3.13 understand the roles of oestrogen and testosterone in the development of secondary sexual characteristics

Female effects of oestrogen:

1. Breast development
2. Growth of body hair
3. Beginning of menstrual cycle

Male effects of testosterone:

1. Growth of penis and testes
2. Facial and body hair
3. Muscle development
4. Sperm production

3.12 understand how the developing embryo is protected by amniotic fluid

During the development of the embryo, the amnion is developed and amniotic fluid is produced.

Functions:
- cushions developing embryo and fetus and protects it against blows to the abdomen.
- allows fetus to move around and develop a muscular system.
- enters fetus lungs and allow development there.

3.11 describe the role of the placenta in the nutrition of the developing embryo

- placenta forms as an embryo develops
- developing fetus is connected to the placenta
- allows diffusion of glucose, amino acids and oxygen from the mother's blood to fetus and waste carbon dioxide and urea taken away.

Placenta: connection of the fetus and the mother between uterine wall via the umbilical cord that allows the exchange of materials between the mother and the fetus.
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Explanation:

• Placenta is lined with villi to increase surface area for diffusion of materials between mother and fetus.
• Fetal capillaries and maternal capillaries are very close therefore there is a short diffusion distance, and diffusion will be efficient.

Materials including oxygen, water, vitamins, minerals and antibodies are carried from mother to fetus. Waste materials are carried from fetus to mother. This means that drugs such as nicotine and alcohol can also cross placenta and potentially damage the fetus.

Key Idea: There is NO mixing of maternal and fetal blood in the placenta.

This is because:

1. maternal blood has much higher pressure than fetal blood. If fetus were to be connected to maternal circulatory system, its blood vessels would burst.

2. fetus and mother have different blood groups and can trigger clotting.

Therefore what happens in placenta is:

- mother's blood empties into spaces in placenta and babies' blood is carried by umbilical artery into capillaries in villi.

3.10B understand the roles of FSH and LH in the menstrual cycle

Oestrogen:
- produced in ovaries
- causes lining in uterus (endometrium) to grow
- inhibits the release of LH (Luteinising Hormone) which causes ovulation

Progesterone:
- produced in ovaries at around day 14
Progesterone has two main functions:
1. maintaining uterus lining (endometrium) during the second half of the cycle. When the level of progesterone decreases, the lining breaks down.
2. Inhibits the release of LH and FSH. Progesterone also causes the pituitary gland to stop secreting hormones FSH and LH so a new cycle is never started. For this reason most birth control pills contain progesterone

FSH (Follicle-stimulating Hormone):
- produced in pituitary gland
- causes egg to mature
- stimulates ovaries to produce oestrogen
- estrogen inhibits the release of FSH

LH (Luteinising Hormone):
- produced by pituitary gland
- stimulates ovulation

2.95B understand the sources, roles and effects of the following hormones: FSH and LH

Oestrogen:
- produced in ovaries
- causes lining in uterus (endometrium) to grow
- inhibits the release of LH (Luteinising Hormone) which causes ovulation

Progesterone:
- produced in ovaries at around day 14
Progesterone has two main functions:
1. maintaining uterus lining (endometrium) during the second half of the cycle. When the level of progesterone decreases, the lining breaks down.
2. Inhibits the release of LH and FSH. Progesterone also causes the pituitary gland to stop secreting hormones FSH and LH so a new cycle is never started. For this reason most birth control pills contain progesterone

FSH (Follicle-stimulating Hormone):
- produced in pituitary gland
- causes egg to mature
- stimulates ovaries to produce oestrogen
- estrogen inhibits the release of FSH

LH (Luteinising Hormone):
- produced by pituitary gland
- stimulates ovulation

3.9 understand the roles of oestrogen and progesterone in the menstrual cycle

There are four stages in the menstrual cycle:
Stage 1: Day 1 - Start of menstrual cycle. Uterus lining (endometrium) breaks down for around 4 days.
Stage 2: Day 4~14 - Uterus lining builds up again into thick spongy layer full of blood vessels, ready to receive a fertilised egg.
Stage 3: Day 14 - Ovulation; when a matured egg is released from ovary
Stage 4: Day 28 - Uterus wall is maintained for another 14 days until day 28. If no fertilised egg lands on uterus wall by day 28, cycle repeats

