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Embryology > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

What is the function of the cardiovascular system post-natally (after birth)?

A

Deliver blood to the lungs for O2 and distribute oxygenated blood to the body

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2
Q

What is the function of the fetal/embryonic cardiovascular system?

A

Blood receives O2 from the placenta, as lungs are still developing

  • results in mechanisms for embryonic cardiovascular system to bypass embryonic lungs, but this must be remodeled after birth
  • Foramen ovale and ductus arteriosus
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3
Q

Where do cardiac progenitor cells come from? When do they migrate? To where?

A

From epiblast

  • Migrate into splanchnic mesoderm, then cranially above oropharyngeal membrane, forming the primary heart field
  • Week 3
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4
Q

What are Primary Heart Field cells induced by? What do they form?

A

Underlying endoderm - induced to form cardiac myoblasts and blood islands

  • Form a horseshoe-shaped cardiogenic area by Day 19
  • cardiac cells surround developing blood islands
    • two laterally situated tubes are present
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5
Q

How does the developing heart go from being rostral to the buccopharyngeal membrane to being in position in the thorax?

A

Embryo is folding

  • longitudinal folds - brings cranial limb (and developing heart) ventrally
  • Lateral folding causes lateral part of “horseshoe” to fold ventrally as well
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6
Q

How is the heart tube formed?

A

Via the folding of the embryo

  • Horseshoe shaped cardiogenic area is folded ventrally, where it fuses (except at caudal-most end)
  • Fuses with blood vessels so that it receives blood at the caudal end and expels blood at the rostral end
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7
Q

What types of embryonic tissues contribute to the formation of the heart?

A 
Epiblast (cardiac precursor cells)
Coelomic epithelium (myocardium and conducting system)
Neural crest (septa and media of the great vessels)
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8
Q

What is the heart tube initially suspended in?

A

Dorsal mesentery

- the breakdown of this layer results in the formation of the transverse pericardial sinus

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9
Q

What layers is the primitive heart tube composed of?

A

Endoderm
Mesoderm - develops into two layers - myocardium and cardiac jelly
- Cells from splanchnic mesoderm migrate and give rise to epicardium

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10
Q

How is the primitive heart structured?

A

One tube with common inflow tract at bottom and common outflow tract at top
- As cells proliferate, they form segments/bulges that will form different parts of the heart

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11
Q

What are the parts of the primitive heart?

A

From bottom to top:

  • Sinus venosus - common inflow tract
  • Primordial atrium
  • Primordial ventricle
  • Bulbus cordis
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12
Q

What three structures does the bulbus cordis give rise to?

A

Truncus Arteriosus
Conus cordis
Primordial (trabeculated) right ventricle

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13
Q

What structures arise from the sinus venosus?

A

Oblique vein of left atrium
Coronary sinus
Right atrium

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14
Q

What structures arise from the primordial atrium?

A

Parts of right and left atria

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15
Q

What structures arise from the truncus arteriosus?

A

Roots of great arteries

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16
Q

What structures arise from conus cordis?

A

Outflow of ventricles

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17
Q

When does the cardiac loop form?

A

Day 22 - Day 28 (by end of fourth week)

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18
Q

What happens during the looping of the heart?

A

Atria are brought dorsally and developing ventricles sit ventrally

  • Bulbus cordis moves anteriorly
  • Ventricle moves anteriorly, inferiorly, and to the left side
  • Atrium shifts posteriorly and superiorly
  • Bulbus cordis is divided into thirds, from proximal to distal: primitive right ventricle, conus cordis, truncus arteriosus
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19
Q

Why does the cardiac loop form?

A

Differential growth

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20
Q

What happens during the partitioning of the heart?

A

The continuous inflow and outflow lasts until day 27

  • Endocardial cushions develop from cardiac mesoderm, create atrioventricular canals
  • These endocardial cushions contribute to separating the atria and ventricles and the outflow tract
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21
Q

What happens in the conotruncal region?

A

The tissue is invaded by neural crest cells

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22
Q

Where does the sinus venosus receive blood from? Unilaterally or bilaterally?

A

Bilaterally, from three veins

  • Vitelline (from yolk sac)
  • Umbilical (from placenta)
  • Common cardinal vein (from embryo proper)
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23
Q

What happens to the veins during the 5th week?

A

There is a great venous shift to the right (sinuatrial orifice shifts right)

  • right umbilical and left vitelline veins become obliterated, later the left common cardinal vein is lost
  • All that remains of the left sinus horn is the oblique vein of the left atrium and the coronary sinus, which drains blood form the heart
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24
Q

What happens to the right sinus venosus horn?

A

Enlarges and becomes incorporated into right atrium (becomes the sinus venarum)
- Incorporation results in formation of two valves (valve of the IVC and the valve of the coronary sinus)

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25
Q

What is the crista terminalis?

A

The dividing line between the trabeculated part of the right atrium and the sinus venarum

26
Q

Endocardial cushions

A

Thickenings of the sub-endocardium and function in formation of atrial and ventricular walls, AV canals, and aortic and pulmonary channels

27
Q

In the bulbus cordis, what do the endocardial cushions form from? What is their function?

