Development of the Heart

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Questions and Answers

Which condition primarily leads to cyanosis due to the shunting of deoxygenated blood into systemic circulation?

Atrial septal defect (ASD)

Ventricular septal defect (VSD)

Tetralogy of Fallot (correct)

Patent ductus arteriosus (PDA)

What is a common symptom associated with acyanotic congenital heart defects?

Failure to thrive (correct)

Clubbing of the nails

Cyanosis of the lips

Pale gray or blue skin color

What is the primary mechanism of left-to-right shunts in acyanotic congenital heart defects?

Obstruction of blood flow from the heart

Excessive blood flow to the lungs (correct)

Decreased pressure in the right atrium

Blocking the outflow of oxygenated blood

Which congenital defect is NOT classified as acyanotic?

Total anomalous pulmonary venous return Signup and view all the answers

Which condition can result from right ventricular pressure overload from a left-to-right shunt?

Right sided heart hypertrophy Signup and view all the answers

From which part of the embryo does the heart develop?

Mesoderm Signup and view all the answers

What significant event occurs on the 21-22nd day during heart development?

The primitive heart starts beating Signup and view all the answers

Which structure is the arterial end of the heart tube?

Truncus arteriosus Signup and view all the answers

What type of cells induce vasculogenesis in the primary heart field?

Endodermal cells Signup and view all the answers

What happens to the two endothelial heart tubes during the 3rd week of embryonic development?

They fuse to form a single heart tube Signup and view all the answers

Which of the following correctly lists the five dilatations of the heart tube from cranial to caudal end?

Truncus arteriosus, Bulbus cordis, Primitive ventricle, Primitive atrium, Sinus venosus Signup and view all the answers

What does the unfused part of the sinus venosus form in the heart tube?

Two horns that receive veins Signup and view all the answers

Which type of mesoderm is responsible for forming the myocardium and epicardium surrounding the primitive heart tube?

Splanchnic mesoderm Signup and view all the answers

What is the name of the gap between the lower edge of septum primum and septum intermedium during the formation of the interatrial septum?

Foramen primum Signup and view all the answers

Which structure forms the upper part of the interatrial septum?

Septum secundum Signup and view all the answers

What physiological change occurs that leads to the closure of the foramen ovale after birth?

Pressure in the left atrium increases Signup and view all the answers

What structure is formed as the upper part of the septum primum breaks down during interatrial septum formation?

Foramen secundum Signup and view all the answers

How does the foramen ovale function in the heart before birth?

It allows communication between the right and left atria Signup and view all the answers

At what stage of fetal development does the septum primum begin to develop?

End of the fourth week Signup and view all the answers

What happens to the foramen ovale after birth as the left atrium receives blood from the lungs?

It closes due to increased pressure in the left atrium Signup and view all the answers

What anatomical feature represents the lower edge of the septum secundum in adults?

Fossa ovalis Signup and view all the answers

Which of the following statements is true regarding the formation of the interatrial septum?

Both septum primum and septum secundum arise from the same location in the heart Signup and view all the answers

What is the role of septum primum during fetal development?

It partially separates the two atria allowing for fetal circulation Signup and view all the answers

What structure is responsible for the formation of the atrioventricular septum?

Endocardial cushions Signup and view all the answers

Which condition results from a defect in cardiac looping?

Kartagener syndrome Signup and view all the answers

What happens to the bulboventricular sulcus during heart development?

It disappears to allow fusion of the bulbus cordis and ventricle. Signup and view all the answers

Which of the following is NOT a septum that partitions the primitive heart tube?

Muscular septum Signup and view all the answers

Where does the primitive atrium lie in relation to the truncus arteriosus?

Dorsal to truncus arteriosus Signup and view all the answers

Which rare condition is characterized by the heart lying exposed on the surface of the thorax?

Ectopia cordis Signup and view all the answers

What is the primary function of the interatrial septum?

Divide the primitive atrium into right and left atria Signup and view all the answers

What happens to the primitive heart tube as it develops into the adult heart?

Its lumen partitions into four distinct chambers. Signup and view all the answers

At what stage of development do the endocardial cushions appear to form the atrioventricular septum?

About 28 days Signup and view all the answers

Which of the following describes dextrocardia?

The heart is located on the right side of the chest. Signup and view all the answers

At what week does the formation of the interventricular septum typically begin?

Week 4 Signup and view all the answers

How many parts compose the interventricular septum?

