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CV > Embryology of heart > Flashcards

Embryology of heart Flashcards

1
Q

Early development of the heart

A

A. Cardiogenic mesoderm migrates to cranial-most extent of embryo.

B. As a result of embryonic folding, the heart migrates caudally though neck and into thorax.

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2
Q

Heart Tube

A

A. Initially forms as paired endothelial-lined tubes.

B. As the embryo undergoes lateral folding the paired tubes fuse, forming one continuous heart tube.

C. The heart tube receives venous blood at its caudal end and pumps arterial blood to the body at its cranial end.

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3
Q

cardiac looping

A

A. Heart elongates and develops 4 dilations: bulbus cordis, ventricle, atrium, sinus venosus.

B. The ventricles grow faster than other regions, causing the heart to loop.

a. The cranial portion bends ventrally, caudally, and to the right.
b. The caudal portion bends dorsally, cranially, and to the left

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4
Q

Heart Dilations: Sinus Venosus

A
  1. Composed of left and right venous horns (receiving blood from major veins).
  2. Left sinus horn forms coronary sinus.
  3. Right sinus horn is incorporated into right atrium (sinus venarum).
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5
Q

Heart dilations: primitive atrium

A

will form auricles of right and left atria.

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6
Q

Final steps in development of right atrium

A

a. Sinus venosus is incorporated into right atrium and forms sinus venarum.
b. Original embryonic atrium forms atrial auricle.

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7
Q

Final steps in development of left atrium

A

a. Proximal portion of pulmonary vein is incorporated into left atrium and forms smooth walled portion of chamber.
b. Original embryonic atrium forms atrial auricle.

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8
Q

Heart dilations: primitive ventricle

A

will form trabeculated portion of left ventricle

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9
Q

Heart dilations: bulbus cordis

A
  1. Caudal portion forms trabeculated region of right ventricle.
  2. Conus cordis (midportion) will form outflow region of both ventricles (right ventricle – conus arteriosus; left ventricle – aortic vestibule)
  3. Truncus arteriosus (cranial portion) will form pulmonary trunk and aorta.
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10
Q

when do coordinated contractions begin?

A

week 4

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11
Q

circulation through primitive heart

A

B. Blood enters through sinus venosus → primitive atrium → primitive ventricle → bulbus cordis → aortic sac → to embryo.

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12
Q

partitioning of the atrium

A
  1. Step 1 – septum primum forms; this is a thin, membranous septum.
  2. Step 2 – ostium primum forms; this is a short-lived opening along the inferior portion of the septum primum.
  3. Step 3 – ostium primum closes as endocardial cushions fuse to septum primum.
  4. Step 4 – ostium secundum forms from small area of apoptosis in upper portion of septum primum.
  5. Step 5 – septum secundum forms; this is a thick, muscular septum which forms to the right of the septum primum. This will form the bulk of the interatrial septum.
  6. Step 6 – foramen ovale forms within the septum secundum.
  7. The septum primum becomes the valve of the foramen ovale.
  8. Prenatally, pressure is greater in the right side of the heart than the left. Thus, blood bypasses the right ventricle via the foramen ovale.
  9. Postnatally, pressure is greater in left side of heart, closing the valve of the foramen ovale against the septum secundum; and thus forming the fossa ovalis.
  10. Patent foramen ovale (25% of population) – results when the valve of the foramen ovale does not completely fuse to the septum secundum. Usually asymptomatic. However, any increase in pulmonary pressure (coughing, sneezing, pulmonary hypertension) can cause the foramen ovale to re-open.
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13
Q

partitioning of the atrioventricular orifice: steps leading to communication of primitive atria with left and right ventricles

A

a. Initially, only primitive left ventricle is in contact with atria.
b. Right ventricle is separated from atria by the bulboventricular flange.
c. Bulboventricular flange regresses during 5th week; at the same time the atrioventricular canal enlarges and shifts to the right.
d. These two events provide communication of atria with left and right ventricles.

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14
Q

partitioning of left and right atrioventricular canals

A

a. Endocardial cushions (superior, inferior, left, right) are derived from neural crest.
b. Superior and inferior endocardial cushions project into the atrioventricular canal and fuse, separating the AV canal into right and left orifices.

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15
Q

what are endocardial cushions and atrioventricular valves derived from?

A

neural crest

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16
Q

partitioning of ventricles (IV septum)

A
  1. Muscular portion of septum derived from muscle of ventricle walls.
  2. Membranous septum derived from endocardial cushions.
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17
Q

where do heart valves come from?

