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Component 2 Biology > Human reproduction > Flashcards

Human reproduction Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is the function of the scrotum?

A

It’s the external sac that holds the testes out of the body, it gives an optimum temperature of sperm production of 35°C.

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2
Q

What is the function of the testes?

A

To produce male gametes (spermatozoa)

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3
Q

What is the function of the urethra in a male?

A

The tube which connects the bladder to the outside, passes through the penis and transfers urine and semen to the outside.

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4
Q

What is the function of the penis?

A

The organ which passes semen into the reproductive system. Erectile tissue fills of blood for penetration of the vagina.

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5
Q

What is the function of van deferens?

A

The tube which takes a sperm from the testes to the urethra during ejaculation

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6
Q

What is the function of the Epididymis?

A

It’s where the sperm collect and mature

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7
Q

What is the function of the seminiferous tubules?

A

The tubes which are found in the testes, site of sperm production

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8
Q

What is the function of the prostate gland?

A

The glands found at the base of the bladder which produces alkaline secretions to neutralise any urine left in the urethra, neutralise the acidity of the vagina tract and aid sperm mobility.

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9
Q

What is the function of the seminal vesicle?

A

The gland which produces a nutrient secretion which helps sperm mobility.

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10
Q

What is the role of the Sertoli cells?

A

They help nourish and protect the spermatozoa once they are formed, they protect them from their own immune system as spermatozoa or identified as foreign.

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11
Q

Give details about the ovaries?

A

There are two ovaries, oocytes mature in follicles which develop from germinal epithelium cells around the periphery of the ovary. A secondary oversight is released at ovulation. The ovaries alternate each month in releasing the oocyte.

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12
Q

What is the function of the ovary?

A

3-4 cm wide

They are the female sex organs which produce female gametes (oocytes) and secrete hormones: oestrogen and progesterone.

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13
Q

What is the function of the fallopian tube/oviduct?

A

Connect the ovary to the uterus, it collects the oocyte following ovulation and it’s where fertilisation occurs.

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14
Q

What is the function of the perimetrium?

A

Thin layer around the outside

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15
Q

What is the function of the myometrium?

A

Muscular layer

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16
Q

What is the function of the endometrium?

A

It’s the innermost layer in which the embryo becomes implanted in the endometrium. The internal surface sheds each month (menstruation) if there is no embryo.

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17
Q

What is the function of the cervix?

A

It’s the neck of the uterus, a muscular ring which closes the entrance to the uterus, it dilates during birth.

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18
Q

What is the function of the vagina?

A

It’s the muscular tube that leads to the outside of the body.

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19
Q

What is the function of the urethra in a female?

A

Connects the bladder and allows the passage of urine

NOT PART OF THE FEMALE REPRODUCTIVE SYSTEM

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20
Q

What is the function of the bladder?

A

Storage of urine.

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21
Q

Where does spermatogenesis occur?

A

In the seminiferous tubules of the testes.

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22
Q

What is spermatogenesis?

A

It’s the production of haploid spermatozoa from diploid spermatogonium.

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23
Q

What is the process called between primary spermatocyte and secondary spermatocyte?

A

It’s known as maturation in which diploid primary spermatocytes undergo meiosis I to produce secondary spermatocytes.

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24
Q

When do sperm produce their mid piece and tail?

A

It differentiates between spermatids and spermatozoa

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25
Q

When does spermatogenesis start and finish?

A

It starts from puberty and continues until death.

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26
Q

How long does it take for spermatozoa to mature and differentiate?

A

It takes two months for it to mature with five weeks to differentiate.

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27
Q

Why is mitochondria found in the mid piece?

A

To provide ATP for movement.

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28
Q

When do all primary oocytes form?

A

They form prior birth but stop at prophase one

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29
Q

What happens at puberty in oogenesis?

