Reproduction Flashcards
What is sexual reproduction?
Sexual reproduction involves the production of male and female gametes (sex cells) which then fuse together (fertilisation)
What does sexual reproduction lead to?
Variety in the off-spring
What are sperm and egg cells known as?
Specialised cells known as gametes
What is Meiosis?
These cells are produced by a type of cell division called meiosis
What are gametes?
Haploid
What does haploid mean?
Half the number of chromosomes (23)
Why do sperm and egg cells have to be haploid?
So after fertilisation you have a diploid organism
Where are sperm produced?
Testes
What is the male hormone called?
Testosterone
How big is the human sperm cell?
1/20th centimetres long
What does the flagellum do?
Beats rapidely to propel sperm
What does the streamlined head contain?
Enzymes
What are egg cells called?
Ova
Where are egg cells produced?
Ovaries
What are the female hormones called?
Oestrogen and progesterone
What do egg cells have?
A haploid nucleus which is produced by meiosis but they are much larger than sperm cells
Why so sperm need a lower temperature, and what temperature is this?
To develop normally and 35°C
Where does the scrotum lie?
Outside the body
Where does the sperm duct lead from?
Each of the testes to a point just below the bladder
Where does the sperm duct join with?
Urethra - which runs down the centre of the penis
Where is the urethra connected to?
Bladder as well as the sperm ducts.
What does the urethra carry?
Urine from the bladder as well as sperm.
BUT NEVER AT THE SAME TIME
Where is the prostate gland?
At the junction of the sperm ducts and urethra.
What does the glands in the penis create?
Semen for the sperm to swim in
What is the protective covering on the penis called?
Foreskin
How often is an egg released from the ovaries?
Every month
How are ovaries connected to the uterus?
By oviducts
Where does fertilisation occur?
Uterus
The uterus has a tight neck called…
The cervix
How many sperm are released from a male?
500 million sperm
Where does sperm and egg meet up?
In the oviduct
What is the journey of the sperm to the egg?
Vagina - cervix - uterus - oviducts
What is the fertilised egg cell know as?
Zygote - this is the first cell of a new individual
As the zygote travels down the oviduct….
It divides by meiosis many times to form a ball of cells known as an embryo
What is the embryo supported by?
Amnion, amniotic fluid, fluid, umbilical cord and placenta
Give an example of mechanical contraception?
Condom
What is the mechanical method of contaception?
A barrier that prevents sperm entering the vagina
What is an advantage of mechanical contraception?
Easily obtained. Protects against STIs eg HIV
What is a disadvantage of mechanical contraception?
Unreliable if not used properly
What is an example of chemical contraception?
Contraceptive pill
What is the method of chemical contraception?
Taken regularly by the female. Prevents ovualation by changing hormone levels
What is an advantage of chemical contraception?
Very reliable - when taken correctly it is 99% effective
What is a disadvantage of chemical contraception?
Female needs to remember to take the pill. Side effects. Does not protect against STIs
What is a side effect of chemical contraception?
Weight gain, mood swings or an increased risk of blood clots
What is the surgical contraception example number 1?
Vasectomy
What is a surgical contraception example 2?
Female sterilisation
What is a surgical contraception method 1?
Sperm tubes are cut preventing sperm entering the penis
What is surgical contraception method 2?
Oviducts are cut preventing fertilisation
Both advantages of surgical contraception?
Virtually 100% reliable
What are both disadvantages of surgical contraception?
Difficult or impossible to reverse
Where does the embryo become attached?
The embryo becomes implanted to the wall of the uterus
What will the uterus have developed?
A thick lining that holds and nourishes the embryo
What does the embryo do after implantation?
Differentiates to produce a variety of tissues and organs
What is the embryo reffered to after a few weeks?
A foetus
What is the amnion?
A protective membrane that develops around the embryo.
What does the amnion contain?
Amniotic fluid - which cushions the embryo from knocks or bumps
What does the umbilical vein carry?
