Embryology: Folding and Body Cavities

Question 1

in the folding of the embryo, what three fold that happen at the sam time?

Answer 1

head, tail and transverse

Question 2

Before any folding occurs, what structure is most rostral?

Answer 2

septum transversum –> gives rise to Diaphragm

Question 3

Around what week does folding occur?

Answer 3

4th week

Question 4

As the neural tube moves forward, what begins to close?

Answer 4

rostral neuropore

Question 5

The notochord gets tucked ventrally and caudally, what now is the most rostral structure? most caudal?

Answer 5

from rostral - caudal:

intra-embryonic coelum –> heart tubes –> septum transversum

Question 6

Before folding, what three things sit in the prochordal mesoderm?

Answer 6

1) Septum transversum
2) Heart tube
3) Intra-embryonic coelum

Question 7

the membrane connecting the notochord with the prochordal mesoderm is?

Answer 7

oropharyngeal membrane

Question 8

What is the purpose of the oropharyngeal membrane?

Answer 8

acts as a “hinge” or pivot point and all structures will rotate around each other

Question 9

During this process a portion of yolk sac becomes engulfed as well and forms the?

Answer 9

foregut

Question 10

the remainder of the yolk sac that is not engulfed during folding goes?

Answer 10

it is squeezed out the ventral midline

Question 11

as the neural tube folds caudally, what moves?

Answer 11

the collecting stalk and alianois get shifted ventrally

Question 12

after the head fold, where is the oropharyngeal membrane located?

Answer 12

ventral to all structures ( heart tubes, IEC and septum transversum)

Question 13

what makes up the amniotic membrane?

Answer 13

EEM+Ectoderm

Question 14

What are the clinical significances of the head fold?

Answer 14

1) foregut formed
2) oropharyngeal membrane ventral toCNS
3) heart is ventral to CNS and gut
4) heart is dorsal to intraembryonic coelom
5) septum transversum is caudal to heart
6) rostral neuropore closes
7) ectoderm now covers rostral end of embryo while amniotic cavity surrounds the rostral end of embryo

Question 15

What are rostral neural tube defects?

Answer 15

anencephaly and exencephaly

Question 16

during the tail fold, the portion of the yolk sac that gets engulfed forms the?

Answer 16

hind gut

Question 17

the membrane connecting the notochord/neural tube with EEM is?

Answer 17

cloacal membrane

Question 18

the cloacal membrane will give rise to?

Answer 18

the anus

Question 19

the caudal portion of the hindgut that sticks out is called?

Answer 19

cloaca

Question 20

the cloaca will give rise to the?

Answer 20

rectum and urinary bladder

Question 21

What covers the caudal end of the embryo?

Answer 21

ectoderm

Question 22

What surrounds the caudal end of the embryo?

Answer 22

amniotic cavity

Question 23

consequences and clinical significance of the tail fold?

Answer 23

spina bifida and spinal dermal sinus

spinal dermal sinus- the epidermal cells end up proliferating in dura matter of spinal cord

Question 24

After the folds, EEM will complete surround the embryo except at one spot? where and what does it give rise to?

Answer 24

ventral to the midline

it will give rise to umbilical ring

Question 25

Before transverse folding, Mesoderm that is anterior to the IEC is called?

Answer 25

Somatic mesoderm

Question 26

Before transverse folding, Mesoderm that is posterior to IEC is called?

Answer 26

Splanchnic mesoderm

Question 27

What occurs during the lateral or transverse fold?

Answer 27

the body wall folds down on both sides to enclose the embryoonic cut and IEC

Question 28

The Somatic mesoderm swings down as ectoderm swings down and surrounds what structure?

Answer 28

mid gut

Question 29

What is a somatopleure?

Answer 29

somatic mesoderm of lateral plate + ECTOderm

Question 30

What is a spanchopleure?

Answer 30

splanchnic mesoderm of lateral plate + ENDOderm

Question 31

when mesenchymal cells (mesoderm) encouter a fluid filled space (like IEC)

Answer 31

epithelium, but since it is made of mesenchymal cells= mesothelium

Question 32

at the end of the transverse fold, the IEC surrounds what mesoderm?

Answer 32

splanchnic

Question 33

somatic mesoderm will give rise to?

Answer 33

PARIETAL, lining of body cavities

Question 34

splanchnic mesoderm will give rise to?

Answer 34

VISCERAL- outer layer of the organ

Question 35

Two fused layers of mesothelium is called?

Answer 35

Mesentery

Question 36

During the transverse fold, what is the IEC continuous with?

Answer 36

chronic cavity

Question 37

as the embryo starts to grow, the amniotic will expand and fuse with ?

Answer 37

amnion + chorion = amniochorionic membrane

Question 38

what is the umbilical ring?

Answer 38

where ectoderm meets amnion

Question 39

where do the umbilical vessels form?

Answer 39

in collecting stalk

Question 40

what vessels compose an umbilical cord?

Answer 40

2 arteries and 1 vein

Question 41

what are the contents and layers of the umbilius

Answer 41

1) many layers of EEM = collecting stalk 2) Allantois (located inside stalk) 3) umbilical BVs 4) yolk stalk (has its own layer of EEM)

Question 42

After transverse folding, what surrounds the yolk stalk?

Answer 42

IEC

Question 43

ectoderm and amniotic cavity cover the ventral embryo except at the?

Answer 43

umbilical ring

Question 44

definitive umbilicus has formed and is wrapped in?

Answer 44

amniotic membrane

Question 45

the transverse folding process gives rise to what structure?

Answer 45

midgut

Question 46

can the midgut still communicate outside the embryo?

Answer 46

yes, it connects with the residual yolk sac outside the embryo via yolk sac through vitelline duct

Question 47

What is gastroschisis?

Answer 47

means "split gut" - failure in the transverse folding process, allows contents of body cavities to communicate and herniate outside the embryo