ICL 4.6: Development of the Vascular System

Question 1

what are the 3 venal systems in the body?

Answer 1

1. Cardinal System of Veins
2. Umbilical System of Veins
3. Vitelline System of Veins

Question 2

what is vasculogenesis?

Answer 2

formation of primitive vessel by fusion of locally formed endothelia vesicles by the process of vasculogenesis

formation of the blood cells in the embryo consists of several phases: the first is the specification of the angioblasts (vascular precursors) –> the second is organization in primary capillary plexus. (vasculogenesis)

Question 3

what is angiogenesis?

Answer 3

outgrowth or branching of preformed vessels

to keep pace with rapid growth of the embryo this capillaries must undergo reorganization thru resorption and sprouting of new vessels a process called angiogenesis

this process occurs not only in development but also in adult during life to adapt to changes conditions of life in normal and pathological process

Question 4

do embryos have blood vessels?

Answer 4

no, early embryo devoid of blood vessels because all the nutrients were receives by diffusion

as the embryo grows, you need a vascular channel to deliver nutrients

the first to develop is the extraembryonic vascular channel which has origins in different organs

vascular channels then become large vessels or capillaries or some disappear altogether; it’s all based on necessity and what the body needs at the time and in a certain location!

Question 5

what does the circulatory system look like at 4 weeks of development?

Answer 5

the first intraembryonic circulatory arc is organized in a similar manner as the fish

the ventral aortic outflow tract from the heart splits into aortic arch arteries passing around the pharynx though the pharyngeal arches and then collecting into a cephalic paired dorsal aorta that distribute blood throughout the body –> a system of cardinal veins collects the blood and returns it to the heart via a common inflow tract

the second arc (vitelline arc or omphalomesenteric arc) extraembryonic circulatory loop supplies the yolk sac

the third arc extraembryonic (umbilical) consist of vessels associated with the allantois ( in humans this is associated with the umbilical vessels) which extend into the placenta and chorionic tissues

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Question 6

what are the 3 venal systems in the body during embryogenesis?

Answer 6

1. Cardinal System of Veins
2. Umbilical System of Veins
3. Vitelline System of Veins (omphalomesenteric)

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Question 7

what are the 2 arterial systems in the body during embryogenesis?

Answer 7

1. dorsal aorta

2. aortic arches

Question 8

what is the cardinal system of veins? what are the 2 parts?

Answer 8

the cardinal veins form the basis for the intraembryonic venous circulatory system

several sets of cardinal veins appears at different times and in different locations; some will regress and other persist either as independent channels or as components of composite veins that also include veins of other cardinal veins

the anterior cardinal veins (superior) bring the blood from the head region via the left and right common cardinal vein

the posterior cardinal veins (inferior) drain the blood from the lower half of the body into the two common cardinal veins

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Question 9

what is the cardinal system of veins? what are the 2 parts?

Answer 9

the cardinal veins form the basis for the intraembryonic venous circulatory system

the anterior cardinal veins (superior) bring the blood from the head region via the left and right common cardinal vein

the posterior cardinal veins (inferior) drain the blood from the lower half of the body into the two common cardinal veins

from there, the blood is emptied into the sinus venosus and into the atrium via the sinus horns

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Question 10

what is the umbilical system?

Answer 10

the umbilical veins bring the nutrient- and oxygen-rich blood from the placental villi via the umbilical cord to the embryo

they are unpaired umbilical veins –> the right umbilical vein disappears while the left umbilical vein gets enlarged and starts forming a big channel in the liver called the ductus venosus which is very important in heart development since during embryonic development it controls the amount of blood that reaches the heart

then the umbilical veins become included in the developing liver –> the ductus venosus will become the ligamentum venosum in the liver

Question 11

what is the vitelline system?

Answer 11

aka the omphalomesenteric system

it’s closely associated with the development of:

1. duodenum
2. liver
3. drain blood of umbilical vesicle

with the development of the liver the omphalomesenteric veins form a thick hepatic plexus and they also anastomose with the umbilical veins

through various transformative and degenerative processes the vena portae arises which brings the blood from the intestines into the liver – by this means the absorbed nutrients from the intestines can be taken up later through the liver and metabolized

on the other hand, a short-cut, the ductus venosus, is engendered from the thick network of anastomoses of vitelline veins; up to the time of birth, it takes the blood from the umbilical vein and the omphalomesenteric veins and directs it directly into the sinus venosus of the heart

during the course of the early cardiac development the left sinus horn atrophies and with it the posthepatic part of the left omphalomesenteric vein – so now all of the blood from the liver is conveyed via the right omphalomesenteric vein to the sinus venosus

Question 12

which venal system are the pulmonary veins part of?

