Human Body Biology

Master human body biology for RRB exam preparation with comprehensive coverage of organ systems, functions, and health-related concepts.

Introduction to Human Body

Organization of Human Body

Levels of Organization

• Cells: Basic structural and functional units
• Tissues: Groups of similar cells performing specific functions
• Organs: Structures composed of multiple tissue types
• Organ Systems: Groups of organs working together
• Organism: Complete living being

Body Cavities

• Dorsal Cavity: Cranial cavity and spinal cavity
• Ventral Cavity: Thoracic cavity and abdominopelvic cavity
• Thoracic Cavity: Contains heart, lungs, esophagus
• Abdominopelvic Cavity: Contains digestive, urinary, reproductive organs

Body Systems Overview

Major Body Systems

• Skeletal System: Framework and protection
• Muscular System: Movement and posture
• Circulatory System: Transport and distribution
• Respiratory System: Gas exchange
• Digestive System: Food processing and nutrient absorption
• Nervous System: Control and coordination
• Endocrine System: Hormone regulation
• Excretory System: Waste removal
• Reproductive System: Species continuation

Skeletal System

Structure and Function

Bone Composition

• Compact Bone: Dense outer layer
• Spongy Bone: Porous inner layer
• Bone Marrow: Red and yellow marrow
• Periosteum: Outer membrane covering bones

Major Bones

• Skull: Protects brain, 29 bones
• Vertebral Column: 33 vertebrae, supports body
• Rib Cage: 12 pairs, protects heart and lungs
• Limbs: Arms and legs with respective bones

Bone Types

• Long Bones: Femur, humerus, tibia
• Short Bones: Carpals, tarsals
• Flat Bones: Skull bones, sternum
• Irregular Bones: Vertebrae, facial bones

Joints and Movement

Joint Types

• Fibrous Joints: Immovable (sutures in skull)
• Cartilaginous Joints: Slightly movable (vertebrae)
• Synovial Joints: Freely movable (knee, elbow)

Joint Classification

• Hinge Joints: Elbow, knee (movement in one plane)
• Ball and Socket: Hip, shoulder (wide range of motion)
• Pivot Joints: Neck rotation (rotation around axis)
• Gliding Joints: Wrist, ankle (sliding movement)

Functions of Skeletal System

• Support: Provides structural framework
• Protection: Protects vital organs
• Movement: Works with muscles for movement
• Blood Cell Production: Red marrow produces blood cells
• Mineral Storage: Stores calcium and phosphorus

Muscular System

Muscle Types

Skeletal Muscles

• Voluntary Control: Under conscious control
• Striated Appearance: Has striped appearance
• Multi-nucleated: Contains multiple nuclei
• Attached to Bones: Moves skeleton

Smooth Muscles

• Involuntary Control: Not under conscious control
• Non-striated: Smooth appearance
• Single Nucleus: Contains one nucleus
• Found in Organs: Walls of hollow organs

Cardiac Muscle

• Heart Muscle: Found only in heart
• Involuntary: Automatic contraction
• Striated: Has striped appearance
• Intercalated Discs: Special connections between cells

Muscle Function

Muscle Contraction

• Sliding Filament Theory: Actin and myosin filaments slide
• ATP Requirement: Energy for contraction
• Calcium Role: Triggers contraction
• Neuromuscular Junction: Nerve-muscle connection

Major Muscle Groups

• Facial Muscles: Expression, chewing
• Neck Muscles: Head movement
• Arm Muscles: Lifting, reaching
• Leg Muscles: Walking, running
• Core Muscles: Posture, stability

Muscle Pairs

• Agonist: Prime mover muscle
• Antagonist: Opposing muscle
• Synergist: Assists prime mover
• Fixator: Stabilizes origin

Circulatory System

Heart Structure

Heart Chambers

• Right Atrium: Receives deoxygenated blood
• Right Ventricle: Pumps blood to lungs
• Left Atrium: Receives oxygenated blood
• Left Ventricle: Pumps blood to body

Heart Valves

• Atrioventricular Valves: Between atria and ventricles
• Semilunar Valves: Between ventricles and arteries
• Tricuspid Valve: Right atrioventricular valve
• Mitral Valve: Left atrioventricular valve

Blood Vessels

• Arteries: Carry blood away from heart
• Veins: Carry blood to heart
• Capillaries: Site of exchange
• Heart: Central pumping organ

