Human Embryology 1 Anhui Medical University Development of the Circulatory System Dr. Lijie Feng Department of Histology and Embryology School of Basic Medical science School of International Education Anhui Medical University 2 Anhui Medical University Development process of an embryo zygote blastocyst implantation amnion amnion cavity amnion body stalk umbilical body stalk cord blastoderm umbilical cord amnion yolk sac chorion yolk sac exocoelom chorion 20 weeks 4 weeks 3 weeks Question: How embryos receive oxygen and nutrients? 3 Anhui Medical University Maternal blood diffusion Circulatory system development 4 Anhui Medical University Content Establishment of the primordial cardiovascular system * Development of the heart Fetal blood circulation and changes in the circulation after birth Congenital defects of the cardiovascular system 5 Anhui Medical University Content Establishment of the primordial cardiovascular system Development of the heart Fetal blood circulation and changes in the circulation after birth Congenital defects of the cardiovascular system 6 Anhui Medical University Establishment of the primordial cardiovascular system Period: in the 3rd-7th weeks of embryonic development Origin: mesoderm Significance: provide nutrition and oxygen and remove wastes and carbon dioxide 7 Anhui Medical University Establishment of the promordial cardiovasular system 1) Extra-embryonic blood vessels The 15th day, mesenchymal cells in the wall of yolk sac proliferate to form isolated cell clusters ----blood islands body stalk amnion cavity ectoderm endoderm Primordial heart Yolk sac extra embryonic mesoderm Blood islands 8 Anhui Medical University Establishment of the promordial cardiovasular system Peripheral cells endothelial cells endothelial tube Central cells primitive blood cells (blood stem cell) Endothelial tube approach and fuse with each other to form an endothelial tube network Mesenchymal cell endothelial cell primitive blood cell 9 Anhui Medical University Establishment of the promordial cardiovasular system • Endothelial tube network appears in chorionic membrane and body stalk, and connect to vitelline circulation. villi amnion cavity amnion Blood vessel Primordial heart Allantois body stalk Yolk sac chorionic membrane Blood islands Blood vessel 10 Anhui Medical University Establishment of the promordial cardiovasular system 2) Intra-embryonic blood vessels The 18-20th days, blood island appears in the mesenchyma of intraembryonic splanchnic mesoderm to form intraembryonic endothelial tube network By the end of 3rd week, intraembryonic and extra- embryonic endothelial tube networks connect to each other to form primitive cardiovascular system Blood circulation begins at the end of 4nd week 11 Anhui Medical University Formation and variation of blood islands D15, mesenchymal cells D18-20 intraembryonic in the wall of yolk sac mesenchymal cells Blood island Central cells Peripheral cells Primitive blood cells Endothelial cells Blood cells Endothelial tube Primitive cardiovascular Endothelial tube network system (later of 3rd weeks) 12 Anhui Medical University Establishment of the primordial cardiovasular system Mesenchyme near the endothelial tube differentiate into smooth muscles and CT, form the vascular medial and adventitia, evolve into artery and vein. 13 Anhui Medical University 3) Components of the primordial cardiovascular system Primitive cardiovascular system include: - Cardiac tubes - Artery - Vein 14 Model of primitive cardiovascular system (4th weeks) Anhui Medical University 3) Components of the primordial cardiovascular system Cardiac tube: paired, fuse into a single cardiac tube at the 4th week. Cardiac tube Cardiac tube Primitive heart d20 Early of 4w Later of 4w 15 Anhui Medical University 3) Components of the primordial cardiovascular system Arteries At the end of 3rd weeks Paired, the head end connect to cardiac tube Composition: -- Abdominal aorta artery -- Dorsal aorta -- Aortic arch Cardiac tube d20 16 Anhui Medical University 3) Components of the primordial cardiovascular system Arteries Abdominal aorta: paired, the head end connect to cardiac tube, fused to form an aortic sac. Abdominal aorta Abdominal aorta Abdominal aorta d20 Early of 4w Later of 4w 17 Anhui Medical University 3) Components of the primordial cardiovascular system Arteries Abdominal aorta: paired, the head end connect to cardiac tube, fused to form a aortic sac Dorsal aorta: paired, fused to form a single vessel at the 4th week - vitelline artery: several paired, supply the yolk sac - umbilical artery: paired, allantoic artery, supply chorionic membrane Dorsal aorta Dorsal aorta Dorsal aorta umbilical artery Umbilical artery Vitelline artery vitelline artery d20 Early of 4w Later of 