📚 Human Reproduction and Development | 人类生殖与发育
In the Cambridge Lower Secondary Science course, learners explore how the human body changes during adolescence and how the reproductive system enables new life to begin. This topic builds on earlier ideas about cells and organ systems, and it prepares students for later study of genetics and health. Understanding reproduction is not only a key area of biology but also helps learners make informed decisions about their own wellbeing.
在剑桥初中科学课程中，学生将探索人体在青春期发生的变化，以及生殖系统如何孕育新生命。这一主题建立在细胞和器官系统等已有知识的基础上，并为以后学习遗传学和健康知识做好准备。了解生殖不仅是生物学的核心内容，也有助于学生对自己的健康做出明智的决定。
1. Adolescence and Puberty | 青春期
Puberty is the stage of life when a child’s body develops into an adult body capable of reproduction. It is triggered by hormones: in boys, testosterone is released from the testes; in girls, oestrogen is released from the ovaries. These hormones cause secondary sexual characteristics such as growth of pubic hair, deepening of the voice in boys, and breast development and the start of menstruation in girls.
青春期是人体从儿童发育为具备生殖能力的成年人的阶段。这一过程由激素触发：男孩的睾丸分泌睾酮，女孩的卵巢分泌雌激素。这些激素引发第二性征，例如阴毛生长、男孩声音变低沉、女孩乳房发育以及月经开始。
Adolescence also brings emotional and social changes. Learners often notice rapid growth in height and changes in body shape. These changes happen at different rates for different individuals, which is perfectly normal. In science, we focus on the biological processes rather than making comparisons between people.
青春期还会带来情感和社会方面的变化。学生通常会注意到身高迅速增长和体型变化。这些变化在不同个体身上发生的速度不同，这是完全正常的。在科学中，我们关注生物学过程，而不是对人与人之间进行比较。
2. The Male Reproductive System | 男性生殖系统
The male reproductive system is designed to produce sperm cells and deliver them to the female reproductive system. The main organs include the testes, scrotum, sperm ducts, prostate gland, urethra and penis. The testes produce sperm and the hormone testosterone. The scrotum holds the testes outside the body to keep them slightly cooler, which is important for sperm production.
男性生殖系统的功能是产生精子并将其输送到女性生殖系统。主要器官包括睾丸、阴囊、输精管、前列腺、尿道和阴茎。睾丸产生精子和睾酮激素。阴囊将睾丸置于体外，使其保持稍低的温度，这对精子的产生非常重要。
During sexual intercourse, sperm pass along the sperm ducts. The prostate gland adds fluid to nourish the sperm and help them move. This mixture of sperm and fluid is called semen. The penis delivers semen into the female reproductive system through the urethra.
在性交过程中，精子沿着输精管移动。前列腺分泌液体为精子提供营养并帮助其运动。精子和这些液体的混合物称为精液。阴茎通过尿道将精液输送到女性生殖系统中。
3. The Female Reproductive System | 女性生殖系统
The female reproductive system produces egg cells, receives sperm, and supports the development of a baby during pregnancy. The main organs are the ovaries, oviducts, uterus, cervix and vagina. The ovaries produce egg cells and the hormones oestrogen and progesterone.
女性生殖系统产生卵细胞、接收精子，并在怀孕期间支持胎儿的发育。主要器官包括卵巢、输卵管、子宫、宫颈和阴道。卵巢产生卵细胞以及雌激素和孕激素。
The oviducts, also called fallopian tubes, carry an egg from the ovary to the uterus. Fertilisation usually occurs in an oviduct. The uterus is a muscular organ where a fertilised egg can implant and grow. The cervix is the narrow neck of the uterus, and the vagina connects the cervix to the outside of the body.
输卵管将卵子从卵巢输送到子宫。受精通常发生在输卵管内。子宫是一个肌肉器官，受精卵可在其中着床并生长。宫颈是子宫狭窄的下端，阴道将宫颈与身体外部连接起来。
4. Gametes: Sperm and Egg Cells | 配子：精子与卵细胞
Sperm cells and egg cells are the gametes, or sex cells, of humans. A sperm cell is very small and has a tail called a flagellum, which enables it to swim. It contains many mitochondria to release energy for movement and a haploid nucleus carrying genetic information from the father.
