Effects of blood vessels in a living tissue subjected to heat transfer radiation are investigated. The heat transfer between blood flowing inside vessels and the tissue around the vessels is considered. For this purpose, temperature distributions in three-dimensional space are evaluated by solving the continuity, momentum and energy equations, numerically. Blood is considered as non-Newtonian fluid using the power law model. A precise and realistic model for skin and blood vessels is used to analyze the transient heat transfer through skin. Skin is considered as a three-dimensional structure including three layers embedded with counter-current vessels, with optimally branched circular cross sectional areas. Results for temperature distribution show that arteries act as heat sinks while veins carry heat out of the upper part of the tissue. It is observed that the role of blood for cooling the tissue under radiation is more significant than what was assumed in previous studies. Also, skin burn degree induced by radiation is evaluated. It was seen that skin burn is a function of time and temperature. Arteries restrict the skin burn-depth while the veins act oppositely. (C) 2014 Elsevier Ltd. All rights reserved.