Dermatology - Intro To Dermatology Flashcards
Skin is composed of three layers
Epidermis
Dermis
Subcutaneous fat (panniculus)
Composed of viable keratinocytes covered by a layer of keratin
Epidermis
Principal component of dermis
Fibrillar structural protein, collagen
Composed of lobules of lipocytes separated by collagenous septa that contain neurovascular bundles
Panniculus or subcutaneous tissue
Epidermis is thickest on the
Palms and soles
Epidermis thinest on
Eyelid
Dermis thickest on
The back
Subcutaneous fat is generous in these areas
Abdomen and buttocks
Subcutaneous fat thinnest on the
Nose and sternum
First few weeks of life, fetus covered by a layer of
Nonkeratinizing cuboidal cells (periderm)
Adnexal stuctures originate as downgrowths of
Developing epidermis
Adnexal structures first develop during this time
Third month of life
Apocrine sweat units develop from this portion of follicular epithelium
Upper portion of the follicular epithelium
Sebaceous glands develop from this portion of follicular epithelium
Midregion
Adnexal structures appear first in
A. Cephalic
B. Caudal portion of the fetus
Cephalic to caudal
Three basic cell types of adult epidermis
Keratinocytes
Melanocytes
Langerhans cells
Additional cell that can be found in the basal layer of palms and soles, oral and genital mucosa, nail bed and follicular infundibula
Merkel cells
Location of merkel cells (layer)
Basal layer
Directly above the basement membrane zone
Contain intracytoplasmic dense core neurosecretory-like granules
Associated with neurites, act as slow-adapting touch receptors
Merkel cells
Have direct connections with adjacent keratinocytes by desmosomes
Contain a paranuclear whorl of intermidiate keratin filaments
Merkel cells
Exhibits a paranuclear dot pattern
Merkel cells
Label for neuroendocrine markers such as chromogranin and synaptophysin
Merkel cells
Squamous cells
Keratinocytes
Principal cells of the epidermis
Keratinocytes/ squamous cells
Keratinocytes/ squamous cells
Germ cell origin
Ectoderm
Have a specialized function of producing keratin
Keratinocytes
Complex filamentous protein that forms as surface coat (stratum corneum), structural protein of hair and nails
Keratin
Critical for normal functioning of the epidermis, its mutation are recognized causes of skin disease
Keratin
Mutation of genes for these keratin are associated with epidemolysis bullosa simplex
Keratins 5 and 14 (EBS)
Mutation of genes for these keratin are associated with epidermolytic hyperkeratosis
1, 10 (EH)
Epidermis sublayers
Stratum germinativum Stratum spinosum Stratum granulosum Stratum lucidum ( palms and soles) Stratum corneum
Innermost basal layer of epidermis
Stratum germinativum
Malpighian or prickle layer
Stratum spinosum
Granular layer
Stratum granulosum
Horny layer
Stratum corneum
Pale clear to pink layer
Palms and soles
Stratum lucidum
When the skin is scratched or rubbed, these layer thickens or forms
Stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum (thick and compact)
Regulate epidermal differentiation
Histones
Suppresses expression of profilaggrin
Histone deacetylation
Provide a reservoir for regeneration of epidermis
Slow-cycling stem cells
Abnormal keratinization can manifest as
Parakeratosis
Corps ronds
Grains
Appear in the interface between granular and cornified cell layers
Lamellar granules (odland bodies or membrane-coating granules)
Demonstrate abnormal lamellar granules
Lamellar ichthyosis and Flegel’s hyperkeratosis
Contribute a water-barrier function to skin
Found in topical products mean to restore epidermal barrier
Glycolipids (ceramides)
Lamellar bodies for, abnormally in the absence of
