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Biology IGCSE CIE Extended > Sexual Reproductions in Humans > Flashcards

Sexual Reproductions in Humans Flashcards

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1
Q

Prostate Gland definition

A

produces fluid called semen that provides sperm cells with nutrients

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2
Q

Sperm Duct definition

A

Sperm passes through the sperm duct to be mixed with fluids produced by the glands before being passed into the urethra for ejaculation. Muscular tube that connects testis to urethra.

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3
Q

Urethra definition

A

Tube running down the centre of the penis that can carry out urine or semen. A ring of muscle in the urethra prevents the urine and semen from mixing

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4
Q

Testis definition

A

Contained in a bag of skin (scrotum) and produces sperm (male gamete) and testosterone

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5
Q

Scrotum definition

A

Sac supporting the testes outside the body to ensure sperm are kept at temperature slightly lower than body temperature

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6
Q

Penis definition

A

Passes urine out of the body from the bladder and allows semen to pass into the vagina of a woman during sexual intercourse

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7
Q

Oviduct definition

A

Connects the ovary to the uterus and is lined with ciliated cells to push the released ovum down it. Fertilisation occurs here

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8
Q

Ovary definition

A

Contains follicles in which ova (female gametes) are produced which will mature and develop when hormones are released

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9
Q

Uterus definition

A

Muscular bad with a soft lining where the fertilised egg (zygote) will be implanted to develop into a foetus

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10
Q

Vagina definition

A

Muscular tube that leads to the inside of the woman’s body, where the male’s penis will enter during sexual intercourse and sperm are deposited

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11
Q

Fertilisation definition

A

The fusion of the nuclei from a male gamete (sperm cell) and a female gamete (egg cell)

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12
Q

Why do gametes have adaptations?

A

They have adaptations to increase the chances of fertilisation and successful development of an embryo

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13
Q

What 3 adaptations does a sperm have?

A
  • has a flagellum (tail)
  • contains enzymes in the head region (acrosome)
  • contains many mitochondria
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14
Q

How does a sperm having a tail help it in its function?

A

Enables it to swim to the egg

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15
Q

How does a sperm having enzymes in the head region help it in its function?

A

To digest through the jelly coat and cell membrane of an egg cell when it meets one

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16
Q

How does a sperm containing many mitochondria help it in its function?

A

Provide energy from respiration so that the flagellum can move back and forth for locomotion

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17
Q

What 2 adaptations does an egg cell have?

A
  • cytoplasm containing store of energy

- jelly like coating that changes after fertilisation

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18
Q

How does an egg cell having cytoplasm containing a store of energy help it in its function?

A

provides energy for the dividing zygote after fertilisation

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19
Q

How does an egg cell having a jelly like coating help it in its function?

A

forms an impenetrable barrier after fertilisation to prevent other sperm nuclei entering the egg cell

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20
Q

Comparison of male and female gametes in terms of size

A

SPERM: very small (45nm)
EGG: large (0.2mm)

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21
Q

Comparison of male and female gametes in terms of structure

A

SPERM: Head region and flagellum, many structural adaptations
EGG: Round cell with few structural adaptations, covered in a jelly coating

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22
Q

Comparison of male and female gametes in terms of mobility

A

SPERM: Capable of locomotion
EGG: not capable of locomotion

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23
Q

Comparison of male and female gametes in terms of numbers

A

SPERM: produced every day in huge numbers (around 100 million per day)
EGG: thousands of immature eggs in each ovary, but only released each month

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24
Q

What is a zygote?

A

A fertilised egg cell (when nuclei of sperm and egg combine)

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25
Q

Where does the zygote travel after fertilisation?

How long does this take?

A

Towards the uterus

3 days

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26
Q

How does a zygote turn into an embryo?

A

It divides several times to form a ball of cells known as an embryo

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27
Q

What is implantation?

A

When the embryo embeds itself in the thick lining of the uterus and continues to grow and develop

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28
Q

How long is the gestation period for humans?

