The Dermis

The Dermis has its own 2 Layers

The dermisThe thick inner layer of the skin that contains blood vessels, nerves, and connective tissue. is the gelatinous body stocking full of waterThe universal solvent essential for life.. It lies deepAway from the surface of the body. to the epidermisThe outermost layer of the skin, made of stratified squamous epithelium.. The epidermis forms a hard candy shell with its many layers and dead cellsThe basic structural and functional units of life.. In the picture you see here, the dermis is all pink, no purple. Epithelial tissue that lines an open space usually takes up a purple color with the H&E stain used.

The dermis is full of collagenA structural protein in the dermis that provides strength and elasticity. bundles that take up that pink stain. These collagen bundles bind water, making your dermis a huge water reservoir. Skin health can be maintained by drinking lots of water. If you want to continue to look young, lay off the coffee and drink the water! The water content of the dermis creates a strange effect called an artifact. This occurs when it is dried and made into histological slides. The water of the dermis evaporates. As a result, the dermal tissue on the slide starts to crack and blisterA fluid-filled sac between layers of skin caused by friction, burns, or infections.. It sometimes distorts in shape as the water evaporates off. The collagen bundles of the dermis tear away from each other when the water evaporates. This leaves cracks characteristic of the dense irregular tissue found in the bulk of the dermis. Keep this in mind as we view histological slides in this class. Tissues are dried to make these slides. Water evaporates.

The Papillary Layer

Whereas the epidermis had all those strata, the dermis has its own two layers. The papillary layerhe upper layer of the dermis that contains blood vessels and sensory receptors. is a thin layer of areolar tissue. It lies just deep to the border of the epidermis and the dermis. Papilla means nipple; this dermal sub-layer is named for these projections called dermal papillaUpward extensions of the dermis that interlock with the epidermis, forming fingerprints.. These project superficially into the epidermis and increase the contact surface area between the dermis and the epidermis. We found that this enhances the epidermis’s ability to attach to the dermis. It improves the diffusionPassive movement of molecules from areas of high to low concentration. of oxygen and glucoseA simple sugar that is the main source of energy for cells. from the blood vessels in the dermis to the avascularTo be devoid of blood capillaries. Epithelial tissue is avascular, kind of like a cap of dead cells epidermis.

Free nerve endings exist in this superficialNear the surface of the body. layer of the dermis. These dead ends of nerves can detect temperature. Their placement in the papillary layer allows assessment of the temperature of the epidermal cells to determine the outside temperature. Free nerve endings are also found in many other organs.

Phagocytes roam around the papillary layer of the dermis. The term phagocyte means “eating cell.” These white blood cells roam the papillary layer of the dermis and engulf anything they don’t recognize via endocytosisThe process of a cell engulfing material by wrapping its membrane around it.. They transport their catch to a lymph node. There, it undergoes further assessment of the threat it poses and determines the immune system mobilization needed. Macrophages are also present; these cells engage in extensive eating. Phagocytes are in the dermis. They roam the border of the epidermis and the dermis to catch any invaders. This happens before the invaders can penetrate deeper into the dermis and potentially contact a blood vessel.

The Reticular Layer

The word reticular means network or web.  We’ve seen this word before and it is used a lot as an adjective in many areas of the body.  The reticular layerhe deeper portion of the dermis, containing collagen and elastin fibers for skin strength. of the dermis is the deepest 80%.  In many areas of the body, the reticular layer contacts the hypodermisThe layer beneath the dermis, composed of connective and adipose tissue, providing insulation and cu at the deepest boundary.  This layer results in the pinkish, torn-tissue-looking appearance of the dense irregular connective tissue. 

It’s in the dermis that we will also see specific sensory receptorsProteins located on the surface or inside cells that bind specific molecules (e.g., neurotransmitter for pressureThe force exerted by gases in the respiratory system, affecting airflow and gas exchange.. We will also find sensory receptors for sensation. Arteries, veinsBlood vessels that return deoxygenated blood to the heart (except pulmonary veins, which carry oxyge, and lymphatic vessels are present too.   If you are unsure where a certain structure is in skinThe body’s largest organ, providing protection and regulation., guess dermis.  It’s probably right!. 

Aging in the Dermis

The dermis is covered by the epidermis. However, aging-related changes can be seen on the surface of the skin. The epidermis acts like a stocking that dips and rises with the valleys and hills of the dermis. Wrinkles occur as collagen breaks down and largely disappears from the reticular layer of the dermis. Why does collagen break down, you ask? Water. As you age, dehydrationA condition in which fluid loss exceeds intake, leading to a decrease in total body water. becomes more common. Your dermis, as a significant water reservoir, suffers the most damage from dehydration. This differs from stretch marks, which do not result from water loss.

Stretch marks occur when collagen bundles tear. Have you ever seen skin come off chicken and tear the muscle beneath? Those are collagen fibers being ripped apart. Stretch marks happen with tugging and pulling of the skin. This can result from weight gain but can also arise from poorly fitting prosthetic devices. I knew someone with a prosthetic leg. It suctioned to the hip. This led to stretch marks all over his hip skin. These marks were caused by the downward force of the prosthesis. Can you make stretch marks go away, you ask? There is no miracle cure, but treating your skin well is a start. The flow within your skin moves from deep to superficial. Cells and nutrients travel in that direction. Putting on cream provides limited help to your dermis since it must penetrate through all your epidermal layers. Eating well, along with taking biotin and vitamins, can be beneficial. It is essential to provide the dermis with what it needs from the inside.