Understanding Blood Vessels & Circulation

 

What Are Blood Vessels?

• Blood vessels are like roads that carry blood around your body.
• Think of them as highways (arteries), bridges and small streets (capillaries), and return routes (veins) making sure blood can reach every tiny part of you and then get back again.

 

Types of Blood Vessels

Arteries

• Carry blood away from the heart at a high pressure.
• Transport oxygenated blood, with the pulmonary artery being an exception
• Have thick, strong, muscular walls to handle high pressure and contain elastic fibres; like a big highway built to handle fast traffic.
• Have narrow lumen to maintain high pressure.

Veins

• Carry blood towards the heart at a low pressure.
• Transport deoxygenated blood away from the body, with the pulmonary vein being an exception
• Have thinner walls and often have little “one-way gates” (valves) that stops blood from going backwards and prevents backflow under low pressure.
• Have wide lumen as blood pressure is lower.
• Imagine a gentle slope with one-way doors, so nothing rolls the wrong way.

Capillaries

• Tiny, thin-walled vessels, one cell think, which allows substances to easily diffuse in and out.
• Carry blood to cells of the tissues.
• Transport oxygenated blodd from the arteries to cells and deoxygenated blodd from cells to the veins
• Super narrow lumen, allowing blood cells to squeeze through one by one, dropping off oxygen, glucose, nutrients and picking up waste.
• Think of them like small bridges between bigger roads, allowing easy handover of packages.

 

How Structure Matches Job

• Arteries: Thick walls to handle strong pushes of blood from the heart.
• Veins: Thinner walls because pressure is lower, and valves to keep blood moving in the right direction.
• Capillaries: Very thin walls (just one cell thick!) to make trading oxygen and nutrients easy.

 

Important Blood Vessels to Know

 

Organ	Goes Towards Organ	Away Towards Organ
Kidney	Renal Artery	Renal Artery
Heart	Pulmonary Vein, Vena Cava	Aorta, Pulmonary Artery
Lung	Pulmonary Artery	Pulmonary Vein

 

To and from the Heart:

• Aorta: Takes oxygen-rich blood away from the heart.
• Vena Cava: Returns blood lacking oxygen back to the heart.
• Pulmonary Artery: Carries blood from heart to lungs to get oxygen.
• Pulmonary Vein: Brings oxygen-rich blood from lungs back to heart.

To and from the Kidneys:

• Renal Artery: Delivers blood to the kidney to be cleaned.
• Renal Vein: Carries cleaned blood back towards the heart.

 

Arterioles and Venules: Extended

• Arteries divide more as they move away from the heart and get more narrow
• The vessels that join the arteries to the capillaries are arterioles
• Veins act in a similar way, as they get further fron the heart they get more narrow
• The vessels that join the capillaries to the veins are venules