BI0005 - Lecture 10 - The Heart
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What is the inferior vena cava?
The inferior vena cava (or IVC), also known as the posterior vena cava, is the large vein that carries deoxygenated blood from the lower half of the body into the right atrium of the heart.
What is the superior vena cava?
The superior vena cava (also known as the cava or cva) is a large diameter, yet short, vein that carries deoxygenated blood from the upper half of the body to the heart's right atrium.
What is the right atrium?
- The right atrium is one of four chambers (two atria and two ventricles) in the hearts of mammals (including humans) and archosaurs (which include birds and crocodilians).
- It receives deoxygenated blood from the superior and inferior venae cavae, and pumps it into the right ventricle through the tricuspid valve.
What is the aortic valve?
The aortic valve is one of the four valves of the heart. It normally has three leaflets. It lies between the left ventricle and the aorta.
What is the tricuspid valve?
The tricuspid valve, or right atrioventricular valve, is on the right dorsal side of the mammalian heart, between the right atrium and the right ventricle. The function of the valve is to prevent back flow of blood into the right atrium.
What is the right ventricle?
- The right ventricle is one of four chambers (two atria and two ventricles) in the human heart.
- It receives deoxygenated blood from the right atrium via the tricuspid valve, and pumps it into the pulmonary artery via the pulmonary valve and pulmonary trunk.
What is the left atrium?
- The left atrium is one of four chambers in the human heart.
- It receives oxygenated blood from the pulmonary veins, and pumps it into the left ventricle, via the mitral valve.
What is the left ventricle?
- The left ventricle is one of four chambers (two atria and two ventricles) in the human heart.
- It receives oxygenated blood from the left atrium via the mitral valve, and pumps it into the aorta via the aortic valve.
what are the papillary muscles?
In anatomy, the papillary muscles are muscles located in the ventricles of the heart. They attach to the cusps of the atrioventricular valves (a.k.a. the mitral and tricuspidvalves) and contract to prevent inversion or prolapse of these valves.
What are the cordae tendineae?
The chordae tendineae (tendinous chords), or heart strings, are cord-like tendons that connect the papillary muscles to the tricuspid valve and the mitral valvein the heart.
What is the bicuspid / mitral valve?
The mitral valve (also known as the bicuspid valve or left atrioventricular valve) is a dual-flap valve in the heart that lies between the left atrium (LA) and the left ventricle (LV).
The mitral valve and the tricuspid valve are known collectively as the atrioventricular valves because they lie between the atria and the ventricles of the heart and control the flow of blood.
During diastole, a normally-functioning mitral valve opens as a result of increased pressure from the left atrium as it fills with blood (preloading).
As atrial pressure increases above that of the left ventricle, the mitral valve opens. Opening facilitates the passive flow of blood into the left ventricle.
What is the pulmonary vein?
- The pulmonary veins are large blood vessels that receive oxygenated blood from the lungs and drain into the left atrium of the heart.
- There are four pulmonary veins, two from each lung.
- The pulmonary veins are among the few veins that carry oxygenated blood.
What are the pulmonary arteries?
The pulmonary artery carries deoxygenated blood from the heart to the lungs. It is one of the only arteries (other than the umbilical arteries in the fetus) that carry deoxygenated blood.
What is the pulmonary semilunar valve?
- These are located at the base of both the pulmonary trunk (pulmonary artery) and the aorta, the two arteries taking blood out of the ventricles.
- These valves permit blood to be forced into the arteries, but prevent backflow of blood from the arteries into the ventricles.
- These valves do not have chordae tendineae, and are more similar to valves in veins than atrioventricular valves.
- Closure of the semilunar valves causes the second heart sound.
What is the aorta?
- The aorta is the largest artery in the human body, originating from the left ventricle of the heart and extending down to the abdomen, where it bifurcates into two smaller arteries (the common iliac arteries).
- The aorta distributes oxygenated blood to all parts of the body through the systemic circulation
What is the cardiac cycle?
What is the systole and diastole?
- One complete sequence of pumping and filling of the heart is referred to as the cardiac cycle.
- The contraction phase is called systol, and the relaxation phase is called diastol.
What is the cardiac output, and what determines it?
- The volume of blood each ventricle pumps per minute is the cardiac output.
- Two factors determine cardiac output: the rate of contraction, or heart rate (number of beats per minute), and the stroke volume, the amount of blood pumped by a ventricle in a single contraction.
What is the average stroke volume, heart rate, and cardiac output of a human being?
- The average stroke volume in humans is about 70mL.
- Multiplying this stroke volume by a resting heart rate of 72 beats per minute yeilds a cardiac output of 5L/min - about equal to the total volume of blood in the human body.
- During heavy exercise, cardiac output increases as much as fivefold.
What are the steps of mammalian circulation?
- 1. Contraction of the right ventricle pumps blood to the lungs via the pulmonary arteries.
