Learning Objectives
- Understand the circulatory system in humans
- Learn about blood and its components
- Know about excretion in animals
- Understand transport of substances in plants
Key Concepts
Circulatory System
The circulatory system transports substances throughout the body. It consists of the heart, blood vessels, and blood.
Blood and Its Components
- Plasma: Liquid part of blood (yellowish). Carries dissolved nutrients, CO₂, and waste.
- Red Blood Cells (RBC): Contain haemoglobin that carries oxygen. Give blood its red colour.
- White Blood Cells (WBC): Fight against germs and infections.
- Platelets: Help in blood clotting to stop bleeding.
Blood Vessels
- Arteries: Carry oxygenated blood from heart to body (except pulmonary artery).
- Veins: Carry deoxygenated blood from body to heart (except pulmonary vein).
- Capillaries: Thin-walled, tiny vessels for exchange of substances between blood and cells.
The Heart
The heart has four chambers: two upper atria and two lower ventricles. The right side receives deoxygenated blood and sends it to lungs. The left side receives oxygenated blood from lungs and pumps it to the body. A heartbeat includes one contraction and one relaxation. Stethoscope is used to hear heartbeats. Normal pulse rate: 72-80 beats per minute.
Excretion
Excretion: Removal of waste products from the body.
Excretory system: Kidneys filter blood and remove urea, excess water, and salts as urine. Urine flows from kidneys → ureters → urinary bladder → urethra.
Dialysis: Artificial filtering of blood when kidneys fail.
Transport in Plants
Xylem: Transports water and minerals from roots to leaves (upward).
Phloem: Transports food from leaves to other parts (downward and all directions).
Transpiration: Loss of water through stomata. Creates a suction pull that helps in upward movement of water.
Summary
Blood circulates through arteries, veins, and capillaries, pumped by the four-chambered heart. Blood has RBCs, WBCs, platelets, and plasma. Kidneys excrete waste as urine. In plants, xylem carries water upward and phloem transports food.
Important Terms
- Haemoglobin: Oxygen-carrying pigment in RBCs
- Artery: Carries blood away from heart
- Vein: Carries blood to heart
- Xylem: Water transport tissue in plants
- Phloem: Food transport tissue in plants
- Transpiration: Water loss through leaf stomata
Quick Revision
- Blood: Plasma + RBC + WBC + Platelets
- Arteries: away from heart, Veins: to heart
- Heart: 4 chambers (2 atria + 2 ventricles)
- Kidneys → Ureters → Bladder → Urethra
- Xylem: water up, Phloem: food all directions