EMB: Fertilization & Gastrulation Flashcards by Deleted Deleted

When it’s said the embryo is 6 weeks along clinically, what is the actual age of the embryo?

4 weeks

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When does the obstetrical/gestational/menstrual calendar begin?

How far ahead is the Fertilization calendar?

1st day of the females last menstrual cycle

2 weeks after

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Embryology focuses on what trimester?

first trimester

NOTE: fetal development is second and third trimester

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Which layer of the human ovum is an amorphus, acellular, proteoglycan meshwork?

A. Corona Radiata

B. Zona Pellucida

C. Nucleus

D. Perivitelline space

E. Plasma Membrane

Zona Pellucida

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What is found in the head of the sperm?

Acrosome surrounding the Nucleus (23 X or 23Y)

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What portion of the human sperm posses mitochondria?

A. End tail piece

B. Principal piece of tail

C. Middle Tail Piece

D. Neck

Middle Tail Piece

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Cleavage, Formation of the blastocyst, inner cell mass, and implantation starts at what day and goes until when?

Day 0 to Day 7

(ovulation + fertilization)

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What is capacitation?

How long does it take?

Removal of glycoprotein coat from acrosome as the sperm moves through

7 hours

Capacitation = lid removal

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The passage of sperm through the ovum’s corona radiata must occur in order for the sperm to get to the Zona pellucida. Getting through the corona radiata is a group effort by sperm that requires what enzyme?

Hyaluronidase

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Once sperm pass through the corona radiata, the sperm attempt to penetrate the Zona Pellucida. What enzymes are released by sperm to erode the ZP?

What is the principal enzyme?

Esterases

Acrosin

Neuraminidase

Remeber: EAN

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Once sperm reach the zona pellucida the zona reaction occurs.

What is the goal of the zona reaction?

How does it occur?

Blocks polyspermy

Changes conformation that only allows one sperm in, and traps the other sperm in the ZP

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What portion of the sperm enters the oocyte cytoplasm after fusion of plasma membranes?

Head and Tail

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About how long does fertilization take?

24 hours

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What are results of fertilziation? (5)

Completion of 2nd meiotic division

diploid # of chormosomes

sex determination

metabloically active oocyte

initiation of cleavage

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Cleavage increases cell number while decreasing cell size. At what point does cleavage produce the morula (past 8 cell stage)?

After the morula is formed we go on to form the blastocyst. When does this enter the uterus?

Day 3

Day 4

Fertilization = day 0

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What day does the blastocyst no longer have a zona pellucida around it? This is also known as “hatching”

Day 7

NOTE: at Day 5 it’s still present, Day 6 it degrades, Day 7 its gone

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What is another name for inner cell mass?

What is the stem cell layer for the placenta?

Embryoblast

Trophoblast

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At week one we have the late blastocyst which is comprised of what 3 main things?

Inner cell mass

Blastocyst cavity

Trophoblast layer

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In In-vitro fertilization, mature oocytes are collected during a laparoscopy, and placed in a petri dish with capacitated sperm. Cleavage is allowed to occur in the medium, and cells are collected and embryos are transferred into the uterus. What cell stage are the embryos?

4-8 cell stage

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Embryonic stem cells are collected from what portion of the blastocyst?

Inner cell mass

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What structure releases early pregnancy factor?

What is the result of releasing early pregnancy factor?

Trophoblast

Immunosuppressive so the body doesn’t reject the embryo as foreign

Gives rise to cytotrophoblast and synctiotrophoblast

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What are the characteristics of the cytotrophoblast?

What do the cells of the cytotrophoblast gives rise to?

Mitotically active stem cell layer

Gives rise to the synctotrophoblast

What are synctiotrophoblasts responsible for?

Synctiotrophoblast releases what enzyme that’s associated with pregnancy test determination?

Implantation and initial pregnancy signal

Chorionic Gonadotropin (hCG)

How are Hydatidiform Moles created?

Abnormal trophoblastic proliferation

Excessive amounts of hCG

There are 2 types of Hydatidiform Moles, that result for different reasons. What type of mole forms from Fertilization of an empty oocyte, followed by duplication of the sperm? What type of mole forms from fertilization of an empty oocyte by two sperm? What type of mole forms from fertilization of a normal oocyte by two sperm?

