Rat's nose and blood vessels. Coloured scanning electron micrograph (SEM) of a resin cast of blood vessels in the nose of a rat. The main blood vessel enters the nasal cavity from lower left and branches out to form capillaries branching over the nasal concha (upper left). The nasal concha is a set of scroll-shaped spongy bones that line the nasal passage in vertebrates. The blood vessels supply oxygen and nutrients to the nasal tissues, particularly the mucosa lining the nasal passages. As air enters the nose it is warmed by the blood vessels that line the nasal cavity. The cast was made by injecting resin into the blood vessels. The surrounding tissues were then chemically digested.