dermis Flashcards
(8 cards)
dermis
The dermis is your “hide.” It is a strong, stretchy envelope that helps to bind the body together. When you purchase leather goods (bags, belts, shoes), you are buying the treated dermis of animals.The connective tissue making up the dermis consists of two major regions—the papillary and the reticular areas (Figure 4.5), which are composed of areolar and dense irregular connective tissue, respectively. Like the epidermis, the dermis varies in thickness. For example, it is particularly thick on the palms of the hands and soles of the feet but is quite thin on the eyelids.
pappilary layer
The papillary layer is the superficial dermal region. It is uneven and has peglike projections from its superficial surface, called dermal papillae (pah-pil′e; papill = nipple), which indent the epidermis above. Many of the dermal papillae contain capillary loops, which furnish nutrients to the epidermis. Others house pain receptors (free nerve endings) and touch receptors. On the palms of the hands and soles of the feet, the papillae are arranged in definite patterns that form looped and whorled ridges on the epidermal surface that increase friction and enhance the gripping ability of the fingers and feet. Papillary patterns are genetically determined. The ridges of the fingertips are well provided with sweat pores and leave unique, identifying films of sweat called fingerprints on almost anything they touch.
recticular layer
The reticular layer is the deepest skin layer. It contains dense irregular connective tissue, as well as blood vessels, sweat and oil glands, and deep pressure receptors called lamellar corpuscles.
cutenous sensory receptors
Other cutaneous sensory receptors, which are actually part of the nervous system, are also located in the skin. These tiny sensors, which include touch, pressure, temperature, and pain receptors, provide us with a great deal of information about our external environment. They alert us to sources of heat or cold, or the tickle of a bug exploring our skin. In addition to detecting stimuli from our environment, phagocytes found here (and, in fact, throughout the dermis) act to prevent microbes that have managed to get through the epidermis from penetrating any deeper into the body.
found in dermis
Both collagen and elastic fibers are found throughout the dermis. Collagen fibers are responsible for the toughness of the dermis; they also attract and bind water and thus help to keep the skin hydrated. Elastic fibers give the skin its elasticity when we are young. As we age, the number of collagen and elastic fibers decreases, and the subcutaneous tissue loses fat. As a result, the skin loses its elasticity and begins to sag and wrinkle.
thermoregulation
Dermis has lots of blood vessels.
When you’re hot, blood vessels (capillaries) in the dermis dilate (get bigger) and fill with warm blood — this makes your skin red and warm. This helps release heat from your body.
When you’re cold, those blood vessels constrict (narrow) so less blood flows through the skin, which helps keep your body heat inside.
This process is called thermoregulation — the skin helps keep your body temperature balanced!
ulcers
Any restriction of the normal blood supply to the skin results in cell death and, if severe or prolonged enough, skin ulcers. Decubitus (de-ku′bĭ-tus) ulcers (bedsores) occur in bedridden patients who are not turned regularly or who are dragged or pulled across the bed repeatedly. The weight of the body puts pressure on the skin, especially over bony projections. Because this pressure restricts the blood supply, the skin becomes pale or blanched at pressure points. At first, the skin reddens when pressure is released, but if the situation is not corrected, the cells begin to die, and small cracks or breaks in the skin appear at compressed sites. Permanent damage to the superficial blood vessels and tissue eventually results in degeneration and ulceration of the skin (see the photos).
dermis and receptors
The dermis also has a rich nerve supply. As mentioned earlier, many of the nerve endings are designed to detect different types of stimuli (pressure, temperature, pain, etc.), then send messages to the central nervous system for interpretation. (We discuss these cutaneous receptors in more detail in