Complete mole Complete mole Partial mole

What are some clinical features of hydatidiform Mole formation?

Vaginal bleeding Pelvic pressure/pain Enlarged uterus Hyperemesis gravidarum

What is a choriocarcinoma?

Hydatidiform mole that develops into a malignant tumor *(3-5% of moles become this)*

At what week do we give rise to 2 different cell types from the inner cell mass? What are these cell types?

Week 2 Epiblast Hypoblast

What are the components of the epiblast?

Ectoderm Amnion Amnion cavity

What portion of the inner cell mass is only present during week 2, acting as a place holder until week 3?

Hypoblast layer

The hypoblast forms what 3 structures? What does that structure include?

Endoderm Prechordal plate (future mouth) Primary & secondary yolk sac Extraembryonic mesoderm

Which of the following lines the trophoblast and covers the amnion? A. Extraembryonic Coelom B. Extraembryonic Somatic Mesoderm C. Extraembryonic Splanchnic mesoderm

Extraembryonic Somatic Mesoderm

Which of the following lines the yolk sac? A. Extraembryonic Coelom B. Extraembryonic Somatic Mesoderm C. Extraembryonic Splanchnic mesoderm

Extraembryonic Splanchnic mesoderm

Hollow cavity outside of the embryo? A. Extraembryonic Coelom B. Extraembryonic Somatic Mesoderm C. Extraembryonic Splanchnic mesoderm

Extraembryonic Coelom

All of the following derivatives of the extraembryonic mesoderm are from the somatic mesoderm, except for which of the following which is from splanchnic mesoderm? A. Connecting Stalk B. Primitive Blood C. Chorion

Primitive Blood

Which of the following derivatives of the extraembryonic mesoderm forms at the embryonic pole, and changes position during development? A. Connecting Stalk B. Primitive Blood C. Chorion

Connecting stalk

Which of the following derivatives of the extraembryonic mesoderm forms in the wall of the yolk sac? A. Connecting Stalk B. Primitive Blood C. Chorion

Primitive blood

Which of the following derivatives of the extraembryonic mesoderm forms in the cytotrophoblast and synctiotrophoblast? A. Connecting Stalk B. Primitive Blood C. Chorion

Chorion

What is the number 1 reasons mothers bleed to death in pregnancy? Where do these pregnancies occur?

Tubal pregnancies Ampulla or isthmus

Bleeding beyond 20 weeks is a sign of what potential pregnancy error? What should the physician not perform?

Placenta previa: placenta implants close or on internal oss of cervix No digital vaginal exam

What are the degrees of placenta previa that demonstrate how much of the internal oss of the cervix is being covered by the placenta?

Marginal Partial Total

Summarize each developmental week in a quick phrase in terms of formation Week 1 Week 2 Week 3

Week 1: formation of inner cell mass Week 2: formation of epiblast and hypoblast Week 3: Gastrulation

What is gastrulation?

Formation of 3 germ layers Ectoderm Mesoderm Endoderm

What germ layer is the septum transversum from? What does the septum tranversum give rise to?

Mesoderm Diaphragm

What germ layers is the prechordal plate made of?

Ectoderm and endoderm

What causes sacral coccygeal teratomas?

Presence of alll 3 germ layers in the caudal region due to persistance of the primitive streak

Oropharyngeal Teratoma is formed by what?

Abnormal migration of primordial germ cells

The notochord comes from what germ layer? What 2 things does it become?

Mesoderm Template for vertebral column Induces formation of neural plate via Shh

What is the template for the umbillical arteries and veins? What does it become? What germ layer does it come from?

Allantois Becomes urachus Endodermal

What are chordomas? What do they arise from?

Slow growing aggressive neoplasms of bone Remnants of notochord NOTE: occur in axial skeleton in spheno-occipital region

What structure is on either side of the notochord? What does it give rise to?

Paraxial Mesoderm Somites

What structures do intermediate mesoderm produce?

Kidneys Gonads

Lateral plate mesoderm gives rise to connective tissue

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