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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
What can early implantation result in?
Ectopic pregnancy
26
What day will the embryo hatch out of the zona pellucida?
Day 6
27
What does the endometrial epithelium express?
Different types of mucin proteins and pinopods
28
What are pinopods?
Small apical processes that contact the blastocyst and helps it adhere to endometrial epithelium
29
What is blastocyst adhesion mediated by?
Selectin and integrin binding (like leukocyte emigration from the bloodstream)
30
Once the trophoblast contacts the endometrial epithelium and invades, what happens?
Forms two layers - Cytotrophoblast - inner - Syncytiotrophoblast - outer
31
_______ develops into a multinuclear cell "mass" where the borders between individual cells are indistinct
Syncytiotrophoblast
32
Important functions of syncytiotrophoblast once it invades into the endometrial stroma
- Induction/formation of villi (later become placenta) - Secretion of human chorionic gonadotropin (hCG)
33
What does hCG do?
- prevents shedding of endometrium and maintains secretion of progesterone - this is the hormone detected in pregnancy tests
34
As the syncytiotrophoblast invades stroma, the embryoblast differentiates into _______ and _______
- Epiblast: Will become the embryo proper - Hypoblast: In line with blastocytic cavity and forms primary yolk sac
35
(defn.) a fluid filled cavity
Coelom
36
What is Gastrulation?
The process of forming three embryonic germ layers - ectoderm, endoderm, mesoderm
37
When is embryo implantation completed?
approx. day 10 embryo is completely embedded in endometrium and surrounded by syncytiotrophoblast
38
What are decidual cells?
cells that accumulate glycogen and lipids throughout the uterus that can undergo apoptosis to release stored nutrients for embryonic growth
39
What does the epiblast enlarge and give rise to?
Amnioblast = cells that surround the developing amniotic cavity
40
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 _________
primary umbilical vesicle; extraembryonic mesoderm
41
What forms at junction of epiblast and hypoblast?
Bilaminar disk
42
What is the fluid that begins to accumulate between the extra-embryonic mesodermal cells called? When does this occur?
Extraembryonic coelom at day 13
43
3 distinct fluid-filled cavities developed in the embryo during week 2?
- Umbilical vesicle - Amniotic cavity - Extraembryonic coelom
44
Where does the extraembryonic coelom NOT surround the embryo?
at the junction of the amniotic cavity and the rest of the chorionic sac
45
What will the junction of the amniotic cavity and the rest of the chorionic sac become?
The connecting stalk => the umbilical cord
46
Two layers of extraembryonic mesoderm that form and are separated by the fluid in the extraembryonic coelom?
- Extraembryonic splanchnic mesoderm = surrounds umbilical vesicles - Extraembryonic somatic mesoderm = just underneath the cytotrophoblast
47
What is the chorion?
extraembryonic somatic mesoderm + trophoblast = wall of chorionic sac
48
What is the chorionic sac?
Everything on the inside of the chorion
49
How are the amniotic cavity, secondary umbilical vesicle, and bilaminar disk attached to the chorion?
Connecting stalk
50
Where syncytiotrophoblast contacts endometrial blood vessels, the blood vessel deteriorates and blood pools
Lacunar networks
51
During day 13-14, the cytotrophoblast sends extensions to the lacuna to form what?
Primary villi
52
What is the thickened area of columnar cells that appears at the cephalad region of the hypoblast at the end of week 2?
Prechordal plate
53
What is the role of the prechordal plate?
Embryonic organizing centre responsible for induction of other structures (especially head region)
54
Organizer of the head and mouth region that helps to induce formation of structures found at the cephalad pole?
Hypoblast
55
What prevents formation of structures that belong at the caudal aspect of the embryo?
Hypoblast
56
What week does gastrulation occur?
Week 3
57
In gastrulation, what does the bilaminar embryonic disc become?
Trilmainar embryonic disc
58
When does the primitive streak appear?
Beginning of week 3
59
What is the primitive streak?
Thickened linear band in the median plane of the dorsal aspect of the embryonic disk
60
The primitive streak initiates the ______ of the epiblast
caudal region
61
What results from proliferation and movement of epiblast cells to the median plane of the embryonic disc?
Primitive streak
62
What do cells at the cephalad end of the primitive streak form?
primitive node
63
A narrow groove called the __________ develops in the primitive streak, that is continuous with a small depression in the primitive node called the _________
primitive groove; primitive pit
64
Cells leave the deep surface of the primitive streak and form ________
mesenchyme
65
What is mesenchyme?
embryonic CT that forms supporting tissues of the embryo
66
What are mesoblastic cells?
Formed by some mesenchyme, cells that are undifferentiated mesoderm
67
Mesenchymal cells derived from the primitive streak are pluripotential cells, meaning what?
Differentiate into diverse types of cells (fibroblasts, chondroblasts, osteoblasts)
68
What disappears by the end of week 4?
Primitive streak
69
Trophoblast cell and tissue lineage?
Cytotrophoblast and syncytiotrophoblast
70
Inner cell mass cell lineage?
Epiblast and hypoblast
71
Hypoblast cell and tissue lineage?
Extraembryonic endoderm => Yolk sac endoderm
72
Epiblast cell and tissue lineage?
Amniotic ectoderm and embryonic epiblast
73
Embryonic epiblast cell and tissue lineage?
Embryonic ectoderm and primitive streak
74
Embryonic ectoderm cell and tissue lineage?
Neural crest
75
Primitive streak tissue and cell lineage?
Extraembryonic mesoderm, embryonic mesoderm, notochordal process, embryonic endoderm => allantoic endoderm
76
What is developed when mesenchymal cells dive into the primitive pit and migrate cephalad?
Notochordal process
77
When the notochordal process develops a lumen, what is it called?
Notochordal canal
78
What are the roles of the notochord? (3)
- Establish longitudinal axis of embryo - Signals for MSK and CNS dev - Contribute to IV discs

BMS150 Midterm 2 (14 decks)

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