(2) The male and female reproductive systems

(2a) The male reproductive system

The sperm male sex cells (male gametes) are made in the testes after puberty, they are also involved with the production of the hormone testosterone.

The scrotum (scrotal sacs) protects and helps with the thermoregulation of the testicles by keeping the temperature of the testis several degrees below the average body temperature, which is an essential factor for sperm production.

The sperm duct (ejaculatory duct) delivers sperm into the urethra, adding secretions and additives from the prostate gland necessary for sperm function.

So, the sperm moves from the testes into the sperm duct.

The seminal vesicle gland secretes a fluid that mixes with the sperm, and the prostate gland secretes a slightly alkaline fluid that also forms part of the seminal fluid, the fluid that carries the sperm.

The penis is the external male reproductive organ and ejaculates semen into the woman's vagina during sexual intercourse (copulation).

The urethra is the tube that allows urine to flow out of the body from the penis as well as the channel through which the semen flows.

(2b) The female reproductive system

(both female diagrams need to be appreciated in terms of structural features and their function)

Egg - the female sex cell (gamete)

Ovaries - the organ where the eggs (ovum) are produced and stored and the site of production of the hormones estrogen and progesterone. One or both of the ovaries releases an egg every 28 days.

Oviducts (fallopian tubes) - when an egg is released it travels down this tube into the uterus where it may interact with a sperm from the vagina following sexual intercourse.

Umbilical cord - connects the placenta to the growing foetus - baby, oxygen, nutrients and waste substances pass through it (see below).

Placenta - a temporary organ that develops in the uterus during pregnancy and acts as an interface between the growing foetus and the mother's body and provides dissolved oxygen and nutrients to the growing baby and removes waste products (excretory substances) at the same time (all of which pass through the umbilical cord). The placenta also provides a barrier to protect the developing fetus-baby from harmful toxins and pathogens. However some toxins and pathogens can pass through e.g. the rubella virus, nicotine from smoking and alcohol (ethanol) from drinking alcoholic drinks.

Uterus (womb) - a hollow muscular organ located in the female pelvis between the bladder and rectum in which the foetus-baby develops after a fertilised egg is implanted in the uterus lining.

Amniotic (amnion) membrane - the innermost layer of the foetal membranes which surrounds the developing foetus and forms the amniotic cavity.

Amniotic sac and amniotic fluid - the amniotic sac surrounds the foetus during pregnancy and contains the amniotic fluid during gestation and in which the embryo is situated giving it a cushioning effect. Amniotic fluid is ~97% water and constantly renewed. The amniotic fluid also contains cells from the foetus, which will allow prenatal diagnosis through amniocentesis - allowing a check to see if the baby has a genetic or chromosomal condition like Down's syndrome.

Cervix - the lower, narrow end of the uterus that forms a canal between the uterus and vagina.

Vagina - a tube that connects the vulva (outer part of female genitals) with the cervix and uterus, penetration by the male penis allows sperm to travel up into the uterus. Menstrual blood leave the body through the vagina as well as expansion to allow the birth of a child.

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(2c) Reminders - hormones and the regulation and development of secondary sexual characteristics

During puberty sex hormones play an important role in the sexual development of the young body combined with a growth spurt.

In young females, estrogen levels rise during puberty and this increase leads to secondary sex characteristics like breast and hip development and changes in overall body shape (more curvier).

Later in puberty, in a girl's ovaries, eggs begin to mature and the menstrual cycle can begin i.e. a matured egg is released every 28 days (ovulation and periods start).

In young males, testosterone levels rise during puberty and this increase causes boys to develop deeper voices, bigger muscles, and body and facial hair.

It also helps the testes produce sperm, penis enlarges, and testosterone it plays a role in speeding a boy's growth in height during puberty.

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Key points about the male and female reproductive systems and development of secondary sexual characteristics

Source of information is based on textbooks & syllabus-specifications for students taking the AQA GCSE, Edexcel GCSE and OCR GCSE level biology examinations (~US grades 9-10).

Revision notes for biology students on the male and female reproductive systems and the development of secondary sexual characteristics.

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Human Reproductive Systems

Purpose of the Reproductive System

• To produce gametes (sperm in males, eggs in females).

• To enable fertilisation and support the development of offspring.

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Male Reproductive System

Key Structures & Functions:

Structure	Function
Testes	Produce sperm and the hormone testosterone.
Scrotum	Sac that holds the testes outside the body to maintain lower temperature.
Epididymis	Stores and matures sperm.
Sperm duct (vas deferens)	Transports sperm from testes to urethra.
Seminal vesicles & prostate gland	Add fluids to sperm to form semen.
Urethra	Carries semen (and urine) out of the body through the penis.
Penis	Transfers semen into the female during sexual intercourse.

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Female Reproductive System

Key Structures & Functions:

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Secondary Sexual Characteristics

These are physical changes that occur during puberty, triggered by sex hormones.

In Males (caused by testosterone):

• Growth of facial, pubic, and body hair

• Voice deepens

• Muscle mass increases

• Penis and testes enlarge

• Sperm production begins

In Females (caused by oestrogen):

• Development of breasts

• Growth of pubic and underarm hair

• Hips widen

• Start of menstrual cycle

• Ovaries begin releasing eggs

Some changes occur in both sexes, such as growth spurts, emotional changes, and increased interest in sex.

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Why This Is Important in Human Biology

• Helps explain sexual reproduction and fertility.

• Shows how the endocrine system controls development.

• Links to topics like contraception, pregnancy, and puberty education.

• Reinforces understanding of hormonal control and body systems.

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Exam Tips

• Use key terms: testes, ovaries, sperm, egg, testosterone, oestrogen, puberty, secondary sexual characteristics.

• Be able to label diagrams of both reproductive systems.

• Understand the functions of each structure and the hormonal changes during puberty.

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Keywords, phrases and learning objectives for this part on the male and female reproductive systems

Be able to interpret detailed diagrams of the male and female reproductive systems (including the nature and function of the testes ,sperm duct, penis, urethra, egg, ovaries, cervix, vagina ) and describe the development of secondary sexual characteristics in the puberty of girls and boys.

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