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1.23.5.10 - Cardiac Embryology - Coggle Diagram
1.23.5.10 - Cardiac Embryology
dogs
cardiac contractions
slow at first
increase when atria and SV form
start at 18-19 days
cardiac partitioning occurs at 28 days
embryonic disc
mesoderm
ectoderm
endoderm
phases of cardiac embryonic development
cardiogenic plate of mesodermal tissue at head end of embryonic disc
there is rapid development and flexion of head which causes disc to lie below head and mouth but cranial to the foregut
heat is the first organ to undergo functional differentiation
zones of the primitive tubes
ventricle
atrium
bulbus cordis
sinus venosus
arterial trunk
growth of the primitive tube
folds
whe nit folds it falls to the right in D-looping
primitive tube grows quicker than the rest of the embryo and is fixed at two ends
in some cases embryo can have abnormality where tube falls to the left (L-Looping)
venous sinus
right horns becomes incorporated into the atrial wall
left horn becomes the coronary
A-V cushions
they are made up of left and right endocaridal tissue
they go on to form chordae tendinae and atrioventricular valves
a-v cushions are present in the atrioventricular canal
development of the aortic arches
1,2,5 disappear
3 - contributes to the common carotid artery and the proximal internal carotid artery each side
mammals go through stages when all 6 arches appear
4 - right arch forms the right subclavian artery, left arch forms the aorta
6 arches
6
proximal right arch persists as the proximal right artery while the distal section degenerates
left forms the left pulmonary artery and forms the ductus arteriosus
fish
single circulation: gills - body - heart
simple heart
special considerations of the avian cardiovascular system
they have a relatively large cardiac size compared to body weight
can in some species generate very fast heart rates - up to 1000 bpm
birds have a highly efficient cardiovascular systems
important for oxygen delivery and thermoregulation
to cope with high metabolic demands
major fetal vesles
foramen ovale
ductus arteriosus
ductus venosus
systemic arches of tetrapods
fewer and fewer aortic arches remai and they become less symmetrical in the final developed circulatory systems of anurans, reptiles and then mammals
shunts
a passage or anastomosis between two natural channels such as blood vessles
primitive stages of cardiac development
development of the atrioventricular valves
development of the semi-lunar valves
SA valves
later developments
two ventricles
vena cavae
truncus arteriosus dividing into Ao and PA
development of the atria
ontology
development of the embryo from fertilisation to gestation or hatching
goes through stages representing the stages of the evolution of the animals remote ancestors
fibrous cardiac skeleton
insulation of the AV bundle
ossa cordis
separates atria and ventricles
fetal circulation
Oxygen and nutrients from the mother's blood are transferred across the placenta and flows through the umbilical vein towards the baby's liver
Most of this oxygenated blood flows to caudal vena cava and then into RA
This allows some of the blood to go the liver
Most of the blood flows across to the LA through foramen ovale
There it moves through a shunt called the ductus venosus
Blood returning to the heart from the body contains carbon dioxide and waste products as it enters the RA
From the left atrium, blood moves to LV and then aorta to the body
Then flows through the ductus arteriosus into the descending aorta, which connects to umbilical arteries into the placenta
It flows down into the RV and into the PA
There the CO2 and waste products are released into the mother's circulatory system
fish, amphibians and reptiles
The stages the mammalian heart goes through during embryological development are evident in the CV systems of fish, amphibians and reptiles
theory of recapitulation
embryological parallelism
ontogeny recapitulates phylogeny
formation of the aortic and pulmonic valves
expand into the lumen of each vessel
very broad then thin with cellular degeneration
following formation/fusion of truncal ridges get three swellings in walls of Ao and PA trunks
common problems: aortic/pulmonic stenosis
interatrial septa/septum primum
The septum primum grows down towards the AV cushions
O1 (opening 1) - the Foramen primum - allows for blood flow from right to left
The left and right atria are separated by the septum primum
septum secundum
The septum secundum is a second septum that develops to maintain R to L blood flow
It forms a second foramen - which occurs before the closure of the foramen primum - has a series of fenestrations
foramen ovale
The Pressure difference across FO keeps it in open in the fetus (although the pressure gradient is not large)
Patency is maintained by the high blood flow
The Foramen Ovale (FO) shunts blood straight through the Right atrium to the left atrium
blood flow in the atria in early cardiac development
Aimed at septum primum - pushing to left, keeping FO open - flows from right atrium to left atrium
Blood then goes from Left Atrium → left ventricle → body
Lots of blood enters atria from caudal vena cava at this stage
Small amount from right atrium to right ventricle to PA to Ductus
interatrial septa at birth
Septum secundum and septum primum now called inter-atrial septum
Apposition but not fusion common especially in cattle
This occurs within minutes of birth
PFO (persistant foramen ovale) common in people and cattle
Septum secundum and septum primum appose
growth of the truncus arteriosus and bulbus cordis in primitive tube development
Bulbar cushions develop in bulbis cordis and truncal cushions develop in truncus arteriosus which then form forms aorticopulmonary septum as they move up truncus ateriosus
They grow towards each other in spiral
True separation occurs
They then go on to contribute to the interventricular septum
development of the interventricular septum
nterventricular septum from caudal expansion and hypertrophy of the bulbus cordis and primitive ventricle rather than 'growth' of a septum
Bulbus cordis and ventricle grow in caudoventral direction - called Trabeculation
Once the atrioventricular and truncobulbar cushions form and fuse - last step is formation of two ventricles from a common chamber
formation of the atrioventricular valves
Ventricles dilates, walls hypertrophy, trabeculation occurs and endodermal cell death
Strands of cardiac wall mesenchyme from atrio-ventricular cushions to ventricular valves and chordae tendinae
Form from reshaping and tissue loss within ventricular walls
point of trabeculation
Gives rise to uneven surface of ventricles
Endocardial cells undergoing apoptosis
Retention of muscular papillary muscles (support AV valves)
Mesenchymal and myocardial cells dividing