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- In the early part of this phase, the atrioventricular valves are closed and blood pools in the atria. There comes a point when the pressure in the atrium is greater than the pressure in the ventricle of the same side. This pressure difference results in the opening of the atrioventricular valves, allowing blood to flow into the ventricle.
www.kenhub.com/en/library/physiology/cardiac-cycleCardiac cycle phases: Definition, systole and diastole - Kenhub
The second heart sound, S 2 or dub, occurs when the semilunar valves close. When the pressure falls below that of the atria, blood moves from the atria into the ventricles, opening the atrioventricular valves and marking one complete heart cycle. The valves prevent backflow of blood.
- Lindsay M. Biga, Sierra Dawson, Amy Harwell, Robin Hopkins, Joel Kaufmann, Mike LeMaster, Philip Mat...
- 2019
- Introduction
- Structure of The Heart
- The Cardiac Cycle
- Wigger’s Diagram
- Cardiac Volumes
- Key Points
- References
The heart is the pump of the body’s circulatory system. It must work in a systematic way so that the body is adequately supplied with blood. This article will give an overview of the cardiac cycle, highlighting the physiology and clinical relevance.
Blood flows through the structures of the heart in the following order: 1. Great veins (the venae cavae on the right and the pulmonary vein on the left) 2. Atria 3. Ventricles 4. Great arteries (the pulmonary artery on the right and the aorta on the left) There are two sets of valves, theatrioventricular and thesemilunar valves, on each side of the...
The heart relies on its muscle to contract and relax to pump the blood around the body. The left and right sides of the heart areindependent of each other, however, will contract synchronously. When in a contractile state, this is called systole. When in a relaxed state, this is called diastole. The cycle can then be divided into three stages: 1. A...
Wigger’s diagram is used to demonstrate thevarying pressures in the atrium, ventricle, and artery during one cardiac cycle (Figure 2). Intracardiac pressures are different within the right and left sides of the heart. The left side hashigher pressure, as it has to pump blood through the whole body, compared to the right side, which has to pump bloo...
There are two cardiac volumes to be measured during the cardiac cycle. 1. Ventricular end-systolic volume= the volume of blood in the ventricle at the end of the systolic phase 2. Ventricular end-diastolic volume= the volume of blood in the ventricle at the end of the diastolic phase These volumes can then be used to calculate other parameters whic...
The cardiac cycle can be divided into systolic (contraction) and diastolic(relaxation) phases.The cycle goes in the following order: atrial systole, ventricular systole and diastole.Heart valves open when the pressure of the chamber lying before it is higherthan that of the chamber after the valve.The shutting of the valves produces the two heart sounds(S1/S2), also known as the ‘lub-dub’ heart sounds.Reference texts
1. Gillian Pocock, Christopher D. Richards, David A. Richards. Human Physiology (Fifth Edition). 2018. 2. Walter F. Boron, Emile L. Boulpaep. Medical Physiology (Third Edition). 2017.
Reference images
1. Figure 1. OpenStax. Dual System of the Human Blood Circulation. License: [CC BY 4.0] 2. Figure 2 – 6. DanielChangMD. Adapted by Geeky Medics. Wigger’s diagram. Licence: [CC BY-SA 2.5]
The second heart sound, S 2 or dub, occurs when the semilunar valves close. When the pressure falls below that of the atria, blood moves from the atria into the ventricles, opening the atrioventricular valves and marking one complete heart cycle. The valves prevent backflow of blood.
The two SL valves – the pulmonary and aortic valves – are closed, preventing backflow of blood into the right and left ventricles from the pulmonary trunk on the right and the aorta on the left. During filling ventricular pressure increases, while atrial pressure decreases.
As the atrial muscles contract from the superior portion of the atria toward the atrioventricular septum, pressure rises within the atria and blood is pumped into the ventricles through the open atrioventricular (tricuspid, and mitral or bicuspid) valves.
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Why do atrioventricular valves close during atrial systole?
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How does atrial systole affect ventricular pressure?
Closing of the atrioventricular valves produces a monosyllabic “lup” sound. Following a brief delay, the ventricles contract at the same time forcing blood through the semilunar valves into the aorta and the artery transporting blood to the lungs (via the pulmonary artery).