Carries substances from the mother to the foetus
What does the umbilical artery carry?
Carries substances from the foetus to the mother
What travels through the umbilical vein?
Oxygen, glucose, amino acids, vitamins, minerals, water and hormones
What travels through the umbilical artery?
Carbon dioxide and urea
What is the placenta very rich in?
Maternal blood vessels
What in the placenta are very close together?
The maternal and foetal blood systems.
Why are the 2 blood systems separe in the placenta?
To allow diffusion of gasses wnd nutrients to take place in either direction.
Why is it important that the maternal and foetal blood not mix in the placenta?
The mother and foetus may be of different blood groups - if they mixed they would clump and cause death.
What is the placenta adapted for?
Diffusion of material between mother and foetus by having a surface area.
What is the placenta subdivided into?
Many villi that extend the uterine wall - these villi increase the surface area contact between maternal and foetal blood systems.
What is it called when people avoid having sex with a women when the women is ovulating?
Rhythm or natural methods.
Why so sone people choose to avoid having sex with women during ovulation
Religious or ethical reasons
Why is it a much less effective method compared to other methods?
In many women the menstrual cycle is irregular, making it difficult to know exactly when an egg is being released
Where is the site of production of testosterone?
Testes
Where is the site of the production of oestrogen?
Ovaries in females
These hormones are important in the development of the…
Secondary sexual characteristics
What is an argument for IVF
Gives an infertile couple chance to have a child, or same sex.
What is the 1st argument against IVF?
There are more embyros produced than are used in IVF and therefore some may be destroyed which can raise religious objections.
What is the 2nd argument against IVF?
Expensive
What is step 1 of fertility treatment?
Egg production stimulated by hormone therapy
What is step 2 of fertility treatment?
Eggs retrieved from ovary
What is step 3 of fertility treatment?
Sperm sample provided
What is step 4 of fertility treatment?
Eggs and sperm combined to allow fertilization
What is step 5 of fertility treatment?
Fertilized eggs introduced into uterus
What is the controvery with fertility treatment?
It is possible to screen embryos to check for abnormalities or for particular characteristics.
What are causes of infertility in males?
Do not produce enough sperm
Sperm may be unhealthy (without tails)
Impotence
Complications of some STDs
What is impotence
Inability to achieve and maintain an erection
Why may sperm be unhealthy?
Smoking or taking excess alcohol
What will same sex couples also need to have kids?
IVF
Cause 1 of infertility in females
Oviducts may be blocked or twisted (due to infections)
Cause 2 of infertility in females
Complications of some STDs
Cause 3 of infertility in females
Failure of ovaries to produce eggs
Cause 4 of infertility in females
Vagina may be hostile, i.e to sperm entering, eg. The lining may be too thick or acid
Cause 5 of infertility in females
Lining of the uterus does mot develop properly to enable implantation to occur
How does the hormone treatment work?
Fertility drugs are given to a female to increase egg population. This may solve the problem of low egg production
How does IVF treament work, step 1?
The women is given fertility drug to produce multiple eggs
How does IVF treament work, step 2?
The eggs are collected from the ovaries surgically
How does IVF treament work, step 3?
Several succesful embryos are placed in the woman’s uterus - (she will have undergone hormonal treatment to ensure uterus is ready)
How does IVF treament work, step 4?
If the process is successful an embryo will implant in the uterus lining
How does IVF treament work, step 5?
Only a small number of embryos are placed in the uterus to give balance between a successful pregnancy and avoiding multiple births
How long does the mentrual cycle last?
28 days
What is menstraution?
The blood - rich uterine lining breaks down (if pregnancy dows not occur) and is passed out of the body
The uterine lining repairs iteseld and…
Builds up again in preparation of implantation should pregnancy result
What is ovulation?
Egg is released from ovary
What happens to the uterine if pregnancy does occur?
The uterine lining will become even thicker and a placenta forms
What happens to the uterine if a preganancy does not occur?
No futher development of the uterine lining