Critical ceramides (glucosylceramide) or disproportion of critical lipids
Desmosomal adhesions depends on
Cadherins, calcium - dependent desmogleins, desmocollins
Antibodies to caderins, calcium-dependent desmogleins, desmocollins result in
Immunobullous diseases
Desmogleins function
Adhesion
Differentiation
Profilaggrin is contained in keratohyaline granules in this layer
Granular zone
Converstion of profilaggrin to filaggrin takes place in
Granular layer
Characterized by diminished or absent granular layer contributing to retention hyperkeratosis
Ichthyosis vulgaris
Results in the formation of soft, flexible keratin
Keratohyalin
Has an active role in the immune fx of the skin
Keratinocytes
In the presence of Allergic contact dermatitis
Keratinocytes secrete
Cytokines, inflammatory mediators (TNF-alpha)
Express on their surface: intercellular adhesion molecule 1 (ICAM-1), major histocompatibility complex (MHC)
Melanocytes are derived from
Neural cresy
Melanocytes can be found in the fetal epidermis by ___ wk of development
8th
Differences in skin color is due to
Number, size, distribution of melanosomes or pigment granules within keratinocytes
Dendritic cell, lacking cell-cell junctions, lacking tonofilaments, cell with ample amphiphilic cytoplasm
Melanocye
Synthesize in the golgi zone of the melanocyte
Melanosomes
Rounder melanocytes, more pheomelanin
Red hair
Loss off fx mutation in MC1R bring about this change
Eumelanin to pheomelanin
Key components of the innate immune system of the skin
Antimicrobial peptides (cathelicidin, B defensins)
Protect against infection
Role in control of pigmentation
Implicated in the pathogenesis of atopic dermatitis
Cathelicidin, Beta defensins
small cationic proteins important to innate and adaptive immue system,
B-defensin 3
Also functions as a melanocortin receptor ligand
B-defensin 3
Eumelanin production is optimal at this pH
6.8
Evidence of keratinocyte photodamage
Thymidine dimer formation
Affected skin becomes white because of destruction of melanocytes
Vitiligo
Melanocytes number normal
Unable to synthesize fully pigmented melanosomes because of defects in enzymatic formation of melanin
Albinism
Demonstrate basilar hyperpigmentation and prominent melanin within stratum corneum
Black sunburn or ink spot lentigines
Benign proliferations of melanocytes
Nevi
Malignant counterpart of nevi
Melanomas
Effect on pigmentation of
Toll-like receptors
Bacterial lipopolysaccharides
Inc. Pigmentation
Normally found scattered in the stratum spinosum
Langerhans cells
Langerhans cells found in this layer
Stratum spinosum
Cells not connected to adjacent keratinocytes by the desmosomes
Melanocytes
Langerhans cells
Highest density of langerhans cells in the oral mucosa
Oral mucosa (vestibular region)
Lowest density of langerhans cells in the oral mucosa
Sublingual region
Stain specific for langerhans cells
Gold chloride
Characterized by a folded nucleus and intracytoplasmic organelles called birbeck granules
Langerhans cells
Langerhans cells contain these organelles
Birbeck granules
Fully developed form: organelles are rod shaped with a vacuole with one end, resembling a tennis racquet
Langerhans cells
Origin of langerhans cells
Monocyte-macrophage lineage, originate in the bone marrow
Provides recognition, uptake, processing, and presentation of antigens to T lymphocytes
Induction of delayed-type sensitivity
Langerhans cells
Plays a critical role in the langerhans cell maturation and migration
Hyluronan (hyaluronic acid)
Depletes langerhans cells
UV radiation
If skin loses langerhans cells, it loses this ability
To be sensitized (immune tolerance)
