🔬 Introduction
Human physiology is the study of how different systems in the body function and work together to sustain life. The human body has several organ systems, each performing vital roles.
🫁 The Human Digestive System
👉 Function: Converts food into simpler substances for absorption and energy production.
👉 Main Organs:
- Mouth – Chews food, mixes with saliva (enzymes like amylase start digestion).
- Oesophagus – Transfers food via peristalsis.
- Stomach – Secretes gastric juices (HCl, pepsin) for protein digestion.
- Small Intestine – Digestion and nutrient absorption (via villi).
- Large Intestine – Absorbs water, forms faeces.
- Liver & Pancreas – Liver produces bile (digests fats); pancreas secretes digestive enzymes.
📝 Key Concept: Digestion is mechanical (chewing) and chemical (enzymes breaking food down).
🫀 Circulatory System
👉 Function: Transports oxygen, nutrients, hormones, and removes waste.
👉 Main Organs:
- Heart ❤️ – Pumps blood throughout the body.
- Blood Vessels – Includes arteries (carry oxygen-rich blood), veins (carry deoxygenated blood), and capillaries (exchange nutrients and gases).
- Blood Components:
- RBCs (Red Blood Cells) – Carry oxygen using haemoglobin.
- WBCs (White Blood Cells) – Fight infections.
- Platelets – Help in blood clotting.
- Plasma – Carries nutrients, hormones, and waste.
📝 Key Concept: The heart has 4 chambers, and circulation is double circulation (pulmonary & systemic).
🫁 Respiratory System
👉 Function: Supplies oxygen to the body and removes carbon dioxide.
👉 Main Organs:
- Nasal Cavity – Filters air with cilia and mucus.
- Trachea – Windpipe that carries air to lungs.
- Bronchi & Bronchioles – Branch into lungs.
- Lungs & Alveoli – Exchange of gases occurs here via diffusion.
- Diaphragm – Helps in breathing movements.
📝 Key Concept: Respiration includes inhalation (oxygen intake) and exhalation (carbon dioxide release).
🧠 Nervous System
👉 Function: Controls and coordinates body functions.
👉 Main Organs:
- Brain 🧠 – Controls actions, thoughts, and emotions.
- Spinal Cord – Transfers signals between brain and body.
- Nerves – Carry messages through neurons.
💡 Brain Parts:
- Cerebrum – Controls thinking, memory, voluntary actions.
- Cerebellum – Balances movements.
- Medulla Oblongata – Controls involuntary actions (breathing, heartbeat).
📝 Key Concept: Neurons transmit signals through electrical and chemical impulses.
⚡ Excretory System
👉 Function: Removes waste from the body (like urea, excess water, salts).
👉 Main Organs:
- Kidneys – Filter blood, produce urine.
- Ureters – Carry urine to the bladder.
- Urinary Bladder – Stores urine.
- Urethra – Expels urine out of the body.
📝 Key Concept: The kidney contains nephrons, the functional unit for filtration.
🌱 Endocrine System
👉 Function: Controls hormone secretion for body regulation.
👉 Important Glands & Hormones:
- Pituitary Gland – Master gland (growth hormone).
- Thyroid – Controls metabolism (thyroxine).
- Pancreas – Regulates blood sugar (insulin, glucagon).
- Adrenal Glands – Handles stress (adrenaline).
📝 Key Concept: Hormones act as chemical messengers in the body.
💡 Key Points to Remember
✅ Digestion occurs in stages: ingestion → digestion → absorption → assimilation → egestion.
✅ The heart pumps oxygenated and deoxygenated blood through separate chambers.
✅ Breathing involves inhalation (oxygen in) and exhalation (carbon dioxide out).
✅ The nervous system uses electrical signals, while the endocrine system uses hormones.
✅ Excretion maintains internal balance by removing metabolic waste.