Great Vessel development

Question 1

where does the aortic arteries arise from embryologically and how many arches are there at the beginning

Answer 1

the aortic sac, and there are 6 pairs of aortic arches that are formed within the pharyngeal arches via vasculogenesis and angiogenesis

Question 2

what are the three ways that these primitive system changes into the adult pattern we have today

Answer 2

hypertrophy of some vessels (AA 3, 4, 6)

addition of new vessels (external carotid and distal parts of pulmonary artery

loss of some vessel segments

Question 3

what are the intersegmental arteries and how are they formed

Answer 3

Intersegmental arteries form via vasculogenes (within the paraaxial mesoderm) and connect the dorsal aorta together

these vessels run between the somites and then go on to interconnect to one another cranially and caudally

Question 4

What happens to the fate of the Dorsal Intersegmental arteries

Answer 4

Cervical: 7intersegments

• United by the longitudinal anastomosis and then the roots of 1-6 drop out and the 7th one remains
• these left over longitudinal anastomsis become the vertebral arteries
• the 7th intersegmental artery remains on the left and forms the left subclavian artery and the right it forms a portion of the right subclavian

Thoracic: 12 intersegmentals
-superior and inferior thoracic anastomosis between the intersegmentals contribute to the formation of the internal thoracic arteries and while the intersegmentals them selves contribute to the intercostal arteries

Lumbar: 5 intersegments
-lumbar anastamosis involved in making the epigastric and iliac vessels

Question 5

Fate of the Aortic Arches: I and II

Answer 5

Arches I and IIeventually break up and reorganize

small part of AA I may contribute to maxillary artery

a part of AA II becomes the stapedial arteries

Question 6

Fate of the Aortic Arches: III

Answer 6

Carotid Arch, main feeder to the head

will form the common carotid and proximal portion of internal carotid

remainder of internal carotid comes from the dorsal aorta while the external carotid is a sprout from AA III

Question 7

Fate of the Aortic Arches: IV

Answer 7

hypertrophies and becomes very large

Left:

• Forms part of the aortic arch (aortic sac forms first part, 2nd part is the IV, left dorsal aorta and proximal to distal to the 7th intersegmental artery forms the 3rd and 4th parts
• spiral septum of the outflow tract insures connection of left AAIV to the left ventricle
• on the left the 7th intersegmental makes the entire left subclavian artery

Right:

• forms the proximal part of the right subclavian artery
• the 7th dorsal intersegmental artery makes the distal portion
• the right AA IV makes the proximal portion and intervening dorsal aorta makes the rest

Question 8

Fate of the Aortic Arches: V

Answer 8

Never forms

Question 9

Fate of the Aortic Arches:VI

Answer 9

pulmonary arteries
-each side forms new outgrowth that enters the mesenchyme of the luung (intrapulmonary portion)

-both formed from the proximal portion of Aortic sac and VI

since the heart will descend as the body grows it will pull the recurrent laryngeal nerve with it, however since on the right side the distal part of VI is loss it will only wrap around VI on the left side

Question 10

Fate of the dorsal aorta

Answer 10

portion between the AA III and the AA IV is called the carotid duct and this portion is obliterated

right dorsal aorta will also disappear between the right 7th intersegmental artery and its junctions with the left dorsal aorta

the remaining caudal segments of the right and left dorsal aorta fuse to form the descending thoracic and abdominal aorta

Question 11

Fate of the Vitelline arteries

Answer 11

vessels supplying the yolk sac eventually form the GI vasculature

Question 12

fate of the umbilical arteries

Answer 12

paired ventral branches of the dorsal aorta course the placenta and have connections with the developing bladder

a new connection is made between the 5th lumbar intersegmental arteries and the distal umbilical arteries and then the original proximal connections to the dorsal aortic regress in the embryo

after birth the distal end of umbilical arteries is obiterated (part heading to the umbilical cord at the umbilicus) and become the medial umbilical ligaments a

the more proximal portion off the 5th lumbar intersegmental arteries (iliac vessels) are still referred to as umbilical arteries in the adult with the superior vesicular arteries branching off them to supply the bladder

Question 13

what are the shunts of the fetal circulation

Answer 13

Oxygen rich blood bypasses much of the liver via the ductus venosum and enters the inferior vena cava and RA

much of the blood also passes through the foramen ovalis into the LA and only a bit of blood enters the RV

most of the superior vena cava blood is directed into the right ventricle which will then go into the pulmonary trunk and sneak into the descending aorta via the ductus arteriosus

(only 10 percent of blood makes it to the pulmonary circuit)

Question 14

what areas in the fetus recieve the most oxygenated blood

Answer 14

since the blood from the umbilical vein dumps right into the RA and into the LV

the most oxygenated blood will go to the head, neck , and upper limb since it comes from the ascending Aorta

medium oxygenated will go to the rest since blood from the ductus arteriosus mixes with the descending aorta

Question 15

Abnormalities of Great vessels: Patent ductus arteriosus

Answer 15

in fetus, prostagladins keep the ductus arteriosus open prior to birth
affter birth a drop in prostagladins and increase in endothelin release wiill stimulate smooth muscle contraction of the ductus arteriosus about 10 - 15 hours after birth

