Embryology Flashcards
What week doe the primordial heart start forming?
4th week
Describe the stages of vasculogenesis
- Angioblasts are formed from mesenchymal cells (stem cells)
- Angioblasts go on to form the lining of the endothelium of the vessels
- Blood islands form which form the lumen of the vessels
- These blood islands join together to form bigger islands so larger lumen can be formed
In what sites do the first blood vessels appear?
- yolk sac
- gallantois
- connecting stalk
- chorion (membrane under which the embryo is buried
What are the five chambers of the heart tube?
- trunchus arteriosus
- bulbus cordis
- primitive ventricle
- primitve atrium
- sinous venosus
What are the angioblastic cords?
the two tubes which join together to form the heart tube
cord like masses of splanchnic mesenchymal cells ventral to the primordial pericardial celom (a cavity in the mesoderm of an embryo that gives rise in humans to the pericardial cavity) that arrange themselves side-by-side to form the primordia of the endocardial heart tubes.
What chambers are responsible for the formation of the cardiac loop?
bulbus cordis
primitive ventricle
these both form the bulboventricular loop
What is dextrocardia ?
When the heart tube folds the wrong way so the heart is rotated the opposite way round.
What are the two types of heart muscle in the atria and ventricles and where are each found?
- trabeculae carnae: found in ventricles
- pectinate muscles: found in atria and atrial appendages (can remember pect muscles being up high in the chest so therefore at the top of the heart)
Form what type of mesoderm is the visceral pericardium derived?
splanchnopleuric mesoderm (splanchnic = at the organ)
so the visceral pericardium lies on top of the organ so is splanchnic
Form what type of mesoderm is the serous and fibrous pericardium derived?
somatopleuric mesoderm.
Between what days of development do the heart chambers form?
around 27th and 37th days
During the formation of heart chambers what two things have to form for this to happen?
septal formation
endocardial cushion formation
What occurs during the division of the atria?
- what four septa form?
- why is this done?
Septal Primum forms first which grows from the top of the atria down towards the endocardial cushion in the atrioventricular canal, which creates the foramen primum (ostium foremen) as cells grow up form the endocardial cushion towards the bottom of the septum primum.
Apoptosis (programmed cell death) results in cell death towards the top of the septum primum.
At the same time cells divide and grow up from the endocardial cushion and close over the foramen primum
The septal secondum forms in the left atrium beside the septal primum. As it grows it begins to overlap the foramen primum - this is done to form a valve for the oval foramen to prevent blood from flowing form the right to left atria.
This allows oxygenated blood from the placenta to flow from the left atria to the right atria (by passing the lungs) to be pumped around the embyro.
State the four main types of atrial septal defects.
A) Ostium secundum defect
B) Endocardial cushion defect with ostium primum defect
C) Sinus venosus defect
D) Common atrium
Are males or females more affected by ASD (atrial septal defects)?
females
Are males or females more affected by heart defects?
males
What maternal infection acquired during pregnancy can be associated with congenital heart defects?
rubella
What are some causes of heart defects?
- maternal alcohol abuse
- drug abuse
- radiation
- genetic (8%)
- chromosomes (2%)
Describe the 4 stages of the partitioning of the primitive ventricles.
- Muscular part develops from the proliferation of medial wall
- During the process the IV foramen (interventricular foramen) is formed between the free edge of muscular septum and the fused endocardial cushion
- IV foramen permits communication between left and right ventricles
- IV foramen is closed by the fusion of the right and left bulbar ridges with the endocardial cushion forming membranous part of IV septum.
What is the most common form of VSD and who is most affected?
congenital heart disease
males