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Foundations of Medicine > Fertilisation to trilaminar > Flashcards

Fertilisation to trilaminar Flashcards

1
Q

What does the sperm bind with on the surface of the egg?

A

The zona pellucida glycoprotein (ZP3)

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2
Q

How does the sperm enter the egg?

A

It releases acrosomal enzymes from the acrosome of the sperm head

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3
Q

How does the egg cell prevent polyspermy?

A

Sperm penetration causes cortical granules in the cytoplasm to release their contents which hardens the zone pellucida

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4
Q

What does sperm entry trigger in the egg cell?

A

Completion of meiosis 2
Release of cortical granules by oocyte

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5
Q

What occurs when the sperm and egg bind?

A

The sperm contents enter the egg

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6
Q

Where does fertilisation occur within the uterine tube?

A

Ampulla

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7
Q

What is the name given to the smaller daughter cells of the fertilised egg?

A

Blastomeres

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8
Q

What happens to the overall size of the ovum during mitosis?

A

It stays the same

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9
Q

What is the definition of totipotent?

A

Can differentiate to form any type of adult cell, as well as embryonic and placental cell. Blastomeres up to the 8 cell stage are thought to be totipotent

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10
Q

What is mosaicism?

A

When non-disjunction occurs during the first cell division, not during gametogenesis, so only some cells contain the increased number of cells. In trisomy 21, this leads to less prominent features

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11
Q

What is meant by a morula?

A

When the ovum contains 16 or more blastomeres

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12
Q

What occurs during compaction of the morula?

A

Blastomeres come into closer contact and form cell junctions, outer cells that are in contact with the zone pellucida form extensive gap junctions

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13
Q

How many cells are in a blastocyst?

A

70-100

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14
Q

What are the 4 regions of a blastocyst?

A

Trophoblast layer
Inner cell mass
Blastocyst cavity
Zona pellucida

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15
Q

What does the trophoblast layer form?

A

The placenta

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16
Q

What does the inner cell mass form?

A

Embryo

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17
Q

What occurs during hatching?

A

Trophoblasts release enzymes that begin to break down the zone pellucida. Embryonic contractions allow for hatching as the zone pellucida is released

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18
Q

In what does the ovum mature?

A

A preovulatory follicle

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19
Q

What happens to the preovulatory follicle after ovulation?

A

It forms a corpus luteum, a temporary gland that secretes progesterone, maintaining the thick endometrial lining for implantation

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20
Q

What are the 2 layers formed from the trophoblast layer?

A

Cytotrophoblast
Syncytiotrophoblast

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21
Q

What forms the syncytiotrophoblast?

A

A single, multinucleate cell

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22
Q

What hormone does the syncytiotrophoblast form?

A

Human chorionic gonadotrophin

23
Q

What is the function of Human chorionic gonadotrophin?

A

Stimulates the corpus luteum to thicken the endometrial lining and is the basis of pregnancy tests

24
Q

What 2 layers does the embryo split into?

A

Epiblast
Hypoblast

25
Q

What surface of the embryo is the epiblast?

A

Dorsal surface

26
Q

What surface of the embryo is the hypoblast?

A

Ventral surface

27
Q

On what day does the bilaminar embryo form?

A

Day 7.5

28
Q

What 2 cavities form on day 9?

A

Amniotic cavity from the epiblast
Primitive yolk sac (Exocoelomic cavity) from the hypoblast

29
Q

What occurs in the syncytiotrophoblast on day 9?

A

Vacuoles appear and unite to form lacunae

30
Q

What closes the site of embryonic implantation of the endometrium?

A

A fibrin coagulum

31
Q

What is the name of the hypoblast membrane that surrounds the yolk sac?

A

Exocoelomic (Heuser) membrane

32
Q

What fills the trophoblastic lacunae on day 12?

A

Maternal sinusoids formed from nearby capillaries pass blood into the trophoblastic lacunae, establishing a uteroplacental circulation

33
Q

What layer forms around the exocoelomic membrane?

A

Extraembryonic mesoderm

34
Q

What are the 3 components of the extra embryonic mesoderm?

A

Extraembryonic somatic mesoderm (Outer)
Extraembryonic splanchnic mesoderm (Inner)
Extraembryonic cavities

35
Q

What happens to the embryonic mesoderm on day 13?

A

The extraembryonic splanchnic mesoderm degenerates to form the chorionic cavity

36
Q

What structure forms to connect the embryo and trophoblast layer?

A

Connecting stalk

37
Q

What is the exocoelomic cyst?

A

The remnants of the primary yolk sac, found in the chorionic membrane. A secondary yolk sac forms within the embryo

38
Q

During what week does the primitive streak form?

A

Week 3

39
Q

What are the 3 parts of the primitive streak?

A

Primitive pit at the cranial end
Primitive node at the cranial end
Primitive groove at the caudal end

40
Q

What is established by the formation of the primitive streak?

A

The body axes

41
Q

What occurs during the first stage of gastrulation?

A

Epiblast cells move through the primitive streak and replace the hypoblast layer with a definitive endoderm layer

42
Q

What occurs during the second layer of gastrulation?

A

More epiblast cells move in through the primitive streak and move in-between the epiblast layer and definitive endoderm to form three layers

43
Q

What are the 3 layers of the trimlaminar embryo?

A

Ectoderm
Mesoderm
Endoderm

44
Q

What 2 membranes form on the trilaminar embryo?

A

Oropharyngeal membrane (Cranial end)
Cloacal membrane (Caudal end)

45
Q

What structures form from the ectoderm?

A

Epidermis of the skin, hair, nails and associated glands
Nervous system; brain, spinal chord and peripheral nerves

46
Q

what are the 3 regions of the mesoderm?

A

Paraxial mesoderm
Intermediate mesoderm
Lateral plate mesoderm

47
Q

What are the 2 layers of the lateral plate mesoderm?

A

Somatic layer
Visceral layer

48
Q

What is the notochord?

A

A flexible, rod-like structure that forms from mesodermal cells that forms the spinal chord in vertebrates

49
Q

What structures form from the paraxial mesoderm?

A

Axial skeleton, skeletal muscle and parts of the dermis of the back

50
Q

What structures form from the intermediate mesoderm?

A

Urogenital systems; kidney, ureter, gonads and associated structures

51
Q

What structures form from the somatic layer of the lateral plate mesoderm?

A

Most of the dermis, lining of body wall and parts of limbs

52
Q

What structures form from the visceral layer of the lateral plate mesoderm?

A

Cardiovascular system, mesothelial covering of organs and smooth muscle

53
Q

What structures form from the endoderm?

A

Lining of the gut tube
Lining of the respiratory tract
Lining of the bladder and urethra

Foundations of Medicine (56 decks)

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