Embryology 3 - The Early Fetal-Maternal Circulation (Week 8)

Question 1

REVIEW: The amniotic cavity is on the __________ (dorsal/ventral) surface of the developing embryo

Answer 1

dorsal

Question 2

REVIEW: The umbilical vesicle is on the __________ (dorsal/ventral) surface of the developing embryo

Answer 2

ventral

Question 3

REVIEW: The extraembryonic coelom that surrounds both the amniotic cavity and umbilical vesicle becomes the what?

Answer 3

chorionic cavity/sac

Question 4

The chorion = ____________ on the inside + _____________ on the outside

Answer 4

extraembryonic somatic mesoderm,

trophoblastic cells

Question 5

REVIEW: the trophoblasts consists of the ___________ and _____________

Answer 5

cytotrophoblast,

syncytiotrophoblast

Question 6

REVIEW: The ______________ invades the endometrial stroma and helps induce apoptotic death of decidual cells

Answer 6

syncytiotrophoblast

Question 7

_____________ release energy-rich glycogen and lipids that can freely diffuse to (and feed) the embryo

Answer 7

Decidual cells

Question 8

REVIEW: What do the syncytioblasts release?

Answer 8

hCG

Note: this allows ovaries to continue to secrete high levels of progesterone, preventing endometrium shedding during menstruation

Question 9

True or False: When the chorion and embryo have grown large enough and the distance becomes too far for the diffusion of nutrients between the endometrium and the embryo, the embryo must form its own circulation system. This happens around week 4.

Answer 9

True

Question 10

The ___________ begins to form primary chorionic villi that project into the lacuna

Note: lacuna = “lakes of blood” from mom’s circulation

Answer 10

cytotrophoblast

Question 11

When does the embryonic heart begin to beat?

Answer 11

~ day 21 (end of week 3)

Question 12

What does the maternal-fetal circulation depend on?

Answer 12

1) a fetal cardiovascular system
2) structures within the endometrium that allow exchange with the fetal cardiovascular system

Question 13

What are primary chorionic villi composed of?

Answer 13

cytotrophoblasts surrounded by a syncytiotrophoblastic shell

Note: ~ week 2

Question 14

What are secondary chorionic villi composed of?

Answer 14

extraembryonic mesenchymal core surrounded by cytotrophoblast and syncytiotrophoblastic shell

Note: ~ week 3 (day 16)

Question 15

What are tertiary chorionic villi composed of?

Answer 15

blood vessels (capillaries) within the mesenchymal core

• at this stage, fetal blood can now exchange substances (gas, nutrients, waste) between the maternal lacuna through the membrane formed by the tertiary villus

Note: ~ end of week 3 (day 21)

Question 16

As villi develop, the cytotrophoblast pushes through the syncytiotrophoblast layer and forms the ______________, which anchors the chorionic sac and attaches it to the endometrium

Answer 16

cytotrophoblastic shell

Question 17

a villus that attaches to the endometrium via cytotrophoblastic extensions

Answer 17

anchor villus

Question 18

The ___________ is synonymous with the endometrium in a pregnant woman

Answer 18

decidua

Question 19

What are the three separate areas of the decidua?

Answer 19

1) decidua basalis
2) decidua capsularis
3) decidua parietalis

Question 20

the decidua that forms the placenta and is connected ot the embryo via the umbilical cord

Answer 20

decidua basalis

Question 21

decidua that does not include the basalis, but is still associated with and covers the embryo

Answer 21

decidua capsularis

Question 22

decidua formed by the endometrium that is NOT part of the embryo and is far from the site of implantation

Answer 22

decidua parietalis

Question 23

True or False: As the embryo develops, the amniotic cavity gets bigger and bigger, and the chorionic cavity smaller and smaller.

Answer 23

True

Eventually our umbilical vesicle completely deteriorates and disappears

Question 24

Maternal blood is found in the _____________

Answer 24

intervillous spaces

Note: maternal blood is “shot into” these spaces where it bathes the tertiary chorionic villi

Question 25

Where do blood cells and blood vessels first develop?

Answer 25

extraembryonic tissue (umbilical vesicle and connecting stalk/chorion)

Note: begins in the 3rd week

Question 26

the development of brand new blood vessels from the mesoderm

Answer 26

vasculogenesis

Question 27

the “sprouting” of blood vessels formed by vasculogenesis (connecting blood vessels to each other)

Answer 27

angiogenesis

Question 28

True or False: Angioblasts are derived from the mesoderm and are the cells that grow “blood islands”

Answer 28

True

Question 29

As blood islands develop, they develop lumens which become what?

Answer 29

blood vessels

Question 30

Angioblasts also give rise to early red blood cells within and outside the embryo. They are derived from where?

Answer 30

the inner lining of the new vessels (endothelium)

OUTSIDE EMBRYO: from the endothelium in allantois and the umbilical vesicle

INSIDE EMBRYO: from the endothelium of the dorsal aorta

Question 31

True or False: Within the embryo, angioblastic chords form a pair of heart tubes that fuse at the end of the 3rd week to form the primordial heart tube (a single ventricle)

Answer 31

True

Question 32

Cranial folding brings the heart tube __________ (ventrally/dorsally) and ____________ (cephalad/caudally)

Answer 32

ventrally and caudally

Question 33

When do RBCs arise from the dorsal aorta?

Answer 33

~ week 5

Question 34

The ___________ sends blood to the embryo and then to the umbilical artery (to tertiary villi), cardinal veins (to embryo), and the vitelline artery (to the umbilical vesicle)

Answer 34

dorsal aorta

Question 35

The flow from dorsal aorta to cardinal veins feed the ____________ (intraembryonic/extraembryonic) tissues

Answer 35

intraembryonic

Question 36

The ___________ returns blood from tertiary villi back to the embryonic heart

Answer 36

umbilical vein

Question 37

By the end of the 4th week, the single “ventricle” rotates ____________ (clockwise/counterclockwise), such that the sinus venosus structures move to the right side of the heart and the atria posteriorly/superiorly

Answer 37

counterclockwise