Defense & Barriers 2: Skin Basics

Question 1

layers of skin histo? (4)

Answer 1

stratum…

1. corneum
2. granulosum
3. spinosum
4. basale

Question 2

horses vs. dog/cat hair structure?

Answer 2

DOGS/CATS = have COMPOUND hair follicles, where MULTIPLE HAIR SHAFTS come out of ONE FOLLICLE, plush coat

HORSE = have SIMPLE hair follicles, one hair shaft per follicle

Question 3

DESMOSOMES vs. HEMIDESMOSOMES

Answer 3

desmosomes = adhesion proteins that bind KERATINOCYTES to each other

hemidesmosomes = link keratinocytes to ECM

Question 4

cadherin (what is it, what happens if we were to develop Abs against it)

Answer 4

protein that is found IN desmosomes that help HOLD keratinocytes together

if Abs attack it, EPIDERMIS LOSES STRUCTURE

Question 5

function of…
1. langerhan cells
2. melanocytes
3. merkel cells

Answer 5

1. langerhan cells = professional antigen-presenting cells that react with T and B cells to help generate inflammatory response
2. melanocytes = UV protection
3. merkel cells = TOUCH sensation, like when you brush fingertips against dog’s hair

Question 6

furunculosis definition & 3 stages of it

Answer 6

furunculosis = the RUPTURE of a hair follicle

inflammation –> folliculitis –> furunculosis

Question 7

3 parts of the hair follicle & what disease is most likely there for first 2

Answer 7

1. INFUNDIBULUM = TOP portion of hair shaft coming out of follicle, likely to have BACTERIAL infection
2. ISTHMUS = INTERVENING AREA between APOCRINE GLAND and ARRECTOR PILLI MUSCLES where AUTOIMMUNE disease likely
3. INFERIOR PORTION = includes DERMAL PAPILLA & HAIR BULB, dermal papilla sends signal to hair

Question 8

what usually causes folliculitis? (simple answer)

Answer 8

BACTERIA

Question 9

definitions…
1. anagen
2. catagen
3. telogen
4. exogen

Answer 9

1. ANAGEN = GROWTH phase
2. CATAGEN = IN-BETWEEN PHASE, REGRESSION of hair follicle
3. TELOGEN = RESTING phase, no longer growing
4. EXOGEN = SHEDDING of hair shaft

Question 10

why do shar peis have wrinkly coats? what can this cause?

Answer 10

wrinkly coat due to EXCESS HYALURONIC ACID, can then cause VESICLES to form on skin if too much

Question 11

what “disease” process is this from? common in what breeds?

Answer 11

formation of VESICLES from EXCESS HYALURONIC ACID in SHAR PEIS

Question 12

3 main functions of stratum corneum as a SKIN BARRIER
**include 4 types of things that can damage skin

Answer 12

1. prevent WATER LOSS
2. prevent ENVIRONMENTAL INSULTS (allergens, thermal, microbial, chemical)
3. PHOTOPROTECTION via MELANOCYTES & hair

Question 13

a mutation in WHAT part of the skin barrier can cause this? what is this?

Answer 13

mutation in LIPID formation can cause this!

EXCESSIVE SCALING/ichthyosis

Question 14

what 4 things can occur if stratum corneum is DISRUPTED?

Answer 14

1. loss of integrity/elasticity
2. water loss
3. inflammation
4. POSSIBLY pathogen entry

Question 15

cornification
what does it form?
3 steps
what happens if cornification cannot occur?

Answer 15

FORMS THE STRATUM CORNEUM

steps?
1. MODIFIED version of APOPTOSIS OF KERATINOCYTES where 70% of water is lost
2. CYTOPLASM/ORGANELLES is REPLACED BY KERATIN FIBRILS
3. CELL MEMBRANE BECOMES CORNIFIED ENVELOPE, creates CORNEOCYTES
4. CORNIFIED LAYERS become SANDWICHED BETWEEN LIPID

if cornification cannot occur, WATER LOSS and LOSS OF HYDROPHOBICITY –> SCALING

Question 16

3 characteristics of the skin barrier?

Answer 16

1. CONTINUOUSLY SHEDS via DESQUAMATION
2. is HYDROPHOBIC
3. has an INHERENT IMMUNE SYSTEM with LANGERHAN & DENDRITIC CELLS

Question 17

what 3 things does the skin do if the skin barrier is COMPROMISED?

Answer 17

1. INCREASED LIPID PRODUCTION
2. increased EPIDERMAL TURNOVER to make more LIPID
3. INFLAMMATION to protect against PATHOGENS

Question 18

how do we attain skin moisture? (3)

Answer 18

1. keratohyaline granules in corneocytes contain PROFILAGGRIN, which is then PHOSPHORYLATED to FILAGGRIN
2. FILAGGRIN then ANNEALS KERATIN TOGETHER
3. when KERATIN IS BROKEN DOWN, it RELEASES SUBSTANCES that MOISTURIZE THE SKIN

Question 19

transglutaminase 1 function

Answer 19

= helps to FORM THE CORNIFIED ENVELOPE by TAKING PROTEIN like KERATIN and COMPACTING THEM TOGETHER to replace the PLASMA MEMBRANE

Question 20

lamellar bodies
= what is their function?
how do they achieve that function? (2)
how do they change lipids?
what 4 things do their contents do/contain?

Answer 20

= ORGANELLES that help DEPOSIT LIPID BETWEEN CORNIFIED SKIN LAYERS

1. FATTY ACIDS from DIET or ENDOGENOUS sources will get LOADED INTO LAMELLAR BODIES
2. LAMELLAR BODIES migrate to JUNCTION between stratum GRANULOSUM and CORNEUM, and SUPPLIES LIPID TO CORNEUM

change lipids?
they change lipids from POLAR to NONPOLAR via ENZYMES

4 things their contents do/contain…
1. cohesion
2. hydration
3. cathelicidins/beta-defensins for INNATE immunity

Question 21

what process is this showing?

Answer 21

LAMELLAR BODY FUSION at the junction between stratum GRANULOSUM AND CORNEUM to DEPOSIT LIPIDS IN CORNEUM

Question 22

what 3 things is the FINAL STRATUM CORNEUM made up of?

Answer 22

1. cholesterol
2. free fatty acids
3. ceramides

Question 23

acanthosis definition
what big disease can this be found?

Answer 23

= EPIDERMAL HYPERPLASIA

found in CANINE ATOPIC DERMATITIS

Question 24

spongiosus

Answer 24

INTERCELLUAR edema between EPIDERMAL KERATINOCYTES

Question 25

hyperkeratosis definition
relation to orthokeratotic? and parakeratotic?

Answer 25

hyperkeratosis = THICKENING OF STRATUM CORNEUM

ORTHOkeratotic = resembles NORMAL stratum corneum

PARAkeratotic = ABNORMAL stratum corneum, retained nuclei

Question 26

acantholytic keratinocyte/acantholysis

Answer 26

= when keratinocytes are no longer joined TOGETHER in the epidermis due to breakdown of DESMOSOME intercellular bridges