The Circulatory System 37-1 BIO 1004 Flora

Functions of Circulatory System  Small Organisms vs. large organisms (multi- cellular)  Humans and other vertebrates have closed circulatory systems  Blood is enclosed in blood vessels  Human CS consists of blood vessels, heart, and blood that travels through them

The Heart  Located in the center of the thoracic cavity  Surrounding the heart is protective tissue called pericardium  The thick layer of muscle that makes up the heart is called myocardium  The contraction of the myocardium is what forces blood through the blood vessels

The Heart Cont.  Dividing the right side of the heart from the left side of the heart is a barrier called the septum  Prevents the mixing of oxygen poor and oxygen rich blood  On each side of the septum are two chambers  Atrium – upper chamber that receives the blood  Ventricle – pumps blood out of the heart * The heart contains two atria and two ventricles

The Heart

Circulation Through the Body  Heart functions as two separate pumps  Right side of the heart pumps blood from the heart to the lungs – called pulmonary circulation  Oxygen rich blood then flows into the left side of the heart and is pumped to the rest of the body – called systemic circulation

Circulation

Circulation Through the Heart The Process  Blood enters through right and left atria  As heart contracts, blood flows into the ventricles and then to body or lungs  Valves – prevent blood from having a reverse flow  When ventricles contract, the valves close preventing blood flow back into the atria  There are also valves at the exits of the ventricles that prevent blood from flowing back into the heart

Heart Beat  The contraction of the heart begins in a small group of cardiac muscle cells called the sinoatrial node/SA Node (located in right atrium)  Called the pacemaker because these cells set the pace for the heart by contracting  This signal is picked up by fibers called the atrioventricular node (AV node) and this allows the ventricles to contract

Blood Vessels  Blood leaving the left side of the heart is oxygen rich  The aorta carries oxygen rich blood from the heart to the body  3 types of blood vessels  Arteries  Capillaries  veins

Blood Vessels  Arteries – large vessels that carry blood from the heart to tissues in the body  Except for pulmonary – all arteries carry oxygen rich blood  Arteries have thick walls that allow for the high pressures of blood passing through these canals  Capillaries – smallest blood vessels  Nutrient transport, oxygen transport to tissues, and removal of waste products is done by the capillaries

Blood Vessels Cont.  Veins – carry oxygen poor blood back to the heart  Thick walls to withstand pressure  Lack of exercise will weaken vein walls causing them to stretch, thus weakening the valves causing blood to pool in the veins  Known as varicose veins

Blood Pressure  Force of blood on the artery walls is known as blood pressure  Pressure is measured with a sphygmomanometer  Systolic pressure – 1 st # - force felt in arteries when ventricles contract  Diastolic pressure – force felt in arteries when ventricles contract  Kidneys also help regulate blood pressure  Hormones cause kidneys to remove more water when blood pressure is too high  Reduces volume and reduces pressure

Diseases  Atherosclerosis – fatty deposits/plaque build up on the inner walls of the arteries  Often builds up in coronary arteries which bring oxygen rich blood back to heart, and then the heart cells will die from lack of oxygen  Blood clots can break free and travel to the brain and then cause blockage – known as a stroke  Brain cells die from lack of oxygen

Diseases Cont.  High blood pressure – known as hypertension  Weakens and damages heart and blood vessels  Increases risk of heart attack and stroke

Diet  Exercise  NO smoking  Low saturated fat  Watch cholesterol  Obesity causes heart to contract harder, thus wearing out heart faster