A

Puberty every month FSH is released from the pituitary gland which stimulates the development of primary follicles to secondary follicles. It finishes meiosis I to become a secondary oocyte. It starts meiosis II but stops at metaphase II. It’s now a Graafian follicle which migrates to the surface of the ovary where it bursts projecting the secondary oocyte into the fallopian tube- OVULATION

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30
Q

What happens if fertilisation occurs in oogenesis?

A

An ovum is formed if fertilisation has occurred, meiosis has been completed. The nuclei fuse to become a zygote.

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31
Q

What happens between puberty and menopause?

A

One oocyte per month will start dividing again but stop at metaphase II (then ovulated). Meiosis II is only completed if fertilised..

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32
Q

What is the zona pellucida?

A

It is a glycoprotein layer which surrounds the cell membrane of the secondary oocyte the chromosomes are at metaphase II

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33
Q

What do cortical granules prevent?

A

Polyspermy

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34
Q

What is the corona radiata?

A

They are cells which surround the secondary oocyte and provide nutrients.

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35
Q

Describe the menstrual cycle?

A

It occurs in the uterus to prepare for a fertilised egg. Repeating a series of changes in the endometrium. Continues from menarche to menopause.

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36
Q

Where does the ovarian cycle occur?

A

In the ovary

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37
Q

What is the role of the hormones in the menstrual cycle?

A

They control the reproductive cycle and coordinate the ovarian and uterine cycle.

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38
Q

What are the four key hormones?

A

FSH, LH, oestrogen and progesterone

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39
Q

Where is FSH and LH produced?

A

In the anterior pituitary gland

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40
Q

Where is oestrogen and progesterone produced?

A

ovaries

41
Q

When do timing start?

A

From the onset of bleeding

42
Q

When is the follicular phase?

A

From 0 to 14 days (ovulation) (variable)

43
Q

What is ovulation triggered by?

A

Surge in LH

44
Q

When is the luteal phase?

A

14 days to end of cycle (fixed)

45
Q

What happens when the corpus luteum declines?

A

Progesterone levels drop and cycle starts again.

46
Q

Describe the follicular phase

A
  • Day 0 is the first day of a period.
  • On this day all 4 hormone concentrations are low in the plasma.
  • The hypothalamus secretes gonadotrophic releasing hormone (GnRH) which is secreted by the hypothalamus to stimulate the anterior pituitary gland to release FSH and a small amount of LH.
  • FSH stimulates the development of primary follicles in the ovary. It also stimulates thecal cells on the Graafian follicle to produce oestrogen.
  • Oestrogen causes the rebuilding of the endometrium as well as inhibit FS secretion and stimulates LH secretion.
47
Q

What happens at ovulation?

A

The main role of LH is to induce ovulation. One day 14 the high concentration causes the Graafian follicle at the surface of the ovary to release the secondary oocyte.

48
Q

Describe the luteal phase?

A
  • After ovulation (around day 14) the Graafian follicle is retained in the ovary as the corpus luteum which produces progesterone and oestrogen.
  • After ovulation progesterone and oestrogen both inhibit the production of FSH and LH reducing their concentration.
  • Progesterone stimulates the endometrium to thicken and remain in place.
  • Oestrogen triggers the rebuilding of the endometrium, inhibits FSH secretion by negative feedback which decreases its own concentration and stimulates LH production by positive feedback.
49
Q

Describe his breakdown?

A

If there is no implantation (day 21) the fallen concentrations of FSH and LH causes the corpus luteum to breakdown. Breakdown occurs within 14 days if no embryo is present.
The breakdown of the corpus luteum means that progesterone production declines causing the endometrium to shed (day 28).
As oestrogen is low it no longer inhibits FSH production so the menstrual cycle will restart.

50
Q

Describe the journey of the sperm?

A
  • The sperm is released from the epidermis and travels along the van deferens out of the penis through the urethra.
  • Spermatozoa are deposited at the top of the vagina and swim through the cervix and along the uterus lining into the oviduct where they meet the secondary oocyte
51
Q

When must fertilisation occur?

