2010 Lecture 7
Early Vascular Development
Introduction
Image shows the mouse embryo (19 somite) vascular distribution.
The complexity of septation, cardiac outflow separation, remodelling of the peripheral vasculature, and the pre- to post-natal changes may also contribute to the relatively large proportion of birth defects associated with this system. These events of vascular development are covered in a later lecture. The molecular mechanisms regulating cardiac development are still largely unknown. Development does appear to be an independent mechanism preceding both skeletal and smooth muscle development and using different regulatory mechanisms (not MyoD or myogenin). Lectopia Lecture Audio Lecture objectives
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Development overviewThe heart develops from cardiogenic mesoderm that originally lies above the cranial end of the developing neural tube. Enlargement of the cranial neural fold brings this region ventrally to its correct anatomical position. The original paired cardiac tubes fuse, with the "ventricular" primordia initially lying above the "atria". Growth of the cardiac tube flexes it into an "S-shape" tube, rotating the "ventricles" downward and pushing the "atria" upward. This is then followed by septation, a complex process which converts this simple tube into a four chambered heart and covered in a later lecture and lab. A key part of this process is the separation of cardiac outflow (truncus arteriosus) into a separate pulmonary and aortic arch outflow. During embryonic development there is extensive remodelling of the initially right and left symmetrical cardiovascular system and a contribution from the neural crest to some vessels.
Timecourse
Week 2-3 pair of thin-walled tubes Week 3 tubes fused, truncus arteriosus outflow, heart contracting Week 4 heart tube continues to elongate, curving to form S shape Week 5 Septation starts, atrial and ventricular Septation continues, atrial septa remains open, foramen ovale Week 37-38 At birth pressure difference closes foramen ovale leaving a fossa ovalis Angiogenesis
Blood islands
Blood formation
Red blood cellsThe only cells in the blood are nearly entirely fetal red blood cells. These cells differ from adult red blood cells in:
Early vascular systems
Vitelline blood vessels
Embryo blood vessels
Placental blood vessels
Blood flow through the embryoHigh pressure pathway Stage 13/14 sagittal section. Maternal Blood | -> umbilical vein -> liver -> anastomosis -> sinus venosus -> atria ventricles-> truncus arteriosus -> aortic sac -> aortic arches-> dorsal aorta-> pair of umbilical arteries | Maternal Blood. Low pressure pathway Stage 13
Blood vessel remodelingEarly vascular development is laterally symmetrical (paired left and right). With embryo development this scheme is extensively remodelled leading to an asymmetric adult system in the body. Heart developmentMH - Later development of the heart (septation) will be covered in another lecture. Heart loopingTransverse section- Heart is 2 tubes that fuse in the midline anterior to pharynx. The pericardial cavity can be imagined as the top of the "horseshoe" of the intraembryonic coelom. (where the arms become the pleural cavity and the ends fuse anteriorly to form a single peritoneal cavity). This view shows the initial positioning of the ventricles above the atria. The ventricles are rotated into their correct anatomical position by the growth of the heart tube, bending into an "S" shape. Initially... Cardiac inflow- at the bottom (sinus venosus) Cardiac outflow- at the top (truncus arteriosus)
Heart neural crest
Data from: Chan WY, Cheung CS, Yung KM, Copp AJ. Chan WY, Cheung CS, Yung KM, Copp AJ. Cardiac neural crest of the mouse embryo: axial level of origin, migratory pathway and cell autonomy of the splotch (Sp2H) mutant effect. Development. 2004 Jul;131(14):3367-79. PMID: 15226254 Heart layers
Embryonic heart rate
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Internet LinksEmbryo Images Unit: Embryo Images Online Early Cell Populations (cardiogenic section) | Cardiovascular Development | Week 3 Development | Week 4 Development | Heart Chambers and Outflow Tract | Atrioventricular Septation | Outflow Tract Septation | Ventricular Septation | Atrial Septation | Atrial Walls Aortic Arch Vessels | Changes at Birth ReferencesTextbooks
