Intro: Biology of the Skin

Question 1

What are the three layers of the skin?

Answer 1

Epidermis, Dermis, Subcutis

Question 2

What cells are in the epidermis? (4)

Answer 2

Primarily keratinocytes with melanocytes, Langerhans cells, and Merkel cells

Question 3

What are the components of the dermis? (5)

Answer 3

Fibroblasts, collagen, elastin, blood vessels, nerve endings

Question 4

What are the components of the subcutis? (3)

Answer 4

Fat!, blood vessels, and fibrous septae

Question 5

What is the primary function of the Epidermis?

Answer 5

Barrier, protection, wound healing

Question 6

What is the primary function of the Dermis and Subcutis?

Answer 6

Structural support, vascular support, and innervation

Question 7

True or False. The epidermis is a self-renewing tissue that “sheds” itself every 18 days.

Answer 7

False. The epidermis IS self-renewing, but it sheds itself every 28+ days

Question 8

Where do the cells in the epidermis grow from? What happens as they move up?

Answer 8

Grow from stem cells in basal layer and terminally differentiate as they move upwards

Question 9

Is apoptosis high or low in epidermis?

Answer 9

Usually low

Question 10

What 4 layers (from top to bottom) is the epidermis divided into?

Answer 10

1) Stratum corneum 2) Stratum granulosum 3) Stratum spinosum 4) Stratum basale

Question 11

What is the layer of skin that is the source of stem cells, and divison starts in. What is this layer held to the basement membrane with? (IMPORTANT!)

Answer 11

Stratum Basale; Hemidesmosomes!

Question 12

What is the layer of skin in which cells stop dividing and commence terminal differentiation and lipids start to develop in? What holds these cells together that make it appear “spiny”? (ASLO IMPORTANT!)

Answer 12

Stratum Spinosum; desmosomes hold the keratinocytes together!

Question 13

What is the function of Hemidesmosomes in the skin? What is the fucntion of desmosomes in the skin?

Answer 13

Hemidesmosomes hold the basal layer to the basement membrane while desmosomes hold the keratinocytes together (This should be like giving a dead horse guaifenisen by now…)

Question 14

What is the layer that intracellular keratohyaline granules are synthesized (including profillagrin) and lipids are secreted into intercellular space? Why are lipids secreted?

Answer 14

Stratum granulosum; to act as a water barrier

Question 15

What is the layer of skin in which organelles and nuclei degenerate? What is profilaggrin processed into and what does that product do? What combines with this product and what does that do? (this may be important)

Answer 15

Stratum Corneum; processed into filaggrin for keeping water in cells; keratins combine with filaggrin to form MACROFIBRILS that help create a protective layer.

Question 16

What varies between the epidermis from area to area of the body? (ex. between palm and trunk?)

Answer 16

The thickness of the stratum corneum changes vastly.

Question 17

What has the stratum corneum been compared to and what does each thing represent?

Answer 17

“Brick and Mortar” where the bricks are flattened keratinocytes filled with keratin and filaggrin and the mortar is the lipid mixture surrounding keratinocytes providing a water barrier

Question 18

What is keratin the major fibrous structural protein in and what do they combine to form? What do they do for the cell? What do they contain large amounts of?

Answer 18

In hair and nails and they combine to form INTERMEDIATE filaments; they stabilize against physical stress; large amounts of sulfur containing AA cysteine (bad smell w/ burnt hair)

Question 19

What is this? What does it do? What is it derived from?

Answer 19

It is a melanocyte, it produces pigment and transfers it to surrounding keratinocytes and there is about one per 10 keratinocytes; It is derived from neural crest + migrates during embryonic development

Question 20

What is one of the major immunologic cells in the epidermis? What does it do?

Answer 20

Langerhans (dendritic in dermis); it recognizes abnormal antigens and takes them up to present to lymphocytes in region LN’s; important in allergic rxns + tumor surveillance

Question 21

What cell in the epidermis is important for light touch sensation and can develop into malignant tumors?

Answer 21

Merkel Cells

Question 22

What is the Yellow Arrow? Blue arrow?

