📚 Human Reproduction | 人体生殖系统
Human reproduction is the process by which offspring are produced, involving the union of male and female gametes. This topic covers the anatomy of reproductive systems, hormonal control, the menstrual cycle, fertilisation, pregnancy, birth, and methods of contraception. Understanding how life begins is essential for biology, and it has enormous social and ethical importance.
人类的生殖是产生后代的过程，涉及男性和女性配子的结合。本主题涵盖生殖系统解剖结构、激素调控、月经周期、受精、妊娠、分娩以及避孕方法。理解生命如何开始的原理，对生物学至关重要，也具有极大的社会和伦理意义。
1. Overview of Reproductive Systems | 生殖系统概述
Sexual reproduction requires two parents. Each parent produces specialised sex cells called gametes. In humans, the male gamete is the sperm and the female gamete is the egg (ovum). At puberty, the reproductive organs mature and secondary sexual characteristics develop under the influence of hormones. The purpose of the reproductive systems is to ensure that gametes meet, fuse, and develop into a new individual.
有性生殖需要双亲。每个亲本产生特化的性细胞，称为配子。在人类中，雄性配子是精子，雌性配子是卵子。青春期时，生殖器官成熟，并在激素影响下发展出第二性征。生殖系统的目的是确保配子相遇、融合并发育成一个新个体。
2. Male Reproductive System | 男性生殖系统
The male reproductive system is designed to produce, store and deliver sperm. The testes, located inside the scrotum, are the site of sperm production (spermatogenesis) and also secrete the hormone testosterone. Sperm are stored and mature in the epididymis. During ejaculation, sperm travel through the vas deferens (sperm duct), mix with fluids from the seminal vesicles, prostate gland and Cowper's gland to form semen, and exit the body through the urethra inside the penis.
男性生殖系统的功能是产生、储存和输送精子。位于阴囊内的睾丸是精子生成（精子发生）的部位，也分泌激素睾酮。精子在附睾中储存并成熟。射精时，精子经过输精管，与来自精囊、前列腺和尿道球腺的液体混合形成精液，并通过阴茎内的尿道排出体外。
The scrotum holds the testes outside the body cavity. This is important because sperm production requires a temperature slightly lower than normal body temperature (about 35 °C). The penis contains erectile tissue that can fill with blood to become erect, allowing it to be inserted into the vagina to deposit semen close to the cervix.
阴囊将睾丸保持在腹腔之外。这一点很重要，因为精子的生成需要的温度略低于正常体温（约35 °C）。阴茎含有勃起组织，充血后可勃起，从而能够插入阴道将精液输送到子宫颈附近。
| Organ | Function |
|---|---|
| Testis | Produces sperm and testosterone |
| Epididymis | Stores sperm; allows them to mature |
| Vas deferens (sperm duct) | Carries sperm from epididymis to urethra |
| Seminal vesicles, prostate gland, Cowper's gland | Secrete fluids that nourish sperm and form semen |
| Urethra | Tube through which semen and urine leave the body (not at the same time) |
| Penis | Delivers semen into the female reproductive tract |
器官功能表（英文如上）。中文对照：睾丸产生精子和睾酮；附睾储存精子并使其成熟；输精管将精子从附睾运送到尿道；精囊、前列腺和尿道球腺分泌滋养精子的液体并形成精液；尿道是精液和尿液排出的管道（不会同时）；阴茎将精液输送到女性生殖道。
3. Female Reproductive System | 女性生殖系统
The female reproductive system produces eggs, provides a site for fertilisation, supports the development of the embryo and foetus, and enables birth. The ovaries produce eggs (ova) and secrete the hormones oestrogen and progesterone. Each month, during the menstrual cycle, an ovum is released from an ovary in the process of ovulation. The ovum is caught by the funnel-shaped end of the oviduct (Fallopian tube) and travels towards the uterus.
女性生殖系统产生卵子，提供受精的场所，支持胚胎和胎儿的发育，并实现分娩。卵巢产生卵子，并分泌雌激素和孕激素。在月经周期中，每个月会有一个卵子从卵巢释放，这个过程称为排卵。卵子被输卵管漏斗状的末端捕捉，并朝子宫方向移动。
Fertilisation normally occurs in the oviduct. The zygote then travels to the uterus, a muscular organ with a thick lining called the endometrium. If fertilisation occurs, the embryo implants into the endometrium; if not, the lining breaks down and is shed during menstruation. The cervix is the neck of the uterus that opens into the vagina. The vagina receives sperm during intercourse and serves as the birth canal.
