Integument (skin) Flashcards
What are the functions of the skin?
Protection against external agents, UV rays, and water loss
Regulates temp. And ion-water balance
Calcium homeostasis
Sensory application
Fat storage
What does the clinical examination of the skin reveal?
Ecto-parasites and internal disease processes resulting from endocrine and nutritional disorders
What we the two parts of the skin?
Epidermis and dermis
Epidermis
Stratified squamous keratinized epithelium
4-5 different layers
What are the 2 dermis layers?
2 layers: papillary and reticular
Hypodermis
Not apart of the skin
Superficial fascia (site for Sub-Q injections)
Sweat glands present
Loose CT filled with fat
What are the layers of thick skin?
- Basale (germinativum)
- Spinosum
- Granulosum
- Lucidum (absent in thin skin)
- Corneum
Spinosum Layer
Mitotic cells (also in basale)
Tonofilaments (thick keratin bundles)
Spiny appearance
Granulosum Layer
Non-membrane bound, basophilic, keratohylain granules
Membrane-bound lamellar granules, with phospholipids
Keratinocyte
Most abundant and contains melanin
Synthesize soft keratin, protect from invading organisms and dehydration
Melanocyte function
Synthesize melanin and protect from UV light
Melanocyte
10%, in malpighian layer and hair follicles
Originates from the neural crest cell
Doesn’t divide
Why can melanocytes synthesize melanin?
Because they contain tyrosinase enzyme that convert tyrosine to amino acid
How do melanocytes differ among people?
Their ability to synthesize melanin and transfer melanin into keratinocytes (not the #)
_______ are a malignant growth of melanocytes
Melanoma
Langerhans cells
Macrophages (antigen presenting cells) that protect from organisms
Originates from monocytes
Merkel’s cells
Sensory mechanoreceptors
In thick skin
Innervated by sensory nerves
How do you distinguish melanocytes from keratinocytes?
Dihydroxyphenylalanine reaction (DOPA)
M: DOPA +
K: DOPA -
Cytocrine
Mode of secretion where melanocyte injecting melanin into the adjoining keratinocytes (cytoplasm to cytoplasm)
Melanogenesis
- Tyrosinase is synthesized in the RER and accumulated in vesicles of the Gogli complex
- Synthesis begins in melanosomes (free vesicles)
- Melanin granules migrate to the tips of the melanocyte’s processes, then transferred to keratinocytes
Thin skin characteristics
Basal layer: one layer of cells
Spinosum: 2-3 layers of cells
Granulosum: one layer
Lucidum: absent
Corneum: few layers of keratinized, dead cells
Hair, sebaceous and apocrine sweat glands present
Thick skin characteristics
Basal layer: one layer of cells
Spinosum: many
Granulosum: 3-4
Lucidum: present
Corneum many layers of keratinized cell
Hair, and sebaceous glands absent, merocrine sweat glands present
Papillary layer
Loose irregular CT
More vascular and cellular than reticular layer
Major part of the dermal papilla
Reticular layer
Dense irregular CT
Type 1 collagen and elastic fibers
Smooth muscle ( are your pilorum)
Nerve fibers and receptors
Deep of subcutaneous plexus blood supply
In hypodermis
Formed by large vessels
Dermis-hypodermis junction
Middle of cutaneous plexus blood supply
Hairs and glands of the dermis
Superficial subpapillary plexus
Supplies papillary layer and epidermis
Superficial arterio-venous anastomoses
Thermoregulatory structures
In papillary layer of pig and man, absent in other domestic species
Sebaceous skin glands
All over body (except foot pad)
Hair follicles (except lip, penis and vulva)
Holocrine
What kind of secretion do sebaceous glands release?
Sebum, that lubricates the hair shaft, protects skin from drying, diminishes water loss and contains Vit. D
Examples of sebaceous glands
Infraorbital, inguinal and interdigital regions of sheep
Base of horns in goats
Anal sacs of cats
Prepuce and circumanal region of dogs
What modes of secretion is used for sweat?
Merocrine and apocrine
Species variation for sweat glands
Absent in rats and birds
Poorly developed in dogs and pigs
Apocrine glands
Abundant in most domestic species
Profuse secretion in horses
Least active in goats and cats
Apocrine gland function
Produce viscous secretion that serves as a sex attractant in some species
Regulate temperature (horse and cattle)
Where are merocrine glands present?
Present in foot pads of dogs and cats
Frog of horse hooves
Planum nostral and carpal glands of pigs
Planum nasolabial of cattle
How is sweating controlled in domestic species?
Smypathetic cholinergic nerve fibers
How is sweating controlled in horses?
Sympathetic adrenergic fibers
What is the secretory portion of merocrine sweat glands?
Simple columnar epithelium underlain by myoepithelial cells
Large lumen
Apical protrusions
What is the duct portion of the merocrine sweat glands made of?
Stratified cuboidal epithelium
How are the hair beds in the pig, dog and cat?
2-4 clusters of hair follicles
1 principal (guard) hair
3-9 auxiliary (wool) surrounding hairs
What does a complete hair consist of?
Hair shaft
Hair follicle
Root
Bulb
Papilla
Hair shaft
Free threadlike part above the skin
Consists of: medulla (soft keratin), cortex(hard keratin), cuticle
Root
Portion of the hair beneath the skin
Hair follicle
Sheath covering the root
Consists of CT sheath, glassy membrane, external root sheath, internal root sheath
Inner root sheath
Contain pink trichohyalin granules
Ends at the level of sebaceous glands
External root sheath
Extension of the stratum basal layer of the epidermis
Covers surface of hair bulb
Gives rise to all parts of the hair
Hair bulb
Extended part of the hair follicle where hair is rooted
What is the hair bulb indented by?
Dermal papilla which contains blood vessels
Arrector Pili
Bundle of smooth muscle attached at an angle to the CT sheath of the hair follicle
What does sympathetic stimulation of arrector pili cause?
Elevation of hair
Important in thermoregulation
What separates the dermis and the epidermis?
Basement membrane
What is the most common types of hair?
Cover hair
Wool hair
Fine, wooly undercoat”
Sheep or goat
Tactile (sinsus) hair
Whiskers in carnivores
Blood sinus present in CT sheath of hair follicle
Sensory innervation (tactile)
Hair cycle
Hair production is cyclic (seasonal)
Controlled by light and temp.
Germinal area of follicle quiescent or mitotic
What are the hair cycle stages?
Anagen (active growth)
Catagen (involution)
Telogen (resting)
How is hair color created?
By melanocytes present in the germinal matrix covering the dermal papilla
Keratohyaline
Soft keratin
High lipid content
Low sulfur content
Cells desquamate
Trichohylaine
Hard keratin
Hair, horn, feathers
Low lipid content
No desquamation
