As we closed the chapter dealing with the integumentary system, I decided it would be good to do a brief review on what we learned. The integumentary system is composed of two main layers: the epidermis and the dermis, and there are two types of skin (thin and thick). Thin skin has hair and is more prevalent as opposed to thick skin which is only found in the palms of the hands and the soles of the feet.
The epidermis is the layer of skin that is exposed and is visible. The dermis lies directly beneath the epidermis. Then there is the hypodermis that contains adipose tissue and connective tissue. The epidermis is further divided into 5 layers: stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum basale. The stratum corneum is the layer that varies in thick skin.
The cells of the epidermis are keratinocytes, melanocytes, Langerhans', and Merkel's cells. The epidermis is made up of keratinized stratified squamos epithelium. The keratinocytes are the cells that function to separate the organism from the outside environment. Melanocytes are the cells that secrete melanin. Melanin is important because it is the reason that we are protected from UV radiation. It also produces the pigment of the epidermis. Langerhans' cells are the one's that present antigen's to the immune system. Lastly, Merkel's cells function in stratum basale of the epidermis and they are the most abundant in the fingertips and other places that sensory perception is intense.
http://classroom.sdmesa.edu/eschmid/Chapter5-Zoo145.htm
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