Development of Heart & CVS (KSAUHS COM 2020) PDF

Dr. ABDULRAHMAN ALRADDADI Assistant Professor of Human Anatomy BMS-COM-KSAUHS Development of Heart & CVS Dr. ABDULRAHMAN ALRADDADI Office N: 1.CM.2.311 Email: [email protected] Office Ext: 95280 Lecture Objectives By the end of the lecture the students should be able to: • Describe the mai...

Dr. ABDULRAHMAN ALRADDADI Assistant Professor of Human Anatomy BMS-COM-KSAUHS Development of Heart & CVS Dr. ABDULRAHMAN ALRADDADI Office N: 1.CM.2.311 Email: [email protected] Office Ext: 95280 Lecture Objectives By the end of the lecture the students should be able to: • Describe the main features of heart development to the fourchambered system. • Describe the development of the pericardium. • Describe the development of primary and secondary atrial septa and the ventricular septum. • Explain the changes occurring in the bulbis cordis and truncus arteriosus in its transformation from a single to a double tube. • Describe the development of the aortic arches on the right and left sides from the fetus to the adult. • Describe the development of arteries and veins. • Describe the developmental aberrations responsible for the following malformations: patent ductus arteriosus (P.D.A.); atrial septal defects (A.S.D.) and ventricular septal defects (V.S.D.); tetralogy of Fallot and transposition of the great vessels. References 1. Langman's Medical Embryology, 14th edition (2018), International Edition by T.W. Sadler: Chapter 12: Cardiovascular System. Pages: 165 - 200 2. The Developing Human, 10th Edition (2015) By Keith L. Moore, T.V.N. (Vid) Persaud, and Mark G. Torchia: Chapter 13: Cardiovascular System. Pages: 283 – 335 *** THIS PRESENTATION WAS PREPARED FOR LECTURING PURPOSES. THE ONLY OFFICIAL REFERENCE FOR THIS SESSION IS THE ASSIGNED REFERENCES, AS MENTIONED IN THE BLOCK BOOK. 1/9/2023 Dr. A Alraddadi 4 Lecture Outline I. Introduction II. Early Development III. The Formation of the Cardiac Loop IV. Septation of the Heart V. Vascular Development VI. Circulatory Changes at Birth VII. Congenital Malformations I. Introduction Introduction Phases of Embryonic Development I. Embryonic Period • Week 1 to week 8 • 1st 2 weeks (Blastocyst)  Cell proliferation (zygote > morula > blastocyst) • Weeks 3 to 8 (Main embryonic period)  Gastrulation, folding of the embryo, formation of organ systems II. Fetal Period • Week 9 to week 38 1/9/2023 DR. A ALRADDADI 7 Introduction Early Development • Bilaminar germ disc: • End of the 2nd week • Epiblast & Hypoblast • Gastrulation: • Week 3 • Trilaminar germ layers: • Ectoderm, mesoderm (paraxial, intermediate, lateral), endoderm • Notochord Formation • By day 18 • Induces ectoderm to form Neural plate: Neural tube → CNS • Neural crest cells → PNS 1/9/2023 DR. A ALRADDADI 8 Introduction • Begin early in gestation during the 3rd week • Cardiogenic Plate at the cranial part of the trilaminar disc • Primitive Blood Vessels → Two Endocardial Tubes → Single Endocardial Tube = Primitive Heart Tube → Cardiac Loop → 4 Primordial Heart Chambers • The inflow and outflow tracts = the systemic and pulmonary circulations • By the end of the 8th week the fetal heart has formed • Blood circulation: fetal life Vs postnatal life Development of the human heart during the first eight weeks (top), and the formation of the heart chambers (bottom). In this figure, the blue and red colors represent blood inflow and outflow (not venous and arterial blood). Initially, all venous blood flows from the tail/atria to the ventricles/head, a very different pattern from that of an adult. https://en.wikipedia.org/wiki/Heart_development II. Early Development Early Development • Cardiac progenitor cells begin to form in the middle of the 3rd week in the epiblast layer, lateral to the primitive streak • These cells migrate through the primitive streak to an area that is rostral to the buccopharyngeal membrane in the