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BMS > Human Embryogenesis: Weeks 1-3 of Prenatal Development > Flashcards

Human Embryogenesis: Weeks 1-3 of Prenatal Development Flashcards

1
Q

The embryogenesis and embryonic period occurs from

A

Week 1-8

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2
Q

The fetal period occurs from

A

Wee 9-38

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3
Q

At the center of the 28 day menstrual cycle and its phases

A

Ovulation

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4
Q

The ovulated oocyte is surrounded by a shell with

A

Layers

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5
Q

Spermatozoa are conditioned in the female tract to be able to fertilize the oocyte. This is called

-sperm that do not undergo are unable to fertilize

A

Capacitation

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6
Q

Fertilization occurs where the oocyte and capacitted sperm meet, which is in the

A

Ampulla of uterine tube

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7
Q

Sperm can live in the female tract for several days, but an oocyte that is not fertilized degenerates within

A

24 hours of ovulation

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8
Q

Implantation of the early embryo is during endometrial secretory phase. If pregnancy occurs, the corpus luteum is maintained for a period by

A

Human chorionic gonadotropin (hCG)

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9
Q

Secreted by trophoblasts of the placenta

A

hCG

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10
Q

What are the three “shell” layers of the oocyte?

A
  1. ) Corona Radiata (outer)
  2. ) Zona Pellucida
  3. ) Plasma membrane (inner layer)
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11
Q

Outer crown of follicular cells around oocyte

-has chemoattractants for sperm

A

Corona Radiata (cumulus oophorus)

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12
Q

What are the functions of the corona radiata?

A

Provides protection, energy, and support for oocyte

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13
Q

Intermediate glycoprotein layer made up of “zona proteins” (ZP)

A

Zona Pellucida

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14
Q

The zona protein ZP3 binds

A

Sperm

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15
Q

Sperm are modified by secretions in the female tract.
These modifications take several hours and make up
a mandatory “ripening” process for fertilization called

A

Capacitation

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16
Q

Removed at the tip of the sperm head during capacitation to make the membrane overlying the acrosome more fluid for enzyme release during fertilization

A

Glycoproteins and Plasma Proteins

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17
Q

Become hyper-active during capacitation

A

Sperm tails

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18
Q

What are the three phases of fertilization?

A
  1. ) Penetration of corona radiata
  2. ) Penetration of zona pellucida
  3. ) Plasma membrane fusion
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19
Q

Capacitated sperm penetrate the corona radiata via the

-only 300 of the 300 million sperm ejaculated penetrate the corona radiata

A

Whipping sperm tail

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20
Q

In phase 2, sperm heads bind to the ZP3 receptors in the zona pellucida and release acrosomal enzymes that allow

A

Penetration of zona pellucida

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21
Q

In phase 3, the sperm and oocytes plasma membranes fuse. The oocyte completes meiosis II and the female gamete (ovum) and male gamete (sperm) fuse their haploid pronuclei to form a

A

Diploid zygote

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22
Q

What happens to the oocyte plasma membrane upon sperm contact?

A

It depolarizes

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23
Q

Intracellular Ca2+ tsunami that induces the cortical reaction

-prevents polyspermy (more than one sperm binding)

A

Oocyte PM depolarization

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24
Q

At the initiation of cleavage, the zygote is metabolically activated and will soon mitotically divide into

A

2 cells

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25
Q

Two oocytes are simultaneously ovulated and each is fertilized by separate sperm

-70% of all twins

A

Dizygotic twins (DZ)

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26
Q

A single zygote is fertilized by a single sperm and splits into 2 zygotes within the 1st week after fertilization

-30% of all twins

A

Monozygotic Twins

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27
Q

A series of symmetrical mitotic divisions during week 1

A

Cleavage

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28
Q

Cleavage divisions occur approximately 20 hours apart and results in

A

Blastomeres

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29
Q

Daughter cells which are smaller w/ each successive division and are encased by the zona pellucida in the early embryo

A

Blastomeres

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30
Q

Cleavage continues and blatomeres up through the 8-cell stage are

-can give rise to all embryonic and extraembryonic tissues

A

Totipotent

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31
Q

Beyond the 8 cell stage, cells become more differentiated and are committed to being a

A

Particular cell type

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32
Q

By day 4, the 32-cell morula (“mulberry”) is a solid ball of compacted cells migrating in the uterine tube toward the

A

Uterus

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33
Q

The cells of the morula segregate and begin to establish polarity. What is the:

  1. ) Inner cell mass (ICM)
  2. ) Outer cell mass (OCM)
A
  1. ) Embryoblast

2. ) Trophoblast

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34
Q

Fluid from the uterine cavity penetrates the zona pellucida to surround cells of the morula’s embryoblast/ICM. By 4.5 days after fertilization, the penetrating fluid pools and forms the

A

Blastocyst cavity of the blastocyst

35
Q

Embryoblast/ICM cells can give rise to any/all embryonic cells, meaning they are

A

Pluripotent

36
Q

Pluripotent embryoblast/ICM cells have great clinical potential as

A

Embryonic stem cells

37
Q

Occurs 6 days after fertilization during the secretory phase of the endometrium (day 20 of 28 day cycle)

A

Blastocyst Implantation

38
Q

Secrete enzymes that degrade the zona pellucida, allowing the blastocyst to hatch through the zona pellucida on day 5

