Skin Flashcards
What are the primary functions of the skin?
- Mechanical barrier/protection
- Prevent electrolyte, water loss
- Radiation protection
- Elasticity for movement
- Immune defense
- Temperature regulation
Additional functions include nerve receptors for perception and storage/excretion of vitamins and other substances.
What components make up the integument?
- Subcutis (Hypodermis)
Cutis: - Dermis
- Epidermis
- Modified skin structures (e.g., hair follicles, footpads)
The integument serves various roles, including protection and sensory functions.
What is the role of the subcutis?
- Loose connective tissue
- Insulation
- Energy storage
- Protection (e.g., footpad digital cushion)
The thickness of the fat in the subcutis varies by body region.
What are the two layers of the dermis?
- Papillary dermis 20%
- Reticular dermis 80%
The papillary dermis nourishes the epidermis, while the reticular dermis provides strength and flexibility.
How many layers does the epidermis have, and what are they?
- Stratum basale
- Stratum spinosum
- Stratum granulosum
- Stratum lucidum (only in footpad/nasal skin)
- Stratum corneum
The epidermis typically has 4-5 layers.
What is the function of keratinocytes in the epidermis?
Keratinocytes are produced in the stratum basale and move up to the skin surface, differentiating and undergoing cell death before sloughing off in 20-30 days.
This process is crucial for the renewal of skin cells.
What is a mucous membrane?
A layer of cells that surrounds body organs and orifices, containing or secreting mucus to protect surfaces.
Mucous membranes are found in the respiratory, digestive, and reproductive systems.
What are the three layers of mucosa?
- Epithelium
- Lamina propria
- Muscularis mucosae
These layers play a role in capturing foreign particles and providing a barrier.
What are the three main types of hair?
- Primary hairs (guard hairs)
- Secondary hairs (undercoat)
- Tactile hairs (found on face and head)
Each type of hair serves different functions and varies between species.
What are the phases of the hair cycle?
- Anagen (active growing phase)
- Catagen (transitional phase)
- Telogen (resting phase)
Hormones influence the hair cycle phases.
What is the role of sebaceous glands?
Sebaceous glands secrete sebum, which provides antimicrobial properties and contributes to skin hydration.
Sebaceous adenitis is a condition that affects these glands.
What is the skin microbiome?
The skin microbiome consists of normal symbiotic organisms that inhabit the skin and play a role in health.
Levels of these microbes can be affected by various environmental factors.
What are the resident bacteria commonly found on canine skin?
- Micrococcus spp.
- Coagulase-negative staphylococcus
- Alpha hemolytic streptococcus
- Clostridium spp.
- Propionibacterium acnes
- Acinetobacter spp.
- Staphylococcus pseudintermedius
These bacteria are part of the normal skin flora.
True or False: Neutrophils and macrophages are phagocytic cells that engulf foreign material.
True
They also produce cytokines to attract other immune cells.
Fill in the blank: Vitamin A is critical for _______.
[epidermal differentiation and normal sebum production]
Vitamin A is often used to treat keratinization disorders.
How does temperature affect skin health?
- Low temperature can cause frostbite
- High temperature can lead to sunburn and other skin cancers
Extreme temperatures can damage the skin.
What is the purpose of a Woods lamp examination?
To identify fluorescing hairs indicative of fungal infections, such as M. canis.
Positive predictive value is 90%, negative predictive value is 94%.
What is the significance of Toll-like receptors in keratinocytes?
They recognize pathogens and establish an immune response.
This plays a critical role in the skin’s defense mechanism.
What factors can influence the skin microbiota?
- Breed
- Nutrition
- Hygiene
- Environmental conditions
These factors can affect the diversity and health of the skin microbiome.
What is the purpose of PCR in dermatology?
To detect dermatophyte DNA
PCR stands for Polymerase Chain Reaction, a technique used to amplify DNA sequences.
What does a positive Wood’s lamp examination indicate?
M.canis (apple green fluorescence)
M.canis refers to Microsporum canis, a common dermatophyte affecting cats.
What is the common finding in untreated cats during a Wood’s lamp examination?
Fluorescing hairs
Fluorescing hairs are typically easier to find in untreated cats than in treated ones.
What is the positive predictive value of Wood’s lamp examination?
90%
The positive predictive value indicates the probability that subjects with a positive screening test truly have the disease.
What is the negative predictive value of Wood’s lamp examination?
94%
The negative predictive value indicates the probability that subjects with a negative screening test truly do not have the disease.
What can cause false positive and false negative results in Wood’s lamp examination?
Inadequate equipment, lack of magnification, patient compliance, poor technique, lack of training
These factors can significantly affect the accuracy of the examination.
What type of samples are taken for direct examination?
Scrapes of alopecic lesions or plucks from periphery
Alopecic lesions refer to areas of hair loss.
What substances are used to mount hairs and scales in direct examination?
Mineral oil, potassium hydroxide (+/- LCB or India ink) or compounded chlorphenolac
KOH (potassium hydroxide) is used to clear debris and enhance visibility of the samples.
What is the sensitivity range of direct examination for dermatophytes?
41-61%
Sensitivity refers to the test’s ability to correctly identify those with the disease.
