1. Blood vessels 11.3

3. Arteries The blood from the heart is carried through the body by a complex network of blood vessels Arteries take blood away from the heart The main artery is the aorta Aorta branches into other major arteries, which take blood to different limbs and organs

4. Arteries Carotid artery takes blood to the brain Brachial arteries take blood to the arms Thoracic artery take blood to the thorax and then into the hepatic, renal and gastric arteries for the liver, kidneys and stomach respectively Iliac artery takes blood to the lower limbs

5. Layers of the arteries The arteries have three layers of tissues: – An outer layer of connective tissues (stretches to support blood flow) – A middle layer of smooth muscles (regulate blood flow by altering vascular resistance by constriction and dilation) – A smooth inner single layer of epithelial cells called the endothelium

7. Pulse When blood is forced through the artery by the contraction of the heart, the artery expands The expansion can be felt as the pulse The artery has to be large, close to the skin and in front of a bone Do mini investigation page 488

9. Arterioles The major arteries diverge into minor arteries, and then into smaller vessels called arterioles Arterioles reach more deeply into the muscles and organs of the body Arterioles have smooth muscle in their wall, thus they can be controlled by the nervous system

10. Arterioles Signals from the nerves can regulate the diameter of the arterioles and control the blood flow to certain parts of the body – Vasodilation: an increase in the diameter of arterioles that increases the blood flow to tissues – Vasoconstriction: a decrease in the diameter of the arterioles that decreases the blood flow to tissues

11. Arterioles Vasoconstriction is an important feature of the circulatory system. Without it your body will need 200 L of blood to fill all the blood vessels The ability to control blood flow ensure that the 5 L of blood we have is distributed where it is needed

12. Capillaries Arterioles diverge into capillary beds Capillary beds contain 10 to 100 capillaries that branch among the cells and tissues of the body https://www.youtube.com/watch?v=Q530H1 WxtOw https://www.youtube.com/watch?v=Q530H1 WxtOw

13. Capillaries Capillaries are narrow diameter tubes Can fit blood cells in a single-file lines Supply oxygen and nutrients to every cell throughout the body tissues Carbon dioxide and other waste produced during aerobic cellular respiration diffuse into the tissue fluid and then into the capillaries

14. Fluid exchange High fluid concentration on the arterial side cause water to diffuse from the blood to the tissue fluid On the venous side, high concentration of water in the tissue fluid causes water to move from the tissue fluid to the blood This maintains a balance between the fluids in the circulatory system and the tissues

15. Controlling blood flow Page 489 https://www.youtube.com/watch?v=yeX0uDpPB j4

16. Venules and veins The capillaries connect the arteries to the veins On one side we have the arteries and arterioles carrying oxygenated blood and nutrients to the tissues On the other side the capillaries merge into small vessels called venules that merge to form large vessels called veins

17. Venules and veins Venules and veins carry deoxygenated blood containing carbon dioxide and other waste products from the tissues to the heart The middle layer of smooth muscle is not as thick as the arteries The walls in the veins are not as elastic as the arteries Blood pressure in veins are lower than in arteries

18. Venules and veins Veins have valves to prevent the backflow of blood Because veins have to work against gravity to get blood back to the heart, contraction of skeletal muscle assists with the flow of blood back to the heart https://www.youtube.com/watch?v=HNuPWd fjDoc https://www.youtube.com/watch?v=HNuPWd fjDoc

20. Blood pressure https://www.youtube.com/watch?v=qWti317 qb_w https://www.youtube.com/watch?v=qWti317 qb_w