Cell biology-Nasopharynx surface showing microvilli on the surface of stratified squamous nasal epithelial cells. The tiny microvilli increase the cell surface area and likely aid in localizing foreign debris coming from the nose detected by immune cells. Mucus secreted by cells in the epithelial lining (not seen) traps foreign objects such as bacteria, preventing them from entering the lungs. SEM X2000.
Blood clot. Coloured scanning electron micrograph (SEM) of a blood clot from the inner wall of the left ventricle of a human heart. Red blood cells (erythrocytes) are trapped within a fibrin protein mesh (cream). The fibrin mesh is formed in response to chemicals secreted by platelets (pink), fragments of white blood cells. Clots are formed in response to cardiovascular disease or injuries to blood vessels. Connective tissue (orange) is also seen.