splanchnic mesoderm. • The underlying endoderm induces these cells to differentiate into: 1. Blood Islands: consists of precursor blood cells and angioblasts 2. Myoblasts: will develop into the myocardium Early Development • The cells are arranged in a horseshoe-shaped structure called the cardiogenic plate • It consists of two laterally placed endocardial tubes surrounded by myoblasts and is thus referred to as the primordium of the heart Early Development • As the neural tube grows and closes, the primordium of the heart will shift position from rostral to the buccopharyngeal membrane to the thoracic region Early Development • The two endocardial tubes fuse to form the primitive heat tube with an endothelial lining and myocardial layer • As the primitive heart tube is forming, angiogenic cells appear on both sides, close to the midline and will develop into the paired dorsal aortae Early Development • At their cephalic end, the paired dorsal aortae bend around the developing embryo and are attached to the cephalic end of the primitive heart tube forming the aortic arches • Six pairs of aortic arches will develop sequentially Early Development • The primitive heart tube shifts its position into the pericardial cavity which is formed by the intraembryonic cavity • The primitive heart tube is held in position by the dorsal mesocardium which will disappear leaving a space called the transverse pericardial sinus • The primitive heart tube remains suspended at its two ends • The blood begins to flow from its caudal to its cranial end Early Development • The myocardium thickens and secretes an extracellular matrix called the cardiac jelly • Around the myocardium, an outer layer develops called the epicardium • Hence, the primitive heart tube has three layers: 1. Endocardium: the innermost lining of the heart 2. Myocardium: the middle layer, which contains muscle cells 3. Epicardium: the outer lining (or visceral pericardium) Early Development The primitive heart tube consists of 4 subdivisions. From caudal to cranial the subdivisions are: 1. Sinus Venosus 2. Primitive Atrium 3. Primitive Ventricle 4. Bulbus Cordis Early Development 1. Sinus Venosus: paired structures which receives three sets of veins: 1. Umbilical Veins: from the placenta 2. Vitelline Veins: from the yolk sac 3. Cardinal Veins: from the body of embryo 2. Primitive Atrium: a single structure continuous with the sinus venosus 3. Primitive Ventricle: will become the left ventricle - That part of the endocardial tube between the atrium and ventricle is the atrioventricular canal 4. Bulbus Cordis: 1. 2. 3. Caudal 1/3: will become the trabeculated part of the right ventricle Middle 1/3: will become the conus cordis which will form the outflow tracts of both ventricles Cranial 1/3: will become the truncus arteriosus, which is continuous with the aortic arches and will form the roots and first part of the: a. Aorta b. Pulmonary trunk Early Development • The first heartbeat occurs at 22 days and originates in the myocardium, forming peristalsis-like waves beginning in the sinus venosus. • By the end of week 4 coordinated contractions of the heart results in unidirectional blood flow: Blood enters the sinus venous (from the vitelline, cardinal and umbilical veins) → the primitive atrium → the primitive ventricle → the bulbus cordis → the aortic sac → the aortic arches → the dorsal aortae for distributions to the embryo, yolk sac and placenta III. The Formation of the Cardiac Loop The Formation of the Cardiac Loop • As the primitive heart elongates and grows rapidly, bends and forms the cardiac loop, which is finished by day 28. • The loop is formed by the differential growth of the ends: 1. The cranial end grows ventrally and to the right 2. The caudal end grows dorsally and to the left • At the end of loop formation, the venous and arterial ends are brought together as in adults. The Formation of the Cardiac Loop Sinus Venosus Derivatives 1. Left Horn → the coronary sinus and oblique vein of the left atrium. 