title: Histomorphometric and sympathetic innervation of the human internal thoracic artery.
abstract: BACKGROUND
  Internal thoracic artery (ITA) is an established arterial graft for the coronary artery by-pass surgery. Special micro-anatomical features of the ITA wall may protect it from age related pathological changes. One of the complications seen after coronary artery bypass grafting is vasospasm. Sympathetic nerves may be involved in vasospasm.
  
  
  OBJECTIVE
  To ascertain the sympathetic innervation of the internal thoracic artery and to assess the effect of aging on this artery by histomorphometry.
  
  
  METHODS
  Fifty-four human internal thoracic artery samples were collected from 27 cadavers (19 male and 8 female) with ages of 19 to 83 years. Samples were divided into three age groups: G1, 19-40 years; G2, 41-60 years; G3, >61 years. Sections (thickness 5 mm) of each sample were taken and stained with hematoxylin-eosin and Verhoeff-Van Gieson stains. Five of fifty-four samples were processed for tyrosine hydroxylase immunostaining.
  
  
  RESULTS
  The thickness of the tunica intima was found to be constant in all age groups, whereas the thickness of the tunica media decreased in proportion to age. Verhoeff-Van Gieson staining showed numerous elastic laminae in the tunica media. Significant differences (p < 0.0001) in the number of elastic laminae were found between G1 with G2 cadavers, between G2 and G3 cadavers and between G3 and G1 cadavers. Tyrosine hydroxylase immunostaining demonstrated sympathetic fibers, located mainly in the tunica adventitia and the adventitia-media border. The sympathetic nerve fiber area and sympathetic index were found to be 0.0016 mm² and 0.012, respectively.
  
  
  CONCLUSIONS
  Histology of the ITA showed features of the elastic artery. This may be associated with lower incidence of Atherosclerosis or intimal hyperplasia in ITA samples even in elderly cases. Low sympathetic index (0.012) of ITA may be associated with fewer incidences of sympathetic nervous systems problems (vasospasm) of the ITA.
  
  
  CONCLUSIONS
  Sympathetic nerve fibers are present in the adventitia of the internal thoracic artery. This is an elastic artery, although anatomically it is considered to be medium-sized. The sympathetic index may be used for analysis of sympathetic nerve fiber-related problems of the internal thoracic artery.
authors: Department of Anatomy, Kasturba Medical College International Center, Manipal University, Manipal, India. msreddy.anat@gmail.com
authors: Sreenivasulu
authors: S
authors: Reddy
authors: Pramod
authors: P
authors: Kumar
authors: Keerthana
authors: K
authors: Prasad
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology; D001026:Coronary Artery Bypass / Q000009:adverse effects; D003329:Coronary Vasospasm / Q000209:etiology; D004547:Elastic Tissue / Q000033:anatomy & histology; D005260:Female; D006801:Humans; D008297:Male; D008323:Mammary Arteries / Q000294:innervation*; D008875:Middle Aged; D009929:Organ Size; D012737:Sex Factors; D013564:Sympathetic Nervous System / Q000033:anatomy & histology*; D017539:Tunica Intima / Q000033:anatomy & histology; D017540:Tunica Media / Q000033:anatomy & histology; D055815:Young Adult