L29: Development Of Great Vessels And Circulatory Changes At Birth Flashcards
Vasculogenesis vs Angiogenesis
Vasculogenesis: De novo formation of blood vessel from angioblasts / Haemangioblast (from mesodermal cells)
Angiogenesis: Growth of new capillaries from pre-existing blood vessels
Development of pharyngeal arches and aortic arches
Pharyngeal arch
- 6 pairs of pharyngeal arches —> 5th arch rudimentary (not visible on surface)
- each pharyngeal arch has a core mesenchyme —> specific tissues in head and neck
- each arch has own nerve and artery
Aortic arch
- within each pharyngeal arch —> own aortic arch (embedded in mesenchyme of pharyngeal arches) —> terminate in left and right dorsal aorta
- Blood flow: sinus venosus —> atria —> ventricles —> truncus arteriosus —> aortic sac —> aortic arch —> dorsal aorta
- aortic sac contribute a branch as new aortic arches form —> appear in cranial-to-caudal sequence
- 5th aortic arch eventually degenerate
Differentiation of aortic arches
- 1st aortic arch degenerate —> maxillary artery
- 2nd aortic arch degenerate —> hyoid, stapedial arteries
- 3rd aortic arch: (blood to head)
Left: Common carotid artery, proximal External and Internal carotid artery
Right: Common carotid artery, proximal External and Internal carotid artery - 4th aortic arch: (blood to head and arms)
Left: Aortic arch between Left Common carotid artery and Left Subclavian artery
Right: proximal Right Subclavian artery - 6th aortic arch: primitive pulmonary artery present (5 week) (blood to lung bud)
Left: Left pulmonary artery, Ductus arteriosus (allow blood to bypass lung)
Right: Right pulmonary artery
Connections of aortic arches with dorsal aorta
3rd aortic arch:
Left: proximal internal carotid artery
Right: proximal internal carotid artery
4th aortic arch:
Left: distal aortic arch
Right: proximal subclavian artery
6th aortic arch:
Only Left: ductus arteriosus
Abnormal origin of right subclavian artery
- obliterated 4th aortic arch and proximal right dorsal aorta
- formed by 7th intersegmental artery and distal right dorsal aorta
- settle below left subclavian artery and cross midline behind oesophagus to the right arm
—> compress trachea and oesophagus but not too severe
Double aortic arch:
If distal right dorsal aorta persists along with normal 4th aortic arch + proximal dorsal aorta
—> formation of vascular ring surround trachea and oesophagus —> difficulty in breathing and swallowing
Vitelline arteries
- branch of dorsal aorta
- Differentiate into gut vessels:
Foregut: Coeliac artery
Midgut: Superior mesenteric artery
Hindgut: Inferior mesenteric artery (from umbilical artery)
Umbilical artery
- branch of dorsal aorta
- carry deoxygenated blood to placenta for oxygenation
- at birth:
Proximal portion of umbilical arteries —> Superior vesical arteries
Distal portion of umbilical arteries —> Medial umbilical ligaments
3 Venous system
- Vitelline veins (中間): carry blood from Yolk sac to sinus venosus
- Umbilical veins (兩者之間): originate from Chorionic villi —> carry oxygenated blood to embryo
- Cardinal veins (兩側): draining body of embryo
Development of Cardinal veins
L, R Anterior cardinal veins: drain Cephalic part of embryo
L, R Posterior cardinal vein: drain rest of embryo
Anterior and Posterior cardinal vein join —> Common cardinal vein —> enter Sinus venosus / Sinus horn
Development of sinus venosus
- Originally, receives blood from Left and Right Sinus horn —> Primitive atrium
- Left-to-right shunt of blood —> Right sinus horn ↑ in size —> obliteration of:
1. Right Umbilical vein (右入)
2. Right Posterior Cardinal vein (右側)
3. Left Vitelline vein (左中)
4. Left Anterior/Posterior Cardinal vein —> Left Common Cardinal vein (左側)
(仲有: Left Umbilical vein, Right Vitelline vein, Right Anterior Cardinal vein)
