PATTERNS OF THE A-V PATHWAYS 



9 J 7 



arterioles, a name given to them by Seymour (109). 

 The anastomoses were seen to contract to complete 

 closure. 



Microscopic observations of cochlear blood vessels 

 in living guinea pigs were reported by Perlman & 

 Kimura (95, 96) in 1955. Special attention was given 

 to the small vessels of the spiral ligament and the 

 stria vascularis. The quartz rod technique was used 

 after the cochlea was fenestrated in the fourth turn. 

 The fenestra was o. 1 to 0.2 mm' 2 and exposed the 

 spiral ligament on the lateral wall of the cochlear 

 duct as well as the stria vascularis. Perlman and 

 Kimura were certain that all vessels in the field were 

 visible to them and that all the basic units of a vascu- 

 lar bed were present. The identification of the various 

 components was based on the diameter, the wall 

 thickness, shape of the vessels, the rate and direction 

 of flow, and the presence of smooth muscle cells and 

 vasomotion. Numerous anastomoses between all 

 types of vessels were seen, but the distribution and 

 direction of flow from the radiating arteriole to the 

 collecting venule suggested a segmental blood supply. 



The arterioles of the spiral ligament were seen to 

 branch into a number of different vessels. A small 

 branch at right angles to the radiating arteriole was 

 seen to run parallel to the cochlear duct in the upper 

 portion of the spiral ligament. It anastomosed with a 

 similar vessel from an adjacent arteriole. 



Another branch was seen that crossed the under- 

 lying stria vascularis and emptied into the collecting 

 vein below the cochlear duct. This type of vessel, 

 regularly seen in the area, has no branches, is narrow 

 and straight, and has a rapid blood flow. It has 



ft. COCHLEAE 

 PROPRIA 



H .V. SPIRALIS 



'/■ POSTERIOR 



fig. 19. Segment of cochlea showing relation of exposed 

 vessels to the cochlear duct and the main trunks in the modiolus. 

 [From Perlman & Kimura (95).] 



smooth muscle cells regularly distributed along its 

 walls. The authors have called this vessel an arterio- 

 venous arcade. (See figs. 19 and 20.) 



Another branch of the radiating arteriole with a 

 uniform diameter extends over the underlying stria 

 vascularis, has no branches, and ends at the level of 

 the spiral prominence just below the stria vascularis. 

 The vessel with which the branch connects runs paral- 

 lel to cochlear duct and tributaries from it join collect- 

 ing venules of the spiral ligament. The blood vessels in 

 the stria vascularis are at right angles to the radiating 

 arteriole, the collecting veins, and the arteriovenous 

 arcade. 



The last branch from the radiating arteriole is the 

 one which enters the stria vascularis. Diameters of 

 the strial vessels are usually larger than the diameters 

 of the radiating arteriole or arteriovenous arcades. 

 Strial vessels do not have a regular distribution of 

 smooth muscle cells and were not seen to contract. 



The vessel in the spiral prominence is independent 

 of the stria vascularis, being directly supplied by a 

 branch from the radiating arteriole. A large number 

 of tributaries leave this vessel to join the collecting 

 vein. Anatomically, it seems to have the qualifications 

 of a capillary, being small in size and devoid of 

 smooth muscle cells, and having a slow rate of blood 

 flow. It shows no vasomotion. 



In commenting on the vascular pattern, Perlman 

 and Kimura state that the segmental type of blood 

 flow suggests that interference with function may be 

 localized. Interruption of flow in a radiating arteriole 

 of an arteriovenous arcade may occur while flow 

 continues in the underlying stria vascularis. Flow in 

 the stria vascularis may cease while active flow con- 

 tinues in the radiating arteriole, arteriovenous arcade, 

 spiral prominence vessels, and venules. The presence 

 of arteriovenous arcades in the spiral ligament sug- 

 gests a possible regulatory mechanism for controlling 

 flow in the stria as well as affording anastomotic 

 channels to insure continuity in blood flow along the 

 spiral ligament. 



Perlman believes that the strial vessels, the arterio- 

 venous arcade, and the spiral prominence vessels 

 have functional roles. The strial vessels may be called 

 capillaries with regard to their position, the fact that 

 they have the lowest blood flow rate, and the fact 

 that they have no smooth muscle cells in their walls. 

 The decrease in the rate of blood flow from the radiat- 

 ing arteriole to these capillaries of the stria vascularis 

 is large and abrupt. The final exchange of diffusible 

 substances probably occurs in these vessels. 



The role of the cochlear blood vessels in the absorp- 



