DSF Histo of Skin

Question 1

3 layers of skin

Answer 1

Epidermis
Dermis
Hypodermis (subcutis)

Question 2

Epidermis

Answer 2

Keratinized stratified squamous epithelium

Question 3

Dermis

Answer 3

Papillary and Reticular

Loose irregular and dense irregular CT

Question 4

Hypodermis (subcutis)

Answer 4

Loose CT

Shock absorption, insulation, energy reservoir

Question 5

Thick skin

Answer 5

Soles and palms
Thick layer of epidermis 
Only eccrine glands, no other appendages
Highly innervated for exquisite sensory discrimination
*Have Stratum lucidum

Question 6

4 cell layers of epidermis (5 in thick skin)

Answer 6

Stratum basale
Stratum spinosum
Stratum granulosum
Stratum lucidum
Stratum corneum

Question 7

4 cell types w/in the epidermal cell layers

Answer 7

Keratinocytes
Melanocytes
Langerhans cells
Merkel cells

Question 8

Keratinocytes

Answer 8

Ectodermally-derived cells
Protection from mechanical forces, UV light, water barrier
Specialized apoptosis involved in maturation
Contain majority of skin’s melanin

Question 9

Melanocytes

Answer 9

Produce melanin (oxidation of Tyr (tyrosinase key), released in melanosomes)
Found in stratum basale
Origin: neural crest

Question 10

Langerhans cells

Answer 10

Stratum spinosum
Immune cells of epithelium - can migrate
Lymphocytes, mast cells, macrophages
Dendritic cells (APCs) - adaptive immunity
Derived from bone marrow stem cells (mesoderm)
NO pigment or keratin, can be identified in TEM by folded nuclei
Birbeck granules

Question 11

Merkel cells

Answer 11

Mechanoreceptor cells of epithelium (SB of epidermis)
Also found along basement membrane of hair follicles
Form Merkel corpuscle along w/ underlying nerve processes
Likely neural crest origin
Intimately associated w/ a nerve fiber

Question 12

Stratum basale

Answer 12

Single cuboidal/low columnar layer, attached to BL by hemidesmosomes
Proliferative
Beginning of keratin synthesis - few keratin filaments
Continuous w/ basal layer of appendages
Stains blue due to lots of free ribosomes
Vitamin D production
Melanin present above nucleus (to protect DNA)

Question 13

Stratum spinosum

Answer 13

Stratified and non-uniform
Vitamin D production
“Spinous” processes: cytoplasmic projections/desmosomal attachments
Near basal layer: Proliferative capability, keratin synthesis
Near surface: flatter, larger, more TFs, start of water barrier formation

Question 14

Keratohyalin granules

Answer 14

Stratum granulosum

Contain filaggrin and trichohyalin - involved in aggregation of keratin filaments into tonofibrils (TFs)

Question 15

Stratum granulosum

Answer 15

1-3 layers thick
No proliferation
Even more keratin filaments bundled into TFs
Lamellar bodies released
Keratohyalin granules
Cells undergo apoptosis

Question 16

Stratum corneum

Answer 16

Dead cells (no nuclei/organelles)
Keratin matrix
Coated w/ water barrier
Subject to exfoliation/desquamation
*SL in thick skin similar

Question 17

Psoriasis

Answer 17

Accelerated cell proliferation and maturation rate

Characteristic scaly plaques

Question 18

Desquamation of SC

Answer 18

Deep layer of SC at neutral pH, becomes acidic superficially - disrupts desmosomal junctions

Question 19

Cytocrine secretion

Answer 19

Process by which keratinocytes take up melanin: phagocytose tips of melanocyte dendritic processes
Direct transfer of secretory material from 1 cell to another

Question 20

What is skin pigmentation determined by?