受精通常发生在输卵管内。之后受精卵移动到子宫。子宫是一个肌肉发达的器官，有着厚厚的内膜，称为子宫内膜。如果受精发生，胚胎会植入子宫内膜；如果没有，内膜崩解并在月经期间脱落。子宫颈是子宫的颈部，通向阴道。阴道在性交时接收精子，并作为产道。
| Organ | Function |
|---|---|
| Ovary | Produces eggs and hormones (oestrogen, progesterone) |
| Oviduct (Fallopian tube) | Carries egg to uterus; site of fertilisation |
| Uterus | Houses and nourishes the developing foetus |
| Cervix | Separates the vagina from the uterus; dilates during birth |
| Vagina | Receives sperm; acts as birth canal |
中文对照：卵巢 — 产生卵子和激素（雌激素、孕激素）；输卵管 — 将卵子运送到子宫，是受精的场所；子宫 — 容纳并滋养发育中的胎儿；子宫颈 — 分隔阴道和子宫，分娩时扩张；阴道 — 接收精子，并作为产道。
4. Gametes: Sperm and Egg | 配子：精子和卵子
Gametes are haploid cells, meaning they contain half the normal number of chromosomes (23 in humans). This ensures that when a sperm fuses with an egg, the resulting zygote has the full diploid number (46 chromosomes). Sperm cells are highly specialised for movement. Each sperm consists of a head containing the nucleus, a midpiece packed with mitochondria to provide energy, and a tail (flagellum) that propels it through the female reproductive tract.
配子是单倍体细胞，这意味着它们含有正常染色体数目的一半（人类为23条）。这保证了当精子和卵子结合时，所形成的受精卵拥有完整的二倍体数目（46条染色体）。精子细胞高度特化，适于运动。每个精子包括一个含有细胞核的头部、一个充满线粒体以提供能量的中段，以及一条能推动精子在女性生殖道中游动的尾部（鞭毛）。
The egg cell (ovum) is much larger than a sperm because it contains a large amount of cytoplasm and nutrient reserves to support early development after fertilisation. Its cell membrane is surrounded by a protective layer called the zona pellucida. The egg is essentially immobile and is transported passively by cilia and muscular contractions of the oviduct.
卵子细胞比精子大得多，因为它含有大量细胞质和营养储备，以支持受精后的早期发育。其细胞膜外包裹着一层保护层，称为透明带。卵子基本上是不动的，被动地通过输卵管的纤毛和肌肉收缩来运输。
5. The Menstrual Cycle | 月经周期
The menstrual cycle is a roughly 28-day cycle controlled by hormones from the pituitary gland and ovaries. It prepares the female body for pregnancy. The cycle can be divided into four main phases: menstruation (days 1-5), the follicular phase (days 1-13), ovulation (around day 14), and the luteal phase (days 15-28). These phases reflect changes in the ovaries and the uterus lining.
月经周期是一个大约28天的周期，受垂体和卵巢分泌的激素控制。它为女性身体做好怀孕的准备。该周期可分为四个主要阶段：月经期（第1-5天）、卵泡期（第1-13天）、排卵期（约第14天）和黄体期（第15-28天）。这些阶段反映了卵巢和子宫内膜的变化。
During the follicular phase, several follicles in the ovary begin to develop, but usually only one matures fully. Rising levels of oestrogen from the developing follicle stimulate the thickening of the endometrium. Just before ovulation, a surge in luteinising hormone (LH) triggers the release of the mature egg. After ovulation, the empty follicle becomes the corpus luteum, which secretes progesterone. Progesterone maintains the thick endometrium and inhibits further ovulation. If the egg is not fertilised, the corpus luteum degenerates, progesterone levels fall, and the endometrium is shed as menstrual bleeding.
