Studied by 2 people
simplest encapsulated receptor
Ruffini corpuscules
epidermal ridge corresponds to an underlying
dermal papilla
Epidermis
made of keratinized stratified squamous epithelium
Dermis
dense irregular, highly vascularized connective tissue and containing numerous sensory receptors
stratum of Malpighi of epidermis - made of
stratum basale (germinativum) + stratum spinosum
four populations of cells of epidermis
keratinocytes, langherhans cells, melanocytes, merkel cells
Stratum basale of epidermis
single layer of small columnar or cuboidal keratinocytes, has int filaments and desmosomes, stem cell mitotic activity here
Cells are bound to each other in epidermis through
desmosomes
hemidesmosomes connect
epidermal cells to BM
stratum spinosum of epidermis
thickest layer of epidermis with keratinocytes, many int filaments and membrane-coating granules, upward migration of keratinocytes
cytokeratin
fibrillar protein of int filaments, specific to epithelial cells
tonofilaments
cytokeratin bundle groups, many in stratum spinosum of epidermis
spines of stratum spinosum of epidermis
small cytoplasmic processes @ lat membranes of cells, where keratinocytes are attached by many desmosomes
stratum granulosum of epidermis
several layers of keratinocytes (larger), has keratohyaline granules and keratinosomes, cornified cells made
keratohialine granules
composed of filaggrin (nonintermediate protein filament) → induces aggregation of keratins → with formation of coarse keratohyalin granules
Keratinosome
have hydrophobic glycophospholipidic complex
stratum corneum of epidermis
thickest, cells filled with keratin, hard cells will slough off
keratinization of stratum corneum of epidermis
process of evolution, from the basal cell, to the superficial, cornified cell, which is shedding off/sloughed off
stratum lucidum of epidermis
only in thick skin, advanced keratinization process, cells contain densely packed keratin filaments and eleidin
Epidermal growth factor (EGF) and interleukin (IL-1α)
influence the growth and development of keratinocytes
Transforming growth factor (TGF)
suppresses keratinocyte proliferation and differentiation
epidermal permeability barrier
outer multilamellar lipid layer (cross-linked to involucrin) cornified cell envelope of 3 proteins + keratin-filaggrin komplex tight junctions between cells of the stratum granulosum (claudin)
Cells that are always present in the epithelium
Melanocytes, Langerhans cells, Merkel cells
melanocytes
produce melanin (melanofilaments), first stored in premelanosome of golgi, matures to melanosome by oxidation of tyrosine to DOPA by tyrosinase, go into keratinocytes
melanoblasts
melanocyte precursor, migrating from the neural crest into the basal layer of the epidermis
Langerhans cells (dendritic cells)
red bone marrow-derived cells, mainly in stratum spinosum, in the epidermis as immunologic sentinels, involved in immune responses, use proteins langerin and CDa1 (Birbeck granules)
Process of langerhans cells
phagocytoses the antigen, presents it to a neighboring T cell or enters a lymphatic vessel, migrates to lymph node, reenter the blood circulation, reach site of epidermal antigen and release proinflammatory cytokines to neutralize the antigen
merkel cells
modified epithelial cells, found in the stratum basale, mechanoreceptors (linked to keratinocytes by desmosomes and with intermediate filaments), many in fingertips, around free nerve endings
_________ ________- contains also neuroendocrine vesicles (VIP, P substance) - thus being part also of the DES
merkel cell
Dermis - contains
fibrocytes, fibroblasts and extracellular matrix, blood and lymph vessels, small number of macrophages, lymphocytes and mast cells
Papillary layer of dermis
superficial, has dermal-epidermal junction through papillae, loose connective tissue provides mechanical anchorage and nutrients to epidermis, contains more ground substance
fine nerve fibers in papillary layer of dermis
Meissner corpuscles (tactile stimulation), Krause end bulbs (respond to cold)
reticular layer of dermis
thick bundles of collagen fibers and coarse elastic fibers, sweat glands ducts, hair follicles and muscles, sebaceous glands
Epidermal-dermal junction/interface - ensures
the anchoring of the two layers, one to each other and their separation through the BM
the connection between the epidermis and the dermis is achieved by
hemidesmosomes
cell adhesion molecules
type VII collagen anchoring fibers
Epidermal-dermal junction in protected vs non protected areas
flat in protected, irregular in non protected with papillary crests
Hypodermis
superficial fascia of loose connective tissue and abundant adipose tissue and smooth + striated muscle fibers
Hypodermis function
mobility of the skin adipose tissue contributes to thermal insulation, storage of metabolic energy and shock absorber.
nutritive arteries of the skin are found
deep in the hypodermis
Profound subcutaneous plexus
at the epidermal-dermal interface n its branches provide blood supply for the adipose tissue in the hypodermis + dermis
superficial subpapillary plexus
under papillae of dermis, vascularization of superficial dermis + forms capillary loops
anastomotic arterio -venous shunts
in dermis, role in the thermoregulation, blood flow controlled by glomuses
Naked nerve endings
found in the epidermis, light pressure and touch stimuli
peritrichial nerve ending
around the base and shaft of the hair follicle, stimulated by the movement of the hair
Merkel disk
encapsulated receptor, discriminates touch, attached to the Merkel cell found in the stratum basale of the epidermis
Meissner corpuscle
in the dermal papillae of palms, feet, around the lips, mammary gland areola, tactile receptors, made of Schwann cells
Pacinian corpuscle
in the hypodermis, transient vibratory stimuli and is the receptor for deep pressure covered by connective tissue layer
Pilosebaceous unit
produce hair and sebum, a hydrophobic secretory product, which protects hair and accentuates hydrophobic characteristics of keratin
components of pilosebaceous unit
hair follicle (shaft + bulb), accompanied by sebaceous glands and arrector pili muscle
Arrector pili muscle
part of pilosebaceous unit, bundle of smooth muscle fibers, controlled by autonomic sympathetic nervous system
Sebaceous glands
holocrine simple saccular/alveolar glands, secrete lipids - sebum, everywhere except for the palms and soles, release into follicle or surface of skin
Sebaceous glands composed of
secretory portion (in dermis), sometimes excretory ducts (stratified squamous epithelium)
merocrine sweat glands
everywhere except lips and genitalia, simple tubulo-glomerular gland
secretory portion of merocrine sweat gland
lined by a pseudostratified epithelium with clear cells (secrete watery), dark cells (secrete proteins) and myoepithelial cells
excretory canalicular portion of merocrine sweat gland - contains
sweat duct and helical path (opens on its surface at a sweat pore)
heat-regulated vs emotional sweat
heat-regulated under cholinergic control, emotional under adrenergic control
Apocrine sweat glands
scent gland, coiled, tubulo-glomerular glands, merocrine
Moll's glands
apocrine sweat glands at eyelids
ceruminous glands
apocrine sweat glands at external auditory conduct, secrete cerumen
Sweat glands innervated by
sympathetic vegetative nervous system
