The Circulatory System Blood, Blood Vessels and the Heart C5: 5 types of Blood Vessels a. arteries b. arterioles c. veins d. venules e. capillaries Arteries Have thick, muscular walls so they are able to withstand the blood pressure coming from the heart Carry blood AWAY from the heart Elastic: handle change in blood volume after each ventricular contraction Arterioles Small arteries are called ARTERIOLES Not as elastic as arteries They relax causing the arteriole to dilate, resulting in the opposite effect: increase blood volume, decrease pressure Veins Carry blood TOWARDS heart Have a thin muscle layer Contain VALVES to help the blood return to the heart Small veins are called venules Valves in Veins there is not enough blood pressure to make the blood return all the way to the heart One-way valves and the skeletal muscles work together to squish the blood back heart Varicose Veins If the valves malfunction in the legs, a painful condition can result Called Varicose veins Allows blood to pool in the elastic veins, causing them to bulge Varicose veins in rectum are called hemorrhoids. Capillaries Connect the veins and arteries Site of gas exchange between blood and cells Oxygen, nutrients and water diffuse out of the blood and into the cells Carbon dioxide, wastes and water diffuse out of the cells and into the blood Capillaries have extremely thin walls for diffusion. Comparison of Blood vessels Most of the bp that came from the heart is lost when the blood travels through the capillaries That is why you need VALVES in your veins. C3: Your Heart – structure and function Mostly Muscle Beats about 65-75 times per minute Is comparable to two pumps joined together Has 4 chambers: Right Atrium, right ventricle Left Atrium, Left Ventricle Anatomy diagrams are labelled as if you are looking down on a patient (unless otherwise indicated) Therefore, the R.A. is the patient’s right – not yours! PIG HEART Structure of the Heart 4 One-Way-Valves between the atria and the ventricles on both sides = Atrioventricular valves at the exit of both ventricles = semi-lunar valves prevent blood from flowing backwards If one of your valves is defective, you might have a “heart murmur”. Top View (looking down) Chordae Tendineae Anchor AV valves on ventricles to prevent valves from inverting Chordae Tendineae Demonstrate the flow of blood from the aorta through the body and back to the left ventricle. good overview of circulation through heart, nodal control Flow of Blood through the heart Blood enters the R.atrium via the superior and inferior vena cava When the Atria contract, blood moves from the R.A. to the R.Ventricle, passing the AV valve as it goes The ventricles contract, and force the blood through the semi-lunar valve and out to the body via the AORTA Blood Flow Video Both atria fill and contract at the same time. Both ventricles will fill and contract at the same time occurs when the AV valves close. The second heart sound “dub” occurs when the other valves close. distinguish between systolic and diastolic pressures When the cardiac muscle contracts it is called Systole When the chamber relaxes it is called diastole the SA node, AV node, and Purkinje fibres Our heartbeat is INTRINSIC. SPECIAL TISSUE, called NODAL TISSUE, has characteristics of both nerve and muscle tissue, controls the heartbeat. There are TWO nodal regions in the heart: 1. SA (sinoatrial) NODE Located upper back wall of right atrium. INITIATES THE HEARTBEAT every 0.85 seconds to make the ATRIA CONTRACT. SA Node The SA node is called the “PACEMAKER” because it keeps the beat regular. ARTIFICIAL PACEMAKERs, will send out an electric signal every 0.85 seconds to stabilize the heart rate if the SA node doesn’t work. 2. AV (atrioventricular) NODE: SA Node AV Node Located base of the R.A. near the septum. When the pulse from SA Node reaches AV node, the AV node will send out a signal along conducting fibers called PURKINJE FIBERS. They take the message to the VENTRICLES, and cause them to contract. The contraction of the ventricles begins at the Purkinje base of theFibers heart and moves up like a wave. Video Clip autonomic regulation of the heartbeat Heart under involuntary control by the brain MEDULLA OBLANGATA, This center can increase or decrease the heart rate Various factors, such as stress, oxygen levels, and bp determine how the ANS will affect heart rate. distinguish between pulmonary and systemic circulation Heart Beat Heart in a Box Flow of Blood: Blood travels in 2 loops A. The Pulmonary system - goes from the heart to the lungs and back to the heart again Only place where deoxygenated blood is in ARTERIES, and oxygenated blood is in VEINS Superior Vena Cava Aorta Pulmonary artery Pulmonary Vein Inferior Vena Cava Review b. Systemic Circuit When L. ventricle pumps to push the blood to rest of body This ensures there is ample blood pressure for the blood to deliver it’s oxygen and nutrients to the cells The Coronary Arteries The heart does not use the blood inside the atria or ventricles to get it’s nutrients and oxygen Has own set of arteries and veins to supply oxygen and nutrients = coronary arteries Circulatory Review Circulatory rap Atherosclerosis Excess fat and cholesterol stick to the arteries, forming a PLAQUE Plugs up the arteries, restricting blood flow If the blood flow that is restricted is to the heart, a heart attack may occur Angioplasty – possible procedure if the blockage isn’t too severe Heart Attack When the cells of the heart do not get enough oxygen The severity of the attack depends on how bad the coronary artery blockage is, and how many heart cells die At first, the victim may suffer angina pectoris (radiating pain in the left arm). One cause of heart attack: Smoking Nicotine causes heart to pump faster Also causes some arteries to contract (get smaller) Puts unneeded strain on the heart muscle Coronary Bypass Surgery: segments of leg veins are grafted between the aorta and coronary vessels, in order to bypass a blockage. Two to four such bypasses may be performed in a single operation. e.g. three such grafts would be known as a “triple-bypass” operation. Coronary bypass, donor heart transplants, and artificial heart implantation (which don’t work yet!) are surgical methods that have been used for the treatment of heart attacks. More than 50% of all deaths in Canada & U.S. are due to hypertension (high blood pressure), stroke, and heart attack. Heart Attack: when portion of heart dies due to lack of oxygen. At first, the victim may suffer angina pectoris (radiating pain in the left arm). Death may result if immediate treatment not given. Some more nasty circulatory events: Thrombus: a stationary clot attached to an arterial wall. Slows the flow of blood. Embolus: a thrombus that has become dislodged and moves along with the blood. When the vessel narrows, the embolus gets stuck and entirely blocks the flow of blood in a small vessel. This is called an embolism. Stroke: when portion of brain dies due to lack of oxygen -- usually when arteriole bursts or is blocked by an embolism. Strokes usually cause death or paralysis.