A

Form from neural crest

- function to partition the truncus arteriosus

28
Q

Between the atria and ventricle, what are endocardial cushions formed from? What is their function?

A

NOT derived from neural crest

- Partition of the atria, atrioventricular canals, and interventricular septum

29
Q

Septum Primum

A

A sheet begins to grow downward from the rood of the common atrium
-descends towards endocardial cushions

30
Q

Ostium primum

A

A gap that remains in the septum primum

  • allows shunt of oxygenated blood from Right to Left
  • Endocardial cushions grow superiorly from the atrioventricular canal and close ostium primum
31
Q

Ostium secundum

A

Perforations in the upper portion of the septum that appear before the closure of the ostium primum

32
Q

Septum secundum

A

A ridge of tissue that forms to the right and in front of the septum primum

  • covers the hole in the septum primum but still has opening called oval foramen
  • portion of septum primum that sits behind the oval foramen is termed the valve of the oval foramen
33
Q

What is the function of the foramen ovale?

A

Allows blood to pass from the right atrium into the left atrium and bypass the right ventricle (which in turn bypasses the pulmonary trunk and the lungs)
- closes after birth, becomes known as fossa ovale

34
Q

Probe patency

A

An anatomic variation in 10-20% of individuals

- oval foramen remains patent but does not shunt blood (asymptomatic)

35
Q

What is the left atrium formed from?

A

A trabeculated part that arises from the atrium proper (auricle) and a smooth-walled part that arises from the pulmonary veins

36
Q

What is the right atrium formed from?

A

A smooth-walled part that derives from the sinus venosus and a part containing the pectinate muscle that derives from the atrium proper

37
Q

What happens to the left horn of the sinus venosus?

A

Forms coronary sinus and oblique vein of left atrium

38
Q

What happens to the right horn of the sinus venosus?

A

Incorporated into right atrium (sinus venarum)

39
Q

What does the right sinuatrial valve develop into?

A

Valve of inferior vena cava

Valve of coronary sinus

40
Q

ASD

A

Atrioseptal defect

41
Q

Patent foramen ovale

A

Either septum primum has regressed too much or septum secundum is underdeveloped
- abnormal flow between atria

42
Q

What does the primitive ventricle give rise to?

A

Most of the left ventricle and part of the inlet to the right ventricle

43
Q

How long are the ventricles in communication with each other during development?

A

The 5th week

- there is a common AV canal

44
Q

How does the AV canal become blocked off from the right ventricle?

A

The AV canal becomes bound by AV endocardial cushions (superior and inferior) and two lateral AV cushions. At this point, the AV canal communicates only with the left ventricle
- the right is blocked by the bulbo-ventricular flange

45
Q

How does the AV orifice communicate with both primitive ventricles after it was previously blocked off?

A

The superior and inferior cushions project farther into the lumen and fuse, this divides the common AV canal into right and left canals

46
Q

What are the AV valves formed from?

A

Formed from Mesenchyme derived from the ventricular myocardium
- the valves remain connected to the muscular wall by tendinous cord

47
Q

What is the interventricular septum formed from?

A

Muscular ingrowth (differential growth of myoblasts)

  • conus septum
  • endocardial cushions
48
Q

What initiates the process of cavitation?

A

Blood flow into ventricles

49
Q

What createsthe trapeculated appearance of the ventricular walls?

A

Blood flow (cavitation)

50
Q

Chordae tendinae

A

Structures attached to cusp of valves, derived from mesenchyme
- form cusps of AV valves

51
Q

In formation of the ventricles, what does the bulbus cordus give rise to?

A

most of the right ventricle

52
Q

In formation of the ventricles, what does the truncus arteriosus give rise to?

A

The distal portions of both ventricles (right - infundibulum and conus arteriosus; left - aortic vestibule)

53
Q

In ventricle formation, what happens to the medial walls?

A

The medial walls of each ventricle become opposed and merge, forming the muscular interventricular septum

54
Q

What is the communication that is between the ventricles initially?

A

The IV foramen that exists between the IV septum and the fused endocardial cushions

55
Q

What is the IV foramen reduced by?

A

The conus septum

56
Q

What is the IV foramen eventually closed by?

A

A growth from the endocardial cushions (this is the membranous part of the IV septum)

57
Q

How do the semilunar valves arise?

A

As swellings in the pulmonary and aortic channels and neural crest cells are involved

58
Q

How does the septum form in the truncus arteriosus and conus cordis?

A

Paired ridges (derived from neural crest) form in both the truncus arteriosus and conus cordis (truncus swellings). These swellings grow centrally, into the lumen, and spiral around each other; the ridges fuse, forming a spiral wall that is the aorticopulmonary septum and divides the channels into an aortic and pulmonary channel.

59
Q

Where do 80% of Ventricular Septal defects happen?

A

In the muscular septum

60
Q

How do the semilunar valves form?

A

During conotruncal separation, mesenchymal tubercles appear, forming semilunar cusps

  • tubercles hollow out superiorly to form valves (semilunar sinuses)
  • each valve is made out of 3 cusps hollowed out superiorly
  • neural crest cells invade tissue forming valves

Embryology (3 decks)

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