Human Embryogenesis: Weeks 1-3 of Prenatal Development Flashcards Preview

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Flashcards in Human Embryogenesis: Weeks 1-3 of Prenatal Development Deck (83):
1

The embryogenesis and embryonic period occurs from

Week 1-8

2

The fetal period occurs from

Wee 9-38

3

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

Ovulation

4

The ovulated oocyte is surrounded by a shell with

Layers

5

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

Capacitation

6

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

Ampulla of uterine tube

7

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

24 hours of ovulation

8

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

Human chorionic gonadotropin (hCG)

9

Secreted by trophoblasts of the placenta

hCG

10

What are the three "shell" layers of the oocyte?

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

11

Outer crown of follicular cells around oocyte

-has chemoattractants for sperm

Corona Radiata (cumulus oophorus)

12

What are the functions of the corona radiata?

Provides protection, energy, and support for oocyte

13

Intermediate glycoprotein layer made up of "zona proteins" (ZP)

Zona Pellucida

14

The zona protein ZP3 binds

Sperm

15

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

Capacitation

16

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

Glycoproteins and Plasma Proteins

17

Become hyper-active during capacitation

Sperm tails

18

What are the three phases of fertilization?

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

19

Capacitated sperm penetrate the corona radiata via the

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

Whipping sperm tail

20

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

Penetration of zona pellucida

21

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

Diploid zygote

22

What happens to the oocyte plasma membrane upon sperm contact?

It depolarizes

23

Intracellular Ca2+ tsunami that induces the cortical reaction

-prevents polyspermy (more than one sperm binding)

Oocyte PM depolarization

24

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

2 cells

25

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

-70% of all twins

Dizygotic twins (DZ)

26

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

-30% of all twins

Monozygotic Twins

27

A series of symmetrical mitotic divisions during week 1

Cleavage

28

Cleavage divisions occur approximately 20 hours apart and results in

Blastomeres

29

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

Blastomeres

30

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

-can give rise to all embryonic and extraembryonic tissues

Totipotent

31

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

Particular cell type

32

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

Uterus

33

The cells of the morula segregate and begin to establish polarity. What is the:
1.) Inner cell mass (ICM)
2.) Outer cell mass (OCM)

1.) Embryoblast
2.) Trophoblast

34

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

Blastocyst cavity of the blastocyst

35

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

Pluripotent

36

Pluripotent embryoblast/ICM cells have great clinical potential as

Embryonic stem cells

37

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

Blastocyst Implantation

38

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

Trophoblasts

39

Drive blastocyst implantation

-located at embryonic pole of the blastocyst

Trophoblasts

40

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

Placenta

41

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

-Secreted by trophoblasts

Human Chorionic Gonadotropin (hCG)

42

With implantation, the pregnant uterine endometrium undergoes a

Decidua reaction

43

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

Ectopic pregnancy

44

95% of ectopic pregnancies occur in the

Uterine Tube

45

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

Week 1

46

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

Week 2

47

The ebryoblast forms the 2-layered/bilaminar disc during

Week 2

48

Embyoblast differentiation forms the

Bilaminar embryonic disc

49

What are four extraembryonic structures developed during week 2?

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

50

Differentiate into cells of the embryo proper and amnioblasts

Epiblasts

51

Is located dorsal to the bilaminar disc, but expands

Amniotic cavity

52

What are three components of amniotic fluid?

1.) Fetal urine
2.) Oligohydraminos
3.) Polyhydraminos

53

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

Hypoblasts

54

Located ventral to the bilaminar disc, and eventually regresses

Yolk sac

55

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

Yolk sac

56

Hypoblasts give rise to which two things?

1.) Yolk sac
2.) Connecting Stalk

57

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

Connecting stalk

58

Develops from the trophoblast-altered endometrium

Maternal placenta

59

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

Placenta

60

What is the:
1.) Fetal part of placenta
2.) Maternal part of placenta

1.) Chorion fondosum (trophoblasts & hypoblasts)
2.) Decidua basalis (uterine endometrium)

61

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

Waste

62

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

Nutrients

63

In maternal blood, nutrients move to the placenta from

Spiral arteries

64

In maternal blood, waste moves from the placenta to the

Uterine veins

65

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

Thin placental barrier

66

A busy time for epiblasts in formation of intraembryonic germ layers

Week 3

67

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

Gastrulation

68

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

Gastrulation

69

The three primary germ layersof the trilaminar embryo are the

-originate from epiblast

Ectoderm, mesoderm, and endoderm

70

The process of forming the endoderm, mesoderm, and ectoderm

Gastrulation

71

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

Endoderm

72

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

Mesoderm

73

Epiblast cells that remain behind then become the

Ectoderm

74

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

Gastrulation

75

Becomes structures that communicate with the external environment

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

Ectoderm

76

Becomes a component of support through muscles and connective tissues

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

Mesoderm

77

Functions in digesting, breathing, and secreting

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

Endoderm

78

Organs are derived from more than one

Germ layer

79

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

Buccopharyngeal membrane and cloacal membrane

80

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

Buccopharyngeal membrane

81

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

Cloacal membrane

82

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

Notochord

83

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

Teratomas

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