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Cardiopulmonary I > Development of Heart > Flashcards

Development of Heart Flashcards

1
Q

Dextrocardia

A

The heart is directed to the right side of the body instead of the left side, people who have this disease are at an increased risk of having other congenital heart defects

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2
Q

Endocardial Cushions, why are they important

A

Formation of proper endocardial cushions is a key event in the development of heart, defects in the development of endocardial cushions leads to ASD, VSD, PDA, transposition of the great vessel and other defects

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3
Q

What cells are responsible for forming the endocardial cushions

A

Neural crest cells, they contribute to the cells that form the endocardial cushions.

They also form head and neck structures, individuals with craniofacial defects have an increased risk of developing defect in endocardial cushions

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4
Q

What happens when the atrial septation fails

A

Atrial septal defects arise. Clinical features are:

  1. These are usually asymptomatic
  2. These are usually detected when a murmur is heard, since blood is being pushed into the right side of the heart there will a fixed splitting of S2 due to late closure of the pulmonic valve
  3. Echo is needed for diagnosis
  4. It can be treated without an open heart surgery
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5
Q

Patent foreman ovale

A

It is not considered an ASD since no tissue is missing, it is simply the failure of the two atrial septal to fuse

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6
Q

When does the heart development begin

A

Day 19

  1. Vasculogenesis at the caudal end (cardiac region) leads to formation of horsehoe-shaped endocardial tubues
  2. Medial: becomes dorsal aorta
  3. Later the endocardial tubes become venous structures
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7
Q

Day 20

A

Embryo starts to fold cephalo-caudally and laterally which forms aortic arch.

Right and left endocardial tubes start to come together

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8
Q

Day 21

A

Lateral endocardial tubes differentiate to form the venous structure on each side

  1. Posterial cardinal veins
  2. Anterior cardinal veins
  3. Vitelline veins from the yolk sac

Single heart tube has been formed by the lateral fusion of the right and left endocardial tubies in the cardiogenic region

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9
Q

Day 21 to 23

A

Following structures are present in the cardiogenic region, from cephalic to caudal

  1. Sinus Venosis
  2. Atrium
  3. Ventricle
  4. Bulbis Cordis
  5. Truncus arteriosis
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10
Q

When does heart starts to beat

A

On day 22

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11
Q

Day 22

A

Spanchnopleuric mesoderm around the primitive heart starts to differentiate into two new layers:

  1. Myocardium: heart muscles
  2. Cardiac jelly: extracellular matrix secreted in between the myocardium and primitive endothelium of the heart tube

Mesothelial cells derived from splnachnopleuric mesoderm migrate towards the myocardium and form serous epicardium or visceral epicardium

Primitive pericardial cavity continues to form gaining a parietal layer of methothelial cells

Now there are 4 layers:

  1. Endocardium
  2. Cardiac jelly
  3. Myocardium
  4. Epicardium
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12
Q

Day 23

A
  1. The heart tube surrounded by the cardiac jelly begins to elongate, loop and fold on itself as it moves towards establishing the adult form
  2. The bulbis cordis grows so that it is displaced inferiorily, ventrall and to the right
  3. Sinus Venosis and atrium grow so they are superior and posterior
  4. Second aortic arch appears
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13
Q

What would happen if the heart doesnt fold or loop in proper direction

A

If the heart doesnt fold or loop in the proper direction then either dextracardia or situs inversis would develop.

People with situs inverusus have less chnaces of having congenital anomalies as compared to the people who have dextracardia

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14
Q

Day 25

A

Blood starts to circulate

  1. Ventricle start to differentiate into left and right primitive ventricle as this region increases in size and thickness
  2. The heart also starts to form a right and left atria though differential growth
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15
Q

Day 28

A

Endocardial Cushions form Septum Intermedium

  1. Heart starts the process of producing a seperate systemic and pulmonary circulation
  2. Two seperate masses of tissues (superior/anterior and inferior/posterior endocardial cushions) from the walls of the heart start to grow toward each other at the junction of the atrium with the ventricles
  3. These projections of the walls of the heart form the atrioventricular canals (opening filled with blood) and the septum intermediam (mass of tissue between the atrioventricular canals)
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16
Q

ASD

A
  1. About 20% of down’s syndrome patients have these defects
  2. ASD is thought to be caused by the failure of the endocardial cushion to form properly
    - It may lead to lack of seperation of the mitral and tricuspid valves
    - May relate to the problems of neural crest cells
  3. Clinical symptoms are failure to thrive, need to take a breath during feeding and tachypnea.

Cyanosis can also be present

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17
Q

Partitioning of the embryonic atrium, how does that happen

A
  1. Right horn of the sinus venosus grows larger and starts to be incorporated into the posterior wall for the primitive atrium
    - Anything derived from the sinus venosus will be smooth-walled
  2. As the sinus venosus grows into the atrium, opening for SVC, IVC and coronory sinus starts to become seperate
  3. Pulmonary veins start to grow into the left, posterior wall of the primitive atrium
  4. On day 28 the septum primum grows down from the superoposterior wall of the atrium to being the process of forming a LA and RA, the forman ovale that connect the RA and LA is now called the ostium primum
  5. By 6th week the septum primum meeds and fuses with the septum intermedium, obliterating the ostium primun and forming a complete RA and LA
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18
Q

Early structure of the heart

A
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19
Q

What do endocardial cushions seperate

A

They seperate the atria from the ventricles

20
Q

Explain the formation of the foreman ovale and its unidirectional flow of blood

A

The septum primum first starts to form in a heart when the endocardial cushions have finished to form proper divisions between the atria and the ventricles. However when this septum is just about to seperate the 2 atria completely, controlled cell death causes a hole on the top of this septum primum.

