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Year 12 - Biology > C18 - Fertility and Assisted Reproduction (Yr 2) > Flashcards

C18 - Fertility and Assisted Reproduction (Yr 2) Flashcards

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1
Q

What is the function of the cervix?

A

It provides a narrow opening into the uterus, protecting the fetus during pregnancy.

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2
Q

What is the function of the ovary?

A

It produces the female gametes (oocytes/eggs/ova) in follicles.

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3
Q

What is the function of the oviduct?

A

A.k.a. the fallopian tube, it is where the egg gets fertilised by sperm.

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4
Q

What is the function of the uterus?

A

This is where the embryo develops.

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5
Q

What is the function of the vagina?

A

It stimulates the penis to ejaculate and provides a birth canal.

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6
Q

What is the function of the vulva?

A

It protects the internal parts of the female reproductive system.

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7
Q

What is the function of the epididymis?

A

It stores sperm prior to ejaculation.

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8
Q

What is the function of the penis?

A

It penetrates the vagina and releases sperm.

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9
Q

What is the function of the prostate gland?

A

It secretes an alkaline fluid to counteract the acidity of the vagina.

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10
Q

What is the function of the scrotum?

A

It holds the testes, maintaining a temperature 2°C below normal body temperature.

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11
Q

What is the function pf the seminal vesicle?

A

It secretes a fluid containing proteins and fructose to nourish the sperm.

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12
Q

What is the function of the sperm duct?

A

It transfers sperm during ejaculation.

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13
Q

What is the function of the testis?

A

It produces sperm and testosterone.

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14
Q

What is the function of the urethra (males)?

A

It transfers semen during ejaculation and urine urine during urination.

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15
Q

What are seminiferous tubules?

A

Seminiferous tubules are located within the testes, and are the specific location of meiosis, and the subsequent creation of male gametes (spermatozoa).

The epithelium of the tubule consists of a type of sustentacular cells known as Sertoli cells, which are tall, columnar type cells that line the tubule.

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16
Q

What are Sertoli cells?

A

Tall, columnar cells which line the seminiferous tubules within the testes.

They’re essential for testis formation and spermatogenesis.

Sertoli cells facilitate the progression of germ cells to spermatozoa via direct contact and by controlling the environment within the seminiferous tubules.

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17
Q

What is gametogenesis?

A

The production of gametes, involving meiotic cell divisions.

This can occur as Oogenesis (occurring in females) or Spermatogensis (occurring in males)

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18
Q

What occurs during Oogenesis?

A

1 - Primordial germ cells (2n) will divide by mitosis to produce many oogonia (before birth)

2 - Each oogonia grows within the follicle of cells to form primary oocytes.

3 - The primary oocyte starts to undergo meiosis I but pauses at prophase i (before puberty)

4 - During puberty primary oocytes undergo the first meiotic division to form haploid secondary oocytes.

5 - The secondary oocyte begins the secondary meiotic division but pauses in metaphase II unless fertilisation takes place.

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19
Q

What occurs during spermatogenesis?

A

1 - A primordial germ cell divides by mitosis to produce spermatogonia.

2 - The spermatogonia then grow to form primary spermatocytes.

3 - The primary spermatocytes separate the homologous pairs of chromosomes in meiosis I (reduction division) to form the haploid secondary spermatocytes.

4 - The haploid spermatids are formed from the separation of the sister chromatids in meiosis II.

5 - The spermatids are found in association with the Sertoli cells (found in the testis) which nourish the spermatids as they differentiate into spermatozoa.

6 - The rate of formation of spermatozoa is high and continuous throughout the life of a sexually active mature male.

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20
Q

What are the similarities between spermatogenesis and oogenesis?

A

They have a multiplication, growth and maturation phase.

They have mitosis followed by meiosis.

They produce haploid gamete.

They begin with primordial germ cells.

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21
Q

What are the differences between spermatogenesis and oogenesis?

A

The are no polar bodies in males (polar bodies in females).

Spermatids undergo differentiation to form spermatozoa.

Spermatogenesis is continuous whereas oogenesis stops in later life (menopause).

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22
Q

What is the structure of an oocyte?

A

They consist of a cytoplasm a.k.a yolk due to fat droplets in the cytoplasm.

The haploid nuclei (arrested at metaphase II) sits within the yolk.
During follicle development , unequal division of the cell during meiosis produces the first polar body which can be seen outside the plasma membrane and won’t develop.