Because macrophage found in epidermis 72 h after UV B irradiation produce IL 10 (downregulates immune response)
Junction of epidermis and dermis is formed by
Basement membrane zone (dermoepidermal junction)
Basement membrane zone composed of 4:
Plasma membranes of basal cells with hemidesmosomes
Lamina lucida
Lamina densa (basal lamina)
Fibrous components assoc. with basal lamina - anchoring fibrils, dermal microfibrils, collagen fibers
basal lamina is synthesized by
Basal cells of the epidermis
Major component of basal lamina
Type IV collagen
Major component of anchoring fibrils
Type VII collagen
Two makor hemidesposomal proteins of dermoepidermal junction
BP230 (bullous pemphigoid antigen 1)
BP180 (bullous pemphigoid antigen 2, type XVII collagen)
Considered to be a porous semipermeable filter, which permits exchange of cells and fluid between the dermis and epidermis
BMZ
Serves as a structural support for the epidermis and holds the epidermis and dermis together
BMZ
Helps regulate growth, adhesion and movement of keratinocytes and fibroblasts, as well as apoptosis
BMZ
How does BMZ regulate fx
Activation of integrins and syndecans
Loss of fx of extracellular matrix protein 1 results to (in lipoid proteinosis)
Reduplication of basement membrane
Epidermal Appendages
Eccrine, apocrine glands
Ducts
Pilosebaceous units constitute adnexa
Signaling critical for hair development
Hedgehog signaling
Abnormalities in this pathway contribute to formation of
Pilar tumors
Basal cell carcinoma
Absence of hedgehog signaling results to
Embryonic hair germs may develop instead into modified sweat glands or mammary epithelium
T/F
All adnexa can function as reserve epidermisT
T
Which reepithelialize more rapidly due to abundance of adnexa
A. Face, scalp
Vs
B. Back
A. Face and scalp
Intraepidermal spiral duct, which opens directly onto the skin surface
Eccrine sweat units
Acrosyringium
Eccrine sweat units
Composed of small polygonal cells with a central round nucleus, surrounded by ample pink cytoplasm
Acrosyringium
Straight dermal portion of the duct is composed of
Double layer of cuboidal epithelial cells
Lining of dermal portion of acrosyringium
lined by eosinophilic cuticle on its luminal side
Coiled secretory portion of acrosyringium is found in this layer
Superficial panniculus
Except in the back (deep dermis)
acrosyringium
Two types of secretory cells
Large, pale, glycogen rich cells
Smaller, darker-staining cells
acrosyringium
Which type of secretory cell is thought to initiate sweat formation
Pale, glycogen-rich cells
acrosyringium
Type of secretory cell that active reabsorbs sodium, modifying the sweat from isotonic to hypotonic
Darker cells
In humans, _______ units are found in virtually all skin sites
eccrine sweat units
In most mammals, this gland is the major sweat gland
Apocrine
What mediates physiologic secretion of swear
Cholinergic innervation
Stimulus increased sweating
Heat
Emotional stress
This type of sweating involves a biphasic response, with initial hyperpolarization and secondary depolarization mediated by activation of Ca and Cl ion conductance
Cholinergic sweatinf
Sweating
Involves monophasic depolarization
Dependon on GCI (cystic fibrosis transmembrane conductance regulator)
Adrenergic secretion
This type of sweating is absent in pt with CF
No adrenergic secretion
This hormone also play a role in stimulating eccrine secretion
Vasoactive intestinal polypeptide
Apocrine units develop as outgrowths of
Infundibular or upper portion of hair follicle (not surface epidermis)
T/F
Although immature apocrine units are found covering the entire skin surface of the human fetus, these regress and are absent by the time the fetus reaches term.