- 2. As the blood flows through capillary beds in the left and right lungs, it loads O2 and unloads CO2.
- 3. Oxygen rich blood returns from the lungs via the pulmonary veins to the left atrium of the heart.
- 4. Next, oxygen-rich blood flows into the left ventricle, which pumps the oxygen-rich blood out to body tissues through the systematic circuit.
- 5. Blood leaves the left ventricle via the aorta, which conveys blood to arteries leading thoughout the body.
- 6. The first branches from the aorta are the coronary arteris, whch supply blood to the heart muscle itself.
- 7. Then branches lead to capillary bends in the head and arms.
- 8. The aorta then descends into the abdomen, supplying oxygen-rich blood to arteries leading to capillary beds in the abdominal organs and legs (hind limbs).
- 9. Within the capillaries, there is a net diffusion of O2 from the blood to the tissues and of CO2 produced by cellular respiration into the blood.
- 10. Capillares rejoin, forming venules, which convey blood to veins.
- 11. Oxygen-poor blood from the head, neck, and forlimbs is channeled into a large vein, the superior vena cava.
- 12. Another large vein, the inferior vena cava, drains blood from the trunk and hind limb.
- 13. The two venae cavae empty their blood into the right atrium, from which the oxygen-poor blood flows into the right ventricle.
What does it mean that cardiac muscle are autorhythmic?
Some cardiac muscle cells are autorhythmic, meaning they contract and relax repeatedly without any signal from the nervous system.
How is the heart autoryhthmic?
The answer lies in a group of autorhythmic cells located in the wall of the right atrium, near where the superior vena cava enters the heart.
This cluster of cells is called the sinoatrial (SA) node, or pacemaker, and it sets the rate and timing at which all cardiac muscle cells contract.
How to the sinoatrial node work?
The SA node generates elecrical impulses much like those produced by nerve cells.
Because cardiac muscle cells are electrically coupled through gap junctions, impulses from the SA node spread rapidly within heart tissue.
In addition, these impulses generate currents that are conducted to the skin via body fluids.
What is an ECG or EKG?
A medical test called an electrocardiogram, which uses electrodes place on the kin to detect the currents produced by the hear which are conducted to the skin via body fluids.
The resulting graph has a characteristic shape that represents the stages in the cardiac cycle.
What is the atrioventricular node?
They are other autorhythmic cells, located in the wall between the left and right atria.
How do pacemaker impulses cause contraction of the heart?
Impulses from the SA node first pread rapidly through the walls of the atria, causing both atria to contract in unison.
During atrial contraction, the impulses originating at the SA node reach other autorhythmic cells that are located in the wall between the left and right atria.
These cells form a relay point called the atrioventricular (AV) node.
Here the impulses are delayed for about 0.1 second before spreading to the walls of the ventricles.
This delay allows the atria to empty completely before the ventricles contract.
Then, the signals from the AV node are conducted throughout the ventricular walls by specialized muscle fibers called bundle branches and Purkinje fibers.
What are the different parts of an ECG?
P wave - Atria depolarise prior to contraction.
QRS complex - Ventricular depolarisation
T wave - Ventricular repolarization
What warning signals are there for heart attacks - Leading causes of death in England and Wales.
Uncomfortable pressure, fullness, squeezing or pain in the centre of the chest lasting more than a few minutes.
Pain spreading to the shoulders, neck or arms. The pain may be mild to intense. It may feel like pressure, tightness, burning, or heavy weight. It may be located in the chest, upper abdomen, neck, jaw, or inside the arms or shoulders.
Chest discomfort with lightheadedness, fainting, sweating, nausea or shortness of breath.
Anxiety, nervousness and/or cold, sweaty skin.
Paleness or pallor.
Increased or irregular heart rate.
Feeling of impending doom
What is atherosclerosis?
Atherosclerosis (also known as arteriosclerotic vascular disease or ASVD) is a specific form of arteriosclerosis in which an artery wall thickens as a result of the accumulation of calcium and fatty materials such as cholesterol and triglyceride.
It reduces the elasticity of the artery walls and therefore allows less blood to travel through.
This also increases blood pressure.
What is angina?
Angina pectoris – commonly known as angina – is chest pain due to ischemia of the heart muscle, due in general to obstruction or spasm of the coronary arteries.
What is ischemia?
In medicine, ischemia, is a restriction in blood supply to tissues, causing a shortage of oxygen and glucose needed for cellular metabolism (to keep tissue alive)
What is acute myocardial infarction ?
Myocardial infarction, or acute myocardial infarction (AMI) is the medical term for an event commonly known as a heart attack.
It happens when blood stops flowing properly to part of the heart and the heart muscle is injured due to not receiving enough oxygen.
Usually this is because one of the coronary arteries that supplies blood to the heart develops a blockage due to an unstable buildupof white blood cells, cholesterol and fat.
The event is called "acute" if it is sudden and serious.
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