The sons pellucida surrounds the structure and consists of glycoproteins.
Cortical granules are present and will be involved in the acrosome reaction at fertilisation.
Ovarian follicle cells (corona radiata) surround the structure.

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23
Q

What is a polar body?

A

The small cells which bud off from an oocyte at the two meiotic divisions and do not develop into ova.

During follicle development , unequal division of the cell during meiosis produces the first polar body which can be seen outside the plasma membrane and won’t develop.

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24
Q

What does a secondary oocyte consist of?

A

A haploid nucleus at the centre, as well as two centrioles, surrounded by a cytoplasm / yolk containing fat droplets.

Within the yolk are cortical granules.

This is surrounded by the plasma membrane. The polar body would be situated in the plasma membrane.

Then there is the layer of gel composed of glycoproteins called the zona pellucida.

The outer layer consists of a layer of follicle cells called the corona radiata.

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25
Q

What is the zona pellucida?

A

The layer of gel composed of glycoproteins between the plasma membrane and corona radiata in an oocyte.

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26
Q

What is the corona radiata?

A

The outer layer of the oocyte consisting of follicle cells.

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27
Q

What is the structure of a mature sperm?

A

It has an acrosome - a thin cap over the nucleus containing enzymes required to digest its way through the zona pellucida (haploid nuclei).

It’s mid section contains many mitochondria which synthesise ATP to provide the energy for the movement of the tail.

Protein fibres provide longitudinal rigidity.

Contractile fibres made up of microtubules in a 9 + 2 arrangement create a whipping movement so that the sperm can swim.

28
Q

What is the acrosome?

A

The thin cap over the nucleus of sperm cells which contains enzymes required to digest its way through the zona pellucida of an oocyte.

29
Q

What does GnRH stand for?

A

Gonadotrophin-releasing hormone.

The hypothalamus produces gonadotrophin-releasing hormone which causes the anterior pituitary gland to produce FSH and LH.

30
Q

Where is GnRH produced and what does it do?

A

The hypothalamus produces gonadotrophin-releasing hormone which causes the anterior pituitary gland to produce FSH and LH.

31
Q

What does L.H. Do in males during gametogenesis?

A

Leuteinising hormone binds to Leydig cells in the testes which triggers the release of testosterone, contributing to spermatogenesis.

However the testosterone can send negative feedback to the pituitary gland to prevent the release of L.H. as well as send negative feedback to the hypothalamus to prevent GnRH from being produced.

32
Q

How can L.H. and GnRH be prevented from being produced within males.

A

Testosterone (released from Leydig cells in the testes) can send negative feedback to the pituitary gland to prevent the release of L.H. as well as send negative feedback to the hypothalamus to prevent GnRH from being produced.

33
Q

What does FSH do in males during gametogenesis?

A

It binds to Sertoli cells within the testes and make them more receptive to testosterone and encourage spermatogenesis.

34
Q

How can Sertoli cells influence the amount of FSH produced?

A

Sertoli cells can release inhibin which sends negative feedback to the pituitary to reduce the amount of FSH produced.

35
Q

What does L.H. do in females during gametogenesis?

A

It binds to follicle cells in the ovaries, causing them to mature and release oestrogen.
A surge of L.H. causes a secondary oocyte to be released from the mature Graafian follicle.

36
Q

What does FSH do in females during gametogenesis?

A

It binds to follicle cells in the ovaries, causing them to at you’re and release oestrogen.

37
Q

What does progesterone do in females during gametogenesis?

A

It inhibits LH and FSH.

38
Q

What does oestrogen do in females during gametogenesis?

A

Rising levels inhibits FSH and causes a surge in LH.

39
Q

What is the ovarian and uterine cycle?

A

The ovarian cycle controls the release of secondary oocytes.

The uterine cycle controls the development of the uterus lining.

40
Q

What are the four phases of the menstrual cycle?

A

Proliferative phase

Ovulation phase

Secretory phase

Menstrual phase

41
Q

What occurs during the different phases of the menstrual cycle?

A

Proliferative phase - the uterus lining regenerates.

Ovulation phase - the secondary oocyte is released into the oviduct from a mature follicle in the ovaries.

Secretory phase - the uterus lining secretes nutrients to prepare for embryo implantation.

Menstrual phase - the uterus lining is shed if implantation doesn’t occur.

42
Q

What occurs during the different phases of the menstrual cycle?

A

Proliferative phase - the uterus lining regenerates.

Ovulation phase - the secondary oocyte is released into the oviduct from a mature follicle in the ovaries.

