Anatomy of the Cardiovascular System Flashcards
Describe the organisation and function of the cardiovascular system
It’s a a closed, tubular organ system conveying blood to and from all parts of the body, using the heart for propulsion. It uses different types of vessels to carry the blood. The blood is used to transport O2 and CO2, nutrients, and waste products. It consists of pulmonary and systemic circulations
Describe the path of the blood, in reference to the vessels it travels through
The blood is pumped from the heart into the arteries at high pressure. The arteries branch out and eventually terminate in short muscular arterioles, and eventually end up in capillaries where exchange takes place. By this point, the blood has slowed down and is under less pressure, where it enters venules, then veins, and ends up back at the heart
Describe the structure of the heart
The heart is a muscular pump which provides the force necessary to circulate blood to all the tissues of the body. Pumps about 5L/min. It’s a 4 chambered muscle which is enclosed in a pericardial sac (double walled membranous sac) that’s lined by the parietal layers of a serous membrane. The visceral layers make up the epicardium. The next layer of the heart wall is the myocardium which is the thick muscular part, and then the endocardium.
Describe the position and function of the valves of the heart
The heart has valves to prevent the backflow of blood in circulation. There are 2 types of valve in the heart. Atrioventricular (cuspid) valves are between atria and ventricles. Bicuspid valve AKA mitral valve. Semilunar valves are at the base of large vessels leaving the ventricle. Semilunar are aortic and pulmonary valves
Describe the path of blood through the heart and the rest of the circulatory system
Blood flows from the right atrium to the right ventricle, and is then pumped to the lungs for oxygenation. From the lungs, blood flows into the left atrium, down into the left ventricle, and is then pumped to the rest of the body. It goes through the arteries, then the arterioles, then the capillaries, then the venules, then veins, which end up in the super/inferior vena cava and eventually end up in the right atrium. The coronary arteries branch from the ascending aorta, and the brain is supplied by the internal carotid and vertebral arteries.
Describe the blood supply to the myocardium
The myocardium is a working muscle - it needs constant O2 and nutrient supply. For this reason, the cardiac muscle has an extensive capillary network. The right and left coronary arteries (branching off the ascending aorta) supply the myocardium. After the blood passes through the myocardial capillary network, it enters the cardiac (coronary) vein system which drains into the right atrium via the coronary sinus
Explain the structure and function of the arterial system
The arteries carry blood away from the heart under high pressure. For this reason they need to be thick walled. The blood is pumped into large elastic arteries which branch into smaller and smaller vessels until microscopic arterioles are reached. These arterioles play an important role in regulating blood flow into tissue capillaries
Explain the structure and function of the capillaries
The capillaries are the most numerous and smallest blood vessels. They form the connection between the arteries and veins. They are extremely thin walled to facilitate gas and nutrient exchange - their primary function. Gas exchange occurs via diffusion. Fluid exchange is determined by osmotic and hydrostatic pressure. The microcirculation causes substances to leave the capillaries at one end and return at the other end
Explain the structure and function of the venous system
The veins carry blood towards the heart. After flowing through the capillary system, the blood enters the venules, and through larger and larger veins until it reaches the heart. Veins are thinner than arteries because they don’t have to withstand as high pressures as arteries do. They have the same 3 layers but less smooth muscle and connective tissue. Medium and large veins have valves which prevent backflow, this is especially important in the arms and legs where backflow is a gravitational response
Why are there modifications to the fetal blood system?
Because the fetus relies on the mother for gaseous exchange and nutrients. It doesn’t have functional lungs, gi, or kidney so no need for a full blood supply reaching every organ
Describe and explain the functions of the four modifications to the adult circulatory system to give the fetal circulatory system
Foramen Ovale - hole in the septum which allows the blood to bypass the lungs
Ductus Arteriosus - Connects main pulmonary artery to the proximal descending aorta, allowing the blood to bypass the lungs
Ductus Venosus - Connects umbilical vein to vena cava, allowing blood to bypass the liver
Umbilical vein/arteries - Carries fetal blood to the placenta and rich blood from the placenta to the fetus
Describe the fetal circulatory path
Maternal blood arrives at placenta, and exchanges with the fetal blood from the umbilical arteries. The umbilical vein carries this super rich blood towards the heart and the ductus venosus allows the blood to drop off some nutrients at the liver but mostly bypasses it. Deoxygenated blood from the body joins the rich blood in the vena cava, becoming partially oxygenated. This partially oxygenated blood enters the heart via right atrium. It goes down into the right atrium and is pumped to the lungs where it mostly bypasses them via the ductus arteriosus. Also, the foramen ovale allows most of the blood to go through to the left atrium, where it meets the blood coming from the lungs in the aorta where it goes to the rest of the tissues, and ends up in the umbilical arteries and back at the placenta