Answer 12

they are not assigned to any of the 3 venal systems! they develop independently and there’s no consensus about their development

some think that they branch from the left atrium while others thing they form as a a solitary vessel

Question 13

what does the arterial system look like?

Answer 13

The system of aortic arches in early human embryo is organized along the same principles as the system of arteries supplying blood to the gills of many aquatic lower vertebrates. Blood exits from a common ventricle into a ventral aortic root, from which it is distributed through the branchial arches by pairs of aortic arches. In gilled vertebrates the aortic arch arteries branch into capillary beds, where the blood become oxygenated as it passes thru the gills. In mammalians the aortic arches remains as a unit because the oxygenation is done in the placenta. The aortic arches empty into a paired dorsal aorta where the blood enters the systemic circulation.

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Question 14

what are the adult derivatives of the arches?**

Answer 14

arch 1: regresses, and part of the arch becomes part of the maxillary artery

arch 2: regresses and becomes steapedial artery

arch 3: forms the common and internal carotid arteries; doesn’t regress!

1,2,3 go to the head
_____________

R. arch 4: forms the proximal right subclavian artery

L. arch 4: forms arch of the aorta

R. arch 6: forms part of the right pulmonary artery

L. arch 6: forms part of left pulmonary artery and ductus arteriosus

R. arch 7: forms part of the right subclavian artery

L. arch 7: forms entire left subclavian artery

R. dorsal aorta: regress and forms middle of the right subclavian artery

L. dorsal aorta: forms descending thoracic aorta

aortic sac: forms ascending aorta and brachiocephalic artery

Question 15

what is the role of the neural crest cells?

Answer 15

they give signals to the endothelial vessels so that the aortic arch is preserved after the neural crest is gone

Question 16

why are the recurrent laryngeal nerves located where they are?

Answer 16

the vagus nerve wraps around the 4th arch

but the 4th arch turns into the aortic arch and subclavian artery on the left and right side, respectively

Question 17

what are some of the aortic arch anomalies?

Answer 17

1. right aortic arch
2. double aortic arch
3. aberrant subclavian artery
4. interrupted aortic arch

Question 18

what is the right aortic arch anomaly?

Answer 18

the right aortic arch results from developmental obliteration of the left fourth branchial arch artery and the regression of the left dorsal aorta

in the anomaly, the aortic arch is constructed from the equivalent vessels on the right side

to reach the arch, the ductus arteriosus must traverse the midline and in doing so, it may produce constriction of the esophagus

Question 19

what is the double aortic arch anomaly?

Answer 19

a double aortic arch is an anomaly of the arch resulting in two arches that surround the esophagus and trachea in the superior mediastinum to form a vascular ring

dysphagia and respiratory distress may follow

it results from a failure of regression of the section of the right dorsal aorta between the seventh intersegmental artery and the junction with the left dorsal aorta

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Question 20

what is the interrupt aortic arch anomaly?

Answer 20

it is caused by obliteration of the left fourth branchial arch artery which is related to the aortic arch

so the proximal part of the aortic arch artery divides to form the brachiocephalic trunk and left common carotid arteries and there is no continuity of the arch beyond these branches

the descending aorta doesn’t form! so instead the ductus arteriosus becomes very large and functions as the aorta

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Question 21

what is the right subclavian artery anomaly?

Answer 21

rarely, the right subclavian artery arises from the aortic arch distal to the left subclavian artery

to reach the right side of the thorax, it passes behind the esophagus and trachea to produce a vascular ring

developmentally, this condition results from regression of the right fourth branchial arch artery

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Question 22

what’s the adult derivative of the 1st aortic arch?

Answer 22

it regresses and forms part of the maxillary artery

Question 23

what’s the adult derivative of the 2nd aortic arch?

Answer 23

it regresses and forms part of the stapedial artery

Question 24

what’s the adult derivative of the 3rd aortic arch?

Answer 24

forms the common and internal carotid arteries

Question 25

what’s the adult derivative of the 4th aortic arch?

Answer 25

R = proximal right subclavian artery

L = arch of the aorta

Question 26

what’s the adult derivative of the 5th aortic arch?

Answer 26

trick question, there is no 5th aortic arch! it never developed

Question 27

what’s the adult derivative of the 6th aortic arch?

Answer 27

R = forms part of the right pulmonary artery

L = forms part of the left pulmonary artery and ductus arteriosus

Question 28

what’s the adult derivative of the 7th aortic arch?

Answer 28

R = forms part of the right subclavian artery

L = forms the entire left subclavian artery

Question 29

what’s the adult derivative of the dorsal aorta?

Answer 29

R = it regresses and forms the middle of the right subclavian artery

L = forms the descending thoracic aorta

Question 30

what’s the adult derivative of the aortic sac?

Answer 30

it forms the ascending aorta and brachiocephalic artery