While the development of the vascular system in
other organs is regulated by functional influences
and hereditary factors; in the case of the placenta
the site of implantation in the uterus and the
characteristics of the maternal circulation also
play an important role.
The maternal and foetal blood circulatory paths
within the placenta are regarded from the haemodynamic
point of view as most complicated because the
placental structure is looked upon as being most
complex. Many contradicting views are held in that
respect and many theories are formulated regarding
the placental structure and maternal blood circulation
through it. It is clear that in order to understand
these questions the placental connections with the
uterus and foetus must be studied both with the naked
eye and microscope.
The human placenta according to Grosser is
described as a placenta haemochorialis, thereby
meaning that the foetal chorion is in direct
relationship with the maternal blood.
This fact underlies many risks that the pregnant,
parturient, and puerperal woman undergoes and it
follows that a sound knowledge of the vascular
conditions in the pregnant uterus underlies the
pathology of reproduction. For instance: is the
mechanism of antepartum and postpartum haemorrhage
really understood? or the factors that are
associated with embolus complicating child birth
known? - advancement in obstetrics depends to some
extent on the complete knowledge of this subject.
In 1935 Rudolf Spanner of Kiel brought forward
a new conception formulating a new idea not only of
the structure of the placenta but of the circulation
of the maternal blood through that organ and back to
the uterine veins. His work depended on injection
experiments on the pregnant uterus and placenta.
In the present scope of this work Spanner's work on
the subject has been studied and experiments done
to compare with his results.