Topic 17: Development II

Question 1

What happens after cleavage?

Answer 1

normal cell cycle resumes
cell division slows
animal body starts to take shape during next 2 stages of development:
- gastrulation
- organogenesis

Question 2

What is gastrulation?

Answer 2

morphological process by which hollow blastula becomes layered embryo (gastrula) with:

• a digestive tube
• embryonic germ layers

Question 3

What are the steps to gastrulation in sea urchins?

Answer 3

1. mesenchyme cells at vegetal pole migrate into blastocoel
2. invagination at vegetal pole
3. archenteron forms
4. archenteron extends across blastocoel
5. mouth formation

Question 4

What is invagination?

Answer 4

when the cells of the vegetal plate flatten and buckle and fold inward

Question 5

What are filopodia?

Answer 5

mesenchyme cells produce this at tip; they are thin extensions

Question 6

What are the steps to gastrulation in birds?

Answer 6

1. formation of epiblast and hypoblast
2. formation of primitive streak
3. formation of 3 germ layers

Question 7

What is a trophoblast?

Answer 7

outer single layer of cells

Question 8

What is the inner cell mass?

Answer 8

the cluster of cells that become an embryo

Question 9

What are the steps to gastrulation in humans?

Answer 9

1. implantation
2. formation of epiblast and hypoblast
3. formation of 4 extraembryonic membranes
4. formation of 3 germ layers

Question 10

What is organogenesis?

Answer 10

process of organ formation

Question 11

What is neurulation?

Answer 11

formation of the brain and spine

Question 12

What forms the notochord?

Answer 12

mesoderm

Question 13

What forms the nerve cord?

Answer 13

ectoderm

Question 14

What is induction?

Answer 14

the process by which cells stimulate or influence differentiation of neighboring cells

Question 15

What are the steps in neurulation?

Answer 15

1. formation of the notochord
2. formation of neural plate
3. formation of neural tube

Question 16

How does the neural plate form?

Answer 16

the notochord induces the ectoderm above it to thickem

Question 17

How does the neural tube form?

Answer 17

the neural plate rolls up

Question 18

What does the neural tube develop into?

Answer 18

the CNS
anterior portion -> brain
remainder -> spinal cord

Question 19

What happens to the notochord?

Answer 19

most of it disappears, some form vertebral discs

Question 20

Why does spina bifida happen?

Answer 20

it occurs when the neural tube doesn’t form properly

Question 21

What is the neural crest?

Answer 21

it’s between the neural tube and ectoderm

cells migrate -> nerves, teeth, skull, bones

Question 22

What are somites? What do they do?

Answer 22

blocks of mesoderm cells next to notochord

migrate -> segmented/repeated structures - ribs, vertebrae, muscless

Question 23

What happens during the first trimester?

Answer 23

the biggest changes for the mother and embryo

the implanted embryo secretes hCG and acts like LH on corpus luteum - maintains progesterone, estrogen secretion

Question 24

How does the placenta form?

Answer 24

when first implanted, the nutrients come directly from the endometrium
weeks 2-4 the triploblast mixes with endometrium to form the placenta

Question 25

What is the placenta?

Answer 25

an organ of exchange between mother and embryo - exchanges nutrients, gases, immunity, waste

Question 26

What connects the embryo to placenta?

Answer 26

the umbilical cord

Question 27

Identical vs fraternal twins

Answer 27

identical twins come from the same egg and sperm

fraternal twins come from 2 different eggs and sperms

Question 28

What happens during birth?

Answer 28

it begins with labor, then
uterine contractions to push the fetus and placenta out
it is regulated by prostaglandins, hormone like estradiol and oxytocin

Question 29

What are the stages of birth?

Answer 29

1. dilation of cervix
2. explusion: delivery of the infant
3. delivery of the placenta