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Table of Contents
Cardiac Infarction: current concepts in diagnosis and dilatation/ stenting therapy
Topic 7 - Team J - Dibyasree Biswas, Joy Rakshit, Sidharth Thambiraj, Sumeet Yogeshwar Dekate
The Cardiovascular System
The cardiovascular system (CVS) is a complex arrangement of hydraulic systems. It is also known by other names such as circulatory system or the blood-vascular system. This system comprises mainly of 3 parts: the heart , the blood vessels and the blood. The heart is considered as the main pumping machine of blood and the blood vessels act as the delivery routes. The cardinal task of the CVS is to transport oxygen, carbon dioxide, numerous chemical compounds, and the blood cells via these media. There are various mechanisms which helps in maintaining and operating the cardiovascular system. These mechanisms make sure that there is a constant blood supply to every corner of the body depending on the demand and also an optimized internal environment around every cell independent of the demands for food or waste production.
Anatomy and physiology
Our heart is an incredible muscular organ subjected to an immense physical task more than any other muscle in our body over the lifetime. Everyday, the average human heart beats about 100,000 times, pumping 2,000 gallons of blood through the body. Now that is really phenomenal considering being only the size of the fist and weighing approximately 10-12 ounces!
In the human body, the heart is situated between the lungs, slightly towards the left of the center. The heart can be divided into two parts, the right and left parts. Furthermore, each part has two chambers, namely the right atrium and right ventricle and the left atrium and left ventricle. A muscle called Septum separates the right atrium and right ventricle from the left atrium and left ventricle. The upper part of the heart is attached to three major blood vessels: a) superior vena cava, b) aorta and c) pulmonary artery.
The heart consist of four valves and each of these valves allow the blood to flow only in one direction. A short description is given below:
- The Tricuspid valve / Right atrioventricular valve: it lies between the right atrium and the ventricle. It consists of three flaps. It stops the return flow of blood from the right ventricle to the right atrium.
- Bicuspid valve /Mitral valve/ Left atrioventricular valve: It lies between left atrium and left ventricle. The valve has two flaps It stops the return flow of blood from the left ventricle to the left atrium.
- Pulmonary valve: It can be seen at the right ventricle. It consists of three half-moon-shaped cusps. This does not allow blood to come back to the right ventricle.
- Aortic valve: It lies between the left ventricle and aorta. Its construction is similar to the pulmonary valve. This valve prevents the backward blood flow to the left ventricle from the aorta.
The blood is transferred to the various body-parts through blood vessels. There are three types of blood vessels:
- Arteries: It is thick-walled and carries the oxygenated blood away from the heart.
- Veins: These are thin-walled and carry deoxygenated blood towards the heart.
- Capillaries: These are the smallest and the last level of blood vessels.
The wall of the heart consists of three layers of tissue:
- Epicardium : connective tissue to provide protection.
- Myocardium : also known as the cardiac muscles, comprises core tissues of the walls of the heart.
- Endocardium: provides protection to valves and chambers inside the heart.
The heart pumps blood that travels throughout the body. In order to achieve this successfully, the heart muscles need to have a perfect coordination, pumping blood at the correct time, direction and pressure.
The cardiac cycle:
- The top right atrium (Sinoatrial, SA node) generates electrical impulse (given by purple shade)
- Both the right and left atria contracts by receiving this impulse, thus pushing the blood down into the ventricles via Atrioventricular (AV) node
- The signal is slowed down at AV node to avoid the contraction of atria and ventricle at the same time
- From there on the impulse is carried on to the ventricles causing them to contract
These electrical activities of the heart can be detected by an instrument called electrocardiograph and recorded on a graph paper with wave-like patterns called the electrocardiogram (ECG). Any atypical pattern if detected can be due to fluctuations in the electricity spread, resulting in different forms of arrhythmias (abnormal heartbeat).
Aorta and main arteries
The aorta is the prime and largest artery in fact the largest blood vessel in the human body. It originates from the left ventricle of the heart and runs down to the abdomen and there, it bifurcates into two smaller arteries, the common iliac arteries. The aorta supplies oxygenated blood to the circulatory system. The other arteries related to the heart are coronary arteries namely (1) Left main coronary artery (LMCA) and (2) Right coronary artery (RCA).
1. Left main coronary artery (LMCA): The left prime coronary artery which supplies blood to the left heart muscle which is the left ventricle and left atrium. The LCMA is further divided into branches:
a. The left anterior descending artery: It originates from the left coronary artery and supplies blood to the front of the left side of the heart.
b. The circumflex artery: It originates from the left coronary artery and encircles the heart muscle. This artery supplies blood to the outer side and back of the heart.
2. Right coronary artery (RCA): The task of the right coronary artery is to supply blood to the right ventricle, the right atrium and the sinoatrial (SA) and atrioventricular (AV) nodes, which controls the heart rhythm. Again, the RCA bifurcates into smaller branches which are the right posterior descending artery and the acute marginal artery. Unlike the left anterior descending artery, the right coronary artery supplies blood to the middle or septum of the heart.
Venous system and blood supply to and from the lung
The deoxygenated blood reaches the heart via superior vena cava and inferior vena cava and pours the blood to the right atrium, and then the blood is pumped into the right ventricle. The ventricle then pumps it into the pulmonary arteries. The pulmonary arteries carry the deoxygenated blood into the lungs for oxygenation. The blood is oxygenated inside the lungs with the help of Dalton's principle of gas transfer. The blood capillaries are set in between alveoli. During inhalation, the lungs sucks in O2 and carry it to alveoli and the O2 is then transferred to the blood in capillaries and hence the blood is oxygenated. Then the oxygenated blood is carried in pulmonary veins and carried to the left atrium of the heart. And then it is transferred to the left ventricle and then pumped to the aorta. The aorta supplies blood to the rest of the body.