BCMB 230 1st EditionExam # 3 Study Guide Lectures: 15 - 20 Lecture 15 (Oct 22)The cardiovascular system has three main components: the heart, blood vessels, and blood. The heart is used as a pump to move the blood through the blood vessels. The blood vessels are used as a pathway to transport blood throughout the body to and from the heart and helps regulate pressure and flow. Blood acts as a blood system that does the work; components of blood are specialized to perform a certain task.There are two main circulatory pathways of the cardiovascular system, meaning that the heart acts like two separate pumps. When talking about the heart, the right and left sides are critical to distinguish between due to the structural and physiological differences. In the pulmonary circuit, blood gets pumped out from the right side of the heart and goes into the lungs, and then comes back through the left side of the heart. In the systemic circuit, blood goes out the left side of the heart and then through a series of systemic pathways; blood comes back through the veins and into the right side of the heart. There is not just one systemic circuit but one for every tissue. An artery is a blood vessel that carries blood away from the heart. A vein is a blood vessel that carries blood toward the heart. Capillaries are small thin-walled vessels that interact with tissues and are where the exchange of gases occurs between blood and tissue.Blood is composed mostly of water but also contains red blood cells, plasma, leukocytes,and platelets. Red blood cells carry oxygen and carbon dioxide which is important for gas exchange. We can determine the hematocrit or percent volume of red blood cells in blood if we centrifuge it. This percentage is usually around 45%. Plasma is the fluid component of blood that has water, proteins, electrolytes, salt, sugar, amino acids, etc and composes slightly over half (about 55%) of the blood. Leukocytes are also known as white blood cells and are involved in the defense against disease, helping to provide immunity against sickness. Platelets are involved with clotting.The heart is a hollow organ that has four fluid filled chambers: two atria and two ventricles. Atria are smaller with thinner walls while ventricles are larger with thicker walls. The interventricular septum is the wall that separates the right and left sides of the ventricles. The left side generally has a thicker wall because the lefts side is the one that pushes blood all the way down to the toes; systematic pathways are more extensive. When looking at diagrams, typically “red” denotes oxygenated blood that has been to the lungs but has not yet reached the tissues yet. These are usually the arteries in the systemic circuit and the veins in the pulmonary circuit. Typically “blue” denotes deoxygenated blood is blood that has had oxygen removed by the tissue. These are usually the veins in the systemic circuit and arteries in the pulmonary circuit. This pattern is not always the same for all figures, however, so be sure to check.Valves are in the heart and blood vessels. They are used to prevent blood from flowing in the wrong direction. Valves are controlled through pressure and without muscle control. Therefore they do not use energy or resources. Valves have a cup-like shape which is called acusp. When blood pushes on the cusps in the right direction, it opens the pathway up. However,if blood pushes on it in the opposite direction, the blood catches in the cups and causes the door to close. There are two types of valves: the atrioventricular valves and the semilunar valves. The atrioventircular (or AV) valves are located between the atrium and the ventricle, allowing blood to move from the atria to the ventricles. There are two types of AV valves. The tricuspid has three cusps and is found on the right side of the heart. The bicuspid has two cuspsand is found on the left side of the heart. The semilunar valves are in the main arteries leaving the heart. There are two types of semilunar valves. The pulmonary semilunar valves open the pathway to the pulmonary pathway and are in the pulmonary trunk leading to the lungs. The aortic semilunar valves open the pathway to the systemic pathway and are in the aorta leading to the body.There are three veins that dump blood into the right atrium. The vena cava consists of the main veins that bring blood to the systemic pathways. The superior vena cava brings blood from vessels mostly above the heart (toward the head). There is also the inferior vena cava thatbrings blood vessels from below the heart. The coronary sinus is a small vein from the heart itself that, like both sides of the vena cava, bring blood into the right atrium. After right atrium, blood flows through the tricuspid valve into the right ventricle. It leaves through the pulmonary semilunar valve which then takes it to large artery called the pulmonary trunk (trunk denotes a shortcut). This almost immediately divides into left and right pulmonary arteries which take us to the lung capillaries (which carries deoxygenated blood from heart to lungs). It then travels through the pulmonary veins into the left atrium, passes through the bicuspid valve into the left ventricle. Then it passes into the aortic semilunar valve into the aorta (the main artery for the systemic system) which goes into systemic capillaries eventually leading back into the vena cava through the veins (superior, inferior, or coronary sinus). When the heart contracts, the right and left ventricles contract simultaneously. Because of this, blood is moved into both the pulmonarytrunk and the aorta semilunar valve simultaneously as well.All four valves are in a line, separating the heart into two separate electrical components. The electrical signal is stopped by these valves—called the cardiac skeleton. Cardiac muscle has a lot of gap junction (similar to single unit smooth muscle) while connective tissue does not. All atria are going to be very connected which makes it easier for them to be very coordinated with each other. Atria can be operated independent of ventricles because of the layer of connective tissue. This is significant because we don’t want them to contract at the same time but first the atria and then the ventricles. When squeezing blood out, we want the atria to contract starting at the top of the heart going to the bottom and pushing blood down into the ventricles. We want the ventricles to contract