Blood vessels are tubular structures that transport blood throughout the body. They are part of the circulatory system, working together with the heart to deliver oxygen and nutrients and remove waste products.
🧩 Main Types of Blood Vessels
There are three major types of blood vessels:
| Type | Direction of Blood Flow | Main Function |
|---|---|---|
| Arteries | Away from the heart | Carry oxygen-rich blood to body tissues |
| Veins | Toward the heart | Return oxygen-poor blood to the heart |
| Capillaries | Between arteries and veins | Exchange of gases, nutrients, and waste with cells |
🔍 Details of Each Type
🔴 Arteries
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Carry blood from the heart to the body.
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Thick, elastic walls to handle high pressure.
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Largest artery: Aorta.
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Usually carry oxygenated blood, except for the pulmonary artery (which carries deoxygenated blood to the lungs).
🔵 Veins
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Carry blood back to the heart.
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Thinner walls, lower pressure than arteries.
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Contain valves to prevent backflow.
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Largest veins: Superior and Inferior Vena Cava.
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Usually carry deoxygenated blood, except for the pulmonary vein (which carries oxygenated blood from the lungs).
⚪ Capillaries
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Microscopic vessels, just one cell thick.
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Connect arteries and veins.
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Site of gas exchange (oxygen ↔ carbon dioxide) and nutrient/waste exchange with tissues.
⚙️ Functions of Blood Vessels
| Function | Description |
|---|---|
| Transport | Deliver oxygen, nutrients, and hormones to tissues |
| Waste removal | Remove carbon dioxide, urea, and other waste products |
| Temperature control | Adjust blood flow to help regulate body temperature |
| Blood pressure regulation | Help control and maintain blood pressure via vessel diameter |
| Immune response | Deliver white blood cells to areas of infection or injury |
🩺 Common Blood Vessel Disorders
| Condition | Description |
|---|---|
| Atherosclerosis | Build-up of plaque inside arteries, narrowing blood flow |
| Hypertension | Chronic high blood pressure; puts strain on vessel walls |
| Varicose veins | Enlarged, twisted veins (often in the legs), due to valve failure |
| Thrombosis | Blood clot inside a vessel; can block blood flow |
| Stroke | Interruption of blood supply to the brain (due to clot or vessel rupture) |
| Heart attack | Blockage of coronary arteries leads to damage in heart muscle |
| Aneurysm | Weakening and bulging of a blood vessel wall; can burst |
🧠 Interesting Facts About Blood Vessels
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The human body has over 100,000 kilometers (60,000+ miles) of blood vessels.
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Capillaries are so small that red blood cells must pass through them one at a time.
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Arteries pulse in rhythm with the heart — that's what you feel when you check your pulse.
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The color of veins under the skin appears blue due to how light penetrates and reflects — not because the blood is blue.
✅ Summary Table
| Vessel Type | Blood Flow Direction | Oxygen Level | Structure & Features |
|---|---|---|---|
| Artery | Heart → Body | High (oxygenated) | Thick, elastic, high pressure |
| Vein | Body → Heart | Low (deoxygenated) | Thin walls, valves, lower pressure |
| Capillary | Connect arteries/veins | Varies (gas exchange) | Extremely thin, site of exchange |