Cardiovascular SystemEmbryology and Anatomy*

Dr. Kalpana MallaMBBS MD (Pediatrics)

Manipal Teaching Hospital

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Embryonic Heart Development

The heart develops in the embryo during post-conception weeks 3 - 8

Beginning Development

• Early week post-conception: 2 endothelial tubes• Mid-week : endothelial tubes fuse to form a

tubular structure• 28 days following conception: the single-

chambered heart begins to pump blood

Week 4

• Heart has: – single outflow tract, the truncus arteriosus (divides to

form aorta & pulmonary veins)– Single inflow tract, the sinus venosus (divides to form

the superior and inferior vena cavae)– Single atrium– Single ventricle– AV canal begins to close

Weeks 5

Week 5

• AV canal closure complete

• Formation of atrial and ventricular septums

• Heart grow rapidly, and fold back on itself to form its completed anatomic shape

Week 7

• Ventricular septum fully developed

• Coronary Sinus forms

• Outflow tracts (aorta & pulmonary truck) fully separated

8 Weeks After Conception

• By the end of the 8th week after conception the fetus has a fully developed 4-chambered heart

Layers of Heart

• Pericardium (most superficial)

– Visceral, parietal

• Myocardium (middle layer)– Cardiac muscle

• Endocardium (inner)– Endothelium

Lines the heart

Creates the valves

Right Heart Chambers

• Right Atrium (most of base of heart)– IVC, SVC, Coronary sinus – Rt atrium– Ventral wall = rough Pectinate muscle– Fossa Ovalis- on interatrial septum, remnant

of Foramen Ovale

Right Heart Chambers

• Right Ventricle– RA – TV – RV – Pulmonary Valve- pulmonary trunk

- lungs– Trabeculae Carnae – muscle ridges along ventral

surface– Papillary Muscle-cone-shaped muscle to which

chordae tendinae are anchored– Moderator Band-muscular band connecting anterior

papillary muscle to interventricular septum

Left Heart Chambers

• Left Atrium– Lungs - 4 Pulmonary Veins –LA– Pectinate Muscles line only auricle

Left Heart Chambers

• Left Ventricle (apex of heart)– LA – mitral valve – LV – AV – aorta – body– Same structures as Rt Ventricle: Trabeculae

carnae, Papillary muscles, Chordae tendinae– No Moderator Band

Heart Valves - heart sounds

Heart Valves: Lub*-Dub

• Tricuspid Valve: Right AV valve – 3 Cusps (flaps) - anchored in Rt. Ventricle by

Chordae Tendinae– Chordae Tendinae prevent inversion of cusps

into atrium– Closure of AV valve – 1st heart sound

Heart Valves: Lub*-Dub

• Bicuspid (Mitral) Valve: Left AV valve– 2 cusps anchored in Left Ventricle by chordae

tendinae– Functions same as Rt. AV valve

Heart Valves: Lub*-Dub

• **Semilunar valves:

• Pulmonary Semilunar Valve: RV to Pulmonary Trunk– Aortic Semilunar Valve: LV to Aorta– 3 cusps– Closure of SV – 2nd heart sound

The Great Vessels and major branches

Aorta (from Left Ventricle)

• Ascending– Coronary arteries

• Aortic Arch – Brachiocephalic trunk– Left Common Carotid– Left Subclavian

• Descending (Thoracic/Abdominal)– Many small branches to organs

The Great Vessels

• Pulmonary veins

- 4 into heart (lt atrium) • Pulmonary Trunk (from Rt Ventricle)

- -2 Pulmonary Arteries into lungs

– Inferior/Superior Vena Cava / Coronary sinus

Flow of Blood• Deoxygenated - SVC+IVC, Coronary Sinus -

enters RA - Tricuspid Valve - RV - Pulmonary Valve - Pulmonary trunk → Pulmonary Arteries → lungs

• Oxygenated blood - 4 P Veins - LA - Bicuspid/Mitral Valve – LV – Aortic Valve - Aorta - body

The Normal Heart

Circulation

• Coronary circulation – the circulation of blood within the heart

• Pulmonary circulation – the flow of blood between the heart and lungs

• Systemic circulation – the flow of blood between the heart and the cells of the body

Fetal Circulation: main differences

1. Presence of placental circulation

2. Presence of ductus venosus – UV to IVC

3. Absence of gas exchange in collapsed lungs

4. Widely open foramen ovale

5. Widely open ductus arteriosus

Three Shunts of Fetal Circulation

• Ductus Venosus (Ligamentum venosum)

- Oxygenated blood from placenta - fetal UV - IVC – RA - by passes liver

• Foramen Ovale

- From RA to LA – by passes the RV,Pulmonary trunk -no blood to lungs

• Ductus Arteriosus– Blood from pulmonary trunk to aortic arch – by passing lungs

Fetal Circulation

• Umbilical Vessels:

-2 Umbilical Arteries (Medial Umbilical Ligaments) =deoxygenated blood from fetus to placenta– 1 Umbilical Vein (Ligamentum teres)= Oxygenated

blood to fetus from placenta

Fetal Circulation

– Placenta - umbilical vein - ductus venosus –IVC – RA- foramen ovale –LA –LV – Aorta – systemic circulation

– RA – RV – pulmonary trunk - ductus arteriosus – aortic arch - enter the systemic circulation, by passing the pulmonary circulation

Fetal circulation before birth

• Note :oxygenated blood mixes with deoxygenated blood in

(I)Liver

(II)IVC

(III)rt. Atrium

(IV)Lt. Atrium

(V)entrance of the ductus arteriosus into the descending aorta

After Birth

• Lungs expands with air and pulmonary vascular resistance falls. Pulmonary blood flow increases

• The foramen ovale and ductus venosus close during the first day of life

• The ductus arteriosus close during the first 24 – 72 hours of life

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