Blood Components

Plasma

• Water: 90% of plasma
• Proteins: Albumin, globulins, fibrinogen
• Nutrients: Glucose, amino acids, lipids
• Waste Products: Urea, carbon dioxide

Red Blood Cells (Erythrocytes)

• Hemoglobin: Oxygen-carrying protein
• Biconcave Shape: Increases surface area
• No Nucleus: Mature RBCs lack nucleus
• Life Span: 120 days

White Blood Cells (Leukocytes)

• Immunity: Fight infections
• Types: Neutrophils, lymphocytes, monocytes
• Nucleus Present: Contains nucleus
• Mobility: Can move through tissues

Platelets (Thrombocytes)

• Clotting: Blood clot formation
• Cell Fragments: Not complete cells
• No Nucleus: Lack nucleus
• Short Life: 7-10 days

Respiratory System

Respiratory Organs

Upper Respiratory Tract

• Nose: Air entry, filtration, warming
• Nasal Cavity: Air passage, humidification
• Pharynx: Common passage for air and food
• Larynx: Voice box, contains vocal cords

Lower Respiratory Tract

• Trachea: Windpipe, air passage
• Bronchi: Branches into lungs
• Bronchioles: Small air passages
• Alveoli: Gas exchange sites

Breathing Process

Inspiration (Inhalation)

• Diaphragm Contracts: Moves downward
• Rib Cage Rises: Intercostal muscles contract
• Volume Increases: Chest cavity expands
• Pressure Decreases: Air flows in

Expiration (Exhalation)

• Diaphragm Relaxes: Moves upward
• Rib Cage Falls: Intercostal muscles relax
• Volume Decreases: Chest cavity contracts
• Pressure Increases: Air flows out

Gas Exchange

• Alveoli: Site of gas exchange
• Oxygen Diffusion: Into blood
• Carbon Dioxide Diffusion: Out of blood
• Partial Pressure: Drives gas exchange

Digestive System

Digestive Tract

Alimentary Canal

• Mouth: Ingestion, mechanical breakdown
• Esophagus: Food passage to stomach
• Stomach: Protein digestion
• Small Intestine: Nutrient absorption
• Large Intestine: Water absorption

Accessory Organs

• Liver: Bile production, metabolism
• Gallbladder: Bile storage
• Pancreas: Enzyme production
• Salivary Glands: Saliva production

Digestion Process

Mouth Digestion

• Mechanical: Teeth grind food
• Chemical: Salivary amylase acts on starch
• Formation: Bolus formation
• Swallowing: Tongue pushes food to pharynx

Stomach Digestion

• Acid: Hydrochloric acid kills bacteria
• Enzymes: Pepsin digests proteins
• Churning: Mechanical mixing
• Chyme: Partially digested food

Small Intestine Digestion

• Enzymes: Pancreatic and intestinal enzymes
• Bile: Fat emulsification
• Absorption: Nutrient absorption
• Villi: Increase surface area

Large Intestine Function

• Water Absorption: Reabsorbs water
• Electrolyte Absorption: Absorbs salts
• Vitamin Production: Bacteria produce vitamins
• Waste Formation: Forms feces

Nervous System

Central Nervous System

Brain Structure

• Cerebrum: Higher functions, thinking
• Cerebellum: Balance, coordination
• Brain Stem: Vital functions
• Diencephalon: Thalamus, hypothalamus

Brain Regions

• Frontal Lobe: Reasoning, planning
• Parietal Lobe: Sensory information
• Temporal Lobe: Hearing, memory
• Occipital Lobe: Vision

Spinal Cord

• Neural Pathway: Connects brain to body
• Reflex Center: Simple reflexes
• Protection: Surrounded by vertebrae
• Meninges: Protective membranes

Peripheral Nervous System

Somatic Nervous System

• Voluntary Control: Skeletal muscle control
• Sensory Input: Receives sensory information
• Motor Output: Sends motor signals
• Reflex Arces: Automatic responses

Autonomic Nervous System

• Involuntary Control: Automatic functions
• Sympathetic: Fight or flight response
• Parasympathetic: Rest and digest
• Homeostasis: Maintains internal balance

Neuron Structure

• Cell Body: Contains nucleus
• Dendrites: Receive signals
• Axon: Transmits signals
• Synapse: Connection between neurons

Endocrine System

Major Glands

Pituitary Gland

• Master Gland: Controls other glands
• Anterior Pituitary: Growth hormone, thyroid-stimulating hormone
• Posterior Pituitary: ADH, oxytocin
• Location: Base of brain

