Integumentary System- Skin Flashcards
What are the functions of the integument and its associated functions?
-To act as a protective barrier
-Structural
-Metabolic – can metabolize drugs & chemicals as well as hepatocytes (epidermis)
-Immunologic/antimicrobial
-Photoprotective (against uv and radiation)
-Neurologic (touch, pain)- nerve endings
What are the secondary functions of the skin?
+/- Temperature and blood pressure control (sweat)
+/- Vitamin D production
-Pheromone production (through glands)
-Excretory function
-Sexual displays
What are the layers of the skin?
Epidermis – epithelium
*Keratinocytes
*Non-keratinocytes (melanocytes, dendritic cells)
Dermis – dense irregular connective tissue
Hypodermis (subcutis) – subcutaneous adipose tissue and fascia overlying muscle
**cutaneous is epidermis or close dermis
What are the layers of the epidermis?
-layers:
-statum basale
-stratum spinous
-stratum granulosum
-stratum corner
-as proliferation takes place from bottom layer, cells move up from their location:
*changing their morphology and function *with fully karatenized, essentially dead layers at the top.
where are Stratum basal located? and what are their characteristics?
Single layer of cuboidal cells resting on basement membrane
Hemidesmosomes attach them to basement membrane
Desmosomes attach cells to each other and overlying cells
-melanin is located here
What are stratum spinosum? and what are their characteristics
No longer mitotic
Larger cells with more cytoplasm
Produce keratin intermediate filaments which strengthens the cytoskeleton
Produce lamellar granules (a.k.a lamellar bodies)
Lipids
Hydrolytic enzymes and other proteins
Prominent layer in thicker epithelium: nares, pads of feet
what is stratum granulosum? and what are its characteristics?
- named for the basophilic keratohyalin granules
-MODIFIED APOPTOSIS
-Flattened cells lying parallel to surface
-Keratohyalin granules contain precursors of filaggrin protein (organize lamellar bodies)
-TIGHT JUNCTIONS (& desmosomes) between cells
-Upper layer undergoes modified apoptosis
*Loss of nuclei and organelles
What is cornification and stratum corneum?
Stratum corneum – major permeability barrier of skin
Corneocytes - end result of keratinocyte differentiation
No organelles
Stratum corneum is hallmark of keratinized (cornified) stratified squamous epithelium
what are the Components needed for cornification ?
Keratin fibers fill the cytoplasm (chocolate)
Cornified envelope (protein & lipid layers) (candy coating)
Extracellular lipids – lipid lamellae
what aggregates the keratin filaments (monofilaments)into tight bundles (tonofibrils) during cornification?
FILAGGRIN
This promotes the collapse of the cell into a flattened shape, which is characteristic of corneocytes in the cornified layer.
Corneocytes are so flat and thin that they readily fold over on themselves like a thin sheet of tissue paper
_________ constitute 80-90% of the protein mass of the epidermis
keratins and filaggrins
The _______ is a tough protein-lipid polymer structure formed JUST BELOW the cytoplasmic membrane
cornified cell envelope
What are the steps for creating a cornified cell envelope?
-First step: formation of PROTEIN SCAFFOLD along inner surface of PLASMA MEBRANE, including over desmosomes
-second step: Lamellar bodies fuse with plasma membrane releasing:
Ceramids lipids, with very long chain N-acyl fatty acids, are incorporated into the plasma membrane (lipid part of the envelop) and anchored to protein envelope (UNIQUE TO FULLY KARATEINZED cells)
-Third step:Ceramides in cornified envelope interdigitate with and organize the intercellular lipid lamellae
*The stratum corneum barrier is composed of corneocytes and intercellular lipids, cholesterol, free fatty acids
*The stratum corneum barrier is composed of corneocytes and intercellular lipids, cholesterol, free fatty acids
keratin to keratinization
layers:
ceramic lipids
cornfield envelope
Lamellar bodies also create intercellular lipid layers that creates a___________, AND THEY PROMOTE DESQUAMATION (shredding of corneocytes)
- water tight barrier. (cement/permeability barrier where cornification is taking place)
Lamellar bodies fuse with plasma membrane releasing :
*Free fatty aids and cholesterol released into extracellular space
*Ceramides in cornified envelope interdigitate with and organize the intercellular lipid lamellae
___________________________ are important for the mechanical stability of the corneocytes.
Keratins and cornified envelope proteins
what are the steps of epidermal programming?? and what happens in each?
refer to image
proliferation, differentiation, cornification, desquamation
proliferation takes 14 days= desquamation takes 14 days
what are released from lamellar bodies?
ceramid lipids, lipases, proteases, fatty acids and phospholipids
NOT KERATIN INTERMEDIATE FILAMENTS
Where can melanin (from melanocytes be found in the body?
