Flashcards in L29 – Development of the great vessels and circulatory changes at birth Deck (96):
The de novo formation of blood vessels from angioblasts (haemangioblasts)
growth of new capillaries from pre-existing blood vessels(i.e. dorsal aorta, cardinal vein)
Three mechanisms of Angiogenesis?
1. Sprouting (= branching)
2. Intussusception (= splitting: grow inward into smaller capillaries)
3. Bridging (grow inward but more evenly distributed)
Which mechanism of angiogenesis gives increasing number of blood vessels?
6 pairs of pharyngeal arches develop. Describe innervation of arches. Describe core of these arches and their function.
Each pharyngeal arch receives its own nerve, artery
Each arch has core of
mesenchyme tissue: give rise to specific tissues in head and neck
How do aortic arches arise and where do they terminate?
Arise from aortic sac (distal truncus arteriosus)
Aortic arches are embedded in mesenchyme core of pharyngeal arches
Terminate in L/R dorsal aortae > converge to outflow tract
How do pharyngeal arches and aortic arches appear?
Cranial- caudal sequence
Aortic sac contributes a branch to each new pharyngeal arch as it
Which pharyngeal arch forms incompletely and degenerates?
What happens to the first and second aortic arches by 5th week?
1st and 2nd aortic arches degenerate
1st arch remnant= Maxillary artery
2nd arch remnant= hyoid and stapedial arteries
What happens to 3rd, 4th and 6th aortic arches by week 5?
3rd = Large
4th, 6th = Still forming
Which arch give rise to primitive pulmonary artery?
developing 6th aortic arch
Is the differentiation of aortic arches simultaneous?
Graded formation: remodelling from 1st arch to 6th
What areas do the aortic arches supply blood to?
3rd = head
4th = head, arms
6th= lung bud
Describe further development of 3rd aortic arch.
Left and Right:
Form L/R Common carotid artery
Proximal portion of internal carotid artery
Describe further development of 4th aortic arch.
Left: Aortic arch (portion between left subclavian and left common carotid artery)
Distal aortic arch connect to L dorsal aorta
Right: Proximal portion of right subclavian
artery > connect to R
Describe further development of 6th aortic arch.
Left: Left pulmonary artery + Ductus arteriosus
Right: Right pulmonary artery
What is role of ductus arteriosus?
Transient, allow blood to bypass lungs to descending aorta
Which caudal portion of dorsal aorta is obliterated?
Right dorsal aorta
What do vessels in right cranial dorsal aorta lead to?
7th intersegmental artery
What duct formed by 3rd aortic arch is obliterated?
Name the vessel that connect 3rd aortic arch with dorsal aorta?
Proximal internal carotid artery on both sides
Name the vessel that connect 4th aortic arch with dorsal aorta?
Proximal subclavian artery on right
Distal aortic arch on left
Name the vessel that connect 6th aortic arch with dorsal aorta?
Only left dorsal aorta through ductus arteriosus
Which vessels are wrongly obliterated/ wrongly persist in Abnormal origin of right subclavian artery?
Wrongly obliterated: Right 4th aortic arch and right proximal dorsal aorta
Wrongly persist: Right distal dorsal aorta
Right subclavian artery wrongly formed by right distal dorsal aorta and 7th intersegmental artery
Consequence of abnormal origin of right subclavian artery?
Abnormal right subclavian artery settle below left subclavian artery
Cross midline behind esophagus to reach right arm
Neither esophagus or trachea compressed severely
What causes double aortic arch to form?
Wrongly persist: right distal dorsal aorta
vascular ring surrounds,
trachea and esophagus
> difficulties in
Dorsal aorta branches throughout the embryo. Name A/V for placenta circulation, Vitelline circulation.
Left umbilical vein
Vitelline circulation :
Vitelline arteries (branch of dorsal aorta) differentiates into what vessels of the gut?
Coelian arteries in foregut
Superior mesenteric arteries in mingut
What vessel forms artery for hindgut?
Umbilical arteries > inferior mesenteric arteries
Role of umbilical arteries?
Originate from chorionic villi, Convey deoxygenated blood to placenta for oxygenation
Fate of umbilical arteries at birth?