精子和卵子是人类的配子，即性细胞。精子非常小，有一条称为鞭毛的尾巴，使其能够游动。精子含有许多线粒体，为运动释放能量，还含有一个单倍体细胞核，携带来自父亲的遗传信息。
An egg cell is much larger than a sperm cell because it contains stored nutrients in its cytoplasm. It also has a haploid nucleus carrying genetic information from the mother. When the nuclei of a sperm and an egg fuse during fertilisation, a diploid zygote is formed with a full set of chromosomes.
卵细胞比精子大得多，因为其细胞质中储存了营养物质。卵细胞也含有一个单倍体细胞核，携带来自母亲的遗传信息。当精子和卵子的细胞核在受精过程中融合时，会形成具有完整染色体组的二倍体受精卵。
- Sperm cell adaptations: flagellum for swimming, many mitochondria for energy, haploid nucleus.
- Egg cell adaptations: large cytoplasm with food stores, haploid nucleus.
- 精子的适应特征：鞭毛用于游动，许多线粒体提供能量，单倍体细胞核。
- 卵细胞的适应特征：细胞质大并储存营养物质，单倍体细胞核。
5. The Menstrual Cycle | 月经周期
The menstrual cycle is a monthly series of changes in the female reproductive system. It usually lasts about 28 days, although cycles between 21 and 35 days are common. The cycle prepares the uterus for a possible pregnancy.
月经周期是女性生殖系统每月发生的一系列变化。它通常持续约 28 天，但 21 至 35 天的周期也很常见。该周期使子宫为可能的怀孕做好准备。
At the start of the cycle, the lining of the uterus breaks down and is lost through the vagina. This bleeding is called menstruation. After menstruation, the uterus lining gradually thickens again under the influence of oestrogen. Around day 14 of a 28-day cycle, ovulation occurs: an egg is released from an ovary and travels into an oviduct.
在周期开始时，子宫内膜脱落并通过阴道排出。这种出血称为月经。月经结束后，在雌激素的影响下，子宫内膜逐渐再次增厚。在 28 天周期的第 14 天左右发生排卵：卵子从卵巢释放并进入输卵管。
After ovulation, progesterone helps maintain the thickened lining. If fertilisation does not occur, the levels of oestrogen and progesterone fall, and the lining breaks down again. This begins the next menstrual period.
排卵后，孕激素帮助维持增厚的子宫内膜。如果未发生受精，雌激素和孕激素水平下降，内膜再次脱落，开始下一个月经期。
6. Fertilisation and Implantation | 受精与着床
Fertilisation is the fusion of a sperm nucleus with an egg nucleus. It usually takes place in the oviduct after ovulation. During sexual intercourse, millions of sperm are released into the vagina, but only a small number reach the oviduct. Only one sperm enters the egg membrane, and then the egg membrane changes to prevent any other sperm from entering.
受精是精子细胞核与卵细胞核的融合。它通常发生在排卵后的输卵管内。在性交过程中，数百万个精子被释放到阴道中，但只有少量能到达输卵管。只有一个精子能进入卵细胞膜，之后卵细胞膜发生变化，阻止其他精子进入。
After fertilisation, the zygote divides many times as it moves towards the uterus. The ball of cells that forms is called an embryo. When the embryo reaches the uterus, it sinks into the thickened lining. This process is called implantation, and it marks the beginning of pregnancy.
受精后，受精卵在向子宫移动的过程中多次分裂。形成的细胞团称为胚胎。当胚胎到达子宫时，它埋入增厚的子宫内膜中。这一过程称为着床，标志着怀孕的开始。
7. Pregnancy and Fetal Development | 怀孕与胎儿发育
After implantation, the embryo continues to develop. The placenta forms and attaches to the wall of the uterus. The placenta allows the exchange of substances between the mother’s blood and the baby’s blood without the two blood supplies mixing directly. Oxygen and nutrients pass from mother to baby, and waste products such as carbon dioxide pass from baby to mother.
