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Biology > 11.4-Sexual Reproduction > Flashcards

11.4-Sexual Reproduction Flashcards

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1
Q

Oogenesis

A

Oogonium → Oogonia → Primary Oocyte [stopped in prophase I] → (loses 1st polar body) Secondary Oocyte [stopped in metaphase II]→ (loses 2nd polar body after its fertilised) Ovum

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2
Q

Spermatogenesis

A

Spermatonium → spermatogonia → primary spermatocyte → secondary spermatocyte → spermatid → spermatozoa

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3
Q

Sertoli Cells

A

Helps the spermatids to develop into spermatozoas
→ gives them nutrients and nurse them
→ can also detect cells that aren’t developing properly = can cancel them and digest

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4
Q

Epididymis

A

** Where the sperm is stored**
+ Testicle fluid = removed
+ Sperm mature here and dev. ability to swim

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5
Q

Where is sperm made?

A

In seminifourous tubules

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6
Q

Which cells produce testosterone to initiate spermatogenesis?

A

Leydig cells

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7
Q

Seminal Vesicles

A

+ adds nutrients that include fructose for respiration

+ Mucus to protect sperm

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8
Q

Prostate gland

A

+ Adds fluids that neutralise the vaginal acids and mineral ions
+ Prostoglandins = switch sperm cells on to start swimming

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9
Q

What happens when the spermatozoas are ready to be released?

A

+ The muscular contractions squeeze the epididymis to release the sperm cells into the Vas Deferens to go up!
+ It also squeezes the glands to provide nutrients and protection for the cells

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10
Q

Zona Pellucida

A

Layer of gel composed by glycoproteins

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11
Q

Corona Radiata

A

Layer of follicle cells

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12
Q

Acrosome vesicle

A

Contain enzymes required to digest its way through the ovum wall

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13
Q

Microtubules in the Flagellum are in what arrangement?

A

9+2 arrangement

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14
Q

Function of Protein fibres in the spermatozoa

A

To strengthen tail = add longitudinal rigidity and provide mechanism for propulsion

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15
Q

Helicle mitochondrion in spermatozoa

A

Synthesise ATP to provide energy for movement of tail structure

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16
Q

Fertilisation makes a?

A

Zygote

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17
Q

Polyspermy is?

A

When multiple cells enter the egg

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18
Q

Preventing Polyspermy Step 1: Acrosome reaction

A

+ The sperm must penetrate the thick cumulus mass to reach the Zona Pellucida
+ The contact betw/ the Zona Pellucida and proteins in the sperm cell membrane = trigger acrosome reaction
+ Acrosome vesicle fuse w. sperm plasma membrane and releases enzymes that digest a pathway through the Zona Pellucida

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19
Q

Preventing Polyspermy Step 2: Penetration of Egg Membrane

A

+ The acrosome reaction exposes an area of membrane on tip of the sperm that has proteins that can bind to egg membrane
+ The 1st sperm that gets through the Zona Pellucida → binds to the membrane = sperm and egg fuse
+ Sperm nucleus enters the egg cell = fertilisation!
+ Ca2+ released from egg endoplasmic reticulum

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20
Q

Preventing Polyspermy Step 3: The Cortical Reaction

A

+ Sperm causes the activation of the egg
+ Cortical Granules (vesicle located near egg membrane)
→ When egg activated = their contents released from egg by exocytosis
+ In mammals = Cortical vesicle enzymes = digest the binding proteins → no further sperm can bind
+ Enzyme also results in general hardening of Zona Pellucida
+ Release of Ca2+ ions = activates meiosis and prepare cell for completion of meiosis II and cell division

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21
Q

External fertilisation

A

+ Aquatic animals often release their gametes directly into the water
→ animals have behaviours that bring eggs in close proximity w/ sperm

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22
Q

What are the risks of External fertilisation (5)

A 
\+ predation
\+ Susceptibility to environmental variation
\+ Temp.
\+ pH fluctuations 
\+ pollution
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23
Q

Internal fertilisation

A

+ Terrestrial animals → or else gametes will dry out
+ Ensures sperm and ova = placed in prolonged close proximity to e.o
+ Once egg fertilised → developing embryos can be protected inside female

24
Q

What happens to ovum after it is fertilised?

A

+ Divides by mitosis to form 2 diploid nuclei and cytoplasm = divides equally forming 2-cell embryo
+ 2-cell embryo → replicate DNA → carry out mitosis → divide again → form 4-cell embryo
= abt 48hrs

25
Q

What happens to the 4-cell embryo after 48hrs?

A

+ Further cell division happens BUT it is unequal
→ leads to migration of cells = embryo shaped like a hollow ball
→ BLASTOCYST = not even recognisable as anything (ball of stem cells!)

