The walls (outer structure) of The walls (outer structure) of veins Capillaries are tiny (extremely narrow) arteries contain smooth muscle consist of three layers of tissues that are blood vessels, of approximately 5-20 fibre that contract and relax under thinner and less elastic than the micro-metres the instructions of the sympathetic corresponding layers of aerteries. (one micro-metre = 0.000001metre) nervous system. Veins include valves that aid the return of diameter. blood to the heart by preventing blood There are networks of capillaries in most Transport blood away from the from flowing in the reverse direction. of the organs and tissues of the body. heart; These capillaries are supplied with blood Transport towards the heart; by arterioles and drained by venules. Carry Oxygenated Blood Carry De-oxygenated Blood Capillary walls are only one cell thick (see (except in the case of the (except in the case of the Pulmonary diagram), which permits exchanges of Pulmonary Artery); Vein); material between the contents of the capillary and the surrounding tissue Have relatively narrow lumens (see Have relatively wide lumens (see diagram diagram above); Function is to supply tissues with components of, and carried by, the blood, Have relatively more muscle/elastic Have relatively less muscle/elastic tissue; and also to remove waste from the tissue; Transports blood under lower pressure surrounding cells ... as opposed to simply Transports blood under higher (than arteries); moving the blood around the body (in the pressure (than veins); case of other blood vessels); Have valves throughout the main veins of Do not have valves (except for the the body. These are to prevent blood Exchange of oxygen, carbon dioxide, semi-lunar valves of the pulmonary flowing in the wrong direction, as this water, salts, etc., between the blood and artery and the aorta). could (in theory) return waste materials the surrounding body tissues. to the tissues.
The walls (outer structure) of arteries contain smooth muscle fibre that contract and relax under the instructions of the sympathetic nervous system. Transport blood away from the heart; Carry Oxygenated Blood (except in the case of the Pulmonary Artery); Have relatively narrow lumens (see diagram Have relatively more muscle/elastic tissue; Transports blood under higher pressure (than veins); Do not have valves (except for the semi-lunar valves of the pulmonary artery and the aorta). The walls (outer structure) of veins consist of three layers of tissues that are thinner and less elastic than the corresponding layers of aerteries. Veins include valves that aid the return of blood to the heart by preventing blood from flowing in the reverse direction. Transport towards the heart; Carry De-oxygenated Blood (except in the case of the Pulmonary Vein); Have relatively wide lumens (see diagram above); Have relatively less muscle/elastic tissue; Transports blood under lower pressure (than arteries); Have valves throughout the main veins of the body. These are to prevent blood flowing in the wrong direction, as this could (in theory) return waste materials to the tissues. Capillaries are tiny (extremely narrow) blood vessels, of approximately 5-20 micro-metres (one micro-metre = 0.000001metre) diameter. There are networks of capillaries in most of the organs and tissues of the body. These capillaries are supplied with blood by arterioles and drained by venules. Capillary walls are only one cell thick (see diagram), which permits exchanges of material between the contents of the capillary and the surrounding tissue Function is to supply tissues with components of, and carried by, the blood, and also to remove waste from the surrounding cells ... as opposed to simply moving the blood around the body (in the case of other blood vessels); Exchange of oxygen, carbon dioxide, water, salts, etc., between the blood and the surrounding body tissues.
Senior_Science_Resources_-_Circulatory_system_and_pharmaceuticals_work_booklet.docx