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IGCSE CAMBRIDGE BIOLOGY 2023. > Human Reproduction. > Flashcards

Human Reproduction. Flashcards

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1
Q

Describe sexual reproduction.

A

Sexual reproduction is a process involving the fusion of the nuclei of two gametes to form a zygote and the production of offspring that are genetically different from each other.

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2
Q

Describe fertilization.

A

Fertilization is the fusion of the nuclei from a male gamete (sperm) and a female gamete (egg cell).

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3
Q

The nuclei of gametes are _____ and the nucleus of a _______ are diploid.

A

The nuclei of gametes are haploid and the nucleus of a zygote are diploid.

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4
Q

What are the three functions of the male reproduction system?

A
  • Produces testosterone.
  • Manufactures the male gametes.
  • Delivers them to the site of fertilization.
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5
Q

What is the function of the following male reproductive part:
- Testes.

A
  • Made up of many coiled tubes which produce the male gametes (sperm).
  • The cells between the tubes produce testosterone.
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6
Q

What is the function of the following male reproductive part:
- Scrotum.

A
  • Sac of skin that encloses the testes and hang outside of the body between the legs where the testes are protected.
  • Temperature is 2 - 3°C lower than the body temperature - ideal for sperm development.
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7
Q

What is the function of the following male reproductive part:
- Sperm ducts.

A

Carries sperm from the testis to the urethra.

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8
Q

What is the function of the following male reproductive part:
- Prostate gland.

A

Produces fluid which makes up most of the sperm.

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9
Q

What is the function of the following male reproductive part:
- Urethra.

A
  • Carries semen from the sperm duct to the tip of the penis.
  • Carries urine, a valve prevents this happening at the same time.
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10
Q

What is the function of the following male reproductive part:
- Penis.

A

Erectile tissue can be stiffened by filling with blood. Once erect can be used to deliver sperm to the vagina of the female (ejaculation).

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11
Q

What are the four functions of the female reproductive system?

A
  • Produces oestrogen/progesterone.
  • Develops female gametes.
  • Accepts sperm.
  • Allows development/birth of the fetus.
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12
Q

What is the function of the following female reproductive part:
- Ovaries.

A

Contains thousands of follicles which develop the ova (eggs) and produce oestrogen and progesterone.

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13
Q

What is the function of the following female reproductive part:
- Oviducts (Fallopian tubes).

A

Carries the ovum to the uterus.
(Fertilization usually occurs in the first third of the oviduct).

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14
Q

What is the function of the following female reproductive part:
- Uterus.

A

Site of implantation and development of the fetus.

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15
Q

What is the function of the following female reproductive part:
- Cervix.

A

Ring of muscle at the lower end of the uterus.

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16
Q

What is the function of the following female reproductive part:
- Vagina/ birth canal.

A
  • Receives the penis during intercourse, sperm are deposited here.
  • Baby passes down the vagina during birth.
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17
Q

How are sperm cells and egg cells made?

A

Egg cells and sperm cells are made by meiosis.

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18
Q

What is the function of the following adaptive feature of sperm:
- Flagellum.

A

Flagellum is a tail used for swimming.

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19
Q

What is the function of the following adaptive feature of sperm:
- Middle piece containing mitochondria.

A

Middle piece containing mitochondria to release energy so the sperm can swim.

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20
Q

What is the function of the following adaptive feature of sperm:
- Enzymes in the acrosome.

A

The acrosome is a vesicle containing enzymes to dissolve through the jelly surrounding the egg cell.

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21
Q

What is the function of the following adaptive feature of egg cells:
- The food/ energy stored in the cytoplasm.

A

Cytoplasm contains a store of energy that provides energy for cell division after fertilization.

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22
Q

What is the function of the following adaptive feature of egg cells:
- Jelly coat.

A

Jelly coat changes after fertilization to form an impenetrable barrier to prevent other sperm nuclei entering the egg cell.

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23
Q

Compare male and female gametes in terms of:
- Size.

A
  • Sperm cell = Small, very little food store.
  • Egg cell = Much larger than sperm cell as it contains a food store in the cytoplasm
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24
Q

Compare male and female gametes in terms of:
- Movement/ mobility.

A
  • Sperm cell = Contains a lot of mitochondria to release energy so the sperm can swim using tail movement.
  • Egg cell = Does not move itself (is moved along the oviduct by cilia and peristalsis.
25
Q

Compare male and female gametes in terms of:
- Structure/ Adaptive features.

