2010 Lecture 21

From Embryology



In lecture 7 - Early Vascular Development, the early development of the cardiovascular system was discussed. This second lecture will now focus on the extensive remodeling that occurs in both the heart and vascular system during later development. In addition, there will be discussion on the major cardiovascular abnormalities. The laboratory this week will also give you the opportunity to work through some of these concepts using a new online teaching module.

Dr Nalini Pather - Lecture 21 - Printable version

This material is also presented in an online Cardiac Embryology tutorial.


Cardiovascular Links: cardiovascular | Heart Tutorial | Lecture - Early Vascular | Lecture - Heart | Movies | 2016 Cardiac Review | heart | coronary circulation | heart valve | heart rate | Circulation | blood | blood vessel | blood vessel histology | heart histology | Lymphatic | ductus venosus | spleen | Stage 22 | cardiovascular abnormalities | OMIM | 2012 ECHO Meeting | Category:Cardiovascular
Historic Embryology - Cardiovascular 
1902 Vena cava inferior | 1905 Brain Blood Vessels | 1909 Cervical Veins | 1909 Dorsal aorta and umbilical veins | 1912 Heart | 1912 Human Heart | 1914 Earliest Blood-Vessels | 1915 Congenital Cardiac Disease | 1915 Dura Venous Sinuses | 1916 Blood cell origin | 1916 Pars Membranacea Septi | 1919 Lower Limb Arteries | 1921 Human Brain Vascular | 1921 Spleen | 1922 Aortic-Arch System | 1922 Pig Forelimb Arteries | 1922 Chicken Pulmonary | 1923 Head Subcutaneous Plexus | 1923 Ductus Venosus | 1925 Venous Development | 1927 Stage 11 Heart | 1928 Heart Blood Flow | 1935 Aorta | 1935 Venous valves | 1938 Pars Membranacea Septi | 1938 Foramen Ovale | 1939 Atrio-Ventricular Valves | 1940 Vena cava inferior | 1940 Early Hematopoiesis | 1941 Blood Formation | 1942 Truncus and Conus Partitioning | Ziegler Heart Models | 1951 Heart Movie | 1954 Week 9 Heart | 1957 Cranial venous system | 1959 Brain Arterial Anastomoses | Historic Embryology Papers | 2012 ECHO Meeting | 2016 Cardiac Review | Historic Disclaimer

Lecture Objectives

  • 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 major cardiovascular developmental abnormalities.

Textbook references

  • Human Embryology (3rd ed.) Larson Chapter 7 p151-188 Heart, Chapter 8 p189-228 Vasculature
  • The Developing Human: Clinically Oriented Embryology (6th ed.) Chapter 14: p304-349

Other textbooks

  • Before we Are Born (5th ed.) Moore and Persaud Chapter 12; p241-254
  • Essentials of Human Embryology Larson Chapter 7 p97-122 Heart, Chapter 8 p123-146 Vasculature
  • Human Embryology Fitzgerald and Fitzgerald Chapter 13-17: p77-111

Recent reviews

  • Yutzey KE, Kirby ML. Wherefore heart thou? Embryonic origins of cardiogenic mesoderm. Dev Dyn. 2002 Mar;223(3):307-20. Review. PMID: 11891982
  • Three-dimensional reconstruction of gene expression patterns during cardiac development. Soufan AT, Ruijter JM, van den Hoff MJ, de Boer PA, Hagoort J, Moorman AF. Physiol Genomics. 2003 May 13;13(3):187-95. Review. PMID: 12746463
  • Moorman A, Webb S, Brown NA, Lamers W, Anderson RH. Development of the heart: (1) formation of the cardiac chambers and arterial trunks. Heart. 2003 Jul;89(7):806-14. PMID: 12807866
  • Bruneau BG. Transcriptional regulation of vertebrate cardiac morphogenesis. Circ Res. 2002 Mar 22;90(5):509-19. Review. PMID: 11909814

Heart Development

Day 14 Heart tube

Early Human Heart Tube Development

  • endocardial tube in pericardial cavity
    • dorsal mesentry (mesocardial) attachment lost
    • attached at cranial (arterial) and caudal (venous) ends
  • tube elongation - bending and series of expansions

Bulbus Cordis

  • refers to the outflow tract in early embryo
  • 3 parts
Adult Heart blood flow
Fetal Structure Adult Structure
Truncus arteriosus aorta

pulmonary trunk

Conus arteriosus right ventricle - smooth part
Primitive ventricle right ventricle - trabecular part

left ventricle - trabecular part

Primitive atrium right atrium - trabecular part

left atrium - trabecular part

Sinus venosus right atrium - smooth part (sinus venarum)

coronary sinus oblique vein of left atrium

Heart Layers

  • 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).
  • myocardium - muscular wall of the heart, thickest layer formed by spirally arranged cardiac muscle cells.
  • endocardium - lines the heart, epithelial (endothelial) tissue lining the inner surface of heart chambers and valves.

