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Embryo - Heart Development Flashcards

1
Q

What layer does the Heart develop from?

A

Basics:

  • splanchnic layer of lateral mesoderm

Other Facts:

  • Earliest organ to develop (~day 18)
  • Heart beats (~day 21-22)
    • detected by sonography (~week5)
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2
Q

What is cardiogenic mesoderm and what does it split into?

A

Basics:

  • horseshoe shaped region of mesoderm
    • extending from anterior of embryo –> both sides of foregut

Approx 18 days:

  • Cardiogenic Mesoderm = cranial to precordal plate (mouth)

Pericardial coelom splits it into:

  1. somatic part (dorsal)
  2. splanchnic part (ventral)
    • primordial heart tubes dev. from this layer

Pericardial coelom eventually is divided by folds to form:

  • ​pericardial space (heart)
  • pleural space (lungs)
  • peritoneal space (abdomenal structures)
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3
Q

What is the importance of flexion and folding?

A

Basics:

  • Folding & flexion –> migration of developing heart into normal anatomical position
    • ventral to foregut
    • proximal to diaphragm

Longitudinal Folding:

  • Brings everything caudal into correct place
    • ​Heart tube = now caudal to head & ventral to foregut
    • Septum transversum = caudal to heart
      • future diaphragm
  • ​Secondary Yolk sac —> forms gut/GI structure​

Lateral folding:

  • fuses heart tubes together
  • parietal pericardium
    • forms from somatic layer of mesoderm
  • visceral pericardium
    • forms from splanchnic layer of mesoderm
    • phrenic nerve found in folds

Results:

  • Pleural cavitites lie along the sides of the foregut
    • airways develop from foregut
  • Peritoneal cavities lie dorsally at sides of gut
  • Pericardial cavity moves to position vental to foregut
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4
Q

What are the 5 subdivisions of the Single Heart Tube in early embryonic development?

A

Sinus venosus –> Primordial Atrium –> Primodial Ventricle –> Bulbus Cordis –> Truncus Arteriosus

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5
Q

Embryological fates of the heart tube components?

A
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6
Q

Truncus arteriosus gives rise to?

A

Ascending aorta & pulmonary trunk

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7
Q

Bulbus cordis gives rise to?

A

Smooth parts (outflow tract) of left and right ventricles

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8
Q

Endocardial cushion gives rise to?

A
  • Atrial septum
  • Membranous interventricular septum
  • AV & semilunar valves
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9
Q

Primitive atrium gives rise to?

A

Trabeculated part of left & right atria

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10
Q

Primitive ventricle gives rise to?

A

Trabeculated part of left & right ventricles

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11
Q

Primative pulmonary vein gives rise to?

A

Smooth part of left atrium

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12
Q

Left horn of sinus venosus gives rise to?

A

Coronary Sinus

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13
Q

Right horn of sinus venosus gives rise to?

A

Smooth part of the right atrium (sinus venarum)

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14
Q

Right common cardinal vein and Right anterior cardinal vein give rise to?

A

Superior vena cava (SVC)

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15
Q

What is Cardiac Looping ?

What defect can arise?

A

Cardiac Looping:

  • Primary heart tube loops to establish left-right polarity/heart laterality
    • begins at week 4 of gestation
  • D-Loop (normal)
    • apex = left

When things go wrong:

  • Dextrocardia (L-loop)
    • ​apex = right​​​
  • Seen in Kartagener syndrome
    • primary ciliary dyskinesia
  • Complete situs inversus
    • all organs = reversed
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16
Q

What is involved in Left-Right Partitioning?

A

Basics:

  • ALL of the heart tube MUST BE PARTITIONED:

Partitioning = accomplished by the growth/dev of:

  1. Endocardial cushions (AV cushions)
    • neural crest cells = important for this formation
  2. Interatrial septum
  3. Interventricular sepum
    • muscular & membranous parts
  4. Spiral (aortico-pulmonary) septum
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17
Q

Separation of the Atrial chambers involves what 5 steps?

A

Atrial Chambers in Utero:

  1. Septum primum grows toward endocardial cushions
    • narrows foramen primum
  2. Foramen secundum forms in septum primum
    • foramen primum disappears
  3. Septum secundum develops as f_oramen secundum_ maintains right-to-left shunt
  4. Septum secundum expands and covers most of foramen secundum
    • opening btw septum secundum + septum primum = foramen ovale
  5. Remaining portion of septum primum forms valve of foramen ovale

After Birth:

  • Septum secundum & septum primum fuse to form the atrial septum
  • Forman ovale usually closes due to ↑ L.A. pressue
    • fossa ovale = reminant that can be seen in R.A.
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18
Q

What are the 3 Steps for the Separation of Ventricle Chambers?