A
  • Sperm cell = Flagellum, Mitochondria, and enzymes in the acrosome.
  • Egg cell = Energy stores in the cytoplasm, jelly coat that changes at fertilization so only one sperm cell enters and fertilizes.
26
Q

What number of chromosomes do sperm cells and eggs cells have?

A

23 which is the haploid number.

27
Q

Compare male and female gametes in terms of:
- Number produced.

A
  • Sperm cell = (100 000 000) many per day from puberty to old age.
  • Egg cell = One a month from alternate ovaries from puberty to middle age (menopause), except when pregnant or taking the contraceptive pill.
28
Q

Describe what happens during sexual intercourse.

A

During sexual intercourse, the penis becomes erect and enters the vagina. Sperm are released from the testes and travel by peristalsis along the sperm ducts. Contractions of the urethra move the seminal fluid through the penis into the vagina.

29
Q

What happens in early development?

A

The zygote forms an embryo which is a ball of cells that implants into the lining of the uterus.

30
Q

What happens at fertilization?

A
  • Enzymes released by the acrosome break down the jelly coat so that the nucleus of the sperm can fertilize the nucleus of the egg cell.
  • The ovum membrane alters to form a barrier to the entry of other sperm.
  • The new cell contains a set of genetic material from the mother and a set from the father. It is a diploid zygote with 46 chromosomes.
  • The fertilized ovum or zygote now starts to divide by mitosis and continues to move down the oviduct by peristalsis of the oviduct muscles and the beating of cilia to the uterus where it implants in the thickened uterus lining.
  • Once the embryo is attached to the lining of the uterus, some of its outer cells combine with some of the mother’s cells and a placenta begins to develop.
31
Q

What are the 6 functions of the placenta?

A
  • exchange of dissolved nutrients e.g. glucose, amino acids, and excretory products e.g. urea.
  • Exchange of dissolved gases by diffusion e.g.oxygen and carbon dioxide.
  • Antibodies diffuse from the mother to the baby to provide passive immunity.
  • Protection of the fetus from the mother’s immune system.
    - there is no direct contact between maternal and
    fetal blood. The mother’s blood flows under high
    pressure and would damage the delicate blood
    vessels of the fetus also if the mother and fetus
    have different blood groups then the mother’s
    antibodies and platelets may cause it to clot.
  • It provides a barrier to toxins and pathogens however some toxins e.g. nicotine, alcohol, heroin, and pathogens can diffuse across the placenta and affect the fetus.
  • Secretion of hormones (progesterone) which maintains the lining of the uterus during pregnancy as the corpus luteum breaks down.
32
Q

What is the umbilical cord?

A

The umbilical cord connects the fetus to the placenta.

33
Q

What is the function of the umbilical cord?

A

The cord contains the umbilical artery which carries deoxygenated blood and wastes (e.g. carbon dioxide and urea) from the fetus to the placenta and the umbilical vein which carries oxygenated blood and nutrients(e.g. glucose and amino acids) from the placenta to the fetus.

34
Q

What does the amniotic fluid protect the fetus against?

A
  • mechanical shock.
  • drying out.
  • temperature fluctuations.
35
Q

What is the fetus surrounded by throughout pregnancy?

A

Throughout pregnancy the fetus is surrounded by a membrane called the amniotic sac which contains amniotic fluid.

36
Q

What are the 6 secondary sexual characteristics in males?

A
  • Facial hair develops.
  • Chest broadens.
  • Voice deepens.
  • Hair develops on chest, under armpits and in pubic region.
  • Penis and testes become larger.
  • Sperm production begins.
37
Q

What are the 5 secondary sexual characteristics in females?

A
  • Breasts develop.
  • Hips broaden.
  • Hair grows under armpits and in the pubic region.
  • Vagina enlarges.
  • Oestrogen begins the cycle of egg production and prepares the uterus lining for implantation.
38
Q

Fill in the missing spaces:
At puberty, a person becomes _________ able to ____________. At puberty the ______ instructs the _____________ __________ to make ______________ (Follicle Stimilauting Horomore and Luteinizing Hormone) that stimulate the ____________ ____ ________ to release the ___ hormones into the ______ _________. The testes release __________ and the _________ release oestrogen. These hormones only affect the ____________ _____ which have ______ to recognise them.