A

9 months

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29
Q

What happens in the first 12 weeks? (development of a baby)

A

the major development of organs

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30
Q

How does the embryo get its nutrients

A

the embryo gets nutrients from the mother by diffusion through the uterus lining

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31
Q

3 things which are completed by 12 weeks (development of a baby)

A

After this point the organs are all in place, the placenta has formed and the embryo is now called a fetus

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32
Q

After 12 weeks, what happens during the rest of the gestation period?

A

The remaining gestation time is used by the fetus to grow bigger in size

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33
Q

What is the fetus surrounded by and what does this contain?

A

The fetus is surrounded by an amniotic sac which contains amniotic fluid

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34
Q

What is the amniotic fluid made from?

A

the mother’s blood plasma

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35
Q

What is the role of the umbilical cord?

A

The umbilical cord joins the fetus’s blood supply to the placenta for exchange of nutrients and removal of waste products

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36
Q

What nutrients does the fetus need while developing?

Where do these nutrients come from?

A

glucose, amino acids, fats, water and oxygen

from the mother’s blood

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37
Q

Does the blood supply of the fetus and mother mix?

A

NO

The bloods run opposite each other, never mixing

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38
Q

Where does the blood supply of the mother and fetus “meet”?

A

in the placenta

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39
Q

How is the fetus connected to the placenta?

A

By the umbilical cord

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40
Q

Apart from nutrients, what does the mother’s blood supply contain?

A

The mother’s blood also absorbs the waste products from the fetus’s blood in the placenta

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41
Q

What sort of waste products may the fetus produce?

A

carbon dioxide and urea

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42
Q

Why do waste products need to be removed from the fetus’ bloodstream?

A

so that they do not build up to dangerous levels

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43
Q

By what process do these nutrients/waste products move from fetus to mother?
Why?

A

Movement of all molecules across the placenta occurs by diffusion due to difference in concentration gradients

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44
Q

How is the placenta adapted for efficient diffusion?

A

The placenta is adapted for this diffusion by having a large surface area and a thin wall for efficient diffusion

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45
Q

What does the placenta act us?

A

The placenta acts as a barrier to prevent toxins and pathogens getting into the fetus’s blood

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46
Q

What sorts of things might the placenta not be able to prevent from passing through it?
What does it depend on?

A

Not all toxin molecules or pathogenic organisms (such as viruses, eg rubella) are stopped from passing through the placenta (this usually depends on the size of the molecule)

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47
Q

What are pregnant women advised not to do during pregnancy?

A

Smoke, drink alcohol, do drugs

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48
Q

What happens immediately after the baby is born?

A

The umbilical cord is cut and tied off to prevent bleeding. Shrives up and falls off after a few days leaving the belly button.

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49
Q

What happens to the placenta after the baby has been born?

A

The placenta detaches from the uterus wall shortly after birth and is pushed out due to contractions in the muscular wall of the uterus – known as the afterbirth

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50
Q

What are the six (simple) stages of birth?

A 
Amniotic sac breaks
Muscles in the uterus wall contract
Cervix dilates (gets wider)
Baby passes out through the vagina
Umbilical cord is tied and cut
Afterbirth is delivered
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51
Q

What is antenatal care?

A

Antenatal (before birth), care is the name given to the care and advice given to expectant mothers along with checks on fetal growth and development

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52
Q

What 3 pieces of advice are expectant mothers given?

A
  • having a balanced diet
  • exercise to stay fit
  • health precautions such as avoiding infections, tobacco, alcohol and other drugs
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53
Q

What does a woman need to take to have a fully healthy diet while pregnant? Why?

A

need to take folic acid to prevent developmental issues with the fetus

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54
Q

What happens to the mammary glands during pregnancy?

A

Enlarge and become prepared to secrete milk

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55
Q

What causes the mother to be stimulated to release milk shortly after birth?

A

sucking action of the baby at the breast

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56
Q

What are the advantages of breastfeeding? (4)

A
  • contains exactly the right nutrients in the right amounts the baby needs at different stages
  • contains antibodies which help the baby prevent infection
  • helps develop a bond between mother and baby
  • is free
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57
Q

What are the disadvantages of breastfeeding? (2)

A
  • if it does not come easily to the mother it can contribute to postnatal depression
  • responsibility for feeding the baby is solely with the mother
58
Q

What are the advantages of bottle feeding? (2)

A
  • allows the father to bond with the baby

- allows the mother more freedom as she is not solely responsible for feeding the baby

59
Q

What are the disadvantages of bottle feeding? (2)

A
  • risk of infections increased if bottles and equipment are not properly sterilised
  • is expensive
60
Q

What is the function of the amniotic sac?

