Introduction to Dermatology

Question 1

Describe the different Fitzpatrick skin types

Answer 1

Type 1 - light hair, light eyes, white, +++ freckles, always burn no tan

Type 2 - blonde/brown, light to med, skin fair, ++ freckles, sunburn easily tan minimally

Type 3 - brown, med/dark, +, sunburn initially and tan gradually

Type 4 - Medium to dark hair, dark eyes, moderate brown skin, no freckles, sunburn minimally and tans well

Type 5 - Dark hair, dark eyes, dark brown skin, no freckles, rarely sunburn, dark tan

Type 6 - Dark hair, eyes, black skin, 0 freckles, never sunburn and always tan

Question 2

List the layers of the epidermis

Answer 2

Stratum corneum
Stratum granulosum
Statum spinosum
Statum basale

stratum lucidum in thick skin (between granulosum and corneum)

Question 3

Stratum basale

Answer 3

contains keratinocyte stem cells resting on a basement membrane (single layer of cuboidal cells, attached via desmosomes)

Attached to basal lamina via hemidesmosomes.

contains Merkel cells, which are sensory neuroendocrine cells that communicate w/ large, myelinated sensory afferents -> responsible for fine touch

Tonofilaments: protein structures that insert into the dense plaques of desmosomes on the cutoplasmic side of the plasma membrane

Question 4

Stratum spinosum

Answer 4

has prickly or spiny appearance due to desmosome attachments -> synthesis of involucrin and membrane coating granules begin here

where keratinization begins

Question 5

stratum granulosum

Answer 5

cross-linking keratin continues, organelles begin to disappear, and keratinocytes produce lamellar bodies (lipid containing secretions that form a hydrophobic membrane)

Keratohyalin granules contain profillaggrin -> fillaggrin cross-links keratin tonofilaments and is important in barrier function in the skin (mutated in dry skin)

Question 6

stratum corneum

Answer 6

nuclei are completely absent and keratin has formed a watertight barrier, breakdown of fillagrin forms natural moisturizing factor NFH

desmosomes still connect tightly packed adjacent cells

Question 7

Melanocytes

Answer 7

epidermal cells that produce melanin and package them within melanosomes, which can be phagocytosed by surrounding keratinocytes.

By internal conversion, melanin converts mutagenic UV radiation into harmless heat

Located primarily in the basal layer of the epidermis and in hair follicles

Question 8

Why do some people have darker skin?

Answer 8

have more melanosomes (melanin production) rather than melanocytes

Question 9

Langerhans cells

Answer 9

dendritic antigen presenting cells that populate the dermis and epidermis -> migrate to lymph nodes where they interact with T and B cells

Question 10

Melanin

Answer 10

Derived from tyrosine, synthesized by melanocytes!

Eumelanin - black to brown pigment
Pheomelanin - yellow to red-brown pigment

Light skin - melanosomes distributed in clusters above the nucleus

Dark skin - melanosomes distributed individually throughout the cytoplasm

Question 11

Dermis

Answer 11

underlying connective tissue layer, which includes:

papillary layer (loose connective tissues) lies immediately under the epidermis

deeper reticular layer (dense connective tissue)

Question 12

Vitamin D Synthesis

Answer 12

1. 7-dehydrocholesterol can be converted to cholecalciferol (Vitamin D3) in the skin byUVB
2. Cholecalciferol (Vitamin D3) and Ergocalciferol (Vitamin D2) can both be ingested and absorbed through the intestines
3. Vitamin D2 and Vitamin D3 are then converted to calcidiol (25-hydroxy Vitamin D) by the liver
4. 1,25-dihydroxy-Vitamin D (calcitriol) is the active form and is synthesized by the
   kidneys

Question 13

Vitiligo

Answer 13

Absence of melanocytes due to autoimmunity, which shows up clinically as depigmented macules and patches

Question 14

Papillary layer of the dermis

Answer 14

site of attachment to epidermis and necessary for development and differentiation

contains capillary network that is epidermal blood supply

Meissner’s corpuscles + defense cells

Question 15

Reticular layer of the dermis

Answer 15

contains extensive collagen and elastic fibers that provide strength and flexibility -> had hair and glands

pathway for major blood vessels, arranged for thermoregulation

site of nerve tracks and major sensory receptors

Pacinian corpuscles -> vibration, pressure and touch

Question 16

Meissner’s corpuscles

Answer 16

delicate tough
dermal papillae of thick skin
Schwann cells + sensory nerve terminals wrapped by fibroblasts and collagen

Question 17

Pacinian corpuscles

Answer 17

rapidly adapting receptors that detect changes in vibrations

dermis of thick and thin skin

onion like! w/ layers of flattened connective tissue-like cells -> w/ 1 sensory nerve fiber

Question 18

Apocrine Sweat Glands

Answer 18

secretion: decapitation, a process where the apical portion of the secretory cell cytoplasm pinches off and enters the lumen

located in axillary, pubic and perianal regions

milky, viscid, carbohydrate-rich secretion that is initially odorless, bacterial action makes it grody

begin to function in puberty -> have ducts that empty into hair follicles just above sebaceous glands

Question 19

Eccrine sweat glands

Answer 19

Traditional sweat glands distributed over most of the body

Not found in the lips, under nails or on the glans penis, glans clitoris just fucking understand this

Watery, enzyme-rich secretion INITIALLY ISOTONIC but then becomes HYPOTONIC as Na+ is absorbed from ducts

THERMOREGULATION!

