Some observations on vessels in the arterial wall

This thesis is entitled "Some observations on Vessels in the Arterial Wall" and is concerned with a study of the vasa vasorum in the aorta; coronary arteries; pulmonary trunk and arteries; arteries of the root of neck; basilar and cerebral arteries; limb arteries, ductus arteriosus and umbilical arteries. Postnatal specimens were examined from birth to eighty years of age, to compare the characteristic pattern and distribution of the vasa vasorum in the arterial wall and the changes which occur with age. Foetal specimens were examined to determine when the arterial wall ceased being dependant completely upon luminal blood for nourishment, and to compare the prenatal patterns and distribution of the intramural vessels with the postnatal microcirculation. The umbilical arteries and ductus arteriosus were chosen as examples of arteries showing adaptive changes at birth, and the effect of this on the vasa vasorum was considered. Both foetal and postnatal arteries were injected at physiological pressures with a radio-opaque medium (Micropaque) and examined with the Coslett Nixon x-ray projection microscope. This instrument produces a point source of x-rays from a metal target, which penetrates the full thickness arterial wall, and allows examination of the specimen without routine histological preparation, in contrast to previous investigations. In each artery the aim of the examination was to differentiate between the arterial and venous sides of the microcirculation; examine the characteristic patterns of the arterial and venous vasa; determine the depth the intramural vessels penetrated, and investigate the effect of age on the development of vassal architecture. In intrauterine life it was found that vasa vasorum first appeared on the abdominal aorta, and that the neonatal pattern had developed in the remainder of the aortic wall and pulmonary trunk by the thirty fourth week, all the vasa being confined to the adventitial layer. Postnatal development of the vasa vasorum was characterised by the template of adult appearances being formed in the adventitia in the second year, and penetration of the media from the fourth year, with vascularization of the arterial wall being completed by the fifteenth year. Arteries showing adaptive changes at birth were vascularized in the later weeks of pregnancy; showed the neonatal pattern by the thirty fourth week, and were characterised by a rapid ischaemia after birth. From these findings the importance of the vasa vasorum in relation to the haemodynamics of the circulation as it affected the arterial wall; the formation of aortic aneurysm and aortic grafting, and the extent the arterial wall was vascularized by vasa vasorum was discussed