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MSCT > Embryology: Body Plan > Flashcards

Embryology: Body Plan Flashcards

1
Q

What are the three embryonic germ layers?

A

Ectoderm, mesoderm, and endoderm

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2
Q

What tissues arise from the ectoderm?

A

Central/peripheral nervous systems, some skeletal and connective tissue of the head, epidermis, hair, nails, sensory epithelium of nose/ear/eye

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3
Q

What tissues arise from the mesoderm?

A

Skeletal/smooth/cardiac muscle, cartilage, bone, connective tissue, blood, urogenital system

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4
Q

What tissues arise from the endoderm?

A

Epithelium of the gut and it’s derivatives, epithelium of the respiratory system

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5
Q

What is caudal regression syndrome?

A

A disorder of impaired development of the lower half of the body. Can include lower limbs, lower back (lumbar/sacral vertebrae), lower gut, and urogenital tracts.

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6
Q

What is the underlying mechanism of caudal regression syndrome?

A

Abnormal growth and migration during gastrulation resulting in abnormal development of the caudal mesoderm, which is the last mesoderm to form

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7
Q

What is sirenomelia?

A

An extreme and rare form of caudal dysplasia in which the two lower limbs are fused at the midline. GI and GU organs are often malformed or absent. Usually fatal.

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8
Q

What is embryonic induction?

A

The stimulation of a specific developmental pathway in one group of cells by a closely approximated second group of cells. The inducing tissue passes a signal to the responding tissue, which “changes the fate” of the responding tissue.

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9
Q

What are the three different mechanisms of embryonic induction?

A

Diffusion of the inducing molecule from inducing tissue to responding tissue; contact between the ECM of inducing and responding cells; direct contact between the inducing and responding cells

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10
Q

What are the four examples of embryonic induction that Dr. Hartley wants us to know?

A

Primitive streak formation, mesoderm formation, neural induction, and lens induction.

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11
Q

What is the mechanism of primitive streak formation?

A

Signaling from extra-embryonic tissue (via TGF-beta and Wnt family molecules) induces epiblast cells to form primitive streak

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12
Q

What is the mechanism of mesoderm formation?

A

FGF produced by the endoderm causes migrating epiblast cells to become mesoderm

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13
Q

What is the mechanism of neural induction?

A

Primitive node cells produce TGF-beta family antagonists, FGF/IGF family molecules, which causes the ectoderm to form the neural plate

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14
Q

What is the mechanism of lens induction?

A

The optic vesicle develops as an extension of the embryonic brain and produces BMP4 (TGF-beta family), causing the overlying ectoderm to differentiate into the lens instead of skin

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15
Q

What is the period of susceptibility and when does it occur?

A

The period when the embryo is most vulnerable to environmental factors causing abnormal development; weeks 4-8

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16
Q

Insults during which period usually result in spontaneous abortion?

A

First three weeks

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17
Q

What is an anomaly?

A

A marked deviation from “normal”

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18
Q

What is an association?

A

A nonrandom appearance of two or more anomalies together with an unknown cause

19
Q

What is the definition of congenital?

A

Present at birth

20
Q

What is a deformation?

A

A structural defect resulting from mechanical forces on the fetus over a prolonged period

21
Q

What is a malformation?

A

A structural defect resulting from abnormal embryonic or fetal development

22
Q

What is a sequence?

A

Multiple defects determined by a primary anomaly

23
Q

What is a syndrome?

A

A group of anomalies occurring together that have a specific common cause

24
Q

What is a teratogen?

A

An agent or factor that can disturb the development of an embryo

25
Q

How long after fertilization does the blastocyst implant in the uterine wall?

A

About 1 week

26
Q

What does the egg become after the development of the two pronuclei?

A

Zygote

27
Q

What does the zygote become after it’s first mitotic division?

A

Blastomere

28
Q

For how long is the blastomere totipotent?

A

Until 4-8 cell stage

29
Q

What is the definition of totipotent?

A

Can give rise to both the embryo and the fetal part of the placenta

30
Q

What does the blastomere become when it reaches the 16 cell stage?

A

Morula

31
Q

What is the definition of pluripotent?

A

Can give rise to all cell types except the placenta

32
Q

What two processes happen as the cells of the morula divide?

A

Compact (move closer together) and cavitate (secrete fluid to form a cavity)

33
Q

What does the morula become after compaction and cavitation?

A

Blastocyst

34
Q

How long does the implantation process take?

A

About a week (week 1-2)

35
Q

What is the embryoblast?

A

The inner cell mass of the blastomere; forms the embryo

36
Q

The embryoblast contains what type of stem cells?

A

Totiipotent

37
Q

What is the trophoblast?

A

The outer cell mass of the blastomere; form the fetal part of the placenta

38
Q

The trophoblast contains which type of stem cells?

A

Pluripotent

39
Q

When do the blastomeres segregate into the embryoblast and the trophoblast?

A

Around day 6

40
Q

When do the blastomeres segregate into the embryoblast and the trophoblast?

A

Around day 6

41
Q

What two layers does the embryoblast differentiate into, and what cavities do they form?

A

Epiblast - columnar cells that secrete fluid to form the amniotic cavity; hypoblast - cuboidal cells migrate to line the blastocyst to form the primitive yolk sack

42
Q

What is the embryo called when it forms two layers of the embryoblast?

A

Bilaminar embryo

43
Q

What two layers does the trophoblast differentiate into, and what cavities do they form?

A

Syncytiotrophoblast - outer layer, one cell with many nuclei; cytotrophoblast - actively proliferating cells

MSCT (14 decks)

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