Lec 12 - Integument Flashcards
functions of the integument
- protection from abrasion
- excretion of salts, water, & organic wastes
- temperature regulation
- storage of lipids
- production of melanin & keratin
- synthesis of Vitamin D 3
- sensory reception of stimuli related to touch, pressure, pain, temperature
layers of the integument and features
epidermis:
* stratified squamous keratinized epithelium
* keratinocytes, melanocytes,
Langerhan’s cells; sensory organs & nerve endings
dermis:
* papillary layer- loose irregular CT
* reticular layer-dense irregular CT
* hair follicles, glands, smooth muscle, blood vessels
hypodermis (subcutis): (subcutaneous fascia)
* unilocular (white) adipose tissue
* loose irregular CT
features of thick vs thin skin
- “thick” skin
- epidermis > 5 mm
- hairless: e.g. nasal
plenum & foot pads - “thin” skin
- epidermis ~ 1mm
- haired skin:
general body
epidermis layers
stratum corneum: multiple layers, anuclear zone, flattened cellular remnants shed from surface (st. lucidum)
stratum granulosum: multiple layers of elongated cells with nuclear degradation & basophilic granules
stratum spinosum: multiple layers of
irregularly shaped cells with spiny processes bridging extracellular space
stratum basale: (st. germinativum): single layer of small, cuboidal basophilic cells; may see mitotic figures
components of each epidermis layer
- Stratum Basale:
* stem cells for epidermis; constant proliferation renews epithelial layer
* some tonofilaments (keratin
intermediate filaments)
* hemidesmosomes & focal adhesions to adhere to basal lamina
* some desomsomes - Stratum Spinosum: (prickle cell layer)
* production of tonofilaments (keratin IF) & desmosomes
* upper layers produce lamellar bodies (lipid) & IF-associated proteins - Stratum Granulosum:
* synthesize lamellar bodies (lipid) & keratohyaline vesicles (basophilic granules)
* exocytose lamellar bodies
* undergo apoptosis - Stratum Corneum:
* dead (apoptotic) cells filled with granule contents & tonofilaments
* thickened plasma membrane & lipid seal
* surface ‘cells’ exfoliate.
what layer do you see in thick hairless skin
stratum lucidum
stratum spinosum - what is prominent, purpose
- desmosomes especially prominent in this region of epidermis
- strong cell-cell adhesion resists abrasion
melanocytes - where are they found, what do they look like, function
melanocytes:
* neural crest derived cells
* make pigment & “donate” it to
keratinocytes; forms cap over nucleus
* melanocyte cell bodies usually found in basal layer of epidermis; processes project deeper into epidermis
tyrosine conversion, what happens when there is an issue, what factors affect coat colour
tyrosine (converted by tyrosinase) –> DOPA –> melanin (eumelanin, pheomelanin)
issues with tyrosinase = albinism
Factors affecting coat“colour”:
* type and amount of melanin produced by melanocytes
* arrangement of melanin in hair matrix
* underlying skin pigmentation
* distribution of melanocytes in integument
langerhans cells - what are they part of, involved in what
- part of mononuclear/macrophage
phagocytic system (dendritic cell) - process antigens taken up by skin,
then travels to regional lymph nodes - involved in hypersensitivity
reactions: e.g. contact allergic dermatitis
what increases surface area in the dermis
epidermal ridges and dermal papillae
- dermis of loose and dense irregular CT
- loose region organized as finger like papillae intersection with epidermal ridges: increased surface area
epidermal derivatives ofthe skin
what is incuded in the pilosebaceous unit
role in thermoregulation
“dermal appendages” or adnexa of the integument
* hair follicles
* sweat glands: apocrine & eccrine
* sebaceous glands
“pilosebaceous unit”
* hair and hair follicle
* sebaceous gland
* apocrine sweat gland
* arrector pili muscle
role in thermoregulation:
* boundary zone
* evaporative cooling
* waterproofing
parts of the hair, and what makes it up
Hair Shaft: made of hard keratin
* outer cuticle
* inner medulla
* middle cortex
Root/Root Sheath:
* matrix cells split into inner and outer root sheath
* outer root sheath continuous with epidermis
Hair Bulb:
* growing region of hair: stem cells
* matrix cells generate keratin
* melanocytes
Hair Papilla:
* connective tissue invagination into follicle bulb
* inductive activity
piloerection - what happens, function
- arrector pili is bundle of smooth muscle connecting hair follicle to base of epidermis
- contraction leads to rotation of follicle causing hair to stand upright
- raised hair traps boundary layer of air: thermoregulation
- also involved in aggression & fear displays
whats another name for whiskers, what are they specialized for, composition
- specialized for tactile sense
- typical structures of a primary hair follicle with large guard hair
- follicle surrounded by ring sinus (blood filled space) with dense CT capsule
- sensory nerves sometimes seen (note: all hairs have nerve input at papilla)
hair growth cycle, what determines hair length, what phase is prolonged in some hairs
Anagen (Growth)
* nourishment via blood supply in papilla; hair matrix cell division & hair growth
Catagen (Transition)
* cell division & hair growth cease; follicle shrinks
Telogen (Resting)
* hair not anchored & falls out
(shedding)
* new hair starts growing in papilla; initiates renewed anagen phase
-time spent in anagen determines hair length
* some hairs (e.g. eyelashes) have prolonged telogen phase
eccrine sweat glands; epithelium, function, type of secretion, where are they found
- simple coiled tubular gland
- stratified cuboidal epithelium; duct cells much smaller
- watery sweat for evaporative cooling
- some Na + reabsorbed but sweat contains NaCl & other ions; N waste (e.g. urea & ammonia); low in protein merocrine secretion
- found in hairless skin; uncommon in veterinary species
apocrine sweat galnds; epithelium, function, type of secretion, where are they found
- simple coiled tubular
- secretory portion simple cuboidal/columnar epithelium; surface blebbing: apocrine secretion
- wide lumen; myoepithelial cells
- duct cells stratified cuboidal; narrow lumen
- product is protein, carbohydrate, ions, lipids, N waste, etc.
- “haired” skin
- part of pilosebaceous unit; duct empties into hair follicle
sebaceous gland; epithelium, function, type of secretion, where are they found
- simple branched acinar
- basal cells are mitotic; secretory cells undergo apoptosis (holocrine secretion)
- duct cells stratified cuboidal
- secretory cells pale, full of lipid droplets
- secretion is sebum: oily substance produced by holocrine mode
- bacteriostatic, emollient, barrier, pheromone functions?
- found mostly in haired skin
- part of pilosebaceous unit; duct empties directly into hair follicle
- usually several per hair follicle
hypodermis (subcutis); function, why is there extensive adipose tissue
- technically not part of the skin; anchors dermis to underlying muscle or bone
- extensive adipose tissue:
- ‘fat pads’ serve as shock absorbers & inhibit freezing injury
- footpad fat has a lower freezing point than many other tissues
- subcutaneous fat (‘blubber’) provides thermal insulation
mammary gland - type of gland, made up of, what is elaborate in it, what does it produce
- compound acinar gland
- made up of multiple lobes, separated by CT
- each lobe composed of numerous alveoli (acini)
- elaborate duct system drains milk into storage region (cistern); eventually released via canals in teat (species differences)
- produces milk via apocrine & merocrine modes of secretion
