Answer to Question #167678 in Human Anatomy and Physiology for Jasmine Elfaqir

Question

There is a papillary pattern on the skin of the finger, but it is not on the skin of the face. What features of the structure of the skin can explain this?

Answer 1

The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis provides tensile strength and elasticity to the skin through an extracellular matrix composed of collagen fibrils, microfibrils, and elastic fibers, embedded in hyaluronan and proteoglycans.

It harbors many mechanoreceptors (nerve endings) that provide the sense of touch and heat through nociceptors and thermoreceptors. It also contains the hair follicles, sweat glands, sebaceous glands, apocrine glands, lymphatic vessels and blood vessels. The blood vessels in the dermis provide nourishment and waste removal from its own cells as well as for the epidermis.

The dermis is tightly connected to the epidermis through a basement membrane and is structurally divided into two areas: a superficial area adjacent to the epidermis, called the papillary region, and a deep thicker area known as the reticular region.

The dermis extends up into the epidermis in structures called dermal papillae. These have two functions.

• First, they help adhesion between the dermal and epidermal layers.
• Second, in areas of thick skin like this, they provide a large surface area, to nourish the epidermal layer.

The epidermis is composed of the outermost layers of the skin. It forms a protective barrier over the body's surface, responsible for keeping water in the body and preventing pathogens from entering, and is a stratified squamous epithelium, composed of proliferating basal and differentiated suprabasal keratinocytes.

Due to the proportion of dermis and epidermis, there are two types of skin - thin skin and thick skin. Thick skin is only found in areas where there is a lot of abrasions - such as palms, fingertips, and soles of feet, while thin skin is a hairy type, which could be found in all other areas of the body. So at thick skin, there is a big amount of epidermis consist of 5 layers of skin and a comparably low amount of dermis. In this case, the dermis forms noticeable extensions. But at thin skin, there is an opposite situation with a low amount of epidermis with only 3 layers and a bigger amount of dermis, which forms a smooth surface.