fluid.
Synovial fluid reduces friction and cushions.
Types of Synovial Joints:
Ball and Socket: Rotates in many directions (e.g., hip and shoulder).
Hinge Joint: Moves in one plane (e.g., elbow, knee).
Pivot Joint: Allows rotation (e.g., neck).
Gliding Joint: Allows slight movements in all directions (e.g., wrist).
VI. Connective Tissues
Types:
Cartilage: Softer than bone, acts as shock absorber, lacks blood supply.
Types: Hyaline cartilage, fibrocartilage, elastic cartilage.
Ligaments: Tough fibrous tissue connecting bone to bone to stabilize joints.
Tendons: Connect muscles to bones, made of parallel collagen fibers for elasticity.
VII. Anatomy of Synovial Joint
Composed of ligaments, two or more bones, and an articular capsule.
Cartilage cushions ends of bones to prevent direct impact.
Synovial membrane secretes synovial fluid as lubricant.
Example: Knee Joint:
Formed by femur, tibia, fibula, and patella.
Contains ligaments: ACL, PCL, LCL, MCL for stability.
ACL injuries often result from abnormal movements.
Menisci (lateral and medial) cushion the knee.
VIII. Physiological Differences in Age Groups
Childhood: Bones are not very hard, are elastic; low stability.
Adolescence: Rapid growth and development; improved joint structure.
Adulthood: Loss of bone density as demineralization begins.
C. Nervous System
I. Functions
Components: Brain, spinal cord, and nerves.
Functions of the nervous system:
Control all bodily functions.
Facilitate abilities such as thinking and memory.
Adjust emotions in response to environmental changes.
II. Structure
Nerve Cell (Neuron): Basic structure and functional unit.
Composed of:
Cell Body (Soma)
Dendrites
Axon
Types of Neurons:
Sensory (Afferent) Neurons: Transmit signals to CNS.
Associative (Interneurons) Neurons: Connect sensory and motor neurons.
Motor (Efferent) Neurons: Send signals from CNS to muscles.
Myelin Sheath: Coats most axons, speeds up nerve impulse transmission.
III. Central Nervous System (CNS)
Composed of the brain and spinal cord; controls and processes perception and response.
Brain: A complex tissue with approximately one hundred billion neurons, protected by:
Meninges
Cerebrospinal fluid
Skull bones
Divisions of Brain:
Cerebrum: Largest part, divided into left and right hemispheres.
Each hemisphere corresponds to opposite body side.
Cerebral Cortex: Outer layer responsible for higher functions.
Divided into frontal, parietal, occipital, and temporal lobes.
Cerebellum: Coordinates muscle movements, balance, and posture.
Brainstem: Maintains basic life functions (breathing, heart rate).
IV. Physiological Differences in Age Groups
Childhood: Poorly developed inhibition leads to quick reactions.
Adolescence: Balanced neural processes improve analysis and synthesis.
Adulthood: Reduced neural activity and memory decline.
D. Muscular System
I. Functions
Composed of over 600 muscles, primarily attached to bones via tendons.
Main Functions:
Produce body movement.
Generate heat and energy through chemical reactions in muscle cells.
Muscle Characteristics:
Contractibility: Ability to contract.
Excitability: Respond to stimuli.
Extensibility: Ability to stretch.
Elasticity: Ability to return to resting length after stretching.
II. Types of Muscles
Available in three types:
Skeletal Muscles: Voluntary; cross-banded appearance. Works in pairs (agonist and antagonist).
Cardiac Muscles: Striated and branched; found in the heart; involuntary and fatigue-resistant.
Smooth Muscles: Involuntary; not striated; found in internal organs; fatigue-resistant.
III. Structure of Skeletal Muscle
Contains bundles of muscle fibers, which are made up of myofibrils.
Myofibrils: Functional unit of muscle; consists of the contractile proteins actin and myosin.
IV. Types of Muscle Fibers
Slow-twitch Fibers (Type I): High oxidative capacity, low glycolytic capacity; used for endurance activities.
Fast-twitch Fibers (Type II): Generate high force but fatigue quickly; further categorized into:
Type IIa: Fast oxidative glycolytic (aerobic)
Type IIb: Fast oxidative (anaerobic)
Muscle fiber characteristics comparison:
Slow-twitch (Type I):
Higher hemoglobin content
Higher fatigue resistance
Smaller size
Slower contraction velocity
Fast-twitch (Type II):
Lower hemoglobin content
Lower fatigue resistance
Larger size
Faster contraction velocity
V. Types of Muscle Contraction
Isotonic Contraction: Muscle length changes, causing movement; subdivided into:
Concentric Contraction: Muscle shortens while generating force.
