Definition
The testes produce sperm (spermatogenesis) within their seminiferous tubules, and also produce testosterone.
After leaving the testis, sperm are stored and mature in the epididymis, before travelling through the vas deferens.
The seminal vesicles produce a sugary (fructose-rich) fluid that nourishes sperm, providing an energy source for their journey. The prostate gland adds further fluid that helps sperm survive and stay mobile. These fluids combine with sperm to form semen, which passes out through the urethra.
Definition
The acrosome (found at the head of a sperm cell) contains enzymes that help the sperm penetrate the protective layers surrounding an egg during fertilization.
The structure of a sperm cell directly relates to its function: a streamlined head containing genetic material and the acrosome (for penetrating the egg), a midpiece packed with mitochondria (providing energy for movement), and a long tail/flagellum (providing propulsion) — every part is specialized purely for successfully reaching and fertilizing an egg.
Definition
Testosterone is the hormone primarily responsible for the development of male secondary sexual characteristics (like facial hair, a deeper voice, and increased muscle mass), alongside driving sperm production.
Definition
Oogenesis (egg formation) takes place in the ovaries.
The Fallopian tubes carry the egg released from the ovary towards the uterus, and are also the usual site where fertilization actually occurs if sperm are present.
After an egg is released from the ovary (ovulation), it travels into the Fallopian tube — if fertilized there, it continues to the uterus to implant; if not fertilized, it eventually breaks down and is shed during menstruation.
The cervix is the narrow lower part of the uterus, connecting it to the vagina — it functions as a protective barrier/opening that can dilate widely during childbirth. The vagina serves as the passage connecting the cervix to outside the body, receiving sperm during intercourse and serving as the birth canal during delivery.
Definition
Oestrogen and progesterone (produced by the ovaries) together regulate the female reproductive cycle and female secondary sexual characteristics — oestrogen is more associated with driving the buildup of the uterine lining and developing secondary sexual characteristics, while progesterone is more associated with maintaining the uterine lining to support a potential pregnancy.
Definition
GnRH (gonadotropin-releasing hormone) is released by the hypothalamus and stimulates the pituitary gland to release LH (luteinizing hormone) and FSH (follicle-stimulating hormone), which in turn act on the testes or ovaries.
A surge in LH directly triggers ovulation (the release of an egg from the ovary).
Definition
Gametogenesis is the process of forming gametes (sperm and eggs); it involves meiosis (a special type of cell division that halves the chromosome number, so gametes are haploid () rather than diploid () like body cells — this is essential so that when a sperm and egg fuse at fertilization, the resulting cell has the normal diploid number again).
Definition
Spermatogenesis chart: a diploid () primary spermatocyte undergoes meiosis I to form two haploid () secondary spermatocytes, which undergo meiosis II to form four haploid () spermatids, which mature into four haploid () sperm.
Oogenesis chart: a diploid () primary oocyte undergoes meiosis I to form one haploid () secondary oocyte plus one haploid () polar body (which typically degenerates); the secondary oocyte undergoes meiosis II (usually completed only if fertilized) to form one haploid () mature egg plus another polar body.
Example 1 — comparing gamete output
Compare spermatogenesis and oogenesis in terms of the number of gametes produced.
- Each primary spermatocyte undergoes two full meiotic divisions with all resulting cells developing into functional sperm.
- Each primary oocyte also undergoes two meiotic divisions, but most of the cytoplasm is retained in just one cell each time, with the rest discarded as small polar bodies.
Answer: Spermatogenesis produces functional sperm per primary spermatocyte; oogenesis produces only functional egg per primary oocyte (plus non-functional polar bodies)
Remember
Only one functional egg is usually produced from one primary oocyte (rather than four, as with sperm) because the divisions in oogenesis are unequal — almost all of the cytoplasm, nutrients, and cellular resources are concentrated into a single large cell (the egg) at each division, with the rest discarded as small polar bodies, since a large store of resources gives a fertilized egg a much better start supporting early development than four smaller cells would.
Definition
Not all sexually transmitted diseases (STDs) are caused by the same type of pathogen — different STDs are caused by different types of pathogens, including bacteria (e.g. gonorrhoea, syphilis), viruses (e.g. HIV, herpes), and other organisms (e.g. certain parasites or fungi). One serious complication of an untreated STD can be infertility (from damage to reproductive organs) or, in severe cases, life-threatening illness.
AIDS (Acquired Immunodeficiency Syndrome) is caused by HIV (Human Immunodeficiency Virus), which attacks and gradually destroys the immune system's cells (specifically certain white blood cells), leaving the body increasingly vulnerable to infections and diseases it would normally fight off easily — this is exactly why AIDS itself isn't usually what kills a patient directly, but rather the opportunistic infections that a severely weakened immune system can no longer control.
Definition
Two major ways HIV can be transmitted: through unprotected sexual contact with an infected person, and through contact with infected blood (e.g. sharing needles, contaminated blood transfusions) — it can also be transmitted from an infected mother to her child during pregnancy, birth, or breastfeeding.
Early signs and symptoms of AIDS (HIV infection) can include fever, fatigue, swollen lymph nodes, and flu-like symptoms, though a person can carry HIV for years without obvious symptoms before the condition progresses.
Definition
There is currently no cure for AIDS, but antiretroviral therapy (ART) — a combination of drugs — can effectively control HIV, keeping the virus suppressed to very low levels, allowing infected individuals to live long, largely healthy lives, and greatly reducing the risk of transmitting the virus to others.
Remember
Steps to prevent HIV transmission include practising safe sex (using condoms), avoiding sharing needles or other blood-contaminated items, ensuring blood used for transfusions is properly screened, and pregnant individuals with HIV receiving appropriate medical treatment to greatly reduce the risk of transmission to their child.
Quick Recap
- ●Male system: testes (sperm testosterone) epididymis (stores/matures) vas deferens; seminal vesicles/prostate add fluid semen urethra
- ●Sperm: acrosome (enzymes to penetrate egg), midpiece (mitochondria, energy), tail (movement)
- ●Female system: ovaries (eggs oestrogen/progesterone) Fallopian tube (fertilization site) uterus cervix vagina
- ●GnRH (hypothalamus) LH/FSH (pituitary) testes/ovaries; LH surge ovulation
- ●Gametogenesis meiosis, . Spermatogenesis: 1 primary spermatocyte 4 sperm. Oogenesis: 1 primary oocyte 1 egg polar bodies (unequal division concentrates resources)
- ●STDs: different pathogens (bacteria, viruses, etc.); HIV attacks immune cells AIDS; spreads via sexual contact/blood/mother-to-child; no cure, but ART controls it effectively
