embryology Flashcards
week that gastrulation occurs
week 3
week that heart development begins
week 3
what is the first organ that begins to function
heart
define gastrulation
process of transforming a bilaminar disc (hypoblast and epiblast) into a trilaminar disc (ectoderm, mesoderm, and endoderm)
describe the migration of cells during gastrulation
ectoderm: epiblast cells that do not migrate
epiblast cells that migrate move towards the primitive streak where they invaginate and pass the epiblast layer to become mesoderm or continue downward and replace hypoblast to become endoderm
some epiblast cells migrate through the primitive node to become the notochord
define primitive streak
on the surface of the epiblast layer and is the site for invaginating epiblasts that give rise to the mesoderm and endoderm layers
define primitive node
raised area that surrounds the primitive pit and is located at the cephalic end of the primitive streak
list areas of mesoderm
paraxial, intermediate, and lateral plate (which has somatic and splanchnic layers)
from which area does the cardiovascular system arise
splanchnic lateral plate mesoderm and neuroectoderm (neurocrest cells)
how are neural crest cells important to the cardiovascular development
important in development of the outflow tract of the heart (aorta and pulmonary trunk)
how is the primary heart field developed
cardiac progenitor cells emerge from the primitive streak and migrate bilaterally to the cranial end of the embryo wherere they reside in the splanchnic layer of the lateral plate mesoderm at the most cranial end
how is secondary heart field formed
derives from splanchnic mesoderm of the pharynx and is regulated by neural crest cells (secondary heart field is responsible for lengthening the outflow tract)
two types of body folding, what week does it occur
week 4
cephalocaudal folding: displaces primitive heart inferiorly into thorax
lateral folding: closes anterior wall and endocardial heart tubes become single heart tube
precursor of heart tube
blood islands
ectopia cordis
lateral folding defect
lateral folds do not meet to close ventral (anterior) wall of thorax, heart is outside of body
may be combinded with lateral folding defects of the ventral abdomen
what day does the heart spontaneously beat
day 22
list 5 major dilations cranial to caudal
truncus arteriosus bulbus cordis primitive ventricle primitive atrium sinus venosus (l. and r. sinus horn)
left sinus horn gives rise to:
coronary sinus and oblique vein
right sinus horn gives rise to:
siuns venarum and valves of the coronary sinus and IVC
primitive atrium gives rise to:
trabeculated, muscular components of atria (pectinate muscle)
primitive ventricle gives rise to:
trabeculated, muscular components of the ventricle
bulbus cordis gives rise to:
smooth portions of the ventricles (conus arteriosus, aortic vestibule)
truncus arteriosus gives rise to:
pulmonary trunk and aorta
describe process of cardiac looping
cranial end: folds caudally, anteriorly, and right
caudal end: folds cranially, posteriorly, and left
*apex ultimately points to the left
dextocardia
cardiac looping abnormality
apex of heart points to the right side
describe shunting of sinus venosus
originally: left and right horn each have common cardinal vein, umbilical vein, and vitelline vein
eventually left to right shunting occurs so that venous drainage into to left and right sinus horn is not symmetrical
left horn becomes cornonary sinus and oblique vein
right horn becomes valves of the inferior vena cava and coronary sinus and the sinus venarum
where does the umbilical vein carry blood from
placenta
where does vitelline vein carry blood from
yolk sac and G.I.
how is sinus venosus incorporated into heart
it becomes the smooth wall of the right atrium or the sinus venarum which is between the superior and inferior vena cava
how are pulmonary veins incorporated into the heart
first a single vein branches off of left atrium which divides and divides again resulting in 4 veins and gives rise to smooth wall of right atrium
list all of the pieces that must come tofether for proper separation and alignment of the chambers and outflow tract to occur
endocardial cushions of the atrioventricular region septum primum septum secundum conotruncal ridges of the outflow tract muscular ventricular septum membranous ventricular septum neural crest cells
endocardial cushions
located in atrioventricular and conotruncal regions
required for complete septation of the atria, atrioventricular canal, ventricles, and outflow tract
describe septation of atria
septum primum grows from roof inferiorly towards cushions (ostium primum is opening between cushions and growing septum premum)
ostium secundum forms by cell death in upper portion of septum primum (allows blood to bypass lungs)
septum secundum grows to the right of septum primum and is crescent shaped, leaving foramen ovale to allow blood flow
septum primum is valve of foramen ovale and closes to become fossa ovalis after birth
list causes for atrial septal defect
ostium secundum defect: 70%, most common, escessive cell death of septum prmum or lack of septum secundum
ostium primum defect: 20%, failure of septum primum and endocardial cushions to fuse
sinus venosous defect: 10%, usually associated with partial anamalous pulmonary venous return
soronary sinus defect: 1%
patent foramen ovale
no structural development, the foramen ovale just doesnt close at birth
atrroventricular septum formation
fusion of endocardial cushions
persistent common atrioventricular canal
atrioventricular septum is not formed causing both an ASD and VSD, cushions do not close
tricuspid atresia
right atrioventricular canal does not develop
always accompanied with: foramen ovale patency, VSD, underdeveloped right ventricle, left ventricular hypetrophy