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Biology year 12 > reproduction > Flashcards

reproduction Flashcards

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1
Q

what are sperm cells

A

male gametes

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2
Q

sperm cell

A

formed in testes by meitosis to produce haploid nuclei
specailise in the testes
development under the infulence of the hormone testosterone

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3
Q

sperm cell features

A

flagellum-help sperm cell swim
haploid nucleus- only half the chromosomes (23)
mitochondria- provide energy to sperm

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4
Q

egg cell

A

to supply nutrients and energy to egg as it develops if fertilized

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5
Q

male reproductive system

A

testes- where sperm produced
penis-organ that transfers sperm to the woman
urethra- tube that carries urine or semen out of the body
scrotum- holds the testes in place
sperm duct- carries sperm from the testies to the penis
prostate gland- adds fluid to the sperm to nourish it

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6
Q

female reproductive system

A

ovary- where eggs develop
uterus-proper name for womb, where fertilized egg grows into a baby
vagina- erect penis inserted here during sex and where baby comes out at birth
cervix- a ring of muscle at the top of the vagina

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7
Q

what is fertilization

A

male nucleus fuses with female nucleus/fusion of haploid sperm nucleus and the female egg nucleus to produce a diploid zygote

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8
Q

fertilisation process

A

The sperm is deposited in the vagina, swims through the uterus and along

This occurs in the oviduct of the female the oviduct where it may fuse with an egg if one is present.

After fertilisation the zygote divides many times by MITOSIS to form a ball of cells as it travels down the oviduct to the uterus

IMPLANTATION ie this is when the ball of cells embeds in the lining of the uterus and starts to develop into a foetus (the woman is now pregnant).

After implantation in the uterus lining it then differentiates to produce a variety of tissues and organs.

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9
Q

implantation

A

After IMPLANTATION the ball of cells continues to divide further by mitosis and the cells formed start to differentiate (specialise) into different tissues and orgons.

Some of the cells develop into the PLACENTA. This is the organ of exchange between the mother’s blood and the baby’s blood Placenta exchange of dissolved nutrients, oxygen, carbon dioxide and urea

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10
Q

adaptions of the placenta for exchange

A

villi in placenta- prodives large surface area for diffusion of substances between the foetus and mother
thin wall of placenta- gives a short diffusion pathway
blood vessles in umbillical cord are close by- maintain a diffusion gradient

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11
Q

substances carried, direction of transport and reason for foetus

A

Oxygen and nutrients (e.g. glucose and amino acids)

Mother → Baby

There is a high concentration of oxygen. glucose and amino acids in the mothers blood so it diffuses across into the baby.

The baby uses oxygen and glucose for respiration and amino acids to make protein for growth

Waste materials (e.g. urea and carbon dioxide)

Baby → Mother

The baby releases carbon dioxide from respiration and it (along with urea) diffuses back into the mothers blood

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12
Q

umbillical cord

A

The UMBILICAL CORD contains the foetal blood vessels that carry these substances to and from the foetus.

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13
Q

amniotic sac

A

Pregnancy in humans lasts nine months - this is known as the GESTATION period

During this time the baby is enclosed in a membrane - the AMNION

Inside the AMNIOTIC SAC is a fluid called the AMNIOTIC FLUID

This cushions and protects the foetus during its development.ng its development.

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14
Q

male sex hormone

A

testosterone- produced in testes

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15
Q

female sex hormone

A

estrogen- produced in ovaries

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16
Q

what is puberty

A

period of development during which large physical and emotional changes take place in an individual

17
Q

oestrogen functions

A

Oestrogen has two main functions in the menstrual cycle

(a) The initial repair and build up of the uterus wall and (b) The stimulation of ovulation.

At the start of the menstrual cycle (Day one -when bleeding starts) the level of oestrogen is low.

As the cycle progresses the level of oestrogen rises.

  • It peaks in the middle of the cycle, causing the release of an egg (ovulation).
18
Q

progestrone functions

A

The level of progesterone is also low during menstruation and peaks in the days following ovulation. The role of progesterone is to build up and maintain the thick uterine lining (and the subsequent development of the placenta and other structures associated with pregnancy) should pregnancy occur.

Note:

If pregnancy does not occur, the levels of oestrogen and progesterone drop towards the end of the cycle and this causes menstruation to occur. The cycle then begins again.

19
Q

menstruation

A

starts during puberty in teenage girls and usually contiunes once a month until menopause when menstration stops.
generally considered as 28 day cycle

20
Q

period of cycle

A

Day 1-5

Menstruation - blood flows out of the vagina as the lining of the womb breaks up

Day 6-10

The lining of the womb starts to grow again - becomes thick with a rich blood supply

Day 10-17

During this time it is possible for fertilisation to occur if sperm is present in the oviduct as OVULATION occurs - egg is released from the ovary

Day 13-15

Day 18 - 28

If the egg is not fertilised it dies and eventually passes out of the vagina

The cycle then repeats itself

21
Q

causes of infertility

A

women:Failure of ovary to produce eggs (ova not released)

The oviducts may be blocked or twisted, possibly due to infection Damage to the oviducts as a result of a sexually transmitted infection
The lining of the uterus does not develop properly to enable implantation to occur ie does not allow implantation
Premature menopause
The vagina may be hostile to sperm entering, e.g. the lining may be too thick or acidic

In men:
Low sperm count.
Abnormal sperm eg poor motility
Hormone imbalances
Impotence

22
Q

treatments for infertility

A

fertility drugs
invitro fertilisation

23
Q

fertility drugs

A

These are given to the women to increase production of eggs. This may solve the problem if low egg production is the issue but if there are other problems such as blocked oviducts then in vitro fertilisation may be necessary.

24
Q

in vitro fertilisation

A

IVF was developed to allow infertile couples to conceive a child. Eggs and sperm are harvested from the parents and allowed to combine in a culture dish before the fertilised embryos are placed into the mother’s uterus.

25
Q

process of ivf fertilisation

A

The woman is given fertility hormones for a period of time before IVF - to stimulate the production of a large number or ova

to thicken the uterine lining in preparation for implantation

The ova produced are collected from the ovaries via the vagina

Sperm is donated and mixed with the eggs in a Petri dish and the nuclei allowed to fuse to fertilise the ova - in vitro

The fertilised ova are checked for healthy development by examination under a microscope

The selected fertilised ova will continue to develop for several days and are then implanted into the uterine lining.

More than one embryo (usually no more than 2-3) may be implanted -

To increase the chances of the pregnancy being successful, because

Some embryos die or do not divide or

Some embryos fail to implant successfully

26
Q

risks of ivf

A

However multiple embryo replacements carry the risk of multiple pregnancy and birth - an increased risk of premature labor - leading to a higher risk of birth defects such a blindness, and cerebral palsy

27
Q

contraception

A

prevention of conception by artifical or natural means

28
Q

mechanical means of contraception

A

male:condom
female:sheath

provides physical barrier

29
Q

chemical means of contraception

A

female: contraceptive pill
chemical implant

changes hormone levels

30
Q

surgical means of contraception

A

male:
vasectomony- sperm ducts cut
female:
oviducts cut

31
Q

advantages of mechanical means of contraception

A

mechanical means are reversible
do not require medical supervision
very reliable if used properly
protects against sti’s

32
Q

advanages of chemical means of contraception

A

reliable and reversible method

33
Q

disadvantages of of chemical means of contraception

A

side effects
requires medical supervision
doesnt protect against sti’s

34
Q

disadvantages of surgical means of contraception

A

it is irreversible

Biology year 12 (1 decks)

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