在卵泡期，卵巢中的多个卵泡开始发育，但通常只有一个完全成熟。发育中的卵泡分泌的雌激素水平上升，刺激子宫内膜增厚。在排卵前，黄体生成素（LH）的激增触发了成熟卵子的释放。排卵后，空的卵泡转变成黄体，分泌孕激素。孕激素维持着增厚的子宫内膜并抑制进一步的排卵。如果卵子未受精，黄体退化，孕激素水平下降，子宫内膜脱落形成月经出血。
6. Hormonal Control of Reproduction | 生殖的激素调控
The menstrual cycle is controlled by a negative feedback loop involving the hypothalamus, pituitary gland and ovaries. The pituitary gland produces follicle-stimulating hormone (FSH) and luteinising hormone (LH). FSH stimulates the growth of ovarian follicles and the secretion of oestrogen. Rising oestrogen levels initially inhibit FSH, but a high level of oestrogen stimulates a sudden surge in LH, which causes ovulation.
月经周期由涉及下丘脑、垂体腺和卵巢的负反馈环路控制。垂体腺产生促卵泡激素（FSH）和促黄体激素（LH）。FSH刺激卵泡的生长和雌激素的分泌。上升的雌激素水平起初抑制FSH，但高水平的雌激素刺激LH的突然激增，从而引起排卵。
After ovulation, the corpus luteum secretes progesterone. Progesterone inhibits the release of FSH and LH, preventing the further development of eggs during pregnancy. If fertilisation occurs, the developing embryo produces human chorionic gonadotropin (hCG), which maintains the corpus luteum, keeping progesterone levels high. In the absence of pregnancy, falling progesterone removes the inhibition on FSH and LH, and a new cycle begins.
排卵后，黄体分泌孕激素。孕激素抑制FSH和LH的释放，以防在怀孕期间有新的卵子发育。如果受精发生，发育中的胚胎会产生人绒毛膜促性腺激素（hCG），维持黄体，使孕激素水平保持高位。如果没有怀孕，孕激素水平下降解除了对FSH和LH的抑制，新的周期开始。
7. Fertilisation | 受精
Fertilisation is the fusion of a haploid sperm nucleus with a haploid egg nucleus to form a diploid zygote. After sexual intercourse, sperm swim through the cervix and uterus into the oviduct. Only a few hundred out of millions of sperm reach the egg. The sperm must penetrate the zona pellucida and the egg's cell membrane. Once the first sperm enters, the egg membrane changes to prevent other sperm from entering (polyspermy is prevented).
受精是单倍体精子细胞核与单倍体卵子细胞核融合形成二倍体受精卵的过程。性交后，精子游过子宫颈和子宫进入输卵管。数以百万计的精子中只有几百个能到达卵子。精子必须穿透透明带和卵子的细胞膜。一旦第一个精子进入，卵子膜会发生变化，防止其他精子进入（防止多精入卵）。
The nuclei of the sperm and egg fuse, restoring the diploid chromosome number. The zygote immediately begins to divide by mitosis as it travels along the oviduct towards the uterus. This ball of cells is called a morula, which then becomes a blastocyst before implantation.
精子和卵子的细胞核融合，恢复了二倍体染色体数目。受精卵在沿着输卵管向子宫移动的过程中，马上开始通过有丝分裂进行分裂。这一团细胞称为桑葚胚，接着在着床前发育为胚泡。
8. Implantation and Pregnancy | 着床与妊娠
About a week after fertilisation, the blastocyst reaches the uterus and embeds itself into the thickened endometrium. This process is called implantation. The outer layer of the blastocyst forms the placenta, while the inner cell mass develops into the embryo. The placenta is the organ through which the exchange of materials takes place between the mother and foetus.
受精后约一周，胚泡到达子宫并嵌入增厚的子宫内膜。这个过程称为着床。胚泡的外层形成胎盘，而内细胞团发育成胚胎。胎盘是母体和胎儿之间进行物质交换的器官。
The placenta allows oxygen, water, nutrients (glucose, amino acids) and antibodies to pass from the mother's blood into the foetal blood. Waste products such as carbon dioxide and urea diffuse from the foetal blood into the mother's blood for excretion. The amniotic sac filled with amniotic fluid surrounds the foetus, protecting it from physical shock and temperature changes. The umbilical cord connects the foetus to the placenta.
胎盘使得氧气、水、营养物质（葡萄糖、氨基酸）和抗体能够从母体血液进入胎儿血液。二氧化碳和尿素等代谢废物从胎儿血液扩散到母体血液中以排出。充满羊水的羊膜囊包裹着胎儿，保护其免受物理冲击和温度变化的影响。脐带将胎儿连接到胎盘。
9. Birth | 分娩
After approximately 40 weeks of pregnancy (gestation), labour begins. The hormone oxytocin stimulates strong rhythmic contractions of the uterine muscles, gradually opening the cervix (dilation stage). Once the cervix is fully dilated, the mother is able to push the baby out through the vagina. This is the expulsion stage. After the baby is delivered, the umbilical cord is clamped and cut. The placenta, now called the afterbirth, is expelled shortly afterwards.
