Peds Test 2 Flashcards
Fertilization
occurs in fallopian tube
sperm+oocyte= zygote (cell division starts)
Blastomeres
zygote becomes blastomere as cells cells get smaller with increase in number, still in fallopian tube
Compaction
after 3rd cleavage (8 cell stage)= the cells can’t all contact each other, so it undergoes compaction. cells separate into inner and outer cells (where embryonic development starts)
Morula
at 16 cell stage, makes its way to end of fallopian tube
inner cell mass= becomes embryo
outer cell mass= becomes trophoblasts (eventually placenta)
Blastocyst
- once in uterus
- enlarges and is free floating
- fluid penetrates intercellular spaces of inner mass- creates space called Blastocele and inner mass is pushed to one pole
Blastocyst is comprised of
- trophoblast= outer covering, cells flatten and become epithelial wall (will become placenta)
- blastocele= internal fluid filled space
- embryoblast= inner cell mass (becomes embryo)
Implantation
trophoblastic cells over embryo blast pole penetrate between epithelial cells/endometrium of uterine wall (attached by L-selectins and carbohydrate receptors)
Trophoblast differentiates into 2 layers
1) syncytiotrophoblast- multi nucleus, no cell boundaries
2) cytotrophoblast- 1 nucleus, distinct cells (divides and migrates into syncytiotrophoblasts)
- -both beomce part of chorion (one of the fetal membranes)
Embryoblast differentiates into 2 layers
1) hypoblast layer (entoderm)- cuboidal next to blastocele
2) epiblast layer (ectoderm)- columnar next to amniotic cavity (small cavity within the epiblast)
Cytotrophoblast proliferates to form 2 things
1) amnion- thing productive membrane that strands embryo
2) amniotic cavity- space
Gastrulation
process establishing 3 germ layers from Inner Cell mass
-ectoderm, endoderm, mesoderm (these are the major embryonic tissues from which all tissues and organs of the body develop)
Gastrulation Steps
1) formation of primitive streak- cells migrate to streak on epiblast
- this is regulated by fibroblast growth factor 8 (FGF8)= made by streak cells= decreases E-cadherin = decrease stickiness of cells so cells slip between hypoblast and epiblast layers
–cells displacing hypoblast= endoderm (was entoderm)
–cells between = mesoderm
–cells on epiblast= ectoderm
===embryonic disc
Progenitor Heart Cells
lie in epiblast, adjacent to cranial end of primitive streak
- form primitive heart field= comprised of blood islands, which form endocardial tubes (lined with myoblasts)= unite to form primitive heart tube= tube elongates and secondary heart field cells added to cranial end
- lays on top of intraembryonic celom (which becomes pericardial cavity)
- bld islands appear inferior= dorsal aortas
- other end attaches to vitelline veins via sinus venous
Primary Heart Field vs. Secondary
primary= atria, LV, RV
secondary= RV, conus corps, trunks arteriosus (outflow tracts)
Happens with:
–Serotonin (5HT)= left side- initiates R/L patterning (PITX2 gene)
– Monoamine Oxidase = right side- degrades serotonin on right side
Bending directions of Heart Tube
cephalic part= forward, down, right
caudal part= back, up, left
-bulges into pericardial cavity
-oriented so atrium and sinus venous lie superior to bulbs cords, ventricle, and dorsal aorta
Regions become? Dorsal Aorta/Aortic Sac, Bulbus Cordis, Primitive Ventricle, Atrioventricular Sulcus, Paired Primitive Atria, Sinus venosus
Dorsal Aorta/Aortic Sac=aortic arch/outflow tract Bulbus Cordis- RV Primitive Ventricle- LV Atrioventricular Sulcus- AV valves Paired Primitive Atria- atria Sinus venosus- SVC, IVC
Diverticula
appear on front of endocardial tube and around primary inter ventricular foramen (on LV and 1/3 of bulbus)
- trabeculae inside leads to valves, chordeae tendenie, papillary muscles, and AV valves
Ventricle Chamberization
1) division of AV Canal into R and L AV orficice via endocardial cushions (membrane)
2) Ventricular Septation- upward growth of muscular ridge at inter ventricular foramen
Endothelial Cushions
develop in AV Canal and Conotruncal regions
-assist in membrane septum, AV canal, valves, Aortic and Pulm channels
3 Goals for division of the AV canal with cushions
1) form barrier between atria and ventricles
2) R and L division of canal
3) eventually occupied with mitral and tricuspid valves
Atrial Septation
1) sickle shaped crest grows down from roof of the common atrium= Septum Primum (extends down to meet cushions) = doesn’t connect all the way leaving a space= Ostium Premium (then cushion grows and closes it)
2) apoptosis makes holes in upper part of Septum Primum= Ostium Secundum
3) second crest grows down from roof= Septum Secundum= which overlaps the Ostium Secundum= but leaves another hole= Foramen Ovale
final blood flow is R to L shunt through foramen ovale and through septum secundum
Outflow Tract Septation
-opposing cushions form in truncus
—one from right superior wall= grows distally and left
—one from left inferior wall= grows distally and right
——both grow towards aortic sac, twist around and fuse, forms aorticopulmonary septum (aka forms septum in truncus to make aorta and pulm artery)
-in Conus Cordis, cushions grow from right dorsal and left ventral walls (grows towards each other and distally)= unites with truncus septum
===divides conus into anterolateral (RV) outflow and posteromedial (LV) outflow tracts
AV Valve Formation
AV orficis is surrounded by local proliferations of mesenchymal tissue= remained attached to ventricular wall, muscular tissue degrades and replaced by connective tissue
Semilunar Valves Formation
small tubercles found on truncus swellings (and then hollow out on upper surface