A

12 to 24 hours after ovulation in the oviduct.

52
Q

What is fertilisation?

A

A sequence of events from the point at which a sperm and the secondary oocyte make contact

53
Q

Summarise the steps?

A
  1. Sperm surrounding the secondary oocyte in the oviduct.
  2. Capacitation.
  3. Acrosome reaction.
  4. Sperm head entry.
  5. Cortical reaction.
  6. Meiosis.
  7. Mitosis.
54
Q

Describe the step when the sperm surrounds a secondary oocyte?

A

This occurs after sexual intercourse. The sperm responds to chemicals produced by the secondary oocyte.

55
Q

Describe capacitation?

A
  • It occurs as the sperm moves through the fluid in the uterus.
  • It causes a change in the membrane covering the acrosome which causes an increase chance of the sperm binding to the oocyte.
56
Q

What do the enzymes in the uterus cause?

A
  • Removal of cholesterol and glycoproteins in the acrosome membrane makes it more fluid.
  • The sperm membrane becomes more permeable to calcium ions which increases tail activity and starts the acrosome reaction.
57
Q

What is the acrosome reaction?

A
  • It’s when the acrosome membrane ruptures due to contact with the outer jelly coat releasing hydrolytic protease enzymes.
  • the sperm pushes its way through the Corona radiator by the gaps in the cells.
  • it allows the sperm head to come in contact with the zona pellucida.
  • the hydrolytic enzymes within the acrosome are released which hydrolyses the zona pellucida.
58
Q

Describe the sperm head entry step?

A
  • It’s enabled by the action of acrosin (protease) enzyme.
  • The cell membranes of the oocyte and sperm fuse.
  • Stimulates the completion of meiosis II
59
Q

What is the cortical reaction?

A
  • It’s when the cortical granules in the ovum release enzymes by exocytosis. It causes the change in the zona pellucida structure to produce a fertilisation membrane (zona pellucida expands and hardens).
60
Q

What is the cortical reaction triggered by?

A

The entry of the male nucleus in to the cytoplasm which causes calcium ions to be released from the oocytes SER.

61
Q

What does the cortical reaction prevent?

A

Polyspermy (more than one sperm fusing with the egg)

62
Q

What happens during meiosis II?

A

The second meiotic division completes an ovum is formed containing a female nucleus and a second polar body.

63
Q

What happens during mitosis?

A
  • The female chromosomes lineup along the mitotic equator.
  • The nucleus fuses (over nucleus with the sperm nucleus to form a diploid zygote.
  • The first mitotic division produces two cells which are referred as an embryo.
64
Q

What is produced after fertilisation?

A

A diploid zygote

65
Q

What is the sequence called as the embryo moves down the oviduct dividing by mitosis?

A

Cleavage (2, 4, 8, 16 cell structures)

66
Q

What is the solid ball of 16 cells known as?

A

Morulla (72 hours)

67
Q

What happens when the zygote divides by mitosis?

A

It divides to form a hollow ball of undifferentiated cells the cells form the trophoblast which are on the outside of the blastocyst which has an inner cell mass on one side.

68
Q

What is implantation?

A

It’s around seven days post fertilisation where the blastocyst moves from the oviduct to the uterus where it gets embedded into the endometrium.

69
Q

Describe implantation?

A
  • The outer layer of cells, the trophoblast develops protrusion is called trophoblastic villi.
  • The endometrium simultaneously has thickened with an increase in blood supply.
  • The trophoblastic villi penetrate into the endometrium giving a large SA for exchange of nutrients.
  • The embryo will derive nutrients from the endometrium during the next 2-4 weeks
  • The trophoblast then develops into the chorion - an outer membrane surrounding the embryo,
  • Cells of the chorion move into the trophoblastic villi to form the large chorionic villi - location of the foetal blood vessels
70
Q

What is the implantation window?

