Metastatic Cancer – Melanoma
Video Lessons on Normal Anatomy and Histology of Skin
Lyz Boyd; Helen Dyck; and Jennifer Kong
Learning Objectives
By the end of this section, you will be able to:
- List the three layers of skin and the cells that occupy each layer.
- Identify the three layers of skin and cells which are protein rich vs. poor or alive vs. dead based on H&E staining.
Skin, like all tissues, is made out of multiple cells attached together to serve a common function. Thus, there can be a variety of different cells residing within the same tissue.
1 minute video of normal skin anatomy
Skin is divided into 3 major layers: the epidermis, dermis, and hypodermis. This chapter will focus predominantly in the epidermal layer as this is where melanocytes reside.
1 Minute Video of Normal Skin Anatomy by Lyz Boyd, licensed under All Rights Reserved
Normal skin histology
Presented by Lyz Boyd using a histology slide of H&E stained normal skin (DHPLC e-slide: PATH 304-004)
1 Minute Video of Normal Skin Histology by Lyz Boyd, licensed under All Rights Reserved
- The skin has three layers: the epidermis, dermis & hypodermis (subcutaneous).
- The epidermis is the most exposed layer, comprised mostly of keratinocytes and a minor amount of melanocytes. Keratinocytes are filled with the tough protein keratin, which helps the epidermis be durable. The most exposed layer of the epidermis are layers of dead, keratin-filled keratinocytes histologically evident by its lack of nuclei and strong staining for protein.
- Melanocytes reside in the epidermis on the regenerative layer (i.e. stratum basale). Melanocytes continually produce the protein pigment melanin which provides a physical barrier near the nuclei of living keratinocytes, thus protecting the DNA from UV damage. When the keratinocytes die at the most-exposed layer, the melanin pigment has already degraded as there is no longer any need to protect living nuclei. Thus, the most exposed layer of the skin lacks pigment.
- The thicker dermal & epidermal layers contain large vessels and nerves which help supply the epidermis with nutrients and sensation.
- Stratum corneum
- Stratum granulosum
- Stratum basale
- Stratum spinosum
2. Which of the following is not a function of the hypodermis?
- Protects underlying organs
- Helps maintain body temperature
- Source of blood vessels in the epidermis
- A site for long-term storage
3. Cells of the epidermis derive from stem cells of the stratum basale. Describe how the cells change as they become integrated into the different layers of the epidermis.
Answer Key
- Stratum basale
- Source of blood vessels in the epidermis
- As the cells move into the stratum spinosum, they begin the synthesis of keratin and extend cell processes, desmosomes, which link the cells. As the stratum basale continues to produce new cells, the keratinocytes of the stratum spinosum are pushed into the stratum granulosum. The cells become flatter, their cell membranes thicken, and they generate large amounts of the proteins keratin and keratohyalin. The nuclei and other cell organelles disintegrate as the cells die, leaving behind the keratin, keratohyalin, and cell membranes that form the stratum lucidum and the stratum corneum. The keratinocytes in these layers are mostly dead and flattened. Cells in the stratum corneum are periodically shed.
Outermost tissue layer of the skin.
Layer of skin between the epidermis and hypodermis, composed mainly of connective tissue and containing blood vessels, hair follicles, sweat glands, and other structures.
Connective tissue connecting the integument to the underlying bone and muscle.
Cells that produce the brown/black pigment melanin. They are located in select parts of the body, but most visible at the bottom layer (the stratum basale) of the skin's epidermis and the middle layer of the eye (the uvea)
