Integument Flashcards
What is the specific name for the cell making up the epidermis?
Keratinocytes
Which cells of the epidermis are mitotic?
basal cells
What type of connection holds all of the layers of the epidermis together?
hemidesmosones below and desmosomes above
What are the 4 layers of the epidermis?
-Stratum corneum
-Stratum granulosum
-Stratum spinosum
-Stratum basale
What is the function of melanocytes and merkel cells?
make melanin
What factor affects the thickness of stratum spinosum?
The level of protection needed
What is the prominent layer in thick epithelium such as pads of feet and nares?
Stratum spinosum
What is the name of the strongly basophilic granules in the stratum granulosum?
keratohyalin granules
What layer undergoes apoptosis?
stratum granulosum
What is the role of keratohyalin granules?
They contain precursors of profilaggrin (which bundles keratin)
What is the major permeability barrier of skin?
Stratum corneum
What is the cell name after keratinocyte differenciation?
Corneocytes
What is the hallmark of stratum corneum?
keratinized stratified squamous epithelium
What are the 3 components of cornification?
-Keratin fibers
-Cornified envelope
-Extracellular lipids
What protein aggregates keratin filaments (tonofilaments)?
Filaggrin
What does keratin filament aggregation promote?
The collapse of the cell into a flattened shape, which is characteristic of corneocytes in the cornifed layer
What is the first step in forming the cornified envelope?
The rise in intracellular Ca2+ triggers the formation of a protein scaffold along the inner surface of plasma membrane
What is the role of lamellar bodies?
They fuse with the plasma membrane, releasing ceramids with long fatty acids which are incorporated into the plasma membrane which creates the lipid layer of the cornified envelope
What step is unique to fully keratinized (cornified) cells?
The formation of the lipid layer after fusion of lamellar bodies
What is another function of lamellar bodies that is not the formation of the cornified envelope lipid layer?
They create the intercellular lipid lamellae
How do lamellar bodies promote shedding (desquamation)?
They contain and subsequently release proteases that break down desmosomal proteins as well as lipases that digest the lipid components
List 4 ways in which the skin acts as an antimicrobial barrier?
-Desquamation
-Dry surface with low pH
-Antimicrobial proteins produced by keratinocytes
-Mast cells, lymphocytes in dermis
What is the function of a langerhan cell?
Part of immunologic barrier. a dendritic antigen presenting cell
Where are melanocytes located?
epidermis
Why are melanocytes hard to see?
They transfer the melanin to adjacent keratinocyte cytoplasm
What causes vitiligo?
Immune mediated destruction of melanocytes
Is there direct blood flow to the epidermis?
no
How do nutrients get to the epidermis?
They diffuse from vessels in the dermis
How are nerves supplied to the dermis?
-free nerve endings
- Merkel cells in basal layer are mechanoreceptors
What sensory receptors are located in the deep dermis and hypodermis, and respond to vibration and pressure?
Pacinican corpuscle
What are the two classifications of hair?
simple and compound
What are the three basic components of a compound hair?
a large guard hair, smaller wool hairs, and a shared auxillary glads (sweat glands)
What is the “hair shaft exit” called?
infudibulum
What two major species have compound hairs?
feline and canine
How are hair follicles oriented?
Obliquely in dermis or subcutis towards tail
How are hair follicles connected to the dermis?
Arrector pili muscle (smooth muscle) inserts on CT sheath of follicle and originates from superficial layer of dermis
Describe the structure of hair
Hair shaft, follicle which includes the hair bulb (matrix cells-germative layer and dermal papilla-vascularized loose CT
What are the layers of a hair follicle?
Connective tissue sheath, external root sheath, internal root sheath
Where are hair shaft medulla layers found? In what type of hair?
The inner most part of wooly/primary hair
What are the two phases of the hair cycle?
-Anagen: mitotically active
-Telogen: not mitotically active and will shed
What is the hallmark of a telogen hair?
dermal papilla regression
Define sebaceous gland
Simple branched alveolar gland associated with primary hair follicles which secrete discharge into duct then into hair shaft
What is sebaceous gland secretion stimulated by? inhibited?
Stimulated by testosterone and androgens
Inhibited by corticosteroids
What is the function of circumanal glands?
Modified sebaceous gland used for pheromone production
Where can you find circumanal glands?
Around the anus, tail base, groin area
What are the two types of sweat glands?
-Aprocrine
-Eccrine
What type of sweat gland is most common in domestic species?
Aprocrine
What are the major functions of apocrine sweat glands?
In dogs and cats: produce body odor. In cattle and horses produce perspiration
What species uses apocrine sweat glands for thermoregulation?
Horses and kinda cattle
Describe the epithelium of apocrine glands of anal sac
cornified, stratified squamous
What are the three layers of the hoof epidermis?
Stratum externum
Stratum medium
Stratum internum
What is the wall of the hoof made of?
Tubular horn surrounded by intertubular horn
