Skin Flashcards
Definition
Largest organ in the mammalian body
Comprised of an epithelial covering, it’s derivatives (hair, glands, horns, hooves, etc.), and associated CT
Functions
Protection Regulation of body temperature Secretion Sensory Organ Communication Reflects physiological condition of the animal
Organization
Epidermis & dermis
Epidermal cell types
Keratinocytes
Langerhans cells
Melanocytes
Merkel Cells
Layers of Epidermis
Stratum basale/germinativum Stratum spinosum Stratum granulosum Stratum lucidum Stratum corneum
Keratin - types
Soft keratin
Hard keratin
Keratinization/Formation of Keratin
- Synthesis of filaments in stratum basale - synthesizes 2 of 4 keratin subtypes
- Aggregation of filaments 0 in superficial cells of stratum spinosum
- Stratum spinosum cells form membrane-coating granules that eventually release lipid-rich contents into intercellular space forming a waterproof permeability barrier
- Keratohyalin granules - non membrane bound - appear in close association w/filaments in s. granulosum and non-keratin proteins released by them cause keratin to associate into thicker bundles
Keratohyalin granules also sequester non-keratin proteins (loricrin and filaggrin and keep them separated from other cellular constituents until they are required in stratum lucidum for keratin filaments to form macrofibrils - Degradation of nucleus and loss of cellular organelles - begins in most superficial layer of the stratum granulosum and is completed in stratum lucidum and corneum
- formation of a filament-matrix complex of keratin - in stratum corneum
Layers of Dermis
Papillary layer
Reticular layer
Dermis - definition
= corium
layer of skin immediately deep to epidermis
derived from mesoderm
composed of connective tissue
most accessory structures are embedded in here
Hypodermis
subcutaneous layer/superficial fascia that isn’t part of the skin
consist of looser irregular CT
anchors dermis to underlying CT of deep fascia, perocondrium, etc
Depots of fat are here in animals of good condition
Accessory structures of the skin
Hair, sweat glands, sebaceous glands
derived from epidermis
anchored in dermis or hypodermis
Function - Protection
most important characteristic
barrier between internal and external environments
guards against injury, bacterial invasion, UV damage, desiccation
Function - regulation of body temperature
insulation - mediated by hair coat & adipose tissue
heat dissipation - cutaneous blood supply and sweat glands (in some animals)
Function - secretion
from sweat, sebaceous, and mammary glands
Function - Sensory organ
largest sensory organ of the body
provides pain, touch, pressure, and temperature sensation
Function - communication
gives off odors that govern sexual behavior
helps animals ID each other and their territories
Function - reflects physiological condition of the animal
may reflect internal and external disease processes
endocrine disorders, nutritional problems (i.e. Vitamin A deficiency)
Epidermis
stratified squamous epithelium
ectodermal origin