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A morphological study on the obliteration processes of the ductus arteriosus in the horse
1Veterinary Hospital, Department of Veterinary Anatomy, Faculty of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
Insights
The equine ductus arteriosus undergoes significant changes during gestation and rapidly closes within three days after birth. Histological analysis reveals smooth muscle cell rearrangement and intimal thickening as key obliteration processes.
Area of Science:
- Veterinary Anatomy
- Developmental Biology
- Equine Perinatology
Background:
- The ductus arteriosus is a crucial fetal blood vessel that normally closes after birth.
- Understanding the timing and mechanisms of ductal closure in horses is vital for neonatal care.
Purpose of the Study:
- To investigate the morphometric and histological changes associated with ductus arteriosus obliteration in equine fetuses and newborns.
- To determine the physiological timeline for ductal closure in foals.
Main Methods:
- Morphometric analysis of ductal length, diameters, and circumference in equine fetuses and newborns.
- Histological examination of ductal tissue to identify cellular and structural changes.
Main Results:
- Ductal dimensions increased linearly in fetuses until 310 days, then decreased.
- Ductal measurements decreased post-birth, with closure observed in all foals by day three.
- Histology showed smooth muscle cell rearrangement and intimal thickening during intrauterine life and post-birth.
Conclusions:
- Preparatory modifications of the ductus arteriosus begin during fetal development.
- Smooth muscle cell rearrangement in the inner media is a primary event in ductal obliteration, occurring pre- and postnatally.
Abstract:
The obliteration processes of the ductus arteriosus of equine foetuses and newborn foals were studied morphometrically and histologically. The length, internal and external diameters and circumference of the ductus in equine foetuses increased progressively and linearly up to 310 days with advancing foetal age, but the values, especially the internal diameter, decreased from 320 to 330 days. After birth, the ductal measurements decreased gradually and ductal closure was found in three of 14 foals examined on the first day post partum, in two of six on the second day and in nine of nine on the third day or later, suggesting that the ductus arteriosus closes physiologically within three days after birth. Microscopical findings of the ductus arteriosus were characterised by the rearrangement of smooth muscle cells in the inner media and intimal thickening in foetuses, and by the central displacement of the intima in newborn foals. It was concluded that the ductus arteriosus begins to undergo preparatory modifications during intrauterine life, when the vessel is still functional, and that the most significant starting point of change in the obliteration processes is the rearrangement of smooth muscle cells in the inner media, which occurs during pre- and post natal life.