The Heart and Cardiovascular
Pericardium...
Between the epicardium and the pericardium is a space called the called the PERICARDIAL SPACE, or PERICARDIAL CAVITY. The pericardium is a serous membrane, secreting a thin, slippery fluid into the pericardial space. The pericardial fluid lubricates the membranes and allows them to slide past one another with very little friction.
Atrioventricular valves...
Entrance valves. Located between atria and ventricles on both sides of the heart. Have cusps or flaps. When the ventricles are relaxed, the cusps hang loosely. In this position the valves are open and permit the flow of blood from the atria into the ventricles. When the ventricles contact, the muscle compresses and squeezes the blood in the ventricles. The blood pushes the cups upward toward the atria into a closed position. The closed AV valves prevent the backward flow of blood from the ventricles to the atria. The cusps are attached to the ventricular wall by tough fibrous bands of tissue called CHORDAE TENDINAE. As blood pushes the cusps into a closed position, the chordae tendineae are stretched to their full length. They hold onto the cusps and prevent from the "blowing" through into the atria. The right AV valve is called the TRICUSPID VALVE - it has cusps. The left AV valve called the BICUSPID VALVE it had 2 cusps. The left AV valve is also called the MITRAL VALVE.
Left ventricle...
Receives oxygenated blood from the left atrium. Primary function: to pump blood into the systemic circulation. Blood leaves through the aorta - largest artery of the body. Notice the thickness of the myocardial layer of the ventricles. This thick muscle is needed to generate enough force to pump blood out of the heart. Notice that the left ventricular myocardium is thicker than the right. This is due to the greater amount of force required to pump blood into the systemic circulation.
Right ventricle...
Receives unoxygenated blood from the right atrium. Pump it to the lungs through the pulmonary artery. The pulmonary artery divides into right and left branches to carry the blood to both right and left lungs.
Semilunar valves...
2 semilunar valves are exit valves. Pulmonic valve (PULMONARY VALVE, RIGHT SEMILUNAR VALVE) - located between the right ventricle and the pulmonary artery. When the right ventricle relaxes, the valve is closed. When the right ventricle contracts, look forced the pulmonic valve open. Blood flows through the open valve in the pulmonary artery to the lungs. When the ventricle relaxes the pulmonic valve snaps close. The AORTIC VALVE or the LEFT SEMILUNAR VALVE is located between the left ventricle and the aorta. It works in the same way- when the left ventricle contacts, blood is forced into the aorta. It snaps close when the ventricle relaxes. How do semilunar valves close? They close when the pressure in the ventricles becomes less than that in the vessels - it sucks the valves close - back pressure like you see in an empty shampoo bottle.
Right atrium...
A thin walled cavity. Receives unoxygenated blood (blue) from: Superior vena cava - collects blood from the head, upper body region. Inferior vena cava - receives blood from the lower part of the body.
Blood supply to the myocardium...
Although blood constantly flows through the heart, this blood does NOT nourish the myocardium. The blood supply that nourishes and oxygenated the myocardium is provided by the myocardium CORONARY ARTERIES. The CORONARY VEINS collect the blood that nourishes the myocardium. The blood then travels to the CORONARY SINUS where it empties into the right atrium. The myocardium depends on a constant supply of oxygenated blood. If this blood supply is interrupted even for a short period of time, the myocardium can be damaged. If a blood clot (thrombosis) occludes (blocks) a coronary artery, myocardial cell death occurs. This even is a MYOCARDIAL INTERACTION (MI), of a HEART ATTACK.
Heart sounds...
The "heart beat" we hear is made by the vibrations caused by the closure of the valves. We hear "lubb-dubb" The first sound "lubb" is due to the closure of the AV valves. The second Heart sound "dubb" is due to the closure of the semilunar valves. When the valves become faulty, the heart sounds change. Abnormal heart sounds are called MURMURS.
The Heart's Layers and Coverings...
The Heart is made up of 3 layers of tissue: ENDOCARDIUM, MYOCARDIUM, and EPICARDIUM.
The heart's chambers and large vessels...
The heart has 4 chambers: 2 atria and 2 ventricles. The ATRIA (singular ATRIUM) receive the blood - the upper chambers.
Structure of the Heart: What it is...
The heart is a hollow, muscular organ, made up of cardiac muscle. Its primary function: to pump and force blood through the blood vessels of the body, providing every cell in the blood with vital nutrients and oxygen. The heart pumps an average of 72 times each minute for your entire lifetime. If you live to be 75, your heart will be in excess of 3 billion times. The adult heart is about the size of a closed fist. It sits in the chest with in the mediastinum the space between the 2 lungs. It lies toward the left side of the body. 2/3 of the Heart is located to the left of the midline of the sternum. The Heart is located between ribs #2-#5. The lower, more pointed end of the Heart is called the APEX. The Heart lies within and is supported by a sling-like structure called the PERICARDIUM. The PERICARDIUM attaches the Heart to surround structures such as the ....
A double pump into circulations...
The myocardium enables the heart to pump blood (made of cardiac muscle). The heart is like a DOUBLE PUMP - or two pumps that beat as one. The pumps are the RIGHT HEART and the LEFT HEART. The right heart receives unoxygenated blood from the superior and inferior vena cavae -large veins that collects blood from all parts of the body. The right heart is always color blue because it contains unoxygenated. The pumps blood to the lungs where the blood oxygenated. The path that the blood follows from the right side of the heart to and through the lungs and back to the left side of the heart is called the PULMONARY CIRCULATION. The only function of pulmonary circulation is to load the blood with oxygen and unload carbon dioxide. This happens by DIFFUSION. The left side of the heart receives the oxygenated blood from the lungs and pumps it to all the organs of the body. The left side of the heart is always colored red because it contains oxygenated blood. The path that the blood follows from the left side of the heart to all the organs of the body and back to the right heart is called SYSTEMIC CIRCULATION.
Heart valves...
The purpose of the heart valves is to keep the blood flowing in a FORWARD DIRECTION The four heart valves lie at the entrance and exit of the ventricles.
Epicardium...
The thin outermost layer. Consists of epithelial and connective tissues.
What happens when your heart valve becomes leaky?
The valve allows blood to leak back into the chamber from which it has just been pumped. The blood is allowed to flow in the wrong direction. This increases the workload of the Heart and causes other serious problems.
Myocardium...
Thick middle layer. Composed of cardiac muscle. Allows the Heart to contract, forcing blood through the blood vessels.
Left atrium...
Thin walled cavity that receives oxygenated (red) blood from the lungs through 4 pulmonary veins.
Endocardium...
Thin, innermost layer. Composed of simple squamous epithelium overlying a layer of connective tissue. The smooth, shiny surface allows blood to flow over it easily. Also forms the inner lining of blood vessels that enter and leave Heart.
