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49 Cards in this Set

  • Front
  • Back
when does the cardiovascular system begin to develop?
week 3

mesenchymal cells derived from mesoderm form endothelial tubes which join to form primitive vascular system
from what does the heart develop?
splanchnic mesenchyme in cardiogenic area
what forms the paired endocardial heart tubes?
bilateral cardiogenic cords formed from mesenchyme, which become canalized and then fuse into a single heart tube
what happens to the mesenchyme surrounding the cardiogenic cords?
surrounding mesenchyme thickens to form myoepicardial mantle separated from endothelial heart tube by gelatinous cardiac jelly
what are the four parts of the primitive heart?
sinus venosus
bulbus cordis
what veins drain into the sinus venosus in the primitive heart?
vitelline veins from the yolk sac
umbilical veins from the chorion
common cardinal veins from the embryo
with what is the truncus arteriosus continuous caudally? cranially?
caudally - bulbus cordis

cranially - enlarges to form aortic sac (from which aortic arches arise)
what do the systems of paired veins become after birth?
vitelline system - portal system
cardinal system - caval system
umbilical system - degenerates
why does the bulboventricular loop form?
bulbus cordis and ventricle grow faster than the rest of the heart and it bends on itself to form the bulboventricular loop
what happens at the same time that the bulboventricular loop forms?
heart invaginates into pericardial cavity
what forms the transverse pericardial sinus?
dorsal mesocardium (which attaches heart to dorsal wall of pericardial cavity) degenerates to form the transverse pericardial sinus
when does the first heartbeat occur?
21 to 22 days
where do the peristalsis-like waves of the primordial heart begin?
sinus venosus
when does the heart have coordinated contractions which result in unidirectional flow?
by the end of week 4
what is the pathway through the primitive heart?
blood enters the sinus venosus from vitelline, cardinal, and umbilical veins

blood flows into primitive ventricle

ventricular contraction pushes blood into the bulbus cordis and truncus arteriosus into the aortic sac, passing the aortic arches and branchial arches

blood passes to dorsal aortae for distribution to embryo, yolk sac and placenta
when does the heart divide into four chambers?
between weeks 4 and 7
what divides the atrioventricular canal?
endocardial cushions from the dorsal and ventral walls and begin approaching each other at week 5, fusing, and dividing the atrioventricular canal into right and left canals
when does the septum primum begin to extend into the atrium? from where?
day 28

superoposterior wall, growing caudally toward atrioventricular canal
when are the left and right atria separated by the septum primum?
fifth week
what is the ostium primum?
foramen that forms in the septum primum
when does the septum primum fuse with the endocardial cushions to obliterate the ostium primum?
at the end of the sixth week
what is the ostium secundum?
shunt formed by the coalescence of perforations in the septum primum, which form before the ostium primum closes
what is the septum secundum?
a flap growing from the roof of the right atrium, but not reaching the endocardial cushion, leaving an opening called the foramen ovale
what are the two staggered openings through which blood shunting from right atrium to left atrium passes?
foramen ovale (from septum secundum)

foramen secundum (septum primum)
what closes the foramen ovale after birth?
fusion of the septum primum with the septum secundum
from where is the coronary sinus derived?
left horn of the sinus venosus
from where is the right atrium derived?
smooth part (sinus venarum) - right horn of the sinus venosus

muscular part (auricle) - primitive atrium
what separates the sinus venarum from the auricle internally and externally?
internally - crista terminalis

externally - sulcus terminalis
until when is the crescentic fold which partitions the ventricles open cranially (interventricular foramen)?
until end of week 7
when does the aorticopulmonary septum divide the truncus arteriosus into the pulmonary trunk and aorta?
during week 5

valves develop from proliferation of subendocardial tissue
from what temporary pacemaker does the sinus venosus take over?
primitive atrium
when does the sinoatrial node develop? from where?
week 5
(part of the sinus venosus which becomes incorporated into the right atrium)
from where does the atrioventricular node develop?
sinus venosus
when is the critical period of heart development?
20-50 days after fertilization
what is the most common defect of the cardiac septa?
ventricular septal defects
what is a membranous ventricular septal defect?
oval membranous portion of interventricular septum fails to develop
what is a muscular septal defect?
perforation anywhere in the muscular part of the interventricular septum

caused by excessive resorption of myocardial tissue during formation of muscular part of interventricular septum
what is cor triloculare biatriatum?
3-chambered heart resulting from absence of interventricular septum
what does tetralogy of fallot consist of?
pulmonary valve stenosis
ventricular septal defect
overriding aorta
hypertrophy of right ventricle

(cyanosis is obvious sign but may not be present at birth)
what is pulmonary valve stenosis?
cusps of pulmonary valve are fused together to form a dome with a narrow central opening
when do aortic arches, arising from the aortic sac, penetrate the branchial arches?
week 4 and 5

(when the branchial arches form)
when is the primitive aortic arch pattern transformed into the adult arterial arrangement?
during week 6 to 8
when does the lymphatic system begin to develop?
week 5
how does the lymphatic system develop?
6 primary lymph sacs develop, and later become interconnected by lymph vessels

lymph nodules don't appear until just before and/or after birth
what is a hygroma?
tumor-like mass of dilated lymphatic vessels derived from pinched-off portion of jugular lymph sac
via what vein does oxygenated blood return to the fetus from the placenta?
umbilical vein

drains into liver or passes by via ductus venosus
what forms a shunt for oxygenated blood to bypass the liver?
ductus venosus
what structures of the fetal heart close after birth?
foramen ovale
ductus arteriosus
ductus venosus
umbilical vessels
how long does it take for left ventricular wall to be thicker than right?
1 month after birth

(at birth right ventricular wall is thicker)