3 parts Signup and view all the answers

What is the correct order of development for the aorticopulmonary septum?

Neural crest and endocardial cells migrate, then form truncal and bulbar ridges Signup and view all the answers

What effect does the fusion of truncal and bulbar ridges have on the ventricular outflow tract?

It rotates 180° to separate the aorta and pulmonary trunk Signup and view all the answers

Which of the following is NOT a type of valvular anomaly?

Coronary Signup and view all the answers

What can congenital heart defects (CHDs) lead to?

Pathological connections between heart chambers Signup and view all the answers

What is the formation of the interventricular septum characterized by?

Complete closure by week 8 without shunting Signup and view all the answers

What is a potential outcome of the disruption of normal cardiac morphogenesis?

Congenital heart defects Signup and view all the answers

Which part of the interventricular septum is NOT one of its components?

Septal part Signup and view all the answers

Which of the following not correctly describe a potential state of valvular anomalies?

Hyperplastic Signup and view all the answers

What parts make up the interventricular septum?

Muscular part, bulbar part, membranous part Signup and view all the answers

During which week does the formation of the aorticopulmonary septum typically begin?

Week 4 Signup and view all the answers

What outcome may occur due to Congenital Heart Defects (CHDs)?

Pathological connections between heart chambers Signup and view all the answers

Which cells are involved in the formation of the aorticopulmonary septum?

Neural crest and endocardial cells Signup and view all the answers

What is a characteristic of the interventricular septum's development compared to the atrial septation process?

It is completed without shunting between the ventricles Signup and view all the answers

What establishes the initial attachment of the heart tube within the pericardial cavity?

Dorsal mesocardium Signup and view all the answers

How does the heart tube relate to the pericardial cavity after the formation of the head fold?

It rotates and lies cranial to the septum transversum. Signup and view all the answers

What happens to the cardiac jelly as development progresses?

It is replaced by the myocardium. Signup and view all the answers

Which embryonic layer contributes to the formation of the endothelial heart tube?

Splanchnopleuric mesoderm Signup and view all the answers

What structure forms after the mesocardium connecting the bulboventricular loop disappears?

Transverse sinus Signup and view all the answers

During heart tube formation, what is the role of the myoepicardial mantle?

To invest the front and sides of the heart tube Signup and view all the answers

What embryological structure gives rise to the visceral layer of the pericardium?

Myoepicardial mantle Signup and view all the answers

Which structure is formed from the proliferation of the splanchnopleuric mesoderm on the dorsal aspect of the pericardial cavity?

Myoepicardial mantle Signup and view all the answers

Which of the following describes the heart tube's shape during the formation of the bulboventricular loop?

U-shaped Signup and view all the answers

What was the initial origin of all components of the cardiovascular system (CVS)?

Mesoderm Signup and view all the answers

At what time does the development of the separate blood vascular system begin?

Beginning of the third week Signup and view all the answers

What is a key modification that occurs in lateral folding during heart development?

Modification of the developing heart tube Signup and view all the answers

What does the right-left blood shunt primarily indicate in fetal circulation?

Normal fetal gas exchange process Signup and view all the answers

Which of the following components is involved in the development of the heart tube?

Hemangioblasts Signup and view all the answers

What aspect of the primitive ventricles is important to understand in their clinical correlations?

Their modification from primitive structures Signup and view all the answers

What is the primary function of the endocardial cushions during heart development?

To separate the atrioventricular canal into right and left channels Signup and view all the answers

What structural feature is formed by the fusion of the truncus arteriosus and bulbar ridges?

Aorticopulmonary septum Signup and view all the answers

In which week does the separation of the atrioventricular septum occur in embryonic development?

At the end of the 4th week Signup and view all the answers

What condition is a result of a defect in cardiac looping?

Dextrocardia Signup and view all the answers

Which of the following is NOT a normal process during the development of the cardiovascular system?

Atrial septal defect closing Signup and view all the answers

What anatomical position does the primitive atrium occupy in relation to the truncus arteriosus?

Dorsal to the truncus arteriosus Signup and view all the answers

What leads to the formation of the septum intermedium in the heart?

Merging of the endocardial cushions Signup and view all the answers

What happens to the bulboventricular sulcus during heart development?

It disappears as bulbus cordis and ventricle fuse Signup and view all the answers

What is a characteristic of ectopia cordis?

The heart lies exposed on the thoracic surface Signup and view all the answers

What is the role of microtubules and dynein arms in cardiac development?

