1. Development of heart and
respiratory system
By
Dr. Abdul Waheed Ansari
Chairperson &Prof. Anatomy, RAKCODS.
RAKMHSU.
12/18/2014 1
2. The learning outcomes for this
embryology topics are
• Formation of primitive heart tube from the
mesoderm.
• Five different chambers of embryonic heart
and their transformation in to 4 chambers of
adult heart.
• Common congenital forms of heart
development- ASD, VSD, & Fallot’s Tetralogy.
• Development of larynx, trachea and lungs.
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3. Primitive heart tube
• The heart is the first organ to form within the
embryo and this complex developmental
process begins during the fourth week.
• Heart developmental abnormalities affect 8-
10 of every 1000 births in the United States.
• The heart initially forms from two tubes
located bilaterally of the trilaminar embryo in
the cranial region.
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4. The image below shows the primitive tubes
developing in an embryo approximately 18 days
after conception
At the most cranial end of the
embryonic disc these blood
islands (splanchnic
mesenchymal cells) are
forming the primitive heart
tube.
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5. Two endothelial heart tubes come together and fuse in
the midthoracic region to form the primordial
cardiacheart tube- 22 days embryo
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6. There are five chambers in the primitive
heart
From venous end to arterial end the
five chambers are as follows:-
1. Sinus venosus
2. Primitive atrium
3. Primitive ventricle
4. Bulbus cordis
5. Truncus arteriosus
• The primitive heart begins to beat on
22nd day of intrauterine life.
• The circulation does not start until
days 27-29.
• The sinus venosus will transform into
right atrium-smooth part.
• The primitive atrium will split and form
rough parts of right and left atria of
adult.
• The primitive ventricle develops into
right and left ventricle in adult.
• The bulbus cordis get absorbed into
smooth part of right and left ventricle.
• The truncus arteriosus will form the
aorta and pulmonary trunk.
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7. Common congenital heart diseases
• This abnormality is
Ventricular Septal
Defect.
• There will be a hole
between right and left
ventricles
• 25% of CHD are VSD.
• VSD is more frequent in
males.
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8. Tetralogy of Fallot’s
• The incidence of this
abnormality is 9-14% of
CHD.
• There are 4 components for
this syndrome:-
1. pulmonary stenosis,
2. VSD,
3.dextroposition of aorta,
4. RV hypertrophy.
• Results in cyanosis.
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9. Transposition of the Great Vessels
• It occurs in 10-11% of
CHD.
• Aorta arises from the RV
with the pulmonary trunk
arising from the left.
• Most common cause of
cyanotic heart disease in
newborns
• This can be surgically
corrected.
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10. Atrial Septal Defect
• This defect occurs in 6-10%
of CHD.
• This defect is more common
in females.
• Most commonly patent
foramen ovale; can also be
an ostium secundum defect,
an endocardial cushion
defect with ostium primum
defect, sinus venosus
defect, common atrium.
• Results in cyanosis due to
right-to-left shunt.
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11. Development of larynx
• The larynx is first seen as an outgrowth from the foregut during week 4 of
fetal development.
• The outgrowth of tissue is called the lung bud or the respiratory
diverticulum, which is a ventral diverticulum of endoderm that arises from
the floor of the foregut caudal to the pharynx.
• The lung bud forms a groove in the floor of the pharynx called the
laryngotracheal groove.
• The lung bud mesenchyme gives rise to the smooth muscles of the lower
respiratory system.
• The lung bud initially is in open communication with the foregut, but
eventually they become separated by indentations of mesoderm called the
tracheoesopheageal (or esophagotracheal) folds.
• In the 4th week of development, the tracheoesophageal folds fuse in the
midline to form the tracheoesopheageal septum, and it is here where the
foregut divides into the trachea ventrally and esophagus dorsally.
• The opening of the respiratory diverticulum into the foregut becomes the
laryngeal orifice.12/18/2014 11
13. Development of cartilages and muscles of
larynx
• The pharyngeal arches or branchial arches are the ridges like
structures developing below the head region of the embryo
during the 5th – 6th weeks of I.U.L.
• There are 6 branchial arches developing on either sides of
primitive pharyngeal cavity.
• Each pharyngeal arch is covered by ectoderm, having a central
core of mesoderm and lined internally by endoderm. In addition
to mesenchyme derived from paraxial and lateral plate
mesoderm, the core of each arch receives substantial numbers of
neural crest cells, which migrate into the arches to contribute to
skeletal components of the face.
• Each arch contains an artery, cartilage, nerve, & muscular
component.
• Arches and Pouches form the face, tongue, lips, jaws, palate,
pharynx and neck cranial nerves, sense organ components,&
glands.12/18/2014 13
14. Each arch will give rise to muscles,
cartilages, bones and ligaments
• The laryngeal cartilages and intrinsic muscles of
larynx develops from 4th & 6th pharyngeal arches.
• The nerve of 4th arch is external laryngeal nerve.
• The cricothyroid muscle of larynx is the only
intrinsic muscle visible outside the larynx and it is
supplied by external laryngeal nerve, a branch of
vagus nerve
• All intrinsic muscles of larynx are supplied by
recurrent laryngeal nerve, branch of vagus. It is
the nerve of 6th pharyngeal arch.
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16. Pharyngeal arches that contributes to
larynxPharyngeal Arch 4
• Associated with aortic arch 4,
which contributes to the proximal
segment of the right subclavian
artery and the arch of the aorta.
• Innervated by CN X (superior
laryngeal branch of the vagus
nerve).
• The thyroid, cricoid, arytenoid,
corniculate and cuneiform
cartilagesdevelop from mesoderm of
4th arch.
The cricothyroideus muscle
develops from 4th arch.
Pharyngeal Arch 6
• Associated with aortic arch
6, which contributes to the
proximal segments of the
pulmonary arteries and
ductus arteriosus (which
becomes the ligamentum
arteriosum in the adult).
• Innervated by CN X
(recurrent laryngeal branch
of the vagus nerve).
• Epiglottis develops from
hypobranchial eminence.
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