when Left Common Cardinal vein is obliterated —> all remains in Left Sinus Horn:
- Oblique vein of L atrium
- Coronary sinus
Right atrium:
Sinuatrial orifice (opening to R sinus horn) guarded by left + right venous valves:
—> R sinus horn incorporated into R atrium —> Sinus Venarum
—> superior portion of venous valves disappear
—> inferior portion of venous valves —> valves of IVC + valves of coronary sinus
—> Crista terminalis divide trabeculated right atrium and Sinus Venarum
Left atrium:
Single pulmonary vein develops as an outgrowth of posterior left atrial wall
—> connecting with veins of lung buds
—> four pulmonary veins
Development of Vitelline veins
Arise from Yolk sac capillary plexus (run in each side of duodenum)
—> development of liver cord
—> proximal part of Vitelline and Umbilical Vein broken into vascular network
—> Hepatic sinusoids
—> drain into Right and Left Hepatocardiac channels —> sinus venosus
2nd month:
Left Sinus horn + Left Hepatocardiac channel —> obliterated
—> Left Umbilical vein
—> Right Hepatocardiac channels
—> Hepatic portion of IVC (Common Hepatic vein)
—> sinus venosus
3rd month:
- Vitelline vein network around duodenum —> Portal vein (single vessel)
- Right Vitelline vein —> superior mesenteric vein (drains small intestine)
(Blood flow: superior mesenteric vein —> portal vein)
- Left Proximal Umbilical veins + Right Umbilical vein —> obliterated
—> Left Umbilical vein carry blood from placenta to liver through Ductus venosus
Development of IVC, SVC and azygous vein
Anastomosis between (R/L) Anterior Cardinal veins —> Left Brachiocephalic vein Terminal Left Posterior Cardinal vein —> Left Superior Intercostal vein
Right Common Cardinal vein —> SVC
Proximal Right Anterior Cardinal vein —> Internal Jugular vein
Anastomosis between subcardinal veins —> Left Renal Vein
Right subcardinal vein —> Renal segment of IVC
Anastomosis between Sacrocardinal veins —> Left Common Iliac vein
Intercostal vein empty into right supracardinal vein + posterior cardinal vein —> Azygous vein
Summary of venous system development
- Left Vitelline vein: regress
- Right Vitelline vein: Terminal IVC (hepatic portal system)
- Left Umbilical vein: anastomosis with Ductus Venosus
- Right Umbilical vein: regress
- Left Anterior Cardinal vein: oblique vein of L atrium, Internal Jugular vein
- Right Anterior Cardinal vein: Right Brachiocephalic vein, Internal Jugular vein, SVC
- Medial Anastomosis: Left Brachiocephalic vein
- Left Posterior Cardinal vein (with anastomosis): Left Common Iliac vein, sacral IVC
- Right Posterior Cardinal vein (with anastomosis): Right Common Iliac vein, sacral IVC
- Left Subcardinal vein (with anastomosis): Left Renal and Gonadal vein
- Right Subcardinal vein: Right Renal and Gonadal vein, renal IVC
- Left Supracardinal vein: Hemiazgos vein, Intercostal vein
- Right Supracardinal vein: Azygos vein, Intercostal vein, 3rd segment IVC
Venous system defects
Double IVC: failure of Left Sacrocardinal vein to lose connection with Left Subcardinal vein
Absence of IVC: Right Subcardinal vein fail to connect to liver and shunts blood directly to Right Supracardinal vein (eventually become Azygos vein)
Left SVC: Left Anterior Cardinal vein persistence + obliteration of Common Cardinal vein + Proximal part of Anterior Cardinal vein on the right —> blood from right is channeled to left by Brachiocephalic vein —> Left SVC drains into R atrium via coronary sinus
Double SVC: Left Anterior Cardinal vein persistence + failure of Left Brachiocephalic vein to form —> Left SVC drains into R atrium via coronary sinus
Fetal circulation before birth, mixing of oxygenated blood with deoxygenated blood in:
- Portal system
- IVC
- Heads and limbs
- Lungs
- Ductus arteriosus