A

A fluid-filled sac that protects the embryo from damage and unequal pressures from acting upon it.

61
Q

Why are birth control methods important?

A

Birth control methods are important in keeping family sizes small and in limiting the increase in the human population

62
Q

What 4 categories of contraception methods are there?

A

Humans can use mechanical, chemical, surgical and natural contraceptive methods to prevent a pregnancy

63
Q

What can some types of birth control methods protect the user from?

A

Some birth control methods also give protection from sexually transmitted infections

64
Q

What is abstinence?

A

avoiding sexual intercourse completely

65
Q

What is the rhythm method?

A

avoiding sexual intercourse during the fertile period of the menstrual cycle when ovulation occurs

66
Q

Using the rhythm method how can a woman work out the exact time of ovulation?

A

the exact time ovulation happens can be worked out by monitoring body temperature and quality of cervical mucus

67
Q

Is the rhythm method reliable?

A

No, it’s the least reliable method

68
Q

What are the two chemical types of birth control?

A

IUD/IUS

Contraceptive pill, implant, injection

69
Q

What does IUD / IUS stand for?

A

an intrauterine device or intrauterine system

70
Q

what is an IUD and who fits it?

A

a small device fitted inside the uterus by a doctor or nurse

71
Q

How does an IUD work?

chemical aspects

A
  • it releases sex hormones which thicken the mucus produced in the cervix, making it difficult for sperm to swim into the uterus
  • it also thins the lining of the uterus, making it more difficult for a fertilised egg to implant
72
Q

How does an IUD work?

physical aspects

A

an IUD also interferes with the passage of sperm through the uterus, in which way it is acting as a barrier method of birth control

73
Q

What may a contraceptive pill, implant or injection contain?

A

may contain just progesterone or a mixture of progesterone and oestrogen

74
Q

Is the contraceptive pill, implant, injection method effective?

A

Yes, very when taken regularly

75
Q

In what ways is a contraceptive implant or injection better than the pills?

A
  • both last several months

- increase the effectiveness as they remove the risk of forgetting to take a pill regularly

76
Q

What are the 3 types of barrier methods of birth control?

A

Condom
Femidom
Diaphragm

77
Q

How do barrier contraceptive methods work?

A

All work by preventing sperm from reaching the egg

78
Q

What is a condom?

A

latex sheath worn over the penis

79
Q

How does a condom work?

A

prevents sperm entering the vagina as ejaculate remains in condom

80
Q

What does a condom also protect from (apart from preventing pregnancy)?

A

Protects against STI’s

81
Q

What is a femidom?

A

latex sheath inserted into the vagina

82
Q

How does a femidom work?

A

prevents entry of sperm into the vagina

83
Q

What is a diaphragm?

A

a rubber cap that fits over the entrance to the cervix

84
Q

How does a diaphragm work?

A

prevents entry of sperm into the uterus

85
Q

What is often used alongside a diaphragm?

A

often used with a spermicide (cream which kills sperm)

86
Q

What are the 2 types of surgical methods of birth control?

A
  • vasectomy

- female sterilisation (tubal ligation)

87
Q

How does a vasectomy work?

A

the sperm ducts are cut, meaning that no sperm is present in the semen when ejaculation occurs

88
Q

How does female sterilisation work?

A

the oviducts are cut or tied off, preventing eggs from reaching the uterus or sperm from reaching the eggs

89
Q

Are surgical methods of birth control effective? What’s the downside?

A

very effective but difficult to reverse

90
Q

How do Contraceptive Hormones in the Pill Work?

A

They work by mimicking some of the hormone levels during pregnancy
By raising the levels of progesterone and oestrogen, the uterus lining is maintained and development of another egg cell is prevented
This means that sex at any time of the month cannot cause pregnancy as no egg is released to be fertilised

91
Q

When and why are fertility treatments used?

