SEM_7_02_Allantoic Circulation in Embryonic Development
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Questions and Answers

Which circulatory pathway is responsible for carrying blood to the yolk sac and then back to the heart to be distributed within the embryo?

  • Placental circulation
  • Allantoic circulation
  • Pulmonary circulation
  • Vitelline circulation (correct)

    • What is the main difference between the prenatal and post-natal circulations?

  • Size of blood vessels
  • Location of metabolic organs (correct)
  • Direction of blood flow
  • Composition of blood

    • Which system contributes to the formation of the placental circulation?

  • Arterial system
  • Allantoic circulation (correct)
  • Lymphatic system
  • Venous system

    • Where does the vitelline circulation carry blood to be enriched with nutrients?

    <p>Yolk sac</p> Signup and view all the answers

    What is the function of vitelline circulation in birds and reptiles?

    <p>Carries blood from the yolk sac to the embryo and back</p> Signup and view all the answers

    What happens to vitelline circulation in mammals during early gestation?

    <p>It regresses and becomes rudimentary</p> Signup and view all the answers

    Which circulatory arc establishes a connection between the chorioallantoic membrane and the embryo?

    <p>Allantoic/placental circulation</p> Signup and view all the answers

    What does intra-embryonic circulation refer to?

    <p>Circulation confined to the interior of the body</p> Signup and view all the answers

    What happens to the distal portions of vitelline circulation as mentioned in the text?

    <p>They transform into intestinal veins and liver vessels</p> Signup and view all the answers

    Which vessel does the right vitelline vein become according to the text?

    <p>Portal vein, caudal vena cava, and main intestinal artery</p> Signup and view all the answers

    What happens to the left vitelline vein as mentioned in the text?

    <p>It mostly involutes, but some remnants contribute to formation of permanent vessels</p> Signup and view all the answers

    What does allantoic circulation ramify throughout?

    <p>Chorioallantoic membrane and embryo</p> Signup and view all the answers

    What type of circulation does allantoic circulation become in mammals?

    <p>Placental circulation</p> Signup and view all the answers

    What is the origin of permanent circulation in adults according to the text?

    <p>Intra-embryonic circulation</p> Signup and view all the answers

    What is the main reason that most of the relatively oxygenated blood coming from the caudal vena cava is guided towards the foramen ovale?

    <p>Higher pressure in the right atrium compared to the left atrium</p> Signup and view all the answers

    What is the purpose of diverting the less oxygenated blood from the right ventricle through the ductus arteriosus into the descending aorta?

    <p>To prevent pulmonary circulation</p> Signup and view all the answers

    What determines the closure of the foramen ovale at birth?

    <p>Decreased pressure in the right atrium and increased pressure in the left atrium</p> Signup and view all the answers

    What happens immediately after cutting the umbilical cord at birth?

    <p>Stimulation of receptors in the respiratory centre</p> Signup and view all the answers

    What leads to closure of the ductus venosus after cutting the placental input?

    <p>Reflexive contraction of musculature in the wall of the ductus venosus</p> Signup and view all the answers

    What determines whether or not patent foramen ovale is present?

    <p>Failure of functional closure of foramen ovale after birth</p> Signup and view all the answers

    What is responsible for closing of the ductus arteriosus immediately after birth?

    <p>Reflexive muscle contractions</p> Signup and view all the answers

    What is responsible for determining crucial changes in arterial pressure at birth?

    <p>Cutting of umbilical cord and activation of breathing</p> Signup and view all the answers

    What is responsible for increasing arterial pressure in left atrium at birth?

    <p>Increased return of blood from lungs via pulmonary veins</p> Signup and view all the answers

    What is responsible for decreased pressure in right side of heart at birth?

    <p>Rupture of umbilical cord</p> Signup and view all the answers

    What leads to permanent closure of ductus arteriosus after a few weeks or months?

    <p>Reflexive muscle contractions</p> Signup and view all the answers

    What is the role of the ductus venosus during fetal development?

    <p>It shunts oxygenated blood from the placenta to the caudal vena cava.</p> Signup and view all the answers

    What happens in some dogs if the ductus venosus fails to occlude after birth?

    <p>It results in a patent ductus venosus, allowing toxic digestive products to bypass the liver and affect the brain.</p> Signup and view all the answers

    What does the left umbilical vein carry during fetal development?

    <p>Oxygenated blood from the placenta to the liver, most of which is shunted through the ductus venosus to the caudal vena cava.</p> Signup and view all the answers

    What is the fate of umbilical veins after passing through a rich plexus of chorionic capillaries?

    <p>They undergo remodeling after birth, with oxygenated blood entering the heart via the caudal vena cava, and they become the only vessels from the placenta to enter the embryo.</p> Signup and view all the answers

    What distinguishes fusion of umbilical veins in horses and pigs from that in ruminants and carnivores?

