Embryology 1 Flashcards
(83 cards)
1
Q
What are the 4 major stages in heart development?
A
- Primitive heart tube
- Heart looping
- Atrial and ventricular septation
- Outflow tract septation
2
Q
When does heart development begin?
A
3rd week
3
Q
What forms the circulatory system?
A
Lateral plate mesoderm
4
Q
How are the 2 primitive heart tubes formed?
A
Angiogenic cell islands collect in the lateral plate mesoderm, move towards the midline and coalesce
5
Q
What is the first major system to function in the embryo?
A
Cardiovascular system
6
Q
When does the primordial heart start to function?
A
Beginning of 4th week
7
Q
Why does the cardiovascular system begin to function so early?
A
The embryo is rapidly growing and nutrition by diffusion is not enough to satisfy the growing embryo
8
Q
Where do blood vessels first appear?
A
- Wall of the yolk sac
- Allantois
- Connecting stalk
- Chorion
9
Q
What are angioblastic cords?
A
Paired endothelial strands
10
Q
When do angioblastic cords appear?
A
3rd week
11
Q
Where do angioblastic cords appear?
A
Cariogenic mesoderm
12
Q
What do angioblastic cords canalize to form?
A
Heart tubes
13
Q
What is formed when the tubular heart joins blood vessels in other areas?
A
Primordial cardiovascular system
14
Q
What is the pericardium derived from?
A
Intra-embryonic coelm
15
Q
What are the parietal and fibrous layers of the pericardium formed from?
A
Somatic mesoderm
16
Q
What is the visceral layer of serous pericardium derived from?
A
Splanchnic mesoderm
17
Q
What are the structures on the primitive heart tube from cranial to caudal end?
A
- Truncus arteriosus
- Bulbus cordis
- Ventricle
- Atrium
- Sinus venosus
18
Q
What structures are found in the arterial end of the primitive heart tube?
A
- Truncus arteriosus
- Bulbus cordis
- Ventricle
19
Q
What structures are found in the venous end of the primitive heart tube?
A
- Atrium
- Sinus venosus
20
Q
How many horns does the sinus venosus have?
A
2
Right and left
21
Q
Where does each horn get blood from?
A
- Yolk sac via vitelline vein
- Placenta via umbilical vein
- Body of the embryo via the common cardinal vein
22
Q
What does the truncus arteriosus continue cranially with?
A
Aortic sac
23
Q
What arises from the aortic sac?
A
Aortic arches
24
Q
Where do the aortic arches terminate?
A
Dorsal aorta
25
Which way does the primitive heart tube loop?
Anti-clockwise
26
Which regions of the primitive heart tube grow fastest?
- Bulbus cordis
| - Ventricle
27
What do the bulbus cordis and ventricle form?
They form a u-shape known as the bulboventricular loop
28
How does the heart come to face the right?
The heart tube loops to the left side
29
What is the most frequent positional abnormality of the heart?
Dextrocardia
30
What other condition is dextrocardia associated with?
Situs inversus
31
When does the partitioning of the primordial heart occur?
Around the 27th to 37th day of embryonic development
32
What does the partitioning of the primordial heart involve?
1 or 2 actively growing masses of tissue
33
What does endocardial cushion formation result in?
Separation of the right atrioventricular opening from the left atrioventricular opening
34
What does septum formation result in?
Separation of the right atrium from the left atrium and right ventricle from the left ventricle
35
What are many cardiac malformations associated with?
Defective formation of endocardial cushion and septum formation
36
What can defective endocardial cushion and septum formation result in?
- Atrial septal defect
| - Ventricular septal defect
37
When does the partitioning of primordial atrium into left and right atria take place?
Starts towards the end of the 4th week
38
What develop during the portioning of the primordial atrium into left and right atria?
- Septum primum and foramen primum
| - Septum secondum and foramen secundum
39
What is the ostium primum?
Opening between septum primum and endocardial cushion
40
Where is the foramen secundum formed?
At the upper end of septum primum
41
Where is the septum secundum formed?
On the right of the septum primum
42
After formation what does the septum secundum do?
It grows and overlaps the foramen secundum.