A

In situations where couples find it difficult to conceive, fertility treatments can improve their chances

92
Q

What 3 types of fertility treatments are there?

A
  • Artificial Insemination
  • Fertility Drugs
  • In Vitro Fertilisation (IVF)
93
Q

When is Artificial Insemination used?

A

If the male is not producing healthy sperm

94
Q

What is the process of artificial insemination ?

A
  • donor sperm is used

- The sperm are placed into the female’s vagina at the fertile point in her menstrual cycle

95
Q

What social issues can be considered with artificial insemination?

A
  • The male must be able to cope with the fact that the child is not biologically his
  • Sperm donors may father multiple children who are not able to know their parentage
96
Q

When are fertility drugs used?

A

This method is used when the female is not producing enough eggs

97
Q

What types of hormones are in fertility drugs and what do they do?

A

Hormones, including FSH, are given to her to stimulate egg production

98
Q

What social issues can be considered with fertility drugs?

A

Several eggs can be released at once so this increases the chance of multiple births (twins or triplets etc)

99
Q

When is IVF used?

A

If the female cannot conceive naturally even after taking fertility drugs, or if there are issues with both male and female fertility in a couple, IVF can be used

100
Q

What are the 4 stages of IVF?

A
  1. This involves fertility drugs being given to the female to stimulate egg production before they are harvested from the ovary
  2. The eggs are then inseminated in a petri dish using sperm from the male
  3. Once embryos have formed, they are placed back into the uterus of the female
  4. Several embryos are implanted to increase the chance of one developing further
101
Q

What social issues can be considered with IVF?

A
  1. IVF is relatively expensive and not all couples can afford it
  2. As several embryos are implanted, the risk of multiple births is quite high
  3. Some women use IVF to get pregnant at a later age than they would be able to conceive naturally
102
Q

How are STI’s passed on?

A

Unprotected sexual intercourse can lead to the transfer of pathogens via exchange of body fluids

103
Q

What is an example of an STI that can develop into something else?

A

HIV (Human Immunodeficiency Virus), the virus that usually leads to the development of acquired immunodeficiency disease (AIDS)

104
Q

How can HIV be spread (apart from sexually)? (4)

A

HIV can also be spread via:

  • sharing needles with an infected person,
  • blood transfusions with infected blood
  • from mother to fetus through the placenta
  • mother to baby via breastfeeding
105
Q

What symptoms do people usually get immediately after infection? (HIV)

A

people often suffer mild flu-like symptoms

106
Q

Do people who first get HIV know they’re infected? Why?

A

These symptoms pass and for a period of time infected people might not know they are infected

107
Q

What specific thing does HIV infect?

A

The virus infects a certain type of lymphocyte of the body’s immune system

108
Q

What do lymphocytes usually do?

A

Normally lymphocytes seek out and destroy pathogens that enter the body, producing antibodies that attach to pathogens, enhancing phagocytic activity

109
Q

How does HIV avoid detection by lymphocytes?

A

HIV avoids being recognised and destroyed by lymphocytes by repeatedly changing its protein coat

110
Q

How does HIV manage to survive in the body?

A

It then infects a certain type of lymphocyte and uses the cells’ machinery to multiply

111
Q

What does HIV do to the body’s immune system?

A

This reduces the number of lymphocytes of the immune system, and also the number of antibodies that can be made

112
Q

How does HIV lead to AIDS?

A

It decreases the body’s ability to fight off infections, eventually leading to AIDS (Acquired immunodeficiency)

113
Q

What does HIV attach to?

A

HIV attaches to receptors on lymphocyte

114
Q

How does HIV enter the lymphocyte?

A

HIV injects its genetic material into the lymphocyte, which becomes a HOST CELL

115
Q

What happens to the lymphocyte after HIV is done with it?

A

After making many copies of itself, the host cell is destroyed by HIV

116
Q

In what 4 ways can the spread of STI’s be controlled?