2. Right Horn → the smooth part of the right atrium (sinus venarum) • The muscular part of the right atrium (the auricle) is derived from the primitive atrium • The two portions are separated by the crista terminalis The Formation of the Cardiac Loop Sinus Vensous Derivatives 3. The opening between the sinus venosus and right atrium, called the sinoatrial orifice, develops into: 3. Right venous valve → Valve of inferior vena cava & Valve of coronary sinus 4. Left venous valve: becomes part of the septum secundum 4. The venous valves fuse dorsocranially and form ridge called the septum spurium. The Formation of the Cardiac Loop Sinus Vensous Derivatives 5. The primitive atrium on left side sprouts a pulmonary vein, which branches and: a. Grows towards the developing lungs b. The trunk of the pulmonary vein is incorporated into atrium and will become the smooth wall of the left atrium while the portion derived from the left side of the primitive atrium retains a trabeculated appearance as the left auricle. IV. Septation of the Heart Septation of the Heart • During the beginning of the separation of the pulmonary and systemic circulations, a continuous communication between left and right sides is maintained to: 1. Permit blood to flow directly from the right atrium to the left atrium 2. Bypass the nonfunctioning lungs • Septation of the heart include: A. Formation of the atrioventricular canal B. Septation of the atrium C. Separation of the Ventricles D. Formation of the outflow tracts Septation of the Heart Atrioventricular Septation • Formation of the atrioventricular canal between the atrium and ventricle • Endocardial cushions: ‐ 4 areas of expanded matrix production ‐ between the endocardium & myocardium. ‐ form in conotruncal region • At week 5, they approach each other and fuse, dividing the atrioventricular canal into right and left canals Septation of the Heart Septation of the atrium The Septum Primum ‐ Grows toward the endocardial cushions ‐ Leaving a large temporary opening: the ostium primum ‐ Fuses with the endocardial cushions: closing the ostium primum ‐ The upper part of the septum undergo cell death: the ostium secundum The Septum Secundum ‐ Appears on the right of the septum primum ‐ Grows downward to cover the foramen secundum ‐ Does NOT fuse with the endocardial cushions: foramen ovale Foramen Ovale ‐ Permits blood flow from Rt atrium to Lf atrium ‐ Opposite flow is prevented by the flap valve (septum primum) ‐ After birth, ↑ pressure in the left atrium causing → closing the foamen ovale = solid wall separating the right and left atria ‐ The site of the foramen ovale becomes the fossa ovalis Septation of the Heart Separation of the Ventricles • By the interventricular septum: ‐ A crescent-shaped fold (muscular tissue + endocardial tissue) ‐ The interventricular foramen: initially at it’s cranially end • Consists of two components: 1. A membranous part: endocardial tissue 2. A muscular part: muscular tissue • After closure: ‐ The right ventricle communicates with pulmonary trunk ‐ The left ventricle with the aorta Septation of the Heart Formation of the Outflow Tracts • Partitioned by endocardial cushion into pulmonary and aortic trunks: ‐ Two spiral mesodermal ridges → spiral aorticopulmonary septum (conotruncal septum) ‐ Neural crest cells: contribute in septum ‐ The caudal ends → the membranous part of the interventricular septum ‐ The cranial ends → the semilunar valves • As the aorticopulmonary septum formed: ‐ blood from the right ventricle flows into the pulmonary trunk ‐ blood from the left ventricle flows into the aorta V. Vascular Development Vascular Development • In the middle of week 3, blood islands (mesoderm origin)are found in the following areas: 1. Body of the embryo 2. Chorion 3. Connecting stalk • Within each blood island the peripherally located cells flatten and give rise to the endothelial cells: the walls of arteries and veins • These cells join together to form angioblasts: vascular plexuses throughout the embryo. Vascular Development • Three separate circulations will soon be interconnected: 1. Vitelline circulation: develops in the wall of the yolk sac 2. Chorionic circulation: gives rise to umbilical vessels delivering blood to and from the placenta 3. Intra-embryonic circulation: circulates blood through the body of the developing embryo Vascular Development Derivatives of the Aortic Arch Arteries • Six pairs of aortic arch arteries: 1. 1ST pair → maxillary arteries 2. 2nd pair → the hyoid and stapedial arteries 3. 3rd pair→ the common carotids and roots of internal carotids 4. 4th pair → contributes to subclavian and left to arch of aorta 5. 5th pair → completely disappears. 6. 6th pair→ the proximal part of the pulmonary arteries. The left 6th arch also forms the ductus arteriosus Vascular Development Vascular Development • Fate of the paired dorsal aortae, vitelline and umbilical arteries: 1. Dorsal aortae → the descending aorta (the suprarenal gland, the gonads, and the kidneys) 2. Vitelline arteries → form arteries in the dorsal mesentery that supply the gut (the celiac, superior and inferior mesenteric arteries) 3. Umbilical arteries → the internal iliac arteries and medial umbilical ligaments Vascular Development Three paired veins drain into the heart at 4 weeks: 1. Vitelline veins: ‐ Drain the yolk sac ‐ The left vitelline vein disappears ‐ The right vitelline vein develops into the hepatic portion of the inferior vena cava, the portal vein and the superior mesenteric vein 2. Umbilical veins: ‐ Bring oxygenated blood from placenta ‐ The right umbilical vein disappears ‐ The left connects the placenta to the inferior vena cava via the ductus venosus Vascular Development 3. Common cardinal veins: ‐ Drain the head and neck and body wall of the embryo ‐ The cardinal veins consist of: a. Anterior cardinal veins: ‐ Drain blood from head and neck region ‐ The cranial portion → cerebral veins, intracranial dural sinuses and internal jugular veins ‐ The cervical portions → the left and right brachiocephalic veins ‐ The right anterior cardinal vein and the right common cardinal vein → the superior vena cave Vascular Development 3. Common cardinal veins: b. Posterior cardinal veins: ‐ Drain the lower body and receives the following veins: i. Subcardinal veins: ‐ Drain the kidneys, gonads and suprarenal glands ‐ The right subcardinal vein → the renal segment (between liver and kidney) of the inferior vena cava ii. Supracardinal veins: ‐ Appear lateral to sympathetic trunk ‐ In thoracic region→ azygos and hemiazygos veins ‐ In pelvic region → the pelvic segment (below kidneys) of inferior vena cava. iii. Sacrocardinal veins → lower part of inferior vena cava and continue as common iliac veins Vascular Development The inferior vena cava develops from: 1. Right vitelline vein 2. Right subcardinal vein 3. Supracardinal veins 4. Sacrocardinal vein VI. Circulatory Changes at Birth Circulatory Changes at Birth Fetal Circulation • Oxygenated blood from the placenta: umbilical vein → ductus venosum → inferior vena cava → the right atrium (mixing deoxygenated and oxygenated blood): a. b. Most oxygenated blood → the foramen ovale → the left atrium → left ventricle → aorta → the fetal body Most deoxygenated blood → the right ventricle → the pulmonary trunk → the ductus arteriosus → aorta (bypassing the nonfunctioning lungs) • Blood is returned to the placenta for oxygenation via the umbilical arteries Circulatory Changes at Birth Postnatal Circulation Changes: • The ductus venosus → the ligamentum venosum. • The umbilical arteries → the medial umbilical ligaments. • The umbilical vein → the ligamentum teres hepatis. • The ductus arteriosus → the ligamentum