Dermis Structure & Inflammatory Skin Disease (wikispace) Flashcards
Identify the structural components of the dermis.
The dermis contains blood vessels, nerves, and cutaneous appendages (hairs, sweat glands/ducts, etc.) that are important to the structure and function of the skin as an organ.The dermis may be further subdivided into two zones: a) the papillary dermis (located immediately beneath the epidermis), and b) the reticular dermis located deeper in the tissue.Dermal matrix is a term often used to describe the admixture of collagen fibers, elastic fibers and ground substance all of which are synthesized by dermal fibroblasts.The skin appendages, also known as adnexal structures, is a term used by dermatopathologists to refer to the hair follicles, sebaceous glands (oil glands), and sweat glands found in the skin that are vital to protection and homeostasis.
Distinguish between the types of collagen relevant to the skin
Collagen is a key component of the dermis that provides most of the tensile strength of the skin.Collagen I – This form comprises >85 wt. % of the adult dermis. It is also a major component of bone.Collagen III – This type of collagen comprises a large part of the fetal dermis but is not a major portion of the adult dermis.Collagen IV – This form is found in high concentration in the “basement membrane zone” which is present in the dermoepidermal junction. It is also more prominent around vesselsCollagen VII – This form is found in the anchoring fibrils which are used by the body to attach the epidermis to the dermis.
Understand the function of elastic fibers in the skin.
Elastic fibers provide the skin with resiliency. Roughly put, resiliency is the ability of the skin to be distorted but then return to its original shape. Elastic fibers are much smaller than collagen fibers.
Be familiar with the ground substance components of the dermis
Ground substance is a general term for a gelatinous material intercalated between and amongst the collagen bundles, elastic fibers, and appendageal structures of the dermis. It consists principally of two glycosaminoglycans: hyaluronic acid and dermatan sulphate. Remember that glycosaminoglycans are complex molecules made up of proteins and sugars, and are capable of absorbing >10,000x their weight in water.With the help of other compounds, called fibronectins (glue”) this gel-like mass functions like a sponge. Crudely put under pressure it can expel bound water and then take it up again. This process helps to facilitate nourishment of the overlying epidermis by easily allowing a water-based environment for diffusion.The ground substance is constantly being destroyed by enzymes like hyaluronidase and then renewed via production from fibroblasts.
Identify disorders associated with defects in collagen and elastin
Scurvy: Without vitamin C, the collagen fibers will not attain their final desired strength. As a result, minor wounds will fail to heal, hair will grow abnormally, and the blood vessels will be quite fragile due to inadequate support from the surrounding collagen.Ehlers-Danlos syndrome (EDS) is a group of related disorders of collagen synthesis.The most common acquired disorder of elastic is solar elastosis. Over a lifetime, a person accumulates significant sunlight exposure, and this exposure leads to degeneration of the elastic fibers. These collagen bundles become dystrophic tend to “clump” and aggregatePseudoxanthoma elasticum (PXE), which is caused by a mutation in a gene encoding for part of the “multidrug resistance complex”. In PXE, the elastic fibers of the dermis become enlarged, tangled, and calcified, Clinically, the skin of the flexural areas of the body maintains a “plucked chicken” appearance that serves as a clue to the diagnosis. Also, hypertension and bleeding disorders in the eye occur.
Know the vascular supply of the skin.
The epidermis contains no blood supply, and it derives its nourishment via diffusion of materials through the ground substance of the dermis. It is important to understand the vascular structure of the dermis. The easiest way to conceptualize the blood vessels of the dermis is to divide it into superficial and deep vascular plexi.The cutaneous vascular system is important for wound healing, homeostasis, and modulation of inflammation/leukocyte trafficking.
Identify the major adnexal structures of the skin.
