Heart Development Flashcards

1
Q

When do the primordial heart and vascular system begin to appear in an embryo?

A

middle of the 3rd week

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2
Q

When does the heart start to function?

A

beginning of the 4th week

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3
Q

From what three main embryonic structures does the cardiovascular system develop?

A
  1. splanchnic mesoderm - forms heart promordium
  2. paraxial and lateral mesoderm - near otic placodes
  3. neural crest cells - from between otic vesicles and caudal end of 3rd somite pair
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4
Q

What is the structure whose name is crossed out in blue?

What is its origin and significance?

It is paired. What do the two of them form and how?

A

angioblastic cords

  • earliests signs of heart dev. (during 3rd week)
  • paired endothelial cell groups which leave the cardiogenic splanchnic mesoderm just below the pericardial intraembryonic coelom
  • later canalize to form endocardial tubes
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5
Q

What are the steps of the general process for the initial formation of the embryonic vascular system?

(acronym)

A

A B C F V A

All Boston Cabbies Find Vagina Appealing

  • begin at end of 3rd week
  1. Angioblast Differentiation - mesenchymal cells > angioblasts
  2. Blood Island Formation - angioblasts aggregate > blood islands
  3. Cavities - intercellular clefts combine to form cavities in islands
  4. Flattening - angioblasts flatten to form endothelium
  5. Vasuculogenesis - endothelium-lined cavities fuse to form vessels
  6. Angiogenesis - endothelial budding > new vessels sprout from old
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6
Q

What forms from the endocardial tubes?

How and when?

A

Tubular Heart

  • endocardium of the heart
  • the 2 endocardial tubes fuse medially during “rolling” or transverse folding
  • 4th week
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7
Q

What induces early development of the heart?

A

stimulation from the anterior endoderm

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8
Q

What 3 paired veins drain into the tubular heart of a 4-week embryo?

They are marked here by the red dots.

A
  • anterior, posterior + common cardinal veins - return O2 poor blood from embryo body
  • vitelline veins - return O2 poor blood from yolk sac
  • umbilical veins - carry O2 rich blood from placenta

(orientation of veins around heart seen below)

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9
Q

What is this cavity on the caudal end of the embryonic heart?

A

sinus venosus

  • receives blood from umbilical, vitelline and cardinal veins
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10
Q

What is this paired structure?

What does it come from and later become?

A

Myoepicardial Mantle

  • thickening of the splanchnic mesoderm
  • it is the dorsal wall of the primordial pericardial cavity
  • later becomes the epi- and myocardium layers

(shown w/ red arrow below, eventually even the dorsal side of the MEM fuses to completely surround the heart tube )

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11
Q

What two embryonic movements explain the movement and fusion of the parts of the primordial heart?

A

Flexion (AKA head/tail fold, longitudinal folding)** **- explains hearts movement from “above” head to in the chest

Rolling (AKA transverse folding) - explains joining of paired heart primordia in the mesoderm

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12
Q

What is #7?

How does it form and what is its fate?

A

Dorsal Mesocardium

  • a dorsal suspension of the heart tube and its surroundings by a stalk of mesoderm
  • forms when the intraembryonic coelom fuses ventrally, but not dorsally
  • eventually disappears as the coelom fuses completely to form the pericardial cavity
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13
Q

What eventually becomes the parietal pericardium?

A

**somatic mesoderm **of the cardiogenic area

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14
Q

What is the area marked by the question mark?

What does it become and how?

A

Truncus Arteriosus

  • cranial end of the primitive heart tube coming from the primitive ventricle and bulbus cordis
  • becomes the aorta and pulmonary trunk after septation by the spiral aorticopulmonary septum
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15
Q

What is the area indicated by the question mark?

What does it become?

A

bulbus cordis

  • rounded structure in primitive heart tube distal to primitive ventricle
  • gives rise to outflow part of the right ventricle (infundibulum)
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16
Q

What is the red question mark?

What does it become?

A

Right Sinus Horn

  • differentiates into the SVC and IVC leading into the sinus venarum
17
Q

What is the blue question mark?

What does it become and how?

A

Left Sinus Horn

AKA Duct of Cuviér

  • becomes the coronary sinus when the sinu-atrial opening moves rightward
18
Q

What are the green structures at the sinu-atrial opening?

