BY5 - Sexual reproduction in humans

  • Male reproductive system
  • Femal reproductive system
  • Spermatogenesis
  • Oogenesis
  • Sexual intercourse
  • Acrosome reaction
  • Implantation
  • Pregnancy testing
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Male Reproductive System (structure and function)

Testes - Produce sperm.

Scrotum (external sacs containing testes) - Prevent sperm from overheating.

Penis - Intromittent organ.

Seminiferous tube - Produce testosterone and sperm (site of spermatogenesis).

Epididymis - Where sperm are stored and matured.

Vas deferens - Connects the testes to the urethra.

Seminal vesicle -Adds nutrients.

Prostate gland - Adds alkaline fluid to neutralise and acidity in urine.

Sertoli cells - Nourish sperm.

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Female reproductive system (structure and function

Ovaries - Produce ova/eggs.

Fallopian tube (oviduct) - Where ova are passed from ovary to uterus (fertilisation takes place here.

Uterus (womb) - Has muscular walls that contract. Where implantation takes place.

Endometrium - The mucus membrane that lines the wall of the uterus.

Cervix - The exit canal from the uterus. Dilates during child birth.

Vagina - Receives semen from the male.

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Spermatogenesis is the formation of sperm in the germinal epitheilu of the seminiferous tubule.

Primordial germ cells-----Mitosis (puberty)--->

Spermatogonium (2n)-----Mitosis--->

Primary spermatocyte (2n)-----1st meiotic division--->

Secondary spermatocyte (n)-----2nd meiotic division--->

Spermatids (n)-----Differentiation and maturaty into gametes---> Sperm cells

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Oogenesis is the formation of eggs/ova in the ovary.

Primordial germ cell-----Mitotic divisions--->

Oogonia (2n)-----Mitotic divisions--->

Primary oocyte (2n) - present at birth arrested at prophase I, at puberty completion of meiosis I and onset of meiosis II--->

Secondary oocyte (n) + 1st polar body - arrested at metaphase II----Ovulation/Sperm entry--> Completion of meiosis II-->

Fertilised egg + 2nd polar body

In fertilised egg there is an unequal clevage of cytoplasm to provide nutrients for the developing embryo.

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Sexual Intercourse

  • The penis of a sexually excited male becomes erect as blood under pressure fills the spongy 'erectile tissues'.

  • The vagina of a sexually 'excited' female widens ad becomes lubricated by the secretion of mucus.


  • During sexual intercourse the penis is inserted into the vagina.


  • The movements of the penis resut in the *********** of semen into the vagina.
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Acrosome reaction

1. Sperm cpntact jelly layer.

2. Acrosomeal reaction.

3. Digestion of jelly layer (hydrolytic enzyme activity).

4. Binding to vitelline envelope.

5. Egg cell membrane envelopes sperm cell membrane. Fusion of acrosomal process membrane and egg membrane.

6. Sperm nucleus and centriole enter egg. Sperm nucleus then fuses with egg nuclues.

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After fertilisation the zygote begins to divide by mitosis and a hollow ball of cells called a blastocyst is formed. The development of the zygote continues as it travels down the fallopian tube. After three days the blastocyst reaches the uterus and embeds in the endometrium, this is called implantation.

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Pregnancy Testing

  • Human chorionic gonadotrophin (hCG) is excreted in the urine + high levels act as a confirmation of pregnancy.
  • When the antibodies are bind with the hCG they will be carried upwards as the urine seeps up the stick.
  • When they reach the test region of the kit they bind with immobilised antibodies and it is firmly held in place.
  • As the immobilies antibody complex becomes more and more cncentrated there is a colour build up.
  • The test relies on the reaction between antibodies bound to coloured latex beads and hCG. Causing a colour change (line to appear).
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