Lecture 11

Question 1

Endoderm formation depends on what?

Answer 1

nodal expression during gastrulation

Question 2

The anterior- posterior gradient:
higher levels of _____ anteriorly
lower levels of ____ + presence of ____ posteriorly

Answer 2

nodal

nodal; FGF-4

Question 3

What does the posterior gut express?

Answer 3

Cdx-2

Question 4

What does Cdx-2 do?

Answer 4

promotes hindgut development

suppresses formation of anterior gut structures

Question 5

What does the anterior gut express?

Answer 5

Hex, Sox-2, Foxa-2

Question 6

More refined differentiation of gut structures depends on the ____ genes

Answer 6

Hox

Question 7

What forms the oropharyngeal membrane and cloacal plate?

Answer 7

endoderm and ectoderm

Question 8

What is the stomodeum?

Answer 8

future oral cavity

Question 9

What is the proctodeum?

Answer 9

future anal region

Question 10

Describe the fourth week embryo

Answer 10

4mm long
rudiments for most of the major organ systems are present (except limbs and kidneys)
prominent pharyngeal arches
wolffian ridges

Question 11

The amnion, yolk sac, chorion and allantois are all what?

Answer 11

extra embryonic tissues

Question 12

The placenta and chorion are what?

Answer 12

fetal maternal interface

Question 13

What are the functions of the amnion?

Answer 13

buffer against mechanical injury
accommodates growth
allows normal movements
protects fetus from adhesions

Question 14

Describe phase I of formation of amniotic fluid

Answer 14

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

Question 15

Describe phase II of formation of amniotic fluid

Answer 15

• contributions from fetal urine

- filtration from vessels associated with chorion laevae

Question 16

What are the possible yolk sac functions?

Answer 16

may concentrate folic acid and vitamins

• site of origin of primordial germ cells
• location of blood islands

Question 17

Where do the allantoic vessels develop?

Answer 17

mesoderm of the allantois

Question 18

What is the proximal part of the allantois?

Answer 18

urachus

Question 19

Describe the previllous embryo

Answer 19

no villi have been formed on the trophoblast

Question 20

describe the primary villous stage of placental development

Answer 20

solid, cytotrophoblastic, ectodermal primary villi appear

Question 21

Describe the secondary villous stage of placental development

Answer 21

mesodermal cores appear within the primary villi

Question 22

describe the tertiary villous stage of placental development

Answer 22

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

Question 23

Describe the final development of placental development

Answer 23

• cytotrophoblastic columns
• cytotrophoblastic shells
• anchoring villi

Question 24

Describe the maternal blood flow pathway

Answer 24

• maternal blood enters intervillous space from spiral arteries
• exchange of materials between maternal blood in lacunae and fetal blood in capillaries in the villi
• maternal blood returns to maternal veins in the decidua basalis

Question 25

Describe the fetal blood flow pathway

Answer 25

• fetal blood entirely enclosed within vessels
• travels to capillary beds within placental villi via umbilical arteries
• returns from capillary beds within placental villi via umbilical vein