Dense irregular connective tissue and adipose tissue are the major constituents of this region. Fibroblasts (fiber producing cells) and adipocytes (fat cells) abound this reticular region. It has densely packed thick collagen fibers, elastic fibers and reticular (netlike) fibers giving skin structural and tensile strength, elasticity and extensibility. These fibers are arranged in parallel to the surface of the skin. The reticular fibers (reticulin), made of Type III collagen, weave throughout reticular layer giving a net-like appearance and hence the name.
Most of the important epithelial glandular structures of skin like eccrine (sweat) glands, apocrine (scent) glands and Sebaceous (oil) glands are located here.
Blood and lymphatic vessels are found traversing this region carrying nutrients, oxygen and immune cells. The deeper vasculature to the skin, the deep cutaneous plexus, are located at the junction of reticular region and hypodermis.
Nervous tissues and receptors are located in this area transmitting sensations like pain, cold and heat and make skin sensitive to touch. Special nerve cells like Meissner's, Vater-Pacini and Pacinian corpuscles are found here. They are responsible for transmitting the sensations of touch and pressure.
The criss-crossing collagen fibers form Langer's lines, also called as cleavage lines. They correspond to the natural orientation of collagen fibers. Surgical incisions made parallel to Langer's lines may heal better, faster and produce less scarring than those cutting across the fibers. Any damage to reticular layer of dermis can cause scarring.
Image source: http://en.wikipedia.org/wiki/File:Normal_Epidermis_and_Dermis_with_Intradermal_Nevus_10x.JPG
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Current topic in dynamic skin care: Reticular dermis layer.