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MSK test one > Fertilization and Gastrulation > Flashcards

Fertilization and Gastrulation Flashcards

1
Q

What are the two kinds of calendars that measure human development?

A

Obstetrical/gestational calendar or ovulatory calendar

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2
Q

What is the obstetrical or gestational calendar? What does it start?

A

The first day of the calendar starts with the LNMP

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3
Q

What is the ovualtory calendar?

A

The calendar that measures from fertilization and ignores the first two weeks before this event

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4
Q

Corona radiata

A

follicular cells that cover the egg cell

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5
Q

Zona Pellucida

A

A mesh of glycoproteins that surround the perivitelline space and nucleus

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6
Q

Perivitelline space

A

The space that surrounds the nucleus of the egg cell. It will release granules when the cell is fertilized to prevent polyspermy

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7
Q

Head of the sperm cell

A

Contains both the acrosome and nucleus (nucleus contains 23x or 23y chromosomes)

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8
Q

Acrosome

A

Contains the proteins like, hyaluronidasem, esterases, acrosin and neuraminidase, to help the sperm penetrate the corona raditata and zona pellucida.

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9
Q

The tail of the sperm

A

Contains three sections the middle, principle and tail end. The middle piece contains mitochondria that are needed by the cell during migration to generate ATP.

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10
Q

What are the events that occur in the first week of human development?

A

Fertilization, cleavage, blastocyst forms, inner cell mass forms and then the beginning of implantation

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11
Q

Where does fertilization occur?

A

In the ampulla of a Fallopian tube

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12
Q

What is capacitation?

A

The removal of the glycoprotein coat and seminal plasma proteins from the plasma membrane of the sperm- this generally occurs in the uterus

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13
Q

What happens when sperm encounter the egg cell?

A

The acrosome will release hyaluronidase which will aid the sperm in getting through the corona radiata. This is a group effort of the sperm so when there is low sperm count, it may not be possible for a sperm cell to pass this point.

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14
Q

What occurs after the sperm cell makes it through the corona pellucida?

A

The first sperm cell will reach the zona pellucida and release esterases, acrosin and neuraminidase from the acrosome. This allows the sperm to penetrate the layer

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15
Q

What is the zona reaction?

A

How the egg cell prevents polyspermy. When the zona pellicuda is penetrated by one sperm cell, this area will undergo conformational changes that make it extremely rigid and will not allow for the passage of any other cells. The perivitelline space will also release granules at this time to prevent polyspermy.

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16
Q

What occurs after the penetration of the zona pellucida by a sperm cell?

A

The sperm cell PM and egg PM will fuse their plasma membranes and the head/tail of the sperm will enter the oocyte cytoplasm. IMPORTANT the male mitochondria will not enter the cytoplasm

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17
Q

Why is it significant that the mitochondria of the male do not enter the oocyte?

A

This means that the developing embryo will get its mitochondrial DNA from the mother. Allows for the maternal lineage to be traced

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18
Q

What occurs after the fusion of PM between the sperm and oocyte?

A

The oocyte will undergo second meiosis and the male will form a pronucleus. The two nuclei will fuse and this will form the zygote.

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19
Q

What are the results of fertilization?

A

Completion of 2nd meiotic division, a diploid organism formed, metabolic activation of oocyte and initiation of cleavage

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20
Q

When does cleavage begin after fertilization?

A

Approximately 30 hours

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21
Q

What is the morulla and about what day does it form?

A

Cells are going through cleavage and when they reach about day 3 they are 12-32 cells that are contained in the zona pellucida still. The morulla enters the uterus from here.

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22
Q

How does the blastocyst form and on what days?

A

The morulla enters the uterus where it will fill with uterine fluid. This creates a cavity in the morulla and the development of an early blastocyst. The zona pellucida begins to degrade about day 5 and the inner mass forms with trophopblast surrounding it. By day 7 the late blastocyst has formed

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23
Q

What is the late blastocyst and what day does it form?

A

It contains an inner mass that is one layer thick and is the developing embryo. This is surrounded by trophoblast cells that will give rise to the placenta.

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24
Q

What are some of the assisted reproductive techniques?

A

In vitro fertilization/embryo transfer, cryopreservation of embryos and intracytoplasmic sperm injection

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25
Q

What is in vitro fertilization/embryo transfer?

A

The ovary of a female is stimulated to release eggs. These eggs are then collected and fertilized with sperm in a controlled environment. Here the cells will undergo cleavage to the blastocyst formation. The blastocyst is then implanted into the uterus.

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26
Q

What does the trophoblast do after the first week of fertilization?

A

It will release early pregnancy factors to signal the body that the forming embryo is not an invader. Allows for implantation of blastocyst.

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27
Q

What cells do the trophoblast give rise to?

A

The Cytotrophoblast and Syncytiotrophoblast

28
Q

What is the cytotrophoblast and its function?

A

Cells derived from the trophoblast of the blastocyst. These cells act as the stem cells and are mitotically active.

29
Q

What is the Syncytiotrophoblast?

A

Cells derived from the trophoblast of the blastocyst. They are multinucleated cells that help with the implantation of the blastocyst. The produce proteolytic enzymes for degrading the endometrial tissues of the uterus.

30
Q

What is hCG and what cells produce it?

