Paper - Note on a case of patent ductus arteriosus and patent foramen ovale in a mature sheep (1939)
Beattie FJ. Note on a case of patent ductus arteriosus and patent foramen ovale in a mature sheep. (1939) J Anat. 74: 662-663. PMID 17104789
Note on a case of patent ductus arteriosus and patent foramen ovale in a mature sheep
By F. J. R. Beattie Department of Physiology, Chelsea Polytechnical College, London
W. R. M. Morton Department of Anatomy, Cambridge
A number of cases of non-closure of the ductus arteriosus in various mammals have been reported (Giepel, Schmutzer, Hare and Orr, Segall and Mirsky), but little is known about the histology of the non-closed ductus in mature animals. Recent work on the normal physiological closure of the ductus arteriosus in sheep by Barclay, Barcroft et al. (1938) indicates that it is a rapid phenomenon occurring almost immediately after delivery. Boyd (1937) has shown that there is a marked histological difference between the structure of the ductus arteriosus and the adjacent parts of the pulmonary artery and aorta. This difference, which consists of a marked predominance of smooth muscle fibres in the ductus arteriosus as compared with the relatively non-muscular condition of the other two vessels, suggests that the structure of the former is the anatomical basis of its sudden constriction at birth, i.e. that its apparently physiological closure, as contrasted with anatomical obliteration, is due to contraction of this musculature. It would be very interesting, therefore, to know if any difference in the structure of the wall of the ductus arteriosus, e.g. paucity of muscle, is present in those cases where there is non-closure in the adult.
The following note is a record of the histological findings in such a case, with some observations on these findings. The material consisted of the heart and vessels of a mature sheep, which was obtained by one of us (F. J. R. B.) for routine class work, so that over 24 hr. elapsed before the vessels were fixed in formalin. There was no history of the condition of the sheep during life. The heart shows a patent foramen ovale, guarded by a very well developed sleeve-like valve which projects into the left auricle for a distance of 2 cm. There is a well-marked patent ductus arteriosus, 0-9 cm. in length, running from the pulmonary artery (from a point just proximal to its bifurcation) to the aorta. The ductus arteriosus continues distally for a further 0-5 cm., incorporated in the aortic wall, before opening into the aortic lumen. The relevant vessels were sectioned and stained for muscle, elastic and collagen fibres. The material did not take the differential stains well, owing to the post-mortem changes which had occurred before fixation.
The aorta shows relatively few bundles of smooth muscle fibres as compared with the number seen in a normal sheep aorta. The muscle fibres are scattered throughout the thickness of the wall instead of being arranged in well-marked bundles occupying the outer half or two-thirds of the wall. The elastic tissue’and collagen seems to be present in about equal amounts, and they constitute the main bulk of the wall. The pulmonary trunk shows slightly more muscle tissue than the aorta, but it is not conspicuous. There is no sign of bundle formation as in the normal pulmonary trunk, which shows considerably more muscle bundles than the normal aorta. Elastic tissue is present, but not so much as in the aorta. Collagen fibres make up the bulk of the wall. The ductus arteriosus shows a very well-marked internal elastic lamina, immediately outside which were about 50-60 layers of muscle, collagen and elastic tissue, arranged concentrically. There appears to be more muscle tissue in the outer layers than in the inner layers, and a greater proportion of muscle in the ductus than in the aorta. Surrounding the outside of the ductus is a very thick layer of elastic fibres.
The probable course of the blood was as follows: Some of the blood from the right atrium passed into the right ventricle and thence to the pulmonary artery as in the normal heart, but some must have passed through the foramen ovale into the left atrium. It is inconceivable that blood passed from the left atrium into the right atrium as the valve guarding the foramen ovale was so complete. Mixed blood therefore entered the left ventricle and aorta. Judging by the large size of the pulmonary trunk prior to its junction with the ductus arteriosus, and its subsequent reduction in size (we cannot use the post-mortem direction of the ductus arteriosus as a guide to its direction during life (Barclay et al.)), it seems reasonable to assume that blood passed from the pulmonary artery to the aorta. This is contrary to what might be expected from a consideration of the normal pressure differences between the two vessels, and also from the assumption that the venous stream has already been divided into two. Considering the structure of the ductus in this case, there is no persistence of the condition present in the ductus of a newly born lamb, but rather there is the appearance of a structure designed to withstand high pressures. Whether this is due to the altered pressure changes in the vessels owing to the cardiac abnormality, or to the absence of the normal amount of smooth muscle at birth (leading to non-closure of the ductus and hence back pressure on the right side of the heart, with consequent failure of closure of the foramen ovale), it is not possible to say.
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Cite this page: Hill, M.A. (2020, August 10) Embryology Paper - Note on a case of patent ductus arteriosus and patent foramen ovale in a mature sheep (1939). Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Paper_-_Note_on_a_case_of_patent_ductus_arteriosus_and_patent_foramen_ovale_in_a_mature_sheep_(1939)
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