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BMS150 Midterm 2 > Embryology 1 - Fertilization to Gastrulation > Flashcards

Embryology 1 - Fertilization to Gastrulation Flashcards

1
Q

Female haploid gametes

A

oocytes

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2
Q

Where oocytes, progesterone, and estrogen are produced?

A

Ovaries

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3
Q

The site that receives oocyte from ovaries and where sperm fertilizes the oocyte?

A

Fallopian tube (in the ampulla)

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4
Q

Site where embryo, placenta, and membranes develop?

A

Uterus

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5
Q

When does crossing-over occur to mix the maternal and paternal chromatids (genes)?

A

Prophase 1

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6
Q

When is meiosis completed in an oocyte? When is fertilization completed?

A

When the sperm penetrates the oocyte; when spermatic pronucleus and oocyte pronucleus fuse => diploid cell (zygote) produced

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7
Q

Person with ovaries is born with a certain number of _______ oocytes that have been paused during the first stage of meiosis and do not continue until ______.

A

diploid; after puberty

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8
Q

Release of a secondary oocyte from the ovarian follicle

A

Ovulation

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9
Q

Ovulated secondary oocyte together with zona pellucida is externally covered in…?

A

Cumulus oophorus = granulosa cells that will rearrange and form corona radiata

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10
Q

What happens when sperm cells penetrate the zona pellucida?

A

Inject their genetic material into the oocyte

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11
Q

Why can’t double fertilization occur?

A

After a sperm cell penetrates the zona pellucida, it becomes impenetrable to other sperm cells

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12
Q

What reaction does contact with the zona pellucida trigger for the sperm cells?

A

Acrosome reaction = sperm secretes digestive enzymes that break down zona pellucida

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13
Q

Protein coat that surrounds an oocyte as well as the early embryo

A

Zona pellucida

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14
Q

Multicellular organism prior to fetal stage

A

Embryo

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15
Q

Cells formed during development that do not become part of the neonatal organism but involute or contribute to the fetal membranes (often contribute to the placenta)

A

Extraembryonic

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16
Q

Approximately 16-cell stage of an embryo with NO BLASTOCOEL

A

Morula

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17
Q

A spherical mass of cells that is composed of a trophoblast that surrounds a blastocoel and an embryoblast

A

Blastocyst

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18
Q

A cell that is totipotential and is present during very early development (product of cleavage)

A

Blastomere

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19
Q

What does totipotential mean?

A

A cell that can become any cell

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20
Q

What is is called when an embryo becomes surrounded by the endometrium of the uterus?

A

Implantation

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21
Q

Four structures of an embryo seen around days 4-5? What is the stage called when these 4 structures are present?

A

Trophblast - layer of cells outside the sphere
Zona pellucida - covering trophoblast
Embryoblast - inner cell mass
Blastocoel - fluid filled cavity

This is the blastocyst stage

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22
Q

What does progesterone level increase cause?

A

Increased ciliary movement to move the zygote

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23
Q

After 5 days, where does the blastocyst arrive?

A

Fundus of the uterus

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24
Q

Roles of zona pellucida in early development? (6)

A

BPPSPP
- Barrier so only one sperm penetrates
- Porous for communication between embryo and maternal rep. structures
- Protects embryo
- Signal to help trophoblast differentiation
- Prevent premature implantation
- Prevent the blastomeres for dissociating

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25
Q

What can early implantation result in?

A

Ectopic pregnancy

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26
Q

What day will the embryo hatch out of the zona pellucida?

A

Day 6

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27
Q

What does the endometrial epithelium express?

A

Different types of mucin proteins and pinopods

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28
Q

What are pinopods?

A

Small apical processes that contact the blastocyst and helps it adhere to endometrial epithelium

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29
Q

What is blastocyst adhesion mediated by?

A

Selectin and integrin binding (like leukocyte emigration from the bloodstream)

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30
Q

Once the trophoblast contacts the endometrial epithelium and invades, what happens?

A

Forms two layers
- Cytotrophoblast - inner
- Syncytiotrophoblast - outer

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31
Q

_______ develops into a multinuclear cell “mass” where the borders between individual cells are indistinct

A

Syncytiotrophoblast

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32
Q

Important functions of syncytiotrophoblast once it invades into the endometrial stroma

A
  • Induction/formation of villi (later become placenta)
  • Secretion of human chorionic gonadotropin (hCG)
33
Q

What does hCG do?

A
  • prevents shedding of endometrium and maintains secretion of progesterone
  • this is the hormone detected in pregnancy tests
34
Q

As the syncytiotrophoblast invades stroma, the embryoblast differentiates into _______ and _______

A
  • Epiblast: Will become the embryo proper
  • Hypoblast: In line with blastocytic cavity and forms primary yolk sac
35
Q

(defn.) a fluid filled cavity

A

Coelom

36
Q

What is Gastrulation?

A

The process of forming three embryonic germ layers - ectoderm, endoderm, mesoderm

37
Q

When is embryo implantation completed?

A

approx. day 10 embryo is completely embedded in endometrium and surrounded by syncytiotrophoblast

38
Q

What are decidual cells?