Proximal portion = superior vesical arteries
Distal portion = medial umbilical ligaments
Role of cardinal veins?
Draining body of embryo proper
Role of vitelline veins?
Carrying blood from yolk sac to sinus venosus
What are the six cardinal veins? What do cardinal veins originate from?
Left and Right Anterior, Common, Posterior cardinal veins
Arise from Left or Right horns of Sinus venosus
What cardinal veins drains what part of embryo?
Anterior cardinal vein> drain cephalic part
Posterior cardinal vein > drain rest of embryo
How do cardinal veins join?
Anterior and Posterior cardinal veins join at common cardinal veins > enter sinus venosus
Route of blood in sinus venosus? receive and opens into what?
Receives blood from right, left sinus horn
Opens into primitive
Effects of asymmetrical Left to right shunt of blood in primitive heart?
Right sinus horn increases in size
Obliteration of left vitelline vein and left posterior + anterior cardinal veins, right umbilical vein, right posterior common
What vessels are NOT obliterated in the development of sinus venosus before day 50?
left umbilical vein, right anterior + common cardinal vein
What vessel obliterated from day 50-56? What remnant of left sinus horn?
Left common cardinal vein obliterates
remains of left sinus horn = oblique vein of left atrium,
What happens to the initial orifice of pulmonary vein?
becomes 4 orifices of pulmonary veins
Fate of right anterior cardinal vein?
right brachiocephalic vein
Fate of right posterior cardinal vein?
inferior vena cava
Fate of right anterior cardinal vein?
Superior Vena Cava
What occurs to form sinus venarum?
Right sinus horn is gradually incorporated/ inserted into right atrium to form sinus venarum (smooth-walled)
What is the sinuatrial orifice originally flanked by?
Initially flanked by right, left venous valves
What happens to the valves of sinuatrial orifice in development of sinus venosus?
Superior portion of valves disappear
Inferior portion develops into:
Valve of inferior vena cava
(drains into RA)
Valve of coronary sinus (drains into RA)
What forms to divide the original trabeculated primitive right atrium and the incorporated right sinus horn - sinus venarum?
Crista terminalis forms dividing line between:
Original trabeculated part of right atrium
What initially develops to form single embryonic pulmonary vein? Fate of this single vein?
Posterior left atrial wall grows out = single embryonic pulmonary vein
later: 4 pulmonary veins enter LA
Where do vitelline veins arise from?
Arise from capillary plexus of yolk sac
Tract of vitelline veins?
Carry blood from yolk sac to sinus venosus, passing liver
Run in each side of duodenum and forms plexus around it > develops into a single vessel (portal vein)
What forms hepatic sinosoids?
With development of liver cord (by Week 5): proximal part of vitelline, umbilical veins break into numerous vascular network > form
How are hepatic sinusoids drained?
drain into sinus venosus through right, left hepatocardiac channels to vena cava
Explain Selective obliteration to maintain flow back to right atrium by forming common hepatic vein.(Star with left sinus horn obliteration...)
Left sinus horn and hepatocardiac channel obliterated > blood from left umbilical vein enters sinus venosus through right hepatocardiac channel > right vitelline forms common hepatic vein (hepatic portion of inferior VC)
What is superior mesenteric vein derived from? How?
Right vitelline vein
Left vitelline vein degenerate, leaving enlarging R. vitelline > portal vein branching into superior mesentery and splenic veins
What portions of umbilical veins are obliterated? What remains and enlarges?
Proximal part of both umbilical veins
Remainder of right umbilical vein
Left umbilical vein remains and enlarges
How does left umbilical vein carry blood from placenta to heart, bypassing liver?
via DUCTUS VENOSUS
ligamentum venosum at birth
Anastomosis of what veins form left brachiocephalic vein?
Between anterior cardinal veins
How is the left superior intercostal vein formed?
Terminal portion of left posterior cardinal vein entering left brachiocephalic vein retained as left superior intercostal vein
What forms superior vena cava?
Right common cardinal vein +
proximal portion of right anterior cardinal vein
What does the distal portion of right anterior cardinal vein form?
Right internal jugular vein
What forms the azygous vein?
Right supracardinal vein + a portion of posterior cardinal vein
What forms the left renal vein?