A
  1. Muscular interventricular septum forms
    • opening = interventricular foramen
  2. Aorticopulmonary septum rotates & fuses w/ muscular ventricular septum
    • forms membranous interventricular septum
    • closes interventricular foramen
  3. Growth of endocardial cushions separates atria from ventricles
    • contributes to both atrial septation & membranous portion of the interventricular septum
19
Q

Explain outflow tract formation.

What happens when things go wrong?

A

Outflow tract formation:

  • Neural crest & endocardial cell migrations
    • truncal & bulbar ridges
      • spiral & fuse to form aorticopulmonary septum
    • ascending aorta & pulmonary trunk

When things go wrong:

  • Conotruncal abnormalities assoc. w/ failure of neural crest cells to migrate:
    • Transposition of great vessels
    • Tetralogy of Fallot
    • Persistent truncus arteriosus
20
Q

Valve Development

A

Aortic/Pulmonary:

  • derived from endocardial cushions of outflow tract

Mitral/Tricuspid:

  • derived from fused endocardial cushions of the AV canal

When things go wrong…

  • Valvular anomalies:
    • Stenotic
    • Regurgitant
    • Atretic
      • tricuspid atresia
    • Displaced
      • Abstein anomaly
21
Q

Fetal Circulation

A

Fetal Circulation:

  • Placental circulation
    • source of oxygentated blood
  • Right-to-left shunts
    • Foramen ovale
      • connects R.A. + L.A.
    • Ductus arteriosus
      • connects R.V. –> pulmonary artery + descending aorta
  • Little pulmonary blood flow
    • Non-functional lungs

Note:

  • Limbs & GI = less oxygenated blood
22
Q

What are the 3 important Shunts in Fetal Circulation?

A

Basics:

  • Blood in umblical vein:
    • Po2 = 30mmHg
    • ~ 80% saturated w/ O2
  • ​Umbilical arteries have low O2 saturation

3 Important Shunts

  • Ductus Venosus
    • Blood entering fetus via umbilical vein –> IVC
      • Bypasses hepatic circulation
  • Foramen Ovale
    • Oxygenated blood reaches heart via IVC
    • Blood directed from R.A. –> L.A. –> L.V. –> Aorta
    • Most blood pumped thru Aorta
  • Ductus Arteriosus
    • De-oxygenated blood from SVC
      • R.A. –> R.V. –> main pul. artery –> Ductus arterious –> Decending Aorta
    • Shunt is due to HIGH fetal pul. artery resistance
      • cause by partly low O2 tension

After Birth:

  • infant takes breath = ↓ Resistance in pul vasculature
    • ↑ L.A. pressue
  • Foramen ovale closes –> Fossa ovalis
  • ↑ O2 (from respiration) + ↓ Prostaglandins (from placental separation) = closure of Ductus Arteriosus
    • Indomethacin = helps close PDA
    • Prostaglandins E1, E2 = kEEp PDA open
    • Reminant = ​Ligamentum arteriosum
23
Q

What is the Fate of aortic arches?

A
  • ​1st arch
    • maxillary artery
  • 2nd arch
    • stapedial a.
      • tympanic branch of internal carotid a.
  • 3rd arch
    • common carotid
    • proximal part of internal carotid a.
  • 4th arch
    • arch of aorta (left)
      • left subclavian a.
    • right subclavian
      • right 7th cervical intersegmental branch
  • 5th arch
    • completely disappears
  • 6th arch
    • right pulm. a.
    • left pulm. a
      • ductus arterious
24
Q

What are the Disappearing arteries?

A

Partially disappearing:

  • 1st arch
  • 2nd arch
  • Right 6th arch
  • Righ Dorsal Aorta

Totally disappearing:

  • 5th arch
25
Q

What aortic branches do the Recurrent laryngeal nerves wrap around?

A

Left Recurrent laryngeal nerve

  • wraps around 6th aortic arch
    • lateral to ductus arteriosus

Right Recurrent laryngeal nerve

  • wraps around 4th arch - right subclavian a.
    • 5th & 6th arches disappear
26
Q

What are the 3 Major Anomalies of the arch system?

