L17. Developmental Biology

Question 1

What are organs derived from?

Answer 1

Organs are derived from 2 or more basic tissues

Question 2

What are the 3 primary germ layers?

Answer 2

1. ectoderm
2. mesoderm
3. endoderm

Question 3

What is differentiation?

Answer 3

The development of specialized cell types. cells become more specialized for a specific function

Question 4

What are stem cells?

Answer 4

Cells that

• have potency ( can differentiate into other cell types)
• create more stem cells (self-renew)

Question 5

What is potency?

Answer 5

Refers to the possible cell types that a specific cell can generate during normal development

Question 6

What are the different types of potency a cell can posses?

Answer 6

1. totipotent: can give rise to any cell type

2. pluripotent:can give rise to numerous cell types

Question 7

What are the major types of stem cells? Are they totipotent or pluripotent

Answer 7

1. embryonic stem cells: totipotent
2. organ stem cells: pluripotent
3. induced pluripotent stem cells: pluripotent

Question 8

How are stem cells regulated

Answer 8

By their microenvironment

Question 9

Explain the stem cell niche

Answer 9

Stem cells contact somatic hub cells
The hub cells express a ligand ( unpaired protein)
Unpaired protein signals to stem cells inhibiting differentiation
Stem cells divide perpendicular to the hub and the further daughter cells no longer receives the signal and differentiates

Question 10

What is induced pluripotent stem cells?

Answer 10

Induce embryonic stem cell qualities in cells that are non-pluripotent

Question 11

What is the developmental rule of thumb?

Answer 11

progression to a more differentiated state results in less potency

Question 12

What gives rise to all of the tissues in the embryo

Answer 12

1. stem cell proliferation

2. daughter cell differentiation

Question 13

What are the 3 period of pre-natal development?

Answer 13

1. pre-embryonic
2. embryonic development
3. fetal period

Question 14

When is the pre-embryonic state?

Answer 14

first 2 weeks

Question 15

What are the characteristics of the pre-embryonic state?

Answer 15

• gastrulation begins

- implantation ad transport of the zygote

Question 16

When is the embryonic development state?

Answer 16

3-9 weeks

Question 17

What are the characteristics of the embryonic state?

Answer 17

• gastrulation is completed
• neurulation begins and organ formation starts
• umbilical cord and extra-embryonic membrane forms

Question 18

When is the fetal period stage?

Answer 18

9 weeks to birth

Question 19

What are the characteristics of the fetal period stage?

Answer 19

growth and further organ specialization

Question 20

When do we reach the 2-cell stage?

Answer 20

30 hours

Question 21

When do we reach the 8-cell stage?

Answer 21

3 days

Question 22

How many days till the

a. morula
b. blastula
c. implantation starts
d. implantation is completed
e. gastrulation

Answer 22

a. 4 days
b. 5days
c. 6-7 days
d. 9 days
e. 14-15 days

Question 23

Write down the process from fertilization->gastrulation

Answer 23

oocyte->2-cell stage->8-cell stage ->morula->blastula->implantation->gastrulation

Question 24

Identify the embryoblast and trophoblast

Answer 24

(pg 22 of L17)

Question 25

What does the embryoblast differentiate into?

Answer 25

hypoblast
epiblast
(becomes embryo and some extraembryonic tissue)

Question 26

What does the trophoblast differentiate into?

Answer 26

syncytiotrophoblast
cystotrophoblast
(becomes extra-embryonic tissue)

Question 27

Identify all the parts in PG 22 of notes L17

ie. where the hypoblast, epiblast,synctiotrophoblast and cystotropblast

Answer 27

pg 22 L17

Question 28

Why doesn’t menstruation occur after fertilization

Answer 28

the synciotrophoblast secretes hCG

Question 29

What does hCG do?

Answer 29

like lutenizing hormone

maintains corpus luteum -maintains high levels of progesterone and estrogen preventing menstruation

Question 30

What is the function of the synciotrophoblast

Answer 30

1. secrete hCG hormones
2. release proteases/proteolytic enzymes that break down ECM of endometrium wall
3. finger like projections extend into uterus to form lacunae.

Question 31

Identify all the structures ( hypoblast,epiplast ,amniotic fluid,synchytrophoblast and cytotrophoblast) in day 8 pg 24 of L17

Answer 31

pg24 in L17

Question 32

what happens with the synchiotrophoblast after 9 days?

Answer 32

• surrounds bastocyst

- forms trophoblastic lacunae (gaps that maternal blood will flow into)

Question 33

Draw what happens 9 days after fertilization ( page 25 L17

Answer 33

pg 25 L17

Question 34

What happens with the epiblast after 9 days after fertilization

Answer 34

epiblast forms 2 layers around growing amnionic cavity ->amnioblasts +epiblast

Question 35

What happens with the hypoblast cells 9 days after fertilization

Answer 35

hypoblast cells start to migrate within the cytotrophoblast->Heuser’s membrane forms

Question 36

What happens from Day10-11

Answer 36

• erosion of maternal capillaries occur, maternal blood fills with trophoblastic lacunae
• space between hypoblast and Heuser’s membrane->primary yolk sac
• extraembryonic reticulum invaded by epiblast cells called embryonic mesoderm