A

6-10 days after ovulation

71
Q

What % of blastocysts will inked between 8-10 days

A

80%

72
Q

What produces HCG?

A

The chorion layer

73
Q

What is the function of the HCG hormone?

A

To maintain the corpus luteum in the ovary for the first 16 weeks of pregnancy. This hormone forms the basis of the pregnancy testing kit.

74
Q

What is the placenta?

A

It connects the embryo/ foetus to the uterus wall

75
Q

Describe the blood flow for the umbilical cord?

A

Blood from the embryo travels to the placenta through umbilical arteries and returns via the umbilical vein.

76
Q

What are the 5 roles of the placenta?

A
  1. Secretion of hormones
  2. Exchange of O2/CO2
  3. Barrier
  4. Immunity
  5. Protection
77
Q

What hormones does the placenta secrete?

A

Progesterone and oestrogen (takes over from the corpus luteum)

78
Q

How is O2 and CO2 exchanged through the placenta?

A

Nutrients and waste with the mother circulation

79
Q

What does the placenta act as a barrier against?

A
  • high blood pressure
  • blood born pathogens
  • toxins in the maternal blood
80
Q

How does the placenta give immunity?

A

It allows the maternal antibodies to protect the foetus by passive immunity.

81
Q

How does the placenta aid protection?

A

It aids from the mothers immune system, preventing white blood cells from the mother passing into the foetal blood circulation.

82
Q

What are the complications of the placenta?

A

Doesn’t provide complete immunological protection

  • spontaneous abortions = organ rejection
  • pre-eclampsia - very high blood pressure in the mother.
  • some viruses can cross the placenta ie rubella
  • some drugs can cross the placenta ie heroin.
83
Q

How many umbilical arteries does the placenta have?

A

2

84
Q

How many umbilical veins does the placenta have?

A

1

85
Q

Where does the umbilical arteries carry blood to?

A

Carries foetal blood to the placenta

86
Q

Where does the umbilical vein carry blood to?

A

Carries blood back to the foetus

87
Q

Where is the foetal blood carried over?

A

A large surface area of chronic villi, these have micro-villi to increase the surface area in which it is in contact with the mothers blood.

88
Q

Where does the maternal blood flow into?

A

It flows into the intervillous space in the endometrium from the uterine artery and flows out through the uterine vein.

89
Q

What mechanism does the umbilical arteries and veins have?

A

a counter current flow

90
Q

What does the amnion surround?

A

developing follicles

91
Q

What is the amnion?

A

It is a membrane derived from the inner cell mass of the blastocyst. Initially the amnion is in contact with the foetus but after 4-5 weeks amniotic fluid starts to accumulate pushing the amnion membrane outward.

92
Q

How does the amniotic fluid protect the foetus during development?

A 
By: 
maintaining temp 
providing lubrication 
contributing to lung development 
allowing movement 
acting as a shock absorber.
93
Q

What produces progesterone and oestrogen?

A

First the corpus luteum and then the placenta which continues to inhibit FSH and LH release preventing more follicles maturing and ovulation.

94
Q

What does progesterone also suppress?

A

The ability of the uterine walls to contract

95
Q

What does oestrogen stimulate the growth of?

A

The growth of the uterus to accommodate the foetus and growth and development of mammary glands.

96
Q

What happens to oestrogen and progesterone levels before birth?

A

Oestrogen levels are still increasing and progesterone levels begin to decrease, the uterine walls begin to contract. The decrease of progesterone allows the secretion of oxytocin and prolactin.

97
Q

What is oxytocin?

A

It’s secreted by the posterior pituitary gland and causes contractions of the myometrium. Positive feedback occurs which leads to an increase level of oxytocin and stronger contractions.

98
Q

What is prolactin?

A

It is secreted by the anterior pituitary gland, stimulates the mammary glands to synthesise milk. Milk is released when oxytocin causes the muscles around the milk duds to contract.

Component 2 Biology (9 decks)

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