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Foundation of Medicine > Fertilisation to Trilaminar embryo > Flashcards

Fertilisation to Trilaminar embryo Flashcards

1
Q

What happens in fertilisation (4 stages)

A

1) Sperm binds in a human specific interaction with the zona pellucida glycoprotein (ZP3)

2) Acrosomal enzymes released from sperm head; the sperm digests its way into egg.

3) Egg and sperm plasma membrane fuse and sperm contents enter the egg

4) Sperm entry triggers:
- completion of meiosis 2
- release of cortical granules by oocyte

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2
Q

Where does fertilisation occur

A

Ampulla of uterine tubes

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3
Q

What is cleavage- first cell division

A

Zygote undergoes series of mitotic divisions which subdivides fertilised egg into many smaller daughter cells called blastomeres

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4
Q

what are blastomeres with up to 8 cells classed as

A

totipotent- capable of giving rise to any cell type

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5
Q

What is mosaicism

A

Individuals with 2 or more cell line with different chromosome complements

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6
Q

What is a morula

A

16+ blastomeres (smaller daughter cells)

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7
Q

What is compaction of morula

A

Cells confined within zona pellucida
so to maximise space cells come closer in contact with each other begin to form cell junctions

Outer cells in contact with zona pellucida form extensive gap junctions and fluid enters through zona pellucida

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8
Q

What is zona pellucida

A

the thick transparent membrane surrounding a mammalian ovum before implantation

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9
Q

What is in a blastocyst (when is it formed)

A

Trophoblast
Zona pellucida
Inner cell mass
Blastocyst cavity
(Morula becomes the blastocyst)

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10
Q

What happens when blastocyst hatches

A

Embryo interacts directly with endothelial lining of the uterus for implantation,
Zona pellucida was removed before implantation

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11
Q

What day and where does implantation occur

A

Typically on day 6 on posterior anterior uterine wall

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12
Q

What is corpus luteum

A

Produces progesterone which is essential in maintaining endometrium for embryo to survive

Stimulated by hCG - hormone for pregnancy tests

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13
Q

on what day does bilaminar embryo (2 germ layers) form

A

day 7.5 when embryo organises itself into 2 cell layers : Epiblast (dorsal) and Hypoblast (ventral)

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14
Q

What drives active process creating bilaminar embryo

A

Trophoblast

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15
Q

What is trophoblast

A

Divided into cytotrophoblast and syncytiotrophoblast

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16
Q

What 2 cavities form on day 9 of bilaminar embryo formation

A

Amniotic cavity (Epiblast)
Primitive yolk sac (Hypoblast)

17
Q

What cavity forms on day 12 of bilaminar embryo development

A

Chorionic cavity

-Formed when extraembryonic mesoderm develops & degenerates

18
Q

What do some cells do to form definitive (secondary) yolk sac on day 13 of bilaminar embryo development

A

Hypoblast cells migrate

19
Q

What is ectopic pregnancy

A

Implantation outside the uterus which is dangerous and life threatening

20
Q

What abnormal sites can ectopic pregnancies implant

A

Ovaries
Uterine tube
Peritoneum (abdominal cavity

21
Q

Where does the primitive streak appear in week 3

A

midline at caudal end of epiblast

22
Q

What is the cranial end of primitive streak

A

Primitive pit and node

23
Q

Why is primitive streak involved in gastrulation

A

Movement of epiblast cells through primitive streak to form 3 germ layers

24
Q

What do hypoblast cells get replaced by

A

Definitive endoderm = germ layer

25
Q

What are the 3 germ layers of TRILAMINAR embryo

A

Ectoderm (outermost)
Mesoderm
Endoderm (innermost)

26
Q

what is derived from ectoderm

A

Epidermis of skin
(hair, nails, associated glands)

Nervous system
(brain, spinal cord, peripheral nerves)

27
Q

What 3 regions is mesoderm divided into either side of notochord

A

Paraxial mesoderm
Intermediate mesoderm
Lateral plate mesoderm (2 parts Somatic and Visceral)

28
Q

What is the fate of paraxial mesoderm

A

Axial Skeleton
Voluntary skeletal muscles
Part of dermis (back)

29
Q

what is the fate of intermediate mesoderm

A

Urogenital systems
e.g. Kidneys & ureter
Gonads & associated structures

30
Q

What is the fate of lateral plate mesoderm- somatic part

A

Most of dermis (back)
Lining of body wall
Parts of limbs

31
Q

What is the fate of lateral plate mesoderm- visceral part

A

Cardiovascular system
Mesothelial organ coverings
Smooth muscle

32
Q

What is derived from Endoderm

A

Lining of gut tube, respiratory tract, bladder and urethra

Foundation of Medicine (23 decks)

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