T
Straight excretory potion of apocrine duct composed of
Double layer of cuboidal epithelial cells
Apocrine sweat glands open into
Infundibular portion of hair follicle
Coiled secretory gland of aprocrine glands is located at the
Junction of dermis and subcutaneous fat
Lining of the coiled secretory gland of apocrine
Single layer of cells (columnar to cuboidal)
More widely dilated than eccrine coils
Apocrine coils
Sweat stains more deeply red in H&E sections
Apocrine coilds
Pale pink sweat stains H&E
Eccrine
Decapitation secretion (apex)
Apocrine sweat glands
Apocrine secretion is mediated by
Adrenergic innervation
Catecholamines (circulating, adrenomedullary origin)
VIP
Episodic excretion, continuous secretion
Apocrine
Function of apocrine sweat glands in humans
No known fx
Apocrine fx other anmials
Protective, sexual, thermoregulation
Apocrine generally found in the ff sites
Axillae, Areolae Anogenital region External auditory canal (ceruminous glands) Eyelids (glands of Moll) Stroma of sebaceous nevus of Jasasshon
Apocrine glands do not begin to fx until
Puberty
Upper bud of fetal follicle develops into
Sebaceous glands
Lower bud of fetal follicle develops into
Becomes attachment of the arrector pili muscle
A third epithelial bud develops from the opposite side of the follicle above the lvel of the sebaceous gland anlage and gives rise to ____
apocrine gland
Uppermost portion of the follicle, which extends from its surface opening to the entrance of the sebaceous duct is called
Infundibular segment
Portion of the follicle betwen sebaceous duct and insertion of arrector pili muscle is
Isthmus
Throughout life, in the follicle, this portion undergoes cycles of involution and regeneration
Inferior portion
Hair follicles develop sequentially in rows of
Three
Are surrounded by the appearance of two secondary follicles
Primary follicles
Where to the arrector pili muscles interconnect within the follicular unit
Isthmus
Move together as hair grows
Hair shaft and inner root sheath until the fully keratinized inner rooth sheath sheds at the level of isthmus
Portion of the follicle that is permanent
Upper two (infundibulum, isthmus)
This segment is completely replaced with each new cycle of hair growth
Inferior segment
Active growth phase of hair
Anagen
Anagen lasts
3-5 years
% of scalp hairs in anagen phase
85-90%
Scalp anagen hairs grow at a rate of
0.33 mm/day
Catagen / involution lasts
2 weeks
Resting phase of hair
Telogen
Telogen lasts
3-5 months
AIDS effect on anagen phase
Prolonged
Synchronous termination of anagen or telogen results in
Telogen effluvium
is when some stress causes hair roots to be pushed prematurely into the resting state
Telogen effluvium
Telogen effluvium can be induced by
Febrile illness, surgery, weight loss
___ months after pregnancy, a more pronounced effluviun is noted
3-5 months
This hair cycle is characterized by a pigmented bulb and inner root sheath
Growing anagen hair
chemotherapy affects this cycle
Anagen
Best identified by presence of apoptotic cells in the outer root sheath
Catagen hairs
Have nonpigmented bulb with a shagging lower border
Telogen club hairs
Scalp hair of white people is shaped
Pubic hair, beard and eyelashes are shaped
Round
Oval
Scalp hair of black people are
Oval
Which causes it to be curly
Uncombable hair is
Triangular with a central canal
Hair shape is partially controlled by
Trichohyalin gene
Hair color depends on
Degree of melanization
Distribution of melanosomes within the hair shaft
Larger melanosomes are found in the hair of
Black persons
Smaller melanosomes which are aggregated within membrane bound complexes are found in the hair of
White persons
Graying of hair results from
Decreased number of melanocytes (fewer melanosomes)
Premature graying is related to
Exhaustion of the melanocyte stem cell pool
Sebaceous glands are formed as an outgrowth ofrom
Upper portion of hair follicle
Composed of lobules of pale-staining cells with abundant lipid droplets in their cytoplasm
Adnexa
Sebaceous glands
Lined by a red cuticle that undulates sharply ina pattern resembling shark’s teeth
Sebaceous duct
Sebaceous glands are found in greatest abundance on the
Face, scalp
Sebaceous glands are not found in
Palms and soles
Hair follicles of the tarsal plate of the eyelids (meibomian glands), buccal mucosa, vermilion border of the lip (fordyce spots), prepuce, mucosa lateral to the penile frenulum (Tyson glands), labia minora, female areola (Montgomery tubercles)
