Block III - Integument Flashcards
What are the three layers of skin?
1) Epidermis
2) Dermis
3) Hypodermis
What are the characteristics of the epidermis?
Features keratinized cells; derived from the ectoderm
What are the characteristics of the dermis?
Features papillary (loose CT, vascularized) and reticular (deep layer; dense CT) layers
What are the characteristics of the hypodermis?
Features loose CT and adipocytes
Stratum Basale
Connects to the basal laminae;
single layer of cells;
features hemidesmosomes (attach epidermal cells to the extracellular matrix)
ALIVE and ACTIVE (mitotic activity)
Stratum Spinosum
“Spiny” layer due to increased tonofilaments and desmosomes
ALIVE and LESS ACTIVE
Stratum Granulosum
Features keratihyalin (gives rise to eleidin molecules in the Lucidum layer) and lamellar (waterproof) granules
ALIVE and INactive
Stratum Lucidum
Keratinized layer with no organelles (thick skin ONLY!)
DEAD and INACTIVE
Stratum Corneum
“Cornified” - Thick layer of entirely keratinized cells
VERY DEAD
Langerhan’s Cells
Intra-epidermal macrophages;
These cells are antigen presenting in T-cells and mediators of tolerance against viruses
Merkel’s Cells
Located in the stratum basale;
act as sensory mechanoreceptors for cutaneous sensations and contain free nerve endings at the base of the cell
Melanocytes
Located in the stratum basale;
Produces melanin pigment which protects the nucleus from UV radiation;
melanin is transferred to keratinocytes of stratums basale and spinosum;
require tyrosinase for proper function
Thick skin
Hairless with merocine sweat glands (i.e. paw and nose pads)
Thin skin
Features hair follicles with arrector pili muscle; has sebaceous glands and aprocrine sweat glands
Epidermal pegs
downward projections visible in the Dermo-epidermal layer
Dermal papillae
Upward projections visible in the Dermo-epidermal layer; present at the bottom of hair follicles
vascularized - carries blood supply to surrounding region
Hair shaft
rises above the skin surface
Hair root
Present within the hair follicle and contains a bulb ending
Medulla
loose cuboidal cells with air pockets located within the hair follicle
Cortex
Dense, keratinized cells located between the hair cuticle and medulla
Cuticle
single layer of keratinized cells;
forms the outermost layer of the hair shaft
Glassy membrane
Thick basement membrane located within the root shaft
External root sheath
continuous with the epidermis;
adjacent to the glassy membrane
Internal root sheath
layer of squamous cells;
features another cuticle that runs opposite to the hair cuticle
Primary Follicle
Large diameter;
features sebaceous glands, arrector pili muscles, and sweat glands
Secondary Follicle
Smaller diameter; may contain sebaceous glands
Arrector Pili Muscle
Smooth muscle responsible for goosebumps (contraction) and insulation
Sebaceous glands
Produces sebum (lipids and cell debris) through holocrine secretion;
used for antibacterial and waterproof coating
Apocrine sweat glands
Apical budding via apical secretory caps;
Myoepthelial cells responsible for product expression;
Merocrine/Eccrine sweat glands
Secretion via exocytosis;
responsible for thermoregulation and electrolyte balance
Stratum Externum
Outermost layer of the hoof (the “glaze”);
continuous with the perioplic epidermis
Stratum Medium
Supportive layer of the hoof;
features the tubular and intertubular groove
Stratum Lamellatum/Internum
Features the Lamellar horn (insensitive laminae)
Laminar corium
Sensitive laminae (derived from dermis)
Nociceptors
Free nerve endings responsible for detecting pain, itch, and temperature
Meissner’s corpuscles
Encapsulated nerve ending responsible for detecting light pressure/touch
Pacinian’s corpuscle
Encapsulated nerve ending responsible for detecting deep pressure
Ruffini’s corpuscle
Encapsulated nerve ending responsible for detecting stretch
Which layer is the sensitive laminar derived from?
Dermis
Which layer is the insensitive laminae derived from?
Epidermis
What is the function of Ceruminous glands and what kind of secretion does it use?
Ear wax; apocrine secretion
What the function of Uropygial glands and what kind of secretion method does it use?
The preen gland in birds;
Type of sebaceous gland (holocrine secretion)
What the function of Meibomian glands and what kind of secretion method does it use?
Help to keep eyes moist (located in the eyelid);
Type of sebaceous gland (holocrine secretion)
