Homeostasis - Hormones in human reproduction

Where is an egg fertilised by a sperm cell?

In the oviduct

What do we call a fertilised egg?

Zygote

What does a fertilised egg develop into and how does it do so?

An embryo; the zygote divides by mitosis

where does the embryo implant itself?

into the lining of the uterus

What does this then develop into and how does it do so?

Foetus; embryo divides by mitosis

From where does this foetus obtain what it needs and release its waste products?

The mother's blood via the placenta

What are primary sexual characteristics?

The ones you are born with

What are secondary sexual characteristics?

Develop during puberty as a result of rising oestrogen and testosterone levels

Male only puberty

- voice drops and breaks

- muscle develops

- shoulders and chest broaden

- testes grow and start to produce sperm

Female only puberty

- breasts develop

- menstrual cycle starts

- hips widen

Both male and female puberty

- pubic hair grows

- growth spurt

- increases activity of sweat glands

- body hair/facial hair

- growth of external genialia

- brain changes and matures

which hormone triggers puberty in a male and when?

Testosterone which stimulates sperm production - 9-15yrs old

which hormone triggers puberty in a female and when?

Oestrogen - 8-12yrs

What is the main function of the menstrual cycle?

To prepare the uterus lining for the implantation of an embryo

How long does the menstrual cycle usually last?

28 days

Menstrual cycle step 1

The uterus lining sheds

Menstrual cycle step 2

the egg matures in a follicle in the ovary

Menstrual cycle step 3

The egg is released from the ovary in ovulation

Menstrual cycle step 4

the uterus lining builds up/thickens

Menstrual cycle step 5

the uterus lining is maintained

What is a follicle?

A ball of cells in the ovary in which an egg matures

What happens to the remains of the follicle after ovulation?

When the egg is released, the empty follicle is left behind (the corpus luteum) and secretes progesterone, which maintains the uterus lining

If the egg is not fertilised what happens to the unfertilised egg?

It disintegrates and dies

If the egg is not fertilised what happens to the uterus lining?

It sheds during menstruation

If the egg is not fertilised what happens to the empty follicle?

it breaks down

If the egg is fertilised what happens to the fertilised egg/zygote?

It divides by mitosis to form an embryo

If the egg is fertilised what happens to the uterus lining?

It is maintained to house the implanted embryo

If the egg is fertilised what happens to the empty follicle?

It secretes progesterone to maintain the uterus lining

What gland secretes FSH?

The pituitary gland

What gland secretes oestrogen?

ovaries

What gland secretes LH?

The pituitary gland

What gland secretes progesterone?

The empty follicle in the ovaries

What does FSH stand for?

follicle-stimulating hormone

What does LH stand for?

luteinizing hormone

What hormone stimulates the secretion of oestrogen?

FSH

What hormone stimulates the secretion of LH?

Oestrogen

What is the effect of FSH on the female reproductive system?

Causes an egg to mature in a follicle in the ovary

What is the effect of oestrogen on the female reproductive system?

Causes uterus lining to rebuild

What is the effect of LH on the female reproductive system?

Causes ovulation

What is the effect of progesterone on the female reproductive system?

maintains uterus lining

What hormone does oestrogen inhibit the release of?

FSH

What hormone does progesterone inhibit the release of?

FSH and LH

What hormone does FSH stimulate the release of?

Oestrogen

What hormone does oestrogen stimulate the release of?

LH

What triggers the start of the next menstrual cycle?

the decrease of the progesterone levels

Why might a woman miss her period?

pregnancy, birth control (contraception), being severely underweight

What is the menopause, what causes it and when does it occur?

When a woman permanently stops her menstrual cycle at around 45-55 - caused by the lowering of hormone levels

What is infertility?

When a couple cannot get pregnant (conceive) despite having regular unprotected sex

what are the possible reasons for infertility?

Lack of female hormones, damaged, oviducts, lack of/inactive sperm, age, obesity, eating disorders

what are the ways to treat infertility?

1. using a fertility drug to allow natural conception

2. In vitro fertilisation

What do fertility drugs contain and what do they do?

- artificial FSH and LH to stimulate egg maturation, oestrogen production and ovulation so more eggs released so increased chance of fertilisation

- also stimulates release of oestrogen and progesterone -> thickens and maintains uterus lining to prepare for embryo implantation

What is IVF?

In vitro fertilisation - fertilisation "in glass"

Fertilisation takes place in a lab, in a petri dish and doesn't occur in the female's body

When would IVF be used?

- if oviducts have been damaged/blocked by infection

-if someone has had cancer e.g. cervical, ovarian, uterine, testicular

What are the steps involved in IVF?

1. Mother is injected with synthetic FSH to stimulate the matural of eggs and LH to bring eggs to point of ovulation

2. Eggs are collected from ovary and fertilised with sperm in the lab

3. Zygotes are incubated in special solutions in a warm environment to develop into embryos

4. 1 or 2 embryos are inserted into the uterus to hopefully grow and develop

What are the advantages of IVF?

- Has helped to overcome infertility

- Reduces the chance of passing on a genetic disorder

- Zygotes/embryos/mature eggs can be stored for later

What are the disadvantages of IVF?

- Expensive for NHS and individuals

- not always successful, especially when older

- fertility drugs have health risks

- emotionally and physically stressful

- increases the chances of multiple births which are more likely to lead to stillbirths or premature births which cost lots of money to keep baby alive (1 in 80 to 1 in 5)

What are the ethical concerns of IVF?

- Eggs produced by IVF can be stored until used so if woman dies, doesn't want embryos or relationships splits then they my be destroyed

- Could be combined with embryo screening to make "designer babies" with desirable characteristics

- if embryos aren't used, they're destroyed

What is contraception?

Methods to prevent pregnancy, either by preventing the sperm and egg from meeting, or preventing the implantation of an embryo in the uterus

How do hormonal methods of contraception work?

Oral contraceptives contain hormones

Injection, implant or skin patch of slow release progesterone

Intrauterine device may release a hormone

ALL contain hormones that inhibit FSH/LH production so no eggs mature/released

How do non-hormonal methods of contraception work?

Barrier methods (condoms, diaphragms) prevent sperm reaching an egg

Intrauterine device (copper) prevent implantation of an embryo

Spermicidal agents kill or disable sperm

Abstinence - avoid sexual intercourse when egg may be in oviduct to prevent fertilisation

Surgical methods of male and female sterilisation - sperm ducts to prevent sperm release or oviducts tied to prevent egg travelling to uterus for fertilisation