Review Sheet Art-labeling Activity 2 Part A Drag the labels onto the diagram to identify the layers of the epidermis. Reset Help stratum basale stratum corneum stratum lucidum stratum granulosum stratum spinosum
The Correct Answer and Explanation is:
Here is the correct labeling of the epidermal layers from the deepest (bottom) to the most superficial (top):
- Stratum basale
- Stratum spinosum
- Stratum granulosum
- Stratum lucidum (only in thick skin, like palms and soles)
- Stratum corneum
Explanation
The epidermis is the outermost layer of the skin and serves as the body’s first line of defense against environmental harm. It is composed of five distinct layers, each with unique functions and characteristics. From deepest to most superficial, these are:
- Stratum basale (basal layer): This is the bottom layer and consists of a single row of cuboidal or columnar cells. It is where keratinocytes (skin cells) are actively dividing through mitosis. This layer also contains melanocytes, which produce melanin (skin pigment), and Merkel cells for touch sensation.
- Stratum spinosum (spiny layer): Above the basal layer, this layer consists of several layers of keratinocytes that are beginning to produce keratin, a protective protein. The cells appear “spiny” under a microscope due to desmosomes (protein connections) that hold the cells together. Langerhans cells, which help with immune defense, are also found here.
- Stratum granulosum (granular layer): In this layer, keratinocytes begin to die and fill with keratohyalin granules, which are important for waterproofing and strengthening the skin. This layer marks the transition from living to dead cells.
- Stratum lucidum (clear layer): Found only in thick skin, such as the palms of the hands and soles of the feet, this thin, translucent layer provides an extra level of protection.
- Stratum corneum (horny layer): The outermost layer made of many layers of flat, dead keratinocytes. These cells are full of keratin and form a tough, protective barrier that is regularly shed and replaced.
These layers work together to protect the body from pathogens, prevent water loss, and aid in sensation.