Adnexa functionally and anatomically related to
Hair follicle
Unique secretory products of sebaceous glands
Wax esters
Squalene
Can reduce squalene levels produced by sebaceous glands
Antihistamines
Fx of skin lipids
Barrier fx Antimicrobial properties (sphingoid bases from epidermal ceramides and fatty acids from sebaceous triglycerides)
Protect the fingertip from trauma
Nails
Leads to the formation of nail plate
Matrix keratinization
Fingernails grow an average
0.1 mm/day
How many months does it take to replace a complete nail plate
4-6 months
Growth rate is much slower for this nail
Toe naikl (12-18 months)
Keratin types found in the hair
Epidermal and hair types, with hair types predominating
This keratin is only present in nail isthmus
Keratin 10
Demonstrate widening of intercellular space between nail keratinocytes on electron microscopy
Brittle nails
Rete pegs that resemble an egg crate
Skin
True parallel rete ridges
Nail bed
Nail cuticle is formed by keratinocytes of
Proximal nailfold
Nail plate is formed by
Matrix keratinocytes
Distal portion of the nail matrix
Lunula
Endogenous pigments tend to follow the contour of
Lunula
Exogenous pigments follow the
Contour of the cuticle
Dorsal nail plate is formed by
Proximal matrix
Ventral nail plate is formed by
Distal matrix, with contribution from nail bed
Melanocytes derive from
Neural crest
Nerves derive from
Neural crest
Dermis derived from
Mesodermal
Dermis as dendritic-shaped cells containing mucopolysaccharide (precursors of fibroblasts)
Week of fetal life
6th week
Week of fetal life
Fibroblasts are actively synthesizing reticulum fibers, elastic fibers, collagen
12th week
Vascular network develops
Fat cells appeared beneath the dermis
Week of fetal life
24th week
This signaling is critical for the differentiation of ventral versus dorsal dermis
Wnt/ Beta catenin signaling
Serves as a scaffold for the adnexal structures
Dermis
Dermis composed of small collagen bundles that stain deeply red
Infant dermis
Dermis with few fibroblasts persist, coollagen bundles are thick, stain pale red
Adult dermis
Two populations of dermal dendritic cells are noted
Factor XIIIa - positicve dermal dendrocytes
CD34+ dermal dendrocytes
Dermal dendritic cell
Gives rise to dermatofibromas, angiofibromas, acquired digital fibrokeratomas, pleomorphic fibromas, fibrous papules
Factor XIIIa - positive dermal dendrocytes
This dendrocyte are accentuated around hair follicles but exist throughout the dermis
CD34+ dermal dendrocytes
Dendrocyte that disappear from the dermis early in the course of morphea
CD34+ dermal dendrocytes
Rare skin condition that causes painless, discolored patches on your skin
Skin changes appear on the abdomen, chest, or back
It tends to affect only the outermost layers of the skin
Morphea
Tx for morphea that allows CD34+ dermal dendrocytes to reappear
UVA1 light treatment
Principal component of dermis is the collagen
Collagen
Represents 70% of the dry weight of the skin
Collagen
Amino acids in collagen
Hydroxyproline
Hydroxylysine
Glycine
Collagen type
Dermis
Type I collagen
dermis below the lvel of post-capillary venule
Reticular dermis
Collagen expressed in the reticular and papillary dermis
Collagen I mRNA and collagen III mRNA
What downregulates collagen production in dermis
UV light (photoaging)
Type collagen
BMZ
Type IV
Type collagen anchoring fibrils
Type VII
Type IV and Type VII produced predominately by
Keratinocytes
Collagen
Dystrophic epidermolysis bullosa
Acquired epidermolysis bullosa
Type VII
Produces elastic fibers, ground substance of dermis (glycosaminoglycans, acid mucopolysaccharides)
Fibroblast
Consist of two components: protein filaments + elastin
Elastic fibers
AA unique to elastic fibers
Desmosine and isodesmosine
Fine elastic fibers
Papillary dermis
Coarse elastic fibers
Reticular dermis
Minor component of normal dermis but is a major mucopolysaccharide that accumulates in pathologic state
Hyaluronan
Major stress-resistant material of the skin
Collagen
Contribute little to resisting deformation and tearing of the skin but have a role in maintaing elasticity
Elastic fibers
Term generally used to refer to a clinically heterogenous group of autoimmune diseases including lupus erythematosus, scleroderma, dermatomyositis
Connective tissue disease
Involves the most visible collagen abnormalities, collagen bundles become hyalinized and space between collagen bundles diminish
Scleroderma
produce increased dermal mucin, mostly hyaluronic acid.
