Lecture 3: heart development Flashcards
progenitor heart cells migrate and form
horseshoe-shaped primary heart field in the splanchnic layer of the lateral plate mesoderm
primary heart field gives rise to
left and right sides of the hear, atria, left ventricle, and part of the right ventricle
secondary heart field gives rise to
the remainder of the right ventricle and the outflow tract (conus cords and trunks anteriosus)
hemangioblasts
- once in the cardiac crest differentiate into hemangioblasts
- form blood cells and blood islands by vascular endothelial growth factor
endocardial heart tubes
- formed by islands of hemagioblasts
- lined with endothelium
merging of the heart tube
- as the embryo folds laterally the caudal regions of the heart tube merge
- inner endothelial lining and outer myocardial layer
cardiac jelly
- extracellular matrix secreted by the myocardium
- separates the endothelium from the myocardium
dorsal mesocardium
-initially attaches the heart tube to the dorsal side of the pericardial cavity
transverse paricardial cavity
formed by the break down of the central portion of the dorsal mesocardium
importance of the breakdown of the dorsal mesocardium
liberated the tube for further growth and bending
cranial end of the cardiac tube is attached to
the pharyngeal arches
caudal end of the cardiac tube is embedded in
the septum transversum
five heart dialations
- sinus venous
- primitive atrium
- primitive ventricle
- bublus cordis
- truncis arteriosus
sinus venous
left and right sinus horns that initially receive three paired veins
primitive atrium
forms traberculated part of the right atrium and all of the left atrium
pimitive ventricle
forms trabeculated left ventricle
atrioventricular canal
separates the primitive atrium and the primitive ventricle
bulcus cordis
- proximal: right ventricle
- distal (conus cordis): smooth part of the right (conus arteriousus) and left ventricle (aortic vestibule)
truncis arteriosus
proximal ascending aorta, pulmonary trunk
heart loops to the
right
area of rapid heart growth
proximal bulbus cordis and primitive ventricle
cardiac looping
displacement of the proximal bulbous cordis
caudally, ventrally, and to the right
cardiac looping
displacement of the primitive ventricle
to the left
cardiac looping
displacement of the primitive atrium
dorsally and cranially
results of cardiac looping
-initial caudal inflow (sinus venous) of the heart is positioned dorsal to the outflow track (truncus)
3 initial initial pairs of veins that enter the sinus
- vitelline veins (de-oxygenated)
- umbilical veins (oxygenated)
- common cardinal veins (de-oxygenated)
vitelline veins
arise from the yolk sac and drains the gut tube:
- portion of the inferior vena cava
- portal veins
- splenic vein
- superior mesenteric vein
- inferior mesenteric vein
umbilical vein
umbilical vein carries oxygenated blood form the placenta to nourish the embryo
- right regresses, left is left
- umbilical vein carries oxygenated blood from the placenta to the embryo
cardinal veins
anterior and posterior cardinal veins form the main venous drainage system of the embryo
- vessels rearrange to give rise brachiocephalic vein
- superior vena cava
- portion of the inferior vena cava
remnants of the left sinus horn
oblique vein of the left atrium and coronary sinus
sinus venarum
smooth walled portion of the right atrium caused from the incorporation of the right horn
crista terminalis
dividing line between the traberculated wall (from primitive atrium) and smooth wall (from right sinus horn)
initial outflow of blood order
trunks arterious- aortic sac- aortic arch vessels- paired dorsal aorta
development of the atrioventricular septum
- endocardial cushions form on the dorsal and ventral walls of the atrioventricular canal
- cushions meet and fuse resulting in 2 atrioventricular canals
cardiac cushion function as primitive valves
- blood hollows out tissue
- mesenchymal tissue becomes fibrous forming atrioventricular valves which connect to the papillary muscles
septation of the atria
- primary septum is the valve of the foramen ovale
- secondary septum forms foramen ovale
what happens to the septation of the atria after birth?
fall in pressure in right atrium will result in valve of foramen oval pressing agains the secondary septum
formation of the primary septum
forms on the dorsal roof of the atrial chamber and grows toward the atrioventricular canal
foramen primum
space between the caudal edge of the septum primum and endocardial cushions which serves as a shunt
-it’s later obliterated
foramen secundum
formed by coalescence of small ruptures in the septum primum
formation of the secondary septum
- a second crescent shaped ridge of muscle forms
- it does not completely close leaving an opening called the foramen ovale
partitioning of the outflow tract
- truncus ridges partition the pulmonary and aortic channels
- ridges are largely derived from neural crest mesenchyme that migrate through the pharyngeal apparatus to the developing heart
development of the truncus ridges
- right and left grow from the walls
- develop in a spinal configuration
- fuse with one another in a cranial to caudal direction
- forming the truncal septum(aortic pulmonary septum)
separation of the ventricles
- muscular inter ventricular septum
- membranous interventricular septum
muscular inter ventricular septum
- protrusion in the lumen as the right and left walls expand
- grows towards the endocardial cushions but stops before reaching them
interventricular foramen
space between the muscular ventricular septum and the endocardial cushions
membranous interventricular septum
- results in complete separation of ventricles
- muscular septum fuses with conotruncal septum and endocardial cushion
tissues involved in membranous part of ventricular septum
- right and left conus cordis swellings
- endocardial cushion
- nueral crest cells
fetal circulation
- Umbilical vein carries oxygenated blood (~ 80% O2 saturation) from maternal placenta to the fetus
- In the liver, most blood flows through the ductus venosus directly to the inferior vena cava (a small amount will enter the liver sinusoids to nourish the tissues of the liver)
- Blood enters the right atrium of the heart- most passes directly to the left atrium via the oval foramen-blood enters the left atrium to the ascending aorta (heart musculature and head and neck are well oxygenated)
- Pulmonary resistance is high, blood that has entered the right atrium and pulmonary trunk is shunted by the ductus arteriousus to the descending aorta
- Blood flows to the back to the placenta through the umbilical arteries
circulation after birth
- and 2. Closure of umbilical vein and ductus venosus- several minutes after birth, adult remnant is the ligamentum teres (umbilical vein) and ligamentum venosum (ductus venosus)
- Pressure changes between the two atria cause the initial closing of the oval foramen. Fusion of the primary and secondary septa is usually complete three months after birth (adult structure is foramen ovale)
- The ductus arteriosus closes immediately after birth- obliterated ductus arterious is the ligamentum arteriousus
- Contraction of smooth muscle cells in the walls of the umbilical arteries result in closure a few minutes after birth. Distal parts of the arteries form the medial umbilical ligaments, proximal portions remain open as the superior vesical arteries
adult structure for the umbilical arteries
medial umbilical ligament and superior vesical arteries
adult structure for the umbilical vein
ligamentum teres
adult structure for the ductus venosus
ligamentum venosum
adult structure for the ductus arteriosis
ligamentum arteriosum
adult structure for the foramen ovale
fossa ovalis
