Dermatology Flashcards
Skin + UVB=
Cholecalciferol (Vitamin D3)
The liver converts Vitamin D3 into
Calcidiol (25-hydroxy Vitamin D)
The Kidneys convert 25 hydroxy Vitamin D (Calcidiol) into
active 1,25 dihydroxy Vitamin D (Calcitriol)
Fitzpatrick Skin Types I and II
I. Never tans, always burns
II. Tans with difficulty, usually burns
Fitzpatrick skin types III and IV
III. Average tanning, sometimes burns
IV. Easily tans, rarely burns
Fitzpatrick skin types V and VI
V. Very easy to tan, very rarely burns
VI. Never burns
Types of cells present in the epidermis
Keratinocytes, Langerhans cells, Melanocytes
Two types f melanin produced by melanocytes
Eumalanin: black to brown pigment
Pheomelanin: yellow to red-brown pigment
Skin pigmentation is due to:
TYPE OF MELANIN PRODUCED,
AS WELL AS SIZE AND DISTRIBUTION OF MELANOSOMES
Distribution of melanosomes in Light skin vs dark skin
in light skin, the melanosomes are smaller and are distributed in clusters above the nucleus in the keratinocyte, in dark skin, the melanosomes are larger and distributed individually throughout the cytoplasm of the keratinocyte
The absence of melanocytes is called _____. Where is it commonly seen?
Vitiligo, commonly seen in periorifacial and acral locations
Layers of the epidermis
Stratum corneum
Stratum granulosum
Stratum spinosum
stratum basalis
How long does renewal of the epidermis take?
28 days
Hemidesmosome
Attachment point of basal cells to the basal lamina of the dermal epidermal junction
Bullous Pemphigoid
Autoantibodies to BP180 (type XVII collagen) or BP230, both found int he hemidesmosomes. Causes subepiderman blisters and tense bulla. Most common autoimmune bullous disorder. Treatment: prednisone
keratin,
a tough protective protein that makes up the majority of the structure of skin, hair and nails. MAde by keratinocytes of the epidermis
Desmosomes
structuresfor cell to cell adhesion (macula adherens)
• Contain intracellular keratin filaments and transmembrane proteins, desmogleins and desmocollins
Acquired antibodies to desmoglein 1 and desmoglein 3 cause ____ _____
pemphigus vulgaris
Pemphigus Vulgaris
-Primary skin lesions are flaccid bulla (Nickolsky sign positive)
-Pathology: Intraepidermal blisters
• painful oral erosions
• Other mucous membranes can be involved (eyes, GI and GU mucosa)
• Treatment: Prednisone or other immunosupressives
What cell layer do the cells start to lose their nuclei?
Statum granulosum
What do the granules of keratinocytes contain?
keratohyalin granules contain filaggrin, which X-links keratin, lamellar bodies excrete ceramics
What is the stratum corneum composed of? What keeps it moist?
dead and desquaming keratinocytes. Natural moisturizing factor (NMF) keeps it moist
Patients with ______ mutations have significantly reduced levels of the NMF in the stratum corneum and exhibit increased _______ water loss
filaggrin
transepidermal
Merkel cells
Small cells associated with nerve endings in epidermis. Their function has long been uncertain, but they seem to be involved in neural development and tactile sensation. Recent evidence supports a role for Merkel cells in light touch
Macule
Flat area of color change
Less than 1.0 cm
Can be hyper pigmented or hypopigmented
Patch
Flat area of color change
Greater than 1.0 cm
Can be hyper pigmented (think cafe au lait spot) or hypopigmented
Papule
Discrete,solid,elevatedbody
• Less than 1 cm in diameter
• May be further classified by surface change
– Scale, Crust
Plaque
- Solid,flat-topped,elevated area of skin
- Greater than 1cm and broader than thick
- May be further classified by surface change
Nodule
- Firm and well-defined lesion
- May be dermal or subcutaneous
- Greater than 1.0 cm
Scale
- Excess stratum corneum (outermost layer)
- May appear as flakes or plates
- Color usually white or gray
Crust
• Dried blood, serum or purulent exudate that
forms on the skin surface
• May be thick or thin
• Color determined by type of dried fluid
Vesicles
- Fluid filled cavity or elevation
- Form within or just below epidermis
- Less than 1.0 cm in diameter
Bulla
- Fluid filled “blister”
* Greater than 1.0 cm in diameter
Pustule
- Circumscribed elevation that contains pus
- Less than 1.0 cm in diameter
- Color usually whitish-yellow
