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GERR > Fertilisation, Implantation and Gastrulation > Flashcards

Fertilisation, Implantation and Gastrulation Flashcards

1
Q

When do sperm need to arrive in female reproductive system to be successful?

A

1-2 days before or after ovulation

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2
Q

What changes occur in cervical mucus at ovulation?

A

Increase in amount and less thick allowing easier transport of sperm also less acidic

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3
Q

What is the function of fimbria?

A

Help move the ovum from the ovary into the Fallopian tube

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4
Q

What movement of the Fallopian tube brings the ovum through it?

A

Moves to Ampulla of Fallopian tube, peristaltic wave of Fallopian tube

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5
Q

How long can sperm survive in the female reproductive system?

A

5 days

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6
Q

What process prepares the sperm to fertilise an egg?

A
  • Capacitation - remodelling of the sperms glycoprotein coat
  • membrane molecules are masked by plasma proteins these membrane molecules need to be removed to reveal binding sites
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7
Q

Where does capacitation take place and how long does it take?

A
  • Uterus and oviduct

- 5-7 hours

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8
Q

What does the passage of sperm through cumulus layer depend on?

A
  • Hyaluronidase released from sperm acrosome
  • tubal mucosal enzymes
  • Flagellar action
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9
Q

What is the function of the zone pellucida?

A

glycoprotein shell which facilitates and maintains sperm binding and induces acrosome reactions

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10
Q

What triggers the acrosome reaction?

A
  • multiple adhesions of sperm to the zona pellucida
  • triggers opening of calcium channels of sperm cell membrane driving exocytosis of acrosomal content
  • Needs to happen for fertilisation to continue
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11
Q

What is the acrosome?

A

modified lysosome located around anterior of the Spermatozoon head

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12
Q

What other reaction is triggered by the sperm binding?

A

Cortical reaction - exocytosis of cortical enzymes into ZP

  • this destroys sperm receptors on ZP
  • and causes hardening of the ZP (zona reaction)
  • This means no more sperm can enter the cell
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13
Q

What is the process of multiple sperm entering ovum called and what does this usually result in?

A

Polyspermy
2 = dispermy
3 = triploidy
if this happens foetus nearly always aborts

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14
Q

What are stages 1 and 2 of fertilisation?

A

1) sperm preparation

2) sperm-egg recognition and binding

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15
Q

What are stages 3 and 4 of fertilisation?

A
  • fusion of plasma membrane of oocyte and sperm
  • triggering completion of meiosis II of oocyte (haploid now)
  • Head and tail of sperm enter cytoplasm of oocyte
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16
Q

What is stage 5 of fertilisation?

A

Formation of male and female pronuclei

  • membranes of pronuclei begin to breakdown and chromosomes become arranged for mitotic cell division
  • fertilisation complete
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17
Q

How many chromosomes do pronuclei contain?

A

23

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18
Q

What is a fully fertilisatilised egg called?

A

Zygote

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19
Q

What is a fully fertilisatilised egg called?

A

Zygote - after complete fusion of oocyte and sperm

20
Q

What is cleavage?

A
  • Series of mitotic divisions. of the zygote

- The resulting cells (blastomeres) become smaller with each division

21
Q

After which division do blastomeres undergo compaction and what happens next?

A

3 divisions

  • blastomeres compact
  • then divide to form a 16 cell morula
22
Q

What are the two cell types of blastocyst?

A

Outer cell mass (trophoblast give rise to placenta)

Inner cell mass (embryoblast gives rise to foetus)

23
Q

How do blastocysts form?

A
  • Morula develop into blastocysts 5-7 days after fertilisation
  • central cavity forms, filled with fluid (blastocoel) from the ZP
  • Two distinct cell types found trophoblasts and embryoblasts
24
Q

What epithelium lines the uterus?

A

simple columnar (endometrium)

25
Q

What does IVF stand for?

A

In Vitro Fertilisation

26
Q

What happens in IVF?

A

1) Hormonal stimulation of egg maturation
2) Removal of eggs by laproscopy
3) Collection of sperm sample and concentration of most active sperm
4) In vitrofertilisation
5) Early cleavage in vitro
6) Extra embryos frozen
7) reimplantation of up to three embryos

27
Q

What cells do the trophoblasts Divide and differentiate to from?

A 
Outer syncytiotrophoblasts (which invade the ovary) 
Inner Cytotrophoblasts
28
Q

What two cells do the embryo blast cells divide and differentiate to form?

A

Epiblasts (upper cell layer)

Hypoblasts (lower cell layer)

29
Q

What phase is the uterus in at time of implantation for IVF?

A
  • secretory phase
30
Q

What is the function of the acrosome?

A

Perforations in acrosome allow release of acrosome enzymes which facilitate sperm heads binding and penetration of ZP
- this must happen before Sperm can fuse to cell membrane of oocyte

31
Q

What cell secrete Human Chorionic gonadotrophin and what is its function?

A

syncytiotrophoblasts

  • tells corpus luteum to continue producing progesterone and oestrogen
  • This means the endometrial lining knows to stay in place (not shed), remains in secretory phase
32
Q

Where does the amniotic cavity form and why is it so important?

A

In the epiblast

- results in formation of bilaminar disk (which is what the foetus forms from)

33
Q

What is Gastrulation and when does it occur?

A
  • Formation of the three embryonic germ layer (previously two: epiblast and hypoblast)
  • Wk 3
34
Q

What are the three germ layers of trilaminar disc which forms after gastrulation?

A
  • Ectoderm
  • Mesoderm
  • Endoderm
35
Q

What happens in Gastrulation?

A
  • organism becomes organized
  • Groups of cells which form specific organ systems and tissue are moved together
  • Cells which will influence each other are also moved in such a way that they can do that
36
Q

What is the first step of gastrulation?

A

Formation of primitive streak which is a dipped line that forms at the hind of the zygote which will form parts of the reproductive system and anal canal

37
Q

What membranes form the head and hind region of the foetus?

A

Cloacal membrane = hind

Oropharyngeal = head

38
Q

What are the parts of the primitive streak?

A

Primitive pit and primitive node at the tip also includes a groove

39
Q

What aspects of the primitive streak forms what part of the body?

A

Anterior part - Cranial
Posterior - Caudal
right and left - lateral

40
Q

What occurs to create the three layers of gastrulation?

A

Epiblast cells lose their attachment to each other and begin to roll over the primitive ridge into the groove (migrate inwards)

41
Q

Where do the epiblast cells which have migrated move to?

A
  • First cells integrate and displace hypoblast cells to form endoderm
  • some cells lie in the middle to form mesoderm
  • remaining cells in epiblast form ectoderm
42
Q

What is the benefit of gastrulation?

A

1) Primary germ layer formed
2) Organized into proper location
3) creates body axis (anterior-posterior, dorsal-ventral and Left-Right)

43
Q

What body parts are formed from the Ectoderm?

A

Ectoderm - CNS, PNS, sensory epithelia of the eye, ear, nose, epidermis and its appendages, mammary glands and pituitary glands

44
Q

What body parts are formed from the Mesoderm?

A

Connective tissue, striated muscle and smooth muscle, heart, blood vessels, lymphatic vessels, kidneys, ovaries, testes, spleen, serous membrane (lining body cavities)

45
Q

What body parts are formed from the Endoderm?

A

epithelial lining of the GI, respiratory tract bladder and urethra, thyroid and parathyroid, liver and pancreas

GERR (49 decks)

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