Fertilisation to Trilaminar Flashcards

1
Q

fertilisation:

A

union of gametes - fusion of sperm and oocyte to form a zygote

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2
Q

where does fertilisation take place

A

in the ampulla of the uterine tube

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3
Q

in the firsts stage of fertilisation the Sperm binds to the

A

zona pellucida glycoprotein (ZP3)

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4
Q

Acrosomal enzymes released from sperm head;

A

sperm digests its way into egg

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5
Q

Egg and sperm plasma membranes fuse and

A

sperm contents enters the egg

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6
Q

Sperm entry triggers completion of meiosis 2 and release of

A

cortical granules by oocyte (make ZP impenetrable to other sperm)

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7
Q

what does one cell embryo undergo

A

a series ofcleavage divisions

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8
Q

what’s a mitotic division

A

dividing into identical cells

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9
Q

what else happens during cleavage and why

A

Rapid mitotic division without increase in size

because cells are confined within the ZP the embryo will change shape(compaction)

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10
Q

what does cleavage form

A

morula(16+ cells) blastocyst(200-300 cells)

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11
Q

name one type of cell in a blastocyst and explain

A

Outer cell mass (trophoblast):contacts with the endometrium of the uterus to facilitate implantation and the formation of the placenta

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12
Q

name another type of cell in a blastocyst and explain

A

Inner cell mass (embryoblast):responsible for the formation of the embryo itself

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13
Q

how to cells maximise available space

A

by coming into closer contact with each other

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14
Q

Inner cells form

A

cell junctions

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15
Q

outer cells form

A

gap junctions

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16
Q

what signals the formation of theblastocyst

A

Fluid enters through ZP producing a blurred cell mass

17
Q

describe implantation

A

Embryo implants into endometrial lining on posterior or anterior uterine wall

18
Q

Ectopic pregnancy:

A

implantation outside the uterus

19
Q

Placenta previa:

A

placenta lies low in uterus and partially/completely covers cervix

20
Q

where does the Stella part of the placenta arise from

A

the trophoblast

21
Q

what day is implantation typically on

A

day 6

22
Q

what occurs in day 7.5

A
  • Trophoblast divides into cytotrophoblast (individual cells) and syncytioblast (single multinucleated cell which produces hCG)
  • Embryobast divides into epiblast (dorsal surface) and hypoblast (ventral surface)
  • Amniotic cavity begins to form
23
Q

what occurs during day 9

A
  • Formation of 2 cavities = amniotic cavity (epiblast) and primitive yolk sac (hypoblast)
  • Implantation complete and closure by fibrin coagulum
24
Q

what 2 cavities are formed (day 9)

A

amniotic cavity (epiblast) and primitive yolk sac (hypoblast)

25
Q

once you get to day 7.5 what period is this called

A

Development of the bilaminar embryo

26
Q

what occurs during day 12

A
  • Uteroplacental circulation established
  • Extraembryonic mesoderm develops then degenerates, forming chorionic cavity
27
Q

what occurs during day 13

A
  • Further development of chorionic cavity
  • Presence of existing stalk (later umbilical cord)
  • Second wave of hypoblast cells migrate to form definitive yolk sac
28
Q

what hormone is the basis for pregnancy tests

A

hCG

29
Q

what does then primitive streak set up

A

body axis - for the next process to begin (gastrulation)

30
Q

how are the 3 primary germ layers formed

A

nvagination of the epiblast cells through the primitive stream

31
Q

what are the 3 primary germ layers

A

ectoderm, mesoderm, endoderm (trilaminar embryo)

32
Q

where do you not get mesoderm formation

A

at the oropharyngeal

33
Q

what does ectoderm form

A
  • Epidermis of skin, hair, nails
  • Nervous system
34
Q

what does mesoderm do

A

separates itself into different regions:
- Paraxial mesoderm
- Intermediate mesoderm
- Lateral plate mesoderm

35
Q

what does Paraxial mesoderm form:

A

axial skeleton, skeletal muscle

36
Q

what does Intermediate mesoderm form:

A

urogenital systems

37
Q

what does Lateral plate mesoderm form

A

Somatic layer:dermis, lining of body wall, parts of limbs

Visceral layer:cardiovascular system, mesothelial covering of organs, smooth muscle

38
Q

endoderm

A
  • Lining of gut tube
  • Lining of respiratory tract
  • Lining of bladder and urethra