着床后，胚胎继续发育。胎盘形成并附着在子宫壁上。胎盘允许母体血液和婴儿血液之间进行物质交换，但双方的血液不会直接混合。氧气和营养物质从母体传给婴儿，二氧化碳等废物从婴儿传给母体。
The baby is connected to the placenta by the umbilical cord. The baby floats in amniotic fluid, which protects it from bumps and sudden movements. Around eight weeks after fertilisation, the developing embryo is called a fetus. During the remaining months, the organs and body systems continue to grow and mature.
婴儿通过脐带与胎盘相连。婴儿漂浮在羊水中，羊水可保护婴儿免受碰撞和突然运动的伤害。受精后约 8 周，发育中的胚胎称为胎儿。在接下来的几个月里，器官和身体系统继续生长和成熟。
8. Birth and the Afterbirth | 分娩与胎盘娩出
After about nine months of pregnancy, birth begins. The muscles of the uterus contract rhythmically. These contractions cause the cervix to dilate, or widen, so the baby can pass through. The amniotic sac often breaks at this stage, releasing the amniotic fluid.
怀孕约九个月后，分娩开始。子宫肌肉有节律地收缩。这些收缩使宫颈扩张，以便婴儿能够通过。羊膜囊通常在这个阶段破裂，释放出羊水。
The baby is pushed through the cervix and vagina and out of the mother’s body. After the baby is born, the umbilical cord is clamped and cut. The placenta and remaining membranes are delivered later; this is called the afterbirth. The baby now begins to breathe and feed independently.
婴儿被推出宫颈和阴道，离开母体。婴儿出生后，脐带被夹住并剪断。胎盘和剩余的胎膜随后排出体外，这称为胎盘娩出。婴儿现在开始独立呼吸和进食。
9. Contraception and Reproductive Health | 避孕与生殖健康
Contraception is the use of methods to prevent pregnancy. Barrier methods, such as condoms, prevent sperm from reaching the egg. Hormonal methods, such as the contraceptive pill, change the levels of hormones in a woman’s body to prevent ovulation. Other methods include intrauterine devices and natural methods based on timing.
避孕是指使用各种方法防止怀孕。屏障避孕法（如避孕套）阻止精子到达卵子。激素避孕法（如避孕药）改变女性体内的激素水平以阻止排卵。其他方法包括宫内节育器和基于时间推算的自然避孕法。
Some contraceptive methods, especially condoms, also reduce the risk of sexually transmitted infections (STIs). Good reproductive health includes understanding how to prevent infections and knowing when to seek medical advice. In science lessons, learners study the biological basis of these methods rather than making personal choices.
某些避孕方法，尤其是避孕套，还能降低性传播感染的风险。良好的生殖健康包括了解如何预防感染，以及知道何时应寻求医疗建议。在科学课上，学生学习这些方法的生物学原理，而不是做出个人选择。
10. Key Terms and Checkpoints | 关键术语与复习要点
The table below summarises the key terms for this topic. Use it as a quick revision checklist before your checkpoint test.
下表总结了本主题的关键术语。你可以在考前将其作为快速复习清单使用。
| Term | 术语 | Definition | 定义 |
|---|---|
| Puberty | 青春期 | Stage when the body becomes capable of reproduction | 身体具备生殖能力的阶段 |
| Hormone | 激素 | Chemical messenger that controls body changes | 控制身体变化的化学信使 |
| Gamete | 配子 | Sex cell, such as sperm or egg | 性细胞，如精子或卵子 |
| Fertilisation | 受精 | Fusion of sperm and egg nuclei | 精子与卵子细胞核的融合 |
| Implantation | 着床 | Embryo sinks into the uterus lining | 胚胎埋入子宫内膜 |
| Placenta | 胎盘 | Organ for exchange between mother and baby | 母体与婴儿之间进行物质交换的器官 |
| Ovulation | 排卵 | Release of an egg from the ovary | 卵子从卵巢释放 |
| Contraception | 避孕 | Methods used to prevent pregnancy | 用于防止怀孕的方法 |
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