HESI A2 Exam: Cardiovascular System
The Heart
The four muscular chambers of the heart are the right and left atria and the right and left ventricles.
The left ventricle pumps blood to the body and the right ventricle pumps blood to the lungs.
The atria receive blood returning to the heart and the ventricles collect and expel blood from the heart.
Atrioventricular valves separate the atria and ventricles.
The tricuspid valve separates the right atrium and the right ventricle.
The mitral valve separates the left atrium and the left ventricle.
Blood Vessels
Blood outside the heart travels through the blood vessels. The three major types of blood vessels are arteries, capillaries, and veins.
Arteries are strong and elastic and prepared for the high pressure of blood as it leaves the heart.
The aorta is the largest artery in the body and carries blood away from your heart and to the rest of your body.
The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs (not the heart).
Oxygenated blood leaves the heart via the aorta and travels through a network of arterioles to arrive at the capillary beds.
Smaller arteries (arterioles) supply blood to the capillaries, which facilitate the exchange of oxygen and carbon dioxide. The capillaries are any of the minute blood vessels that form networks throughout the bodily tissues; it is through the capillaries that oxygen, nutrients, and wastes are exchanged between the blood and the tissues. The capillary networks are the ultimate destination of arterial blood from the heart and are the starting point for flow of venous blood back to the heart.
Veins
Veins carry blood back to the heart.
Venules carry blood away from the capillaries back to the veins and eventually back to the heart.
The vena cava brings deoxygenated blood back to the heart. The vena cava is also the largest vein in the body.
Pulmonary veins carry oxygenated (as opposed to deoxygenated) blood and bring blood from the lungs to the heart.
The superior and inferior venae cavae, as well as right and left pulmonary veins, are vessels that return blood to the heart.
Blood
Blood is an essential bodily fluid that transports oxygen and nutrients to the tissues and removes waste products, including carbon dioxide and ammonia. The four main components of human blood are red blood cells, white blood cells, platelets and plasma.
Plasma is a liquid component of blood and accounts for about half of the blood volume.
Red blood cells account for the second greatest component of blood by volume. The functional unit of red blood cells is hemoglobin. Hemoglobin is an iron containing protein that facilitates gas exchange by binding to either oxygen or carbon dioxide.
Sickle cell trait involves red blood cells that are irregularly shaped.
White blood cells are part of the body's immune response and remove pathogens from the blood. Lymphocytes, a type of white blood cell, release antibodies in response to disease and enable other immune system responses.
Platelets prevent bleeding by developing blood clots. They work with coagulating proteins to stick to vessel walls (and to each other).
Circulation
The systemic circuit carries oxygenated blood away from the left ventricle of the heart and returns deoxygenated blood to the right atrium.
The pulmonary circuit contains the blood vessels that carry blood to and from the lungs.
The lymphatic system drains toxins and wastes from body tissues and removes foreign entities from circulation.
Flow of Blood
From the left ventricle, blood flows to the aorta, then through the arteries and capillaries, and then returns to the heart via the vena cava, at which point it enters the right atrium. It flows from the right atrium to the right ventricle, then through the pulmonary artery to the lungs, and finally returns to the left atrium by way of the pulmonary vein.
Cardiovascular Regulation
The cardiovascular system orchestrates the movement of blood and lymph.
Systole involves contraction that forces blood to move either into another heart chamber or into an artery.
Atrial systole involves blood moving into the relaxed ventricles.
During ventricular systole, once the pressure of contraction opens the semilunar valves, blood is pumped into either the aorta or pulmonary artery.
During diastole, the heart muscle relaxes and the chambers are passively filled with blood. The backflow of blood into the chambers would be a sign of weakened heart valves, such as in the case of congestive heart failure.
The medulla oblongata regulates cardiac output. It signals a decrease in cardiac output when blood pressure increases and an increase in cardiac output when blood pressure decreases. This is saying that with increased blood pressure, the oblongata will tell the heart to beat slower and with decreased blood pressure heart rate will increase.