Eccentric Contraction: Muscle lengthens while generating force.
Isometric Contraction: Muscle generates force without changing length; no movement occurs.
Isokinetic Contraction: Muscle maintains movement at constant speed using an isokinetic dynamometer.
VI. Neuromuscular Coordination
Agonist: Muscle that contracts and generates movement.
Antagonist: Muscle that relaxes and lengthens, opposing the agonist to protect joints.
Example: Elbow joint - Agonist: Biceps, Antagonist: Triceps.
Includes flexors (contraction leads to joint flexion) and extensors (contraction leads to joint extension).
VII. Reflex Actions
Reflex Arc: A pathway that mediates reflex actions; enables quick responses without brain path delay.
Conditioned Reflexes: Actions learned through experience; differ from inborn reflexes.
E. Cardiovascular System
I. Functions
Composed of the heart, blood vessels, and blood.
Main Functions:
Transportation of nutrients and oxygen.
Regulation of body temperature.
II. Blood Vessels
Arteries: Carry oxygenated blood away from the heart; thick-walled and elastic.
Veins: Carry deoxygenated blood back to the heart; thinner walls and have valves to prevent backflow.
Capillaries: Smallest vessels connecting arterioles and venules, allowing substance exchanges.
III. Heart
Located between the lungs, size of a closed fist with four chambers: two atria and two ventricles.
Heart Rate (HR):
Number of beats per minute; average for public: 60-80 bpm; athletes: 28-40 bpm.
Maximum Heart Rate Formula: HR_{ ext{max}} = 220 - ext{Age}
Stroke Volume (SV): Volume of blood pumped from LV per beat, influenced by heart size and capacity.
Cardiac Output (CO): Measures amount of blood pumped out per minute: CO = HR imes SV
IV. Cardiac Cycle and Blood Pressure
Cardiac Cycle: Sequence of contraction (systole) and relaxation (diastole).
Blood Pressure (BP): Pressure of circulating blood in arteries; indicates vital sign.
V. Circulation
Double Circulation: Blood passes through the heart twice in each complete circuit (pulmonary and systemic circuits).
Blood Flow Distribution: At rest (15-20% to muscles) vs. during maximal exercise (80-85% to muscles).
VI. Components of Blood
Red Blood Cells: Carry oxygen; shaped to maximize hemoglobin capacity.
White Blood Cells: Fight infections.
Platelets: Aid in blood clotting.
Plasma: Liquid component, transporting cells, nutrients, and waste.
F. Respiratory System
I. Functions
Respiration: Inhaling oxygen and exhaling carbon dioxide.
Sound Production: Produced by air expelling through vocal cords.
II. Structure
Major parts: nasal passages, trachea, lungs.
Air Path: Nasal cavity → Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Alveoli.
III. Breathing Mechanism
Inspiration: Thoracic cavity expands, dropping diaphragm and raising ribs to draw air in.
Expiration: Muscles relax, reducing cavity size to expel air out.
IV. Lung Capacities
Measurement: Use of spirometer; measures various lung volumes and capacities:
Tidal Volume (TV), Inspiratory Reserve Volume (IRV), Vital Capacity (VC), Residual Volume (RV), etc.
V. Pulmonary Ventilation and Gaseous Exchange
Pulmonary Ventilation: Exchange of gases between atmosphere and lungs.
Gaseous Exchange: In alveoli (external & internal respiration).
VI. Importance of Cardiorespiratory System
Critical for performance in physical activity; linked functions enhancing oxygen delivery and utilization.
VII. Maximal Oxygen Uptake (VO2 max)
Standard measure for cardiovascular fitness; involves respiratory and cardiovascular efficiency.
G. Energy System
I. Energy Sources
ATP (adenosine triphosphate) is vital for muscular contractions; limited storage spans about ten seconds.
II. Anaerobic System
ATP-PC System: Provides immediate energy without oxygen; short duration, high power, no lactic acid.
Lactic Acid System: Enables ATP resynthesis from glucose without oxygen; produces lactic acid, valuable for short bursts of exercise.
III. Aerobic System
Operates using oxygen over extended periods, producing energy from carbohydrates and fats, essential for endurance activities.
IV. Aerobic Stages
Stage 1: Glycolysis (glucose to pyruvic acid)
Stage 2: Krebs Cycle (in mitochondria, generating ATP)
Stage 3: Electron Transport Chain (O2 required for maximal ATP generation).