Secretory phase - the uterus lining secretes nutrients to prepare for embryo implantation.

Menstrual phase - the uterus lining is shed if implantation doesn’t occur.

43
Q

What occurs during the menstrual cycle?

A

1) The pituitary gland secretes FSH.
2) FSH is transported via the blood to the ovaries where it stimulates a follicle to develop.
3) The mature follicle releases oestrogen.
4) Oestrogen thickens the uterus lining, inhibits FSH secretion and stimulates the sudden secretion of LH from the pituitary gland on approx day 11.
5) LH causes ovulation (secondary oocyte release from follicle into oviduct)
6) LH stimulates the follicle to develop into a structure called a corpus luteum, which secretes small amounts of oestrogen and large amounts of progesterone.
7) Progesterone inhibits FSH and LH, but stimulates the growth of blood vessels in the uterus lining.
8) Since LH is now inhibited, the corpus luteum degenerates and produces less progesterone which enables more FSH to be secreted.
9) If pregnancy doesn’t occur, a decrease in oestrogen and progesterone causes the outer lining of the uterus to be shed and lost in menstruation.

The cycle is repeated.

44
Q

What changes in hormone levels occur during the menstrual cycle?

A

1) The pituitary gland secretes FSH.
2) FSH is transported via the blood to the ovaries where it stimulates a follicle to develop.
3) The mature follicle releases oestrogen.
4) Oestrogen thickens the uterus lining, inhibits FSH secretion and stimulates the sudden secretion of LH from the pituitary gland on approx day 11.
5) LH causes ovulation (secondary oocyte release from follicle into oviduct)
6) LH stimulates the follicle to develop into a structure called a corpus luteum, which secretes small amounts of oestrogen and large amounts of progesterone.
7) Progesterone inhibits FSH and LH, but stimulates the growth of blood vessels in the uterus lining.
8) Since LH is now inhibited, the corpus luteum degenerates and produces less progesterone which enables more FSH to be secreted.
9) If pregnancy doesn’t occur, a decrease in oestrogen and progesterone causes the outer lining of the uterus to be shed and lost in menstruation.

The cycle is repeated.

45
Q

How does progesterone interact with other hormones during the menstrual cycle?

A

It maintains the endometrium and inhibits FSH and LH in the pituitary gland.

46
Q

How does oestrogen interact with other hormones during the menstrual cycle?

A

It repairs the endometrium, inhibits FSH and stimulates LH.

47
Q

How does FSH interact with other hormones during the menstrual cycle?

A

It stimulates the development of a Graafian follicle and stimulates oestrogen (in the ovary).

48
Q

How does LH interact with other hormones during the menstrual cycle?

A

It causes ovulation, stimulates development of the corpus luteum and stimulates progesterone.

49
Q

What occurs during fertilisation?

A

1) The sperm swim up through the cervix and uterus into the oviduct. If a secondary oocyte is present, fertilisation can occur.
2) The acrosome binds to the zona pellucida on the secondary oocyte.
3) The acrosome releases hydrolytic enzymes which digest the zona pellucida.
4) Proteins on the sperm’s head bind to the plasma membrane of the secondary oocyte.

5) The sperm and secondary oocyte membranes fuse and the sperm nucleus enters the oocyte. Fertilisation occurs and the nuclei fuse, restoring the diploid number.
The cell is now a zygote.

6) Entry of the sperm activates cortical granules in the ovum. They release enzymes that digest the sperm-binding proteins on the ovum membrane.
They also produce a hardening of the zona pellucida to prevent other sperm from entering.

50
Q

Why is fertilisation important?

A

It enables genetic variable (due to crossing over during meiosis).

51
Q

What is hCG?

A

Human chorionic gonadotropin is a hormone secreted from part of a blastocyst which will form the placenta and can be used to detect pregnancy.

52
Q

What does hCG do?

A

By maintaining the corpus luteum that surrounds the egg, human chorionic gonadotropin also maintains the lining of the uterus, which is necessary to sustain a pregnancy if an egg is fertilized.

When the corpus luteum surrounding an unfertilized egg dies, falling hormone levels cause the uterine lining to slough, which results in a menstrual period.
By maintaining the uterine lining, hCG provides a place for embryonic development.

The embryo is totally dependent on the uterine lining until the placenta is fully formed, usually during the fourth month of pregnancy.

53
Q

How does fertilisation occur?