What type of cases might direct examination pick up that Wood’s lamp may miss?
Cases negative on Wood’s lamp
Direct examination can identify dermatophyte infections that do not fluoresce under Wood’s lamp.
What cell types are on the dermis
Fibroblasts, mast cells, histiocytes, dendrocytes
What is the papillary dermis made off
Loose connective tissue with capillaries elastic fibres reticular fibres, collagen within ground substance
What is reticular dermis made off
Dense connective tissue, blood vessels, elastic fibres, collagen fibres, mast cells, nerve endings, lymphatics within ground substance
Name other structures within dermis
Sebaceous glands, sweat glands, arrector pili muscles, hair follicles
How thick is the stratum corneum
12-15 um
45-52 layer thick
How thick is the stratum granulosum+stratum spinosum+ stratum basale
8-12um
3-4 layers thick
How thick is haired skin
0.1-0.5mm
How thick is footpad and planum nasale
up to 1.5mm
What layer is stratum basale
basal cell layer
what layer is stratum spinosum
prickle cell layer
what layer is stratum granulosum
granular cell layer
what layer is stratum lucidum
clear cell layer (footpad/nasal skin)
What layer is stratum corneum
horny cell layer
How is the basal cell layer arranged
most keratinocytes arranged in rows
basal cells attached to BMZ by hemidesmosomes
Mitotic activity provides for continual renewal of skin cells
How is the spinous layer arranged
spines- desmosomes cell: cell adhesion
desmosomes continous with keratin intermediate filaments
intermediate filamates aggregate into keratin bunflrd
thick in gootpads
lamellar bodies start to form
Damage in spinous layer
adhesion between spinous cells
Damage in basal cell layer
adhesion of basal cells to BM
adhesion of basal cells to prickle cells
How is the horny cell layer arranged
multiple layers flattened polygonal cells- form a thick waterproof cell membrane
cells keratinised with thickened cell envelops
cells contain aggregated keratin bundles within cornified envelope
Describe the muscularis mucosae
Deepest layer of the mucosa, a layer of smoooth muscle provide a perpetual motor function that keeps mucosa in flux
Describe the lamina propria
epithelium attaches to a loose connect tissue, middle layer is called lamina propria
composed of structural protein molecules, nerves and veins
Describe the epithelium of the mucosa
surface layer, cells arranged depends on body site, in mouth stratified squamous epithelium, in some site the epithelium has cilia
2 types of hair follicles
simple primary
compound: primary with secondary follicles
What type of hair follicles do dogs, cats, sheep and goats have
compound follicles, several hairs in a single folliclule opening, sheep are mostly secndary hairs
What type of hair follicles do horse, cattle, pigs and humans have
simple follicle single primary guard hair
What happens in the anagen hair phase
acitve growing phase
dermal papilla deep in dermis and anchored firmly by root sheath
What happens in the catagen hair phase
intermediate/transitional phase
hair starts to become more superficial as bulb moves away from papilla
What happens in the telogen hair phase
resting phase
hair is now dead, located very superficially and held loosely in follicle
What hormones affect hair cycle
steroid
thyroxin
How does steroid affect hair cycle
prolongs telogen
how does thyroxin affect hair cycle
stimulates anagen
2 types of sebaceous gland
found in hairs (open into infundibulum)
free sebaceous gland (meibomian glands-eyelids)
Describe epitrichial sweat gland
opens into infundibulum
Describe atrichial sweat gland
opens onto skin
Name 2 types of sweat gland
epitrichial
atrichial
atrichial vs epitrichial secretion
epitrichial- not inervated merocrine secretion of albuminous sweat
Atrichial- innervated merocrine secretion to produce watery sweat onto skin surface (eg.footpads)
How does the skin recognize pathogens
keratinocytes and langerhans cells bear toll like receptors that recognize and establish a highly coordinated immune response
What do keratinocytes and langerhans do to neutralise pathogens
produce AMP to neutralise pathogens, inflammatory mediates alert immune cells, activate innate immune cells like NK cells, neutrophils, macrophages and eosinophils
How do natural kills cells work
they are cytotoxic lymphocytes activated by interferons or cytokines and can eliminate virally infected cells and cancer cells by penetrating the cell and releasing toxic granules into abnormal cell
granules, create holes in the cell which swell, burst and die
Why is protein important for skin
important for normal keratinization, pigmentation and hair growth
why is essential fatty acids important for skin
important for sebum productions especially linoleic acid
why is vitamin c importatn for skin
necessary for collagen sysnthesis/cross- linking
why is vitamin e important for skin
primary antioxident in the cell membrane
why is copper importatn for skin
serves as a cofactor in enzymatic conversion of tyrosine to melanin
deficiency can cause changes in pigmentation
why is zinc important for skin
criticcal for transition of nucleated epidermal cells to anucleate squamous cells in stratum corneum
deficiency seen in husky as congenital diseas and fast growing dogs on cereal or calcium diet
develop dry scaling lesions over pressure points and face
Name 4 important husbandry and environmental factors for skin
nutrition-deficiency or excess
temperature-extremes
sunlight- AI or photsensitisation
Hygiene-infection
How does steroid affect hair cycle
prolongs telogen
how does thyroxin affect hair cycle
stimulates anagen