26
Q

What happens to the Blastocyst at 7 days after fertilisation?

A

+ consists of abt 125 cells
+ been moved by the cilia of cells in oviduct wall → down the oviduct
+ reached the uterus
+ Zona Pellucida = broken down → blastocyst has used up the reserves of egg = needs external food supply

27
Q

Implantation

A

+ Blastocyst sinks into the endometrium
+ Outer layer of Blastocyst = develops finger like projections = allowing it to penetrate the endometrium
+ Also exchange materials w/ mother’s bl. = absorbing food and O2

28
Q

After 8 weeks what is the embryo now called?

A

Fetus

→ recognisable as human and sex can be determined soon

29
Q

What does pregnancy depend on?

A

The maintenance of the endometrium

→ which depends on the continual production of progesterone and oestrogen

30
Q

In early pregnancy what hormone does the embryo produce? and what does it do?

A

hCG

→ stimulates the corpus luteum to continue to secrete progesterone and oestrogen

31
Q

What does the placenta do?

A

Facilitates the exchange of materials betw/ mother and embryo
→ needed cuz the body surface area to vol. ratio = becomes smaller as fetus grows larger

32
Q

What is the placenta made of?

A

Fetus tissues, in contact w/ maternal tissues in uterus wall

+ Fetus dev. membrane that forms amniotic sac that contains amniotic fluid → to support and protect the fetus

33
Q

What is the basic functional unit of the placenta?

A

Placental Villus

→ increase in # during pregnancy = to cope w/ the increase demands of foetus for exchange of materials w/ mother

34
Q

Where does the maternal blood flow?

A

In the intervillous space around the villi

35
Q

Where does the foetus blood circulate?

A

in blood capillaries close to the surgace of each villus

36
Q

How big is the distance betw/ the foetal and maternal blood?

A

V. small = 5μm approx.

37
Q

What is the placental barrier?

A

Cells that separate maternal and foetal blood

→ MUST be selectively permeable = allowing some substances to pass BUT not others!

38
Q

What is the chorion?

A

The foetal part of the placenta

39
Q

Is blood in the umbilical vein oxygenated or deoxygenated?

A

Oxygenated

40
Q

Is blood in the umbilical arteries oxygenated or deoxygenated?

A

Deoxygenated

41
Q

By 9 weeks of the pregnancy what does the placenta secrete?

A

Oestrogen and Progesterone in LARGE quantities to sustain the pregnancy!
→ The Corpus Luteum is no longer needed
→ There is danger of miscarriage IF the switch fails

42
Q

How does O2 and CO2 move in and out of the foetal blood past the placental barrier?

A

Diffusion

43
Q

How does glucose move into the foetus blood past the placental barrier?

A

Facilitated diffusion

44
Q

How do antibodies move into the foetal blood past the placental barrier?

A

Endocytosis

45
Q

How does water move in and out of the foetal blood past the placental barrier?

A

Osmosis

46
Q

Parturition?

A

Child birth

47
Q

What is birth mediated by?

A

Positive feedback involving oestrogen and oxytocin

48
Q

During pregnancy which hormone does progesterone inhibit?

A

Oxytocin by the pituitary gland = inhibits the contractions of muscular outer wall of the uterus (Myometrium)

49
Q

At the end of pregnancy what happens to the different hormone levels?

A

+ Hormones produced by the foetus = signal to the placenta to STOP secreting pregesterone and therefore Oxytocin is produced.

50
Q

What does oxytocin stimulate?

A

The contraction of muscle fibres in the Myometrium

51
Q

Positive feedback mechanism of oxytocin

A

The contractions stimulated by oxytocin = detected by stretch-receptors = signal to pituitary gland (posterior) to secrete more oxytocin
+ Oxytocin makes contractions more freq. and more vigorous which stimulates increase secretion of more oxytocin

52
Q

What does the freq. increase in contraction cause?

A

Gradual increase in the myometrial contractions = allowing baby to be born w/ min intensity of contractions

53
Q

What causes the cervix to dilate?

A

Relaxation of muscle fibres

54
Q

What bursts the amniotic sac?

A

Uterine contraction → causes amniotic fluid to pass out

55
Q

What finally happens to push the baby out?

A

Further uterine contractions (over hrs)

56
Q

Altricial species

A

Give birth to relatively helpless, incompletely developed young/ offspring

57
Q

Precocial species

A

Offspring hv. open eyes, hair = immediately mobile and somewhat able to defend themselves against predators
+ Mammals w/ large body size = more likely to be precocial → correlate w/ long gestation period

Biology (12 decks)

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