Cardiovascular System - Heart Development: Difference between revisions

Revision as of 15:54, 25 March 2010

Introduction

Human embryo heart (day 54 - 56)

In human embryos the heart begins to beat at about 22-23 days, with blood flow beginning in the 4th week. The heart is therefore one of the earliest differentiating and functioning organs.

The heart begins very early in mesoderm within the trilaminar embryonic disc. The heart forms initially in the embryonic disc as a simple paired tube inside the forming pericardial cavity, which when the disc folds, gets carried into the correct anatomical position in the chest cavity.

A key aspect of heart development is the septation of the heart into separate chambers. As the embryonic/fetal circulation is different to the neonatal circulation (lung/pulmonary activation), several defects of heart septation may only become apparent on this transition. One septal "defect" occurs in us all, the foramen ovale (between the 2 atria) which in general closes in the neonate over time.

Embryonic Heart Rate (EHR), early in development the heart starts to spontaneously beat and a recent study by Wisser and Dirschedl in dated human embryos showed an increase up to 63 postmenstrual days or 22 mm greatest length. Thereafter a steady decrease of EHR was noted. Maximal EHR is reached when morphological development of the embryonic heart is completed.

Textbooks

Human Embryology (2nd ed.) Larson Ch7 p151-188 Heart
The Developing Human: Clinically Oriented Embryology (6th ed.) Moore and Persaud Ch14: p304-349
Before we Are Born (5th ed.) Moore and Persaud Ch12; p241-254
Essentials of Human Embryology Larson Ch7 p97-122 Heart
Human Embryology Fitzgerald and Fitzgerald Ch13-17: p77-111

Human Development Timecourse

Cardiogenic region - in splanchnic mesenchyme of prechordal plate region
Week 2 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 40 At birth pressure difference closes foramen ovale leaving a fossa ovalis

Link: Timeline human development

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 tissue lining the inner surface of heart chambers and valves.

Heart Volume

Week*	Heart Volume (ml)	Lung Volume (ml)
10	0.6	1.6
18	4.3	10.9
30	26.6	49.3

Table data is "embryonic age" while original reference used "gestational age" (from LMP)(Data: Peralta CF, Cavoretto P, Csapo B, Falcon O, Nicolaides KH. Lung and heart volumes by three-dimensional ultrasound in normal fetuses at 12-32 weeks' gestation. Ultrasound Obstet Gynecol. 2006 Feb;27(2):128-33.)

Stroke Volume

Week*	Left Stroke Volume (ml)	Right Stroke Volume (ml)	Cardiac Output L/R (ml/min)
10	0.02	0.01	2.39 / 1.8
18	0.32	0.30	43.46 / 46.72
32	2.07	2.67	284.71 / 365.99

Table data is "embryonic age" while original reference used "gestational age" (from LMP). The stroke volume (SV) can be calculated from ultrasound measurement of end diastole volume (EDV) minus end systole volume (ESV); (SV = EDV - ESV). (Data: Molina FS, Faro C, Sotiriadis A, Dagklis T, Nicolaides KH. Heart stroke volume and cardiac output by four-dimensional ultrasound in normal fetuses. Ultrasound Obstet Gynecol. 2008 Aug;32(2):181-7.

Embryo Images

References

Person AD, Klewer SE, Runyan RB. Cell biology of cardiac cushion development. Int Rev Cytol. 2005;243:287-335. Review.
Matsui H, Ikeda K, Nakatani K, Sakabe M, Yamagishi T, Nakanishi T, Nakajima Y. Induction of initial cardiomyocyte alpha-actin--smooth muscle alpha-actin--in cultured avian pregastrula epiblast: a role for nodal and BMP antagonist. Dev Dyn. 2005 Aug;233(4):1419-29.
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.
Anderson RH, Webb S, Brown NA, Lamers W, Moorman A. Development of the heart: (2) Septation of the atriums and ventricles. Heart. 2003 Aug;89(8):949-58.
Brand T. Heart development: molecular insights into cardiac specification and early morphogenesis. Dev Biol. 2003 Jun 1;258(1):1-19.
Yutzey KE, Kirby ML. Wherefore heart thou? Embryonic origins of cardiogenic mesoderm. Dev Dyn. 2002 Mar;223(3):307-20.
Eisenberg LM. Belief vs. scientific observation: the curious story of the precardiac mesoderm. Anat Rec. 2002 Apr 1;266(4):194-7.
Davidson AJ, Zon LI. Turning mesoderm into blood: the formation of hematopoietic stem cells during embryogenesis. Curr Top Dev Biol. 2000;50:45-60.

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Cite this page: Hill, M.A. (2024, May 2) Embryology Cardiovascular System - Heart Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Cardiovascular_System_-_Heart_Development

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@@ Line 103: / Line 103: @@
 * [http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11920381 Eisenberg LM.] Belief vs. scientific observation: the curious story of the precardiac mesoderm. Anat Rec. 2002 Apr 1;266(4):194-7.
 * [http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=10948449 Davidson AJ, Zon LI.] Turning mesoderm into blood: the formation of hematopoietic stem cells during embryogenesis. Curr Top Dev Biol. 2000;50:45-60.
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