arteriosum → increased pressure in the left atrium → closes the foramen ovale Blood flow: • Deoxygenated blood from the right atrium → the right ventricle → the pulmonary trunk and arteries → the lungs (the pulmonary circulation) • Oxygenated blood from the lungs → the pulmonary veins → the left atrium → the left ventricle → aorta → to the body (the systemic circulation) VII. Congenital Malformations Congenital Malformations Patent Ductus Arteriosus (PDA) • Females > males • Aortic blood shunted into pulmonary a. • Primary cause is failure of contraction of the muscular wall • Associated with: ‐ Maternal rubella infection ‐ Premature infants ‐ Other cardiac defects • Treated by surgical closure Congenital Malformations Aterial Septal Defects (ASD) • Females > males Patent Foramen Ovale • Failure of adhesion between the flap and septum secondum after birth • Most common ASD • 25% of people • Mostly clinically insignificant • Some cases blood shunted to left causing cyanosis Congenital Malformations Aterial Septal Defects (ASD) Endocardial Cushion Defect with primum type ASD • Deficiency of endocardial cushions • Failure of septum primum to fuse with cushions • Patent foramen primum Common atrium • Rare defect • Interatrial septum is absent • Failure of septum primum and secondum to develop Congenital Malformations Ventricular Septal Defects (VSD) • Males > Females • Most common cardiac defects (25%) Membranous Septal Defect • Most common VSD • Failure of the membranous septum to develop • Results in ↑ pulmonary blood flow → pulmonary hypertention → dyspnea & cardiac failure Muscular Septal Defect • Less common • Defects in the muscular septum Complete Absence of The Septum • Extremely rare • Failure of the septum to develop (single ventricle or common ventricle) • Die at infancy or early adulthood Congenital Malformations Tetralogy of Fallot 1. Pulmonary stenosis 2. VSD 3. Dextroposition of aorta (overriding aorta) 4. Right ventricular hypertrophy • Pulmonary trunk is usually small • Cyanosis appear later on The Development Of Cardiovascular System https://www.youtube.com/watch?v=-0N76gycPvo&index=6&list=PLerPQAYf2bNtt9SfyUiIoH4D-QlV15Am&t=41s 1/9/2023 Dr. A ALRADDADI 51 Thank you 1/9/2023 Dr. A Alraddadi 52 Assess your Knowledge 1/9/2023 DR. A ALRADDADI 53 Development of the Heart 1) Cardiac precursor cells form from which layer? a) Hypoblast b) Ectoderm c) Epiblast d) Notocord e) Endoderm Development of the Heart 2) The transverse pericardial sinus forms from the breaking away of? a) Somites b) Notocord c) Axial Mesentary d) Dorsal Mesentary e) Ectoderm Development of the Heart 3) On what day does the heart start to beat? a) 22 b) 24 c) 26 d) 28 e) 30 Development of the Heart 4) What structure does the proximal third of the bulbus cordis become? a) Right Ventricle b) Left Ventricle c) Ventricular Outflow Tracts d) Aorta & Pulmonary Artery e) Left & Right Atria Development of the Heart 5) What structure does the middle third (conus cordis) of the bulbus cordis become? a) Right Ventricle b) Left Ventricle c) Ventricular Outflow Tracts d) Aorta & Pulmonary Artery e) Left & Right Atria Development of the Heart 6) What structure does the distal third (truncus arteriosus) of the bulbus cordis become? a) Right Ventricle b) Left Ventricle c) Ventricular Outflow Tracts d) Aorta & Pulmonary Artery e) Left & Right Atria Development of the Heart 7) What major structure is formed by the sinus venosus? a) Aorta b) Left Ventricle c) Right Ventricle d) Left Atrium e) Right Atrium Development of the Heart 8) Where is the ostium primum formed? a) Between Right and Left Ventricles b) Between Right and Left Atria c) Between Right Atrium and Ventricle d) Between Left Atrium and Ventricle e) Within the Coronary Sinus Development of the Heart 9) What is the correct order of cardiac conduction? a) AV node to SA node to His bundle to Purkinje fibers b) Purkinje fibers