A

Human chorionic gonadotropin produced by the Syncytiotrophoblast. This signals to the female body that she is pregnant.

31
Q

What is a hydatidiform mole?

A

Abnormal trophoblastic proliferation and excess hCG produced. This is the product of an unviable blastocyst that implanted into the uterine wall. Can be the result of a complete mole or partial mole formation.

32
Q

What is a complete mole?

A

The fertilization of an empty oocyte followed by the duplication of the male genome. So the blastocyst will contain a double copy of the male DNA. OR by an empty oocyte by two sperm.

33
Q

What is a partial mole?

A

The fertilization of a normal oocyte by two sperm

34
Q

What is the clinical presentation of a hydatidiform mole?

A

Elevated hCG, vaginal bleeding, pelvic pressure, enlarged uterus and hyperemesis

35
Q

What can hydatidiform moles lead to?

A

Choriocarcinomas

36
Q

What is a choriocarcinoma?

A

A malignant tumor that forms after a hydatidiform mole forms. These cells will migrate to the liver, lungs, vagina, intestine, brain and bone

37
Q

What occurs during week two of fertilization?

A

The embryo will form into a bilaminar disk composed of epiblast and hypoblast

38
Q

What is the epiblast?

A

One of the layers of the bilaminar disk of the embryo in week two. These cells give rise to the ectoderm of the embryo and the amnion.

39
Q

What is the hypoblast?

A

One of the layers of the bilaminar disk of the embryo in week 2. These cells will be replaced by other cells in week 3 so only present during this time.

40
Q

What does the hypoblast give rise to?

A

It will be the site of the endoderm but is extraembryonic(will not be incorporated to the embryo), it is the primary/secondary yolk sac and extraembryonic mesoderm

41
Q

How does the yolk sac form?

A

hypoblast in week two will proliferate out and form the primary yolk sac. Part of this will pinch off and the secondary yolk sac forms.

42
Q

What is the extraembryonic mesoderm?

A

A placeholder till the mesoderm forms. Consist of three parts. The coelom, somatic mesoderm and splanchnic mesoderm.

43
Q

What is the extraembryonic coelom?

A

The hollow cavity that surrounds the embryo

44
Q

what is the extraembryonic somatic mesoderm?

A

The cells that line the trophoblast and the amnion- will form the umbilical cord or the connecting stalk.

45
Q

What is the extraembryonic splanchnic mesoderm?

A

The cells that line the yolk sac

46
Q

What is previa?

A

When the blastocyst implanted at the os. Can be marginal, partial or complete. The placenta will form at the opening of the os and can lead to maternal hemorrhaging during pregnancy. Will generally correct it self, but if it does not then the baby must be delivered via c-section

47
Q

What is the process that occurs during week three of development?

A

Gastrulation

48
Q

What is Gastrulation?

A

The formation of the three germ layers

49
Q

What are the three germ layers?

A

Ectoderm, mesoderm and endoderm

50
Q

What does the ectoderm give rise to?

A

Skin, hair, nails, CNS and brain

51
Q

What does the mesoderm give rise to?

A

Connective tissue, muscle, bone, heart, spleen and blood

52
Q

What does the endoderm give rise to?

A

lungs, GI organs, bladder and the glands

53
Q

What is the primitive streak?

A

It is an invagination that occurs in the epiblast layer of the embryo

54
Q

What is the process of the formation of the primitive streak?

A

Cells in the epiblast will begin to proliferate and will migrate towards the center of the embryo where they will invaginate. These cells will the proliferate down and replace the cells of the hypoblast with true endoderm cells. The process continues and the next layer of true mesoderm is formed.

55
Q

What part of the developing embryo will become the diaphragm?

A

The septum transversum

56
Q

what part of the developing embryo will become the heart?

A

The cardio genie area

57
Q

What are the two areas that are fused ecto/endo derm?

A

The prechordal plate- future mouth

the cloacal membrane- future lower body openings

58
Q

The formation of the notocord

A

it is formed from the mesoderm- cells extend from the primitive knot anteriorly to the prechordal plate to form the notochord process. They will then fuse with the endoderm briefly to form the notochord plate. The cells then go back to their rounded structure in the mesoderm to form the notochord proper.

59
Q

what is the function of the notochord?

A

It is a template for the neural plate, enduces formation of the cns and provides longitudinal axis for embryo

60
Q

What is a sacrococcygeal teratoma?

A

Remant of the primitive streak- continued to proliferate and form all three germ layers

61
Q

What is a chordoma?

A

an aggregration of neoplasms of bone- arises from remnants of notochord- occurs in the axial skeleton

62
Q

what is the allantois?

A

made from the endoderm- template for the umbilical arteries and vein

63
Q

what does the mesoderm differentiate into?

A

paraxial mesoderm, intermediate mesoderm and lateral plate

64
Q

What does the paraxial mesoderm give rise to?

A

Somites- which are myotome, sclerotome and dermatome

65
Q

What does the intermediate mesoderm give rise to?

A

The urogential system like kidneys and gonads

66
Q

What does the lateral plate give rise to?

A

The connective tissue- including the blood, lymph, mesenteries and cardiovascular

67
Q

What are the two sections of the lateral plate?

A

Top layer by the ectoderm is the somatic layer

the bottom layer by the endoderm is the splanchnic layer

MSK test one (9 decks)

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