Blood Vessels: Arteries, Capillaries & Veins in a Snap! Unlock the full A-level Biology course at http://bit.ly/2Zb97S7 created by Adam Tildesley, Biology expert at SnapRevise and graduate of Cambridge University.

SnapRevise is the UK’s leading A-level and GCSE revision & exam preparation resource offering comprehensive video courses created by A* Oxbridge tutors. Our courses are designed around the OCR, AQA, SNAB, Edexcel B, WJEC, CIE and IAL exam boards, concisely covering all the important concepts required by each specification. In addition to all the content videos, our courses include hundreds of exam question videos, where we show you how to tackle questions and walk you through step by step how to score full marks.

Sign up today and together, let’s make A-level Biology a walk in the park!

The key points covered of this video include:

1. Blood Vessels
2. Arteries and Arterioles
3. Capillaries
4. Veins and Venules

Blood Vessels

Transporting blood in vessels allows it to be pumped at high pressure delivering nutrients and removing waste more efficiently. The circulatory system has five different types of vessel. These are adapted to different roles based on their relative distance from the heart. All have smooth and thin inner layer of cells called the endothelium.

Arteries and Arterioles

Arteries carry blood away from the heart at high pressure. To cope with the high pressure artery walls are very thick. Artery walls have layers of elastic tissue and smooth muscle encased in a thick outer layer of collagen. Arterioles have a similar structure to arteries but they are smaller and have relatively thinner muscle and elastic layers. Contraction of smooth muscle constricts the arteriole and is used to control the flow of blood through the body.

Capillaries

Capillaries have very thin walls consisting of just the single-celled layer of endothelium. The lumen of capillaries is very narrow and can squeeze red blood cells against the endothelium to improve transfer of oxygen. The increased resistance greatly slows the flow of blood in the capillary beds.

Veins and Venules

Veins carry low pressure blood back to the heart. Vein walls are not thick and the lumen is very wide to maximise blood flow. Veins have valves that ensure the low pressure blood only flows in the right direction. Movement of skeletal muscles compresses the veins and pushes the blood along. Venules are smaller than veins and lack valves. They deliver blood from the capillary beds to the veins.

Summary

Blood is transported in different types of blood vessel depending on distance from the heart in the circulatory system
Arteries and arterioles are adapted to transport blood at high pressure and control which parts of the body blood flows to
Capillaries are adapted to exchange substances with the surrounding body tissues
Vein and venules are adapted to transport low pressure blood from capillary beds back to the heart
Veins have valves that prevent low pressure blood from travelling in the wrong direction