Lecture 40 4/23/24 Flashcards
What is integument?
something that covers; especially an enveloping layer such as skin/membrane/cuticle
What are the functions of skin?
-protection
-situational awareness
-temp. regulation
-secretion/excretion
-metabolic
What are the components of the skin?
-epidermis
-dermis
-adnexa
-subcutis
What are the characteristics of the epidermis?
-most superficial layer
-keratinized stratified squamous epithelium
-produces basement membrane
-sits on top of dermis
How does epidermis differ from epithelium?
epidermis is only used to refer to the epithelium of skin; epithelium is more of an umbrella term
What are the five layers of the epidermis?
-stratum corneum
-stratum lucidum
-stratum granulosum
-stratum spinosum
-stratum basale
What are the characteristics of the stratum corneum?
-cornified/keratinized cells
-dead, flattened, and eosinophilic
-can have nuclei in cells
-continually shed and replaced
-thickness varies by location and in response to injury and disease
What are the characteristics of the stratum lucidum?
-prominent only in the footpads
-may be seen in nasal planum
-located between stratum corneum and granulosum
What are the characteristics of the stratum granulosum?
-intracellular keratohyalin granules
-thickness varies by location
-absent in areas of “hard” keratin
-trichohyalin granules in the hair follicles
What are the characteristics of the stratum spinosum layer?
-spinous cell layer
-desmosomes hold adjacent cells together; causes prickly appearance
-often the thickest layer
What are the characteristics of the stratum basale?
-single layer of cuboidal cells attached to underlying basement membrane
-hemidesmosome attachment
-continually divide; supply cells for the other layers
Which non-epithelial cells ARE found in the epidermis?
-melanocytes
-Langerhans cells
-Merkel cells
Which non-epithelial cell structures are NOT found in the epidermis?
-blood vessels
-lymphatics
What are the characteristics of melanocytes?
-in the stratum basale
-produce and share melanin with adjacent keratinocytes
-melanin product protects against UV radiation
What are the characteristics of Langerhans cells?
-in the stratum basale and spinosum
-similar to macrophages
What are the characteristics of Merkel cells?
-clear cells found in the stratum basale
-function somewhat unknown
-thought to act as mechanoreceptors as well as regulate hair cycle
What are the characteristics of reptile scales?
-epidermal in origin
-overlapping projections of stratum corneum
-extensions of the epidermis
What are the characteristics of fish scales?
-dermal origin
-covered with epidermis
What are the characteristics of the epidermal-dermal junction?
-smooth in most locations
-epidermal rete pegs interdigitate with dermal papillae in high friction areas
What are the functions of the dermis?
-supports epidermis
-provides tensile strength
What are the components of the dermis?
-collagen, reticular, and elastic fibers
-ground/interstitial substance
-blood vessels
-lymphatics
-nerves
-mixed cells
What is adnexa?
“appendages” of an organ
What are the adnexa of the skin?
-hair follicles
-glands
What are the components of a hair follicle?
-hair shaft
-adventitial sheath
-outer root sheath
-inner root sheath
-matrix
-dermal papilla
What are the layers of the hair shaft, from out to in?
-cuticle
-cortex
-medulla
What are the segments of the hair follicle?
-infundibulum: granular layer w/ flaky keratin
-isthmus: glassy cells and homogenous keratin
-suprabulbar and bulbar: small dark cells
What are the characteristics of primary hair follicles?
-large diameter
-deeply rooted in dermis
-have sebaceous glands
-have apocrine glands
-have arrector pili muscle
What are the characteristics of secondary hair follicles?
-smaller diameter
-rooted more superficially
-may have a sebaceous gland
-lack apocrine glands
-lack arrector pili muscle
What is a simple follicle?
-individual follicles clearly separated by connective tissue
What are the two types of compound follicles?
-clustering of follicles within minimal intervening connective tissue
OR
-multiple hair shafts in a single follicular infundibulum
Which types of follicles are seen in different species?
simple:
-horses
-pigs
-cows
simple and compound:
-sheep (hair-growing vs. wool growing)
primary and secondary follicles:
-goats
primary simple and secondary compound:
-dogs
-cats
What are the steps of the hair cycle?
-anagen: growth phase
-catagen: transitional/involuting phase
-telogen: resting phase
Which sections of the hair follicle are lost during catagen and telogen, and which are permanent?
-deeper suprabulbar and bulbar, are lost
-infundibulum and isthmus are permanent
What are the characteristics of sinus hairs/whiskers?
-adventitial sheath is thickened by connective tissue trabeculae
-trabeculae are filled with blood
-well-innervated to provide sensation
What are the characteristics of arrector pili muscles?
-smooth muscle
-lifts the hair
-sympathetic innervation leads tocontraction when stressed, which causes elevated hairs
-traps heat and warns off predators
