Circulatory System By Alcy, Patrick, Henry, Matt

Circulatory Structure & Diagram - There are two main parts of the circulatory system: - The pulmonary circulation is a short loop from the heart to the lungs and back again. This is where deoxygenated blood is reoxygenated (3). - The systemic circulation sends blood from the heart to all other parts of the body (3). - The heart is the main organ, responsible for pumping blood throughout the body. - A system of blood vessels distributes oxygen-rich blood through arteries and sends oxygen-poor blood through the veins back to the heart for circulation again. - Arteries and veins meet at capillaries, where gas exchange occurs.

Heart Structure - Pericardium is a double-sac of tough, connective tissue, protects the heart and connects it to nearby structures (4). - A fluid in between its layers lubricates the heart during its perpetual twisting motions. - The bulk of the heart wall - the Myocardium - is made up of cardiac muscle and holds the structure together (4). The Myocardium acts as a skeleton on which contractile force is applied. - These cardiac muscles have their own coronary circulation. - Coronary arteries branch off the aorta. - Endothelium is a one-cell-thick epithelial sheet, and is a special tissue only located in the heart/blood vessels (4).

Heart Structure (continued) - The heart has four chambers that are enclosed by thick, muscular walls. - The heart lies between the lungs and just to the left of the middle of the chest cavity. - The bottom part of the heart is divided into two chambers called the right and left ventricles. - Right Ventricle: pumps blood into pulmonary circulation for the lungs (3). - Left Ventricle: left ventricle pumps blood into the systemic circulation through the aorta (3). - The upper part of the heart is made of two chambers called the right and left atria. - A wall called the interatrial septum divides right and left atria. - Right and left atria is separated from the ventricles by the atrioventricular valves.

Heart Diagram

Blood Vessels: Function FUNCTION Arteries: distributor of blood to extremities Arterioles: push blood to capillaries Capillaries: cellular respiration occurs here Venules: small diameter, de-oxygenated blood from capillaries (4) Veins: brings un-oxygenated blood to heart Heart: aorta pumps oxygen rich blood from lungs to rest of the body (4)

Blood Vessels: Structure ARTERY - large diameter Outer coat → elastic tissue → smooth muscle → elastic tissue → basement membrane → endothelium ARTERIOLE - small diameter Outer coat → smooth muscle rings → basement membrane → endothelium CAPILLARY - smallest diameter of blood vessels Basement membrane → endothelium VEIN - large diameter outer coat → smooth muscle elastic fibers → basement membrane → endothelium with a valve

Gas Exchange - Gas Exchange is most commonly viewed as the delivery of oxygen from the lungs into to the bloodstream, and the elimination of carbon dioxide from the bloodstream to lungs (2). - This occurs in the lungs between the alveoli and the capillaries which are located around the walls of the alveoli. The average adult has about 600 million alveoli giving a total surface area of about a tennis court (2). - The close proximity of the capillaries and the alveoli allow for oxygen and carbon dioxide to diffuse between the respiratory system and the bloodstream. - Then as soon as oxygen molecules attach to red blood cells, blood changes color from blue to red. - As this occurs, carbon dioxide molecules in the alveoli are sent out of the body with the next exhalation. - Capillaries also help facilitate the exchange of nutrients, waste, and hormones between blood and body cells (2).

Prevention of Gas Exchange in non-optimal places There are four features that are particularly important for gas to only be exchanged in the specific places that the body requires. -Capillaries are so thin that red blood cells can only move in single file, slowing down the blood flow to a degree where 98% of all dissolved oxygen is taken up by passing red blood cells. -The air sacs (alveoli) are moist with mucus so that gases can easily dissolve before diffusing (1). -The air sacs have a large capillary network so large volumes of gas can be exchanged in the appropriate manner (1). -Arteries are a lot thicker than capillaries with lots of muscle and elastic fibers that act as a wall hence preventing gas exchange from occurring (1).

Bibliography 1. Dugdale, David C. "Gas Exchange." Medlineplus. A.D.A.M, n.d. Web. 3 Nov "Gas Exchange." BBC News. BBC, n.d. Web. 3 Nov < Exchange." BBC News. BBC, n.d. Web. 3 Nov < 3. “Kids Health." Heart and Circulatory System. N.p., n.d. Web. 2 Nov Kids Health." Heart and Circulatory System. N.p., n.d. Web. 2 Nov < 4. Starr, Cecie, Ralph Taggart, and Lisa Starr. Biology: The Unity and Diversity of Life. Pacific Grove, CA: Brooks/Cole, Print.