23.5
心脏瓣膜
人类心脏是一个复杂的器官，具有调节血流的精密瓣膜系统。主要瓣膜分为两类：房室瓣（AV瓣）和半月瓣。
房室瓣可防止心室收缩时血液从心室倒流回心房。这些瓣膜在腱索和乳头肌的协助下发挥作用。当心室舒张时，腱索处于松弛状态，使血液能够无阻力地从心房流入心室。然而，当心室收缩时，血液向心房方向回流会促使房室瓣…
心脏瓣膜会根据心腔收缩所产生的压力梯度而开启和关闭。
这些瓣膜通过维持心房、心室和血管之间单向血流来调节血液流动。
房室瓣或称为 AV 瓣，连接心房和心室。
三尖瓣连接右心腔，而二尖瓣连接左心腔。这些瓣膜在开放时允许血液流入心室。当心室内压力升高时，瓣膜关闭。
此外，心室乳头肌及其相连的腱索会在反向压力作用下牵拉房室瓣，防止其向心房方向开启。
半月瓣将心室与血管相连。主动脉瓣位于主动脉和左心室之间，而肺动脉瓣位于肺动脉干和右心室之间。
当心室收缩时，升高的压力迫使半月瓣打开，使血液迅速流入血管。当心室舒张时，血液充满瓣膜瓣叶，使其关闭。
View the full transcript and gain access to JoVE Core videos
Q1: What are the two main types of heart valves and where are they located?
The heart has two main valve types: atrioventricular (AV) valves and semilunar valves. AV valves connect the atria to the ventricles—the tricuspid valve links the right chambers, while the bicuspid valve connects the left chambers. Semilunar valves link ventricles to blood vessels: the aortic valve sits between the aorta and left ventricle, and the pulmonary valve lies between the pulmonary trunk and right ventricle.
Q2: How do atrioventricular valves prevent blood from flowing backward into the atria?
AV valves close when ventricular pressure rises during contraction. The papillary muscles contract and tense the chordae tendineae, which pull on the valve cusps and prevent them from swinging into the atria. This muscular bracing system stops backflow of blood during ventricular contraction, ensuring one-directional circulation.
Q3: Why do semilunar valves not require muscular support like atrioventricular valves?
Semilunar valves do not need muscular braces because the arterial walls do not contract and the relative positions of the cusps remain stable. When these valves close, their three symmetrical cusps support each other like the legs of a tripod. Additionally, the aortic sinuses prevent individual cusps from sticking to the aorta wall.
Q4: What happens to heart valves during the cardiac cycle?
Heart valves open and close in response to pressure gradients created by contracting heart chambers. When ventricles contract, increased pressure forces semilunar valves open, allowing blood to rush into blood vessels. When ventricles relax, blood fills the valve cusps, closing them and preventing backflow during the cardiac cycle.
Q5: What role do chordae tendineae and papillary muscles play in valve function?
The chordae tendineae are fibrous cords attached to papillary muscles that control AV valve movement. When ventricles relax, chordae tendineae are slack, allowing blood to flow from atria into ventricles. During ventricular contraction, papillary muscles tense the chordae tendineae, preventing valve cusps from opening into the atria and maintaining proper blood flow direction.
Q6: What is valvular heart disease and what causes it?
Valvular heart disease (VHD) occurs when valve function deteriorates, disrupting normal heart functioning and circulatory flow. Damage to chordae tendineae or papillary muscles can cause regurgitation or backflow of blood. VHD can be congenital or develop after carditis, an inflammation of the heart affecting valve integrity.
Q7: How do pressure gradients control the opening and closing of heart valves?
Heart valves respond directly to pressure differences between heart chambers and blood vessels. When ventricular pressure exceeds atrial pressure, AV valves close. When ventricular pressure exceeds arterial pressure, semilunar valves open. This pressure-driven mechanism ensures unidirectional blood flow through the heart and maintains efficient circulation throughout the body.