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TermsFor more cardiovascular term definitions and links to related topics use the glossary. angioblast - the stem cells in blood islands generating endothelial cells which will form the walls of both arteries and veins. (More? Blood Vessel) angiogenesis - the formation of blood vessels also called vasculogenesis in the embryo. anlage (German, anlage = primordium) structure or cells which will form a future more developed or differentiated adult structure. blood islands - earliest sites of blood vessel and blood cell formation, seen mainly on yolk sac chorion. cardinal veins - paired main systemic veins of early embryo, anterior, common, posterior. cardiogenic region - region above prechordal plate in mesoderm where heart tube initially forms. ectoderm - the layer (of the 3 germ cell layers) which form the nervous system from the neural tube and neural crest and also generates the epithelia covering the embryo. endoderm - the layer (of the 3 germ cell layers) which form the epithelial lining of the gastrointestinal tract (GIT) and accessory organs of GIT in the embryo. endocardium - lines the heart. Epithelial tissue lining the inner surface of heart chambers and valves. endothelial cells - single layer of cells closest to lumen that line blood vessels. extraembryonic mesoderm - mesoderm lying outside the trilaminar embryonic disc covering the yolk sac, lining the chorionic sac and forming the connecting stalk. Contributes to placental villi development. haemocytoblasts - stem cells for embryonic blood cell formation. anastomose - to connect or join by a connection (anastomosis) between tubular structures. chorionic villi - the finger-like extensions which are the functional region of the placental barrier and maternal/fetal exchange. Develop from week 2 onward as: primary, secondary, tertiary villi. estrogens - support the maternal endometrium. growth factor - usually a protein or peptide that will bind a cell membrane receptor and then activates an intracellular signaling pathway. The function of the pathway will be to alter the cell directly or indirectly by changing gene expression. (eg VEGF, shh) maternal decidua - region of uterine endometrium where blastocyst implants. undergoes modification following implantation, decidual reaction. maternal sinusoids - placental spaces around chorionic villi that are filled with maternal blood. Closest maternal/fetal exchange site. mesoderm - the middle layer of the 3 germ cell layers of the embryo. Mesoderm outside the embryo and covering the amnion, yolk and chorion sacs is extraembryonic mesoderm. myocardium - muscular wall of the heart. Thickest layer formed by spirally arranged cardiac muscle cells. pericardium - covers the heart. Formed by 3 layers consisting of a fibrous pericardium and a double layered serous pericardium (parietal layer and visceral epicardium layer). pharyngeal arches (=branchial arches, Gk. gill) series of cranial folds that form most structures of the head and neck. Six arches form but only 4 form any structures. Each arch has a pouch, membrane and groove. placenta - (Greek, plakuos = flat cake) refers to the discoid shape of the placenta, embryonic (villous chorion)/maternal organ (decidua basalis) placental veins - paired initially then only left at end of embryonic period, carry oxygenated blood to the embryo (sinus venosus). protein hormone - usually a protein distributed in the blood that binds to membrane receptors on target cells in different tissues. Do not easliy cross placental barrier. sinus venosus - cavity into which all major embryonic paired veins supply (vitelline, placental, cardinal). splanchnic mesoderm - portion of lateral plate mesoderm closest to the endoderm when coelom forms. steroid hormone - lipid soluble hormone that easily crosses membranes to bind receptors in cytoplasm or nucleus of target cells. Hormone+Receptor then binds DNA activating or suppressing gene transcription. Easliy cross placental barrier. syncitiotrophoblast extraembryonic cells of trophoblastic shell surrounding embryo, outside the cytotrophoblast layer, involved with implantation of the blastocyst by eroding extracellular matrix surrounding maternal endometrial cells at site of implantation, also contribute to villi. (dark staining, multinucleated). truncus arteriosus - an embryological heart outflow structure, that forms in early cardiac development and will later divides into the pulmonary artery and aorta. Term is also used clinically to describe the malformation where only one artery arises from the heart and forms the aorta and pulmonary artery. vascular endothelial growth factor - (VEGF) protein growth factor family that stimulates blood vessel growth, a similar factor can be found in the placenta (PIGF). vitelline blood vessels - blood vessels associated with the yolk sac. waste products - products of cellular metabolism and cellular debris, e.g.- urea, uric acid, bilirubin.
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Course Content 2009Embryology Introduction | Cell Division/Fertilization | Cell Division/Fertilization | Week 1&2 Development | Week 3 Development | Lab 2 | Mesoderm Development | Ectoderm, Early Neural, Neural Crest | Lab 3 | Early Vascular Development | Placenta | Lab 4 | Endoderm, Early Gastrointestinal | Respiratory Development | Lab 5 | Head Development | Neural Crest Development | Lab 6 | Musculoskeletal Development | Limb Development | Lab 7 | Kidney | Genital | Lab 8 | Sensory - Ear | Integumentary | Lab 9 | Sensory - Eye | Endocrine | Lab 10 | Late Vascular Development | Fetal | Lab 11 | Birth, Postnatal | Revision | Lab 12 | Lecture Audio | Course Timetable Cite this page: Hill, M.A. (2024, June 14) Embryology 2010 Lecture 7. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/2010_Lecture_7
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