Development of Heart

Development of Heart. Dr. Mrs. R. Niranjan Department of Anatomy University of Jaffna.

Object i ves. To understand the Establishment of the cardiogenic field Development of primitive heart tube Division and position of the primitive heart Formation of the cardiac loop and its clinical correlates Formation of the coverings of heart Development of the sinus venosus.

Development of the cardiovascular system. Angioblasts arise from: Mesoderm Mesenchyme Angioblast cells g ive rise to blood and blood vessels  Heart begins to function by end of the 3 rd week - in order to meet the nutrient needs of rapidly growing embryo.

ESTABLISHMENT OF THE. 4. CARDIOGENIC FIELD. 9/9/2021.

Establishment of cardiogenic area. Vascular system appears in the middle of 3 rd week Cardiac progenitor cells lie – immediately lateral to primitive streak in the ectoderm. Cranial segments of heart-outflow tract – migrates first followed by caudal portions (ventricles and sinus venosus ) of heart.

Establishment of cardiogenic area. Cardiac progenitor cells travel to the cranial aspect and located rostral to the buccopharyngeal membrane and neural folds They settled in the splanchnic layer of lateral plate mesoderm Induced by underlying endoderm – forms the cardiac myoblasts.

Formation of horse shoe shaped – cardiac tubes. Cardiac Swelling en docardal h.

Establishment of cardiac tubes, myoblast and pericardial cavity.

Establishment of other blood vessels. In addition to the cardiogenic region Blood islands also appear bilaterally, parallel and close to the midline of the embryonic shield. These islands form a pair of longitudinal vessels - dorsal aortae Blood islands also forms the vessels like Arteries Arterioles Capillaries Venules Veins.

Development of primitive heart. Starts as two thin walled endocardial tubes It is the caudal continuation of the first aortic arches Endocardial heart tube - begins to fuse to form a single tube As heart tube fuses Surrounding mesenchyme thickens to form Myocardium Epicardium.

FORMATION AND POSITION OF THE HEART TUBE.  The 2 processes are responsible for final position of the heart Folding of the embryo in a cephalocaudal direction Simultaneous folding laterally.

Effects of cephalocaudal fold - change in the position of primitive heart tube.

Shift of heart tube to different regions. Initially – cardiogenic area in front of buccopharyngeal membrane and neural plate Result of growth of brain and cephalocaudal folding of embryo – Shift to cervical region and finally settled at thoracic region.

Results of lateral folding of embryo. Caudal region merge – except most caudal parts Cranial crescent part of heart tube – outflow tract Primitive heart tube – becomes lined by inner endothelium and outer myocardium Receives – venous drainage at its caudal end and Begins to pump blood at its cranial end.

Effects of lateral fold – fusion of heart tubes. 15.

Invagination of heart tube into pericardial cavity.

Further development of primitive heart tube. Due to differential growth of the heart tube Tubular heart elongates and Develop the dilations or sacculations Thus it is divided into Bulbus cordis , Ventricle Atrium Sinus venosus.

Bulbus cordis. It is a narrow structure except the region for future right ventricle – which forms the trabeculated right ventricle It is divided into Truncus arteriosus - forms the root and proximal portion of aorta and pulmonary trunk Conus cordis – outflow trunk Proximal 1/3 rd of the right ventri cle.

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Formation of cardiac loop.  Steps: Elongation- Primitive heart with different dilatations/sacculation -elongate Bending of cephalic portion Shifting of caudal portion Cardiac loop formation.

Bulbus cordis. Bulbus cordis moves inferiorly, anteriorly and to right.

Primitive ventricle. It moves to the embryo’s left side.

The primitive atrium and sinus venosus. 23. 9/9/2021.

Sinus venosus. Veins opening into horns of sinus venosus- Three pairs of veins Vitelline veins- from yolk sac. Umbilical veins- from placenta. Common cardinal veins-from body of embryo.

Primitive heart –cardiac loop formation 23-28 day.

Primitive heart. 26. Primordia (S  I) (Cranially  Caudally) Truncus  Continuous cranially with first pair of aortic arches Ventricle Both bulbus cordis and ventricle grows faster than other parts which causes S shape bend Sinus Receives venous return from  Umbilical, Vitelline & Common cardinal veins.

Primitive heart –cardiac loop formation 23-28 day.

Finally heart is enclosed in the pericardium. 28.

Primitive heart –cardiac loop formation 23-28 day.

Abnormalities of cardiac looping. Dextrocardia It is a condition in which the heart lies on the right side of the thorax instead of the left It is caused because the heart loops to the left instead of the right . Dextrocardia may coincides with situs inversus.

Formation of coverings of the heart. Developing heart surrounded by splanchnic mesoderm-forms myocardium and visceral epicardium Somatic – parietal layer.

Formation of pericardial sinuses of the heart. 32.

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34. Development of sinus venosus. 9/9/2021. Dr.Mrs. Romini Niranjan.

Development of sinus venosus. Sinus venosus is the most caudal of the primitive heart chambers. 4 th week: it receives blood from the right and left sinus horns . Each sinus horn receives blood from three sets of veins. Anterior and posterior cardinal veins via the common cardinal vein Umbilical vein Vitelline vein.

Venous system. Vitelline veins Umbilical veins Cardinal veins.

Development of sinus venosus. Cephalically, the sinus venosus is in continuity with the primitive common atrium . The communication between the them through the sinuatrial junction. At first this communication between the sinus venous and atrium is wide. Folding and enlargement of the heart shift the junction cephalically and to the right (4 th -5 th week of development)..

Development of sinus venosus. 38. 9/9/2021. Dr.Mrs. Romini Niranjan.

Development of sinus venosus. 39. From 5 th week onwards, the following veins are obliterated: Right umbilical Left vitelline Left common cardinal vein obliterated at 10 th week.

Development of the sinus venosus. 40. 10 th week left common cardinal vein obliterates.

Development of the venous valves. Right sinus horn incorporated into right atrium Its entrance is – sinoatrial orifice , is flanked on each side by valvular fold (right and left valvular folds) Dorsocranially valves fused and formed the septum spurium.

Valve formation. Left venous valve fuses with the developing atrial septum. Right venous valve- Superior portion disappears entirely. Inferior portion –develops into valves of IVC and coronary sinus Crista terminalis is a dividing line between the original atrium and senous venosus portion.

Thank you. 43. 9/9/2021. Dr.Mrs. Romini Niranjan.