12. Cardiovascular System Flashcards
Umbilical blood vessels
2 arteries: deoxygenated from fetus to placenta
1 vein: oxygenated from placenta to fetus
Heart folding
ventral
During transition from amniotic cavity to umbilical vesicle a horseshoe shaped gap forms in cranial region (intraembryonic coelom)
Cranial part of the gap (pericardial cavity) is above the cardiogenetic plate in front of embryo
The coelom has no connection to extraembryonic coelom (chorionic cavity)
Cranial primordium rotates 180 degrees with pericardial cavity
Cardiac primordium lies dorsally to pericardial cavity
Pericardiac cavity bends over forwards and encloses cardiac primordium in the front.
Dorsally the cardiac primordium forms the two layers of the pericardiac bilaminar structure of a folded envelope, mesocardium.
cranial folding
brings heart into primitive thoracic region
yolk sac becomes part of gut tube, forms vitelline duct
allantois forms within connecting stalk
Heart development
Cardiac progenitors derived from cranial mesoderm
2 thin-walled endocardial tubes emerge (Caudal continuation of first aortic arches)
Fusion anterior side to form primitive heart tube
Extracellular matrix in between epimyocardium and endocardial tubes (ardiac jelly
Cardiac jelly involved in cardiac looping
Splanchnic/visceral mesoderm forms myocardium
Surrounding mesenchyme (secondary heart field) thickens to form epicardium (over myocardium): progenitor source
Coronary vasculature forms between myocardium and epicardium
Tubular heart elongates, develops dilations or sacculations
development veins and arteries
Contribution of blood islands from yolk sac to dorsal aorta
Aorta and sinus horn (inflow) start to develop
Blood vessels first appear solid cell clusters (angioblasts) that get a lumen and form pairs of longitudinal vessels
- Angioblasts arise from mesoderm (splanchnic and chorionic), mesenchyme (yolk sac and umbilical), which differentiates into blood islands (blood and blood cells (rest in vessels: vasculogenesis)
Aortic arches continue anterior and run ventrally
Dorsal aorta: supply cranial to caudal
after 4 weeks: rearrangement in arteries (6 arches)
- 1 and 2: disappear by 29 days
- 3: carotid arteries (head region)
- 4: left aortic arch, righ subclavian (arms (& head/thorax)
- 5: never forms
- 6: pulmonary arch
Vitelline + umbilical arteries form in yolk sac
Coronary arteries form from epicardial cells / sinus venosus (dedifferentiation)
4 weeks
3 systems of paired veins drain into heart
- Vitelline veins
- Umbilical veins (from chorion, placenta)
- 2 at start, one degenerates
- Cardinal veins
Sinus horn and sinus venosus
- Entry of blood into heart
- Drainage side of cardinal veins
- Sinus venosus develops from sinus horn
- Finally blood comes from right sinus horn
- Sinus horn gets incorporated in atrial wall
- Right common anterior cardial vein becomes superior vena cava
- Right vitelline duct becomes terminal part of inferior vena cava
Liver development
Liver buds grow out, get oxygen via hepatic sinusoids (veins)
Proximal part disappears
Left umbilical vein brings blood to liver
Increase of placental circulation: blood shunt, directly from placenta to hepatocardiac channel: ductus venosus (disappear at birth)
Network around duodenum develops in single vessel: portal vein
Right horn develops into hepatocardiac channel
Vitelline veins form a plexus around duodenum and gut tube, pass through septum transversum
4 chamber formation
New tissue growth
Atria from ventricles
Opening on left and right side to ventricles
Division between left and right atrium
Ventricular septa (aorta vs pulmonary artery)
4 chambers (top to bottom): Truncus arteriosus, Bulbus cordis, Ventricle, Atrium, Sinus venosus
Cardiac looping
Both bulbus and ventricle grow faster than other parts which appears S-shape bend
Primitive heart bends atrium and sinus lie dorsal to bulbus and ventricle
Atrial portion being paired becomes one
Atrioventricular junction remains narrow (from atrioventricular canal: connecting atrium with the ventricle)
Smooth inner surface heart forms primitive trabecullae in ventricle, septa start to form
- Atrium and bulbus remain smooth temporarily
- Sinus maintains its paired condition longer than any other portion of the heart tube
Septa formation
- 4-6 weeks
- Tissue growth
- Two growing masses of tissue approach each other in the same plane, fuse, divide a single chamber into two
- Overgrowth
- Involves a growth of a chamber at all points except a narrow strip that doesnt grow
- Leave small canal connect two chambers
- Atrioventricular septum
- Bulges form on dorsal and ventral walls AV canal: endocardial cushion septum
- Start to divide the ventricles
- Atrial sept
- Septum primum
- Sickle-shaped crest grows from roof of endocardial cushion
- Ostium primum/foramen primum
- Opening between septum and endocardial cushion, closes by growth of endocardial cushion
- Foramen secundum
- Opening in septum primum
- Septum secundum
- As right atrium grows and incorporates part of the sinus
- Foramen ovale
- Valve passes blood from right to left atrium vis ostium secundum (blood from inferior vena cava)
- Bypasses lungs in fetus
- Associated with septum secundum
- At birth, septum primum presses against, seals opening
- Septum primum
- Ventricular septum
- Expansive growth of ventricle laterally, fusion of medial walls starts formation of muscular interventricular septum near apex
- Septal formation in truncus
- Cuntinuous paired ridges fuse, form spiral septum
- Cavum aorticum → LV
- Cavum pulmonare → RV
- Two cava eventually separate forming ascending aorta and pulmonary trunk
- Cuntinuous paired ridges fuse, form spiral septum
Pre and postnatal circulation
Ductus arteriosus closes due to muscle contractions (breathing)
Raises pressure in left atrium
Stop of placental blood flow decreases pressure in right atrium
Closure of foramen ovale
Umbilical cord is cut: closure of umbilical vein and ductus venosus
Arterial septum defect
Opening below foramen ovale: incomplete atrioventricular septum defect
Opening at foramen ovale
