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中师《生理卫生》教材中,“循环系统”一章的“血液”一节中,在讲到测定血液组成成分时,要求向血液中加入适量的柠檬酸钠,以防止血液凝固。但在课堂教学中,多数学生对柠檬酸钠为什么能抗凝?血液凝固的机理是什么?等问题尚不清楚。为帮助学生加深对课本的理解,我在教学过程中设计并补充了一组血液抗凝的实验,效果良好。现将这组实验介绍如下。 一、实验原理 血浆中含纤维蛋白原、血小板遇到粗糙的血管壁伤口,就被破坏并释放出促使血液凝固的凝血酶。这种酶的前身是凝血酶原,在 Ca~(2+)参与下,凝血酶原激活物可催化凝血酶原转化为具有活性的凝血酶。在凝血酶、Ca~(2+)和其它一些因子的作用下,经过一系列变化.可溶性的纤维蛋白原就变成了不溶性的丝状纤维蛋自。这种蛋白形成后,互相交织成网,并把血细胞网罗在内,使原来的血液凝集成块。要防止离体的血液凝固,可通过以下几种途径来实现: 1、往血液中加入适量的抗凝剂（如柠檬酸钠）将 Ca~(2+)夺去,使其成为失钙血,这样可以防止纤维蛋白原变成纤维蛋白,从而避免
In the textbook “Physical Hygiene” of the Central Normal University, in the “Blood” section of the “Circulation System” chapter, when it comes to measuring blood components, it is required to add proper sodium citrate to the blood to prevent blood clotting. However, in the classroom teaching, most students are unable to anticoagulate sodium citrate, what is the mechanism of blood coagulation, and other issues are not yet clear. To help students deepen their understanding of textbooks, I designed and supplemented a series of blood anticoagulation experiments in the teaching process. This set of experiments is now described below. First, the experimental principle Plasma containing fibrinogen, platelets encountered a rough wound on the blood vessel wall, it is destroyed and releases thrombin to promote blood clotting. The predecessor of this enzyme is prothrombin. In the presence of Ca~(2+), the prothrombin activator catalyzes the conversion of prothrombin to active thrombin. Under the influence of thrombin, Ca 2+ and other factors, soluble fibrinogen changes into insoluble filamentous fibrils. After the protein is formed, it is interwoven into a net and the blood cells are collected to make the original blood clot. To prevent blood coagulation in vitro, it can be achieved through the following ways: 1. Add an appropriate amount of anticoagulant (such as sodium citrate) to the blood to take Ca~(2+) and make it become decalcified blood. This prevents fibrinogen from becoming fibrin, thus avoiding