L17. Developmental Biology Flashcards
What are organs derived from?
Organs are derived from 2 or more basic tissues
What are the 3 primary germ layers?
- ectoderm
- mesoderm
- endoderm
What is differentiation?
The development of specialized cell types. cells become more specialized for a specific function
What are stem cells?
Cells that
- have potency ( can differentiate into other cell types)
- create more stem cells (self-renew)
What is potency?
Refers to the possible cell types that a specific cell can generate during normal development
What are the different types of potency a cell can posses?
- totipotent: can give rise to any cell type
2. pluripotent:can give rise to numerous cell types
What are the major types of stem cells? Are they totipotent or pluripotent
- embryonic stem cells: totipotent
- organ stem cells: pluripotent
- induced pluripotent stem cells: pluripotent
How are stem cells regulated
By their microenvironment
Explain the stem cell niche
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
What is induced pluripotent stem cells?
Induce embryonic stem cell qualities in cells that are non-pluripotent
What is the developmental rule of thumb?
progression to a more differentiated state results in less potency
What gives rise to all of the tissues in the embryo
- stem cell proliferation
2. daughter cell differentiation
What are the 3 period of pre-natal development?
- pre-embryonic
- embryonic development
- fetal period
When is the pre-embryonic state?
first 2 weeks
What are the characteristics of the pre-embryonic state?
- gastrulation begins
- implantation ad transport of the zygote
When is the embryonic development state?
3-9 weeks
What are the characteristics of the embryonic state?
- gastrulation is completed
- neurulation begins and organ formation starts
- umbilical cord and extra-embryonic membrane forms
When is the fetal period stage?
9 weeks to birth
What are the characteristics of the fetal period stage?
growth and further organ specialization
When do we reach the 2-cell stage?
30 hours
When do we reach the 8-cell stage?
3 days
How many days till the
a. morula
b. blastula
c. implantation starts
d. implantation is completed
e. gastrulation
a. 4 days
b. 5days
c. 6-7 days
d. 9 days
e. 14-15 days
Write down the process from fertilization->gastrulation
oocyte->2-cell stage->8-cell stage ->morula->blastula->implantation->gastrulation
Identify the embryoblast and trophoblast
(pg 22 of L17)
What does the embryoblast differentiate into?
hypoblast
epiblast
(becomes embryo and some extraembryonic tissue)
What does the trophoblast differentiate into?
syncytiotrophoblast
cystotrophoblast
(becomes extra-embryonic tissue)
Identify all the parts in PG 22 of notes L17
ie. where the hypoblast, epiblast,synctiotrophoblast and cystotropblast
pg 22 L17
Why doesn’t menstruation occur after fertilization
the synciotrophoblast secretes hCG
What does hCG do?
like lutenizing hormone
maintains corpus luteum -maintains high levels of progesterone and estrogen preventing menstruation
What is the function of the synciotrophoblast
- secrete hCG hormones
- release proteases/proteolytic enzymes that break down ECM of endometrium wall
- finger like projections extend into uterus to form lacunae.
Identify all the structures ( hypoblast,epiplast ,amniotic fluid,synchytrophoblast and cytotrophoblast) in day 8 pg 24 of L17
pg24 in L17
what happens with the synchiotrophoblast after 9 days?
- surrounds bastocyst
- forms trophoblastic lacunae (gaps that maternal blood will flow into)
Draw what happens 9 days after fertilization ( page 25 L17
pg 25 L17
What happens with the epiblast after 9 days after fertilization
epiblast forms 2 layers around growing amnionic cavity ->amnioblasts +epiblast
What happens with the hypoblast cells 9 days after fertilization
hypoblast cells start to migrate within the cytotrophoblast->Heuser’s membrane forms
What happens from Day10-11
- 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
