Please read Unit 3 – Introduction to Integument prior to completing the activities in this chapter.

Introduction to Thick Skin (plantar or palmar skin)

Thick skin is found mainly on the bottoms of the feet (plantar surface) and palms (palmar surface).  Thick skin can also develop in other areas exposed to chronic high pressure and/or friction such as skin covering the elbows or knees.  Elevated pressure and/or friction in these areas increases mitosis of epidermal stem cells in the stratum basale (stratum germinativum) and stimulates increased keratin production by keratinocytes in the stratum granulosum of the epidermis.  This results in a much thicker stratum corneum (superficial layer of dead keratinocytes) in thick skin which helps protect underlying tissues from potential damage.

Another difference between thin and thick skin is the presence of a layer known as the stratum lucidum between the stratum granulosum and stratum corneum of thick skin.  The stratum lucidum is a relatively thin, clear-staining region visible on some microscope slides where keratinocytes are beginning to accumulate large amounts of keratin.  Since thick skin is located in areas exposed to high pressure and/or friction, it typically does not possess hair follicles, arrector pili muscles, or sebaceous glands.

Tutorial:  Use the image slider below to learn more about the characteristics and layers of thick skin (plantar or palmar skin). 

Tutorial:  Use the image slider below to learn more about the characteristics and layers of thick skin (plantar or palmar skin). 

Microscopy:  Use the image slider below to learn how to use a microscope to study a microscope slide of thick skin (plantar or palmar skin).

Tutorial:  Use the hotspot image below to learn more about the characteristics and layers of thick skin (plantar or palmar skin). 

Tutorial:  Use the image slider below to study numerous unlabeled images of thick skin (plantar or palmar skin).