A

1) The sperm swim up through the cervix and uterus into the oviduct. If a secondary oocyte is present, fertilisation can occur.
2) The acrosome binds to the zona pellucida on the secondary oocyte.
3) The acrosome releases hydrolytic enzymes which digest the zona pellucida.
4) Proteins on the sperm’s head bind to the plasma membrane of the secondary oocyte.

5) The sperm and secondary oocyte membranes fuse and the sperm nucleus enters the oocyte. Fertilisation occurs and the nuclei fuse, restoring the diploid number.
The cell is now a zygote.

6) Entry of the sperm activates cortical granules in the ovum. They release enzymes that digest the sperm-binding proteins on the ovum membrane.
They also produce a hardening of the zona pellucida to prevent other sperm from entering.

54
Q

How does a pregnancy test (stick) work?

A

1) Urine containing hCG contacts the dipstick.
2) The dipstick contains hCG antibodies with a blue latex particle attached.
3) hCG from the urine sample binds to the hCG antibodies.
4) The antibodies move up along the dipstick.
5) A row of antibodies immobilised at this point bind to the antibodies that have hCG attached.
6) This forms a blue line at this position to indicate pregnancy.
7) A row of antibodies immobilised at this point bind to antibodies that don’t have hCG attached.
8) A blue line in this position ONLY means that the woman is not pregnant.

55
Q

What are the causes of infertility in males?

A

Abnormal sperm, e.g. lack of tails, due to failure to develop properly in the testes.

Production of antibodies that destroy sperm in the semen.

Blockages in the sperm ducts.

Low sperm count.

56
Q

What are the causes of infertility in females?

A

Ovulatory disorders such as a failure to ovulate (due to low hormone levels).

Production of antibodies that destroy the sperm in the uterus.

Blockages in the oviducts e.g. from bacterial infection or endometriosis where uterine layer develops outside the uterus.

57
Q

What are the treatments for infertility?

A 
IVF
   ICSI
   GIFT
Artificial insemination 
Intrauterine insemination 
Ovulation induction
58
Q

What occurs during IVF?

A

Fertility drugs are taken to stimulate the production of eggs meanwhile the male produces a sperm sample.
The oocyte is then removed from the female and fertilised within a lab to form an embryo which is then transferred into the mother’s uterus.

59
Q

What occurs during ICSI?

A

Intra-cytoplasmic sperm injection is an IVF treatment where a single sperm is injected directly into the oocyte, to increase the chance of fertilisation, then is implanted into the womb.
An operation is required to remove sperm from the epididymis.

60
Q

What occurs during GIFT?

A

Gamete intra-fallopian transfer is similar to IVF however, rather than fertilisation occurring within a lab, the sperm and oocyte is passed into the oviduct to enable natural fertilisation.

61
Q

What occurs during artificial insemination?

A

This implies any method involving the introduction of semen into the female reproductive tract without sexual intercourse.
Semen can be placed into the vagina or cervix without the need for special preparation. (Sperm from partner or donor.)

62
Q

What occurs during intrauterine insemination?

A

Sperm (rather than semen) is injected into the uterus at ovulation.
This is used when there are male physical issues e.g. erectile difficulties or premature ejaculation.

63
Q

What occurs during surgical sperm removal?

A

SSR is used when sperm is produced but can’t be ejaculated e.g. due to blockage of the vas (where sperm collects in the scrotum). Sperm can be obtained from the epididymis by using a fine needle or a biopsy of the testes.

64
Q

What occurs during ovulation induction?

A

Follicles in the ovaries are stimulated to develop and form visible secondary oocytes. This is done by providing drugs which either inhibit oestrogen or stimulate FSH and LH to be released.

65
Q

What’s a Graafian follicle?

A

A mature liquid-filled cavity in a mammalian ovary that ruptures during ovulation to release an egg.

Graafian follicles are fluid-filled shell that surrounds and protects the developing egg cell inside the ovary during the menstrual cycle.

Once the Graafian follicle has ruptured, it fills with blood. This blood is rapidly substituted by luteal cells, and the follicle becomes the “corpus luteum.

66
Q

How does the corpus luteum form?

A

Once the Graafian follicle has ruptured, it fills with blood. This blood is rapidly substituted by luteal cells, and the follicle becomes the “corpus luteum.”

The luteal cells manufacture oestrogen and progesterone and this is known as part of the menstrual cycle.

If pregnancy follows, the corpus luteum remains, but if there is no pregnancy, it starts to break down a few days before the start of the next menstrual bleed, ending up as scar tissue.

Year 12 - Biology (15 decks)

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