性-人类性的基本层面
Sex - Basic Aspects of Human Sexuality

初级性特征的发育   Development of primary sexual characteristics

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在起初，两性之间的身体不像看起来有那么大的差别，男女的性器官在结构上甚至非常相象。当然，在胚胎发育的前几周里，在结构上实际不能区分出男女。只有到了出生前的胚胎发育和出生后的青春期发育，男女差别才明晰可见，而且造就了男女的那种为生殖目的而互补的结构差异。可是，尽管这样，我们仍然能够发现相应的起源于同一细胞团的“同源”结构。

The physical difference between the sexes is not as great as it may appear at first glance. Even the female and male sex organs are structurally very similar. Indeed, in the first weeks of their development they are practically indistinguishable. It is only their subsequent growth before birth and later during puberty which makes them complementary to each other for the purpose of procreation. However, even then one can still find corresponding, i.e. "homologous" structures that originated in the same cell mass.

女孩

出生前

两性都来自于公共的胚基

在生命的早几周里，男女胚胎仍保持未分化状态。这时，他们都有了头和肢芽。肢芽是上肢和下肢的前驱结构。同样，这些胚胎也有将要生长成性器官的组织脊，既生殖脊。可是，在这个生殖脊上，人们所能够见到的全部就是一个隆起（使人联想到男性）和一条凹沟（让人联想到女性）。

典型的女性发育

对于女性胚胎，这个隆起发育成阴蒂。而凹沟仍敞开着，逐渐发育形成小阴唇和引导的前部分。在两侧，两小片皮肤发育成大阴唇。另有一些细胞团发育成卵巢。在出生时，外部和内部性器官让人能够清晰地分辨出女性。

在青春期

女性性器官只有在青春期，一般在11-13岁之间，才开始发育直到成人大小和具有生殖功能。从这个意义上看，性成熟的标志是阴毛和首次月经来潮。

男孩

出生前

出生前

两性都来自于公共的胚基

在生命的早几周里，男女胚胎仍保持未分化状态。这时，他们都有了头和肢芽。肢芽是上肢和下肢的前驱结构。同样，这些胚胎也有将要生长成性器官的组织脊，既生殖脊。可是，在这个生殖脊上，人们所能够见到的全部就是一个隆起（使人联想到男性）和一条凹沟（让人联想到女性）。

典型的男性发育

对于男性胚胎，这个隆起发育成阴茎，而凹沟则封闭起来。另外的细胞团发育成睾丸，随后开始分泌睾丸激素。睾丸激素继尔刺激生殖脊进一步发育和分化（缺了睾丸激素，胚胎必将“自动地”发育成一个女胎）。在生殖隆起两侧的两小片皮肤形成阴囊。到了妊娠的第7-9月，睾丸降入阴囊内（假如未降入阴囊，则需要后来的矫正，以避免不育）。在出生时，外部和内部性器官让人能够清晰地分辨出男性。

在青春期

男性性器官只有在青春期，一般在12-17岁之间，才开始发育直到成人大小和具有生殖功能。从这个意义上看，性成熟的标志是阴毛和首次射精。

Girls

Before birth

Both sexes start from a common base
Female and male embryos remain undifferentiated during the first weeks of their lives. They already have a head and limb buds which begin to grow into arms and legs. They also have a ridge of tissue destined to grow into sex organs. However, all one can see at this point is a hump (suggestive of the male) and a groove (suggestive of the female).

The female sex organs reach their full size and function only during puberty, usually between the ages of 11-13. Indications of sexual maturity in this sense are the growth of pubic hair and the first menstruation.

Boys

Before birth

Both sexes start from a common base
Female and male embryos remain undifferentiated during the first weeks of their lives. They already have a head and limb buds which begin to grow into arms and legs. They also have a ridge of tissue destined to grow into sex organs. However, all one can see at this point is a hump (suggestive of the male) and a groove (suggestive of the female).

Typical male development
In the male embryo the hump grows into the penis, and the groove closes. Another cell mass grows into testicles which begin to produce the hormone testosterone. This hormone, in turn, stimulates further growth and differentiation. (Without it, the embryo would “automatically” grow into a female.) Two patches of skin on either side of the hump form the scrotum. Between the seventh and ninth month of pregnancy, the testicels descend into the scrotum. (If they fail to descend, some later correction is required in order to prevent infertility.) At birth, the internal and external sex organs are clearly defined as male.

During puberty

The male sex organs reach their full size and function only during puberty, usually between the ages of 12-17. Indications of sexual maturity in this sense are the growth of pubic hair and the first ejaculation of semen.