A

cells that accumulate glycogen and lipids throughout the uterus that can undergo apoptosis to release stored nutrients for embryonic growth

39
Q

What does the epiblast enlarge and give rise to?

A

Amnioblast = cells that surround the developing amniotic cavity

40
Q

when the hypoblast extends around the entire interior surface of the blastocoel, the inside is now known as the ________ and outside of it is known as the _________

A

primary umbilical vesicle; extraembryonic mesoderm

41
Q

What forms at junction of epiblast and hypoblast?

A

Bilaminar disk

42
Q

What is the fluid that begins to accumulate between the extra-embryonic mesodermal cells called? When does this occur?

A

Extraembryonic coelom at day 13

43
Q

3 distinct fluid-filled cavities developed in the embryo during week 2?

A
  • Umbilical vesicle
  • Amniotic cavity
  • Extraembryonic coelom
44
Q

Where does the extraembryonic coelom NOT surround the embryo?

A

at the junction of the amniotic cavity and the rest of the chorionic sac

45
Q

What will the junction of the amniotic cavity and the rest of the chorionic sac become?

A

The connecting stalk => the umbilical cord

46
Q

Two layers of extraembryonic mesoderm that form and are separated by the fluid in the extraembryonic coelom?

A
  • Extraembryonic splanchnic mesoderm = surrounds umbilical vesicles
  • Extraembryonic somatic mesoderm = just underneath the cytotrophoblast
47
Q

What is the chorion?

A

extraembryonic somatic mesoderm + trophoblast = wall of chorionic sac

48
Q

What is the chorionic sac?

A

Everything on the inside of the chorion

49
Q

How are the amniotic cavity, secondary umbilical vesicle, and bilaminar disk attached to the chorion?

A

Connecting stalk

50
Q

Where syncytiotrophoblast contacts endometrial blood vessels, the blood vessel deteriorates and blood pools

A

Lacunar networks

51
Q

During day 13-14, the cytotrophoblast sends extensions to the lacuna to form what?

A

Primary villi

52
Q

What is the thickened area of columnar cells that appears at the cephalad region of the hypoblast at the end of week 2?

A

Prechordal plate

53
Q

What is the role of the prechordal plate?

A

Embryonic organizing centre responsible for induction of other structures (especially head region)

54
Q

Organizer of the head and mouth region that helps to induce formation of structures found at the cephalad pole?

A

Hypoblast

55
Q

What prevents formation of structures that belong at the caudal aspect of the embryo?

A

Hypoblast

56
Q

What week does gastrulation occur?

A

Week 3

57
Q

In gastrulation, what does the bilaminar embryonic disc become?

A

Trilmainar embryonic disc

58
Q

When does the primitive streak appear?

A

Beginning of week 3

59
Q

What is the primitive streak?

A

Thickened linear band in the median plane of the dorsal aspect of the embryonic disk

60
Q

The primitive streak initiates the ______ of the epiblast

A

caudal region

61
Q

What results from proliferation and movement of epiblast cells to the median plane of the embryonic disc?

A

Primitive streak

62
Q

What do cells at the cephalad end of the primitive streak form?

A

primitive node

63
Q

A narrow groove called the __________ develops in the primitive streak, that is continuous with a small depression in the primitive node called the _________

A

primitive groove; primitive pit

64
Q

Cells leave the deep surface of the primitive streak and form ________

A

mesenchyme

65
Q

What is mesenchyme?

A

embryonic CT that forms supporting tissues of the embryo

66
Q

What are mesoblastic cells?

A

Formed by some mesenchyme, cells that are undifferentiated mesoderm

67
Q

Mesenchymal cells derived from the primitive streak are pluripotential cells, meaning what?

A

Differentiate into diverse types of cells (fibroblasts, chondroblasts, osteoblasts)

68
Q

What disappears by the end of week 4?

A

Primitive streak

69
Q

Trophoblast cell and tissue lineage?

A

Cytotrophoblast and syncytiotrophoblast

70
Q

Inner cell mass cell lineage?

A

Epiblast and hypoblast

71
Q

Hypoblast cell and tissue lineage?

A

Extraembryonic endoderm => Yolk sac endoderm

72
Q

Epiblast cell and tissue lineage?

A

Amniotic ectoderm and embryonic epiblast

73
Q

Embryonic epiblast cell and tissue lineage?

A

Embryonic ectoderm and primitive streak

74
Q

Embryonic ectoderm cell and tissue lineage?

A

Neural crest

75
Q

Primitive streak tissue and cell lineage?

A

Extraembryonic mesoderm, embryonic mesoderm, notochordal process, embryonic endoderm => allantoic endoderm

76
Q

What is developed when mesenchymal cells dive into the primitive pit and migrate cephalad?

A

Notochordal process

77
Q

When the notochordal process develops a lumen, what is it called?

A

Notochordal canal

78
Q

What are the roles of the notochord? (3)

A
  • Establish longitudinal axis of embryo
  • Signals for MSK and CNS dev
  • Contribute to IV discs

BMS150 Midterm 2 (14 decks)

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