Integument Flashcards
hypodermis/subcutis
loose CCT & white fat binding dermis to underlying tissue (superficial fascia)
NOT part of skin
Basic Skin Structure
out to in
- epidermis
- dermis
- hypodermis/subcutis
- accessory structures (adnexa)
Adnexa
hair, hair follicles, glands, arrector pili mm.
Skin made of
epidermis and dermis
layers of epidermis
Stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum
What layers of epidermis have mitotic activity?
stratum basal and stratum spinosum
Where is keratin located?
stratum corneum
Another name for stratum basale
stratum germinativum
Stratum Basale Characteristics
- single layer of cells!
- established dermal-epidermal boundary
Stratum Spinosum Characteristics
- THICKEST layer of epidermis
- cells are alive & divide to limited extend in deeper regions
- spiny appearance between cells
keratinocytes
cells that begin to accumulate keratin
What causes the spiny appearance of cells in Stratum Spinosum?
desmosomes attaching “intercellular bridges”
Stratum Granulosum Characteristics
- 3rd layer of epidermis
- outermost cells are dying in this layer
Stratum Granulosum cells contain
aggregated keratohyaline granules
Keratohyaline granules
granular material seen in cells before fully formed keratin is present
Stratum Lucidum Characteristics
- “optional” epidermal layer
- present in thick skin not thin
- present in places of heavy wear (aka foot pads)
- not in skin with hair follicles
- clear band above stratum granulosum
Stratum Lucidum cells contain
eleidin
and are dying
Eleidin
fibrous protein (intermediate form of keratin) in cells of stratum lucidum
Stratum Corneum Characteristics
- mature keratin
- dead cell layer at surface
Stratum Corneum cells
- flat, without nuclei
- outermost part continuously sloughs off
Melanocytes
make melanin
Melanocyte location
stratum basale
melanin
responsible for skin color
melanin location
cells of stratum basale and lower spinosum
-gets injected into these cells
What forms melanin?
Tyrosine
Melanin’s Job
protect from UV radiation
Melanocytes H&E
dark granules, unstained cytoplasm,
Melanocyte Characteristics
-has cytoplasmic extensions that go b/n cells of stratum basale & stratum spinosum
Langerhans Cell location
stratum spinosum with processes extending between keratinocytes
Merkel’s cell Location
Stratum Basale, parallel to epidermal surface
Merkel’s cell assumed function
sensory input as mechanoreceptors for ‘light’ touch or may have broader role
Function of Rete pegs (epidermal ridges/epidermal pegs)
provide stability
Dermis layers
Papillary layer, Reticular layer, Blood Vessels, Nerves, Receptors
Papillary layer of dermis
- interdigitates with rete peges
- provides structural support & increased surface area
Dermal Receptors
Pacinian Corpuscles
Meissner’s Corpuscles
Pacinian Corpuscle recieves
pressure signals.
Pacinian Corpuscle location
deeper in dermis
Meissner’s Corpuscle receives
touch feelings
Meissner’s corpuscle location
dermal papillae
Adnexa
hair & hair follicles, arrector pilli mm., sebaceous glands, sweat glands
Hair follicle
invaginations of epidermal epithelium
hair bulb
terminal dilation of hair follicle
Base of Hair bulb contains
dermal papillae which are covered by epithelial cells, have a capillary & nerve network, responsible for sustaining hair follicle
Hair
thin strands of hard, compact keratin
Layers of Hair
Medulla - less dense center
Cortex - more dense middle
Cuticle - thin outer layer
Root of hair
epidermal cells covering dermal papilla
Compound hair follicle
- more than one hair emerges from a follicle
- contains 1 large main guard hair & many smaller “wool” hairs
Function of Guard Hair in compound hair follicles
waterproof top layer
Function of wool hairs in compound hair follicles
insulation barrier against the skin
Arrector Pili Muscle
- smooth muscle
- attaches at base of hair follicle
- function = contraction in response to stimulus (hair standing on end)
Sebacous glands
- masses of rounded cells with prominent round nuclei
- only in haired areas
Sebacous gland mode and type of secretion
holocrine & sebum
Holocrine secretion
entire cell ruptures to release contents
Sebacous gland functions
- antibacterial
- waterproofing agent
Sweat glands
simple coiled tubular glands lines with simple cuboidal epithelium
How do sweat glands move secretions?
with myoepithelial cells
Apocrine sweat glands
- duct opens into hair follicle
- most common in domestic animals
- slighly viscous secretion
Apocrine Sweat Gland function
scent and thermoregulation
Merocrine sweat glands
- located in special areas (foot pads)
- duct opens directly onto skin
Anal Sacs
- diverticula within skin of anal region
- keratinized stratified squamous epithelium
- contain glands
Dog Anal Sacs
- apocrine sweat glands only
- frequently impact
Cat Anal Sacs
- apocrine sweat glands & sebacous glands
- unlikely to impact
Circumanal (Perianal) Glands
- modified sebacous glands
- in dogs
- HIGHLY acidophilic cytoplasm; large, round nuclei
- tend to become neoplastic
Supracaudal (Preen) Glands
- collection of large, sebacous glands
- overproduction => “stud tail”
- in carnivores
Sinus (Tactile) Hair Location
mostly on face
Sinus/Tactile Hair
- large hair follicles with blood-filled sinuses
- Trabeculae (CCT) traverse the sinus (lower part in carnivores. everywhere in horses/ruminants)
- nerve ending network within trabeculae
Sinus/Tactile Hair Function
touch & orientation in environment
Functional significance for interdigitation of epidermis and dermis
- increased nutrient diffusion to epithelial cells (from dermis to epidermis)
- increased surface area to facilitate attachment of epidermis to dermis