    <p>In horses and pigs, veins fuse on entering the abdominal wall and four vessels are present, while in ruminants and carnivores they fuse before entering the umbilical cord and three vessels are present.</p> Signup and view all the answers

    What is always necessary for expansion of allantoic vessels in the placenta according to the text?

    <p>Development of umbilical vessels</p> Signup and view all the answers

    What does blood collected from chorion do according to this passage?

    <p>It is returned to embryo by allantoic veins after passing through rich plexus of chorionic capillaries.</p> Signup and view all the answers

    What happens to the less-oxygenated blood from the cranial vena cava in the fetal circulation?

    <p>It is diverted through a fetal blood vessel called the ductus arteriosus into the descending aorta</p> Signup and view all the answers

    What leads to the closure of the foramen ovale at birth?

    <p>Changes in pressure in the right and left atria</p> Signup and view all the answers

    What is responsible for ensuring that vital structures like the brain and coronary circulation receive the best-oxygenated blood in fetal circulation?

    <p>Pumping of relatively-high-oxygenated blood from the left atrium to the left ventricle</p> Signup and view all the answers

    What is the fate of umbilical veins after cutting the umbilical cord at birth?

    <p>They collapse and become non-functional</p> Signup and view all the answers

    What determines whether or not patent foramen ovale is present?

    <p>Changes in pressure in the right and left atria</p> Signup and view all the answers

    What happens to vitelline circulation in mammals during early gestation?

    <p>It carries blood to be enriched with nutrients</p> Signup and view all the answers

    What is responsible for increased arterial pressure in the left atrium at birth?

    <p>Activation of the lungs and pulmonary circulation</p> Signup and view all the answers

    What leads to permanent closure of ductus arteriosus after a few weeks or months?

    <p>Reflexive muscle contractions</p> Signup and view all the answers

    What does intra-embryonic circulation refer to?

    <p>Circulation within different layers of embryonic tissue</p> Signup and view all the answers

    What distinguishes fusion of umbilical veins in horses and pigs from that in ruminants and carnivores?

    <p>Timing of fusion in relation to birth</p> Signup and view all the answers

    During the development of the arterial system, what is the fate of the dorsal aortas?

    <p>They merge to form a single dorsal aorta</p> Signup and view all the answers

    What is the fate of the cranial portion of the dorsal aorta during the fetal development?

    <p>It forms a series of paired aortic arches</p> Signup and view all the answers

    At an early stage of embryo development, what connects the dorsal and ventral aorta on each side of the foregut?

    <p>Successive parallel aortic arches</p> Signup and view all the answers

    What do the first and second pair of aortic arches contribute to in most mammals?

    <p>Supplies to the neck and head arteries</p> Signup and view all the answers

    What is the fate of the right aortic arch in the development of aortic arches?

    <p>Contributes to the right subclavian artery and then degenerates</p> Signup and view all the answers

    What occurs when vascular ring anomalies disrupt the development or dissolution of the aortic arches?

    <p>Constriction around the esophagus</p> Signup and view all the answers

    What is the embryonic sinus venosus of the heart responsible for?

    <p>Receiving return blood from vitelline veins and umbilical veins</p> Signup and view all the answers

    What do the subcardinal veins form in the developing embryo?

    <p>Most of the caudal vena cava, draining blood from the embryonic kidneys and gonads</p> Signup and view all the answers

    From which structures do lymphatic vessels develop?

    <p>Lymph sacs arising from developing veins and derived from mesoderm</p> Signup and view all the answers

    How do lymph nodes develop according to the passage?

    <p>From localised mesodermal invaginations that divide the lumen of the vessels into sinusoids</p> Signup and view all the answers

    During the development of the arterial system, what is the fate of the two dorsal aortas?

    <p>They fuse to form the descending aorta</p> Signup and view all the answers

    What is responsible for the formation of the aortic arches during the early stage of embryo development?

    <p>Transient branchial structures</p> Signup and view all the answers

    What happens to the cranial portion of the dorsal aorta during fetal development?

    <p>It forms a series of pair aortic arches</p> Signup and view all the answers

    What is the main role of the ventral aorta at an early stage of embryo development?

    <p>Connects with the dorsal aorta</p> Signup and view all the answers

    Which pair of aortic arches contributes to the face and neck arteries but remains rudimentary in most mammals?

    <p>First and second pair</p> Signup and view all the answers

    What does the left aortic arch become in the definitive arch of the aorta?

    <p>Left subclavian artery</p> Signup and view all the answers

    What happens to the right aortic arch in the development of aortic arches?

    <p>Contributes to the right subclavian artery</p> Signup and view all the answers

    What is the fate of the fifth and sixth pair of aortic arches in birds and mammals?

