L18. Early Development 2

Question 1

What does the syncytiotrophoblast do?

Answer 1

1. produce hCG ( stop menstruration by keeping estrogen and progesterone high)
2. produce proteolytic enzymes that digests and invade the endometrium and surround the blastocyst
3. forms trophoblastic lacuna (gaps that allow maternal blood to flow through)

Question 2

What are the 2 layers that grow around the amnionic cavity?

Answer 2

1. epiblasts

2. amnioblast

Question 3

What forms the Heuser membrane?

Answer 3

hypoblast cells that start to migrate

Question 4

What surrounds the primary yolk sac/

Answer 4

1. Heuser membrane

2. Hypoblast

Question 5

What is the extraembryonic mesoderm?

Answer 5

1. extraembryonic reticulum is invaded by the epiblasts cells
2. extraembryonic mesoderm lines along the Heuser’s membrane and the cytotrophoblast
3. separates the cytitrophoblasts from the amnioblast

Question 6

What is the chronic cavity?

Answer 6

Forms between the 2 layers of mesoderm as fluid fills in the gaps

Question 7

What happens on day 13 of implantation?

Answer 7

1. Heuser’s membrane and connected extraembryonic mesoderm elongates and buckles
2. definitive yolk sac forms as remnants of the primary yolk sac

Question 8

What are the characteristics at the start of gastrulation?

Answer 8

1. syncitiotrophoblasts have started to establish the placenta
2. amniotic cavity forms
3. definitive yolk sac forms
4. embyo proper is formed
5. has 2 layers; hypoblast and epiblast

Question 9

How does the placenta form?

Answer 9

The extraembryonic mesoderm digs deeper into the synciyotrophoblast and thus it pushes down the cytotrophoblast

Question 10

What are the 2 contributing components to the placenta?

Answer 10

1. maternal component: decidua basalis

2. fetal component: chorionic villi

Question 11

What is the function of the placenta?

Answer 11

allows gas, nutrients and waste exchange.

blood comes close to one another but do not contact.

Question 12

What are the 4 barriers between the mother’s and fetuses blood?

Answer 12

1. synctiotrophoblast
2. cytotrophoblast
3. connective tissue surrounding the blood vessel
4. epithelial of the blood vessel

Question 13

What is the function of the amnion?

Answer 13

protects the embryo, eliminates waste

Question 14

What is the function of the yolk sac?

Answer 14

produces blood until the liver forms
germ cells form here
migrate to gonads

Question 15

What is gastrulation?

Answer 15

rearrangement of cells into the primary germ layers (mesoderm, endoderm and ectoderm)

Question 16

Identify all the components on page 3 part 2

Answer 16

page 3 part 2

Question 17

What forms the embryo?

Answer 17

epiblast

Question 18

What is the first evidence of gastrulation?

Answer 18

the appearance of the primitive streak

Question 19

Identify the primitive peak, primitive node and primitive groove

Answer 19

They form the primitive streak ( page 3 part 3)

Question 20

How does the endoderm form?

Answer 20

1. cells in the middel of the epiblast ingress

2. ingressing cells displace the hypoblast, the endoderm forms

Question 21

What does the endoderm form

Answer 21

1. lines the gut wall

2. generates visceral tissues

Question 22

What happens after the formation of the endoderm

Answer 22

1. second set of cells ingress from the epiblast to fomr the mesoderm
2. mesoderm forms the muscle,bones and blood vessels

Question 23

After the formation of the endoderm and mesoderm what happens?

Answer 23

The epiblast forms the ectoderm

Question 24

What is the epithelial mesenchymal transformation?

Answer 24

1. loss of adhesion between cells at the primitive streak
2. transformation of cells at the primitive peak to mesoderm
3. Slug a DNA-binding transcription factor regulates this gene expression of the primitive streak
4. expression of Slug causes adhesion lost between cells

Question 25

What happens to the esoderm on day 16

Answer 25

1. mesoderm migrates beyond the primitive streak 2. mesoderm fills the gap between all the ectoderm and endoderm 3. migration of mesoderm between ectoderm and endoderm

Question 26

What is the fate of the ectoderm?

Answer 26

skin,hair,lenses of eyes, internal and external ear,nose, sinuses,mouth,anus,tooth enamel, all pats of the nervous system,mammary glands

Question 27

What is the fate of the mesoderm?

Answer 27

Middle cell layer of the embryonic disc and precursor to the muscles, bones, lymphatic tissue, spleen, blood cells,heart and lungs, reproductive and excretory system

Question 28

What is the fate of the endoderm?

Answer 28

it forms the inner cell layer of the embryonic disc which forms the lining of the lungs, the tongue,tonsils, urethra and associated glan, bladder and digestive system

Question 29

What are the 3 mesodermal regions?

Answer 29

1.paraxial 2. intermediate 3.lateral planes

Question 30

What does the lateral plane of the mesoderm form

Answer 30

somatopleure (dorsal) | splanchnopleure (ventral)

Question 31

When does the mesoderm start to differentiate

Answer 31

as the neural late buckles inwards

Question 32

What does the paraxial mesoderm differentiate into

Answer 32

Somites

Question 33

What are somites

Answer 33

Somites are brick like blocks that form the neural tube

Question 34

What is neurulation

Answer 34

formation of the nervous system

Question 35

What is induction

Answer 35

process whereby one cell or group of cells influences the developmental fate of another

Question 36

What induces the formation of the nervous system

Answer 36

specialized mesodermal structure (notochord)

Question 37

Describe neurulation

Answer 37

- formation of the neural tube 1. neural plate (specialized epidermal tissue) buckles inward ,forming the neural tube 2. neural groove forms and the neural folds fuse dorsally and seal off the neural tube 3. neural tissue is initially ectodermal- gows cranially from the primitive node 4. primtive node does not really move backwards , the embryo grows forward

Question 38

Describe somitogenesis

Answer 38

1. growth anterior of the primitive nodes 2. neural tubes and somites form in area aterior of primitive node 3. neural tube will form the spinal cord

Question 39

What do somites form

Answer 39

muscles, limbs,vertebrae

Question 40

What does the neural tube form

Answer 40

Forms the spinal cord

Question 41

Describe the process of patterning in the neural tube?

Answer 41

1. Bone morphogenic proteins that are prominent at the dorsal end of the neural tube form a downward gradien 2. sonic hedgehog proteins at the notochord are produced ventrally and form an upward gradient ( towards the forsal end) 3. the relative amount of BMP and Shh in neural tube determines which transcription factor gets expressed in that cell. 4. grid of different expressed transcription factors in the neural tube 5. each transcription factor domain has progenitor cells that will eventually become neurons