Cardiac Embryology Flashcards
When are cardiac contractions first seen in the dog
18-19 days into gestation
What are the contractions like during development
Slow at first but increase in speed when the atria and SV form
When does cardiac portioning begin to occur
28 days
What layer of the embryo does the heart form from
Carcinogenic plate of the mesoderm tissue
What is formed from the arterial trunk
Aorta
Pulmonary artery
What will form the ventricles
Bulbous cordis
Ventricle
What are the five zones of the primitive tube
Arterial trunk
Bulbous cordis
Ventricle
Atrium
Sinus venosus
Why does the heart tube fold
The tube goes quicker than the rest of the embryo but it’s fixed at both ends
So it folds
Which way does the the primitive tube normally fall
To the right
D looping
What is L looping
When primitive tube folds and abnormally falls to the left
What is L looping
When primitive tube abnormally falls to the left
What happens to the sinus venosus
Right horn becomes incorporated into atrial wall
Left horn not incorporated and becomes part of the coronary sinus
How are the AV valves formed
Within the AV canal, left and right AV endocardial cushions are formed
They then form chordae tendinae
What happens if AV valves aren’t developed properly caused by
Endocardial defect and what animal is most commonly affected?
Mitral/ trisxupid dysplasia
Cats and labradors
What stage occurs after AV valve develops
Atrial separation
How are atria separated
Left and right atria separated by septum primum
Grows towards AV cushion
Then a second septum develops called septum secundum
What is the whole between the two atria called in fetus
Foramen primum
Lungs aren’t functioning
How does most blood enter the atria in the the fetus
Caudal vena cava
How does blood then flow round body once it’s reached the atria
Blood aimed at septum primum which is pushing the blood to the left to keep the foramen ovale open
Then blood goes from left atria to ventricle to body
What causes the septum eecundum and septum primum to close
Decreased pressure in RA and increased pressure in LA, as blood inflow from
Lungs
Occurs within minutes of birth
What happens to truncus arteriosus and bulbous cordis
Cushions of each grow towards each other in a spiral
Attached itself to the intraventeivukar septum
How are the ventricles form
Bulbous cordis and ventricle expand due to hyper trophy (expand like two oranges next to each other)
Then necrosis of cells in the middle (of the orange)
When is the heart fully formed (inter ventricular separation)
Day 32 of gestation
What forms the aorta and pulmonary valves
Formation and fusion of truncal ridges get three swellings
What is aortic/ pulmonic stenosis
Not formed S.L. valves
What is a shunt
A passage between natural channels such as blood vessels
What is the point of shunts
To ensure blood doesn’t go to lumgs
What are the three key shunts
Ducati’s venosus
Foramen ovale
Duct is arteriosus
What is the pathway for foetal circulation
Oxygen and nutrients into blood of fetus from umbilical vein towards baby’s liver
Shunt- ductus venosus
Some blood to liver, most to caudal vena cava then RA
Then LA via Foramen ovale
Then LV, aorta and body
Then waste blood intk RA, RV and PA
Flows through duct is arteriosus into descending aorta to umbilical arteries, into mothers circulatory system
What are the earlier stages of cardiac development
Atria
SA calages
AV valves
What are the later developments
Two Ventricles
Truncus arteriosus into aorta and PA
Vena cava
Why is fetal circulation different from adult
It ‘breathes’ amniotic fluid, so pulmonary artery doesn’t carry oxygen
Fetal blood is oxygen poor
Hepatic portal vein isn’t needed as fetus is fed parentally (via umbilical cord) not orally
Has a stable temperature from amniotic fluid
What does the placenta use the placenta for
Fuel storage/ detoxification
Gas exchange
Waste removal
What are fetal lungs like
Collapsed and unnecessary
Have high resistance
What is the fetal liver like
Not required to excrete waste
Becomes important over last gestation as it’s stores glycogen for use post birth
Why is the blood pressure needed to be kept low
Developing organs and tissues are fragile
So most blood kept away and low
What pressure is blood at in fetus
40-50
What do the shunts in the fetus push blood towards
Adrenal
Heart
Brian
Placenta
What do the shunts push blood away from
Liver
Gut
Kidney
Carcass
Lungs
Why are shunts important
Sends blood to essential organs for immediate survival during physiological stress (birth)
Why does the fetus circulation differ
It’s a symbiotic parasite
How does fetal circulation work
Form the placenta via the umbilical vein to the liver via the ductus venous
Then via caudal vena cava to RA and then LA via Foramen ovale
Then to aortic arch, carotid artery then to cranial VC to RA,
Then via ductus arteriosus to descending aorta
Then back to placenta via umbilical arteries
What are the main blood vessels in fetal circulation
Umbilical vein
Ductus venosus
Foramen ovale
Ductus arteriosus
Umbilical arteries
What are the structures within the umbilicus and their function
Umbilical vein- delivers nutrients to fetus
Umbilical arteries- delivers blood back to placenta
Urachus- a remnant of the alantois (thing before UC was formed- drained urinary bladder)
Which species doesn’t have a ductus venous
Feral horse
What is the function and pathway of the ductus venous
Causes 50% of blood to bypass the liver as no oral intake of food
Shunts blood from umbilical vein to caudal VC
Streams blood to the forameb ovale
What keeps the forameb ovale open in the fétus
Pressure difference
High blood flow
What is the function of the ductus arteriosus
Shunts blood in pulmonary artery to descending aorta
What must fétus do after birth
Start respiration
Circulate a closed system
Begin digestion
Thermoregialrion
Excretion of waste
How does the ductus venous shut
Umbilical cord is located as placenta detaches, so no blood in UV vein
Therefore DV sphincter constructs and blood goes to liver
What is the remnant of the DV called
Ligamentum venosum
How does the foramen ovale shut
Lungs open, so low pulmonary resistance
Placenta is gone so high systemic resistance
Pressure difference causes septa to close and fuse together
What is the remnant of the forameb ovale called
Fossa ovalis
How does the ductus arteriosus close?
DA constricts as increase pO2
Pressure lower in lung, pressure higher in body as blood flows through
What is the remnant of the ductus atteriosus called
ligament arteriosus
What mechanisms occur after birth
Increased PO2 due to lung inflation
Vascular resistance in body increases due to loss of placenta
Changes in hormones (cortisol, catecholamines)
Tissue layers pushed together to become ligaments
When does the DV shunt close
Functional closure within minutes due to improved pulmonary clearance and no UV blood supply
Anatomic closure within days
When does the closure of the FO occur
Functional closure within hours of birth
Anatomic closure is slow (weeks-years)
When does the DA close
Functional- Within minutes to hours
Anatomic- 2-7 days
What do the internal umbilicals become
Round ligaments of the bladder
What does the umbilical vein become
Round ligamnet of liver
What physiological changes occur at the transition from foetus to neonate
Increased oxygenation
Haemoglobin changes
BP increased
Enteral intake of nutrients
What are the four features of tetralogy of fallout
Narrowing or valve between hearth and lungs
Ventricular septal defect
Right ventricular hypertrophic
Aorta is shifted to the right
What is eisenmengrrs syndrome
Due to high pressure in lungs
Too much pulmonary hyper tensions and vasicuakr resistance so blood is reversed and goes from left to right side of heart
