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A heart valve is a biological one-way valve that allows blood to flow in one direction through the chambers of the heart. A mammalian heart usually has four valves. Together, the valves determine the direction of blood flow through the heart. Heart valves are opened or closed by a difference in blood pressure on each side. [1] [2] [3]
Cardiac activity is visible beginning at approximately 5 weeks of pregnancy. The human heart begins beating at a rate near the mother's, about 75-80 beats per minute (BPM). The embryonic heart rate (EHR) then accelerates linearly for the first month of beating, peaking at 165-185 BPM during the early 7th week, (early 9th week after the LMP).
The first heart sound, or S 1, forms the "lub" of "lub-dub" and is composed of components M 1 (mitral valve closure) and T 1 (tricuspid valve closure). Normally M 1 precedes T 1 slightly. It is caused by the closure of the atrioventricular valves , i.e. tricuspid and mitral (bicuspid), at the beginning of ventricular contraction, or systole .
The embryonic heart begins beating at around 22 days after conception (5 weeks after the last normal menstrual period, LMP). It starts to beat at a rate near to the mother's which is about 75–80 beats per minute (bpm). The embryonic heart rate then accelerates and reaches a peak rate of 165–185 bpm early in the early 7th week (early 9th ...
One should comment on S1 and S2 – if the splitting is abnormal or louder than usual. S3 – the emphasis and timing of the syllables in the word Kentucky is similar to the pattern of sounds in a precordial S3. S4 – the emphasis and timing of the syllables in the word Tennessee is similar to the pattern of sounds in a precordial S4.
The cardiac cycle is the performance of the human heart from the beginning of one heartbeat to the beginning of the next. [1] It consists of two periods: one during which the heart muscle relaxes and refills with blood, called diastole , following a period of robust contraction and pumping of blood, called systole . [ 1 ]
The pathophysiology depends on the specific cause of right axis deviation. Most causes can be attributed to one of four main mechanisms. [14] [15] These include right ventricular hypertrophy, reduced muscle mass of left ventricle, altered conduction pathways and change in the position of the heart in the chest. [citation needed]
The Björk–Shiley valve consists of a single carbon-coated disc in a metal housing. The disc is held in place by two metal struts, an inflow and an outflow strut. The housing is made from the alloy Haynes 25, [1] which is composed of 51% cobalt, 20% chromium, 15% tungsten, and 10% nickel. [2]