Answer 22

Yellow = Hair Follicle; Blue = Sebacious gland (Attached to a hair follicle)

Question 23

What is the primary cell in the dermis? What is it’s origin?

Answer 23

Fibroblast; mesenchymal origin

Question 24

What are fibroblasts responsible for? What triggers mitosis?

Answer 24

Synthesis and degradation of connective tissue proteins including collagen, elastin, glycosminoglycans and other glycoproteins; injury triggers mitosis and theyre also responsible for wound healing and scar formation

Question 25

What kind of cell is this? What kind of rash do they form when activated?

Answer 25

Mast Cell; Release granules (histamine) when triggered or when IgE binds during allergic rxn; cause characterisitic "Wheal and flare"

Question 26

Where do hair follicles extend into? What does each follicle have associated with it?

Answer 26

Into subcutis; sebaceous oil gland

Question 27

What is the pilosebaceous unit composed of? (4 things)

Answer 27

Hair follicle, sebaceous oil gland, apocrine sweat glands (in axilla and anogenital skin), arrector pili muscle (for goosebumps!)

Question 28

What is in the black circle? Where are they found in the body? Where do they open on to? What do they do?

Answer 28

They are the "true" sweat glands (eccrine glands) that are present throughout the body, opening directly onto the skin without being associated with a hair follicle and function in regulating temperature by evaporative cooling of sweat

Question 29

What does the subcutis do?

Answer 29

Fat layer that separates dermis from underlying structures (muscle, fascia, organs) and serves as insulation, energy, and protection

Question 30

What happened to these cells?

Answer 30

A sunburn; failure to delete damage cells could lead to skin cancer

Question 31

\*\*\*\*\*\*What's going on here?\*\*\*\*\*\*

Answer 31

Separation of the stratum basale and basement membrane due to **_autoantibodies against hemidesmosomes = Bullous Pemphigoid;_** here it is shown on IF (linear pattern) and in clinic. Will form thicker blisters becausehe whole epidermis is the blister.

Question 32

\*\*\*\*\*\*What's going on here?\*\*\*\*\*\*

Answer 32

Sepration of stratum basale and stratum spinosum due to **_autoantibodies agaisnt desmosomes = Pemphigus Vulgaris_**; Shown here is it on IF and in Clinic

Question 33

What is atopic Dermatitis associated with?

Answer 33

Genetic defects in filaggrin; Clinical examples shown here

Question 34

What is the specific genetic mutation that causes Epidermolysis Bullosa Simplex?

Answer 34

Mutations in Keratin 5/14; the blister forms when the K5 and K14 keratin filamens no longer hold cell together as shown in picture

Question 35

What is a nevus vs melanoma?

Answer 35

Nevus is a mole and is a benign collection of melanocytes whereas a melanoma is a growth of malignant melanocytes; melanocyte shown

Question 36

What is Hypohidrotic Ectodermal Dysplasia?

Answer 36

Genetic condition: Mutation in EDAR gene; protein for itneraction between ecto and mesoderm which results in abnormal hair follicles, sweat glands, and teeth = unable to regulate temp and overheat easily

Question 37

What's going on here?

Answer 37

Local thermoregulatory dysfunction a.k.a. Raynauds' phenomenon and is chronic episodic attacks of digital ischemia; can be provoked by cold; painful and can ulcerate; can be assocaited with underlying AI dz

Question 38

What's going on here?

Answer 38

Small vessel vasculitis; dz's that injure blood vessels + disrupt circulation = curatneous necrosis and/or ulceration; Here it is shown widespread due to Antiphospholipid antibody syndrome

Question 39

List the consequence of the following failures: 1. Maintain structural barrier 2. Immune surveillance 3. Repair injury 4. Regulate temp 5. Circulation 6. Communication 7. Photoprotection

Answer 39

1. Dehydration, infection 2. Infection, AI, cancer 3. Skin cancer, ulcers 4. Hypo/Hyperthermia 5. Infaction (emboli/vasculitis) 6. Itching, insensitivity 7. Cancer, photoaging

Question 40

What is the biologically "non-essential" function of the skin?

Answer 40

Appearance; it is how a person presents themselves which can effect perceptions and self-esteem, performance, and function