Erythema
- Localized, blanchable redness
* Caused by increased blood flow
Erythroderma
- Generalized, blanchable redness
- Caused by increased blood flow
- May be associated with desquamation or extensive scaling
Telangiectasias
• Visible, persistent, dilation of small, superficial cutaneous blood vessels
Palpable purpura
• Raised and palpable discoloration
• Due to vascular inflammation and
extravasation of red blood cells (vasculitis)
• Color is red or violaceous
Erosion
- Localized loss of epidermal or mucosal epithelium
* Causes can include injury or denuding of vesicle or bulla roof (removal)
Ulcer
• Circumscribed loss of epidermis and at least upper dermis
– Depth: can extend to subcutaneous, muscle or
bone areas
– Edge: clean, ragged, undermined
– Tissue at base: necrotic, purulent or healthy granulation tissue
Eschar (crust)
•”Scab”
• Adherent,thick,dry crust
• Causes: trauma, infection, or excoriating skin disease
• Black
Intertriginous distribution
Regions where opposing skin surfaces come in contact that may cause friction
Flexural distribution
• Pertaining to the skin surface overlaying muscles that flex joints, such as biceps
Does the epidermis contain blood vessels?
The epidermis contains no blood vessels, it depends upon the dermis for all its nutritional support.
The dermis also provides the _____, _____ and _____ of the skin
strength, resiliency and plasticity
Two zones of the dermis
: a) the papillary dermis (located immediately beneath the epidermis), and b) the reticular dermis located deeper in the tissue.
Dermal matrix consists of
mixture of collagen fibers, elastic fibers and ground substance all of which are synthesized by dermal fibroblasts.
skin appendages or adnexal structures
hair follicles, sebaceous glands (oil glands), and sweat glands found in the skin that are vital to protection and homeostasis.
dermal papillae
The downward projections of epidermis interdigitate with upward projections of the dermal papillae
What is the main function of collagen in the skin?
It provides essentially all the tensile strength of the skin.
What type of collagen comprises >85% wt % of the adult dermis?
Collagen I
What type of collagen is present in large quantities in the fetal dermis?
Collagen III
Structure of collagen
three chains of proteins arranged in an α-helical structure, electron microscope yields a characteristic pattern of striations with 68 nm intervals. The chains consist of repeated strings of glycine and two other proteins, forming a Gly-X-Y structure. The X and Y are usually proline and hydroxyproline.
Where/how is collagen synthesized?
The synthesized collagen proteins are secreted and then are assembled into collagen fibrils EXTRACELLULARLY.
classic example of an acquired abnormality in collagen production
Scurvy
Ehlers-Danlos syndrome (EDS)
genetic disorders of collagen synthesis, all of the subtypes share 4 major clinical features including:
- skin hyperextensibility
- joint hypermobility
- tissue fragility
- poor wound healing
Collagen fibers provide the skin with tensile strength, but elastic fibers provide the skin with ________
resiliency
elastic fibers are ______ (silver-loving) and special silver stains (such as the ______) may be performed to accentuate the presence of elastic fibers
argyrophilic
Verhoff-Van Gieson stain
The most common acquired disorder of elastic is
solar elastosis
Over a lifetime, a person accumulates sunlight exposure, leads to degeneration of the elastic. collagen bundles become dystrophic tend to “clump”sun-damaged elastic fibers become easy to appreciate on routine microscopy, as basophilic (blue) staining material within the superficial portions of the dermis.
pseudoxanthoma elasticum (PXE)
caused by mutation in a gene encoding part of the “multidrug resistance complex”, responsible for pumping compounds out of cells. The elastic fibers of the dermis become enlarged, tangled, calcified–> characteristic purple-blue color on histo. Skin of the flexural areas= “plucked chicken.” Elastic fibers of the blood vessels are also damaged leading to hypertension and bleeding disorders, particularly in the eye.
Ground substance
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.
Is ground substance static?
