Thorax: first published as 10.1136/thx.20.1.76 on 1 January 1965. Downloaded from Thorax (1965), 20, 76. An x-ray microscopic study of the vasa vasorum of the normal human aortic arch JOHN A. CLARKE From the Department of Anatomy, University of Glasgow Descriptions of the vasa vasorum of the aortic plexus and the patterns of distribution to the inner wall vary. The main papers are concerned with layers of the vessel wall. the intramural vasculature of the descending aorta, This work is concerned with a description of the little reference being made to the aortic arch. The vasa vasorum in the normal human aortic arch, first observation on the vasa vasorum of the aortic using the Coslett-Nixon x-ray projection micro- wall is attributed to Willis (Haller, 1757). scope. This enables a study of the pattern and In a review of -the literature, Ramsey (1936), distribution of the vasa vasorum in freshly injected recording the descriptions of the principal nine- specimens to be made, in contrast to the routine teenth century investigators (Risse, 1853 ; Gimbert, histological and clearing techniques of previous 1865; Plotnikow, 1884), showed that interpreta- investigators. tions of injected and routine histological speci- mens of the aortic wall differed on the depth the MATERIAL AND METHODS intramural vessels penetrated. copyright. From an examination of animal aortae injected Fifty normal post-mortem aortic arches were with India Woodruff examined within eight hours of death from hearts ink, (1926) concluded that in the age group 15-80 years. the aortic vasa arose from collateral branches of The microcirculation in the aortic wall was the aorta, to be distributed to the adventitia and demonstrated by injecting micropaque at physio- inner media. logical pressures, the arterial side through the http://thorax.bmj.com/ Robertson (1929), injecting human thoracic innominate and bronchial arteries, the venous side aortae and animal aortae with coloured cellulose, through the bronchial veins. demonstrated networks of adventitial vessels and X-ray projection micrographs of full thickness concluded that the outer third of the media in the aortic wall and 1 mm. thick sections were taken on human aorta was vascularized. Ilford contrasty plates with an exposure time of 10 By injecting the aortic wall with Higgins ink and minutes. 'The microscope was operated at 15 kV and 40 mA with a copper target providing the clearing in glycerine or by the Spalteholz method, x-radiation. Winternitz, Thomas, and LeCompte (1938) revealed vascular patterns in the outer media of OBSERVATIONS on September 29, 2021 by guest. Protected the human and animal arterial wall and demon- strated intimal vascularization in atheromatous From an examination of the micrographs it was plaques. concluded that the arterial supply to the wall of Geiringer (1951), from an examination of frozen the aortic arch originated from the ostium of the sections of human aorta, concluded that the innominate artery and the terminal branches of normal aortic intima was avascular, only acquir- the bronchial arteries. ing a secondary blood supply if it attained a It was found that tightly coiled arterioles, 80 to critical thickness of 0-5 mm. 100 u in diameter, originated from the ostium of The introduction of microradiographic tech- the innominate artery to be distributed to the niques in arteriography (Barclay, 1947) permitted adventitia of the summit of the aortic arch (Figs. 1 the study of the microcirculation without routine and 2) while the sides and concave aspect of the histological preparation of tissues. de Sousa and arch were supplied by sinuous adventitial Alvares (1960) and Nylander and Olerud (1960), arterioles, 60 to 80 IL in diameter, from the employing microradiography, demonstrated the bronchial arteries (Figs. 3 and 4). vasa vasorum of the aorta and inferior vena cava From the adventitial plexus, arterioles 60 to 80 ,u in the dog, revealing the adventitial arteriolar in diameter penetrated the deep layers of the 76 Thorax: first published as 10.1136/thx.20.1.76 on 1 January 1965. Downloaded from An x-ray microscopic study of the vasa vasorum of the normal human aortic arch 77 r t OF_/ r .jiI14^~~~~~~~~~O' /-fr IF 3-0 FIG. 1 FIG. 2 copyright. I-a ""64~~ http://thorax.bmj.com/ on September 29, 2021 by guest. Protected V V b -* FIG. 3 FIG. 4 For explanation of Figs 1 to 12 see p. 80. Thorax: first published as 10.1136/thx.20.1.76 on 1 January 1965. Downloaded from 78. John A. Clarke v. ._....a 5 :<A. t .. X::e m L copyright. FIG. 5 ]FIG. 6 j: ' : http://thorax.bmj.com/ .B.# #; W ::. :: C .. 1 P6. \ \*, \ \ on September 29, 2021 by guest. Protected .. b S. ......