Ch 1 Structure and Function Flashcards
Fetal skin contains a larger percentage of what type of collagen compared to adult skin?
collagen III (adult skin has more type I collagen)
What is different about where appendages such as the arrector pili muscle, sebaceous glands, epitrichial sweat glands form in primary vs. secondary hair follicles?
in primary - appendages develop on cranial side; in secondary - appendages develop on the caudal side
T/F: At birth, the majority of hair follicles of dogs are primary follicles.
True - secondary follicles develop caudal to the primary hairs during the first 12-28 weeks of life.
Is the skin surface of haired mammals generally acidic or basic?
acidic - but it is influenced by gender, coat color, breed, species
T/F: In cats, secondary hairs are more numerous than primary hairs.
True - 10:1 dorsally, 24:1 ventrally
Layers of the hair follicle near the dermal papilla (inner to outer)
hair medulla –> hair cortex –> hair cuticle –> Huxley’s layer –> Henle’s layer –> outer root sheath –> basement membrane –> fibrous sheath
Hormones that stimulate the hair cycle (induce or prolong anagen)
thyroid hormones, corticotropin, melatonin, androgens, growth hormone
Hormones that inhibit the hair cycle (inhibit anagen, induce catagen, and/or prolong telogen)
cortisol, estrogen, corticotrophin-releasing hormone, corticotropin, prolactin, parathyroid-related peptide
Growth factors that stimulate the hair cycle (induce or prolong anagen)
Fibroblast growth factor (FGF) - 7; hepatocyte growth factor; insulin-like growth factor-1; Sonic hedgehog; Keratinocyte growth factor, WNTs, beta-catenin, TGF-alpha; nerve growth factor; GDNF
Growth factors that inhibit the hair cycle (inhibit anagen, induce catagen, and/or prolong telogen)
epidermal growth factor; fibroblast growth factor (FGF)-2, FGF-5; brain-derived neurotrophic factor; neurotrophin 3,4; TNF-alpha; TGF-beta-1, TGF-beta-2
Cytokines that stimulate the hair cycle (induce or prolong anagen)
TGF-alpha
Cytokines that inhibit the hair cycle (inhibit anagen, induce catagen, and/or prolong telogen)
Interleukin-1, IL-6
Does this substance inhibit or stimulate the hair cycle: activin?
stimulate
Does this substance inhibit or stimulate the hair cycle: noggin?
stimulate
Does this substance inhibit or stimulate the hair cycle: follistatin?
stimulate
Does this substance inhibit or stimulate the hair cycle: cyclosporine?
stimulate
Does this substance inhibit or stimulate the hair cycle: minoxidil?
stimulate
Does this substance inhibit or stimulate the hair cycle: finasteride?
stimulate
Does this substance inhibit or stimulate the hair cycle: retinoids?
inhibit
Does this substance inhibit or stimulate the hair cycle: calcitriols?
inhibit
What is the ratio of primary to secondary hairs in the “normal coat”? What breed is an example of this coat?
high proportion of hairs by number are secondary hairs; GSD, Welsh corgi, wolves, coyotes
What is the ratio of primary to secondary hairs in the “coarse short coat”? What breed is an example of this coat?
strong growth of primary hairs and less secondary hairs; Rottweiler and terriers
What is the ratio of primary to secondary hairs in the “fine short coat”? What breed is an example of this coat?
largest number of hairs per unit, secondary hairs are numerous and well-developed, primary hairs are reduced in size compared to those of the normal coat; Boxers, daschunds, miniature pinschers
Characteristics of the fine long coat? Breeds with this type of coat?
greater weight of hair per unit area than the normal coat, except in toy breeds; Cocker Spaniel, Pomeranian, Chow Chow
Characteristics of the woolly or coarse long coat? Breeds with this type of coat?
secondary hairs make up 70% of the total weight and 80% of the number of hairs; Poodle, Bedlington terrier, Kerry Blue terrier - less tendency to shed than many breeds
Activation of melanocortin 1 receptors on melanocytes leads to production of what type of pigment?
eumelanin
Inhibition of melanocortin 1 receptors on melanocytes leads to production of what type of pigment?
pheomelanin
The shade of eumelanin is controlled by what gene?
tyrosinase related protein 1 gene
What color gene results in a gradual replacement of eumelanin with phaeomelanin? What breed/species of animal is this recognized in?
amber gene (E); Norwegian Forest cats
What breed of cats have a temperature-dependent enzyme that converts melanin precursors into melanin by a process of oxidation?
Siamese, Himalayan-Persian, Balinese, Birman
The dilution gene (D, melanophilin, MLPH) dilutes black to blue (gray), orange to cream, and seal-point to blue-point. How is it inherited?
autosomal recessive
Cornish or Devon rex: lacks primary hairs
Cornish rex
Cornish or Devon rex: has primary hairs that resemble secondary hairs
Devon Rex
Cornish or Devon rex: absent or stubbled whiskers
Devon rex
Cornish or Devon rex: short and curly whiskers
Cornish Rex
Cornish or Devon rex: absent coat on chest, belly, shoulders
Devon Rex
What are Voight lines
boundaries of the areas of distribution of the main cutaneous nerve stems
What are langer lines
course of blood vessels or lymphatics
What are Blaschko lines
pattern assumed by many different nevoid and acquired skin diseases
What are the four cell types within the epidermis?
keratinocytes, melanocytes, Langerhans cells, Merkel cells
Layers of the epidermis (inner to outer)
stratum basale –> stratum spinosum –> stratum granulosum –> stratum lucidum –> stratum corneum
What is the normal thickness of the epidermis in dogs and cats?
2-3 nucleated cell layers (not counting horny layer) in haired skin
T/F: The surface of footpad epidermis is smooth in cats but papillated and irregular in dogs.
True - rete ridges (projections of epidermis into the underlying dermis) are normal to find in the footpad and nasal planum epidermis (and in lightly haired scrotum)
What keratins are present in the stratum spinosum?
retain keratin-5/keratin-14, synthesize K1/K10
T/F: The stratum granulosum is always present in haired skin.
False - variably present, ranges from 1-2 cells thick in areas where it occurs
Where are keratohyalin granules synthesized?
stratum granulosum
What do keratohyalin granules contain?
profilaggrin, keratin filaments, loricrin
Filaggrin degradation produces what? What is the purpose of these products?
urocanic acid, pyrrolidone carboxylic acid – important for normal stratum corneum hydration and help filter UV radiation
What is loricrin?
cystine-rich protein synthesized in the stratum granulosum; involved in binding keratin filaments together in the corneocyte and choring them to the cross-linked envelope
Where is the stratum lucidum best developed?
footpads, less developed in nasal planum and absent from all other areas of normal skin
What differentiates the stratum lucidum from the stratum corneum?
rich in protein-bound lipids; contains a semifluid substance called eleidin
T/F: The corneocytes has no true cell membrane.
True - because it contains no phospholipids; instead has the cornified envelope
What are transglutaminases? Deficiencies can result in what clinical disease?
enzymes that are important in apoptosis, keratinization, hair follicle formation; ichthyosis
Where in the epidermis are transglutaminanses chiefly expressed?
stratum granulosum and upper stratum spinosum; they require catalytic amino acids and calcium
