血象

血培养

粪便培养

尿培养

肥达反应

The sperm has to get through corona radiate to finish fertilization.

Fertilization occurs when the sperm can deliver its genetic material.

The egg is released from the fallopian tube to meet the sperm.

When egg and sperm fuse, a diploid cell is formed.

疝环小而内容物多

疝环小而疝囊颈的弹力大

疝环小而腹内压突然增加

疝环小而疝囊颈水肿

疝环大而疝囊颈水肿

Menstruation

Bleeding

Ovulation

Menopause

全班 65%的同学考试成绩高于均值

全班 65%的同学考试成绩高于中数

全班 65%的同学考试成绩高于众数

全班同学考试成绩是负偏态分布

Menstruation

Bleeding

Ovulation

menopause

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. 【甲 】【乙】 两文在写法、构思上都有相同之处 ， 都有情节 ， 有人物 ， 有议论 ， 有描述 ， 以小见大 ， 寓意发人深省 。

Of the 300 million human sperm ejaculated during sexual intercourse, only about 200 reach the site of fertilization in the oviduct. Sperm are attracted to an ovulated egg by chemical signals released by both the egg and the supporting cells that surround it. Once a sperm finds the egg, it must migrate through a protective layer of cells and then bind to, and tunnel through, the egg coat, called the zona pellucida.

Finally, the sperm must bind to and fuse with the underlying egg plasma membrane. Although fertilization normally occurs by this process of sperm–egg fusion, it can also be achieved artificially by injecting the sperm directly into the egg cytoplasm; this is often done in infertility clinics when there is a problem with natural sperm–egg fusion.

Although many sperm may bind to an egg, only one normally fuses with the egg plasma membrane and introduces its DNA into the egg cytoplasm. The control of this step is especially important because it ensures that the fertilized egg—also called a zygote—will contain two, and only two, sets of chromosomes. Several mechanisms prevent multiple sperm from entering an egg. In one mechanism, the first successful sperm triggers the release of a wave of Ca 2+ ions in the egg cytoplasm. This flood of Ca 2+ in turn triggers the secretion of enzymes that cause a “hardening” of the zona pellucida, which prevents “runner up” sperm from penetrating the egg. The Ca 2+ wave also helps trigger the development of the egg. To watch a fertilization-induced calcium wave.

The process of fertilization is not complete, however, until the two haploid nuclei (called pronuclei) come together and combine their chromosomes into a single diploid nucleus. Soon after the pronuclei fuse, the diploid cell begins to divide, forming a ball of cells that—through repeated rounds of cell division and differentiation—will give rise to an embryo and, eventually, an adult organism. Fertilization marks the beginning of one of the most remarkable phenomena in all of biology—the process by which a single-celled zygote initiates the developmental program that directs the formation of a new individual.