Chapter 2 - Embryology Flashcards
Anomalies of SVC (2 types)
Double SVC
Left sided SVC
What does the embryonic endoderm secrete to induce vessel formation of the splanchnic mesoderm
Bone morphogenic protein TGF-beta This happens by day 18
What are the stimulating factors to trigger vasculogenesis
Indian hedgehog Bone morphogenic protein TGF-beta They induce the yolk sac’s mesoderm to form hemangioblastic aggregates
Embryologic venous development: umbilical veins
R umbilical vein regress
L umbilical vein form anastomosis with ductus venosus
After birth L umbilical vein becomes ligamentum teres (hepatis) inside falciform ligament
Figure: Proangiogenic and antiangiogenic factors
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Renal vein anomalies in embryology
Retro-aortic L renal vein (if anterior component regresses)
L circum-aortic renal vein (if both anterior and posterior renal vein persist)
Both due to persistent posterior renal vein
Define: Dysphagia luroria
Difficulty swallowing due to compression from retroesophageal right subclavian artery
only occurs in 5% with this anomaly
At day 60, what organs take over as the source of blood
Liver, spleen, thymus, bone marrow
Which angiogenic factors lead to endothelial specificity
VEGF: fenestrated endothelium in endocrine glands and kidneys Angiopoietin-1: tight junctions at blood-brain barrier
At which day does hemangioblastic aggregates form in the connecting stalk and chorion
Day 17 These form the extraembryonic umbilical vessels
Double aortic arch: etiology, symptoms
Failure of the R dorsal aorta distal to R 7th intersegmental artery to involute
Passes posterior to esophagus and joins L aortic arch that passes anterior to trachea
Symptoms of esophageal and tracheal compression
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Coarctation of the aorta: common location, etiology, findings
Location: distal to ligamentum arteriosum
preductal type immediate proximal to ligamentum
Etiology: hypothesis is similar to obliteration of ductus arteriosus with oxygen sensitive smooth muscle contraction leading to eventual fibrosis
Findings: collateral vessels, notching of ribs 3-8 because of increased intercostal arteries size
Figure 3 sign: prestenotic dilatation of aortic arch and L subclavian; poststenotic dilataion of descending
Embryological venous development: cardinal veins
Anterior cardinal veins join posterior cardinal veins = short common cardinal veins
Anterior cardinal veins = SVC (junction of L and R brachiocephalic veins)
Cranial portion becomes IJ; parts join with venous plexuses of face to form EJ
Subclavian veins (venous plexuses of limb bud) empty into ACV
Anastomosis of L and R ACV become L brachiocephalic vein
R atrium = enlargement of R ACV and R CCV
Coronary sinus = L CCV
Posterior cardinal veins, subcardinal veins, supracardinal veins = IVC, tributaries, azygos system
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Right aortic arch: two types
etiology and symptoms
Involution of the L dorsal aorta and persistence of the R dorsal aorta
Ligamentum arteriosum from distal R 6th arch
Right aortic arch with aberrant L subclavian (or retroesophageal component): Arch passes to L side posterior to esophagus
Vascular ring formed because of ligamentum arteriosum
Right aortic arch with mirror image branching: arch passes anterior to esophagus and trachea
- higher incidence of malformations, infants almost all cyanotic (inc. ToF)
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Figure: arterial and venous fated angioblast pathways
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Fate of segmental arteries from segments/somites
Cervical, thoracic, lumbar
Ventral and dorsal for each
Cervical: dorsal = vertebral artery, deep cervical, ascending cervical
Thoracic: dorsal = intercostal
ventral = superior thoracic artery, internal thoracic, superior epigastric
Lumbar: dorsal = lumbar arteries; 5th lumbar pair = common iliac
ventral = allantoic (umbilical, internal iliac) and vitelline (celiac, SMA, IMA for foregut, midgut, hindgut)
Normal vascular development of the lower extremity
Ventral branch of 5th lumbar intersegmental artery becomes internal iliac artery gives rise to axial artery
Second branch of the 5th lumbar intersegmental artery becomes the EIA and develops into iliofemoral artery
Axial artery regress (8th week) but parts persist as sciatic (ischiadic) artery, popliteal artery and peroneal artery
Rest develop as sprouts of EIA
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Angiogenic sprouting from existing vessels is facilitated by this factor
Hypoxia this in term upregulates the following: VEGF, angiopoietin-1 and 2, nitric oxide synthase
Embryologic venous development: vitelline veins
Vitelline veins form venous plexus (liver hepatic sinusoids) before entering sinus venosus
L vitelline vein regress forcing blood to go through liver
R vitelline vein = ductus venosus
Cranial portion of R vitelline = IVC
Caudal potion of R vitelline = portal and SMV
L to R vitelline anastomoses = splenic, IMV
After birth ductus venosus becomes ligamentum venosum
Popliteal entrapment syndrome: embryological cause
Attachment of the medial head of the gastrocnemius before maturation of the popliteal artery