A
  1. Double aortic arch
  2. Patent Ductus Arteriosis
  3. Coarctation of Aorta
27
Q

What is a Double aortic arch?

A

Basics:

  • Persistence of RIGHT dorsal aorta
    • Caudal to 7th cervical intersegmental a.
  • Forms ring around trachea & esophagus

Results:

  • Encloses esophagus & trachea
  • Causes:
    • dyspnea (trouble breathing)
    • dysphagia (trouble eating)

Note:

  • 1 of 3 anomalies of the arch system
28
Q

What is a Patent Ductus Arteriosus?

A

Basics:

  • Ductus arteriosus should close after 72 hrs (3 days)
  • Becomes ligamentum arteriosum
  • _Patent Ductus arteriosus = FAILURE TO CLOS_E

Natural causes of closure:

  • Increase in partial pressure of O2 after birth
  • Drop in prostaglandin levels after birth

Treatment of Patent Ductus arteriosus:

  • Give high concentration of O2 to baby
  • Give anti-prostaglandins to baby

Fun Facts:

  • More common in females
  • Associated with:
    1. rubella in early pregnancy
    2. Down Syndrome (trisomy 21)
    3. coarctation of aorta
    4. transposition of great vessels
  • Failure of TGF-B induction after birth

Note:

  • 2 of 3 anomalies of arches
29
Q

What is Coarctation of aorta?

A

Basics:

  • abnormal partial involution (constriction) of dorsal aorta

3 Types:

  1. Postductal
    • distal to ductus arteriosus
    • collateral circulation => less severe effects
      • subclavian a. –> internal thoracic a –> superior epigastric a. –> inferior epigastric a. (branch of external iliac a.);
      • will NOT affect tissue O2 much b/c of collateral circulation
    • Upper limb = HTN & Heart Failure
    • Lower limb = diminished femoral pulse
  2. Preductal
    • ​proximal to ductus arteriosus
  3. Extensive

Note:

  • May be associated w. Turner Syndrome
30
Q

What are the 2 major categories of Congenital Heart Defects?

A

Acynotic

  • Volume load
    • Left –> Right shunt
      1. ASD
      2. VSD
      3. AV Canal
      4. Patent ductus arteriosus
  • Pressure load
    • Obstr. Ventricle Outflow
      1. Pulmonary Valve stenosis
      2. Aortic Valve stenosis
      3. Coarctation of aorta

Cyanotic

  • ↑ Pulm. flow
    • Transposition of Great Vessels
    • Single Ventricle
    • Trucus Arteriousus
  • ↓ Pulm. flow
    • Tetralogy of Fallot
    • Pulm atresia
    • Tricuspid atresia
31
Q

What are the 4 Causes of Congenital Heart Defects?

A

Causes of CHD:

  1. 80% = UNKNOWN
  2. Infection
    • Rubella
  3. Chromosomal
    • Turners syndrome = Coarctation of aorta
    • Downs/Trisomy 21 = ASD/VSD/PDA
  4. Poorly defined familial susceptibility
32
Q

What are the 5 Clinical effects of CHD?

A
  1. Failure to thrive
  2. Cyanosis
    • Right –> Left shunt
  3. Cardiac Failure
  4. Pulm. HTN
  5. Infective endocarditis
33
Q

How does the Single Heart Tube grow?

A

Future Right Atrium

  • rough part = primordial atrium
  • smooth part =
    • right horn of sinus venosus = sinus venarum
    • left horn of sinus venosus = coronary sinus

Future Left Atrium

  • rough part = primordial atrium
  • smooth part = pulmonary arteries

Future Right Ventricle

  • trabeculated part = primordial ventricle
  • smooth part = bulbus cordis = conus arteriosus

Future Left Ventricle

  • trabeculated part = primordial ventricle
  • smooth part = bulbus cordis = aortic vestibule

Future Aorta & Pulm artery

  • from truncus arteriosus
34
Q

What are the major features of Right Atrium?

A
  • Pectinate muscle
    • trabiculated part
      • from primordial atrium
  • Crista terminalis
    • junction of smooth & rough parts
  • Fossa ovalis
    • closed shunt; fetal reminant
  • Tricuspid valve
    • leads to right ventricle
  • Coronary sinus
    • from left horn of sinus venosus
    • venous return from heart veins
35
Q

What are the major components of the Left Atrium & Left Ventricle?