Sweating is triggered by ACTh secretion and by the sympathetic portion of the autonomic nervous system

Question 20

Hair!

Answer 20

Develop in utero down epidermis growth forming a pilosebaceous unit

Hair -> central medulla of keratin, cortex and cuticle of hard keratin. Hair growth is intermittent. Pigment from melanocytes at the base of the hair

With contraction of arrector pili muscle stand up on end!

Question 21

Sebaceous glands

Answer 21

Holocrine secretion (entire sebocytes are being secreted)

Oil glands that secrete sebum, a complex micture of lipids.

Develop along w/ hair follicles and empty their secretion into the upper one-third of hair follicles

Development accelerated at puberty

Question 22

Epidermal rete

Answer 22

downward projections of the epidermis. Interlocking pattern of epidermal rete and dermal papillae -> fingerprints!

Question 23

Dermal papillae

Answer 23

upward projections of the dermis, interacts w/ epidermal rete

Question 24

Collagen I

Answer 24

This form comprises 85% of adult dermis. Major component of bone.

Question 25

Collagen III

Answer 25

Comprises large part of the fetal dermis, which doesn’t scar!

Question 26

Collagen IV

Answer 26

Found in high concentration in the “basement membrane zone” which is present at the dermoepidermal junction. More prominent around vessels

Question 27

Synthesis of collagen

Answer 27

Procollagen is synthesized intracellularly within fibroblasts. Consists of three seperate chains of proteins arranged in an alpha helical structure. Repeated strings of glycide and two other protein (proline and hydroxyproline)

Collagen proteins are secreted and then are assembled into collagen fibrils extracellularly. Vitamic C (ascorbic acid) is required for full assembly

Question 28

Scurvy

Answer 28

What happens to collagen without Vitamin C (abnormal collagen production)

teeth fall out, hair will grow abnormally, minor wounds will fail to heal

Question 29

Ehlers-Danlos Syndrome

Answer 29

Congenital abnormalities in collagen -> disorder of collagen synthesis

Skin hyperextensibility
joint hypermobility
tissue fragility
por wound healing

Question 30

Solar elastosis

Answer 30

sun damaged elastin. Can be stained w/ blue staining material (basophilic)

Question 31

Pseudoxanthoma elasticum

Answer 31

caused by a mutation in a gene encoding part of the multidrug resistance complex

Elastic fibers of the dermis become enlarged, tangled, and calcified resulting in a characteristic purple-blue color upon routine histological examination -> plucked chicken appearance.

Elastic fibers in the blood vessels are also damaged, leads to hypertension and bleeding disorders, particularly in the eyes

Question 32

Ground substance

Answer 32

gelatenous material -> consists of glycosaminoglcycans : lyaluronic acid and dermatan suphate. W/ the help of fibronectins, this gel functions like a sponge

constantly being destroyed and renewed via production from firboblasts

Question 33

Restylane - cosmetic filler

Answer 33

pure hyaluronic acid produced via recombinant technology -> placed under skin because it absorbs a lot of water so gets rid of wrinkles!

Question 34

Vascular structure of the dermis

Answer 34

Wound healing - endothelium, a single cell lining on the innermost surface of vessels, elaborates cytokines + endothelial growth factor

Homeostasis - Sucquet-Hoyer canal, smooth musclederived valve structure, blood can be directed towards and away from the skin.

Intracellular adhesion molecules (ICAM’s) -> white cells adhere and roll, diapedesis, so they may exit vasculature and enter soft tissue

Capillary structure of the skin is contained in uppermost portion of the papillary dermis (suprapapillary plate) -> removal of scaps causes trauma, Auspitz sign.

Question 35

Leukostatic vasculitis

Answer 35

a disease involving the post-capillay venules - immune complex formation (strep/allergies/hep c) -> type III immune rxn.

Leads to inflammation -> leukocytoplasia (process of fibrinoid deposition in the vessel walls, w/ infiltrating neutrophils and neutrophil debris)

-> manifests as palpable purpura, non-blanchable

Question 36

Free nerve endings of the skin

Answer 36

pass through upper dermis to terminate at the dermoepidermal jct, involved in both pain and itch (pruitus( -> the afferent nerves of itch are small, unmyelinated C-fibers w/ slow conduction rate

Question 37

Terminal hairs

Answer 37

large, thick, coarse and pigmented hairs.

Question 38

Vellus hairs

Answer 38

small, fine and apigmented. Located diffusely around the body.

Question 39

Hair terms

Answer 39

Hair is spread into 3rds:
infundibulum/isthmuss/matrical area

Follicular unit derived from primitive ectodermal germ

Question 40

Androgenic alopecia

Answer 40

hairs become miniturized, finer and lie higher in the dermis -> resemble vellus hairs.

Conversion of testosterone to 5-DHT is important in promoting this change. So 5alphareductase inhibitor helps.

Question 41

Chromohidrosis

Answer 41

exclusively apocrine -> lipofuscin pigment is responsible for the colored sweat -> various oxidative states could determine color!

Question 42

Apoeccrine Glands

Answer 42

hybrid sweat glands found in the axilla (axillary hyperhidrosis?)

respond mainly to cholinergic stimuli -> secrete up to 10 times as much sweat as eccrine glands

Injection of botulinim will block sweating because it blocks ACTh!!!