Answer 20

Amount, type, and packaging of melanin in epidermis
Partially controlled by melanin breakdown rate (faster in lighter skinned individuals)
(not determined by # of melanocytes)

Question 21

Albinism

Answer 21

Hypopigmentation
Defective melanin production
Lack of melanin, due to defect in tyrosinase
Normal # of melanocytes

Question 22

Vitiligo

Answer 22

Hypopigmentation

Autoimmune destruction of melanocytes

Question 23

Dermal-Epidermal Junction

Answer 23

Epidermis separated from dermis by BL
Rete ridges: epidermis extends down
Dermal papillae: dermis extends up
Gives fingerprint (high density)

Question 24

Bulbous pemphigous

Answer 24

Autoimmune disorder w/ antibodies against the hemidesmosomes

Huge blisters occur due to disruption of dermal-epidermal junction

Question 25

Papillary Dermis

Answer 25

Superficial loose (areolar) cellular layer/CT

Question 26

Reticular Dermis

Answer 26

Lower, denser, less cellular layer/CT

Question 27

Eccrine (sweat) gland

Answer 27

Thermoregulation, can be stimulated by stress Secrete hypotonic fluid that evaporates on skin surface Found in dermis and superficial hypodermis Ectodermal in origin Simple, coiled tubular glands Glands are pseudostratified epithelium but ducts are 2 layer stratified cuboidal Merocrine secretion - exocytosis Controlled by sympathetic NS Clear, Dark, Myoepithelial cells

Question 28

Apocrine (sweat) gland

Answer 28

Secrete fatty acids, proteins, carbs, ammonia, serous fluid, pheromones *by budding off of the cytoplasm* Found in axilla, areola, genital region and anus Ducts discharge into the hair follicle Found in dermis and upper hypodermis Merocrine gland - coiled tubular, occasionally branched Simple cuboidal epithelium Highly androgen sensitive; not functional until puberty

Question 29

Underarm odor

Answer 29

Bacteria process apocrine secretions

Question 30

Sebaceous gland

Answer 30

Produce and secrete sebum: highly lipid secretion that lubricates the skin Resist friction and water barrier Holocrine gland: secretions made up of disintegrated cells and sebum (apoptosis) Sebocytes form acini which attach to a common duct Highly androgen sensitive

Question 31

Hair follicles

Answer 31

Hair follicle continuous w/ epidermis (SB) Sebum deposition moisturizes hair Hair growth occurs at the bulb, where blood supply and innervation richest Matrix cells in bulb proliferative Merkel cells Melanocytes that contribute to hair color Associated w/ arrector pili muscle

Question 32

Meissner Corpuscles

Answer 32

Encapsulated mechanoreceptors found in dermal papillae Multiple flattened Schwann cells interspersed by spiraling nerve fibers giving a whorled appearance Tactile, fine *light* touch sense

Question 33

Free nerve endings

Answer 33

Simple unmyelinated nerves found penetrating the epidermis

Question 34

Pacinian Corpuscles

Answer 34

Deep dermis and hypodermis Sense pressure and vibration Huge, look like onions in LM

Question 35

Peritrichial nerves

Answer 35

Hair base and shaft highly innervated and stimulated by movement of hair

Question 36

Ruffini end organs

Answer 36

Stretch receptor found in dermis and joint capsules Encapsulated fluid-filled structures traversed by collagen Transmit kinesthetic info (position sense, movement, etc.)

Question 37

Diabetic neuropathy

Answer 37

Peripheral nerve damage leads to loss of skin sensation - can make patient unaware of minor injuries Severe infections can occur if injury goes unnoticed

Question 38

Blood Supply to skin

Answer 38

``` Blood reaches skin via larger vessels in hypodermis (highly vascularized) Subpapillary Plexus (gives off capillary loops) and Cutaneous Plexus ```

Question 39

Arteriovenous anastomoses

Answer 39

Shunts in upper dermis Highly involved in thermoregulation and preservation (shock) In cold and when intravascular volume low (shock): blood shunted away from skin

Question 40

Protective Features of Skin

Answer 40

Mechanical: Stratified squamous epithelium, keratinization, water barrier Immunoprotection: LC, diffuse lymphatic tissue, dermal lymphatics, macrophages UV damage: melanin

Question 41

Follicular bulge

Answer 41

(Of hair follicle) | Has stem cells for melanocytes and for epidermis