This document provides an overview of heart embryology. It describes how the heart develops from two endothelial heart tubes that fuse to form sections including the atria, ventricles, and bulbus cordis. The document outlines the formation of the interatrial septum from the septum primum and secundum, as well as the absorption of the sinus venosus into the right atrium. It also discusses the development of the interventricular septum from the bulbar ridges and proliferation of tissue from the atrioventricular cushions. Common congenital heart anomalies are mentioned including defects of the atrial and ventricular septa.

1. EMBRYOLOGY
OF
HEART
BY: DR.SHILPA PRAJAPATI
(FIRST YEAR M.PT)

2. 1. Introduction
contents
2. Heart
3. Exterior of the heart
4. Formation of interatrial septum
5. Absorption of sinus venosus into right atrium
6. Development of the right atrium
7. Absorption of the pulmonary veins
8. Development of left atrium
9. Bulbus cordis
10.Interventricular septum
11.Development of the ventricles
12.Conducting system of the Heart
13. Congenital anomalies of Heart

3. INTRODUCTION
Very early in the life of the embryo, mesenchyme
differentiates over the yolk sac and in the body of
embryo itself to form small masses of angioblastic
tissue.
which gives rise to
endothelium and blood cells.
The heart is first organ of the body to start
functioning, is prominent in 21 to 28 days
post conception.

4. Heart
Fusion of endothelial heart tubes
Heart is in form of two endothelial heart tubes,
 fuse with one another,
 shows series of dilatation.
Cranial to caudal end are
 Ventricle and atrium,
connected by A.V. canal.
 Fusion in the heart tube in sinus venosus is partial.

5. Heart
Fusion of endothelial heart tubes
Bulbus cordis represents arterial end of heart.
conus (bulbus cordis).
truncus arteriosus.
continuous with the aortic sac from which right and
left pharyngeal arch arteries arise.

6. Heart
Arterial and venous ends of heart tube
Sinsus venosus represents the venous end of the heart.
Horns joins:
i. Vitelline vein from yolk sac
ii. Umbilical vein from placenta
iii. Common cardinal vein from body wall
 The body and right horn are absorbed into the common
atrial chamber, form part of the right atrium.

7. Heart ….
Subdivisions of the Heart Tube
Right CCV forms terminal part of SVC.
Rt Vitelline vein forms terminal part of IVC
Left horn forms part of the coronary sinus.
They open into the atrium.
ATRIUM:
Right and left atria.
A.V.CANAL:
Forms right and left halves, take part in the formation of atria.

8. Heart ….
Subdivisions of the Heart Tube
VENTRICLE:
Bulbus cordis is absorbed into the ventricular
chamber and forms to give rise to the right and left
ventricles.
And forms outflow tracts
TRUNCUS ARTERIOSUS:
Form the ascending aorta and the pulmonary trunk.

9. Heart …
Heart tubes to pericardial cavity
Endothelial heart tubes derived from splanchnopleuric mesoderm
After formation of head fold, tube lies dorsal to pericardial cavity
and ventral to foregut.
Splanchnopleuric mesoderm, on dorsal side, form a thick layer
called myoepicardial mental, After complete invagination, layer
completely surrounds the heart tubes.
It gives rise to the cardiac muscle and visceral layer of
pericardium(epicardium).
Parietal layer derived from somatopleuric mesoderm.

10. Anomalies
Poor development of myocardium(hypoplasia).

11. Exterior of the heart
The heart tube is for sometime suspended from the dorsal
wall of the pericardial cavity, Mesocardium soon disappears
It folded to form ‘U’ shaped
bulbo-ventricular loop.
Atrium and sinus venosus come behind
and above the ventricle form ‘S’ shaped.
At that stage, bulbus cordis and ventricle are separated by
deep bulbo-ventricular sulcus, After these changes exterior of
the heart assumes its definitive shape.

12. Exterior of the heart…
sinus venosus
Sinus venosus and atrial chamber are at first in open
communication.
They become partially separated by grooves at the junction of
these two chambers.
Right groove remains shallow, left one becomes very deep.
left part become completely separated from atrial chamber.
The left horn and its tributaries much reduce in size and
appears as tributary of the right half.

13. Exterior of the heart…
Retrogression of left horn of sinus venosus
Centrally placed sinu-atrial orifice shifts to the right.
Orifice at first transversely orientated becomes vertical.
Margins of orifice come to be bounded by the right and
left venous valves.
Upper ends of the two valves fuse to form structure
called septum spurium.

14. Exterior of the heart…
Atrio-ventricular canal
At first rounded aperture, soon comes to be transverse
canal.
On its dorsal and ventral walls Atrio-ventricular cushions
appears.
This grow and fuse with each other to divide the Atrio-
ventricular canal in right and left halves.
This is called septum intermedium.