to His bundle to SA node to AV node c) SA node to AV node to His bundle to Purkinje fibers d) Purkinje fibers to His bundle to AV node to SA node e) Bachman’s bundle to SA node to AV node to ventricles Development of the Heart 10) Which of the following is NOT associated with an Atrial Septal Defect? a) Persistent ostium secundum b) Endocardial cushion defect c) Sinus venosum defect d) Probe patency e) Transposition of the Great Vessels Development of the Heart 11) What defect is necessary to survive with pulmonary atresia? a) Atrial sepal defect b) Aortic valve stenosis c) Undeveloped coronary sinus d) Left bundle branch block e) Right bundle branch block Development of the Heart 12) Which of the following is NOT associated with Tetralogy of Fallot? a) Pulmonary stenosis b) Pulmonary atresia c) Ventricular septal defect d) Right ventricular hypertrophy e) Dextroposition of the Aorta (over riding aorta) Development of the Vascular System 13) All arteries, veins, and lymphatic channels form from ____. a) Ectoderm b) Mesoderm c) Endoderm d) Chorion e) Villi Development of the Vascular System 14) During what weeks of development do the pharyngeal/branchial arches form? a) 2nd to 3rd b) 3rd to 4th c) 4th to 5th d) 5th to 6th e) 6th to 7th Development of the Vascular System 15) Which aortic arches are important for the abdomen and thorax? a) I, II, III b) I, II, III, IV, V c) V only d) IV, VI e) I, II, IV Development of the Vascular System 16) Which nerve is associated with the aortic arches IV and VI? a) V – Trigeminal Nerve b) VI – Abducent Nerve c) IX – Glossopharyngeal Nerve d) X – Vagus Nerve e) XI –Accessory Nerve Development of the Vascular System 17) Aortic arch IV forms the ____ on the right side of the embryo and the ____ on the left. a) Right subclavian artery; Arch of aorta b) Ductus arteriosus; Pulmonary Artery c) Arch of aorta; Pulmonary Artery d) Ductus arteriosus; Right subclavian artery e) Arch of aorta; Ductus arteriosus Development of the Vascular System 18) What tissue do the vitelline arteries supply? a) Ectoderm b) Mesoderm c) Endoderm d) Aortic e) Pulmonic Development of the Vascular System 19) At birth, a child’s skin appears much less pink than would be expected. The physician determines that the child’s ductus arteriosus did not close. The child has a blue tint because the ductus arteriosus is shunting blood from the ____ to the ____. a) Right Atrium; Left Atrium b) Pulmonary Artery; Aorta c) Right Ventricle; Left Ventricle d) Inferior Vena Cava; Right Atrium e) Descending Aorta; Umbilical Arteries Development of the Vascular System 20) In utero, the ductus venosus helps shunt blood away from the very first organ it reaches to more important organs like the brain. This shunt bypasses the ____. a) Lungs b) Aorta c) Spleen d) Pancreas e) Liver Development of the Vascular System 21) During fetal life, in which of the following structures is the percent hemoglobin/oxygen saturation level of fetal blood the lowest? a) Right Atrium b) Inferior Vena Cava c) Umbilical Vein d) Ductus Arteriosus e) Descending Aorta Development of the Vascular System 22) During week six (lymphatic vessel development), the dilated lymph sac that forms at the lower end of the thoracic duct is called the ____. a) Lymphocitic Sac b) Iliac Lymph Sac c) Retroperitoneal Lymph Sac d) Jugular Lymph Sac e) Cisterna Chyli Development of the Vascular System 23) What cardinal vein is responsible for draining the body wall? a) Subcardinal b) Cacrocardinal c) Supracardinal d) Dorsal cardinal e) Ventral cardinal Development of the Vascular System 24) Which of the following structure gives rise to the coronary sinus? a) Right horn of sinus venosus b) Left horn of sinus venosus c) Right common cardinal vein d) Left common cardinal vein Answers 1. C 2. D 3. A 4. A 5. C 6. D 7. E 8. B 9. C 10. E 11. A 12. B 13. B 14. C 15. D 16. D 17. A 18. C 19. B 20. E 21. A 22. E 23. C 24. B