Oestrogen:
- produced in ovaries
- causes lining in uterus (endometrium) to grow
- inhibits the release of LH (Luteinising Hormone) which causes ovulation

Progesterone:
- produced in ovaries at around day 14
Progesterone has two main functions:
1. maintaining uterus lining (endometrium) during the second half of the cycle. When the level of progesterone decreases, the lining breaks down.
2. Inhibits the release of LH and FSH. Progesterone also causes the pituitary gland to stop secreting hormones FSH and LH so a new cycle is never started. For this reason most birth control pills contain progesterone

FSH (Follicle-stimulating Hormone):
- produced in pituitary gland
- causes egg to mature
- stimulates ovaries to produce oestrogen
- estrogen inhibits the release of FSH

LH (Luteinising Hormone):
- produced by pituitary gland
- stimulates ovulation

3.8 understand how the structure of the male and female reproductive systems are adapted for their functions

Male Reproductive System:


Glands: Produces semen that will provide sperm cells with nutrients.
Sperm Ducts: Sperm passes through sperm duct to be mixed with fluids produced by glands.
Urethra: Tube inside the penis that carries urine or semen. Ring of muscle prevents the two mixing.
Testes: Contained in the scrotum, produces sperm and testosterone.
Penis: Passes urine and semen out.


Female Reproductive System:

Fallopian tube: connects ovary to the uterus, lined with ciliated cells to push released egg into the uterus for fertilisation.
Ovary: produces female gametes (ova) which will mature and develop when FSH is released.
Uterus: muscular bag with a soft lining (endometrium) where a fertilised egg will be implanted to develop into a fetus.
Cervix: a ring of muscle to keep developing fetus in place during pregnancy.
Urethra: tube that passes urine out of the body.
Vagina: muscular tube that leads to the uterus

3.2 understand that fertilisation involves the fusion of a male and female gamete to produce a zygote that undergoes cell division and develops into an embryo

• Sexual reproduction is when a male gamete (sperm) and a female gamete (ova) combine to form offspring genetically different to the parents. 
• Gametes (sex cells) are sperm cells and egg cells produced by the testes and the ovaries respectively. They are produced by meiosis.
• Gametes are haploid, meaning that they only have 23 chromosomes. A full cell has 46 chromosomes. 
• In fertilisation, the gametes fuse to form a zygote which is a diploid cell of 46 chromosomes. (23 from each gamete). The zygote will inherit characteristics of both parents, therefore, it will not be genetically identical to the parent. It will result in genetic variation. 
• The zygote will undergo mitosis cell division and develop into an embryo.

3.1 understand the differences between sexual and asexual reproduction

Sexual reproduction: joining of 2 gametes produced by Meiosis from 2 parents to produce non-identical offspring, inheriting characteristics of both parents.

Advantages of Sexual Reproduction:
- Increases variation
- Organisms can adapt to a new environment
- Diseases less likely to affect whole population due to variation

Disadvantages of Sexual Reproduction:
- takes long time and energy to find mates
- not possible for isolated members


Asexual Reproduction: Involves only one parent that produces offsprings genetically identical via Mitosis.

Advantages of Asexual Reproduction:
- The population can be increased rapidly
- Can exploit suitable environments quickly

Disadvantages of Asexual Reproduction:
- Decreases variation
- Vulnerable to change in conditions
- disease likely to affect the whole population.

2.94 understand the sources, roles and effects of the following hormones: testosterone, progesterone and oestrogen

Hormone	Source	Role	Effects
Testosterone	Testes	Main male sex hormone	Promotes male secondary characteristics
Progesterone	Ovaries	Supports pregnancy	Maintains lining of uterus
Oestrogen	Ovaries	Main female sex hormone	Controls the menstrual cycle and promotes female secondary sexual characteristics