Embryo 4 Flashcards
Vasculogenesis
- formation of new vascular channels by assembly of individual cells precursors called angioblast or hemoangioblast
- from mesoderm
Mesenchyme
embryonic CT
Angiogenesis
development of blood vessels from pre-existing vessels (adults/cancer)
Arteriogenesis
remodeling of existing arteries in response to different pathological/physiological changes
What two cells do angioblasts give rise to?
- Hematopoeitic stem cells
2. Endothelial precursor cells
When does vasculogenesis begin?
end of third week
Where are Hematopoeitic stem cells formed?
AGM
What do blood islands produce?
Plexuses
*channels form within the plexuses, and these channels then enlarge/unite to form arteries and veins
Angioma
- Capillary Hemagioma (nevus vascular): excessive growth of small capillary networks->cherry angiomas (campbell de morgan spots)
- Cavernous Hemagioma: proliferation of large dilated vascular channels
- Hemangioma of infancy: benign tumor; consists of many endothelial cells (due to v asculogenesis; enlarge birth -one year, and then many will regress
Infants with segmental hemangioma should also be evaluated for…
PHACE syndrome
What are the three branches of the fused dorsal aorta?
- Ventral Segmental Arteries
- Lateral Segmental Arteries
- Dorsal Segmental Arteries
What do Ventral Segmental Arteries supply?
splanchnic layer of lateral plate mesoderm and endoderm (ex. IMA, SMA)
What do Lateral Segmental Arteries supply?
intermediate mesoderm derivatives (ex. renal, ovarian, and testicular arteries)
What do Dorsal Segmental Arteries supply?
derivatives of somites; when they come off we call them intersegmental arteries (ex. intercostal and lumbar arteries)
What does the first formed aortic arch supply?
first pharyngeal arch
What forms day 26-32? 32-37?
- rudiments of remaining aortic arches (as 3 forms, 1 degenerates; 4, 2…)
- completion of aortic arches; send a lot of branches to the head
Derivatives of aortic arches: 1st
external carotid, maxillary
Derivatives of aortic arches: 2nd
stems of stapedial arteries
Derivatives of aortic arches: 3rd
common carotid, internal carotid
Derivatives of aortic arches: Aortic sac
brachiocephalic artery, base of arch of aorta
Derivatives of aortic arches: 4th
left: medial portion of arch of aorta
right: proximal right subclavian
Derivatives of aortic arches: 6th
pulmonary arteries
- left: distal ductus arteriosus
- right distal degenerates
Derivatives of aortic arches: 7th intersegmental arteries
right: distal part of right subclavian
left: entire left subclavian
Derivatives of aortic arches: dorsal aorta
right: portion of right subclavian artery
left: descending aorta
Fetal Blood Circulation
O2 blood from placenta–>left umbilical vein–>liver–>ductus venous–>inferior vena cava–>right atrium–>foramen ovale/secundum–>left atrium–>left ventricle–> aorta–>branches going to head/descending aorta
What happens if theres too much blood coming form the placenta?
sphincter constructs, and directs blood into the sinusoids of the liver
What three things do we get with aeration of the lungs?
- Decrease in pulmonary vascular resistance
- Increase in pulmonary blood flow
- Thinning of walls of pulmonary arteries
What is the round ligament of liver/ligamentum teres?
remnant of the left umbilical vein
Where does ligamentum arteriosum come from?
- ductus arteriosus fuses within 72 hours after birth
- due to increased prostaglandins and bradykinin
Coarctation of Aorta
- due to aortic constriction (above/below ductus arteriosus)
- normal/high pulses/BP of UE; low/absent for LE
a. Preductal: can become cyanotic (prostaglandins are given, so duct arteriosus doesn’t close)
b. Postductal: fetus often develops collateral system (angiogenesis)
*due to smooth muscle abnormally goes into aorta, and constricts OR aortic arches remodeled, and narrowed
Double Aortic Arch
- persistence of distal portion of right dorsal aorta (normally it becomes right subclavian, and the rest degenerates)
- vascular rings forms around the trachea/esophagus
- symptoms: stridor, respiratory infections/distress, wheezing, cough, esophageal complains (dysphagia, feeding difficulty, vomiting)
Interrupted Aortic Arch
- both right and left 4th aortic arch arteries are obliterated
- distal right dorsal aorta is retained; normally have VSD and PDA
- Symptoms (day 1-2): weakness, fatigue, poor feeding, false HR, low O2 levels (especially legs)
- associated with DiGeorge Syndrome
*right side always gets O2; left side is variable
What is the most severe form of a coarctation of the aorta?
Interrupted Aortic Arch
Abnormal Origin of the Right Subclavian Artery
- arises from the distal part of the right dorsal aorta, and the 7th intersegmental artery
- the right 4th aortic arch, and the proximal part of the right dorsal aorta obliterate
- right subclavian passes behind the esophagus and trachea
- some people are asymptomatic, and some have esophageal problems
- may see lower pulse in right UE than left because the Rt. subclavian can get compressed on by the vertebral bodies
Right Aortic Arch
- the left fourth arch and left dorsal aorta are obliterated and replaced by the corresponding vessels on the right side
- swallowing can be impaired if ligamentum arteriosum lies on the left side and passes behind the esophagus
What are the three sets of veins?
- Cardinals (anterior, posterior, common): O2 poor blood from body back to heart
- Vitelline (around yolk sac/liver): O2 poor blood from body back to heart
- Umbilical: O2 rich blood from placenta back to heart
Vitelline Veins
- proximal to heat: left: degenerates; right persists
- within liver: right forms hepatic vein (part of inferior vena cava); right and left form portal vein (from gut)
Umbilical Veins
- Right degenerates entirely
- Left persists: brings O2 rich blood from placenta back to heart
a. Proximal degenerates
b. Anastomoses with ductus venosus
c. Distal persists in embryo providing placental return
Cardinal Veins
a. Anterior: drainage from cranial territory
- right forms internal jugular and superior VC
- left forms left brachiocephalic
b. Posterior: drainage from body wall
- degenerate except fro root of azygos and common iliac; replaced by sub cardinal and supra cardinal veins
Venous System Defects: left superior vena cava
-persistence of left anterior cardinal vein and obliteration of the common cardinal and proximal part of the anterior cardinal veins on the right
Venous System Defects: double superior vena cava
-persistence f the left anterior cardinal vein and failure of the left brachiocephalic vein to form
Inferior Vena Cava
- Hepatic segment
- Prerenal
- Renal
- Postrental
- Malformations
- right vitelline/hepatic veins and sinuses
- right sub cardinal
- sub cardinal-supracardinal anastomosis
- right supra cardinal
- Persistence of a sacrocardinal vein (2 inferior VCs)
