Anatomy of Bloodflow Through Fetal Heart Flashcards
what are the black arrows
valve flaps of the atrio-ventricular or tricuspid valve
what are the red and pink arrows
red: chordea tendineae of tricuspid valve
pink: papillary muscles
what is the structure of the right AV (tricuspid) valve
3 cusps: chordae tendineae and papillary muscles/fibrous annular ring support
what is the action of the AV valve
passive/prevents backflow of blood into atrium at systole
1st heart sound lub = closure of right and left AV valves
what are the structures of the right ventricle
list 5 anatomical features of the right ventricle
- wall: endocardium, myocardium and epicardium
- trabecular septomarginalis: distinct feature of right atrium –> carries the short circuiting impulse to the walls –> related to the papillary muscles which will contract before the walls of the heart contract to prepare to hold the valves
- trabecular carneae: elevation of wall –> act like pectinate muscle –> dampen out the turbulence of blood
- pulmonary trunk exits RV on the left lateral side of the heart
- walls are smooth and shiny
what are the structures (transverse section through R&L ventricles)
- most cranial point
- right ventricle
- interventricular septum
- left ventricle
identify the labels and describe how blood flows through the right side
right ventricle forms the cranial margin of heart
blood exits RV through pulmonary trunk (on left lateral side) through pulmonary semi-lunar valve
pulmonary trunk bifurcates into L&R pulmonary arteries which enter root of L&R lung
list the anatomical features of the pulmonary semilunar valve
- at junction of RV and pulmonary trunk
- second heart sound ‘dub’ = closure of pulmonary and aortic semi lunar valves
what is the ligamentum arteriosum
ligament linking the pulmonary trunk and aorta
fetal remnant of the ductus arteriosus
what are these structures
describe the blood flow through the left side of the heart
- oxygenated blood enters left atrium (& auricle) from the lungs via pulmonary veins –> mitral valve (bicuspid) or left AV valve –> left ventricle –> aortic semi-lunar valve guards entrance to aorta –> aorta exits middle of base of heart
what ventricle forms the base of the heart
left –> very thick wall
what are the anatomical features of the mitral valve
2 cusps
what are the structures of left atrium and ventricle
what are the structures (dorsal view of heart after removal of atria)
- right atrioventricular valve
- left atrioventricular valve
- aortic valve
- pulmonary valve
- left coronary artery
- righ coronary artery
cr: cranial
what are the structures
A: mitral valve
B: semi-lunar valve
C: coronary circulation
what is the puncta maxima
points on the chest wall where heart sounds are heard best
left thorax: between 3,4,5th intercostal space
right thorax: tricuspid 4th intercostal space
what are the structures of the thorax
- cranial extent of heart
- caudal extend of heart
- basal border of lung
- line of pleural reflection
- caudal border of lung percussion area shown on right side
what are the structures shown here
- right auricle
- left atrium
- left atrioventricular valve
- interventricular septum
- aorta
what are the structures of the early fetal heart
placenta –> maternal and fetal blood flow coming close to each other
the umbilical vein has nutritious and highly oxygenated blood
returns deoxygenated blood to the placenta
what is the 1st step in the formation of the 4 chambered heart
subdivision of the channel between the primitive atrium and ventricle
2 chambered heart recieving and distributing areas that is segmented in the middle –> partitions coming from above and below
what is the second step in the formation of the 4 chambered heart
subdivision of the primitive ventricle continues –> interventricular septum
the atrioventricular channel splits into two-av canal cushions
the interatrial septum starts to form but is never complete
what is the third step in the formation of the 4 chambered heart
ventricles are now separate
AV valves form
the atria continue to intercommunicate (RA to LA) via foramen ovale
what is the distribution of blood in the fetus before birth
lungs not functional –> high resistance pulmonary circulation
blood flows mainly to the low resistance systemic circulation and the placenta
2 shunts make this possible –> foramen ovale, ductus arteriosus
what other shunt maximizes the PO2 of blood entering the heart from the placenta
ductus venosus in the liver
what is the function of the ductus venosus
blood moves from the umbilicus towards the liver via umbilical vein (green) –> shunt in liver (ductus venosus) prevents mixing of oxygenated blood from placenta (red) with fetal hepatic venous return from gut (blue) –> blood enters right atrium via caudal vena cava (orange)
what is the function of the foramen ovale
oxygenated blood entering right atrium (RA) passes through one way valve –> foramen ovale –> diverted into LA-LV-aorta (orange) –> into aorta –> preferential delivery of blood with high PO2 leaving left ventricle to heart and brain –> blood entering RA from cranial vena cava flows into RV (as in adult) (dark blue)
**a passageway between right and left atrium
don’t want the blood to go into the right ventricle –> goes through the hole and into the left side where it will go through the aorta to head
the caudal vena cava –> carries highly oxygenated blood
cranial vena cava brings deoxygenated blood into the right atrium –> there is a mixing of blood in the right atrium
the cranial vena cava deoxygenated blood is forced into the right ventricle –> bypassing the mixing –> goes to the pulmonary trunk
what is the function of the ductus arteriosus
2nd shunt links pulmonary trunk to aorta –> allows blood entering right ventricle to bypass the lungs and pass into the aorta and eventually bakc to the placenta –> exercises right ventricle in prep for delivering entire output to lungs after birth
**mixes with deoxygenated blood here from the aorta –> nourishes other areas of the body before returning to the placenta
how does the ductus venosus close and what are defects associated with it
often persists until birth in carnivores, ruminants and humans
defect: persistent patent ductus venosus
portacaval shunt: portal blood bypasses liver
how does the foramen ovale close and what are defects associated with it
lung inflation causes increased pressure in left atrium –> functional closure before anatomical closure –> scar right atrium –> forms scar tissue in interatrial wall (fossa ovalis)
defect: patent foramen ovale not problematic
how does the ductus arteriosus close and what are defects associated with it
inflation lungs causes turbulence –> smooth muscle constriction –> anatomical closure –> forms ligamentum arteriosum
defect: patent ductus arteriosus –> serious characteristic machinery murmur
what are the 3 main categories of congenital heart defects
- failure of closure of fetal structures (foramen ovale, ductus arteriosus –> PDA, ductus venosus –> liver)
- septal defects (interventricular septum)
- great vessel defects –> defects of outflow tracts –> aortic or pulmonary valves
- dysplasia - malformed or disorderly
- stenosis - decreased lumen size
- malposition/fusion of great vessels
