Stage 2: Body Systems and How They Work
Heart, lungs, brain, gut and more — how each body system works.
The Cardiovascular System
The heart, blood vessels and circulation — how blood reaches every cell.
Blood and the Lymphatic System
How fluid moves between blood and tissues, how the lymphatic system returns it to the circulation, and how lymph nodes support immune defence.
- How Fluid Moves Between Blood and Tissues (coming soon)
- How the Lymphatic System Drains and Protects (coming soon)
The Respiratory System
Lungs, airways and breathing — how oxygen gets in and carbon dioxide gets out.
- Lungs and Breathing (coming soon)
- How Breathing Actually Works (coming soon)
- How Oxygen Travels in Your Blood (coming soon)
- How Your Body Controls Breathing (coming soon)
- How the Airways Protect Themselves (coming soon)
The Nervous System
Brain, spinal cord and nerves — how the body senses and responds to the world.
- Brain and Nerves (coming soon)
- How Nerve Signals Actually Travel (coming soon)
- The Brain's Main Regions and What They Do (coming soon)
- The Autonomic Nervous System: Automatic Control (coming soon)
- How Nerves Are Protected and Repaired (coming soon)
The Endocrine System
Hormones, glands and metabolism — the body's chemical signalling network.
- Hormones and Metabolism (coming soon)
- How Hormones Actually Work (coming soon)
- The Thyroid: Setting the Body's Pace (coming soon)
- The Pituitary and the Master Control Chain (coming soon)
- Blood Sugar Control: Insulin and Glucagon (coming soon)
The Musculoskeletal System
Skin, bones, joints and muscles — how the body moves and protects itself.
- Skin, Bones and Muscles (coming soon)
- How Bones Grow, Break and Heal (coming soon)
- How Muscles Actually Contract (coming soon)
- Joints, Ligaments and Tendons: Trading Off Movement and Stability (coming soon)
- How Skin Protects and Repairs Itself (coming soon)
The Immune System
How the body defends itself against infection, cancer and foreign substances.
- Immune System and Infection (coming soon)
- How Innate Immunity Responds First (coming soon)
- How Adaptive Immunity Learns and Remembers (coming soon)
- The Lymphatic System: Where Immune Cells Live and Travel (coming soon)
- When the Immune System Overreacts or Under-Reacts (coming soon)
The Digestive System
From mouth to gut — how food is broken down, absorbed and waste removed.
- Digestive System (coming soon)
- How the Stomach Breaks Food Down (coming soon)
- How the Small Intestine Absorbs Nutrients (coming soon)
- The Liver, Gallbladder and Pancreas: Supporting Digestion (coming soon)
- The Large Intestine and the Gut Microbiome (coming soon)
The Renal System
Kidneys, fluid balance and waste — how the body filters the blood.
- Kidneys and Fluids (coming soon)
- How the Kidneys Actually Filter Blood (coming soon)
- How the Kidneys Help Control Blood Pressure (coming soon)
- The Urinary Tract: From Kidneys to Bladder (coming soon)
- Why Kidney Problems Can Stay Silent (coming soon)
The Reproductive System
Male and female reproductive systems, hormones, fertility and pregnancy basics.
- The Reproductive System: An Overview (coming soon)
- The Male Reproductive System (coming soon)
- The Female Reproductive System (coming soon)
- The Menstrual Cycle and Ovulation (coming soon)
- Sperm, Eggs, Fertilisation and Implantation (coming soon)
Eyes, Ears and Sensory Systems
How we see, hear and sense the world — and what can go wrong.
- How Vision Works (coming soon)
- How Hearing Works (coming soon)
- How the Eye Focuses Light (coming soon)
- Balance: The Ear's Hidden Second Job (coming soon)
- Why the Eye's Focusing System Can Fail (coming soon)
- Conductive and Sensorineural: Two Ways Hearing Can Break Down (coming soon)
How Body Systems Work Together
Why no body system works alone, and how the systems interact in real life.
- How body systems interact (coming soon)