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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

22
Q

Stages prior to formation of morula

23
Q

Relations between embryoblast, blastocyst and trophoblast

24
Q

What happens at implantation

A

Trophoblast differentiates into outer syncytiotrophoblast & inner cytotrophoblast

Uterine stroma decidual response

25
What does success of implantation require
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
MOA in order to achieve implantation
* 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
How does trophoblast invasion differ from tumour cells
Tumour cells exhibit uncontrolled invasion Trophoblast invasion is tightly regulated
28
Events leading to pre-eclampsia and intrauterine growth retardation
Sub-optimal trophoblast invasion
29
Overview of menstrual cycle
30
How does the corpus luteum protect itself
HCG (human chorionic gonadotrophin) - 1st text to mother after that placenta produces progesterone
31
Structure formed at day 7.5
32
What has formed at the end of the 2nd week
Uteroplacental circulation
33
Structure at day 9
34
Structure at day 12 What is significant about this day
Embryo makes contact with mother's blood supply
35
Structure at day 13
Primary villi are sticking into trophoblast
36
Where might hatching occur
37
What are ectopic pregnancies
38
Structure at the end of the 3rd week
Getting set up for embryonic circulatory system Some of the cytotrophoblast extends all the way out to provide anchorage
39
What constitutes the major foetal component of the placenta Describe its composition
Chorionic villi Consist of a mesenchymal core containing matrix, cells and foetal BVs
40
Describe the chorionic villi during the first trimester
Villi are covered by the 2 layered epithelium of trophoblast - cyncytiotrophoblast (multi-nucleated, bathed in maternal blood) and cytotrophoblast (cellular, non-invasive, villous)
41
Describe the cytotrophoblast
Cellular, non-invasive, villous
42
Describe the syncytiotrophoblast
Multinucleated, bathed in maternal blood OUTER layer
43
How does the haemochorial placenta change as gestation continues
Cytotrophoblast becomes discontinuous and syncytiotrophoblast becomes thinner Nutrients from maternal blood are transported across compartments to reach foetal vessels
44
What are anchoring villi
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
What cells augment vessel walls
Some extravillous cytotrophoblast cells also invade uterine spiral arteries becoming endovascular trophoblast
46
Decidua basalis
Decidualised endometrial cells and several kinds of immune cells including macrophages and large granular lymphocytes
47
Structure of haemochorial placenta
48
Placental blood supply
49
Changes in blood supply between 4 weeks and 4 months
50
Structures seen during gestation
51
What lies beneath the decidua basalis

GGE (33 decks)

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