-if this doesnt happen 1/2 to 1/3 of blood going into the aorta will be shunted to the pulmonary circulation due to the lower pressure, and blood will circulate their 2-3 times

leads to extra work load for the LV and it will hypertrophy

lead to pulmonary congestion due to the increased blood flow their and eventually congestive heart failure

after 1-3 years can hear a murmur

there is an increased risk for this in the fetus if the mother has a rubella infection

treatment is grostaglandin inhibitor or surgery

Question 16

Abnormalities of Great vessels: Coarctation of the aorta and the two types

Answer 16

Aortic lumen below the orgin of the left subclavian artery is narrowed due to abnormal thickening of the aortic wall
More frequent in turners syndrome
Constriction may be before or after ductus arteriosus

Postductal: sometimes not noticed because collateral circulation is established through collateral ciculation is established through intercostal (intersegmental) arteries and internal thoracic arteries

Preductal: Collaterals usually not well developed
after birth, a little or no blood gets to lower body and legs unless the duuctus arteriosus remains open
-Many times child dies if surgery is not performed to correct this

Question 17

Abnormalities of Great vessels: Aberrant orgin of right subclavian

Answer 17

Right subclavian is formed by distal portion of right dorsal aorta and 7th intersegmental artery

right AA IV and proximal part of right dorsal aorta are obliterated

this may cause problems in swallowing (dysphagia) and respiration (dyspnea) because right dorsal aorta must cross esophagus to reach the right upper limb

usually asymptomatic

Question 18

Abnormalities of Great vessels: double aortic arch

Answer 18

Vascular ring surrounding trachea and esophagus

may lead to esophageal dysfunction nd strangulation of trachea

Question 19

Abnormalities of Great vessels: right aortic arch

Answer 19

the left AA IV and Left dorsal aorta are completely obliterated and replaced by corresponding vessels on right

may cause complaints of dysphagia and dyspnea if the left subclavian artery passes behind the esophagus and the ligamentum arteriosum passes in front of the trachea to reach the right side

Question 20

Abnormalities of Great vessels: Interrupted aortic arch

Answer 20

similar to an abnormal right subclavian except the left AA IV disappears as well

ductus arteriosus remains open and descending aorta and subclavian arteries are supplied with blood of low O2 content

aortic trunk supplies the two common carotid arteries, often seen in DiGeorge syndrome

life threatening unless one intervenes

Question 21

what are the three main venous systems

Answer 21

Vitelline: carries blood from yolk sac to sinus venosus

Umbilical: orginates in chronic villi of placenta carrying O2 rich blood

Cardinal: drains body of the embryo

Question 22

What is the fate of the vitelline veins?

Answer 22

initially empty into sinus horn and as they pass through the septum transversum they become surrounded by liver primordia

as the liver develops the vitelline veins form a vascular plexus (hepatic sinusoids) within the primordia liver

as the left sinus venosus is reduced in size, the blood flow of the left vitelline and the left umbilical is channeled toward the right side within the liver

the proximal portion of the right vitelline vein forms the right hepatocardiac channel that eventually forms the terminal part of the inferior vena cava

the proximal parts of the left vitelline vein (left hepatocardiac channel) will disappear

inferior parts of vitelline veins regress except for that contributing to the portal vein, superior and inferior mesenteric vein and splenic vein

Question 23

what is the fate of the umbilical veins

Answer 23

since vessels pass on either side of the liver they become connected to hepatic sinusoid, proximal part of both sides and remainder of distal right umbilical vein disappears so the left umbilical vein is the only one carrying placental blood to liver

with increased placental circulation, a direct communication is formed between the left umbilical vein and right hepatocardiac channel called the ductus venosus

the ductus venosus allows most of the blood to bypass the sinusodial plexus of liver

Prostaglandins have a role in maintaining patency of duuctus venosus during fetal life

After birth, the left umbilical vein and ductus venosus disappear forming the ligamentum teres hepatis and ligamentum venosum

Question 24

how does the cardinal vein work in the fetus

Answer 24

Anterior and posterior cardinal vein are the early drainage system of the body

they will both join to form the common cardinal vein before entering the sinus horn

anastamoses between the left and right anterior cardinal vein drains most of the head and neck into the cardinal vein on the right side

Question 25

Anterior cardinal vein

Answer 25

an anastomosis between right and left anterior cardinal vein forms the left brachiocephalic vein, superior vena cava forms from right common cacrdinal vein

the connection of the left anterior cardinal with the left common cardinal vein is lost as the left brachiocephalic vein develops. much of the left cardinal vein regresses along with the left sinus horn with remnants forming the coronary sinus

abnormal anterior cardinal vein development can lead to the Superior vena cava draining into the heart via the coronary sinus

Question 26

Posterior cardinal vein

Answer 26

connected to parallel sets of veins called the subcardinal and supracardinal veins, as these new set of veins develop much of the original posterior cardinal veins regress

subcardinal: will form veins primarily associated with the kidney and gonads and contributes to formation of abdominal inferior vena cava
supracardinal: (body wall) will form portions of inferior vena cava and azygos system as well as veins draining the body wall