    <p>Usually rudimentary or never develop</p> Signup and view all the answers

    What happens when vascular ring anomalies disrupt the development or dissolution of the aortic arches?

    <p>Constriction around the esophagus occurs</p> Signup and view all the answers

    What do dorsal segmental arteries supply in the thoracic and lumbar region?

    <p>Intercostal and lumbar arteries</p> Signup and view all the answers

    Which type of arteries do lateral segmental arteries primarily supply?

    <p>Ovarian, testicular, renal, and adrenal arteries</p> Signup and view all the answers

    Initially, what do ventral segmental arteries become as they develop?

    <p>Paired visceral branches for stomach and intestines</p> Signup and view all the answers

    What do vascular ring anomalies lead to when they disrupt the development or dissolution of the aortic arches?

    <p>Constriction around the esophagus occurs</p> Signup and view all the answers

    In which developmental stage do aortic arches initially develop in air-breathing animals?

    <p>Branchial stage</p> Signup and view all the answers

    At what stage does development of the aorta begin in domestic mammals?

    <p>Third week of gestation</p> Signup and view all the answers

    When do derivatives of aortic arches undergo structural changes to form definitive vascular patterns for head and neck, aorta, and pulmonary circulation?

    <p>During fetal stage</p> Signup and view all the answers

    What is responsible for the formation of the definitive venous system in the embryo?

    <p>Cardinal venous system</p> Signup and view all the answers

    What are the caudal cardinal veins temporarily replaced by in the embryo?

    <p>Supracardinal and subcardinal veins</p> Signup and view all the answers

    From which vessels do the azygos veins in adults develop?

    <p>Supracardinal veins</p> Signup and view all the answers

    Where do lymph sacs, which give rise to lymphatic vessels, arise from in the embryo?

    <p>Mesoderm</p> Signup and view all the answers

    What do lymph nodes develop from during embryonic development?

    <p>Lymph sacs</p> Signup and view all the answers

    Which vessels are responsible for draining the blood from the embryonic kidneys and gonads?

    <p>Subcardinal veins</p> Signup and view all the answers

    What is responsible for the initial development of a reticular framework within lymph nodes?

    <p>Lymph sacs</p> Signup and view all the answers

    What do the supracardinal veins develop to drain in the developing embryo?

    <p>Dorsal region of the body</p> Signup and view all the answers

    What is derived from developing veins in order to form lymph sacs?

    <p>'Cardinal venous system'</p> Signup and view all the answers

    Study Notes

    • Embryonic blood circulation involves three circulatory arcs: vitelline, allantoic/placental, and intra-embryonic.

    • The vitelline circulation is the earliest to develop and carries blood from the yolk sac to the embryo and back.

    • In birds and reptiles, vitelline circulation is important as they have a large amount of yolk in the sac.

    • In mammals, the vitelline circulation is rudimentary and eventually regresses during early gestation.

    • The allantoic circulation establishes a connection between the chorioallantoic membrane and the embryo, and in mammals, it forms the placental circulation.

    • The intra-embryonic circulation is confined to the interior of the body and is the origin of the permanent circulation in the adult.

    • The vitelline circulation undergoes remodeling as its distal portions transform into intestinal veins and liver vessels.

    • The right vitelline vein becomes the portal vein, the caudal vena cava, and the main intestinal artery.

    • The left vitelline vein mostly involutes, but some remnants contribute to the formation of permanent vessels.

    • The allantoic circulation ramifies throughout the chorion and interchanges gases with the outside in birds, or becomes the placental circulation in mammals.

    • In some species, the allantoic sac becomes rudimentary and the allantoic circulation is not needed for waste disposal.

    • The development of umbilical vessels is always necessary for the expansion of allantoic vessels in the placenta.

    • Blood from the placenta is brought towards it by the right and left umbilical arteries, which arise from the dorsal aorta and terminate in the chorioallantoic membrane.

    • After passing through a rich plexus of chorionic capillaries, the blood is collected from the chorion and returned to the embryo by the allantoic veins.

    • The umbilical veins undergo remodeling after birth, with the oxygenated blood entering the heart via the caudal vena cava, and the left umbilical vein being the only vessel from the placenta to enter the embryo.

    • In some species, such as horses and pigs, the umbilical veins fuse before entering the umbilical cord and three vessels are present. In other species, such as ruminants and carnivores, the veins fuse on entering the abdominal wall and four vessels are present.

    • During fetal development, the left umbilical vein carries oxygenated blood from the placenta to the liver, most of which is shunted through the ductus venosus to the caudal vena cava.

    • The ductus venosus is a shunt inside the liver that allows oxygenated blood from the placenta to bypass the liver and reach the heart sooner.

