Anatomy of the circulatory system

Join Dr Natasha Barrett as she explains the structure of the circulatory system, including the different types of blood vessels and their construction.

The network of blood vessels in the body is vast. There are a number of different types of vessels that make up your circulatory system. The wall of the vessels consist of three layers (tunica):

• Tunica intima: The innermost layer or tunica intima is a layer of endothelial cells
• Tunica media: The middle layer or tunica media is made of smooth muscle cells
• Tunica externa: The outer layer or tunica externa consists of connective tissue and wraps around the vessel to protect it and to anchor it to surrounding structures

The different types of vessels are:

• Arteries: Arteries have a thicker smooth muscle layer to enable them to cope with the force of blood
• Capillaries: Capillaries are tiny blood vessels. They no longer have a tunica media or externa and consist of a single layer of endothelial cells
• Veins: After the capillaries the blood travels in the smallest veins known as venules, then in the veins before finally travelling in the largest of the veins, the vena cava to be returned into the heart
• Lymphatics: Carries hormonal messages, immune responses and bathes the cells of the body

You can download the Week 1 supplement, which contains additional images and descriptions to help you understand the topics covered in this video.

Have you heard of the house plumbing system analogy used to describe the circulatory system before? Which parts of the circulatory system were you already aware of?