SPI Biology · Reproduction
Human Reproduction
The testes make sperms and testosterone, the ovaries make eggs and oestrogen, and fertilisation in the oviduct starts a new life that grows in the uterus.
Why this matters
Four questions in the bank: two EASY (the hormones behind puberty, the kind of method a condom is) and two HARD figure questions (the glands of the male system, the follicles of the ovary). The HARD ones need only one more fact each: the glands' fluid protects sperms, and the growing follicle's hormone thickens the lining of the uterus.
Concept 1 of 2: Reproductive organs and sex hormones
Each sex has a pair of glands that make both the gametes and a hormone. The hormone is what changes the body at puberty. The other organs are tubes and glands that carry, feed and protect the gametes.
Definition
- Testes: make sperms and testosterone. They sit outside the body in the scrotum, which is cooler.
- Vas deferens: carries sperms to the urethra. Seminal vesicles and prostate: add fluid that nourishes the sperms; it is alkaline, so it neutralises any acid left from urine and fewer sperms are damaged.
- Ovaries: make eggs (ova) and oestrogen; one egg is released about once a month (ovulation).
- Oviduct (fallopian tube): the egg meets the sperm here; fertilisation happens in the oviduct.
- Uterus: the embryo grows here. Each month its lining (endometrium) thickens, made to grow by oestrogen from the growing follicle; if no egg is fertilised, the lining breaks down and comes out as menstruation.
- After ovulation, the empty follicle becomes the corpus luteum, which makes progesterone to keep the lining ready.
| Organ | Makes | Hormone |
|---|---|---|
| Testes (male) | Sperms | Testosterone Testosterone from the testes, oestrogen from the ovaries: never the other way. |
| Seminal vesicles and prostate | Alkaline fluid that carries and protects sperms | None |
| Ovaries (female) | Eggs | Oestrogen (from the growing follicle) |
| Corpus luteum (in the ovary, after ovulation) | Nothing new; it is the empty follicle | Progesterone |
Oestrogen thickens the uterine lining; progesterone keeps it ready for an embryo.
Practice this conceptself-check · 5 quick reps
The same idea in a practice question:
Practice questionEasy
Example 1 · Reproduction · Human Reproduction
Dramatic changes of body features associated with puberty are mainly because of secretion of
Swapping the sex hormones
Testosterone is made by the testes and oestrogen by the ovaries. An option that puts oestrogen in the testes, or names the thyroid or pituitary as the source, is wrong.
Fertilisation in the uterus
The egg is fertilised in the oviduct. The zygote then moves down and settles (implants) in the wall of the uterus.
Giving the corpus luteum oestrogen's job
The growing follicle's oestrogen makes the uterine lining grow. The corpus luteum, formed after ovulation, makes progesterone.
Concept 2 of 2: Methods of contraception
Contraception stops a pregnancy. Each method works in one of four ways: a physical barrier, a chemical, a change in hormones, or a small operation. The question names a method and asks for its kind.
Definition
- Mechanical (barrier): condom, diaphragm. A physical cover stops sperms from reaching the egg. A condom also protects against sexually transmitted diseases.
- Chemical: spermicidal creams and jellies that kill sperms.
- Hormonal: oral pills that change hormone balance so no egg is released.
- Intrauterine device: the Copper-T, placed in the uterus.
- Surgical: vasectomy (the vas deferens is cut and tied in men) and tubectomy (the oviducts are cut and tied in women).
| Method | Kind | How it works |
|---|---|---|
| Condom | Mechanical (barrier) | Stops sperms reaching the egg The only method here that also guards against sexually transmitted diseases. |
| Spermicidal cream | Chemical | Kills sperms |
| Oral pill | Hormonal | Stops the release of eggs |
| Copper-T | Intrauterine device | Placed in the uterus |
| Vasectomy | Surgical (men) | Vas deferens cut and tied |
| Tubectomy | Surgical (women) | Oviducts cut and tied |
Practice this conceptself-check · 3 quick reps
The same idea in a practice question:
Practice questionEasy
Example 2 · Reproduction · Human Reproduction
A condom is a method of control that falls under the following category:
Vasectomy and tubectomy swapped
Vasectomy is done in men (the vas deferens); tubectomy is done in women (the oviducts, also called fallopian tubes).
Summary — formulas & gotchas at a glance
A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.
Reference tables (2)
Reproductive organs and sex hormones4 rows
| Organ | Makes | Hormone |
|---|---|---|
| Testes (male) | Sperms | Testosterone Testosterone from the testes, oestrogen from the ovaries: never the other way. |
| Seminal vesicles and prostate | Alkaline fluid that carries and protects sperms | None |
| Ovaries (female) | Eggs | Oestrogen (from the growing follicle) |
| Corpus luteum (in the ovary, after ovulation) | Nothing new; it is the empty follicle | Progesterone |
Oestrogen thickens the uterine lining; progesterone keeps it ready for an embryo.
Methods of contraception6 rows
| Method | Kind | How it works |
|---|---|---|
| Condom | Mechanical (barrier) | Stops sperms reaching the egg The only method here that also guards against sexually transmitted diseases. |
| Spermicidal cream | Chemical | Kills sperms |
| Oral pill | Hormonal | Stops the release of eggs |
| Copper-T | Intrauterine device | Placed in the uterus |
| Vasectomy | Surgical (men) | Vas deferens cut and tied |
| Tubectomy | Surgical (women) | Oviducts cut and tied |
Watch out for (4)
- Swapping the sex hormones→ Reproductive organs and sex hormones
- Fertilisation in the uterus→ Reproductive organs and sex hormones
- Giving the corpus luteum oestrogen's job→ Reproductive organs and sex hormones
- Vasectomy and tubectomy swapped→ Methods of contraception
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