Development of blood vessels

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Questions and Answers

What is angiogenesis primarily responsible for?

Formation of new vessels from existing ones (correct)

Formation of blood from mesenchymal cells

Formation of major blood vessels from scratch

Development of the heart

Which growth factor is primarily involved in the processes of vasculogenesis and angiogenesis?

Transforming growth factor (TGF-b)

Vascular endothelial growth factor (VEGF) (correct)

Platelet-derived growth factor (PDGF)

Fibroblast growth factor (FGF)

What do the dorsal aorta and pharyngeal arch arteries primarily give rise to?

Major vessels of the lower limbs

Arteries of the gastrointestinal tract

Arteries of the head and neck region (correct)

Arteries supplying the kidneys

The first arteries to appear in a developing embryo are known as:

Primitive aortae Signup and view all the answers

After the fusion of the two primitive heart tubes, what do the ventral aortae form?

Aortic sac Signup and view all the answers

How are the aortic arch arteries distributed?

In craniocaudal order as the arches develop Signup and view all the answers

What happens to the fifth aortic arch artery during development?

It degenerates or does not form a vessel Signup and view all the answers

What structure does the arch connecting the ventral and dorsal aortae lie within?

The first pharyngeal arch Signup and view all the answers

What is the oxygen saturation in umbilical arteries before reaching the placenta?

58% Signup and view all the answers

Which physiological change helps to close the ductus arteriosus at birth?

Contraction of smooth muscles in the ductus arteriosus wall Signup and view all the answers

What is one of the effects of lung expansion immediately after birth?

Increased flow to the lungs Signup and view all the answers

The closure of which structure is directly influenced by the increase in left atrial pressure?

Foramen ovale Signup and view all the answers

Which fold of the internal surface of the anterior abdominal wall is unpaired?

Median umbilical fold Signup and view all the answers

What is the process of vasculogenesis primarily responsible for?

Formation of new blood vessels from angioblasts Signup and view all the answers

How are hemangioblasts related to blood vessel formation?

They are precursors to endothelial cells Signup and view all the answers

Which structure is modified during lateral folding of the developing heart?

Dorsal aorta Signup and view all the answers

What is the significance of the right-left blood shunt during fetal development?

It directs blood away from the liver Signup and view all the answers

What component of the heart tube is crucial for the formation of the ventricles?

Atrioventricular canals Signup and view all the answers

Which of the following statements correctly describes the truncus arteriosus?

It separates into the aorta and pulmonary trunk Signup and view all the answers

Which type of veins are formed from the sinus venosus?

Umbilical, vitelline, and cardinal veins Signup and view all the answers

What does cardiac looping refer to in heart development?

The process by which the heart assumes its final form Signup and view all the answers

Which part of the embryonic cardiovascular system is associated with the primitive atria?

Membranous ventricular septum Signup and view all the answers

What is angiogenesis?

The formation of blood vessels from existing vessels Signup and view all the answers

Which arteries develop from the dorsolateral branches of the primitive dorsal aorta?

Arteries of the upper and lower limbs Signup and view all the answers

What is the primary role of umbilical veins in the developing embryo?

Carrying well-oxygenated blood from the placenta Signup and view all the answers

Which major primitive veins return poorly oxygenated blood from the body of the embryo?

Common cardinal veins Signup and view all the answers

What do the lateral splanchnic branches from the primitive dorsal aorta form?

Phrenic and renal vessels Signup and view all the answers

During which week of intrauterine life do the major primitive veins appear?

5th week Signup and view all the answers

What do vitelline veins primarily drain?

Oxygenated blood from the yolk sac Signup and view all the answers

Which veins are primarily responsible for draining the cranial half of the embryo?

Anterior cardinal veins Signup and view all the answers

Which set of branches from the primitive dorsal aorta forms the vitelline and umbilical arteries?

Ventral splanchnic branches Signup and view all the answers

What structures join to form the common cardinal veins?

Anterior and posterior cardinal veins Signup and view all the answers

What type of veins drain the yolk sac?

Visceral veins Signup and view all the answers

What is the primary source of oxygen for the fetus?

The placenta Signup and view all the answers

What occurs in the fetal lungs during development?

They are collapsed Signup and view all the answers

Which structure serves as a shunt between the umbilical vein and the inferior vena cava?

Ductus venosus Signup and view all the answers

How is oxygenated blood transported from the placenta to the fetus?