Embryonic Heart Rate

  • Stage 9-10 2 mm embryo (gestational sac diameter of 20 mm) EHR at least 75 beats / minute
  • Stage 11-12 5 mm embryo (gestational sac diameter of 30 mm) EHR at least 100 beats / minute
  • Stage 16 10 mm embryo EHR at least 120 beats / minute
  • Stage 18 15 mm embryo EHR at least 130 beats / minute

Week 12 fetal heart rate doppler Week 17 fetal heart rate audio

Separation of the Atria from the Venticles

Separation of the atrioventricular canal

Endocardial Cushions

  • form initial division of atria and ventricles
  • form on dorsal and ventral wall of atrioventcular canals
  • grow into canal - meet and fuse to separate atrioventricular canal into right and left channels
  • anterior and posterior cushions fuse; lateral cushions remain unfused

Atrial Septation

Heart1 atrium icon.jpg

Heart (Carnegie stage 13)

Through all development blood shunts from right to left atrium (bypass lungs)

Septum Primum

Stage 13 Septum Primum Stage 22 Septum Primum

  • dorso-cranial wall, crescentric-shaped membranous extension
  • grows downward towards endocardial cushions
  • opening is foramen primum (ostium primum)- serves as a shunt
  • a series of perforations develop in cranial end - coalesce to form foramen secundum (ostium secundum)
  • septum primum fuses with endocardial cushions - obliterates foramen primum

Septum Secundum

  • crescentric septum secundum begins to form to the right of septum primum
  • grows as septum primum downwards, does not fuse with endocardial cushion, opening is foramen ovale
  • arrangement of the two septa facilitates a one-way valve

Atrial septation Early -atrial and ventricular septation Late-atrial and ventricular septation

Right Atrium

sinus venosus and tributaries
  • with heart looping and formation of interatrial septa, the sinus venosus shifts completely to right atrium
  • right sinus horn incorporates into dorsal wall of right atrium
  • left sinus horn becomes the coronary sinus
  • sinoatrial opening - has 2 flaps, left fuses with septum secundum, right forms valve to inferior vena cava and coronary sinus. Stage 13 - right venous valve Stage 22 - right venous valve

Left Atrium

  • posterior wall - outgrowth forms single pulmonary vein, divided into 4 branches
  • incorporation into the wall leads to 4 openings in posterior wall
  • later moves to the right aligns with atrioventricular canal.

Ventricular Septation

Heart (Carnegie stage 13)
Ventricular septum

Heart1 realign icon.jpg

  • 2 separate components - superior membranous, inferior muscular

Muscular Septum

muscular septum

  • growth of inferior wall
  • fusion of 3 components - right and left bulbar ridges and dorsal endocardial cushion

Membranous Septum

  • above the muscular septum, fusion continuous with septation of the outflow tract


Outflow Tract Septation

Heart1 ventricle icon.jpg

  • in early development, outflow tract is a single tube, bulbus cordis
  • elongates to form proximal conus arteriosus and distal truncus arteriosus
  • 2 growths from wall in spiral pattern, inferior upwards - separate tract into 2 channels Stage 13 truncus arteriousus
  • mesenchyme and neural crest contribute to this septation process
  • fusion of outgrowths separate aortic and pulmonary outflow
Chick Heart 001-icon.jpg Chick Heart 002-icon.jpg Chick Heart 002-icon.jpg
Normal Heart Abnormal Heart Abnormal Heart 2

Vascular Remodeling

fetal heart circulation

Arterial System

pharyngeal arch arteries
  • Aortic sac - remodels forming 2 horns, R forms brachiocephalic artery, L forms common carotid artery

Pharyngeal arch arteries

  • pharyngeal arch artery 1 and 2 regress
  • pharyngeal arch artery 3 and the associated dorsal aorta form the paired internal carotid arteries, these in turn generate the external carotids
  • Left pharyngeal arch artery 4 – forms the aortic arch
  • paraxial mesoderm forms paired dorsal aorta
    • head mesenchyme forms aortic arches
    • connecting stalk contains unbilical (placental) arteries
    • dorsal aortas give rise to
    • vitelline arteries which connect to capillaries on yolk sac
    • intersegmental arteries between somites

Venous System

Cardinal veins contribute nearly all systemic venous system.

common cardinal veins - ducts of Cuvier

hepatic veins - drain de-oxygenated blood from the liver into the inferior vena cava.

internal iliac vein - hypogastric vein

Birth Changes

Fetal circulation

At birth, cutting the umbilical cord and changes in the lungs after the first breaths trigger major functional adaptations in the fetal circulatory system.

