Topic 5 & 6 Cardiac Flashcards
Where does fertilization occur
Fertilization occurs in the ampullary region of the fallopian tube
Sperm + Oocyte = Zygote
undergoes cell divisions
When does the zygote reach 2 cell stage?
about 30 hours post fertilization
When does the zygote reach 4 cell stage ?
at about 40 hours
When does the zygote reach 12-16 cell stage?
at about 72 hours (3 days)
The very first cells are called what?
Cells are called Blastomeres
After the 3rd cleavage, cells have maximized contact with each other and they ttart to undergo what?
Compaction
Cells separate into inner and outer cells.
16 cell stage-called what?
Morula
Had defined inner and outer cells.
Morula has defined what?
Had defined inner and outer cells.
Inner cells = inner cell mass (will become the embryo)
Outer cells = outer cell mass (will become the
trophoblasts, which will be the placenta)
Morula makes its way into the uterus, enlarges and becomes a what?
Blastocyst
How many days after fertilization does implantation occur?
6 day
What time frame can fertilization occur?
12-24 hours after ovulation
Morula enters uterine cavity
Fluid penetrates into the intercellular spaces of Inner Cell Mass.
Spaces become what?
a single cavity Blastocele
Morula enters uterine cavity
Fluid penetrates into the intercellular spaces of Inner Cell Mass.
What is the Embryo called at this point?
Embryo is called a Blastocyst at this point
Blastocyst is comprised of what 3 layers?
Trophoblast
Blastocele
Embryoblast
Trophoblast
outer covering
Formed from cells of the outer cell mass.
Cells flatten and eventually form the epithelial wall of the blastocyst
[BLASTOCYST layer]
Blastocele
Internal fluid filled space
[BLASTOCYST layer]
Embryoblast
Located at one pole
[BLASTOCYST layer]
Trophoblast and part of inner cell mass will become?
become the placenta
blastocyst is in the cell mass
Blastocyst remains free in the uterus for how long?
2 days
When implantation occurs - Trophpblastic cells go where?
Trophoblastic cells over the embryoblast pole penetrate between the epithelial cells of the uterine wall.
When implantation occurs - Blastocyst cells go where?
Blastocyst attaches to uterine epithelium, and subsequently the endometrium
Oriented so the inner cell mass is near the endometrium
At day 8 the Blastocyst is partially embedded
The Trophoblast cells over the embryoblast differentiate into what 2 layers?
Syncytiotrophoblast–multi-nucleated, outer zone no cell boundries
Cytotrophoblast –mononucleated cells, inner layer distinct cells
Both layers become part of the chorion
(one of the fetal membranes)
Synctiotrophoblast -
multi-nucleated, outer zone no cell boundries
[blastocyst partially embedded day 8, outer trophoblast]
Cytotrophoblast
mononucleated cells, inner layer distinct cells
[blastocyst partially embedded day 8, outer trophoblast]
At day 8 the Blastocyst is partially embedded
Inner cell mass–embryoblast, differentiates into what?
Hypoblast layer - Layer of small cuboidal cells adjacent to the blastocyst cavity
Epiblast layer -Layer of high columnar cells adjacent to amniotic cavity
Hypoblast
Layer of small cuboidal cells adjacent to the blastocyst cavity
[blastocyst partially embedded day 8m, inner cell mass]
Epiblast
Layer of high columnar cells adjacent to amniotic cavity
[blastocyst partially embedded day 8, inner cell mass]
Day 11-12 – Completely embedded
Cells of the Synctiotrophoblasts do what?
Capillaries are congested and dilated
Called Sinusoids
penetrate deeper into endothelial lining of maternal capillaries
Day 11-12 – Completely embedded
Capillaries are congested and dilated – what are they called?
Called Sinusoids
Day 11-12 – When completely embedded it causes blood to flow through the trophoblastic system, what is this the beginning of ?
Beginning of the uteroplacental circulation
Cytotrophoblast proliferates to form what 2 layers?
Amnion - Thin Protective membrane that surrounds the developing embryo.
Amniotic Cavity -Space, eventually filled with fluid.
Amnion
Thin Protective membrane that surrounds the developing embryo.
[CYTOTROPHOBLAST]
Gastrulation starts when?
starts at Day 8.
What is Gastrulation?
Process for establishing 3 germ layers, ICM differentiates.
- Ectoderm
- Endoderm
- Mesoderm
The 3 germ layers for Gastrulation do what?
These are the major embryonic tissues from which all tissues and organs of the body develop.
Gastrulation Starts with the formation of
what on the epiblast?
the primitive streak
By day 15-16, it is clearly visible as a narrow groove
Cells of the epiblast migrate to the primitive streak
Arrive and become like what? and do what?