A

Left Atrium

  • Mostly smooth due to absorption of pulm. veins
    • 4 pulmonary veins = bring O2 rich blood
  • Left auricle
    • rough part
    • reminant of primordial atrium

Left Ventricle

  • Aortic vestibule
    • left ventricle outflow tract (LVOT)
    • form bulbus cordis
    • entry into aorta
  • Aortic (semilunar) valve
36
Q

What are the major components of the Right Ventricle?

A
  • Conus arteriosus
    • Right ventricle outflow tract (RVOT)
    • entry into pulm. artery (pulm valve)
  • Moderator band
    • septomarginal trabeculum
    • anchors papillaries to interventricular septum
  • Tendinous cords
    • hold tricusptid valve open
    • attached to papillary muscles
  • Trabeculae carnae
    • rought part
    • from primordial ventricle
37
Q

What are the 2 important features of Fetal Circulation?

A
  1. Lung = non functional
    • collapsed in fetus
    • high pulmonary resistance
  2. Nutrients & O2 rich blood from maternal circulation
    • Placenta –> Umbilical vein –> Ductus Venosus –> IVC –> R.A. –> Foramen Ovale –> L.A. –> L.V. –> Ascending Aorta –.> Body (Brain)
    • Blood from SVC –> R.A. –> R.V. –> Pulm Artery –> Ductus arterious –> Descending Aorta (mixed venous blood to lower limb)
38
Q

What are the 3 Important Changes from Fetal to Adult Circulation?

A
  1. Closure of foramen ovale
    • breathing = lungs expand = resistance in pulmonary system DECREASES
      • right pressure in heart DECREASES
      • left pressure in heart INCREASES
    • change in pressure = closes formaen ovale
      • becomes Fossa Ovalis
  2. Closure of ductus arteriosus
    • becomes ligamentum arteriosum
  3. Closure of ductus venosus
    • becomes ligamentum venosum
39
Q

Explain Ventricular Partitioning

A

Basics:

  • Interventricular septum separates RV & LV by week 7
  • aorta & pulm trunk = formed by partitioning truncus arteriosus

Structures:

  • Ventricular septum has 2 parts:
    • Muscular part - dev. from primordial interventricular septum
    • Membranous part - dev. from endocardial cushions & bulbar ridges
  • Partition of aorta & pulm trunk:
    • continuation of bulbar ridges, truncal ridges, and endocardial cushions
    • forms aorticopulmonary/spiral septum

Both:

  • have rough (trabeculated) part dev. from primordial ventricle
40
Q

What are Ventricular Septal Defects (VSD)?

A

Basics:

  • Failure of tissue from endocardial cushions to fuse w/ primordial IV setum & bulbar ridges
  • Left –> Right Shunt
  • Acyanotic

Most Common:

  • Membranous type of VSD
    • ~25% of all CHD

Note:

  • Can have associated AV valve (mitral) abnormality
41
Q

What are the 4 Abnormal Divisions of Truncus Arteriosus?

A

Basics:

  • Caused by faulty migration of NEURAL CREST cells

4 Defects:

  1. Tetralogy of Fallot
  2. Transposition of Great Vessels
  3. Persistent Truncus
  4. Aorticopulmonary septal defects
42
Q

What is Tetralogy of Fallot?

A

Basics:

  • truncus arteriousus divides unevenly
    • larger aorta, smaller pulm. artery
  • Right –> Left shunt
    • Cyanosis!

Cause:

  • Faulty migration of neural crest cells
  • Failed fusion of endocardial cushions, truncal & bulbar ridges

Results:

  1. VSD
    • membranous VSD
  2. Pulmonary stenosis
    • uneven separation leads to small pulm. artery
  3. Right ventricular hypertrophy
    • increased workload resulting from pulm. stenosis
  4. Overridinig aorta
    • Aorta “rides over the IV septum; receives blood from both ventricles
43
Q

What is the Transposition of the Great Vessels?

A

Basics:

  • Switching of aorta & pulmonary trunk

Cause:

  • Faulty migration of neural crest cells –> absence of spiral twist in aortico-pulmonary septum

Result:

  • Immediately lethal unless combined w/ other defect - PDA, ASD, VSD
44
Q

What is Persistent Truncus Arteriosus?

A

Basics:

  • No formation of aortico-pulmonary septum

Cause:

  • Failure of neural crest cells to migrate

Result:

  • Associated w/ VSD
  • Cyanotic

HSF Block 2 (24 decks)

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