    • In some dogs, the ductus venosus fails to occlude after birth, resulting in a patent ductus venosus, which is a congenital portosystemic shunt that allows toxic digestive products to bypass the liver and affect the brain.

    • The right atrium of the heart receives blood from both the cranial (lower oxygen saturation) and caudal (higher oxygen saturation) parts of the fetal body.

    • The relatively-oxygenated blood from the caudal vena cava is predominantly directed towards the left atrium via the foramen ovale due to haemodynamic factors.

    • The relatively-high-oxygenated blood is then pumped from the left atrium to the left ventricle and into the ascending aorta, ensuring that vital structures like the brain and coronary circulation receive the best-oxygenated blood.

    • The less-oxygenated blood from the cranial vena cava is directed across the tricuspid valve into the right ventricle.

    • This less-oxygenated blood is pumped towards the pulmonary trunk but does not reach the lungs due to their non-functionality in the fetus.

    • Instead, it is diverted through a fetal blood vessel called the ductus arteriosus into the descending aorta.

    • The placenta receives relatively-deoxygenated blood from the fetal systemic arterial circulation and returns blood with the highest oxygen levels to the fetal venous circulation.

    • At birth, the placental circulation is switched off, leading to the activation of the lungs and the pulmonary circulation.

    • The closure of the foramen ovale and the ductus venosus after birth is due to the changes in pressure in the right and left atria.

    • The ductus arteriosus closes immediately after birth due to reflexive muscle contractions.

    • The closure of these fetal circulatory shunts is crucial for the proper functioning of the post-natal cardiovascular system.

    • The segmental (intersegmental) arteries are branches of the dorsal aorta extending between somites, contributing to visceral and body wall blood supply.

    • The embryonic sinus venosus of the heart receives return blood from different parts: vitelline veins (yolk sac), umbilical veins (allantois), and cardinal venous system.

    • The cardinal venous system is the origin of the definitive venous system, which includes the cranial vena cava and caudal vena cava.

    • The primitive venous system in the embryo consists of four cardinal veins, which drain from different parts of the body and fuse to form common cardinal veins before entering the heart.

    • The cranial cardinal veins are transformed into the adult internal jugular veins, with the larger external jugular and subclavian veins arising from them.

    • The caudal cardinal veins are temporarily replaced by two new sets of paired veins, the supracardinal and subcardinal veins.

    • The subcardinal veins form most of the caudal vena cava, draining the blood from the embryonic kidneys and gonads.

    • The supracardinal veins develop to drain the dorsal region of the body, forming the azygos veins in the adult.

    • Lymphatic vessels develop from lymph sacs, which arise from developing veins and are derived from mesoderm.

    • The first lymph sacs to appear are the jugular lymph sacs, followed by the retroperitoneal lymph sac, cisterna chyli, and paired caudal lymph sacs.

    • Lymph nodes develop from localised mesodermal invaginations that divide the lumen of the vessels into sinusoids, with the mesoderm then developing a reticular framework and lymphocytes accumulating within.

    • The spleen and haemal nodes (in ruminants) develop in a similar way.

    • The segmental (intersegmental) arteries are branches of the dorsal aorta extending between somites, contributing to visceral and body wall blood supply.

    • The embryonic sinus venosus of the heart receives return blood from different parts: vitelline veins (yolk sac), umbilical veins (allantois), and cardinal venous system.

    • The cardinal venous system is the origin of the definitive venous system, which includes the cranial vena cava and caudal vena cava.

    • The primitive venous system in the embryo consists of four cardinal veins, which drain from different parts of the body and fuse to form common cardinal veins before entering the heart.

    • The cranial cardinal veins are transformed into the adult internal jugular veins, with the larger external jugular and subclavian veins arising from them.

    • The caudal cardinal veins are temporarily replaced by two new sets of paired veins, the supracardinal and subcardinal veins.

    • The subcardinal veins form most of the caudal vena cava, draining the blood from the embryonic kidneys and gonads.

    • The supracardinal veins develop to drain the dorsal region of the body, forming the azygos veins in the adult.

    • Lymphatic vessels develop from lymph sacs, which arise from developing veins and are derived from mesoderm.

    • The first lymph sacs to appear are the jugular lymph sacs, followed by the retroperitoneal lymph sac, cisterna chyli, and paired caudal lymph sacs.

    • Lymph nodes develop from localised mesodermal invaginations that divide the lumen of the vessels into sinusoids, with the mesoderm then developing a reticular framework and lymphocytes accumulating within.

    • The spleen and haemal nodes (in ruminants) develop in a similar way.

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    Description

    Test your knowledge on the role of the allantoic sac and circulation in embryonic development. Understand how the formation of the allantoic stalk is essential for the development of umbilical vessels and placental expansion.

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