A

Trophoblasts

39
Q

Drive blastocyst implantation

-located at embryonic pole of the blastocyst

A

Trophoblasts

40
Q

Trohphoblasts at the embryonic pole of the blastocyst embed into the uterine wall and eventually form fetal components of

A

Placenta

41
Q

Induces the corpus luteum to continue secretion of progesterone for endometrium maintenance

-Secreted by trophoblasts

A

Human Chorionic Gonadotropin (hCG)

42
Q

With implantation, the pregnant uterine endometrium undergoes a

A

Decidua reaction

43
Q

The blastocyst normally implnts on the anterior or posterior unterine body wall. In 2% of pregnancies, implantation occurs elsewhere. This is called

A

Ectopic pregnancy

44
Q

95% of ectopic pregnancies occur in the

A

Uterine Tube

45
Q

A busy time for cleavage and segregation of blastomeres before implantation in the uterine endometrium

A

Week 1

46
Q

A busy time for trophoblasts , hypoblasts, and amnioblasts in forming extraembryonic support

A

Week 2

47
Q

The ebryoblast forms the 2-layered/bilaminar disc during

A

Week 2

48
Q

Embyoblast differentiation forms the

A

Bilaminar embryonic disc

49
Q

What are four extraembryonic structures developed during week 2?

A
  1. ) Amniotic Cavity
  2. ) Yolk sac
  3. ) Connecting Stalk
  4. ) Fetal part of placenta
50
Q

Differentiate into cells of the embryo proper and amnioblasts

A

Epiblasts

51
Q

Is located dorsal to the bilaminar disc, but expands

A

Amniotic cavity

52
Q

What are three components of amniotic fluid?

A
  1. ) Fetal urine
  2. ) Oligohydraminos
  3. ) Polyhydraminos
53
Q

Proliferate and migrate to line the inner trophoblast surface of the blastocyst cavity, which becomes the yolk sac

A

Hypoblasts

54
Q

Located ventral to the bilaminar disc, and eventually regresses

A

Yolk sac

55
Q

The location of early exchange, early hematopoiesis, and germ cell conversion to gonads

A

Yolk sac

56
Q

Hypoblasts give rise to which two things?

A
  1. ) Yolk sac

2. ) Connecting Stalk

57
Q

Becomes the umbilical cord and connects the embryo/fetus to the placenta

A

Connecting stalk

58
Q

Develops from the trophoblast-altered endometrium

A

Maternal placenta

59
Q

A composite organ that facilitates nutrient and gas exchange between the maternal and fetal compartments

A

Placenta

60
Q

What is the:

  1. ) Fetal part of placenta
  2. ) Maternal part of placenta
A
  1. ) Chorion fondosum (trophoblasts & hypoblasts)

2. ) Decidua basalis (uterine endometrium)

61
Q

In fetal blood, moves to the placenta from the umbilical arteries

A

Waste

62
Q

In fetal blood, moves from the placenta to the umbilical vein

A

Nutrients

63
Q

In maternal blood, nutrients move to the placenta from

A

Spiral arteries

64
Q

In maternal blood, waste moves from the placenta to the

A

Uterine veins

65
Q

There is waste-nutrient exchange and separation (no mixture) of fetal and maternal blood at the

A

Thin placental barrier

66
Q

A busy time for epiblasts in formation of intraembryonic germ layers

A

Week 3

67
Q

In week 3, the epiblast of the bilaminar embryo forms the 3-layered/trilaminar disc in a process called

A

Gastrulation

68
Q

Epiblast cells migrate to the primitive streak where they detach and invaginate (dive down ventrally) through the primitive streak during

A

Gastrulation

69
Q

The three primary germ layersof the trilaminar embryo are the

-originate from epiblast

A

Ectoderm, mesoderm, and endoderm

70
Q

The process of forming the endoderm, mesoderm, and ectoderm

A

Gastrulation

71
Q

Epiblast cells that intercalate among hypoblast cells displace and completely replace hypoblast cells to form the

A

Endoderm

72
Q

Epiblast cells settle between the endoderm and epiblast to form the intraembryonic

A

Mesoderm

73
Q

Epiblast cells that remain behind then become the

A

Ectoderm

74
Q

Polarity (i.e. dorsal-ventral, right-left, cranial-caudal) is established during

A

Gastrulation

75
Q

Becomes structures that communicate with the external environment

-i.e. nervous system, epidermis, and sensory receptors

A

Ectoderm

76
Q

Becomes a component of support through muscles and connective tissues

-i.e. skeletal, muscular, urogenital, and cardiovascular

A

Mesoderm

77
Q

Functions in digesting, breathing, and secreting

-i.e. epithelia of urinary bladder and GI-respiratory systems

A

Endoderm

78
Q

Organs are derived from more than one

A

Germ layer

79
Q

What are the two sites in the embryo where the ectoderm and endoderm adhere tightly together without migration of intervening mesoderm?

A

Buccopharyngeal membrane and cloacal membrane

80
Q

Lies at the cranial end of the embryo as the future location of the oral cavity

A

Buccopharyngeal membrane

81
Q

Lies at the caudal end of the embryo as the future location of the anus

A

Cloacal membrane

82
Q

The primitive streak regresses by the end of the 3rd week with the formation of the

A

Notochord

83
Q

Form when the primitive streak fails to completely regress and contain multiple tissue types derived from the pluripotent epiblast cells

A

Teratomas

BMS (62 decks)

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