Jejunal microvasculature of the llama and alpaca.

The vasculature of the jejunum was studied in 6 llamas and 1 alpaca, using a combination of microangiography, standard light microscopy, and vascular cast imaging. The casts were examined by use of scanning electron microscopy and low-power dissecting microscopy. After administration of 40,000 IU of heparin, all animals were euthanatized by administration of an overdose of sodium pentobarbital. Three sections of jejunum and their respective arcuate vessels were isolated from each animal. One section was immediately placed in formalin for later H&E staining. The second and third sections were placed in warm saline solution, and the vasculature was flushed free of all blood by repeated infusions of the solution. Once flushed of all blood, one section was infused with a radio-opaque medium and subsequently evaluated by microangiography, and the remaining section was perfused with a methylmethacrylate polymer for creation of vascular casts. The arcuate vessels branched into extensive primary and secondary arcades prior to giving rise to the marginal rete. Muscular arteries and small veins left the marginal rete and penetrated the tunica serosa and tunica muscularis to provide nutrients or drain the mesenteric angle, respectively, or entered into the circumferential submucosal network. The primary penetrating vessels in the submucosa formed an extensive submucosal plexus that supplied the tunica serosa, tunica muscularis, and tunica mucosa. The primary penetrating vessels anastomosed with vessels from oral and aboral sections and with their counterparts from the opposite side at the antimesenteric border.(ABSTRACT TRUNCATED AT 250 WORDS)