Thyroid Gland

• Metabolism: Regulates metabolic rate
• Thyroxine: Metabolic hormone
• Calcitonin: Calcium regulation
• Location: Neck region

Adrenal Glands

• Adrenaline: Stress hormone
• Cortisol: Stress response
• Aldosterone: Sodium balance
• Location: Above kidneys

Pancreas

• Insulin: Lowers blood glucose
• Glucagon: Raises blood glucose
• Digestive Enzymes: Food digestion
• Location: Behind stomach

Hormone Functions

Growth and Development

• Growth Hormone: Body growth
• Thyroid Hormones: Development
• Sex Hormones: Sexual development
• Growth Factors: Cell growth

Metabolism Regulation

• Insulin: Glucose metabolism
• Thyroxine: Basal metabolic rate
• Cortisol: Stress metabolism
• Adrenaline: Emergency metabolism

Homeostasis

• ADH: Water balance
• Aldosterone: Electrolyte balance
• Parathyroid Hormone: Calcium balance
• Calcitonin: Calcium regulation

Excretory System

Kidney Structure and Function

Kidney Anatomy

• Cortex: Outer region
• Medulla: Inner region
• Renal Pelvis: Collects urine
• Nephrons: Functional units

Nephron Function

• Filtration: Blood filtration in glomerulus
• Reabsorption: Useful substances reabsorbed
• Secretion: Waste products secreted
• Excretion: Urine formation

Urine Formation Process

• Glomerular Filtration: Initial filtration
• Tubular Reabsorption: Reabsorption of water and solutes
• Tubular Secretion: Secretion of wastes
• Water Conservation: Concentrated urine

Other Excretory Organs

Skin

• Sweat Glands: Excrete sweat
• Temperature Regulation: Cooling effect
• Water Loss: Minor water excretion
• Salt Excretion: Small salt loss

Lungs

• Carbon Dioxide: Exhaled CO₂
• Water Vapor: Water in exhaled air
• Volatile Compounds: Some waste excretion
• pH Regulation: CO₂ removal affects pH

Liver

• Urea Formation: Protein breakdown product
• Bile Pigments: Bilirubin excretion
• Detoxification: Poison removal
• Metabolic Wastes: Various waste products

Reproductive System

Male Reproductive System

Primary Organs

• Testes: Sperm production, testosterone
• Epididymis: Sperm maturation
• Vas Deferens: Sperm transport
• Urethra: Urine and semen passage

Accessory Glands

• Seminal Vesicles: Semen fluid
• Prostate Gland: Prostatic fluid
• Bulbourethral Glands: Pre-ejaculate
• Function: Provide nutrients, medium for sperm

Sperm Production

• Spermatogenesis: Sperm formation
• Sertoli Cells: Support sperm development
• Leydig Cells: Testosterone production
• Hormonal Control: FSH, LH regulation

Female Reproductive System

Primary Organs

• Ovaries: Egg production, hormones
• Fallopian Tubes: Egg transport, fertilization site
• Uterus: Fetal development
• Vagina: Birth canal, copulation

Ovarian Cycle

• Follicular Phase: Egg maturation
• Ovulation: Egg release
• Luteal Phase: Corpus luteum formation
• Menstruation: Uterine lining shedding

Hormonal Regulation

• FSH: Follicle development
• LH: Ovulation, corpus luteum
• Estrogen: Female characteristics
• Progesterone: Pregnancy maintenance

Nutrition and Metabolism

Nutrients

Macronutrients

• Carbohydrates: Energy source (4 kcal/g)
• Proteins: Building blocks (4 kcal/g)
• Fats: Energy storage (9 kcal/g)
• Water: Essential for life

Micronutrients

• Vitamins: Organic compounds, essential in small amounts
• Minerals: Inorganic elements, essential for function
• Trace Elements: Required in minute amounts
• Antioxidants: Protect against cellular damage

Balanced Diet

• Proteins: 10-15% of daily calories
• Carbohydrates: 55-60% of daily calories
• Fats: 25-30% of daily calories
• Vitamins and Minerals: Adequate intake

Metabolism

Basal Metabolic Rate (BMR)

• Definition: Energy required at rest
• Factors: Age, sex, body composition
• Measurement: Calories burned per day
• Importance: Weight management

Energy Balance

• Positive Balance: Weight gain
• Negative Balance: Weight loss
• Energy Balance: Weight maintenance
• Factors: Diet, exercise, metabolism

