00:00 / 00:00
Cardiovascular system anatomy and physiology
Lymphatic system anatomy and physiology
Abnormal heart sounds
Normal heart sounds
Changes in pressure-volume loops
Cardiac and vascular function curves
Altering cardiac and vascular function curves
Law of Laplace
Measuring cardiac output (Fick principle)
Stroke volume, ejection fraction, and cardiac output
Physiological changes during exercise
Cardiovascular changes during hemorrhage
Cardiovascular changes during postural change
Cardiac conduction velocity
Electrical conduction in the heart
ECG normal sinus rhythm
ECG QRS transition
ECG rate and rhythm
ECG cardiac infarction and ischemia
ECG cardiac hypertrophy and enlargement
Control of blood flow circulation
Microcirculation and Starling forces
Blood pressure, blood flow, and resistance
Compliance of blood vessels
Laminar flow and Reynolds number
Pressures in the cardiovascular system
Resistance to blood flow
Action potentials in myocytes
Action potentials in pacemaker cells
Cardiac excitation-contraction coupling
Excitability and refractory periods
0 / 14 complete
0 / 4 complete
S4 heart sound and p. 733
heart sounds of p. 292, 295
associations p. 733
auscultation of p. 295
cardiac cycle p. 292
cardiac tamponade p. 477, 725
splitting in p. 294
S3 heart sound p. 733
heart sounds of p. 295
If you put a stethoscope over the chest, you’ll usually hear something that sounds like lub dub, lub dub, lub dub, which repeats over and over again, with each cardiac cycle, or heartbeat.
Now, the question is, where does this sound come from? Normally, blood is constantly moving through the four chambers of the heart- coming through the veins into the right atrium, going to the right ventricle, then shooting off via the pulmonary arteries to the lungs and coming back from the pulmonary veins into the left atrium and the left ventricle, to be pumped into the aorta. So, in every step, some valves have to open and others have to close. Valves are just “communicating doors” that, when open, allow blood to pass through, and when closed, hold blood within a chamber. So, in total, our heart has four valves- two atrioventricular valves, which separate the atria from the ventricles and are the mitral valve, on the left side, and the tricuspid valve, on the right side, and two semilunar valves, which separate the ventricles from the large arteries coming off of them and are the pulmonary valve, on the right side, and the aortic valve, on the left side. And when these valves are closing, just like a door slamming shut, they are going to make a sound that is transmitted in the direction of the blood flow.
Now the heart is positioned in such a way that the sound of the closing of each of these valves is projected onto a small area on the chest wall. If you place a stethoscope between the second and third rib, known as the right second intercostal space, just next to the upper border of the sternum, you’ll hear the aortic valve closing. Then, if you place a stethoscope in the left second intercostal space, at the left upper sternal border, you can hear the pulmonary valve closing. Making our way down, between the fourth and fifth rib, next to the left lower border of the sternum, is where you can best hear the tricuspid valve closing. Finally, let’s move down to between the fifth and sixth rib, so in the left fifth intercostal space, near the midclavicular line. The midclavicular line is the imaginary line that gets drawn from the midpoint of the left clavicle, or the collarbone, straight down, so you can find where it intersects with the fifth intercostal space. That’s where the mitral valve closing is best heard.
Heart sounds are the noises generated by the beating heart and the resultant flow of blood through it. Specifically, the sounds reflect the turbulence created when the heart valves snap shut. In cardiac auscultation, an examiner may use a stethoscope to listen for these unique and distinct sounds that provide important auditory data regarding the condition of the heart. There are two normal heart sounds: S1 and S2. S1 is caused by the closing of atrioventricular valves at the beginning of systole; whereas S2 is caused by the closing of aortic and pulmonary valves closing at the beginning of diastole.
Latest on COVID-19
Nurse Practitioner (NP)
Physician Assistant (PA)
Create custom content
Raise the Line Podcast
Copyright © 2024 Elsevier, its licensors, and contributors. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
Cookies are used by this site.
Terms and Conditions
USMLE® is a joint program of the Federation of State Medical Boards (FSMB) and the National Board of Medical Examiners (NBME). COMLEX-USA® is a registered trademark of The National Board of Osteopathic Medical Examiners, Inc. NCLEX-RN® is a registered trademark of the National Council of State Boards of Nursing, Inc. Test names and other trademarks are the property of the respective trademark holders. None of the trademark holders are endorsed by nor affiliated with Osmosis or this website.