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Year 1: 03. MSK Exam 1 > Lecture 6: Fertilization and Gastrulation > Flashcards

Lecture 6: Fertilization and Gastrulation Flashcards

1
Q

When is it most likely for something to go wrong in human development?

A

The first 8 weeks (aka the embryonic trimester)

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2
Q

When does the Obstetrical calendar start? When does the calendar assume fertilization occurs?

A

Obstetrical Calendar starts 1st day of LMP

Fertilization starts 14 days after 1st day LMP (Approximates with ovulation, assumes the earliest possible point for fertilization)

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3
Q

Where does the Ovulatory Calendar start?

A

Fertilization (Two weeks after the obstetrical calendar starts)

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4
Q

What is the Zona Pellucida made of?

A

Glycoprotien Meshwork

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5
Q

Where does most fertilization occur?

A

The Ampulla (distal 1/3 of the fallopian tube)

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6
Q

What all occurs in week 1? (5 things)

A
  1. Fertalization
  2. Cleavage
  3. Blastocyst formation
  4. Inner Cell Mass (Embryoblast)
  5. Implantation
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7
Q

What is another name for the inner cell mass?

A

Embryoblast

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8
Q

What is capacitation?

What does this allow for?

A

The removal of a glycoprotien coat and seminal plasma protiens from the plasma membrane of the sperm for fertilization

-passage of sperm through corona radiata

The Acrosome Reaction

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9
Q

What does a sperm use to penetrate the corona radiata?

A

Hyaluronidase

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10
Q

What does a sperm use to penetrate the zona pellucida?

A

Esterases, acrosin, and neuraminidase

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11
Q

What does the Zona Pellucida do to prevent polyspermy?

A

Changes conformation - the meshwork becomes rigid

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12
Q

What technique might be performed to induce pregnancy in a couple for which the male has a low sperm count?

A

Intracytoplasmic sperm injection

Make up for the diminished liklihood of a sperm contacting an egg by directly injecting the sperm into the egg.

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13
Q

Going from exterior to interior, what are the layers of a human oocyte?

A
  1. Corona Radiata
  2. Zona Pellucida
  3. Perivitelline Space
  4. Plasma membrane of oocyte
  5. Cytoplasm of oocyte
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14
Q

What does the perivitelline space assist in?

What does it do?

A

The zona reaction

Releases granules to block polyspermy

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15
Q

What is the name of the cell that divides in cleavage?

A

Blastomere

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16
Q

When does cleavage begin to occur?

A

At about 30 hours

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17
Q

When does the dividing embryo become a morula?

A

Day 3

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18
Q

When does the embryo become an early blastocyst?

What changes to make this structure?

A

Day 5

A fluid filled cavity (blastocystic cavity) is formed

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19
Q

When does the embryo enter the uterine body?

A

Day 3-4

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20
Q

When does implantation typically occur?

A

Around day 6

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21
Q

What stage is the developing embryological structure in by day 7 (end of week 1)?

What are the main structures of this structure?

A

Late Blastocyst

Inner cell mass, blastocyst cavity, and trophoblast ring

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22
Q

What two structures does the trophoblast give rise to, and what do those structures do?

A

Cytotrophoblast

This is a mitotically active stem cell layer, forms the syncytiotrophoblast. Stays on the outside

Syncytiotrophoblast

Contains proteolytic enzymes and hCG - responsible for implantation and initial pregnancy signaling.

Conceptually, the trophoblast gives rise to the placenta.

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23
Q

What does the inner cell mass give rise to?

A

The embryo!

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24
Q

Where do we get Embryos for Stem Cell Therapy?

A

From Cryo-preserved embryos

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25
Q

At what point does the Zona Pellucida disappear?

What this called?

A

By day 7

“Hatching of the embryo”

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26
Q

What immunosupressant protien to the trophoblasts produce?

When do we start to see this be produced?

A

Early pregnancy factor

After about 10 days

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27
Q

What is Hydatidiform Mole?

What causes the complete version?

What causes the partial version?

A

Abnormal proliferation of trophoblasts.

Complete: An empty oocyte getting fertalized, and then duplicating the sperm OR an empty oocyte getting fertalized by two sperm

Partial: Normal egg fertalized by two sperm

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28
Q

What would you call a malignant tumor which has developed from a hyatidiform mole?

Where do these types of tumors like to metastasize? (6 places)

A

Choriocarcinoma

  • Liver
  • Lung
  • Vagina
  • Intestine
  • Bone
  • Brain
29
Q

What are the clinical features of Hydatidiform Mole?

A
  • Vagnial Bleeding (villi can sometimes be seen)
  • Pressure or pain of the pelvis
  • Enlarged Uterus
  • Hyperemesis Gravidarum
  • Excess hCG
30
Q

What two structures make up the Week 2 Inner Cell Mass?

A

Epiblast and Hypoblast

(In week 2 the inner cell mass differentiates into the epiblast and hypoblast)

31
Q

What three structures are formed from the Epiblast?

A

Ectoderm

Amnion

Amnionic Cavity

32
Q

What does the Hypoblast give rise to?

What three structures does that in turn give rise to?

A

The Extraembryonic Endoderm

  1. Prechordal Plate
  2. Primary and secondary yolk sac (aka umbilical vesicle)
  3. Extraembryonic Mesoderm
33
Q

Where would one find Extraembryonic Somatic Mesoderm?