A

neural crest

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18
Q

partitioning of conus cordis and truncus arteriosus

A
  1. Conotruncal ridges (2) are derived from neural crest.
  2. Conotruncal ridges undergo 180° of spiraling along wall bulbus cordis.
  3. Conotruncal ridges fuse to form aorticopulmonary septum (spiral septum).
    a. Conus cordis forms conus arteriosus (right ventricle) and aortic vestibule (left ventricle).
    b. Truncus arteriosus forms pulmonary trunk and ascending aorta.
  4. Semilunar valves form from neural crest of conotruncal ridges.
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19
Q

Ventricular septal defects

A
  1. Hole in wall of interventricular septum.
    a. Membranous septal defect (most common)
    b. Muscular septal defect
  2. Severity depends on size of defect; often results in left-to-right blood shunt.
    Most common types of defects.
    leads to overload of pulmonary arteries, underload of systemic arteries
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20
Q

Atrial septal defects (ASDs)

A
  1. Hole in the interatrial septum
  2. Presentation depends on size of defect; often result in left-to-right blood shunt.
  3. Ostium secundum defect
    a. Cause 1: excessive degeneration of septum primum
    b. Cause 2: insufficient proliferation of septum secundum
  4. Ostium primum defect due to endocardial cushion defect (see below, C).
  5. Common Atrium
    a. Complete absence of atrial septum
    b. Almost always associated with other major heart defects
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21
Q

Endocardial cushion defect

A
  1. Cause: underdeveloped endocardial cushions due to insufficient proliferation of neural crest cells.
  2. Results in :
    a. Persistent atrioventricular canal
    b. Ostium primum defect (ASD)
    c. Membranous interventricular septum defect
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22
Q

what is a stenosis?

A

a narrowing of a lumen or other normally open structure

23
Q

complete stenosis

A

atresia (completely blocked)

24
Q

Pulmonary/Aortic valve stenosis

A
  1. The lumen of the pulmonary trunk or aorta are narrowed or completely occluded due to malformation of semilunar valve.
  2. Often present with both patent foramen ovale and ductus arteriosus.
25
Q

Tetralogy of Fallot

A
  1. Cause: unequal division of truncus arteriosus by conotruncal ridges
  2. 4 components
    a. Overriding aorta
    b. Pulmonary stenosis
    c. Ventricle septal defect
    d. Right ventricular hypertrophy
26
Q

Transposition of Great Vessels

A
  1. Cause: conotruncal ridges fail to spiral.
  2. Aorta arises from right ventricle.
  3. Pulmonary trunk arises from left ventricle
  4. Usually occurs with patent ductus arteriosus, patent foramen ovale
27
Q

Persistent Truncus Arteriosus

A
  1. Cause: conotruncal ridges fail to form.
  2. Undivided truncus receives blood from right and left ventricles
  3. Usually occurs with patent ductus arteriosus, patent foramen ovale
28
Q

DiGeorge Syndrome

A

mnemonic device: CATCH-22

  • Chromosome 22 deletion; neural crest cell disorder
  • Cardiac defects (endocardial cushion and conotruncal ridge defects)
  • Abnormal facies
  • Thymic aplasia
  • Cleft palate
  • Hypocalcemia (parathyroid deficiency)
29
Q

Ectopic Cordis

A
  1. Results from failure of ventral body wall to close

2. Heart lies on surface of chest

30
Q

Dextrocardia

A

heart loops in opposite direction, lies in right thorax (a mirror image)

31
Q

vasculogenesis

A
  1. Under the influence of VEGF, mesodermal cells differentiate into blood islands.
  2. Blood islands give rise to hemagioblasts.
  3. The major embryonic arterial and venous systems and arise via vasculogenesis.
32
Q

angiogenesis

A

sprouting and growth of already existing vessels.

33
Q

3 primary vascular systems of embryo/ fetus

A

intraembryonic system, yolk sac (vitelline) system, placental system

34
Q

Intraembryonic system

A
  1. Aortic arch arteries

2. Cardinal system of veins

35
Q

B. Yolk sac (vitelline) system

A
  1. Vitelline artery

2. Vitelline veins

36
Q

C. Placental system

A
  1. Umbilical arteries (2)

2. Umbilical vein (1)

37
Q

Aortic Arch Arteries originate from

A

aortic sac (receives blood from truncus arteriosus)

38
Q

aortic arch arteries drain to

A

dorsal aortae (paired cranially, fused caudally)

39
Q

Derivatives of aortic arch arteries

A

a. Aortic sac will form proximal portion of aortic arch and brachiocephalic artery.
b. First aortic arch – mostly regresses (maxillary artery)
c. Second aortic arch – mostly regresses (stapedial arteries)
d. Third aortic arch – common carotid artery
e. Fourth aortic arch – right artery forms right subclavian artery
left artery forms a portion of aortic arch
f. Fifth aortic arch – regresses
g. Sixth aortic arch – right artery forms the pulmonary artery
left artery forms the pulmonary artery and ductus arteriosus
h. Seventh intersegmental artery – right artery forms distal part of right subclavian
¬ – left artery forms left subclavian a.

