Heart & Blood: Circulatory Systems Explained

Year 8 Biology Understanding How Blood Flows Through Your Body The Amazing Journey of Circulation

What Do You Already Know?

What happens when you exercise and your heart beats faster? Why do you think your pulse changes? Have you ever wondered how blood travels around your body?

What is the Circulatory System?

A transport network throughout your body Delivers oxygen and nutrients to every cell Removes waste products like carbon dioxide Made up of heart, blood vessels, and blood

The Heart: Your Body's Engine

A muscular pump about the size of your fist Beats approximately 100,000 times per day Has four chambers: two atria and two ventricles Never stops working throughout your entire life

Journey of Blood Through the Heart

Types of Blood Vessels

{"left":"Arteries: Carry blood AWAY from the heart\nUsually carry oxygen-rich blood\nHave thick, muscular walls\nCan feel your pulse in arteries","right":"Veins: Carry blood TO the heart\nUsually carry oxygen-poor blood\nHave thinner walls with valves\nOften visible under your skin"}

Capillaries: The Connection Points

Tiniest blood vessels in your body Only one cell thick Where oxygen and nutrients are exchanged Connect arteries to veins Found in every tissue and organ

Feel Your Pulse Activity

Find your pulse on your wrist or neck Count beats for 15 seconds Multiply by 4 to get beats per minute Record your resting heart rate Compare with classmates

What is Blood Made Of?

55% Plasma (liquid part) 45% Blood cells Red blood cells carry oxygen White blood cells fight infection Platelets help blood clot

Why Do We Need Two Circuits?

Think about this: Why doesn't blood go directly from your heart to your lungs and then to your body? What would happen if oxygenated and deoxygenated blood mixed?

Two Circulation Circuits

{"left":"Pulmonary Circuit\nHeart → Lungs → Heart\nPicks up oxygen\nDrops off carbon dioxide\nShort distance","right":"Systemic Circuit\nHeart → Body → Heart\nDelivers oxygen to tissues\nCollects carbon dioxide\nMuch longer distance"}

How Blood Carries Oxygen

Red blood cells contain hemoglobin Hemoglobin binds to oxygen in the lungs Creates oxyhemoglobin (bright red) Releases oxygen to body tissues Becomes deoxyhemoglobin (dark red)