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ANAT0005 > Heart Development > Flashcards

Heart Development Flashcards

1
Q

What is the function of the foetal circulation?

A

Carry nutrients and gases around the body

Allow exchange at the placenta

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2
Q

What are the 3 foetal blood circuits that need to form in the embryo?

A
  1. Vitelline circuit
  2. Umbilical circuit
  3. Common cardinal circuit
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3
Q

What two structures does the vitelline circuit innervate?

A

Yolk sac and embryo

The liver develops at the site where the vitelline veins empty into the sinus venosus

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4
Q

What two structures does the umbilican circuit innervate?

A

Embryo and placenta

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5
Q

What two structures does the common cardinal circuit innervate?

A

Anterior cardinal veins drain in the head and arms

Posterior cardinal veins drain the trunk and legs

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6
Q

What are the main steps of heart formation?

A
  1. Heart forming mesoderm migrates to the anterior end of the embryo
  2. The cells in the mesoderm destined to be heart cells form a crescent-shaped tube at the cranial border of the disc
  3. The two ends of the tube meet in the midline under the gut to form one tube
  4. The heart tube loops
  5. The atria and ventricles are gradually separated by septation
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7
Q

How many days into development do heart-forming cells appear?

A

17 days

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8
Q

How many days into development does the heart begin to beat?

A

23 days

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9
Q

When does septation begin?

A

27 days

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10
Q

When does septation end?

A

37 days

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11
Q

What are the two heart fields that contribute to heart formation?

A

Primary heart field - develops into the left and right atria and left ventricle

Second heart field - becomes the right ventricles and the outflow tract

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12
Q

What does the cardiac crescent give rise to?

A

The primary heart tube

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13
Q

Describe the components of the primary heart tube

A

On each side of the heart tube there is:

  • an inlet/venous end (sinus venosus)
  • an atrial region
  • a ventricle region

The two sides have a common conotruncus

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14
Q

Which are the two planes in which the heart tube folds

A

Anterioposteriorly

Bilaterally

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15
Q

Describe the anterioposterior folding of the heart tube

A

Folding of the head brings the region of the heart tube under the head and foregut

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16
Q

Describe the bilateral folding of the heart tube

A

Folding of the gut ventrally brings the two endocardial tubes together and fuse to form a single midline heart tube under the completed foregut

17
Q

What are the steps of the division of the heart into its many compartments?

A
  1. Division of the atrioventricular canal
  2. Division of the atria
  3. Division of the ventricles
  4. Partitioning of the outflow tract
18
Q

Describe the division of the atrioventricular canal

A

The atrioventricular canal separates the atria and ventricles by the formation of thickenings in the canal wall called endocardial cushions

The superior and inferior endocardial cushions meet in the midline, dividing the atrioventricular canal into right and left canals

The two canals initially empty into the future left ventricle

Connective tissue from the endocardial cushions invades the myocardium to form the annulus fibrosus which will insulate the atria from the ventricles - except at the passage of the atrioventricular bundle

19
Q

Describe the division of the atria

A
  1. Septum primum grows down from the roof of the primitive atrium towards the AV cushions forming the foramen primum
  2. The septum primum meets the endocardial cushions, closing the foramen primum
  3. Apoptosis in the wall of the septum primum near the room of the atrium forms the foramen secundum, allowing blood to flow from the right to the left atrium
  4. A second, more rigid septum secundum begins to grow to the right of the septum primum
  5. The space between the edge of the septum secundum and the endocardial cushion is called the foramen ovale
20
Q

What is the foramen ovale?

A

The space between the edge of the septum secundum and the endocardial cushion

21
Q

What happens to the foramen ovale following birth?

A

Functional closure of the foramen ovale occurs because of pressure differences between the two atria

The tissues of the two septa also grow together such that they become anatomically fused

22
Q

What is the function of the foramen ovale in the fetal circulation?

A

During embryonic development, oxygenated blood from the placenta delivered via the inferior vena cava is shunted from the right atrium to the left atrium via the foramen ovale

The septum secundum forms a valve across the foramen secundum

This ensures the direction of the blood is unidirectional

23
Q

Describe the division of the ventricles

A
  1. The atrioventricular canal shifts from the primitive centricle on the left towards the developing interventricular septum in the middle
  2. The right ventricle expands in the outlet region
  3. Both ventricles expand caudally
  4. The muscular septum develops
24
Q

Describe the partitioning of the outflow tract

A
  1. Neural crest cells migrate to the truncus arteriosuss= and conus cordis, transform into mesenchymal tissue and proliferate to form ridges
  2. The two truncoconal ridges grow forward toward each other, fuse first at the tuncoconal transition and then zip distally and proximally
  3. As the truncoconal ridges grow toward the ventricles, they contribute to the interventricular septum
  4. The ridges spiral around one another
  5. The ridges fuse
25
Q

Features of the fetal heart at 12 weeks

A

Foramen ovale and ductus arteriosus maintain the foetal circulation

The ventricles are almost fully separated

The interatrial shunt is fully functional

The outflow tract is fully divided

26
Q

What is the ductus arteriosus?

A

Connection between the pulmonary artery and aorta

27
Q

What is the function of the ductus arteriosus?

A

Shunts blood away from the lungs and into the aorta

28
Q

Describe fetal circulation

A
  1. Umbilical vein carries oxygenated blood from the placenta to the inferior vena cava
  2. Oxygenated blood is shunted past the liver and into the inferior vena cava by the ductus venosus
  3. The inferior vena cava enters the right atrium
  4. The blood passes through the foramen ovale into the left atrium, down to the left ventricle and into the aorta
  5. The first major branches to the aorta take the blood into the developing brain
  6. Deoxygenated blood from the head, arms and thorax passes through the superior vena cava and enters the right atrium
  7. The blood passes through the right ventricle and into the pulmonary artery
  8. The ductus arteriosus causes the blood to bypass the lungs as it enters the aorta instead of the pulmonary artery
  9. Deoxygenated blood returns to the placenta in umbilical arteries
29
Q

What are the remnants of the fetal atrium in the adult heart?

A

Smooth walled parts = sinus venosus

Rough walled parts = pectinate muscle

30
Q

Describe the function of the early heart tube

A

Early heart tube contracts slowly and unidirectionally from the caudal end

Parts of the heart that develop from the early tube retain this slower pace and forms the pacemaker system

The myocardium of the chambers conduct more quickly

31
Q

What is the inlet of the early heart tube?

A

Where all the embryonic veins drain

Caudal

32
Q

What is the conotruncus of the early heart tube?

A

Where are the arteries arise - arterial end

Rostral

33
Q

Why does a patent interatrial foramen form?

A

Foramen secundum is too large

Septum secundum is too short

Foramen primum does not close

34
Q

Which cell populations contribute to heart development?

A

Precardiac mesoderm

Cardial neural crest cells

35
Q

What does the precardiac mesoderm give rise to?

A

The endocardium lining the heart

The epicardium covering the heart

The primary heart field

The secondary heart field

36
Q

What does the primary heart tube form?

A

The left ventricle and the primary atria

37
Q

What does the secondary heart tube form?

A

Right ventricle

Atria

Outflow tract

38
Q

What do the cardiac neural crest cells form?

A

Outflow tract

Pro-epicardial cells of epicardial layer and coronary blood vessels

39
Q

Describe what happens to the heart following childbirth

A

The rise in the left atrial pressure pushes the septum primum against the septum secundum and closes the foramen ovale

The change in blood oxygen levels and blood flow closes the ductus venosus and ductus arteriosus

ANAT0005 (6 decks)

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