40
Q

ductus arteriosus

A

arterial blood shunt allowing blood in pulmonary trunk to bypass lungs and re-enter aorta. After birth, it closes to form ligamentum arteriosum.

41
Q

aortic apparatus and the recurrent laryngeal nerves

A

Recurrent laryngeal nerves originally loop around the distal portion of the sixth aortic arch. On the right, the distal portion of sixth aortic arch regresses, fifth aortic arch also regresses, thus right recurrent laryngeal nerve loops around 4th aortic arch (subclavian artery). On the left, the distal portion of the sixth aortic arch becomes the ductus arteriosus (thus, left recurrent laryngeal nerve loops around arch of aorta near ligamentum arteriosum).

42
Q

Vitelline arteries

A
  1. Supply yolk sac.

2. Derivatives: celiac, superior mesenteric, inferior mesenteric arteries.

43
Q

Umbilical arteries

A
  1. Paired branches of common iliac arteries; supply placenta.
  2. Derivatives: proximal portion remains patent (umbilical artery), distal portion form the medial umbilical ligament.
44
Q

Patent ductus arteriosus (PDA)

A

Ductus arteriosus normally closes after birth to form ligamentum arteriosum.
2. PDA can result in a left-right blood shunt ; resulting in an increased pulmonary blood flow and decreased systemic blood flow.

45
Q

Coarctation of aorta : cause

A

constriction of aorta; unknown mechanism.

46
Q

Preductal coarctation of aorta

A

presents at birth because collateral cirulation does not develop prentally.

47
Q

Postductal coarctation of aorta

A

usually presents in later part of first decade, early adolescence. Does not typically present at birth because collateral circulation is established between internal thoracic and intercostal aa. prenatally.

48
Q

Retroesophageal right subclavian artery

A
  1. The right subclavian artery normally forms from the right 4th aortic arch.
  2. In rare cases, the right 4th aortic arch degenerates; leaving the 7th intersegmental artery and a small portion of the dorsal aorta to form right subclavian artery.
  3. Differential growth shifts the right subclavian to lie distal to origin of the left subclavian a.
  4. Does not usually cause esophageal or tracheal constriction.
  5. If there is esophageal compression this is called dysphagia lusoria (difficulty swallowing due to compression by a vessel).
49
Q

Double aortic arch

A
  1. Right dorsal aorta between original of seventh intersegmental a. and fusion with left dorsal aorta persists.
  2. The vascular ring surrounding trachea and esophagus usually causes constriction.
50
Q

Umbilical veins

A
  1. Right umbilical vein degenerates.
  2. Left umbilical vein remains and carries oxygenated blood from placenta through fetal liver to heart.
  3. The ductus venosus is a venous blood shunt which allows this richly oxygenated blood in the umbilical vein to bypass the liver and directly enter the IVC.
  4. Postnatally, the umbilical vein becomes the ligamentum teres hepatis.
  5. Postnatally, the ductus venosus becomes the ligamentum venosum.
51
Q

what do vitelline veins become?

A

(from yolk sac) will form the hepatic portion of IVC

52
Q

Cardinal veins

A
  1. Anterior cardinal veins drain cephalic portion of embryo.
  2. Posterior cardinal veins drain caudal portion of embryo.
  3. Anterior and posterior merge to form common cardinal vein.
  4. Posterior cardinal veins eventually replaced by:
    a. Supracardinal veins – drain thoracic body wall
    b. Subcardinal veins – drain kidneys and portion of abdominal body wall
    c. Sacrocardinal veins – drain lower limbs
  5. Fate of cardinal vessels :
    a. Anterior cardinal veins – left and right brachiocephalic veins
    b. Right common cardinal - SVC (left cc mostly degenerates)
    c. Supracardinal veins - azygos system of veins
    d. Right subcardinal vein - renal portion of IVC
    e. Right sacrocardinal veins - distal portion of IVC
53
Q

Congenital anomalies of venous system

A

A. Absent inferior vena cava

  1. Right subcardinal vein fails to make connection with the hepatic portion of the inferior vena cava.
  2. Caudal portion of body drains to azygos system of veins.
54
Q

What parts of the heart are derived from neural crest cells?

A

valves

CV (15 decks)

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