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BBC Bitesize - GCSE Biology (Single Science) - Blood - Revision 1

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Learn about blood, a complex liquid tissue, and how it transports oxygen, dissolved substances and heat around the body.

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In this video, we look at the different parts of the blood and how they function. We explore the roles of blood plasma, red blood cells, white blood cells and platelets.

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Blood Vessels, Part 1 - Form and Function: Crash Course Anatomy & Physiology #27

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Blood is carried through three different types of blood vessels in the body:

1. arteries

2. capillaries

3. veins

All blood vessels are specifically structured to perform their function. For example, a capillary is microscopically thin to allow gases to exchange, the arteries are tough and flexible to cope with high pressure blood flow and the veins contain valves to prevent the blood from travelling backwards when at low pressure. All vessels feature varying lumen size. The lumen is the hollow opening or the space inside the blood vessel.

Blood

The main function of blood is to transport nutrients and oxygen to the cells of the body.

Blood is made up of four components:

1. red blood cells - these transport oxygen around the body

2. white blood cells - these fight infection

3. platelets - these clot to prevent blood loss during injury

4. plasma - this is the liquid part of blood

Red blood cells are very important for sport and physical activity because they contain haemoglobin. Haemoglobin allows them to carry oxygen from the lungs to the working muscles.

Red blood cells are disc-shaped cells with no nucleus. They are very small but their flattened shape gives a relatively large surface area which allows rapid diffusion of oxygen.

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Structure of blood and blood vessels - Cardiovascular system - Edexcel - GCSE Physical Education Revision - Edexcel - BBC Bitesize

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1 2 3 4 Page 2of 4 Blood is carried through three different types of blood vessels in the body: arteries capillaries veins All blood vessels are specifically structured to perform their function.

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blood vessel, a vessel in the human or animal body in which blood circulates. The vessels that carry blood away from the heart are called arteries, and their very small branches are arterioles. Very small branches that collect the blood from the various organs and parts are called venules, and they unite to form veins, which return the blood to the heart. Capillaries are minute thin-walled vessels that connect the arterioles and venules; it is through the capillaries that nutrients and wastes are exchanged between the blood and body tissues.

The inner surface of every blood vessel is lined by a thin layer of cells known as the endothelium. The endothelium is separated from the tough external layers of the vessel by the basal lamina, an extracellular matrix produced by surrounding epithelial cells. The endothelium plays a critical role in controlling the passage of substances, including nutrients and waste products, to and from the blood. Under certain circumstances, tissues may grow new blood vessels, a process known as angiogenesis. Angiogenesis plays an important role in the replacement of damaged tissue but also occurs under abnormal conditions, such as in tumour growth and progression.

In humans, the function and structure of blood vessels can be affected by a number of different diseases and conditions. Some examples include inflammation; atherosclerosis, which involves the deposition of fat in the arterial endothelium; and hypertension, in which narrowing of the arterioles causes an abnormal increase in blood pressure. See artery; capillary; vein; cardiovascular disease.

The Editors of Encyclopaedia Britannica Meg Matthias.

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Blood vessel | Definition, Anatomy, Function, & Types

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Blood vessel, a vessel in the human or animal body in which blood circulates. The vessels that carry blood away from the heart are called arteries. Veins are vessels that return blood to the heart. Learn more about the anatomy and types of blood vessels and the diseases that affect them.