Anastomosis between subcardinal veins
What forms the hemiazygous vein?
Supracardinal vein + left common cardinal vein
What does the right subcardinal vein develop into?
develops into renal segment of inferior vena cava
What is the fate of left subcardinal vein?
Distal: becomes left gonadal vein
What forms left common iliac vein?
Anastomosis between sacrocardinal veins
What does Intercostal vein empty into ?
right supracardinal vein
What vein becomes hepatic segment of inferior VC?
Right sacrocardinal vein
What is the fate of Left vitelline vein?
Regresses > disappears
Fate of Right vitelline vein?
Terminal segment of IVC
Hepatic portal system (Superior mesenteric vein)
Fate of Left umbilical vein?
Anastomosis with ductus venosus, connect with placenta
Fate of Right umbilical vein?
Regresses > disappears
Fate of Left anterior cardinal vein?
Caudal part: oblique vein of left atrium (coronary sinus)
Cranial part: Left internal jugular vein, connected to left brachiocephalic vein
Fate of Right anterior cardinal vein?
Cranial part: Right internal jugular vein
Caudal part: right brachiocephalic vein, SVC
Fate of Medial anastomosis (anterior cardinal veins)?
Left brachiocephalic vein
Fate of Left posterior cardinal vein + interconnecting
Left common iliac vein
Sacral segment of IVC
Fate of Right posterior cardinal vein + interconnecting
Right common iliac vein
Sacral segment of IVC
Fate of Left subcardinal vein + anastomotic channels?
Left renal and gonadal vein
Fate of Right subcardinal vein ?
Right renal and gonadal vein
Renal segment of IVC
Fate of Left supracardinal vein?
Left superior Intercostal vein + intercostal veins
Fate of Right supracardinal vein ?
Azygous vein (form with portion of posterior cardinal vein)
3rd segment of IVC
Fate of left sacrocardinal vein?
What causes double IVC defect?
left sacrocardinal vein fails to disconnect with left subcardinal vein (develops into Left renal and gonadal vein) >
persistent left sarcocardinal vein
Normally right sacrocardinal vein forms hepatic segment of IVC
Results of double IVC defect?
Left common iliac vein may or may not be present
Left gonadal vein remains as normal
Does not affect other organs
Cause of Absence of IVC?
right subcardinal vein (develops into renal segment of IVC normally) fails to connect with liver >
shunts blood directly into
right supracardinal vein (connects with azygous vein)
What causes Left SVC defect?
Left anterior cardinal vein persists; and
Common cardinal vein and proximal part of
right anterior cardinal veins obliterate (normally persist to form internal jugular vein and portion of SVC)
Result of Left SVC defect?
Right brachiocephalic vein channels blood
flow from right to left
Left SVC drains into right atrium through coronary sinus
Cause of Double SVC defect?
Left anterior cardinal vein persists (normally middle segment obliterated, cranial end= internal jugular, caudal end= left superior intercostal vein, Distal end > coronary sinus)
Left brachiocephalic vein fails to form (no anastomosis of anterior cardinal veins)
Result of Double SVC defect?
left SVC drains into right atrium through coronary sinus
5 locations in fetal circulation that allow oxygenated blood from placenta to mix with desaturated blood?
1) Ductus venosus in portal
Sphincter controls blood
pressure flowing from liver
2) IVC (from lower extremities)
3) Head, limbs
5) Ductus arteriosus (allow bypass of lungs to descending aorta)
Sequence of blood flow in fetal circulation? strating at umbilical vein at placenta.
Umbilical vein > Ductus Venosus in Liver > Inferior VC > RA > either RV or oval foramen to LA > RV to ductus arteriosus (or pulmonary vein) to descending aorta OR LA to LV to Aortic arch > Descending aorta > Umbilical arteries > placenta
Fate of umbilical arteries after birth?
Umbilical arteries close,
Proximal portion becomes
superior vesical arteries
Distal parts form medial
Fate of umbilical vein?
Umbilical vein closes >
become ligamentum teres
Fate of ductus arteriosus at birth?
Ductus arteriosus closes to
arteriosum (no need to bypass lungs to descending aorta)