A

At puberty, a person becomes physically able to reproduce. At puberty the brain instructs the pituitary gland to make hormones (Follicle Stimilauting Horomore and Luteinizing Hormone) that stimulate the primary sex organs to release the sex hormones into the blood stream. The testes release testosterone and the ovaries release oestrogen. These hormones only affect the target organs which have receptors to recognise them.

39
Q

The menstrual cycle is a long term process controlled by a number of hormones, which:

A
  • Prepare the uterus to receive any fertilised ova.
  • Control the development of mature ova.
40
Q

What is the menstrual cycle?

A

The cycle of producing and releasing mature ova is called the menstrual cycle.

41
Q

Fill in the missing spaces:

Girls are born with ____________ of potential _____ ______ in their ______. Each potential egg is surrounded by a ____ _____ ___ ______ and together they form _ _________ (____________ _________ __________). Ovaries ___ _____ produce any more _____ in their lifetime. At puberty (between 10 and 15 years) some of the ______ start to _______ and girls start to have _______.

A

Girls are born with thousands of potential egg cells in their ovaries. Each potential egg is surrounded by a small group of cells and together they form a follicle (Follicle Stimulating Hormone). Ovaries do not produces any more eggs in their life time. At puberty (between 10 and 15 years) some of the follicles start to develop and girls start to have periods.

42
Q

What is a sexually transmitted infection?

A

Sexually transmitted infection is an infection that is transmitted through sexual contact.

43
Q

What is human immunodeficiency virus (HIV)?

A

Human immunodeficiency virus (HIV) is a pathogen that causes AIDS (and STI).

44
Q

Name ways in which a sexually transmitted infection may be transmitted.

A
  • in blood through transfusions, hypodermic needles, and mixing of blood.
  • in semen during unprotected sexual intercourse with an infected person.
  • across the placenta during pregnancy.
  • during birth when the mother and baby’s blood streams come in close contact.
  • during breast feeding through breast milk.
45
Q

Name ways in which a sexually transmitted infection may be transmitted.

A
  • in blood through transfusions, hypodermic needles, and mixing of blood.
  • in semen during unprotected sexual intercourse with an infected person.
  • across the placenta during pregnancy.
  • during birth when the mother and baby’s blood streams come in close contact.
  • during breast feeding through breast milk.
46
Q

How can one prevent catching a sexually transmitted infection?

A

By using condoms, drug users must not share needles, screen blood for transfusions.

47
Q

How can one treat a sexually transmitted infection?

A

Anti-retroviral drugs can be given along with counseling. There is NO cure.

48
Q

What are the signs/ symptoms for HIV?

A

There are none for HIV. After 8 - 10 years it will develop into Acquired immunodeficiency syndrome (AIDS).

49
Q

What is AIDS?

A

AIDS is a collection of diseases which result from the weakening of the immune system.

50
Q

What are the symptoms of AIDS?

A

Symptoms include flu symptoms, swollen glands, high temperature.

51
Q

What is the result of AIDS?

A

Aids cannot be cured as it is from the Human immunodeficiency virus, so death will result.

52
Q

What are the four functions of oestrogen (released by follicle)?

A
  • Repairs uterus lining.
  • Inhibits Follicle Stimulating Hormone.
  • Stimulates Luteinising Hormone release.
  • Stimulates development of female sexual characteristic.
53
Q

What are the two functions of luteinizing hormone (released by the pituitary gland)?

A
  • Stimulates release of mature ovum.
  • Development of the corpus luteum.
54
Q

What are the three functions of progesterone (released by corpus luteum)?

A
  • Thickens uterus lining.
  • Inhibits Follicle Stimulating Hormone.
  • Prevents Menstruation.
  • Prevents production of more eggs.
55
Q

What days do menstruation, repair phase, ovulation, receptive phase, and premenstrual phase take place?

A
  • Menstruation = Day 0 - Day 5.
  • Repair Phase = Day 6 - Day 12.
  • Ovulation = Day 13 - Day 15.
  • Receptive Phase = Day 16 - Day 21.
  • Premenstrual Phase = Day 22 - Day 28.
56
Q

What does FSH do (released by the pituitary gland)?

A

Stimulate follicle growth to secrete oestrogen and develop the ovum.

57
Q

What happens if fertilization happens in regard to progesterone levels?

A

If fertilization does take place progesterone levels remain high and the uterus lining is maintained.

58
Q

What happens if fertilization does not happen in regard to progesterone levels?

A

If fertilization does not take place the progesterone levels decrease and menstruation takes place.

IGCSE CAMBRIDGE BIOLOGY 2023. (32 decks)

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