Compression of the popliteal artery against the medial condyl of femur
Gene responsible for correct patterning and integrity of lymphatic vessels
Angiopoietin-2
lacking this gene results in misshapen, leaky and lack typical association of smooth muscle cells
Cause and problems of patent ductus arteriosus
Most common vascular anomaly
Constricts due to response of oxygen-sensitive smooth muscle cells in its walls to exposure of high O2
Obliterates by 1 month to become ligamentum arteriosum
If patent = pulmonary hypertension
Define: Kommerell diverticulum
Aneurysm formation from a retroesophageal right subclavian artery
Unclear rate of occurance
Normal connection between lymphatic and venous system in adults (2)
Thoracic duct to L subclavian vein
R lymphatic duct to R subclavian vein
Popliteal artery development
Sciatic artery gives deep popliteal artery (anterior to popliteus muscle)
Iliofemoral artery gives superficial popliteal artery (posterior to popliteus mucle)
Distal section of deep popliteal regress
Proximal section of deep popliteal join with superficial popliteal artery
Two variations of upper limb vascular anomalies
High origin of radial artery proximal to level of elbow at cubital fossa = 14.2%
Persistence of the median artery to palm = 12%
Embryologic development of the venous system
Higher variations
4 weeks: 3 paired venous system
Vitelline vein drain yolk sac and GI tract
umbilical vein bring blood from placenta
cardinal vein drains embryo
What is the first step in the development of the vascular system
Modification of splanchnic mesodermal cells into angioblasts –> form vesicular aggregates in the splanchnic mesoderm of the embryo and extraembryonic regions (yolk sac, connecting stalk, chorion)
How do angioblasts become vessels
They develop into flattened endothelial cells that form small vessel cords that eventually coalesce This is vasculogenesis
Fate of primitive aortic arches
1st: regress quickly
2nd: regress quickly
3rd: CCA and proximal ICA
4th: L = aortic arch between L CCA and L subclavian
R = proximal segment of R subclavian
5th: never develops in humans
6th: pulmonary arteries
R distal portion disappear
L distal portion = ductus arteriosus
distal ICA from dorsal aorta between 1st and 3rd arches
dorsal aorta between 3rd and 4th arches disappear
distal segment of R subclavian from right dorsal aorta and R 7th intersegmental artery
R horn of aortic sac elongate to become innominate
L horn of aortic sac = proximal aortic arch
Percentage of people with single artery to each kidney
71%
Variations due to embryologic failure of segmental arteries to fuse
higher incidence in ectopic kidneys or horshoe kidneys
Retroesophageal right subclavian artery: etiology and symptoms
R 4th aortic arch and the connected R dorsal aorta involuted
Right dorsal aorta distal to R intersegmental artery persist and forms R subclavian
R subclavian pushed posterior by developing aortic sac (proximal arch)
95% asymptomatic; 5% esophageal compression
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Persistent sciatic artery:
incidence
course
findings
complication
0.05%
Follows sciatic nerve: pass into thigh through sciatic notch; posterior to adductor magnus; join popliteal artery
Absent femoral pulse, normal popliteal pulse; can be traumatized by sitting
Early atherosclerotic changes, aneurysm formation, sciatic nerve compression
Anomalies of IVC (2 types)
Duplication of IVC
L sided IVC
Function of the gene prospero-related homeobox-1 (Prox-1)
Budding of the lymphatic system from veins
What are the components of the hemangioblastic aggregates
Inner core of hematopoietic stem cells Outer rim of endothelial cells Hematopoietic stem cells serves as source of blood cells in first 60 days
Embryologic variations in aortic arch
65% normal
22% with “bovine arch: brachiocephalic gives off R subclavian, R CCA and L CCA
- short brachiocephalic trunk that bifurcate immediate; L CCA arise from arch at base of brachiocephalic
- L vertebral from arch between L CCA and L subclavian
- L brachiocephalic trunk
When does vasculogenesis begin
Day 17 in yolk sac
Normal vascular development of the upper extremity
- 7th cervical intersegmental artery join axial artery in limb bud
- axial artery becomes axillary, brachial, anterior interosseus
- deep brachial is a bud from brachial; supply posterior arm
- brachial artery gives rise to radial and ulnar
- common interosseos bifurcate to anterio and posterior and median
- radial and ulnar replace anterior interosseos artery as dominant artery of hand; median regresses
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Embryological lymph sacs (6)
origin of each
timing of development
Jugular lymph sacs (2): bud off anterior cardinal vein (junction of subclavian and IJ); 5th week
Posterior lymph sacs (2): bud from caudal segment of posterior cardinal veins (junction of IIV and EIV); late 6th week
Retroperitoneal lymph sac: mesonephric venous system near suprarenal gland; end of 5th week
Cisterna chyli: veins at L3-L4; end of 5th week
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Key constituents of the basement membrane
Type IV collagen Laminins
Figure: primitive aortic arches and their evolvement
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