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Although anatomically simple structures, the atrial septum and the ventricular septum have complex embryological origins. Recent findings in molecular biology allowed better comprehension of their formation. As soon as the heart tube is formed, cells migrate from several cardiogenic fields to take part in the septation. Elongation, ballooning, and later inflexion of the heart tube create chamber separating grooves, facing the future septa. The systemic venous tributaries conflate at the venous pole of the heart; it will partially involute while contributing to the atrial septum. The primary atrial septum grows from the atrial roof towards the atrioventricular canal. It fuses there with the atrioventricular cushions, while its upper margin breaks down to form the ostium secundum. Then a deep fold develops from the atrial roof and partly covers the ostium secundum, leaving a flap-like interatrial communication through the oval foramen. It will close at birth. The interventricular septum has three embryological origins. The ventricular septum primum, created during the ballooning process, origins from the primary heart tube. It will form the trabecular septum and the inlet septum. The interventricular ring, surrounding the interventricular foramen, will participate in the inlet septum and also form the atrioventricular conduction axis. The outflow cushions will separate the outflow tract in the aorta and pulmonary artery, and grow to create the outlet septum. After merging with the atrioventricular cushions, they will also be part of the membranous septum.

The motion of thoracic and lumbar spine segments has been analysed by mean of the skin landmarks method on 14 volunteers (7 males, 7 females). Results demonstrate that: There is no significant difference between male and female. There is either facilitation, or limitation of the motion of the characteristic landmarks of the spinal segments during trunk motion in perpendicular planes. The mobility of the spinal segments is associated with pelvic girdle motion in order to obtain the planed amplitude, and varies with hips abduction. The analysis of the precise mechanisms of relaxing or stretching of the pelvi-spinal musculo-ligamentous structures constitutes a large field of investigation that necessitates the study of other pelvic limbs postures and needs the use of robotic techniques.

The analysis of the displacement of the pelvic girdle, during movements of the trunk in the anatomical orthogonal plans, was carried out by the technique of the cutaneous markers on two series of 7 male subjects and 7 female. The photographs made it possible to objectify angular displacements of reliable singular points and to observe that the abduction of hips determines, according to movements carried out, either a facilitation, or a limitation of displacements observed similar in the two series. The precise mechanism of these variations will have to be analyzed by later studies.

Physiological displacements of the trunk are the addition of these of the pelvic girdle and thoracic and lumbar spine segments. For a long time (3), this conjunction had been noticed but without numbered precisions. The purpose of this communication is to appreciate quantitatively, from a series of 16 subjects, the respective share of each components during lateral bending movements in the frontal plan and movements of rotation in the transverse plan. It results from this work that the pelvic girdle presents as reduced amplitude (4 degrees) in lateral bending on the other hand, displacement predominate to the level of thoracic spine (50 degrees). In rotation pelvic displacements are very important (30 degrees), while the spine so thoracic that lumbar has a weak participation (inferior to 5 degrees). Moderated abduction of hips increases by significant manner the motility of the pelvic girdle.