Dyes used in the H&E stain have an amazing ability to stain each cell and structure in tissue, differentiating each component. Mammalian skin stands out from other stained tissue samples (such as intestinal or nervous tissue) with these distinguishing characteristics:
- Keratin layer (deep pink sheets of flat cells lacking nuclei, if stained properly)
- Dermal papillae (dermal layer extending into the epidermal layer, appearing as finger-like projections)
- Hair follicles (not all skin contains hair, such as hands and feet)
- Melanin pigment (although this brown pigment can also be found in the iris and parts of the nervous system)
Hematoxylin stains the cellular nuclei blue, while eosin stains the non-nuclear cells and supporting structures, such as cytoplasm and collagen, pink/orange. Combined, these dyes assist in recognizing the following cells and layers:
- Epidermal layer consists of the following cells that make up the five sub-layers:
- Basal cells or germ layer: Cells rest on the dermis; blue nuclei are visible and this is where mitosis occurs and cells divide.
- Prickle cell or spiny cell layer: Cells are connected by spines and blue nuclei are visible (see image).
- Granular cell layer: Cells begin losing their nuclei and purple granules are evident.
- Lucid layer: Cell nuclei or granules are no longer evident, leaving a clear pink layer.
- Keratin layer: Consists of deep pink squamous cells that lack nuclei and begin to shed.
- Dermal layer consists of the following cells and structures:
- Dermal papillae: Finger-like projections of connective tissue that reach into the epidermal layer.
- Hair: Begins in the dermal layer and extends into the skin surface (identified as A on the lower image).
- Oil (sebum) glands: Can be found near the hair shaft (identified as B on the lower image).
- Sweat glands: Coiled, tubular structures that produce sweat (identified as C on the lower image).
- Subcutaneous (fatty) layer consists of:
- Fat cells: Insulate and cushion the body.
- Collagen and elastic fibers: Allow flexibility and skin resilience.
- Blood vessels: Transport nutrients and oxygen through blood into the skin.
- Nerves: Allow for the sensory experience in skin.