#. ic. &.. M: I. t '.: 4. .k: _.......... -*;. .:: it >. s_ :, lb, ;6 v.. t...11l w_ \ K N :S *. t _. f X . __ Y .. _W 4 FIG. 7 FIG. 8 .X':..> Thorax: first published as 10.1136/thx.20.1.76 on 1 January 1965. Downloaded from An x-ray microscopic study of the vasa vasorum of the normal human aortic arch 79 I_ copyright. FIG. 9 FIG. 10 http://thorax.bmj.com/ on September 29, 2021 by guest. Protected VI It , (s 4 Fa llT A I; 4 F'IG. II FIG. 12 Thorax: first published as 10.1136/thx.20.1.76 on 1 January 1965. Downloaded from 80 John A. Clarke EXPLANATION OF PLATES All figures, except Figs. 5, 6, and 9, are of full thickness aortic wall. Long axis of aorta (1-a). FIG. 1. Micrograph of the aortic arch. Note the arteriole FIG. 8. Micrograph ofthe side (S) and concave aspect (C) (a) originatingfrom the ostium (o) ofthe innominate artery ofthe aortic arch. Note the dense venous network (n) in the to be distributed to the adventitia (v). Wall of ostium (w), adventitia (v), draining into tributary (t) of the bronchial x20. veins, x25. FIG. 2. Micrograph ofthe summit ofthe aortic arch. Note FIG. 9. Micrograph of 1 mm. thick longitudinal section the coiled arterioles (a) in the adventitia (v), x 45. ofthe aortic arch. Note the origin of the venous plexus (p) FIG. 3. Micrograph ofthe side ofthe aortic arch. Note the in the inner third of the media (m) draining into tributaries terminal branch ofthe bronchial artery (b) approaching the (t) of the adventitial veins (v). Terminal arteriovenous adventitia (v) to divide and distribute sinuous arterioles (a), anastomoses (a-v). Outer two-thirds of media (m,). Intima x 30. (I), x30. FIG. 4. Micrograph of the concave aspect of the aortic FIG. 10. Micrograph of the proximal end of the aortic arch. Note the sinuous arterioles (a) in the adventitia (v), arch (P) and the distal end ofthe ascending aorta (D). Note x 70. the arterioles (a) in the adventitia (v) ofthe aortic arch, and FIG. 5. Micrograph of I mm. thick longitudinal section the arterioles (aj) in the adventitia (v1) of the ascending of the aortic arch. Note the arteriole (a) penetrating the aorta. Avascular zone (z), x 20. deep layers of the adventitia (v) to divide in the outer third of the media (m), x 50. FIG. 11. Micrograph of the distal end of the aortic arch FIG. 6. Micrograph of 1 mm. thi!k transverse section of (D) and the proximal end of the thoracic aorta (T). Note the aortic arch. Note the terminal arterial distribution (a) the arterioles (a) in the adventitia ofthe aortic arch (v) and in the outer two-thirds of the media (m). Inner third of the arterioles (al) in the adventitia (vl) of the thoracic the media (m1) is avascular. Intima (I). Lumen (L1), x 50. aorta, x 20. FIG. 7. Micrograph ofthe summit oJ the aortic arch. Note FIG. 12. Micrograph of the summit of the aortic arch, copyright. the sparse irregular venous network (n) in the adventitia (v), aged65 years. Note the increased coiling (c) ofthe arterioles x 30. (a) in the adventitia (v), x 20. http://thorax.bmj.com/ adventitia, bifurcated, and formed a secondary DISCUSSION plexus of vessels 10 to 20 ,u in diameter in the outer two-thirds of the media (Figs. 5 and 6). The present study has demonstrated that there is It was evident from the micrographs that the an extensive vascular supply to the aortic wall, the adventitial arterioles and their immediate branches general features of which are shown in Fig. 13. showed coiling, which was most marked on the Winternitz et al. (1938) concluded that, whereas summit of the aortic arch (Fig. 2). the intima was only vascularized in 'arterio- From an examination of the micrographs show- sclerosis', the media of the ascending aorta con- on September 29, 2021 by guest. Protected ing the venous side of the microcirculation, it was concluded that there was a plexus of veins in the adventitial layer of the aortic arch, predominantly on the sides and concave aspect (Figs. 7 and 8). v.2 Arranged irregularly, these adventitial venous channels were 100 to 140 yu in diameter and drained into tributaries of bronchial veins (Fig. 8). br. F. A The tributaries of the adventitial venous network A originated in the aortic wall at the junction of the intimal and medial layers, thus appearing closer br. art. to the aortic lumen than the arteries. Coalescing FIG. 13. Diagram of the arterial supply to the aortic arch in an irregular pattern, these tributaries traversed (A). Note terminal branch ofthe bronchial artery (br. art.) the thickness of the aortic wall to drain into the distributing arterial vasa (v.1) to the side of the arch, and adventitial venous network (Fig. 9). arterial vasa (v.2) originatingfrom the innominate artery to No injection medium entered the intima in any supply the summit of the arch.