15. Anomalies
Atrio-ventricular canal defect or persistent Atrio-
ventricular canal :
Defective formation of AV cushions may leads the
interatrial and interventricular septa are in complete.

16. Formation of interatrial septum
Atrial chamber communicates:
•Posteriorly with sinus venosus
•Anteroinferiorly with ventricle.
Divided into right and left halves:
a) Septum arises from the roof of the atrial chamber is septum
primum (ostium primum).
•Grows downwards towards the septum intermedium of AV
canal.
•Only for sometime foramen primum is present.
•Septum primum fuse with septum intermedium, closing the
foramen primum.
•upper part of septum primum form foramen secundum
(ostium secundum)

17. Formation of interatrial septum
b) A second septum to the right of the septum
primum, btw septum primum and septum spurium.
•It grows and overlaps the foramen secundum.
•Right and left atria communicate through foramen
ovale.
•Lower edge of septum secundum (crista dividends)is
thick and firm.
•Edge of the septum primum forms the lower
boundary of foramen secundum is thin and flap.

18. Formation of interatrial septum
Blood flows from right to left atrium through this
foramen.
When blood flows left to right, flap comes into
apposition with the septum secundum and close the
opening.
After birth, left atrium begins to receive blood and the
pressure becomes greater than right atrium.
Causes closer of foramen ovale, permanently fusion of
two flaps.
In adult anatomy, annulus ovalis represent septum
secundum.
Fossa ovalis represents septum primum.

19. Congenital anomalies
Defective formation of septa
A). Interatrial septal defects
I. septum primum defect: septum may fail to reach the
AV endocardial cushions.
II. septum secundum defect : may fail to develop as a
foramen secundum remains wide open.
III. Patent foramen ovale : the oblique valvular passage
between septum primum and secundum remain
patent.
IV. Occasionally , premature closer of the foramen ovale.

20. Absorption of sinus venosus into
right atrium
Right and left venous valves separates.
Left valve and the septum spurium fuse with the
interatrial septum.
Right valve becomes greatly stretched out and
subdivided into three parts:
i. Crista terminalis
ii. Valve of the IVC
iii. Valve of coronary sinus

21. Development of the right atrium
Derived from
a)Right half of the primitive atrium
b)Sinus venosus
c)Right half of the atrio ventricular canal

22. Absorption of the pulmonary
veins
At the time when septum primum beginning, a
single pulmonary vein open into the left half of the
atrium.
Vein divides into right and
left branch.
Gradually veins nearest to the left atrium are
absorbed into the atrium, four separate veins come to
open it.

23. Development of left atrium
Derived from:
a) left half of the primitive atrial chamber
b) left half of the AV canal
c) absorbed proximal parts of the pulmonary veins

24. Bulbus cordis
Divisible into a proximal part; conus
Distal part; truncus arteriosus
Pulmonary and aortic valves, derived from
endocardial cushion.
Grows and fuse with each other in wall of conus.
Aortic and pulmonary openings each have 3
cushions; forms 3 cusps of valve.

25. Congenital anomalies
Atresia or stenosis
any of the orifice may have too narrow an opening
(stenosis),or non at all(atresia).
Types :
1. Valvular
2. Supravalvular
3. Infravalvular
Abnormal growth
1. Accessory cusps in the valves.
Defects of the spiral septum:
septum may not be formed at all also called patent truncus
arteriosus.

26. Interventricular septum
Bulbo-ventricular cavity consists of:
a)Primitive ventricle
communicates
Posteriorly with
atria through
bilateral A.V canals.
b) Conical upper part
communicating
with truncus arteriosus.

27. Interventricular septum
Cavity subdivided in to right and left halves:
a) Each half communicates with corresponding atrium
b) right ventricle opens into pulmonary trunk and left
ventricle into the aorta.
 Subdivision takes place as:
1) A septum – called interventricular septum, grows
upwards from the floor of bulbo-ventricular cavity and
fused with atrio-ventricular cushions(septum
intermedium)
2) Two ridges –right and left bulbar ridges
Arises in the wall of bulbo-ventricular cavity continuous
with the right and left endocardial cushions fuse to form
bulbar septum(conus septum).

28. Interventricular septum
3) The gap btw upper edge of interventricular septum and lower edge
of bulbar septum, field by proliferation of tissue from A.V cushions.
Membranous part of the interventricular septum: Divisible into
anterior and posterior part separated by A.V septum.