Lupus
Dermatomyositis
Has autoantibodies directed against type VII collagen
Bullous lupus
Diseases that have defects in collagen synthsis
Ehlers-Danlos syndrome
X-linked Cutis laxa
Osteogenesis imperfecta
Defect in elastic tissue
Marfan syndrome
Pseudoxanthoma elasticum
Dermal vasculature consists of
Two intercommunicating plexuses
- Subpapillary plexus
- Deeper, lower horizontal plexus
Upper horizontal network
Subpapillary plexus
Contains postcapillary venules and courses at the junction of papillary and reticular dermis
Subpapillary plexus
This plexus furnishes a rich supply of capillaries, end arterioles, and venules to the dermal papillae
Subpapillary plexus
Vasculature found at the dermal-subq interface composed of larger blood vessels
Deeper, lower horizontal plexus
Nodular lymphoid infiltrates surroundting this lower plexus are typical of
Inflammatory morphea
Vasculature of dermis is well developed at sites of
Adnexal structures
Smooth muscle in the skin occurs as
Arrectores pilorum
Tunica dartos of scrotum
Areolas of the nipples
Produce goosflesh
Below the sebaceous glands
Arrectores pilorum
Scattered smoothmuscle throughout the dermis is typical of
Anogenital skin
Composed of small bundles of smooth muscles that crisscross at right angles
Muscularis of veins
Smooth muscle forms a concentric, weathlike ring
Arterial
Specialized aggregates of smooth muscle cells found between arterioles and venules prominent in the digits and lateral margins of palms and soles
Glomus bodies
Serve to shunt blood and regulate temperature in the digits, lateral margins of palms and soles
Glomus bodies
Vascular smooth muscle expresses
Vimentin
Most smooth muscle expresses
Desmin inetrmediate filaments
This is consistently expressed by all types of smooth muscle
Actin
Striated msucle occurs in the skin of the neck as
Platysma muscle
Face - -muscles of expression
Complex network of striated muscle, fascia, aponeuroses
Superficial muscular aponeurotic system (SMAS)
Presence of long, sausage like granulomas following path of nerves in the deep dermis
Hansen’s disease
Touch and pressure mediated by
Found in the dermal papillae esp digits, palms and soles
Meissner corpuscles
Touch and pressure mediated by
On the deeper portion of the dermis of weight-bearing surfaces and genitalia
Vater-Pacini corpuscles
Temperature, pain and itch are transmitted by these fibers
Unmyelinated nerve fibers
Temperature, pain and itch pass to the CNS by way of
Dorsal root ganglia
Histamine-evoked itch is transmitted by
Slow-conducting unmyelinated C-polymodal neurons
Regulate vasoconstriction, apocrine gland secretions, contraction of arrector pili is regulated by
Postganglionic adrenergic fibers
Mediate eccrine sweat secretion
Cholinergic fibers
Play a role in normal immune response in the skin, immediate-type sensitivity, contact allergy, fibrosis
Mast cells
Resemble fried eggs in histologic sections
Mast cells
Mast cells become spindle-shaped hyperchromatic, resmble large dark fibroblasts
TMeP
Telangiectasia macularis eruptiva perstans
Mast cells has receptor site for this Ig
IgE
Mast cells accumulate in the skin because of abnormal proliferation, migration, and failure of apoptosis
Mastocytosis
Lobules of fat cells separated by fibrous septa composed of collagen and large BV beneath the dermis
Subq
Polypeptide that reduces feed intake and weight gain in rodents
Obestatin
Causes abnormal fat distribution and
Insulin resistance
Cushing syndrome
Antiretroviral theraoy
Inflammatory dermatoses that affects primaryly the septa or fat lobules
Panniculitides