Involved in cardiac looping Signup and view all the answers

What major event occurs with the formation of the interatrial septum?

It separates the primitive atrium into right and left atria Signup and view all the answers

What is the fate of the primitive heart tube as it develops?

It forms the mature heart with multiple chambers Signup and view all the answers

What is the foramen that is formed by the breakdown of the upper part of the septum primum as it fuses with the AV septum?

Foramen secundum Signup and view all the answers

Which septum primarily forms the lower part of the interatrial septum?

Septum primum Signup and view all the answers

How does the foramen ovale function in the fetal heart?

Facilitates blood flow from the LA to the RA Signup and view all the answers

What occurs physiologically to close the foramen ovale after birth?

Increased pressure in the LA Signup and view all the answers

Which embryonic structure grows downward toward the septum intermedium and overlaps the foramen secundum?

Septum secundum Signup and view all the answers

What is the gap between the lower edge of septum primum and septum intermedium called during fetal development?

Foramen primum Signup and view all the answers

What anatomical feature represents the remnants of septum primum and septum secundum in adults?

Fossa ovalis Signup and view all the answers

During the formation of the interatrial septum, when does the septum primum start developing?

At the end of the 4th week Signup and view all the answers

What key event promotes the physiological closure of the foramen ovale after birth?

Increased oxygenation of blood Signup and view all the answers

What is the main function of the interatrial septum during fetal development?

Allows shunting of blood between atria Signup and view all the answers

Study Notes

Development of the Heart

The heart originates from a primitive heart tube derived from mesenchyme in the embryo's cardiogenic area.
The primitive heart tube forms the endocardium, while surrounding splanchnic mesoderm differentiates into myocardium and epicardium.
Initial heartbeat occurs around the 21st to 22nd day of embryonic development, with blood circulation starting by the 24th day.

Establishment of the Cardiogenic Area

Cardiac progenitor cells emerge cranial to the primitive streak in the 3rd week of development.
These cells migrate to form a horseshoe-shaped primitive heart field in the splanchnopleuric mesoderm by the end of the 3rd week.
Endoderm of the primitive pharynx induces vasculogenesis in the primary heart field through the secretion of vascular endothelial growth factor (VEGF).

Formation of the Heart Tube

Small vessels coalesce to form two endothelial heart tubes that later fuse into a single heart tube.
The heart tube has a bifurcated structure, with a cranial (arterial) end and a caudal (venous) end.
The heart tube differentiates into five dilations from cranial to caudal: truncus arteriosus, bulbus cordis, primitive ventricle, primitive atrium, and sinus venosus.

Arterial and Venous Ends of the Heart Tube

The truncus arteriosus connects to the aortic sac, leading to the first pharyngeal arch artery and dorsal aorta.
The venous end, or unfused sinus venosus, forms two horns which assist in receiving blood through three veins from the body wall.

Acquisition of Adult Heart Form

Formation of an S-shaped cardiac loop occurs as the primitive atrium and sinus venosus shift position in the pericardial cavity relative to the primitive ventricle.
Bulbus cordis and the primitive ventricle are initially separated by a sulcus which later disappears, resulting in a single chamber.
The expansion of the primitive atrium leads to the development of auricles that project forward from the truncus arteriosus.

Clinical Correlations

Cardiac looping defects can lead to Kartagener syndrome, characterized by situs inversus and dextrocardia.
Ectopia cordis is a rare condition where the heart is exposed on the thoracic surface due to nonunion of the sternal plates.

Formation of Heart Chambers

The single lumen of the primitive heart tube partitions into four definitive chambers via four septa: atrioventricular septum, interatrial septum, interventricular septum, and aorticopulmonary septum.

Atrioventricular Septum Formation

Endocardial cushions arise from mesenchyme in the canal walls and fuse to create the atrioventricular septum around the 28th day of development.

Interatrial Septum Formation

The interatrial septum separates the right and left atria and is formed by septum primum and septum secundum.
Septum primum develops from the primitive atrium and grows towards the atrioventricular septum, creating the foramen primum.
As septum primum fuses with the atrioventricular septum, the foramen secundum forms, facilitating communication between right and left atria through the foramen ovale.

Physiological Closure of Foramen Ovale

The foramen ovale usually closes within the first year of life when pressure in the left atrium surpasses that in the right atrium, pushing the septum primum against the septum secundum.

