skin Flashcards
functions of the skin
- protective + waterproof
- regulates body temp
- sensory receptorz
epidermis
stratified squamous keratinized, ectoderm
- Specialized skin appendages: sweat + sebaceous glands, hair follicles
- Specialized cell types (melanocytes, merkel cells, langerhans cells)
- Mostly keratinocytes
dermis
dense irregular CT, mesoderm
- vascularized
- nerves
- receptors for temp, pain, touch (meissner’s corpuscles) in dermal ridges/papillae
- deep pressure (pacinian corpuscles)
- arrector pili
Meisner’s corpuscules
fine touch and pressure, in dermis
Pacinian corpuscules
deep pressure, dermis
Arrector pili
smooth muscles that attach at base of hair follicle
- anchor to dermis surrounding hair follicle
- goosebumps
Hypodermis
Beneath dermis, loose CT and adipose tissue
- connects skin to tissues + organs
Stratum basale
Innermost part of epidermis
- cuboidal-low columnar stem cells
- some desmosomes cell:cell
- many hemidesmosomes cell:basement
- attach epidermis to dermis
- maintain stem cell phenotype
- stem cells detach from basement membr and move up strata, begin to differentiate
- melanocytes + merkel cells
Stratum spinosum
differentiation to epithelial keratinocytes
- prod many keratin intermediate filaments (tonofilaments)
- many desmosomes cell:cell ends of keratinocyte/processes spines
- Langerhans cells
melanocytes
prod pigment, migrate into epidermis stratum basale
- derived from embryonic/fetal nervous system
merkel cells
mechano/touch receptors migrate into epidermis stratum basale
Langerhans cells
HSC-derived APCs, migrate into epidermis stratum spinosum
melanosome
melanocyte vesicles containing UV-absorbing melanin
- melanin prod by mod of tyrosine
- sent apically into stratum spinosum, phagocytosed by keratinocytes
stratum granulosum
cells fully diff, squamous
- Prod lipid-rich vesicles, exocytosed to generate waterproof barrier b/w granulosum and lucidum
- prod kerothyalin
keratohyalin
glycoprotein complex
- forms cytoplasmic granules (not membr-bound) in cells of s. granulosum
- cross-link tonofilaments
stratum lucidum, eleidin
Above waterproof barrier, fully diff cells
- prod eleidin, glycoprotein that aligns cross-linked tonofilaments parallel
- start to die and enucleate
stratum corneum
enucleated squamous cells, completely dead
- filled w/ protective cross-linked + bundled keratin filaments (squames)
- desmosomes deteriorate, squames slough off
hair follicles
invagination of epidermis, pushing down into dermis
- follicle terminates at epidermal hair root, indented by dermal papilla
- papilla: supply bv and nerves to hair root area
hair follicle - hair
cuticle, cortex, medulla (outside in)
hair follicle - internal root sheath
differentiating s. granulosum-like cells
- very orderly arranged cells
- cells move inward and die to prod. hair shaft
- henle’s layer, huxley’s layer, cuticle (outside in)
hair follicle - external root sheath
modified stratum basale and spinosum
sebaceous glands
outpouching of hair follicle epidermis (above hair bulb)
- ducts branch a lil and empty into hair canal
- alveolar secretory portion, prod lipid-rich sebum (pale H&E)
- secretion by necrosis - all contents released
- duct obstruction -> bacterial infection -> acne formation
eccrine sweat glands
coiled tubular glands, invaginations of epidermis
- mostly clear cells: secrete watery serous secretions, req secretion of Cl- via CFTR
- Interspersed dark cells: secrete sum glycoprotein- + proteoglycan-containing mucous
- contractile cells (epithelial, ectoderm) expel secretory products
- secretory portion deep, duct portion stratified cuboidal
