Cardiac embryology Flashcards
What is the heart formed from
Cardiogenic plate of mesodermal tissue at head end of embryonic disc
What does the cardiovascular system start as
Pulsatile tube
Where do paired vein enter the heart tube from during development
The trunk, liver, yolk sac, placenta
Where do the arterial arches develop and emerge
From the upper end of the embryo
What are the 5 zones of the primitive tube
- Arterial trunk/ truncus arteriosus
- Bulbus cordis
- Ventricle
- Atrium
- Sinus venosus
Describe the layers of the heart and what they develop from
- Endocardial tube= endocardium
- Cardiac jelly= myocard contraction, cell migration- septa and valves
- Thick layer of mesoderm= myocardium
- Thin epicardial layer= epicardium
How does the developing heart fall during growth of the primitive tube
Falls to the right in a d-looping fashion
How is blood supplied to the heart at this stage
Blood flows from vitelline to common cardial veins to sinus venous, then to atria, from atria to common ventrical, then out through arterial trunk
During this, how does the heart take shape
Sinous venous shifts across bottom to cover all of it, Bulbus cordis folds in to be inline with ventricle, Atrium splits to be alongside bulbus cordis and ventricle on both sides and slightly above, Arterial trunk stays at the top
Describe the partitioning of blood flow through cardiac chambers
- Atria
- Atrio-ventricular canal
- Bulboventricular loop
- Arterial trunk
- Separation of the aorta and pulmonary artery
What do the two horns of the sinous venosus become
- Right horn - becomes incorporated into the atrial wall
2. Left horn not incorporated - becomes coronary sinus
What do the atrioventricular cushions form?
They develop on the atrioventricular canal forming the valves and septa in this area to make the heart four chambered
What is the interatrial septum?
wall that separates atria
What is the intra-atrial septum?
Second septum that forms to maintain R to L flow. Forms a second foramen, which occurs before the closure of foramen primum.
Describe the blood flow into the atria during development
- blood enters the atria from caudal vena cava at this stage
- Aimed at septum primum - pushing to left keeping Foramen ovale open - right atrium to left atrium
- Blood then goes to left atrium - left ventricle - aorta - body
septum secundum
defines upper and lower boundaries of foramen ovale
septum primum
flap of tissue in the fetus that covers the foramen ovale within a few seconds after birth
Truncus arteriosus
Gives rise to ascending aorta and pulmonary trunk
How does truncus arteriousus grow?
From the truncal septum downwards, rotates clockwise.
Vessels lumen enlarge, truncus expands and two channels completely separate. Aorta arches over pulmonary artery
Describe the formation of the interventricular septum
Growth of the ventricle moves it to central position.
Once atrioventricular and truncobulbar cushions form and fuse - last step is formation of two ventricles from a common chamber
What occurs in the ventricles to elicit trabeculation
- Endocardial cells undergo apoptosis
- Gives rise to uneven surfaces
- there is also retention of muscular
How does the interventricular septum close?
Due to growth of atrioventricular cushions
How do the atrioventricular valves form?
Form from reshaping and tissue loss within ventricular walls.
Ventricle dilates, walls hypertrophy, trabeculation occurs and endothermal cell death
- strands of cardiac wall mesenchyme from atrioventricular cushions to ventricular wall remain
- Form cusps of atrio-ventricular valves and chordae tendinae
Describe the formation of the aorta and pulmonary artery
- Following formation/fusion of truncal ridges get three swellings in walls of aorta and Pulmonary artery trunks
- Expand into the lumen of each vessel
- Very broad and then thin with cellular degeneration
What is a ventricular septal defect?
VSD is an abnormal opening between the right and left ventricles. Many VSDs close spontaneously during the first year of life if small or moderate defects
Which stages of cardiac development are primitive?
- Development of the atria
- SA valves
- Development of atrioventricular valves
- Development of semi-lunar valves
What stages of cardiac developments are more recent evolutionarily
- two ventricles
- Truncus arteriosus dividing to aorta and pulmonary artery
- vena cava
Describe the fish heart
- one atrium
- one ventricle
- rudimentary valve between two
- conus arteriosus to gills
- keep sinus venosus
Describe the amphibian heart
- Single ventricle
- two atria
- sino-atrial valves
- sinus venosus
- Rudimentary semi-lunar valves
Describe a snake’s heart
- three chambered heart (two atria, one ventricle)
- caudal vena cava and two cranial vena cava (drain into sinus venosus)
- hard to tell difference from sinus venosus and right atrium
- has paired AV valves and paired semi-lunar valves
- 2 aortic arches
Describe a lizard’s heart
- position of heart is dependent on breed
- two atria, left and right ventricle
- R and L aortic arches
- one pulmonary vein
Describe a chelonian heart
- single ventricle
- two atria
- two large carotid-subclavian arterial trunks
Describe a bird heart
- relatively larger than mammals and beat faster
- comparitivley larger left ventricle
- main structural difference is artioventricular valve, is a muscular flap
