9.5:
Reticular Dermis
In the skin tissue, right below the papillary dermis lies the reticular dermis, which accounts for around 80% of the dermal thickness.
The arteries present in the lower subcutaneous region branch into the cutaneous plexus that supplies blood to the reticular dermis and appendages present in the region, such as hair follicles, sweat glands, and sebaceous glands.
Additionally, stem cells, fibroblasts, macrophages, and mast cells are also present in this layer.
The reticular dermis also contains sensory receptors such as Pacinian corpuscles that are sensitive to pressure, and the Ruffini corpuscles that can detect skin stretching.
The extracellular matrix of the reticular dermis primarily consists of an interwoven network of thick bundles of collagen fibers and elastic fibers. Together they make the skin strong, extendable, and elastic.
Moreover, less dense regions in the extracellular matrix and separations between the collagen bundles form cleavage or tension lines on the skin.
9.5:
Reticular Dermis
The papillary and reticular dermis are the two layers of the dermis. They are made of connective tissue with fibers of collagen extending from one to the other, making the border between the two somewhat indistinct. The dermal papillae extending into the epidermis belong to the papillary layer, whereas the dense collagen fiber bundles below belong to the reticular layer.
Reticular Layer
Underlying the papillary layer is the much thicker reticular layer, composed of dense, irregular connective tissue. This layer is well vascularized and has a rich sensory and sympathetic nerve supply. The reticular layer appears reticulated (net-like) due to a tight meshwork of fibers. Elastin fibers provide some elasticity to the skin, enabling movement. Collagen fibers provide structure and tensile strength, with collagen strands extending into the papillary layer and the hypodermis. In addition, collagen binds water to keep the skin hydrated. Collagen injections and Retin-A creams help restore skin turgor by either introducing collagen externally or stimulating blood flow and dermis repair.
This text is adapted from Openstax, Anatomy and Physiology 2e, Section 5.1: Layers of the Skin