大约40周的妊娠期后，分娩开始。激素催产素刺激子宫肌肉强烈而有节律的收缩，逐渐张开子宫颈（扩张阶段）。一旦子宫颈完全扩张，母亲就能用力将婴儿经阴道推出。这是娩出阶段。婴儿出生后，脐带被夹紧并剪断。胎盘（此时称为胞衣）在短时间内排出体外。
10. Contraception | 避孕
Contraception is the intentional prevention of pregnancy. Methods can be hormonal, barrier, chemical or surgical. Hormonal methods such as the contraceptive pill contain oestrogen and progesterone (or progesterone only) to inhibit FSH and LH release, preventing ovulation. The intrauterine device (IUD) prevents implantation. Barrier methods, like condoms and diaphragms, physically prevent sperm from reaching the egg.
避孕是有意识地防止怀孕。方法可分为激素法、屏障法、化学法或手术法。激素法如含有雌激素和孕激素（或仅含孕激素）的避孕药，通过抑制FSH和LH的释放来阻止排卵。宫内节育器（IUD）可防止着床。屏障法，如避孕套和子宫帽，从物理上阻止精子到达卵子。
Surgical methods such as vasectomy (cutting the sperm ducts) for males and tubal ligation (cutting the oviducts) for females provide permanent sterilisation. Natural methods, including the rhythm method (avoiding intercourse around ovulation), are less reliable. The choice of contraceptive method depends on effectiveness, health, convenience and personal beliefs.
手术方法如男性的输精管结扎术和女性的输卵管结扎术，可提供永久绝育。自然避孕法，包括安全期法（避开排卵期），可靠性较差。避孕方法的选择取决于有效性、健康状况、便利性和个人信仰。
11. Sexually Transmitted Infections (STIs) | 性传播感染
Sexually transmitted infections are diseases passed from one person to another through sexual contact. Common examples include HIV/AIDS, caused by the human immunodeficiency virus, which attacks the immune system; gonorrhoea, caused by the bacterium Neisseria gonorrhoeae; and syphilis, caused by the bacterium Treponema pallidum. Chlamydia is another widespread bacterial STI that can lead to infertility if untreated.
性传播感染是通过性接触从一个人传给另一个人的疾病。常见的例子包括：由人类免疫缺陷病毒引起的艾滋病，攻击免疫系统；由淋病奈瑟菌引起的淋病；以及由梅毒螺旋体引起的梅毒。衣原体是另一种广泛的细菌性性传播感染，如不加治疗可能导致不孕。
Many STIs can be treated with antibiotics if diagnosed early. However, some, like HIV, have no cure, though antiviral drugs can manage the condition. Prevention is crucial and includes the use of condoms, limiting sexual partners, and regular health checks. Edexcel IGCSE biology expects you to understand the social and health implications of STIs.
许多性传播感染如果早期诊断，可以用抗生素治疗。然而，像艾滋病这样的疾病虽然无法治愈，但可以通过抗病毒药物进行控制。预防至关重要，包括使用避孕套、限制性伴侣数量和定期体检。Edexcel IGCSE生物学考试要求你理解性传播感染对社会和健康的影响。
12. Summary and Key Points | 总结与要点
Human reproduction is a complex sequence of events that ensures the continuation of the species. Remember the structures and functions of the male and female reproductive systems, the roles of hormones FSH, LH, oestrogen and progesterone in the menstrual cycle, and the events leading from fertilisation to birth. Contraception and the awareness of STIs are important applied topics. When revising, use diagrams to label organs and draw flow charts of hormonal control, ensuring you can describe each stage clearly.
人类生殖是一系列复杂的事件，确保了物种的延续。记住男性和女性生殖系统的结构与功能，月经周期中FSH、LH、雌激素和孕激素的作用，以及从受精到分娩的过程。避孕和对性传播感染的认识是重要的应用性话题。复习时，请使用简图标注器官，并绘制激素调控的流程图，确保你能清晰地描述每个阶段。
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