American Academy of Professional Coders (AAPC) 2026 – 400 Free Practice Questions to Pass the Exam

The stratum spinosum, also known as the "prickle cell layer," is primarily composed of keratinocytes, which are often referred to as "prickle cells" due to their spiny appearance under a microscope. This spiny appearance is a result of desmosomes—the intercellular junctions that connect keratinocytes—holding these cells together and providing structural integrity. As the cells in this layer undergo maturation, they become more flattened and accumulate keratin, preparing them for the subsequent layers of the epidermis.

Additionally, the stratum spinosum contains Langerhans cells, which play a crucial role in the immune response by alerting the body to pathogens that may penetrate the skin. This layer is vital for providing strength and flexibility to the epidermis while contributing to the protective barrier of the skin.

In contrast, clear, flat cells are associated with the stratum lucidum, which is found only in thick skin, such as the palms and soles. Pigmented cells, primarily melanocytes, are located within the stratum basale and are responsible for the production of melanin, which gives skin its color. Smooth muscle cells are not part of the epidermis; they are found in various structures within the body