Embryology 1 Flashcards

1
Q

From what embryonic tissue is the circulatory system derived?

A

The lateral plate splanchnic mesoderm

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2
Q

Where are the first blood vessels found?

A

In the walls of hte tolk sac, allantois, connecting stalk and chorion.

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3
Q

How are the two primitive heart tubes formed?

A

Aniogenic cell islands coalesce in the lateral plate splanchnic mesoderm
Then migrate towards the midline
Then become paired angioblastic cords before becoming heart tubes

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4
Q

The 2 heart tubes form to make one primitive heart tube, what are its sections?

A

From cranial to caudal:
- Truncus Arteriosus
- Bulbus Cordis
- Primitive Ventricle
- Primitive Atrium
- Sinus Venosus

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5
Q

Describe the structure of the sinus venosus/

A

Two horns
Each horn divides to drain blood from 3 areas:
- Yolk sac via vitelline vein
- Placenta via umbilical vein
- Embryo’s body via common cardinal vein

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6
Q

What happens above the truncus arteriosus?

A

The top of the TA forms the aortic sac which divides into two horns each with 6 arches that terminate in a R & L dorsal Aorta

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7
Q

How does the heart tube become the shape of the adult heart?

A

The BC and ventricle grow faster than the rest of it causing it to loop to the right forming a caridac (bulboventricular) loop.

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8
Q

How does dextrocardia occur?

A

The heart tube loops to the left instead of right so it ends up facing the right.

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9
Q

What is the final fate of the bulbus cordis?

A

The Bc forms the right ventricle and parts of the outflow tracts (aorta & pulmonary trunk)

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10
Q

What is the adult form the primitive ventricle?

A

the left ventricle

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11
Q

What does the primitive atrium becomes?

A

Left atrium and parts of right.

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12
Q

What does the sinus vensosus become?

A

The SVC and the right atrium

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13
Q

How is the common atrioventricular canal seperated into left and right?

A

By formation of endocardial cushions

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14
Q

In short how are the atria seperated?

A

By the formation of two adjacent septa each with a foramen that eventually close after birth

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15
Q

What are the two septa and foramen in the atria?

A

Septum Primum - Foramen secundum
Septum Secundum - Foramen Ovale

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16
Q

What are the remains of the foramen ovale left behind in an adult?

A

The fossa ovalis in the interatrial septum

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17
Q

What is the function of the foramen ovale?

A

To allow blood to bypass the lungs passing straight through a valve from right to left atria.

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18
Q

Whats another name for foramen?

A

Ostium

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19
Q

To which side is each atrial septum?

A

The septum secundum is to the right of the septum primum

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20
Q

What is non closure of the foramen called?

A

Atrial Septal Defect (ASD)

21
Q

What are the types of ASD?

A

1) Foramen Secundum defect
2) Endocardial cushion and foramen primum defects
3) Sinus Venosus defect
4) Common Atrium

22
Q

What is the foramen primum?

A

An inferior foramen between the septum primum and endocardial cushion prior which closes prior to septum secundum growth.

23
Q

What seperates the left and right ventricles?

A

A muscular interventricular septum at the base and membranous interventricular septum at the top.

24
Q

How does the muscular interventricular septum form?

A

From the bottom of the primitive ventricle leaving an interventricular foramen at the top

25
Q

How does the membranous interventricular septum replace the interventricular foramen?

A

The aorticopulmonary septum rotates & fuses with the muscular septum forming the membranous one

26
Q

How common is Ventricular Septal Defect?

A

VSD is the most common congenital heart disease (~25% of all CHD)
Most ocmmon in men
MEmbranous is more common than muscular

27
Q

What happens to small VSDs?

A

up to half close spontaneously

28
Q

What sections of the heart tube give rise to the aorta/pulmonary trunk?

A

The bulbus cordis (BC) and Truncus Arteriosus (TA)

29
Q

How does the aortiocopulmonar (conotruncal) septum form?

A

1) Mesenchymal cells from the neural crest proliferate in the BC & TA walls
2) Bulba & Truncal ridges form
3) Ridges connect formin the septum.

30
Q

What happens to the aorticopulmonary septum after its formed?

A

It twists 180degress due to streaming past of blood causing the overlap of the aorta & Pulmonary trunk

31
Q

What gives rise to the AV node and bundle of his?

A

Cells of the AV canal and the Sinus Venosum

32
Q

What gives rise to the SA node?

A

Cells of the Primordial atrium and Sinus Venosum

33
Q

What happens when conducting tissue is abnormal?

A

Cot death or Sudden Infant Death Syndrome (SIDS)

34
Q

From what structure is the pericardium derived?

A

The intra-embryonic coelom

35
Q

What tissue gives rise to the parietal and fibrous pericardium?

A

Somatic Mesoderm

36
Q

What tissue gives rise to the visceral pericardium?

A

Splanchnic Mesoderm

37
Q

Which CHDs are most common in women?

A

ASD & PDA (Patent Ductus Arteriosus)

38
Q

What causes PDA?

A

The mother having a rubella infection while pregnant

39
Q

What often causes septal defects?

A

Maternal alcohol abuse

40
Q

Name some chromosomal CHDs

A

Downs Syndrome
Turners Syndrome

41
Q

What are the causes of CHDs?

A

Generally multifactorial:
Maternal Infection
Maternal substance abuse
Genetics
Maternal drug/radiation treatments

42
Q

What is transposition of the great vessels?

A

A congenital heart disease.
The pulmonary trunk no longer crosses the base of the aorta, instead they run parallel. And there is PDA.
A common cause of cyanotic disease in newborns

43
Q

What is associated with Transposition of the Great Vessels?

A

ASD/VSD

44
Q

What does PDA allow?

A

Exchange of blood between deoxygenated pulmonary & oxygenated systemic circulation

45
Q

What causes Transposition of the great vessels?

A

Either:
Failure of the aorticopulmonary septum to spiral
Defective Migration of neural crest

46
Q

What is tetralogy of fallot?

A

A 4 part congenital heart disease.
- Pulmonary stenosis
- VSD
- Dextroposition of Aorta (Aorta right over the VSD)
- Right ventricular Hypertrophy

47
Q

What is the consequence of dextroposition of the aorta in a case of Tetralogy of Fallot?

A

The Aorta recieves blood from both ventricles so its not properly oxygenated

48
Q

What causes Tetralogy of Fallot?

A

An unequal division of the conus due to anterior displacement of the aorticopulmonary septum