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GGE > Embryos - Implantation > Flashcards

Embryos - Implantation Flashcards

1
Q

Where does fertilisation occur

What does it begin with

A

Begins with contact of sperm with secondary oocyte

ends with formation of zygote (1 cell embryo)

Occurs in ampulla of fallopian tube

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2
Q

Average volume of semen

A

2.5-3.5 ml after 3 days abstinence (2-6ml)

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3
Q

What is the fertility index

A

At least 20 million sperm/ml

40% sperm show vigorous swimming

60% normal shape

pH 7.35-7.5

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4
Q

Seminal vesicles (2/3) releases

A

Water

Fructose

Fibrinogen

Vit C

Prostaglandins

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5
Q

Prostate releases

A

Water buffers

Fibrinoginase (clotting)

Fibrinolytic enzyme (liquification)

Citric acid

Prostaglandins

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6
Q

Bulbourethral gland releases

A

Water

Buffers

Mucus

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7
Q

Epididymis releases

A

Water

Nutrients

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8
Q

1 min after ejaculation

A

Semen coagulation - fibrinogenase

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9
Q

20 min after ejaculation

A

semen liquifaction by the fibrinolytic enzyme in seminal plasma

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10
Q

How does the female prevent sperm entry

How is this overcome

A

Thick mucous prevents entry (keeps micro-organisms out)

Preovulatory rise in oestrogen makes the mucus thin and watery

(Sperm swim through 1.2-3mm/min)

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11
Q

Life span of sperm

A

3-6 days

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12
Q

process of fertilisation

A
  • Secondary oocyte - 1st polar body

surrounded by granulosa cells and Zona Pellucida

  • Acrosome rxn
  • Hyaluronidase - loss of corona (derived from golgi apparatus)
  • Acrosin and neuminidase facilitate passage through ZP
  • On contact with plasmallema of oocyte zona rxn prevents polyspermy - release of cortical granules
  • contact induces secondary oocyte to divide to become ootid (ovum) and 2nd polar body - nucleus known as female pronucleus
  • Tail of sperm degenerates
  • Head and centriole enter
  • Head forms male pronucleus
  • Pronuclei fuse to form zygote
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13
Q

What are the results of fertilisation

A
  • Restoration of diploid number - 46
  • Determination of chromosomal sex of embryo
  • Variation of human species - new combination of chromosomes
  • Intitiation of cleavage - mitotic division of zygote into blastomeres
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14
Q

What happens to the zygote as it passes along the fallopian tube

A

Undergoes cleavage to daughter cells - blastomeres

New cells are smaller after each division

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15
Q

Describe the formations within the 1st week of human life

A

16 cell embryo - morula

Blastocyst with blastocyst cavity - 4 days

Outer flattened cells - trophoblast

Inner cells - inner cell mass

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16
Q

Trophoblast

A

Embryonic part of the placenta

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17
Q

Inner cell mass

A

Primordium of the embryo

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18
Q

When does the ZP disappear

What does this signal the beginning of

A

5-6 days after fertilisation

Process of implantation begins

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19
Q

Process of fertilisation

A
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20
Q

What do the polar body and oocyte have in common

A

Contain same amount of genetic info

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21
Q

Microscopic view of fertilisation

A
22
Q

Stages prior to formation of morula

A
23
Q

Relations between embryoblast, blastocyst and trophoblast

A
24
Q

What happens at implantation

A

Trophoblast differentiates into outer syncytiotrophoblast & inner cytotrophoblast

Uterine stroma decidual response

25
Q

What does success of implantation require

A

Trophoblast penetration of several tissue components to reach maternal blood supply

  • Epithelial lining of the uterus
  • Basal lamina
  • Underlying stroma

sequence of events resembles invasion of malignant tumours

26
Q

MOA in order to achieve implantation

A
  • Invasive cells must attach to ECM proteins
  • Secrete proteases capable of degrading these proteins and migrate through the degraded ECM
  • During implantation and subsequent placentation in the human, populations of trophoblast cells invade the endometrium and maternal vasculature within the uterus
  • Once reaching spiral arteries within the myometrium, trophoblast invasiveness ceases
27
Q

How does trophoblast invasion differ from tumour cells

A

Tumour cells exhibit uncontrolled invasion

Trophoblast invasion is tightly regulated

28
Q

Events leading to pre-eclampsia and intrauterine growth retardation

A

Sub-optimal trophoblast invasion

29
Q

Overview of menstrual cycle

A
30
Q

How does the corpus luteum protect itself

A

HCG (human chorionic gonadotrophin) - 1st text to mother

after that placenta produces progesterone

31
Q

Structure formed at day 7.5

A
32
Q

What has formed at the end of the 2nd week

A

Uteroplacental circulation

33
Q

Structure at day 9

A
34
Q

Structure at day 12

What is significant about this day

A

Embryo makes contact with mother’s blood supply

35
Q

Structure at day 13

A

Primary villi are sticking into trophoblast

36
Q

Where might hatching occur

A
37
Q

What are ectopic pregnancies

A
38
Q

Structure at the end of the 3rd week

A

Getting set up for embryonic circulatory system

Some of the cytotrophoblast extends all the way out to provide anchorage

39
Q

What constitutes the major foetal component of the placenta

Describe its composition

A

Chorionic villi

Consist of a mesenchymal core containing matrix, cells and foetal BVs

40
Q

Describe the chorionic villi during the first trimester

A

Villi are covered by the 2 layered epithelium of trophoblast - cyncytiotrophoblast (multi-nucleated, bathed in maternal blood) and cytotrophoblast (cellular, non-invasive, villous)

41
Q

Describe the cytotrophoblast

A

Cellular, non-invasive, villous

42
Q

Describe the syncytiotrophoblast

A

Multinucleated, bathed in maternal blood

OUTER layer

43
Q

How does the haemochorial placenta change as gestation continues

A

Cytotrophoblast becomes discontinuous and syncytiotrophoblast becomes thinner

Nutrients from maternal blood are transported across compartments to reach foetal vessels

44
Q

What are anchoring villi

A

Some chorionic villi FREE others attached to decidua at the site of invasion - respiratory and absorptive - lungs & gut

At these sites villous cytotrophoblast cells proliferate and break through the syncytiotrophoblast to form cytotrophoblast columns and invade the decidua basalis

45
Q

What cells augment vessel walls

A

Some extravillous cytotrophoblast cells also invade uterine spiral arteries becoming endovascular trophoblast

46
Q

Decidua basalis

A

Decidualised endometrial cells and several kinds of immune cells including macrophages and large granular lymphocytes

47
Q

Structure of haemochorial placenta

A
48
Q

Placental blood supply

A
49
Q

Changes in blood supply between 4 weeks and 4 months

A
50
Q

Structures seen during gestation

A
51
Q

What lies beneath the decidua basalis

A

GGE (33 decks)

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