4w 18 Anhui Medical University 3) Components of the primordial cardiovascular system Arteries Abdominal aorta: paired, the head end connect to cardiac tube, fused to form a aortic sac Dorsal aorta: paired, fused to form a single vessel at the 4th week Aortic arch: 6 pairs, connect dorsal aorta to aortic sac Aortic arch Aortic arch d20 Early of 4w Later of 4w 19 Anhui Medical University 3) Components of the primordial cardiovascular system Veins: Anterior cardinal vein: paired, from upper part of the body Posterior cardinal vein : paired, from lower part of the body --- common cardinal vein sinus venosus (cardiac tube) anterior cardinal vein posterior cardinal vein d20 4 weeks 20 Anhui Medical University 3) Components of the primordial cardiovascular system Veins: - common cardinal vein - vitelline vein : paired, from yolk sac sinus venosus - umbilical vein : paired, from chorionic membrane 21 Anhui Medical University 3) Components of the primordial cardiovascular system Three sets of blood circulation existed at the end of 3rd week Embryonic circulation Umbilical circulation Vitelline circulation 22 Model of primitive cardiovascular system (4th weeks) Anhui Medical University Content Establishment of the promordial cardiovasular system * Development of the heart Fetal blood circulation and changes in the circulation after birth Congenital defects of the cardiovasular system 23 Anhui Medical University Development of the heart -- Formation of primitive heart -- Establishing of the heart shape -- Partitioning of the heart 24 Anhui Medical University Development of the heart 1. Formation of primitive heart 2. Establishing of the heart shape 3. Partitioning of the heart 25 Anhui Medical University 1) Formation of primitive heart The heart arises from cardiogenic area, which located in mesoderm situated cephalic of oropharyngeal membrane brain amnion oropharyngeal membrane body stalk Yolk sac Allantois cloacal membrane cardiogenic area oropharyngeal membrane Cardiogenic area oropharyngeal membrane 26 1) Formation of primitive heart Anhui Medical University Pericardiac coelom: space in cardiogenic area D18-19 Cardiogenic plate: mesodermal cells ventral to the pericardiac coelom aggregate and form two longitudinal, paired cell cords. pericardiac coelom Cardiogenic plate oropharyngeal membrane d19 27 Anhui Medical University 1) Formation of primitive heart D20 Cardiac tubes: The cardiogenic plate become canalized to form two cardiac tubes. pericardiac coelom cardiac tube 28 1) Formation of primitive heart Anhui Medical University Cephalic fold of the embryo pulls the cardiac tube and pericardiac coelom forward and located in ventral of pharynx notochord d20 head Tail folds folds cardiac tube d22 pericardiac coelom 29 Anhui Medical University 1) Formation of primitive heart Cephalic folds of the embryo pulls the cardiac tube and pericardiac coelom forward and located in ventral of pharynx Cardiac tube pericardiac coelom d28 30 1) Formation of primitive heart Anhui Medical University Lateral folds of the embryo make the two cardiac tubes close together, then fused into a single layer in the midline. neural groove dorsal aorta amnion yolk sac pericardiac coelom pericardiac cardiac tube d19 coelom Cardiogenic d20 plate dorsal mesocardium neural tube foregut pericardial cavity cardiac tube d21 d22 31 Anhui Medical University 1) Formation of primitive heart Dorsal mesocardium: cardiac tube invaginate into pericardiac coelom and connect to it by dorsal mesocardium Pericardiac coelom turns into the pericardial cavity dorsal mesocardium neural tube dorsal foregut mesocardium pericardial cavity cardiac tube cardiac tube pericardiac coelom d22 32 1) Formation of primitive heart Anhui Medical University Mesenchyme adjacent to endothelium of cardiac tube proliferate and differentiate into subendothelium of endocardium, myocardium and epicardium. The wall of heart is formed section truncus artiriosus foregut Transverse sinus venous sinus cardiac wall atrium pericardial cavity thoracic wall D28 Lateral view D28 transection 33 Anhui Medical University Development of the heart 1. Formation of primitive heart 2. Establishing of the heart shape 3. Partitioning of the heart 34 Anhui Medical University 2) Formation of the heart shape Single cardiac tube connected caudally to the vein; cephalically connected to the artery, two ends fixed with pericardial cavity. D21 truncus artiriosus artery end Transverse sinus Fused cardiac tube venous sinus atrium pericardial cavity Unfused cardiac tube D28 Lateral view transversum Vein end 35 Anhui Medical University 2) Formation of the heart shape Three dilatations: Two constriction: bulbus cordis bulboventricular sulcus ventricle atrioventricular groove atrium Truncus arteriosus