-stratum basale
-hair follicele
-ducts of sweat and sebaceous gland
How does the skin work as an antimicrobial barrier?
Desquamation – shed cells with adherent bacteria
Dry surface with low pH
Antimicrobial proteins produced by keratinocytes
Mast cells, lymphocytes in DERMIS
Langerhans cells presence: (not fixed)
What is the epidermal/ dermal junction?
Rete ridges: areas of high shearing forces, where the epidermis will indent down
dermal Papillae: area where epidermis indents up
what is the Pacinian corpuscle ?
Located in deep dermis and hypodermis
Encapsulated mechanoreceptor
Respond to deep vibration and pressure
What is the structure of hair? (name each part)
Hair shaft – part of hair that sticks out of skin
Follicle - sac from which a hair grows and into which the sebaceous (oil) glands open.
Includes the hair bulb (in circle)
Matrix cells MITOTIC- germinative layer
Dark blue cuboidal cells overlying papilla
Dermal papilla
Vascularized loose connective tissue
sebaceous gland is at the top (not visible
External (outer) root sheath
Continuous with epidermis
Internal (inner) root sheath
What structures are seen in this image?
what structures are seen here?
seen in guard hair, usually angled towards the tails
smooth muscle near hair moves hair to response (ARRECTOR PILI MUSCLE)
What is the difference between simple and compound hair follicles?
More than one hair shaft arising FROM single follicle and OUT a single infundibulum (opening to skin)
three compound hairs in dog observed, nest to a guard hair
big on edge are guard hairs.
guard hair (biggest)
whole hair (small)
sebaceous gland seen on hair follicle
What are the phases of the hair cycle?
Anagen (mitotically active)
Categen (transition)
Telogen (not mitotically active)
what are sebaceous glands?
Foamy cytoplasm due to tiny vacuoles
Lipid-rich secretion (sebum)
Sebum functions
Lubricates hair and dermis
Acts as physical barrier
Contains antimicrobial products
Stimulated by androgens and testosterone
Suppressed by corticosteroids
what are Circumanal glands (a.k.a. perianal gland, hepatoid glands)?
Modified sebaceous glands
Abundant pink grainy cytoplasm
Central nucleus
Located around anus, tail base, groin area
Influenced by testosterone
Pheromone production
Give rise to relatively common benign tumors
What are sweat glands?
_Apocrine sweat glands
Predominant sweat gland in domestic species (except rodents)
Dogs and cats: major function is to produce body odors.
Horses and cattle (sorta): glands produce perspiration.
_Eccrine sweat glands
Widely distributed sweat glands in humans
Responsible for perspiration (thermoregulation)
Uncommon in domestic species (found in footpads, frog of horse hoof)
What is the function of apocrine gland?
Anal sacs: paired cutaneous diverticula with ducts that open into the anal canal
Anal sacs lined by cornified, stratified squamous epithelium
Sacs fill with sloughed squams and strong smelling aprocrine gland secretions
Empty during defecation
Important for marking territory, social cues
Relatively common malignant tumor
What are the parts of the hoof?
_Parts:
Hoof Wall
Periople
Sole
Frog
Coronary band (junction of hairline and hoof)
*Provides nutrition
*Growth comes from here
Periople (part of hoof wall)
Rubbery tissue above hoof wall, below haired skin (similar to cuticle)
what are the layers of the hoof?
What are the characteristics of the stratum externum?
What are the characteristics of stratum medium?
What do stratum medium look like under microscopes?
what is the stratum internum?
What does the stratum internal look like under the microscope?
what are the labeled parts?
E= secondary dermal laminae
SEL is the actual fingerlike structures
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