Histological Study of Medium Sized Arteries of Neck in Relation With Their Pulse Pressure and Pulsatory Power

Abstract

INTRODUCTION:There are several studies on the microstructure of main arteries of the body but limited have been dealt with the neck arteries. It has been mentioned that the vascular pathologies like the thrombo-embolism, atherosclerosis and infarction are common in the branches of vertebral and internal carotid artery as compared to the branches of external carotid artery. OBJECTIVE: To study the histological structure of the 3 medium sized arteries of neck namely external carotid, internal carotid and vertebral artery, calculation of their mean pulse pressure and pulsatory power and to find any association between them if present. METHOD: Fresh samples of external carotid, internal carotid and vertebral artery each measuring 10mm in length were taken from five cadavers and prepared for histological examination under microscope using orcein and H&E stain. The mean pressure and pulsatory power of these arteries were calculated by taking the measurements such as wall thickness, lumen circumference, arterial wall area, and smooth muscle fibre density in tunica media in that arterial segment. RESULT: The pulsatory power of external carotid artery, internal carotid artery and vertebral artery is found to be 120, 273.3, 400 Joules /heart beat and the mean pressure is 17.1 mm Hg, 27.3 mm Hg and 33.3 mm Hg respectively. CONCLUSION: The thickness of tunica media of an artery is directly proportional to its pulsatory power. The mean pulse pressure, pulsatory power as well the number of smooth muscles fibres in tunica media are more in internal carotid artery and vertebral artery in comparison to external carotid artery. It may be a very important reason why vascular pathologies are less common in branches of external carotid as compare to internal carotid and vertebral artery.

Histological Variations in Various Segments of Vertebral Artery

“…9 Mean of the lumen circumference of VA is 12.2mm; the mean arterial wall thickness 0.25mm. 10 Kornieieva et al (2014) have stated that the mean outer diameter of the VA gradually decreased from 3.9±1.08mm in the vertical extent to 3.4±0.72mm in the oblique course mainly. The diameter was greater in the male on the left, however, right dominating type was revealed in 9% of cases.…”

“…11 Aggarwal et al (2014) have stated that all the vascular pathologies like the thromboembolism, atherosclerosis and infarction are common in the branches of vertebral and internal carotid artery as compared to the branches of external carotid artery. 10 Kornieieva et al (2014) have described that due to significant dilation during the head rotation the V3 became a favourable area of sudden dissections (Sheth TN, 2001; William B, 2012). 5 This segment of the VA possesses number of bends and loops which increased the resistance of blood flow, generating target places for arteriosclerosis, thrombosis and wall calcification.…”

“…10 An abnormally high arterial pressure will undoubtedly increase the load born by the arterial wall. Further Iain MS Wilkinson (1972) observed that as the vertebral artery enters the skull its adventitia and media undergo a significant reduction in thickness, associated with gross diminution or total loss of elastic fibres in these two layers of the artery wall.…”

“…This transformation is most marked in the last 0.50cm extradurally. 10 . Lt VA is larger in diameter (3.75mm) than Rt.…”

From head micro-motions towards CSF dynamics and non-invasive intracranial pressure monitoring

“…the total number of smooth muscle fibers and of the elastic fibers is significantly reduced, and it becomes similar to an elastic artery. For further details see the work of Aggarwal et al 43 .This implies that the intracranial and extracranial arteries display different blood pulse propagation. Moreover, roughly 65% of the blood pulse propagates via the common carotid artery to the internal carotid artery and only 35% contributes via the external carotid artery to the extracranial head circulation 44 .…”