29. Interventricular septum
The membranous part of the interventricular septum is
made up
1) of the original AV cushion btw the attachment of the
interatrial and interventricular septa.
2) of the endocardial proliferation from these
cushions.
 First part separates the left ventricle from the right
atrium while the lower part separates two ventricles.
The tricuspid valve is attached to the membranous
septum at the junction of these parts.

30. Anomalies
Interventricular septum defect : may seen in
membranous or in muscular part of septum

31. Development of the ventricles
Derive from:
a).primitive ventricular chamber
b).proximal part of the bulbus cordis (conus)
Gives rise to infundibulum of right ventricle,
And to the aortic vestibule of the left ventricle.
Aortic and pulmonary valves are formed at the
junction of conus and truncus arteriosus.
Mitral and tricuspid valves formed by proliferation of
connective tissue of A.V canal.

32. Conducting system of the Heart
When there are two heart tubes, pacemaker lies in the
caudal part of the left tube.
After fusion , lies in the sinus venosus.
When the sinus venous is incorporated into the right
ventricle ,it lies near the opening of the SVC.
The A.V node and A.V bundle form in the left wall of the
sinus venosus, and In the A.V canal.
After the sinus venosus is absorbed, A.V node lie near
the interatrial septum.

33. Congenital anomalies of Heart
Anomalies of position
a).Dextrocardia :chambers and blood vessels are reversed
from side to side.
b).Ectopia cordis : heart lies exposed on the front of
the chest, and can be seen from the outside , due to
defective development of the chest wall.
Abnormal growth
1. Tumors

34. Congenital anomalies of Heart
Combine defects :two or more of the above defects may
consist , condition of this type known as fallot’s tetrology
I. interventricular septal defect :
II. Aorta over riding the free upper edge of the
ventricular septum.
III. Pulmonary stenosis
IV. Hypertrophy of the right ventricular

35. Congenital anomalies of Heart
Other defects :
a).pericardium may be partially or completely absent.
b).Congenital defects in conducting systems
c).Transposition of great vessels
d).Taussing – bing syndrome
e).superior or inferior vana cava end in the left atrium.
f).pulmonary veins end in the right atrium or in one of its
tributaries.

36. Patent ductus arteriosus
The ductus arteriosus, connects the left pulmonary
artery to descending thoracic aorta just beyond the
origin of the left subclavian artery, should have
contracted, closed and fibrosed into the ligamentum
arteriosum in a few days from birth.
It persist and blood will flow from the aorta into the
pulmonary circulation

38. References
•Text book of medical physiology ( Guyton and hall,
9th Edition)
•Human embryology( Inderbir Singh)
•Human embryology(Hamilton, body and Mossman's)
•Text book of obstetrics( D.C.Dutta)

41. Fetal circulation
1. Source of oxygenated blood is placenta.
2. Through the umbilical vein; a small portion of blood
passes through the substances of liver to IVC, but the
greater part passes direct through ductus venosus to
IVC.
3. Through the IVC blood reaching the right atrium.
a. most of passes through the foramen ovale into the left
atrium.
b. The rest of it get mixed up with the blood returning
through the SVC to the Rt atrium, passes in to the Rt
ventricle.

42. Fetal circulation
4. From the Rt ventricle, deoxygenated blood enters the
pulmonary trunk.
a) only a small portion of blood reaches the lungs, passes to
Lt atrium.
b) the greater part is sort circuited by the ductus arteriosus
into the aorta.
5. Lt atrium receives
a) Oxygenated blood from Rt atrium
b) A small amount of deoxygenated blood from lungs
This oxygenated blood passes into the left ventricle and
then into aorta. some of this passes into carotid and
subclavian arteries. And rest of it mixed with
deoxygenated blood from ductus arteriosus.

43. Fetal circulation
6. Much of blood of the aorta is carried by the
umbilical arteries to the placenta.

44. Changes in circulation at birth
1) Muscle in the wall of the umbilical arteries contracts
immediately after birth, this prevent loss of fetal blood into
the placenta.
2) Lumen of the umbilical veins and ductus venosus is
occluded.
3) Ductus arteriosus is occluded, so all blood from Rt ventricle
goes to the lungs, is caused by contraction of muscle in the
vessel wall.
4) Through pulmonary vessels much larger volume of blood
reaches the Lt atrium, causing the valve of foramen ovale to
close.
5) When the new born cries, rise of pressure in the Rt atrium
leading to a temporary shunt to the left. This can cause
cynosis.

45. Changes in circulation at birth
Vessels occluded soon after birth are:
•Umbilical artery medial Umbilical ligament
•Left Umbilical vein ligamentum teres of the liver
•Ductus venosus ligamentum venosum
•Ductus arteriosus ligamentum arteriosum