Skin function & structure Flashcards
Name 6+ skin functions.
Physical and protective barrier
Insulation
Thermoregulation
Skin metabolism
Hormone conversion-vitamin D production
Immune function (biological barrier)
Sensory apparatus
Excretory function
Storage (H2O, lipids)
Adnexa production (sweat, sebaceous glands, hairs, claws, erector pili muscles)
etc. etc.
Puppy vs adult dog skin makes up how much of their body weight percentage.
Puppy - skin makes up 24% of its body weight
Adult dog - skin makes up 12% of their body weight
Feline vs canine skin thickness.
Feline 0.4- 2.0 mm thick
Canine 0.5- 5.0 mm skin
Skin pH range.
pH 4.84- 9.95
Skin layers. (3)
epidermis
dermis
hypodermis
The subcutis or hypodermis consists of
Consists of fat and connective tissue.
Is an energy reservoir, capable of thermogenesis, insulation, protective padding, surface contour,
steroid reservoir, estrogen production etc.
The dermis consists of
Consists of insoluble fibers (collagen, elastin)
and soluble polymers like hyaluron. This is what gives skin elasticity.
Most of the “skin” is dermis.
All hair follicles, sebaceous glands, sweat
glands, but also lymph and blood vessels are
located in the dermis.
The epidermis contains 4 types of cells:
give percentages too
1) Keratinocytes (85%)
2) Melanocytes (5%)
3) Langerhans cells (3-8%)
4) Merkel cells (2%)
Langerhans cells make up 3-8% of skin cells. They are…
a type of dendritic immune cell found in the epidermis, primarily in the stratum spinosum layer. They play a crucial role in the immune response by detecting and processing foreign substances, such as pathogens or allergens.
- Antigen Presentation
- Immune Surveillance
- Tolerance Induction: Help in maintaining immune balance by preventing unnecessary immune reactions to harmless substances (e.g., preventing allergic reactions or autoimmune responses).
Merkel cells make up 2% of skin cells. Merkel cells are…
specialized mechanoreceptor cells found in the epidermis. They are primarily responsible for touch sensation and play a role in fine tactile discrimination.
Epidermis layers
- Horny layer (stratum corneum) - outer
layer
(clear layer - stratum lucidum) - Granular layer (stratum granulosum)
- Spinous layer (stratum spinosum)
- Basal membrane (stratum basale)
The Keratinisation process takes how long?
22 days
12Development - differentiation of
keratinocytes.
Cells become flat, they loose nucleus and
other structures by autophagy, keratin is
produced.
Keratinocyte, corneocyte, squamous cell,
epithelial cell
Produced on basalmembrane - move
upwards until being shed as corneocytes
most common autoimmune skin disease in small animals
pemphigus foliaceus
desmosomes in skin get attacked by immune system
Describe Melanogenesis and melanocytes.
Melanocytes are specialized cells located in the stratum basale of the epidermis that produce melanin.
They make up about 5-10% of epidermal cells and transfer melanin in melanosomes to keratinocytes through cellular extensions.
- melanocyte to 10-20 keratinocytes
- Melanin granules are pigment-containing organelles found inside melanosomes.
- Melanin functions as UV protection.
Skin adnexa is located in the…?
Give examples of skin adnexa. (3)
dermis.
- Hair
- Sebaceous glands
- Sweat glands
Sweat and sebaceous glands open into…?
Where are they in increased numbers?
Where are they not found?
they open into the hair follicle.
There are more sebaceous glands on dorsal aspects of neck, chin, dorsal part of the tale.
There are no sebaceous glands on nose and pawpads.
Stud Tail (Tail Gland Hyperplasia) in Dogs
Stud tail, or “tail gland hyperplasia”, is an enlargement of the oil glands near the base of your dog’s tail. These glands are located on the top side of the tail, a few centimeters from the top.
When the glands enlarge, they compress the hair follicles, causing hair loss. They also produce oil, which plugs hair follicles, makes the fur greasy, and makes the skin scaly. Inflammation and secondary infection can then occur.
Can lead top pyoderma.
The most common cause of stud tail is an excess of androgen sex hormones including testosterone. Intact males are most often affected; however, it can occur in any dog, even if they have been spayed or neutered.
Hairs grow in hair follicles.
Simple follicles are found in what species?
Compound follicles are found in what species?
Simple follicles are found in the pig, horse & in cattle.
Compound follicles are found in the cat and dog.
Compound meaning there are many hairs in clusters (both primary and secondary hair).
Primary hair is …?
Secondary hair is …?
Primary hair is strong, it has erector
pili muscle, sweat glands and sebaceous
glands.
Secondary hair is soft, may only have
sebaceous gland.
No new hair follicles are produced during
life.
Animals don’t lose their puppy coat. They only
have secondary hair in the beginning and
gain primary hair later!
The hair growth cycle:
- Anagen – growing phase
- (Katagen – regression phase)
- Telogen – resting phase
- (Eksogen – shedding phase)
In anagen, the hair is…
In telogen, the hair is…
- Anagen - hair is growing
- Telogen – “resting”, the hair is “dead” but stays in hair follicle.
Telogen effluvium is…
is a temporary, diffuse hair shedding condition caused by a disruption in the hair growth cycle. It occurs when a significant number of hair follicles prematurely enter the telogen (resting) phase, leading to increased hair shedding.
Stress, systemic disease might cause telogenisation of all hairs - hairs will fall off simultaneously causing hair loss.
Hair growth is affected by: (6+)
- Photoperiod
- Ambient temperature
- Nutrition
- Hormones
- General health
- Genetics
- Other factors..
Outdoor dogs shed twice a year, indoor doors may shed year round due to artifical light.
Name some important factors affecting hair growth. (3)
nutrition
light
hormones
mechanical irritation
