CARDIAC DEVELOPMENT & FETAL

CIRCULATION

CARDIAC DEVELOPMENT

Cardiac morphogenesis

Looping

Septation

Molecular development

Functional development

CARDIAC MORPHOGENESIS

18 DAYS -

vasculogenesis .. Cell

clusters on either side of

embryonic axis

22 days – fuse –primitive

heart

Splanchnic mesoderm

forms myocardium&

myocardial jelly

Migrating mesothelial

cells-epicardium

HEART STARTS TO

CONTRACT

LOOPING

22-24 days to 28 ndays

Heart bends ventrally and

toward right

Outside appearance similar to

our heart

CARDIAC SEPTATION

Inside appearance

26 days

Atrium

Septum primum

Septum secundum

Ostium primum , ostium secundum

S.P + O.S = foramen ovale

VENTRICLES

INLET – primitive ventricle

OUTLET – bulbus cordis

conotruncal septum

spiral septum aorta &

pulm artery

MOLECULAR DEVELOPMENT

CARDIAC DIFFERENTIATION

ENDODERM-INDUCTION OF MESODERM SIGNALS

FGF ACTIVIN

INSULIN

TRANSCRIPTIONS FACTOR S

GATA4 MEF2

NKX

BHLH

RETIONOIC ACID RECEPTOR FAMILY

RECEPTO

RS

MYOCYTE

MYOCYTE

• SIMILAR ISOFORMS

• MLC , ANP

VENTRICULAR

• MLC 2v

ATRIAL

• MLC2a

• ANP

FUNCTIONAL DEVELOPMENT

FETAL CIRCULATION

the dorsal aortae develop at the same time as the early heart tubes. These connect to the heart tubes prior to fusion via the first aortic arch arteries. Other arches develop, which go on to form the arteries of the head and neck. We also previously saw the way in which the aorta and pulmonary trunk form. The dorsal aorta gives off branches which supply blood to the rest of the embryo:

Gut (ventral/front) branches

Lateral (side) branches

Intersegmental arteries

Fetal Circulation

As the embryo progresses to a fetus the vasculature is still remarkably different to that of the adult, including the presence of three vascular shunts:

foramen ovale (seen previously) - blood travels from the right atrium to the left atrium

ductus venosus - blood from the umbilical vein bypasses the liver to enter the inferior vena cava

ductus arteriosus - blood passes from the pulmonary trunk into the aorta

These shunts allow blood to bypass the lungs, liver and kidneys, whose functions are performed by the placenta while in utero.

The following diagram shows the movement of blood throughout the fetal circulation. The main flow of blood is as follows:

Placenta → umbilical vein → ductus venosus → inferior vena cava → right atrium → foramen ovale → left atrium → left ventricle → aorta → hypogastric arteries → umbilical arteries → placenta. Blood that passes from the right atrium to the right ventricle travels:

Right ventricle → pulmonary trunk → ductus arteriosus → aorta