Through the umbilical vein Signup and view all the answers

Which statement about fetal circulation is true?

Fetal shunts help maintain oxygen concentration for vital organs. Signup and view all the answers

What role does the Foramen ovale play in fetal circulation?

It shunts blood from the right atrium to the left atrium. Signup and view all the answers

What is the approximate Po2 of blood in the umbilical vein?

30 mm Hg Signup and view all the answers

What does the ductus arteriosus connect?

Pulmonary trunk and aorta Signup and view all the answers

What is the function of the umbilical arteries in fetal circulation?

Carry deoxygenated blood back to the placenta Signup and view all the answers

What does the term 'portal circulation' refer to in fetal circulation?

The pathway is of little significance Signup and view all the answers

What physiological change initiates the closure of the foramen ovale at birth?

Increase in left atrial pressure Signup and view all the answers

What causes the closure of the ductus arteriosus after birth?

Increased oxygen tension and release of bradykinin Signup and view all the answers

Which fold of the anterior abdominal wall is formed by the medial umbilical ligament?

Medial umbilical fold Signup and view all the answers

What is the oxygen saturation typically found in the umbilical arteries?

58% Signup and view all the answers

Which statement accurately describes a circulatory change occurring at birth?

Reduction of right atrial pressure facilitates shunt closure Signup and view all the answers

What does vasculogenesis primarily involve in the formation of new blood vessels?

The assembly of specialized mesenchymal cells Signup and view all the answers

What is a critical change in the fetal circulatory system at birth?

Expansion of pulmonary circulation Signup and view all the answers

How does lateral folding affect blood vessel development?

It modifies the structure of the heart tube and associated vessels Signup and view all the answers

What role do umbilical veins play during fetal development?

Deliver oxygenated blood from the placenta to the fetus Signup and view all the answers

Which of the following structures retains its functional role in fetal circulation after birth?

Pulmonary veins Signup and view all the answers

Which statement best describes cardiac looping during heart development?

The heart tube bends and twists to form the definitive heart Signup and view all the answers

What is the primary function of the right-left shunt in the fetal circulatory system?

To bypass the pulmonary circulation Signup and view all the answers

Which statement accurately describes the formation of the sinus venosus?

It receives blood from umbilical and vitelline veins Signup and view all the answers

What happens to the majority of the first and second arch arteries during development?

They completely disappear. Signup and view all the answers

What does the truncus arteriosus give rise to during development?

The aortic arch and pulmonary arteries Signup and view all the answers

Which branch from the primitive dorsal aorta is responsible for forming the arteries of the upper and lower limbs?

Dorsolateral branches Signup and view all the answers

Which vessel primarily drains the cranial portion of the embryo?

Cardinal vein Signup and view all the answers

The umbilical veins in a developing embryo carry what type of blood?

Well-oxygenated blood from the placenta. Signup and view all the answers

What structures unite to form the common cardinal veins in the developing embryo?

Anterior and posterior cardinal veins Signup and view all the answers

What type of veins drain the yolk sac in the developing embryo?

Vitelline veins Signup and view all the answers

During which week of intrauterine life do three pairs of major primitive veins first appear?

5th week Signup and view all the answers

Which vessels can be classified under lateral splanchnic branches of the primitive dorsal aorta?

Phrenic, suprarenal, renal, and gonadal vessels Signup and view all the answers

Which of the following veins is primarily responsible for draining the caudal half of the embryo?

Posterior cardinal veins Signup and view all the answers

What forms the ventral splanchnic branches of the primitive dorsal aorta?

Visceral organ vessels Signup and view all the answers

What function do the common cardinal veins serve in the developing embryo?

Return poorly oxygenated blood from the embryo's body Signup and view all the answers

What is the primary function of the ductus venosus in fetal circulation?

To bypass the liver Signup and view all the answers

In fetal circulation, which structure allows blood to bypass the pulmonary circulation?

Ductus arteriosus Signup and view all the answers

What is the approximate oxygen saturation of blood in the umbilical vein?

80% Signup and view all the answers

How is deoxygenated blood returned from the fetus to the placenta?

Via the umbilical arteries Signup and view all the answers

What mechanism is primarily responsible for maintaining high oxygen concentration for fetal organs?

Fetal shunts in the circulatory system Signup and view all the answers

Which of the following factors significantly increases the resistance to blood flow through the fetal lungs?

Collapsed status of the lungs Signup and view all the answers

Which structure connects the right and left atria in the fetal heart?

