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Organ Systems > Vascular pt 6 (embryology) > Flashcards

Vascular pt 6 (embryology) Flashcards

1
Q

When and how (general) does the vascular system begin to develop?

A

During the third week, angiogenic clusters form blood vessels in the yolk sac, cardiogenic area and placenta (mesoderm)

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2
Q

What are hemangioblasts and what do they do?

A
  • Developed from mesoderm cells

- differentiate between mesenchyme and yolk sac cells via FGF; the cells cluster into islands

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3
Q

What are VEGFs?

What do they do?

A
  • Vascular endothelial growth factors secreted from mesodermal cells
  • differentiate hemangioblasts into hematopoietic stem cells *precursor of all blood cells) and endothelial cells (vessel walls)
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4
Q

What does VEGF secretion by mesenchymal cells do?

A

Generates capillaries which consolidate into arteries and veins

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5
Q

What does PDGF do?

A

(platelet derived growth hormone) differentiates mesenchymal cells into SM and pericytes

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6
Q

During gestation, where is the site of blood formation? (three stages)

A
  1. yolk sac
  2. liver and spleen
  3. Bone marrow
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7
Q

What is the initial process of cardiogenic area formation?

A
  • Precardiac mesoderm migrates laterally to heart-forming region
  • Endoderm replaces hypoblast and secretes signaling factors to regulate endochardial cell and myocyte formation
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8
Q

Explain heart tube formation

A
  • Develop from myoblast clusters
  • heart tubes fuse to make a ventral heart tube and a dorsal aorta during folding
  • pericardium formed from intraembryonic coelom
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9
Q

Explain head folding

A

(bending of endocardial tubes)

  • ventral fusion produces heart tube
  • dorsal fusion produces aorta
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10
Q

Explain bulboventricular loop formation

A

Heart tube forms: truncus arteriosus, bulbus cordis, ventricle/atrium, sinus venosus
The bulboventricular loop is formed by the twisting of heart tube

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11
Q

Explain heart beat formation

A
  • Contractions begin when heart tubes fuse (21-23 days)
  • Contractions are peristaltic waves from primitive atria into ventricles (no initial valves)
  • Blood flow begins in 4th week
  • Heart rate accelerates with chamber formation
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12
Q

What is the bulboventricular loop?

A

Blood flows from sinus venous, thru atria, thru ventricles, thru bulbus cordis and to truncus arteriosus

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13
Q

Explain heart chamber partitioning

A
  • endocardial cushions project from anterior and posterior walls and fuse
  • this separates atria from ventricles leaving AV canals where tricuspid and mitral valves develop
  • cushions form interatrial and interventricular septa
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14
Q

What are the primary and secondary septa of atrial partitioning?

A

primary: separates atria, then forms a secondary foramen
secondary: forms and covers secondary foramen

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15
Q

What is the foramen ovale?
What is its purpose prenatally?
What is its purpose postnatally?

A
  • opening in secondary septum
  • prenatally directs blood flow from the right to left atria
  • postnatally, nothing. L. atrial pulmonary pressure keeps it closed and forms the fossa ovalis
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16
Q

What are two types of atrial septal defects?

A
  1. probe patent foramen ovale: primary and secondary septums don’t adhere well; few symptoms
  2. secundum type SD: excessive resorption of primary septum or inadequate development of secondary; leads to patent foramen ovale (increases work of heart by permitting blood flow from L to R or R to L [cyanosis])
17
Q

Explain the formation of the aorta and pulmonary trunk

A

Spiral aortico-pulmonary septum divides bulbis cordis/truncus arteriosus into aorta and pulmonary trunk; semilunar valves form at the TA and BC junctions

18
Q

How is the ventricular septum formed?

A

Bulbar ridge, endocardial cushions and ventricular wall fuse, closing off interventricular foramen and forming the septum

19
Q

What are the two portions of the ventricular septum?

A
  1. Muscular portion: develops from ventricular wall; separates AV valves
  2. Membranous portion: derived from endocardial cushions and bulbar ridge
20
Q

What is VSD?

A

(Ventricular septal defect)

  • most common defect of heart
  • 25% of these defects occur in the membranous portion
  • allows oxygenated blood to flow from L to R ventricle (can lead to cyanosis)
  • small ones close on own, large ones need surgery
21
Q

What are some defects in BC/TA division?

A
  1. persistant truncus arteriosus (no septum)
  2. transposition of aorta and pulmonary trunk (no spiral)
  3. unequal division of BC/TA (override)
  4. pulmonary or aortic stenosis
22
Q

What is the tetralogy of fallot?

A
  • condition due to unequal dividion of BC/TA

- leads to: VSD, pulmonary stenosis, R. ventricular hypertrophy, overriding aorta

23
Q

What is a neural crest malformation?

A

When neural crest cells migrate from the ectoderm and interact with mesenchyme to form the face and heart

24
Q

What is a heart malformation?

A

Endocardial cushion is malformed due to abnormal migration, proliferation and differentiation of neural crest cells

25
Q

Where does the sinus venous receive blood from? (3)

A
  1. cardinal veins (drain body)
  2. vitelline (drain yolk sac and become portal veins)
  3. umbilical (bring blood from placenta)
26
Q

What are aortic arches?

A

Branches from truncus arterioles that form the major vessels leading to the heart

27
Q

What does the asymmetry of the arches lead to?

A
  • aorta on the left
  • left recurrent laryngeal nerve under aorta
  • right recurrent laryngeal nerve under right subclavian artery
28
Q

What is the ductus arterioles?

A
  • Persistant branch of aortic arch
  • connects pulmonary trunk to aorta
  • permits blood flow from pulmonary trunk into aorta (bypasses lungs)
29
Q

What does the trophoblast differentiate into?

A
  • syncytiotrophoblast: jelly mass that expands into endometrium
  • cytotrophoblast: forms chorionic villi containing fetal blood vessels (b/w intervillous spaces)
30
Q

What is the fetal-maternal placental barrier?
What normally crosses the barrier?
What is potentially harmful if crossed the barrier?

A

Barrier formed by layers of cytotrophoblasts, syncytiotrophoblasts and mesoderm (around fetal vessels)

  • normal transfer includes metabolic substances
  • viruses, alcohol, dilantin, valproic acid, retinoic acid, androgens, antibiotics, etc.
31
Q

What is the fate of vitelline/umbilical veins?

A
  • liver tissue develops around vitelline veins
  • umbilical and vitelline veins converge to form hepatic sinusoids
  • ductus venosus forms internal bypass thru liver
32
Q

What are the three shunts of prenatal circulation?

A
  1. Ductus venosus: diverts blood around liver
  2. Foramen ovale: shunts blood from R to L atrium
  3. Ductus arteriosus: shunts blood from pulmonary trunk to aorta, bypassing lungs
33
Q

What are the three shunts of postnatal circulation?

A
  1. Ligamentum venosum: in liver
  2. Fossa ovalis: in atrial septum
  3. Ligamentum arteriosum: b/w aorta and pulmonary trunk
34
Q

How is oxygen distributed in prenatal circulation?

A
  1. ductus arteriosus shunts deox. blood into aorta, reducing ox. blood in lower limb
  2. blood in umbilical veins and vena cava are separate when entering R. atrium
  3. More ox. blood enters L. atrium, more deox. blood enters R. ventricle and pulmonary trunk

Organ Systems (20 decks)

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