The elytra are striated and mottled with silvery whitish scales. It crystallizes in the form of fibrous aggregates, masses, and vertically striated prismatic crystals. Skeletal striated muscle, or "voluntary muscle", primarily joins to bone with tendons. In obliquely striated muscle, the filaments are staggered. There are three types of muscle, skeletal or striated, cardiac, and smooth. It has long striated ducts and short intercalated ducts. Titin is important in the contraction of striated muscle tissues. The gland has short, striated ducts and long, intercalated ducts. Egg cases without a fibrous outer layer can be striated, bumpy, or smooth and glossy. Titin is a large abundant protein of striated muscle. There may be denervation of striated musculature on the electromyogram. The flattened spire is striated and coronated. Schwann also discovered that muscle tissue in the upper esophagus was striated. Pharyngeal muscles are striated muscles of the head and neck. Unlike vertebrates that have both smooth and striated muscles, insects have only striated muscles.