43
Why is the septum secundum incomplete?
Perforated by oval foramen
44
What is the opening in the septum primum?
Foramen secundum
45
What is the opening in the septum secundum?
Foramen ovale
46
What is the role of the oval foramen?
- Allows most of the blood to pass from the right atrium to the left atrium
- Prevents the passage of blood in the opposite direction
47
What normally happens to the oval foramen after birth?
- It normally closes
| - Increased pulmonary blood flow and shift of pressure to the lift atrium
48
What happens to the septum primum after birth?
It fuses with the septum secundum
49
What is the oval fossa in the adult heart?
A remnant of foetal oval foramen
50
What does non-closure of the oval foramen result in?
Atrial septal defect
51
What are the 4 clinically significant types of ASD?
- Foramen secundum defect
- Endocardial cushion defect
- Sinus venosus defect
- Common atrium
52
Who do atrial septal defects affect more often?
Females
53
What is the first stage in the partitioning of the primordial ventricle?
Muscular ventricular septum forms. Opening is called intraventicular foramen
54
What happens in the partitioning of the primordial ventricle after the muscular ventricular septum forms?
Aorticopulmonary septum rotates and fuses with muscular ventricular septum to form membranous interventricular septum, closing interventricular foramen
55
What is the final stage in the partitioning of the primordial ventricle?
Growth of endocardial cushions separates atria from venticles and contributes to both atrial septation (distally) and membranous portion of the interventricular septum (proximally)
56
What happens during the 5th week of development?
Partitioning of bulbus cordis and truncus arteriosus
57
What must happen before the partitioning of the bulbus cordis and truncus arteriosus?
Active proliferation mesenchymal cells in the walls of the BC and TA
58
What happens during the partitioning of BC and TA?
- Bulbur ridges and truncal ridges are formed
- They undergo 180 degree spiralling resulting in the formation of aorticopulmonary septum
- This septum divides BC and TA in to aorta and pulmonary trunk
59
What causes the spiralling of the bulbur and truncal ridges?
Streaming of blood from the ventricles
60
What is the most common type of congenital heart defect?
Ventricular septal defect
61
Where do VSDs appear?
Can appear in any part of the septum
62
What is the outcome of most small VSDs?
Close spontaneously
63
What is the most common type of VSD?
Membranous
64
Who do VSDs most commonly affect?
Males
65
Where are early pacemakers found?
Primordial atrium and then sinus venosus
66
When does the SA node develop?
5th week
67
Where is the location of the SA in and adult?
High in the right atrium near the entrance of the SVC
68
What do the AV node and bundle develop from?
Cells of AV canal and sinus venosus
69
What is cot death/sudden infant death syndrome?
Abnormalities of conducting tissue
70
What is the fate of the aortic sac?
Aortic arches
71
What is the fate of the bulbus cordis?
- Right ventricle
| - Parts of the outflow tracts
72
What is the fate of the primitive ventricle?
Left ventricle
73
What is the fate of the primitive atrium?
Parts of the right and left atria
74
What is the fate of the sinus venosus?
- Superior vena cava
| - Right atrium
75
What are the factors affecting the aetiology of congenital heart disease?
- Rubella infection in pregnancy
- Maternal alcohol abuse
- Maternal drug treatment and radiation
- Genetic
- Chromosomal
76
What congenital heart diseases are more common in females?
- Atrial septal defect
| - Patent ductus arteriosus
77
What type of defects can maternal alcohol abuse lead to?
Septal defects
78
What is a common cause of cyanotic disease in newborn infants?
Transposition of great vessels
79
What is transposition of great vessels associated with?
- ASD
| - VSD
80
What does transposition of great vessels permit?
Exchange of systemic and pulmonary circulation
81
What are the 2 causes of transposition of great vessels?
- Failure of aorticopulmonary septum to take a spiral course
| - Defective migration of neural crest cells
82
What are the 4 cardiac defects that make up the teratology of fallot?
- Pulmonary stenosis
- Ventricular septal defect
- Dextroposition of aorta
- Right ventricular hypertrophy
83
What is the cause of fallot?
Unequal division of the conus due to anterior displacement of aorticopulmonary septum
