![]() ![]() ![]() The hypodermis consists of well-vascularized, loose, areolar connective tissue and adipose tissue, which functions as a mode of fat storage and provides insulation and cushioning for the integument. It is not strictly a part of the skin, although the border between the hypodermis and dermis can be difficult to distinguish. The hypodermis serves to connect the skin to the underlying fascia of the bones and muscles. Collagen injections and Retin-A creams help restore skin turgor by either introducing collagen externally or stimulating blood flow and repair of the dermis, respectively. In addition, collagen binds water to keep the skin hydrated. Collagen fibers provide structure and tensile strength, with strands of collagen extending into both the papillary layer and the hypodermis. Elastin fibers provide some elasticity to the skin, enabling movement. The reticular layer appears reticulated due to a tight meshwork of fibers. ![]() This layer is well vascularized and has a rich sensory and sympathetic nerve supply. Underlying the papillary layer is the much thicker reticular layer, composed of dense, irregular connective tissue. This layer also contains lymphatic capillaries, nerve fibers, and Meissner corpuscles. In addition, the papillary layer contains phagocytes, that help fight bacteria or other infections that have breached the skin. Within the papillary layer are fibroblasts, a small number adipocytes, and an abundance of small blood vessels. This superficial layer of the dermis projects into the stratum basale of the epidermis to form finger-like dermal papillae (see Figure 6.4). The papillary layer is made of loose, areolar connective tissue, which means the collagen and elastin fibers of this layer form a loose mesh. (credit: modification of work by “kilbad”/Wikimedia Commons). The dermal papillae extending into the epidermis belong to the papillary layer, whereas the dense collagen fiber bundles below belong to the reticular layer. Both are made of connective tissue with fibers of collagen extending from one to the other, making the border between the two somewhat indistinct. This stained slide shows the two components of the dermis-the papillary layer and the reticular layer. ![]()
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