Foramen ovale Signup and view all the answers

Why is portal circulation considered of little significance during fetal life?

Fetal blood is primarily oxygenated by the placenta Signup and view all the answers

What occurs to the lungs of the fetus before birth?

They remain collapsed Signup and view all the answers

What role does the umbilical vein play in fetal circulation?

Delivers oxygenated blood to the fetus Signup and view all the answers

What are the two main sources from which the arteries of the body develop?

Pharyngeal arch arteries and dorsal aorta Signup and view all the answers

What components make up the primitive aorta in a developing embryo?

Two parts: the dorsal and ventral aorta Signup and view all the answers

During which weeks of development do the pharyngeal arches and their arteries primarily develop?

4th and 5th weeks Signup and view all the answers

How many pairs of aortic arch arteries are typically formed during development?

Six pairs Signup and view all the answers

What primarily differentiates the fifth aortic arch artery during its development?

It develops but never forms a vessel. Signup and view all the answers

Which vessel is indicated as a major contributor to the formation of head and neck arteries?

Aortic arches Signup and view all the answers

What is the relationship between the aortic sac and the pharyngeal arch arteries?

Each pharyngeal arch is supplied by an artery from the aortic sac. Signup and view all the answers

What defines the vascular system development process known as angiogenesis?

Formation of new vessels by budding and branching from preexisting vessels Signup and view all the answers

Study Notes

Angiogenesis and Vasculogenesis

Angiogenesis: formation of new blood vessels from preexisting ones through budding and branching.
Vasculogenesis: formation of major blood vessels through the assembly of angioblasts derived from mesoderm.

Development of the Arterial System

Arteries arise from two primary sources: pharyngeal arch arteries and dorsal aorta.
Aortic arches supply arteries to the head and neck; dorsal aorta supplies the rest of the body.

Pharyngeal Arch Arteries

The first arteries to appear are the primitive aortae, originally continuous with primitive heart tubes.
Primitive aorta consists of:
- Ventral aorta (ventral to foregut).
- Dorsal aorta (dorsal to the gut).
- Arched portion connecting both (forms the first aortic arch).

Development of Aortic Arch Arteries

Six pairs of aortic arch arteries develop sequentially from the aortic sac, corresponding to the pharyngeal arches.
The fifth arch is either absent or becomes obliterated.
Aortic sac contributes a branch to each newly developing aortic arch.

Formation of Major Blood Vessels

Blood vessels originate from mesenchymal cells influenced by angiogenic factors like VEGF.
Dorsal aorta branches into:
- Dorsolateral branches for limbs and intercostal arteries.
- Lateral splanchnic branches for various organs (phrenic, renal, gonadal).
- Ventral splanchnic branches for vitelline and umbilical arteries.

Development of the Venous System

Major primitive veins (vitelline, umbilical, common cardinal) appear around the 5th week of gestation.
Common cardinal veins are formed by anterior and posterior cardinal veins uniting.
Visceral veins include:
- Vitelline veins (from yolk sac).
- Umbilical veins (from placenta).
Somatic veins consist of anterior and posterior cardinal veins.

Fetal Circulation

Fetal blood is oxygenated by the placenta, not the lungs.
Lungs remain collapsed in utero, leading to higher resistance to blood flow.
Maternal and fetal blood do not mix directly; a placental barrier facilitates nutrient exchange.

Fetal Shunts

Ductus venosus: shunts blood from umbilical vein to inferior vena cava, bypassing the liver.
Foramen ovale: allows blood flow between the right and left atria, bypassing pulmonary circulation.
Ductus arteriosus: connects pulmonary trunk to descending aorta, also bypassing the lungs.

Circulatory Changes at Birth

Post-birth, shunts close due to shifts in pressure and oxygen tension.
Umbilical vein and ductus venosus closure reduces flow to the right atrium.
Lung expansion reduces pulmonary resistance, increasing blood flow to the lungs.
Closure of foramen ovale occurs due to increased left atrial pressure.

Anatomical Folds of the Anterior Abdominal Wall

Median umbilical fold: formed by the median umbilical ligament (urachus remnant).
Medial umbilical folds: paired, formed by medial umbilical ligaments.
Lateral umbilical folds: paired, formed by the inferior epigastric vessels.

Summary of Learning Outcomes

Understand sequential formation of blood vessels and various systemic changes in embryonic development.
Explain the significance of fetal and postnatal circulation and anatomical changes at birth.