Three types of muscle exist. Smooth muscle lacks striations, is involuntary, and occurs in the digestive system and internal organs. Its cells are tapered and uninucleate. Cardiac muscle is striated and found in the heart. Its cells are quadrangular with a single nucleus and connect to adjacent cells with intercalated disks.
Neuroglial cells are helper cells that support and protect neurons.
The epidermis is made up of stratified squamous epithelium that is produced at the base of the epidermis and that pushes older, keratinized cells outward. Melanocytes within this layer produce melanin. The dermis is fibrous connective tissue with collagen and elastic fibers. Hair follicles in the dermis produce hair shafts. Each follicle has a sebaceous gland that produces lubricating sebum.