Lecture 21: Thorax IV, Heart Development Flashcards
what is the lub sound
closure of AV valves
what is the dub sound
closure of semilunar valves
what heart valves are auscultated on left side (3)
-aortic
-pulmonary
-mitral/left atrioventricular
what heart valve is auscultated on right side
tricuspid/right atrioventricular
where does heart tube/cardiogenic region develop from
visceral lateral plate mesoderm
craniocaudal folding: moving head into thorax
-ectoderm and endoderm fold at ends (cranial and caudal ends fold towards each other)
-mesoderm is pulled caudally, now in neck area
-embryo continues folding until cardiogenic region in chest cavity
-heart tubes get pulled into pericardial cavity, they fuse
-
how does heart primordium move ventrally (body folding)
pericardial cavity, heart tube and septum transversum move caudally until pericardial cavity is ventral to heart tube
-all these will be ventral to developing foregut
what is the septum transversum
precursor to part of diaphragm (caudal to heart)
where does the diaphragm migrate
from cervical to thoracic position because of differential growth of embryo
formation of phrenic nerve
from axons of ventral rami from cervical spinal cord levels C5-7
C7, C6, C5 keep the diaphragm alive
because the phrenic nerve arises in the neck from C5, C6 and C7
steps of embryological development (general)
-lateral folding to form heart tube
-cardiac looping
-restructure venous system
-septation
-closing of shunts
lateral body folding to move/form endocardial heart tubes
-lateral folding brings 2 endocardial tubes together
-myoblasts give rise to myocardium
-endocardial tubes fuse into 1
-heart tube surrounded by myocardium
-myocardium secretes cardiac jelly
what does cardiac jelly turn into
endocardial connective tissue
what are the primary outflow of oxygen poor blood from the fetus
dorsal aortae
early vessel development and blood flow
-blood received at caudal pole of heart tube at sinus venosus
-blood delivered from cranial end of heart tube and passes through aortic arches and sac
function of sinus venosus
receive blood
location of sinus venosus
cranial to heart tube (right next to it)
structures of heart tube from cranial to caudal (9)
-outflow tracts = dorsal aortae/aortic roots
-aortic sac
-truncus arteriosis
-bulbus cordis
-bulboventricular sulcus
-primitive ventricle
-atrioventricular sulcus
-primitive atria
-sinus venosus
primitive ventricle will become
left ventricle
truncus arteriosis and conis cordis will become (2)
pulmonary arteries/trunk and aortic arch
bulbus cordis will become (3)
right ventricle
right and left outflow tracts (left outflow from left ventricle, right outflow from right ventricle)
primitive atria will become (2)
right and left atria
sinus venosis will become (3)
common cardinal veins
umbilical veins
vitelline veins
when does cardiac looping occur
after formation of heart tube
where does cardiac looping occur
inside pericardial cavity
cardiac looping: steps
-bulbus cordis shifts cranially, ventrally and to the right
-primitive ventricle shifts to the right (towards midline)
-primitive atria move caudally, dorsally, to the left (backwards and then upwards, pushed back behind)
-formation of interventricular sulcus with ventricle separation starting
-conus cordis forms distal outflow tracts for right and left ventricles
result of cardiac looping
-displace neighboring structures
restructuring of venous system
-veins on left horn of sinus venosis break down
-left horn becomes coronary sinus
-right horn gets bigger and becomes smooth part of right atrium
right common cardinal vein will become
cranial vena cava
right vitelline vein will become
caudal vena cava
function of inflow tracts
take blood and empty into right atrium
what 3 veins are located on the left and right horns of the sinus venosus (lateral to medial)
common cardinal vein
umbilical vein
vitelline vein
what happens to the umbilical vein
distintegrates
primitive blood flow
common atrium –> AV canal –> primitive left ventricle –> interventricular foramen –> right ventricle –> out through bulbus cordis (conis cordis and truncus arteriosis)
where do pulmonary veins sprout off of
left part of primitive atrium
primordial part of left atrium is what
left auricle
4 septation processes
-atrioventricular
-atrial septation
-ventricular septation
-articopulmonary septation
1st septation to occur
atrioventricular
atrioventricular septation: process
-endocardial cushions develop between atrium and ventricle
-cushions grow towards each other from each side
-fusion divides AV canal into right and left parts
what is the structure formed when endocardial cushions fuse (hint: wall)
septum intermedium
product of atrioventricular septation
separate left and right sides of heart
-create right AV canal and left AV canal
function of septum intermedium
separate primitive atria and primitive ventricle
what do ventricles/heart do during cushion fusion
heart realigns so both ventricles line up with truncus arteriosis
purpose of atrial septation
separate right and left atria
atrial septation: process
-septum primum grows between primitive atria roof
-grows down toward endocardial cushions but is stopped before reaching which creates a space = foramen primum
-foramen primum forms a shunt to bypass the right ventricle
-perforations appear in septum primum to form forman secundum as foramen primum closes due to growth of septum primum
-septum secundum begins to grow to close foramen secundum
foramen ovale: definition and importance
space remaining between septum secundum and formen secundum
-where blood bypasses right atrium into left atrium (no lungs)
ventricular septation: function
separate bulbus cordis (part of the right ventricle) and primitive ventricle (left ventricle)
ventricular septation: process
-muscular interventricular septum arises from floor of primitive ventricle
-doesn’t fuse with endocardial cushions
-incomplete fusion leaves gap = interventricular foramen
aorticopulmonary septation: result
divide pulmonary trunk from aorta
aorticopulmonary septation: process
-AP septum spirals so aorta and pulmonary trunk twist around each other
-pulmonary outflow = right ventricle
aortic outflow = left ventricle
3 shunts that bypass liver and lungs during fetal circulation
-foramen ovale
-ductus arteriosis
-ductus venosus
formane ovale: shunt
from right atrium to left atrium to bypass right ventricle
adult remnant of foramen ovale
fossa ovalis
ductus arteriosis
shunt from pulmonary trunk to aorta to bypass lungs
adult remnant of ductus arteriosis
ligamentum arteriosum
how does foramen ovale close
pressure changes as a result of ductus arteriosus closing
pushes septum primum against septum secundum to close off foramen ovale
