Development of the heart Flashcards
Where does the circulatory system arise from?
Mesoderm
What is the first system to function?
The circulatory system
When does blood begin to circulate?
By the end of the 3rd week
When and where is heart development first indicated?
At 18 - 19 days in the cardiogenic area near the embryonic head
What is the cardiogenic area derived from and when?
Splanchnic mesoderm cells - intra-embryonic mesoderm, 3rd week
What is at either side of the neural plate?
Horse shoe area
What occurs as folding takes place?
The heart tubes fuse to form a single medial endocardial heart tube.
What does thickening mesenchyme around the heart tube thicken to form?
A myoepicardial mantle
What does the myoepicardial mantle become?
Epicardium and myocardium
What is the heart tube composed of? x3
1) Myoepicardial layer
2) Cardial jelly
3) Endocardium
What is cardial jelly secreted by?
Cardiac myoblasts
What does cardial jelly permit?
Permits twisting and diminishes until myocardium is adjacent to endocardium.
What are the five heart regions?
- Truncus arteriosus
- Bulbus cordis
- Primitive ventricle
- Primitive atrium
- Sinus venosus
What is the truncus arteriosus continuous with? x 2
- Caudally with the bulbus cordis
- Cranially with the aortic sac and the aortic arches
What is the sinus venous and what does it receive?
A large venous sinus which receives the umbilical vein the vitelline vein and common cardinal veins.
What are the fastest growing regions?
The bulbus cordis and ventricle
What will the truncus arteriosus become?
Divide into ascending aorta and pulmonary trunk.
What will the bulbus cordis develop into?
Right ventricle
What does the primitive ventricle form?
Left ventricle
What does the primitive atrium become?
The anterior portions of both the right and left atria, and the two auricles.
What does the sinus venosus develop into?
The posterior portion of the right atrium, the SA node, and the coronary sinus.
When do contractions begin?
At day 22
Where do peristalsis-like waves begin?
In sinus venosus
What is blood from sinus venosus controlled by?
SA valves
What happens when ventricle contracts? (where does blood enter)
Enters bulbus cordis, into the aortic sac and then into the aortic arches (branchial arches) to the dorsal aorta
When does septation occur?
From days 28-37
What openings in septum primum and scundum allow?
Allow right-to-left shunting of blood throughout gestation
What is the ostium secundum?
An invagination that arises from the roof of the atrium to the right of the septum primum making its way to the AV cushion
What does foramen ovale allow?
Blood flow from right to left atrium
Why does the foramen ovale close at birth?
Abrupt dilation of the pulmonary vasculature combined with cessation of umbilical flow reverses the pressure difference between the atria and pushes the flexible septum primum against the more rigid septum secundum
When does the interventricular septum takes place?
Between the 4th and 7th week
Summary - day 18/19 -
From the mesoderm – first organ to appear from cardiogenic region near the head.
Summary - day 20/21
Cardiogenic cords transform to endocardial tubes which transform into a single heart tube
Summary - day 21/22
Primitive heart begins beating and pumping blood.
Summary - day 22
Heart tube transforms into the truncus arteriosus, bulbus cordis, primitive ventricle, primitive atrium, and sinus venosus, starting about day 22.
Summary - day 22-28
Developing heart is an S shape within the pericardium
Summary - day 28
Internal septa begin to form
Summary - weeks 5 and 8
The atrioventricular valves form.
Summary - weeks five and nine
Semilunar valves form