Adnexal structures include hair follicles, eccrine glands, apocrine glands, apoeccrine glands and sebaceous glands, all of which are found within the normal dermis.Sebaceous glands are oil-secreting glands located predominantly in the “oily” areas of the body including the scalp, face, neck, upper chest, and upper back.Eccrine glands are what are often referred to as “general sweat glands”. The primary function of the eccrine unit is thermoregulation, which is accomplished through the cooling effects of evaporation of this sweat on the skin surface.Apocrine glands are outgrowths of the upper bulge of the primitive ectodermal germ, a fetal structure which yields the follicular unit. The apocrine glands are located only in the axillary and anogenital area. Specialized variants of apocrine glands include Moll’s glands on the eyelids, the cerumen (ear wax) glands of the external auditory canal, and the lactation glands of the breasts.Apoeccrine glands are hybrid sweat glands that are found chiefly in the axilla. Apoeccrine glands may play a role in axillary hyperhidrosis.
Identify disease processes that occur with dysfunction or deficiency of proteins and structural components of the dermis.
Another example?One disorder of apocrine glands is chromohidrosis (which literally translates into “colored sweat”). Lipofuscin pigment is responsible for the colored sweat. This pigment is produced in the apocrine gland, and its various oxidative states account for the characteristic yellow, green, blue, or black secretions observed in apocrine chromhidrosis. Approximately 10% of people without true chromohidrosis have colored sweat which is regarded as minor, acceptable, and within the normal range. Apocrine chromhidrosis has no fully satisfactory cure or treatment.Whoa.
What is an example of a vascular disease of the skin?
A common disease involving the post-capillary venules is leukocytoclastic vasculitis. In this condition, some type of insult leads to the formation of immune complexes that get stuck to the vasculature.
What is the innervation of the skin?
Nervous tissue of the dermis function in a similar function as does nervous tissue in other areas of the body, specifically to inform and protect.Pacinian corpuscles are structures which resemble an onion in cross-section. They are involved in pressure and vibratory sensation. It is not surprising, therefore, that they are most concentrated in the genital area.Meissner’s corpuscles resemble a pine-cone and are thought to be involved in fine touch and tactile discrimination. Such receptors are in highest concentration on the distal aspects of the digits, particularly the pulps of the fingers.
What are some diseases of innervation of the skin?
Rarely a person is born with a congenital insensitivity to pain, most often with co-existing anhidrosis (an inability to sweat). The condition is caused by mutations in the neurotrophic tyrosine receptor kinase 1 (NTRK1) gene which encodes for the nerve growth factor receptor (NGFR). These children suffer from an enormous number of injuries to the skin and integument, including corneal erosions in >70%. They cannot feel the common danger signs which normally lead to protective responses. Such children have to be examined several times a day for cuts, scrapes, sand stuck in the eye, materials in the skin and other perils common to small children
Compare and contrast the clinical presentations of acne and rosacea.
Acne: inflammatory lesions: papules, pustules, nodulesRosacea: adult acne, common in people with Celtic or Northern European heritage, erythematous disorder of the central face, no trunk involvementDiffuse redness on central face• Inflammatory papules • Pustules • Telangiectasias • Flushing • In 25% cases, eyelids and conjunctivae are involved • Rhynophyma, especially in men, thickness of the skin on the nose
Compare and contrast the clinical presentations of irritant and allergic contact dermatitis
Irritant Dermatitis similar to atopic or allergic contact dermatitis. Clinical history and distribution/pattern may give clues to diagnosis of irritant contact dermatitis. May “burn” more than “itch”.Allergic contact dermatitis: Type IV, delayed-type hypersensitivity reaction usually starts 24-48 hours after exposure to the allergen, but it can be delayed longer. Similar to above.
List common clinical associations and clinical presentation of atopic dermatitis.
Common skin disease in children. Often associated with xerosis (dry skin), and a history of atopy (asthma, allergic rhinitis)Must have: Itchy skin +Plus Three or more of the following:o History of involvement of skin creases (or face if pt < 10 yrs)o Personal history of asthma or hay fever (or FH of atopic disease if pt < 4 yrs)o History of dry skin within the last yearo Visible flexural eczema (or face if pt < 4 yrs)o Onset under 2 years of age
Recognize the clinical presentations and different patterns of psoriasis
Clinical Subtypes:Chronic Plaque Disease,Guttate,ErythrodermaPustular Psoriasis:Generalized Pustular Psoriasi:Von Zumbush (with fever)Pustulosis of the palms and solesAcrodermatitis continua of HallopeauPsoriatic Arthritis Occurs in 5-20% of psoriasis patients