Interventricular Septum Formation

Development of the interventricular septum begins by the 4th week and is completed by the end of the 7th week.
It consists of muscular, bulbar, and membranous parts, each evolving from different origins.

Aorticopulmonary Septum Formation

Neural crest and endocardial cells form truncal and bulbar ridges that spiral and fuse to create the aorticopulmonary septum, dividing the outflow tract into the aorta and pulmonary trunk.

Congenital Heart Defects

Congenital heart defects (CHDs) arise from abnormal cardiac morphogenesis, leading to shunts between heart chambers.
Shunt types include left-to-right (causing pulmonary hypertension) and right-to-left (causing cyanosis).

Acyanotic and Cyanotic Heart Defects

Acyanotic defects include conditions like ventricular septal defect (VSD) and atrial septal defect (ASD), characterized by left-to-right shunts.
Cyanotic defects involve right-to-left shunting, typically manifesting as “blue baby” syndrome with symptoms like feeding problems and exertional dyspnea.

Learning Outcomes

Understand the formation of hemangioblasts and blood islands.
Explain similarities between heart tubes, dorsal aorta, and vitelline veins.
Grasp how lateral folding affects developing cardiovascular structures.
Identify components and derivatives of the heart tube.
Describe cardiac looping and its clinical implications.
Explain development and modification of atrioventricular canals.
Analyze septation and modification of primitive atria and ventricles.

Overview of Cardiovascular Development

Cardiovascular system (CVS) development initiates in the 3rd week of embryogenesis.
All CVS components are derived from mesoderm.
Key developmental processes include the formation of the heart and major blood vessels: umbilical and vitelline veins.

Positioning and Structure of Heart Tube

Heart tube initially positioned caudal to the septum transversum and rotates 180° after head fold formation.
Heart tube and pericardial cavity lie ventral to the foregut after rotation.
Dorsal mesocardium connects the heart tube to the pericardial cavity but disintegrates, anchoring the heart tube at pericardial margins.

Formation of Cardiac Wall

Endothelial heart tube originates from splanchnopleuric mesoderm and becomes the endocardium.
Myoepicardial mantle forms myocardium, surrounded by cardiac jelly, which is replaced by the developing myocardium.
Visceral pericardium arises from myoepicardial mantle; somatopleuric mesoderm gives rise to the parietal layer of pericardium.

Acquisition of Adult Heart Form

Bulboventricular loop formation involves ventral growth of bulbus cordis and primitive ventricle.
Transverse sinus develops from the breakdown of mesocardium connecting various segments of the heart.
S-loop development results from positioning of the atrium and sinus venosus relative to the primitive ventricle.

Clinical Correlations

Cartagener syndrome is linked to defects in cardiac looping, causing situs inversus and dextrocardia.
Ectopia cordis occurs from failure of sternal plates to unite, leading to exposed heart and high neonatal mortality.

Development of Heart Chambers

Primitive heart tube's single lumen partitions into four chambers: atrioventricular, interatrial, interventricular, and aorticopulmonary septa.
Atrioventricular septum forms through the fusion of endocardial cushions, dividing it into right and left canals.

Interatrial Septum Formation

Formed by the septum primum and septum secundum, developing from the primitive atrium.
The foramen primum and foramen secundum are critical gaps during formation.
The foramen ovale, a significant feature, allows temporary blood flow between atria.

Physiological Closure of Foramen Ovale

Typically closes within 6 months to 1 year post-birth as left atrial pressure exceeds that of the right atrium, pushing septum primum against septum secundum.

Interventricular Septum Formation

Development starts in week 4, completed by week 7; differs from atrial septation as it does not allow shunting.
Comprised of muscular, bulbar, and membranous parts, each from distinct developmental origins.

Aorticopulmonary Septum Development

Formed by migrating neural crest and endocardial cells, which create truncal and bulbar ridges that spiral and fuse.
This division establishes distinct pathways for the aorta and pulmonary trunk.

Valve Formation and Clinical Correlations

Valvular anomalies can present as stenosis, regurgitation, or complete atresia (e.g., tricuspid atresia).
Congenital heart defects (CHDs) arise from disruptions in normal cardiac morphogenesis, causing abnormal circulatory connections.

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Description

Explore the intricate processes involved in the development of the heart from its initial formation to the establishment of the cardiogenic area. This quiz covers key concepts such as the primitive heart tube, cardiac progenitor cells, and the formation of the heart tube in embryonic development.