A

Lining the trophoblast and covering the amnion

(Next to ectoderm)

34
Q

Where would one find Extraembryonic Splanchnic Mesoderm?

A

Lining the yolk sac

(Next to endoderm)

35
Q

What does the prechordal plate become?

What other function does it have?

A

The mouth

Organizes the head

36
Q

When is the Hypoblast present?

A

The hypoblast is only present during week 2!

The hypoblast is only present during week 2!!

The hypoblast is only present during week 2!!!

(She said this three times during lecture, so make sure you’ve got this one on lock)

37
Q

What is extraembryonic coelom?

A

The hollow space outside of the embryo.

38
Q

What is the Connecting Stalk made of?

A

Extraembryonic Somatic Mesoderm

39
Q

What is the Primitive Blood made of?

A

Extraembryonic Splanchnic Mesoderm

40
Q

What is the Chorion made of?

What is it?

A

Extraembryonic somatic mesoderm

Cytotrophoblast

Syncytiotrophoblast

The Chorion is one of the layers of the placenta.

41
Q

Where might an Ectopic Pregnancy implant?

A

In the Uterine Tube, or in the Abdomen

42
Q

What is placenta previa?

What is the main clinical manefestation?

A

Partial or complete blockage of the cervix by the placenta.

Vaginal bleeding beyond 20 weeks gestation.

43
Q

What happens in week 3?

A

Gastrulation

It’s also the week that mom often knows she’s pregnant

Week 3 = 3 layers

44
Q

What systems are beginning to develop in week 3?

A

Heart and CNS

45
Q

Women often realize they’re pregnant during what phase of embryological development?

A

Gastrulation - Week 3

46
Q

What sort of things come from the Ectoderm?

A

Skin, hair, nails, brain, spinal cord.

47
Q

What sorts of things develop from the Mesoderm?

A

Muscle, bone, blood, heart, spleen

48
Q

What sorts of structures come from the Endoderm?

A

Lungs, GI tract, bladder, glands (eg. thyroid)

49
Q

Cells of the epiblast push down and encounter signals that cause them to differentiate into what?

A

True endoderm and mesoderm

The epiblast replaces all of the cells of the hypoblast!

50
Q

What do you call the cells of the epiblast that remain on top of the tri-laminar disc?

A

Ectoderm

51
Q

The primitive streak forms in which half of the epiblast?

A

The caudal end.

52
Q

What does the Lateral Plate of the mesoderm give rise to?

A

Connective tissue

(Blood, Lymph, Mesenteries, and Cardiovascular)

53
Q

What does the Intermediate Mesoderm give rise to?

A

Urogenital Structures

(Like the kidneys and gonads)

54
Q

What three types of Mesoderm are present during gastrulation?

A

Paraxial Mesoderm

Intermediate Mesoderm

Lateral Plate

55
Q

What does the heart form from?

A

The cardiogenic area.

56
Q

What layers make up the prechordal plate and the cloacal membrane?

When do these two structures develop?

A

Just ectoderm and endoderm.

There is no mesoderm, and no blood supply

Week 2, before gastrulation occurs.

57
Q

What is the Septum Transversum?

What layer is it made of?

A

The future Diaphragm.

Mesoderm

58
Q

What causes sacrococcygeal and orapharyngeal teratomas?

A

A remnant of the primitive streak

OR

Abnormal Migration of Stem Cells

59
Q

What layer does the notochord come from?

A

Mesoderm

60
Q

What three things does the notochord do?

A

Induces the midline for the embryo

Serves as a template for the vertebral column (does not itself form the vertebral column)

induce the formation of the neural plate and CNS

61
Q

What connects the amniotic cavity to the yolk sac?

What is that opening called?

A

The notochordal process fuses with the endoderm, coming from the primitive pit. This creates an opening into the yolk sac through that pit.

Neurenteric Canal

62
Q

For the Allantois

What layer is it formed of?

What is it the template for?

What does it become?

A

Endoderm

Umbilical arteries and vein (does not become these structures, but provides a template)

Becomes the Urachus

63
Q

What cancer can come from the notocord?

Where do these neoplasms form?

What germ layer will these have come from?

A

Chordomas

Spheno-occipital region of skull, and sacrum

Mesoderm

64
Q

What does the Paraxial Mesoderm give rise to?

A

Somites

(Define the muscle, skeleton and skin)

65
Q

What do Somites become? (3 things)

What germ layer do they come from?

A

Vertebral Skeleton (Scleratome)

Muscle (Myotome)

Dermis (Dermatome)

Mesoderm

66
Q

What does the Intermediate Mesoderm become?

A

Kidneys

Gonads

67
Q

What structures arise from the Lateral Plate Mesoderm?

How is the Lateral Plate Mesoderm Divided?

A

Blood, Lymph, Mesentaries, Cardiovascular

Somatic / Splanchnic

Somatic is next to ectoderm, Splanchnic is next to endoderm

68
Q

What supplies the extraembryonic mesoderm to support the placenta in week 3?

A

The Primitive Streak

Some of the differentiating epiblast cells push down, become mesoderm, and then leave the embryo via the connecting stalk to supply the placenta. These mesoderm cells are now called “extraembryonic”

Year 1: 03. MSK Exam 1 (23 decks)

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