“flask-like”
Detach from epiblast and slip beneath it
Epiblast is the source of the germ layers.
Inward movement causes what?
cause invagination
Cells that displace the hypoblast?
during invagination
Creates Endoderm
Others lie between the epiblast and the new endoderm are called?
(during invagination)
Mesoderm
Cells remaining in the epiblast are called?
during invagination
Ectoderm
Inner Cell Mass now called an Embryonic Disc as what starts to form?
(after invagination
amniotic cavity starts to form
Inner Cell Mass now called an Embryonic Disc as amniotic cavity starts to form.
–Layer of cells of the inner cell mass closest to the amniotic cavity?
Ectoderm
Inner Cell Mass now called an Embryonic Disc as amniotic cavity starts to form
–layers of inner cell mass that borders the blastocele
Endoderm
Inner Cell Mass now called an Embryonic Disc as amniotic cavity starts to form
–Lies inbetween the ectoderm and endoderm.
Mesoderm
Ectoderm Becomes:
Skin, teeth, mouth glands, nervous system, some endocrine glands.
Endoderm Becomes:
Epithelium of digestive tract, respiratory system, bladder, vagina, urethra
Mesoderm Becomes:
All connective tissue, the muscular, skeletal, lymphatic, and circulatory systems
Cardiovascular System appears around when?
in the middle of the 3rd week.
At this point the embryo is no longer able to survive via diffusion alone
The Cardiovascular System reaches a functional state when compared to others?
long before any of the other systems
Vascular system develops from a simple symmetrical plexus, into what?
an asymmetrical complex system of arteries, veins and capillaries.
Progenitor Heart Cells Lie where?
in the Epiblast
Adjacent to the cranial end of the primitive streak
Progenitor Heart Cells move through the primitive streak and into what?
splanchnic layer of the mesoderm
What cells form the Primitive Heart Field (PHF)?
Progenitor Heart Cells
Form a horse-shoe shaped cluster of cells
Primitive Heart Field (PHF): Specified on both sides to become:
Atria, LV, RV, Conus Cordis and Truncus Arteriosus
— Conus and Truncus come from the Secondary Heart field and show up around Day 20-21
Progenitor Heart Cells will form what 2 things?
blood islands and cardiac myoblasts
These will form blood cells and blood vessels
Blood islands unite and form what?
a horse-shoe shaped tube Endothelial cell lined
Surrounded by myoblasts
More blood islands appear bilaterally, parallel and close to the midline.
–Will form dorsal aortas
Intraembryonic Celom (Body Cavity) formed how?
Formed by the joining of small (initially isolated) spaces which appear in the lateral mesoderm
Intraembryonic Celom (Body Cavity) Bilateral cavities extend which way? and form what?
cranially and fuse with each other forming a horseshoe-shaped cavity
Intraembryonic Celom (Body Cavity) eventually becomes what?
pericardial cavity
Heart development starts and occurs where?
at the end of the 3rd week of gestation.
Occurs in the ventral region of the embryo, inferior to the foregut.
Scattered masses of angiogenic cells appear in the ______ derived from PHF.
Occurs where?
mesenchyme Occurs ventral (in front of) the intraembryonic celom
(Blood Islands) Scattered masses of angiogenic cells in the mesenchyme —
Anterior part of the celom will develop the what?
the pericardial cavity
Angiogenic cells form clusters (Blood Islands) which do what?
increase in size and number.
Acquire a lumen, unite and form a plexus of blood vessels
Angiogenic cells form clusters (Blood Islands that acquire a lumen, unite and form a plexus of blood vessels – from this plexus what develop?
bilateral endocardial tubes develop.
The Endocardial tubes unite to form a?
common tube Primitive Heart Tube
By Day 21-22, the single heart tube does what?
starts to beat
Heart tube continues to elongate – Cells are added from the secondary heart field to the cranial end of the tube, this process is essential for normal formation of what 4 things?
- Part of the RV, the Conus Cordis and the Truncus Arteriosus
- Also essential for looping
Heart tube continues to elongate – Cells are added from the secondary heart field to the cranial end of the tube, If lengthening doesn’t occur, this is where outflow tract defects come from – Examples (5)
DORT, VSD, TOF, PA, PS
While the heart tube is elongating, Other blood islands appear inferior to the
endocardial tubes, Eventually give rise to what, which will do what?
dorsal aortas
Will connect with the endocardial tubes
Establish the arterial end of the heart
Other end of the future endocardial tubes will make contact with the ________ and establish a venous pole.
vitelline veins (via the sinus venosus)