A
  • Limiting the number of sexual partners an individual has
  • Not having unprotected sex, but making sure to always use a condom
  • Getting tested if unprotected sex or sex with multiple partners has occurred
  • Raising awareness by education programmes
117
Q

When are primary sexual characteristics developed and what are they?

A

Primary sexual characteristics are present during development in the uterus and are the differences in reproductive organs etc between males and females

118
Q

What are secondary sexual characteristics?

A

Secondary sexual characteristics are the changes that occur during puberty as children become adolescents

119
Q

What are the secondary sexual characteristics controlled by?

A

They are controlled by the release of hormones – oestrogen in girls and testosterone in boys

120
Q

What are examples of secondary sexual characteristics in females? (4)

A
  • breasts develop
  • body hair grows
  • menstrual cycle begins
  • hips get wider
121
Q

What are examples of secondary sexual characteristics in males? (5)

A
  • growth of penis and testes
  • growth of facial and body hair
  • muscles develop
  • voice breaks
  • testes start to produce sperm
122
Q

What changes occur to both boys and girls?

A

growth of sexual organs and growth of body hair

123
Q

What other changes, apart from physical, can happen during puberty? Why? What are examples?

A

Emotional changes also occur due to the increased levels of hormones in the body
These include more interest in sex and increased mood swings

124
Q

When does the menstrual cycle start and what is it controlled by?

A

Starts in early adolescence in girls (around age 12) and is controlled by hormones

125
Q

How long is the average menstrual cycle?

A

The average menstrual cycle is 28 days long

126
Q

When does ovulation occur? What happens?

A

Ovulation (the release of an egg) occurs about halfway through the cycle (day 14) and the egg then travels down the oviduct to the uterus

127
Q

What causes menstruation?

A

Failure to fertilise the egg causes menstruation (commonly called a period) to occur – this is caused by the breakdown of the thickened lining of the uterus

128
Q

How long does menstruation last?

A

Menstruation lasts around 5 – 7 days and signals the beginning of the next cycle

129
Q

What happens after the menstruation cycle finishes?

A

After menstruation finishes, the lining of the uterus starts to thicken again in preparation for possible implantation in the next cycle

130
Q

What is the menstrual cycle controlled by and where do these things come from?

A

The menstrual cycle is controlled by hormones released from the ovary and the pituitary gland in the brain

131
Q

When do oestrogen levels rise?

A

Oestrogen levels rise from day 1 to peak just before day 14

132
Q

What changes does oestrogen cause?

A
  • stimulates the uterus to develop a lining (to replace lining lost during menstruation)
  • post-ovulation, inhibits FSH and LH production in the pituitary gland
  • causes the egg to mature
133
Q

When is the peak in oestrogen levels?

A

The peak in oestrogen occurs just before the egg is released

134
Q

When doe progesterone levels rise?

A

Progesterone stays low from day 1 – 14 and starts to rise once ovulation has occurred

135
Q

What changes does progesterone cause?

  1. increase
  2. decrease
A
  1. The increasing levels cause the uterine lining to thicken further
  2. a fall in progesterone levels causes the uterine lining to break down (menstruation / ‘period’)
    - maintains lining of uterus
    - inhibits FSH and LH production
136
Q

What secretes FSH and LH?

A

the pituitary gland

137
Q

What changes does FSH cause?

A
  • stimulates egg maturation in the follicles of the ovary

- stimulates follicles in the ovaries to secrete oestrogen

138
Q

When is LH secreted?

A

The pituitary gland is stimulated to release luteinising hormone (LH) when oestrogen levels have reached their peak

139
Q

What changes does LH cause?

A
  • stimulates ovulation (release of egg into oviduct)

- stimulates ovary to produce progesterone (ovulation results in the formation of a corpus luteum which secretes p)

140
Q

What happens if the egg is fertilised and pregnancy does occur? (menstrual cycle)

A

If pregnancy does occur the corpus luteum continues to produce progesterone, preventing the uterus lining from breaking down and aborting the pregnancy

141
Q

During pregnancy, at what point does the corpus luteum stop producing progesterone?

A

It does this until the placenta has developed, at which point it starts secreting progesterone and continues to do so throughout the pregnancy

Biology IGCSE CIE Extended (22 decks)

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