Reproduction

Reproduction

Topics in Reproduction

• (Review) : Reproductive organs. What does what?

• Fertilisation: The science• The female menstrual cycle• Birth control in males and females: the pros

and cons• The placenta• Breastfeeding

Questions….For us to discuss on Monday…

1. What is the future for male contraception – way more than condoms

2. What are the risks of getting pregnant if you don’t use birth control – on how many days of her cycle can a woman get pregnant?

3. What precisely does drinking alcohol and smoking during pregnancy do to a developing baby?

4. What are the pros and cons of breastfeeding compared with bottle feeding?

Reproductive organs. What does what?

Check the links on the Blog to review anatomy

and function!

Female reproductive tract

Male reproductive tract

Asexual reproduction: Binary Fission

• animation of binary fission

Asexual Reproduction: Budding

Seen in Hydra and other species…

Asexual reproduction: fungal spores…

Why go for sexual rather than asexual reproduction?

Links to explain…1. From the Natural history museum2. A simple explanation

The basic vocabulary of sexual reproduction

• Gametes (sex cells) are produced by gonads (sex organs – testes and ovaries)

• Gametes are produced through meiosis (reduction division – and have the haploid (n) number of chromosomes

• Female gametes are eggs (large, stationary)• Male gametes are sperm (small, motile)• Gametes join together at fertilisation to produce a zygote

(diploid number of chromosomes, 2n)• After fertilisation, the zygote grows by mitosis, with the full

(2n) chromosome set in every cell

Comparing the ovum and the sperm

The egg is the largest cell, while the sperm is the smallest in the human

body

Fertilisation and embryonic growth

Male sperm production: produced in the testes under influence of testosterone

Testosterone effects

Romantic relationships and testosterone…

According to wikipedia…• Falling in love decreases

testosterone in men but increases it in women

• Testosterone ‘returns to normal’ after the honeymoon period

• Fatherhood decreases testosterone levels

• ‘competition’ affects testosterone levels

Sperm are delicate…

• Sensitive to heat• Sensitive to

environmental oestrogens (Phyto-oestrogens in plants e.g. SOY, Beer), chemicals

• Link - environmental oestrogens 'wreck' sperm...

Female egg production: Produced in the ovaries…

• Eggs are produced pre-birth• Eggs are arrested in prophase

I of meiosis until puberty• From puberty until the

menopause, one egg will be produced each menstrual cycle under hormonal control (oestrogen from the overies, FSH and LH from the pituitary gland)

• The egg is the largest cell in the body

Female menstrual cycle

• An animated version…• …and a detailed diagram• …and a movie!

Hormones of the menstrual cycle

Hormone Site of secretion Main Effects and site of action

GnRH Hypothalamus Stimulates release of FSH and LH from pituitary gland

FSH Pituitary gland Stimulates growth of follicles in the ovary

LH Pituitary gland Promotes ovulation(LH surge) and development of corpus luteum

Oestrogen Ovary (developing follicle) At high level, promotes LH surge. Promotes growth and repair of the uterine lining

Progesterone Ovary (from follicle following ovulation)

Keeps uterne lining thick and well supplied with blood to support pregnancy

Oral contraceptives interfere with the normal menstrual cycle

• Pills exploit feedback controls over hormone secretion

• They contain combinations of oestrogen and progesterone OR progesterone only

• 100% effective if used properly

Combination pill• They contain combinations of

oestrogen and progesterone • You take the hormone pills

for 7 days, and then sugar pills for 7 days, long enough for menstruation to occur but not long enough for ova to develop

• Combination pills can be monophasic, biphasic or triphasic (dose increasing in 1 or 2 stages)

‘Mini pill’

• Low-dose progesterone only – for 28 days

• Ovulation occurs• Uterus is not favourable

for implantation• Less reliable• Safer for older women,

breastfeeding women

Side effects of the pill…

• Sore boobs• Mood swings• Headaches• Can affect blood

pressure• No protection aginst

STI’s

Alternatives to the pill for women: contraceptive patch

Alternatives to the pill: contraceptive ring

• Hormones (oestrogen, progesterone) released into the vagina

• Lower doses of hormones are needed

• Just as reliable as the pill

• Lower hormone doses so more reliable…

Other methods of contraception: Barrier methods

Natural methods of contraception

Natural methods of contraception: Basal body temperature

Pregnancy!

Hormones: What happens during pregnancy?

Placenta• Baby is called a foetus from 8 w,

when embryo has all of its major structures

• Developing baby is totally dependent on mother for nutrients, oxygen and elimination of wastes

• The placenta is the specialised organ that performs this role

• Placenta also produces hormones to help maintain pregnancy

• placenta is joined to foetus by the umbilical cord

Structure of the placenta• Note that foetal blood and

maternal blood do not mix• Oxygen and nutrients from

the mother diffuse into the capillaries of the chorionic villae

• Carbon dioxide and other wastes leave the foetus through the umbilical arteries, pass into the capillaries of the villi and out into the maternal blood