The dorso-cranial fusion of these two structures forms what?

And what is its fate?

A

right and left veinous valves

  • form the septum spurium as they fuse cranially
  • septum spurium and left venous valve incorporate into septum primum
19
Q

How do the ends of the primitive heart tube move in order for the chambers to arrange normally?

What is this new, folded arrangement called?

A

venous end moves backwards and upwards to form atria

arterial end moves forwards and downwards to form ventricles

  • called the bulboventricular or cardiac loop
20
Q

How does the atrioventricular canal septate?

A
  • paired dorsal and ventral AV endocardial cushions form centrally within the canal
  • the AV cushions proliferate dorsoventrally until they fuse
  • tissue around the resulting right and left AV canals is induced by the surrounding myocardium to become the bi- and tricuspid valves
21
Q

What forms from the inferior portion of the right venous valve?

A

Eustachian and Thebesian Valves

22
Q

How do the pulmonary veins form?

A
  • a single primordial pulmonary vein grows out of the dorsal left atrium near the septum primum
  • atrial growth incorporates the primordial pulmonary vein and its main tributaries into the atrial wall, forming the final 4 pulmonary veins
23
Q

What are the origins of the smooth and rough parts of the atria?

A

smooth parts - sinus venarum cavarum and smooth left atria form from incorporation of veinous tissue into atrial wall

rough parts - auricles and pectinate muscles form from common atrium

24
Q

How is the primordial atrium partitioned?

A
  1. thin, cresecent-shaped septum primum grows antero-inferiorly towards EC cushions from the postero-superior wall of the common atrium
  2. foramen primum forms as septum approaches EC cushions
  3. apoptotic holes in septum primum form **foramen secundum **above f. primum
  4. foramen primum closes when septum primum fuses with left side of EC cushions
  5. thicker **septum secundum **grows just right of primum in opposite direction
  6. **foramen ovale **forms from overlap of the two septa at foramen secundum
  7. cranial septum primum disappears forming valve of foramen ovale
25
How does the interventricular septum form?
1. **muscular IV septum** arises as a ridge in the floor of the ventricle 2. at first, just ventricular dilation pushes muscular septum upward 3. then, myoblast proliferation increases size further 4. an **IV foramen** persists at the caudal end of the septum 5. **membranous IV septum** forms finally from 3 sources: * **left and right bulbar ridges** * **endocardial cushions**
26
What forms the parietal pericardium?
**somatic mesoderm**
27
what forms the visceral pericardium?
**mesothelial cells** from septum transversum
28
What forms the ridges which go on to septate the heart tube during the formation of the large arteries?
**mesenchymal cells **from **neural crest cells** which migrate through pharyngeal arches
29
Describe the septation of the bulbus cordis and truncus arteriosus.
* **mesenchymal cells** originating from **neural crest** cells migrate into bulbus cordis * these cells form **bulbar** and **truncal ridges** which spiral 180-270 degrees through the bulbus cordis and truncus arteriosus * ridges proliferate centrally into the bulbotruncal lumen and fuse to complete the septum * a **hook** septum forms superiorly from the spiral septum to complete the separation of the pulmonary circulation
30
How do the semilunar valves form?
**left and right valvulae** - bulbar ridges (AKA primary endocardial cushions) **anterior and posterior valvulae** - secondary endocardial cushions
31
What is the malformation in which all viscera are mirrored?
**situs inversus totalis**
32
What is the malformation in which only the heart is mirrored to the other side of the thorax?
**dextrocardia**
33
What is the name of incomplete closure of septum primum and secundum?
**atrial septal defect** or **persisting foramen ovale**
34
What is the name of the malformation resulting in faulty separation of ventriculars? How does it occur?
**Ventricular Septal Defect** **-** muscular and membranous parts do not fuse
35
How does a **transposition of the great vessels** occur? What is it?
- aorticopulmonary septum twists only 90 degrees - a swapping of the vessels that each ventricle feeds into such that: * deoxygenated blood from the right ventricle feeds into the aorta and systemic circulation * oxygenated blood from the left ventricle feeds into the pulmonary trunk and circulation
36
What is the name of the malformation with four parts? What are the four parts?
**Tetralogy of Fallot** 1. narrow pulmonary valve 2. thick right ventricular wall 3. aortic displacement over IV septal defect 4. IV septal defect