reproduction Flashcards
ovulation
at puberty, ova begin to mature and one is released approximately every 28 days
hormones involved in regulating the menstrual cycle
- FSH (follicle stimulating hormone)
- oestrogen
- LH (luteinising hormone)
- progesterone
FSH
- follicle stimulating hormone
- produced by the pituitary gland
- acts on target structures in the ovaries
- stimulates ovary to to develop a follicle containing an egg (ovum maturation)
- stimulates ovary to produce oestrogen
oestrogen
- produced by the ovaries
- stimulates the uterus lining to thicken
- a steroid hormone
LH
- luteinizing hormone
- produced by the pituitary gland
- acts on target structures in the ovary
- stimulates the mature follicle to release the ovum (ovulation) in the middle of the cycle (around day 14)
progesterone
- secreted by the empty follicle in the ovary (the yellow body/corpus luteum)
- maintains the lining of the uterus during the 2nd half of the cycle so that a fertilised egg may implant
- decreasing progesterone levels cause the thickened uterus lining to break down and be discharged (menstruation)
hormone action
- Oestrogen and progesterone inhibit the production of LH and FSH
- if oestrogen did not inhibit the production of FSH, the ovaries would be stimulated to produce many follicles containing ova during the cycle
- this could result in many ova being released and being fertilised during sexual reproduction
contraception
- high levels of oestrogen and progesterone inhibit FSH production and egg/ovum maturation -> ovulation can’t take place
- these hormones, taken every day, keeps blood levels high
- progesterone also stimulates the production of thick cervical mucus so that sperm are unable to enter the uterus to fertilise an egg
cervix
the opening to the uterus
oral pill (hormonal)
-combined oestrogen and progesterone or progesterone only
Problems: -not 100% effective
-side effects are possible (mainly due to oestrogen) e.g. headaches, nausea, irregular menstrual bleeding, fluid retention
-no protection from STDs
-relies on remembering to take it daily
skin patch (hormonal)
- contains oestrogen and progesterone
- a small patch stuck to the skin, changed each week.
implant (hormonal)
- inserted under the skin of the arm
- releases a continuous amount of progesterone
- lasts for up to three years
injection (hormonal)
- contains progesterone
- each dose lasts 2 to 3 months
intrauterine devices (hormonal)
- T-shaped devices inserted into the uterus that prevent the implantation of an embryo
- plastic intrauterine devices which release progesterone
hormonal methods
can be used as a contraceptive, but do not decrease the risk of sexual transmission of communicable diseases
barrier methods (non-hormonal)
- condoms – worn over the penis to prevent sperm from entering the vagina (only contraceptive device that protects against STDs)
- diaphragm – a shallow plastic cup that fits over the cervix and is used with a spermicide
- spermicide – a substance introduced into the vagina to kill sperm or make them inactive – more effective when used with a diaphragm
intrauterine devices (non-hormonal)
- T-shaped devices inserted into the uterus that prevent the implantation of an embryo
- copper intrauterine devices prevent sperm from surviving in the uterus
surgical methods (non-hormonal)
- permanent sterilisation, cutting or tying structures involved in human reproduction:
- female: oviducts that connect the ovaries to the uterus
- male: sperm duct between the testis and the penis
- very small chance of the structures reconnecting
natural methods (non-hormonal)
- avoiding sexual intercourse when an egg may be in the oviduct (most fertile time) – not very effective
- abstinence – no sexual intercourse – 100% effective
testosterone
- stimulates sperm production
- a steroid hormone
asexual reproduction
- requires only one parent
- gives rise to genetically identical offspring
sperm
- contain many mitochondria in the mid-section to provide energy from the sperm to swim
- nucleus is in the head of the sperm
fertilisation
to prevent many sperms fertilising an egg, the sperm changes the structure of the egg cell as soon as it makes contact with the egg cell’s surface