No, ground substance is constantly being destroyed, by enzymes like hyaluronidase, and then renewed via production from fibroblasts
Restylane
pure hyaluronic acid, placed under skin to augment the tissue and remove lines. It is well-suited for this purpose for two reasons: a) it is a natural substance that is already present in the skin and it does not engender an immune response (unlike some bovine collagen fillers) and b) it absorbs a tremendous amount of water and amplifies the augmentation. Just like endogenously produced hyaluronic acid, Restylane is broken down by tissue hyaluronidases and it is not a permanent augmentation.
verruca
warts. They are benign, virally induced neoplasms (growth) that require an increased blood supply simply to support the virally-proliferating cells. These proliferating vessels may be identified as brownish, thrombosed capillary structures in the center of the verruca
leukocytoclastic vasculitis. How does it manifest clinically?
A common disease involving the post-capillary venules due to the precipitation of immune complexes in the walls of vessels.
. Clinically, vasculitis manifests as “palpable purport” (non blanch able). PMNs attach to vessel wall and degranulate, yielding damage and the extravasation of RBCs into the dermis. This deposition in the vessel walls, w/ infiltrating neutrophils and PMNs debris is called leukocytoclasia.
Free nerve endings pass through the upper dermis to terminate at the:
dermoepidermal junction
Nerves and conduction rate of pruitus
slow, umyelinated C fivers
Pacinian corpuscles
are structures which resemble an onion in cross-section. They are involved in pressure and vibratory sensation. 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
Terminal Hairs
large, thick, coarse, pigmented. Ex: scalp, a man’s beard area and possibly chest/back, and the pubic area, begin deep in the dermis at/near the dermal-subcutaneous junction.
Vellus Hairs
small, fine, and apigmented. Such hairs are located diffusely on the body, and represented the types of hairs often on the ear, the lateral face of women, and the body in general.
It is common to divide the hair follicle into thirds:
infundibulum=upper third
isthmus= middle third (from the sebaceous duct to the insertion of the arrector pili)
martial area= lower third.
Phases of hair life cycle
~85%-anagen (the growth phase),
10-15% telogen (the resting phase)
(1-5%) in catagen (transition phase between anagen and telogen)
androgenic alopecia
hairs become miniaturized, finer and lie higher in the dermis. Ultimately they come to resemble vellus hairs. Conversion of testosterone to 5-dihydrotestosterone is important in promoting this change
treatments of male pattern baldness
finasteride, a 5-α-reductase inhibitor
minoxidil, a drug known to promote the anagen phase
holocrine gland
(sebaceous glands are and example) the method of secretion involved entire sebocytes (sebaceous gland cells) being secreted and in the process breaking-down to extrude the contents.
Acne is a ubiquitious disorder of the _______ unit
pilosebaceous
comedones
Blocked pores that are further classified to be: open - “black heads” or closed - “white heads”.
Eccrine glands
“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.
Merocrine glands/secretion
secrete WITHOUT either the apocrine blebbing, or holocrine shedding. Eccrine glands are a classic example of a merocrine secretion.
that even though sweating is mediated by the _____ portion of the autonomic nervous system it is triggered via _______ secretion. This is a chemical otherwise associated with the ________ nervous system.
sympathetic
acetylcholine
parasympathetic
Apocrine glands
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. At puberty, hormonal stimulation causes apocrine glands to become functional, and the glands respond mainly to sympathetic adrenergic stimuli initiated by emotional stress.
The predominant mode of apocrine secretion is
decapitation, a process where the apical portion of the secretory cell cytoplasm pinches-off and enters the lumen
Apoeccrine glands
hybrid sweat glands that are found chiefly in the axilla. Apoeccrine glands may play a role in axillary hyperhidrosis. These hybrid glands have both a small diameter portion, similar to an eccrine gland, and a larger diameter portion that resembles an apocrine gland. Similar to eccrine glands, they respond mainly to cholinergic stimulihybrid sweat glands that are found chiefly in the axilla. Apoeccrine glands may play a role in axillary hyperhidrosis. These hybrid glands have both a small diameter portion, similar to an eccrine gland, and a larger diameter portion that resembles an apocrine gland. Similar to eccrine glands, they respond mainly to cholinergic stimuli
Which secretes more, an apoeccrine gland or an eccrine glands
apoeccrine glands secrete nearly ten times as much sweat as eccrine glands
hyperhidrosis
focal excessive sweating. may be eccrine, particularly “clammy hands” or “sweaty feet, or may be due to apoeccrine glands in the axilla. generally do not sweat during sleep, most authorities consider it a disease of autonomic dysfunction.