  • blood flow through ductus venosus is eliminated
  • pulmonary circulation bed expands - reducing blood flow through ductus arteriosus
  • physiological closure of interatrial shunt
  • closure of ductus venosus in liver is prolonged
Fetal Structure Adult Structure
foramen ovale fossa ovalis
umbilical vein (intra-abdominal part) ligamentum teres
ductus venosus ligamentum venosum
umbilical arteries distal part -lateral umbilical ligaments; proximal part - superior vesical artery (supplies bladder)
ductus arteriosus ligamentum arteriosum


There are many different cardiac abnormalities, some more common than others, and only a few will be described in this lecture.

Major Abnormalities: Aortic Stenosis, Atrial Septal Defects, Coarctation of Aorta, Dextrocardia, Hypoplastic Left Heart, Long QT Syndrome, Patent Ductus Arteriosus, Pulmonary Atresia, Pulmonary Stenosis, Tetralogy of Fallot, Transposition of Great Vessels, Tricuspid Atresia, Total Anomalous Pulmonary Venous Connection, Ventricular Septal Defect, Abnormalities of Conducting System.

Links: Cardiovascular System - Abnormalities
Statistics-Utah heart defects.jpg

Atrial Septal Defects

Atrial Septal Defect
  • Atrial Septal Defects (ASD) are a group of common (1% of cardiac) congenital anomalies defects occurring in a number of different forms and more often in females.
  • patent foramen ovale - allows a continuation of the atrial shunting of blood, in 25% of people a probe patent foramen ovale (allowing a probe to bypassed from one atria to the other) exists.
  • ostium secundum defect
  • endocardial cushion defect involving ostium primum
  • sinus venosus defect - contributes about 10% of all ASDs and occurs mainly in a common and less common form. Common ("usual type") - in upper atrial septum which is contiguous with the superior vena cava. Less common - at junction of the right atrium and inferior vena cava.
  • common atrium

Ventricular Septal Defects

Ventricular Septal Defect
  • The Ventricular Septal Defect (VSD) usually occurs in the membranous (perimembranous) (70%) rather than muscular interventricular septum, and is more frequent in males that females.
  • Perimembranous defects are located close to the aortic and tricuspid valves and adjacent to atrioventricular conduction bundle.
  • The defect allows left-right shunting of blood, this shunting depends upon the size of the defect. Small defects may close spontaneously, larger defects result in infant congestive heart failure.
  • Clinically repaired by coils or tissue-adapted devices like muscular or perimembranous occluders.


Patent Ductus Arteriosus

Patent Ductus Arteriosus
  • Patent Ductus Arteriosus (PDA) occurs commonly in preterm infants, can close spontaneously (by day three in 60% of normal term neonates) the remainder are ligated simply and with little risk.
  • The operation is always recommended even in the absence of cardiac failure and can often be deferred until early childhood.

Tetralogy of Fallot

Tetralogy of Fallot
  • Named after Etienne-Louis Arthur Fallot (1888) who described it as "la maladie blue" and is a common developmental cardiac defect.
  • The syndrome consists of a number of a number of cardiac defects possibly stemming from abnormal neural crest migration. The basic defect in a tetralogy of Fallot is an asymmetrical fusion of the truncoconal ridges and a malalignment of the aortic and pulmonary valves. This results in the typical 4 features seen in this defect: 1. pulmonary stenosis, 2. overriding aorta, 3. ventricular septal defect, and 4. right ventricular hypertrophy.
Links: Cardiovascular System - Abnormalities


Heart1 looping icon.jpg Heart1 realign icon.jpg Heart1 atrium icon.jpg Heart1 ventricle icon.jpg
Heart Looping Heart Realign Heart Atrial Septation Heart Outflow Septation
Links: Flash Movies | Quicktime Movies

Glossary Links

Glossary: A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers | Symbols | Term Link

Course Content 2010

Embryology Introduction | Cell Division/Fertilization | Lab 1 | 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 | Stem Cells | Stem Cells | Endocrine | Lab 10 | Late Vascular Development | Integumentary | Lab 11 | Birth, Postnatal | Revision | Lab 12 | Lecture Audio | Course Timetable

Cite this page: Hill, M.A. (2024, June 16) Embryology 2010 Lecture 21. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/2010_Lecture_21

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G