Septum secondum then forms which is a second septum that forms on one side of the septum primum and it itself is a hard septum, it leaves a hole in the middle which forms the foreman ovale. Now the foreman ovale has a hole (through septum secundum) and a valve (septum primum)

21
Q

What happens when the atrial septation fails

A

There will be an atrial septum defects, usually this presents as a murmur, more blood is moving through the right side of the heart than the left side of the heart, this results in a fixed split of the pulmonic valve

22
Q

The three types of atrial septal defects

A
23
Q

What is patent foreman ovale

A

A patent foreman ovale is when the septum primum and septum secondum fail to fuse with each other, this is supposed to happen after birth, usually it is not a problem since the left atrial pressure is higher than the right atrial pressure but it can pose problems later in life nonetheless

It is not an atrial septal defect

24
Q

What does it mean if the VSD is membraneous

A

It is from the top, this is the most common

25
Q

Ventricular Septal Defects

A
  1. Isolated VSDs are the most common
  2. About 80% of these defects occur in the membraneous portion of the interventricular septum, which is perimembraneous
  3. More than half of VSDs close spontaneously until age 5
  4. They have systolic murmurs, which can be detected shortly after birth
26
Q

Septation of the truncus arteriosis

A

The objective here is to divide the single vessel truncus arteriosis into aorta and pulmonary vessels and this is done with the help of conotruncal septum that divides the vessel that grows down and twist. When they grow down they either meet the spetan intermedium or it meets them, there is a dispute in the literature

27
Q

What happens when it fails to form the interventricular septum

A

VSD

28
Q

What happens when the conotruncal ridges dont grow properly

A
  1. Transposition of the great arteries
  2. Pulmonary stenosis
  3. Persistant truncus arteriosis
  4. Tetralogy of Fallot
29
Q

What cells are responsible for the proper growth of conotruncal ridges

A

Neural crest cells

30
Q

Transposition of the great vessels

A
31
Q

Persistent truncus arteriosis

A
32
Q

Tetralogy of Fallot

A
33
Q

Pulmonary Stenosis

A

The more severe the splitting the greater the splitting of S2

34
Q

Aortic Valve Stenosis

A
35
Q

When do the valves begin to function

A

8 weeks

36
Q

How do the chordae tendenae form for the valves

A

Their is controlled cell death that occur behind the chordae tendenae that allows them to start being functional

37
Q

Coarctation of the aorta

A
38
Q
A
39
Q

Arches of the aorta

A

Theoretically there are 6 arches of the aorta but the 5th one never forms in humans. We only need to know the following:

Arch III: It forms the common and part of internal carotid artery in neck

Arch IV: Right subclavian artery on the right and arch of the arota on the left

Arch VI(6): Pulmonary arteries

40
Q

What are the arteries that branch out of the aorta

A

Starting from left

Brachialcephalic artery

Left common carotid artery

Left subclavian artery

41
Q

Define the circulatory system in the embryo

A

There are 3 circulatory systems

  1. Associated with the yolk sac is the vitelline veins
  2. Umbilical veins are associated with the placenta
  3. Cardinal veins serve the embryo
42
Q

What forms the IVC and SVC

A

Right vitellin vein forms the inferior vena cava and the right anterior cardinal vein forms the SVC

IVC is formed by VItelline

43
Q

What is the short cut called that bypasses the liver

A

Ductus venosus

44
Q

What are the 2 important shunts that are normally present at bith

A
  1. Foreman ovale
  2. Ductus arteriosus
45
Q

What is the function of the Eustachian valve

A

It causes the blood to bypass the right atrium and go straight into the foreman ovale and then to the left atrium

46
Q

Explain the circulation system just before and after birth

A

Before birth:

  1. Lungs have very high resistance, minimal blood is made to pass through lungs
  2. Blood comes from the umbilical cord, passes through the liver via ductus venosus, goes into the right atrium where it is shoved by the eustachian tube into the left atrium via the foreman ovale.
  3. Aorta supplies some blood to the lungs via ductus arteriosis

After birth:

  1. New born starts to take breath through their lungs which causes the bradykinens to be released from the fetal lungs
  2. Rise in O2 causes the smooth muscles in the ductus arteriosis to constrict
47
Q

Patent ductus arteriosis

What do you give to inhibit the closure of ductus arteriosis or accelerate the closure of ductus arteriosis

What kind of murmur is there

Where does cyanosis occur

A

To keep: Prostraglandin

To accelerate the closure: Indomethican

Machine like murmur

In the toes, not in the fingers

Cardiopulmonary I (37 decks)

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