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Embryo Exam II > Lecture 11 - Body Plan III > Flashcards

Lecture 11 - Body Plan III Flashcards

1
Q

Initial signaling for endoderm formation occurs during ___.
Depends on…
Gradient?
Gut?

A

Gastrulation.

Nodal expression during gastrulation

Ant/Post gradient: ^levels of nodal anteriorly and lower posteriorly. Also post is FGF-4

Post: Cdk-2
Ant: Hex, Sox-2, Foxa-2
Refined differentiation of gut depends on Hox genes

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2
Q

Both the oropharyngeal membrane and cloaca plate are form by __ and __ with no intervening __.

Perforations are the result of…

Stomodeum becomes the…
Proctodeum becomes the…

A

Endoderm and ectoderm; mesoderm

Instability created by lack of mesoderm

Oral cavity
Anal region

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3
Q

Fourth Week Embryo

A

4mm long

Rudiments for most major organs are now present (save for kidneys and limbs)

Prominent pharyngeal arches

Wolffian ridge

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4
Q

Wolffian Ridge

A

IDk

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5
Q

48-hour chick embryo

A

Pharyngeal Arches: Mandibular, hyoid
Pharyngeal slits 1-3

Overall J shape

Yolk sac is empty (give rise to primordial germ cells)

circulatory arcs are present, basic but bidirectional

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6
Q

In a 10 mm Pig embryo…

A

Maxillary process, mandibular arch, stomodeum

U-shaped nervous system

Pharynx/glottis

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7
Q

4-week human embryo

A

Similar to 48- hr chick
Overall J shape

Yolk sac is empty (give rise to primordial germ cells)

circulatory arcs are present, basic but bidirectional

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8
Q

Amnion

A

Inner cell mass, epiblast derivative

Extraembryonic tissue

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9
Q

Yolk Sac

A

Inner cell mass, hypoblast derivative

Extraembryonic tissue

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10
Q

Chorion

A

Part of fetal maternal interface

Extraembryonic tissue

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11
Q

Allantois

A

Inner cell mass, interfaces with placenta via umbilical cord

Extraembryonic

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12
Q

Placenta

A

Trophoblast derivative (implantation)

Fetal-maternal interface (“embryonic stock”)

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13
Q

Chorion

A

Trophoblast derivative

Fetal-maternal interface (“embryonic stock”)

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14
Q

Amnion

A
  • Buffer against mechanical injury
  • accommodates growth
  • allows normal movements
  • protects fetus from adhesions
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15
Q

Hydramnios

A

Relate to esophageal atresia and anencephaly????

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16
Q

Oligohydramnios

A

Relate to renal agenesis ???

17
Q

Formation of amniotic fluid

A

Phase I:

  • first 20 weeks of pregnancy
  • free diffusion of electrolytes through fetal ectoderm
  • secretion by amniotic membrane

Phase II:

  • contributions from fetal urine
  • filtration from vessels associated with chorion laevae
  • possible other sources
18
Q

Yolk sac ___ in size and exists ___ the amniotic cavity. Eventually degrading.

A

Decreases

Outside

19
Q

Yolk Sac Functions

A

May Concentrate:

  • folic acid
  • vitamins A, B, E

Site of origin of primordial germ cells

Location of blood islands (origin of initial blood cells)

Meckel’s diverticulum?

20
Q

Extraembryonic hematopoiesis

A

Formation of blood cells outside of embryo

Related to blood islands of yolk sac

21
Q

Meckel’s diverticulum

A

Blind sac/pouch

Leftover/rudimentary yolk

22
Q

Allantois

A

Umbilical vessels develop in mesoderm of allantois

Proximal part=urachus

  • associated with urinary bladder
  • becomes median umbilical ligament
23
Q

Placental Development

A 
Previllous embryo
Primary Villous Stage
Secondary V Stage
Tertiary V Stage
Final Development
24
Q

Previllous Embryo

A

No villi have formed on trophoblast

25
Q

Primary Villous Stage

A

Solid, cytotrophoblastic, ectodermal primary villi appear

26
Q

Secondary Villous Stage

A

Mesodermal cores appear within the primary villi

27
Q

Tertiary Villous Stage

A

Characterized by the appearance of blood vessels within the mesenchymal core of the secondary villi

28
Q

Final Development

A

Cytotrophoblastic columns

Cytotrophoblastic shells
-formed by expansion of the cytotrophoblastic columns over th maternal decidual cells

Anchoring villi
-villi that are anchored to the cytotrophoblastic shell (as opposed to floating villi)

29
Q

Blood Flow Pathway (Maternal)

A
  • Maternal blood enters inter Villous spaces (trophoblastic lacunae) from spiral arteries
  • exchange of materials (resp gases, nutrients, waste products) between maternal blood in lacunae and fetal blood in capillaries in the villi
  • maternal blood returns to maternal veins in the decidua basalis
30
Q

Blood Flow Pathway (Fetal)

A
  • Fetal Blood is entirely enclosed within vessels
  • travels to capillary beds within placental villi via umbilical arteries (usually 2)
  • returns from cap beds within placental villi via umbilical vein (1)
31
Q

What is the purpose of villi in the placenta of a developing embryo?

A

Greatly increases surface area allowing for greater gas exchange and absorption of the placenta

Embryo Exam II (8 decks)

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