Health and Disease

Common Diseases

Cardiovascular Diseases

• Hypertension: High blood pressure
• Coronary Artery Disease: Heart artery blockage
• Stroke: Brain blood vessel blockage
• Heart Failure: Pumping inability

Respiratory Diseases

• Asthma: Airway inflammation
• COPD: Chronic obstructive pulmonary disease
• Pneumonia: Lung infection
• Tuberculosis: Bacterial lung infection

Digestive Diseases

• Peptic Ulcer: Stomach lining damage
• Hepatitis: Liver inflammation
• Gallstones: Gallbladder stones
• Diarrhea: Frequent loose stools

Prevention and Health

Healthy Lifestyle

• Balanced Diet: Proper nutrition
• Regular Exercise: Physical activity
• Adequate Sleep: 7-8 hours nightly
• Stress Management: Mental health

Vaccination

• Immunity: Disease prevention
• Herd Immunity: Community protection
• Schedule: Recommended vaccination timeline
• Importance: Public health

Regular Check-ups

• Early Detection: Disease identification
• Prevention: Risk factor management
• Monitoring: Health status tracking
• Treatment: Early intervention

First Aid and Emergency

Common Emergencies

CPR (Cardiopulmonary Resuscitation)

• Chest Compressions: 30 compressions
• Rescue Breaths: 2 breaths
• Ratio: 30:2 compression-to-breath
• Continuation: Until help arrives

Choking

• Heimlich Maneuver: Abdominal thrusts
• Back Blows: Alternate method
• Chest Thrusts: For pregnant women
• Recognition: Universal choking sign

Bleeding Control

• Direct Pressure: Apply pressure
• Elevation: Raise injured limb
• Pressure Points: Major artery pressure
• Tourniquet: Last resort, severe bleeding

Basic First Aid

Burns

• Cool Water: Run cool water over burn
• Cover: Clean, dry dressing
• Pain Relief: Over-the-counter medication
• Medical Attention: Severe burns

Fractures

• Immobilization: Don’t move injured area
• Splint: Support injured limb
• Ice: Reduce swelling
• Medical Help: Seek immediate attention

Fainting

• Position: Lay person flat
• Elevation: Raise legs above heart
• Fresh Air: Ensure good ventilation
• Recovery: Usually quick recovery

Practice Questions

Question 1

Which chamber of the heart pumps oxygenated blood to the body?

Question 2

What is the function of red blood cells?

Question 3

Name the organ that produces insulin.

Question 4

What is the basic structural unit of the nervous system?

Question 5

Which part of the brain is responsible for balance and coordination?

Question 6

What is the main function of the kidneys?

Question 7

Name the gas that is transported by hemoglobin in blood.

Question 8

What is the function of the diaphragm in breathing?

Question 9

Which organ produces bile?

Question 10

What is the normal human body temperature?

Quick Reference

Important Numbers

Body Statistics

• Normal Body Temperature: 37°C (98.6°F)
• Normal Heart Rate: 60-100 beats per minute
• Normal Blood Pressure: 120/80 mmHg
• Normal Respiratory Rate: 12-20 breaths per minute

Blood Values

• Blood Volume: 5-6 liters (adult)
• RBC Count: 4.5-5.5 million/mm³
• WBC Count: 4,000-11,000/mm³
• Platelet Count: 150,000-450,000/mm³

Organ Systems and Functions

Common Medical Terms

Prefixes

• Hypo-: Below normal
• Hyper-: Above normal
• Tachy-: Fast
• Brady-: Slow

Suffixes

• -itis: Inflammation
• -osis: Condition
• -ectomy: Removal
• -plasty: Surgical repair

Memory Tips

Body Systems

• Skeletal: Framework and protection
• Muscular: Movement and posture
• Circulatory: Transport system
• Respiratory: Gas exchange
• Digestive: Food processing
• Nervous: Control center
• Endocrine: Hormone regulation
• Excretory: Waste removal

Blood Flow Path

• Right Atrium → Right Ventricle → Lungs → Left Atrium → Left Ventricle → Body

Digestive Process

• Mouth → Esophagus → Stomach → Small Intestine → Large Intestine → Anus

Brain Functions

• Frontal: Thinking, planning
• Parietal: Sensory
• Temporal: Hearing, memory
• Occipital: Vision
• Cerebellum: Balance
• Brain Stem: Vital functions

Back to Science Topics

All Topic Practice