Reference is by Veterinary embryology. DVM 2nd semester students must download. If not understandable anything see figure in next slide.

1. Embryonic Normal
Development of Heart
Submitted to :DR. RIAZ HUSSAIN PASHA

2. Submitted by:
ATTIQUE HASSAN
ZIKRIA MANZOOR
M.ABDULLAH
DVM 2nd semester(EVENING)

3. Some important terms
• Embryo :
“an unborn or unhatched offspring in the
process of development, in particular a human offspring
during the period from approximately the second to the
eighth week after fertilization (after which it is usually
termed a fetus).”
• Heart:
“ Heart is pumping organ. Which pumps and distribute
blood throughout the body.”

4. Importance of cardiac system
• In the early stages of embryological development, the
respiratory, excretory and nutritional requirements of
the embryo are provided through simple diffusion.
• As the mammalian embryo increases in size, diffusion is
inadequate for its nutritional, respiratory and excretory
needs. Because of its increasing size and complexity, the
developing embryo requires a system for delivering
oxygen and nutrients to its tissues, and for transporting
its waste products. These requirements are supplied by
the cardiovascular system.

5. Heart Development
• 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. 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.
• The floor of the amniotic cavity is formed by the embryonic disc.
• Embryonic disc: “The thickened plate from which the embryo
develops in the second week of pregnancy.”
Embryonic
disc

6. How Heart Forms
• Heart development refers to the prenatal
development of the human heart. This begins with the
formation of two endocardial tubes which merge to
form the tubular heart, also called the primitive heart
tube.
• The heart tube elongates on the right side, looping and
becoming the first visual sign of left-right asymmetry of
the body. Septa form within the atria and ventricles to
separate the left and right sides of the heart.

8. Formation of heart chambers
• Partitions which form in the primordial mammalian
heart gradually convert the single pulsating cardiac tube
into a complex four-chambered organ. Although
formation of cardiac septa takes place at approximately
the same time, for descriptive purposes their formation
is described as if they were separate events. The foetal
heart continues to function effectively as these ongoing
major structural changes occur.

9. Partitioning of the atrio-ventriculor canal
• In the region of the atrio-ventricular canal, two masses
of cardiac mesenchymal tissue known as endocardial
cushions, which are located between the endocardium
and the myocardium. extend towards each other and
fuse. The fused endocardial cushions form the septum
intermedium, which divides the common atrio-
ventricular canal into left and right atrio-ventricular
openings

11. Final form of Right Atrium
• The terminal portion of the pectinate muscles
form crista terminalis.
• sulcus terminalis: A sulcus which externally
represent the crista terminalis.
• The regressing left horn of the sinus venosus
contributes to the formation of the coronary
venous sinus which opens into the right atrium.
• Venous Sinus also called as Sinus venorum.

13. Left Atrium
• During the embryonic development the common
pulmonary vein become incorporated into left atrium.
• Structures inside left atrium are similar to those of right
atrium.

14. Formation of the left and right ventricles
• The dilated portion of the bulbus cordis and the
embryonic ventricle form a common chamber.
•BULBUS CORDIS:
“In the embryo the segments of the
heart tube destined to be a partitioned and to form the
two ventricular outflow segments to the aorta on the
left to the pulmonary trunk on the right.”

15. Conti
• As the walls of the ventricle and bulbus cordis increase
in thickness diverticulation of their inner surfaces
imparts a trahecular appearance to the myocardium.
• At this stage, the embryonic ventricle can be considered
as the primitive left ventricle and the dilated bulbus
cordis as the primitive right ventricle.
• As the inter-ventricular sulcus deepens and the walls of
the expanding ventricles meet medially at the sulcus.
the walls become apposed and fuse, contributing to the
elongation of the intervenlricular septum.

16. Final form of right ventricle
• Conus arteriosum:
“ A doom shaped structure formed by
right ventricle at cranial border of heart.”
• Trabeculae carnea:
“Rough wall of ventricle which bears
muscular ridges and bands.”
• Moderate bands:
“Extend from septum to opposite wall.”

19. Final form of left ventricle
• Trabeculae carnea:
“Rough wall of ventricle which
bears muscular ridges and bands.”
• Moderate bands:
“Extend from septum to opposite
wall.”
• Ventricular septum:
“ It is a portioning which separate
the cavities of two ventricles.”

21. Formation of cardiac valves
• The aortic and pulmonary valves, which are necessary
for prevention of backflow of blood into the left and
right ventricles, arise from three swellings of sub-
endothelial mesenchymal tissue at the origins of the
aortic and pulmonary trunks.
• Mesenchymal tissue:
Type of connective tissue found
in embryonic life only. Composed of ground substance
And a few fibers/cells.

23. Heart Walls
• The main walls of the heart are formed between day 27 and 37
of the development of the early embryo.
• The myocardium thickens and secretes a thick layer of
rich extracellular matrix containing hyaluronic acid which separates
the endothelium. Then mesothelial cells form the pericardium and
migrate to form most of the epicardium. Then the heart tube is
formed by the endocardium, which is the inner endothelial lining of
the heart, and the myocardial muscle wall which is the epicardium
that covers the outside of the tube.