Lecture 1 Flashcards
Types of sweat glands
Apocrine, Eccrine
Sweating
cholinergic response (regulated by certain neurotransmitters)
Evaporation of sweat
causes goose bumps due to stimulation of contraction of the arrector pill muscle seen on the diagram
Apocrine gland
associated with the hair follicles found in armpits, perineal region, and external ear canal.
Apocine secretions
milky white and odorless. Upon exposure to cutaneous bacteria, it produces a pungent odor
Sebaceous Gland
appendaged to the hair follicle: produces an oily substance called sebum whose function is unknown perhaps water repellancy?
Sebum
contains liquid and solid phase, if out of balance it may contribute to acne
Nail Plate
approximately 0.5mm-1.3mm thick. Includes dorsal nail plate, intermediate nail plate, adn ventral nail plate
Nail Bed
Non cornified soft tissue underneath the nail plate, heavily vascularized. Extends from the lunlula to the hyponychium
Nail Matrix
A thick layer of highly proliferative epithelial tissue responsible for nail plate. Lower cell layers contains melanocytes which likely confer the pigmentation to the nail plate. This layer is heavily vascularized.
Nails
modified epidermis, contain 25 cell layers of flattened, dead keratinized cells fused into a hard slightly elastic plate. High in disulfide linkages
Onychomycisis
nail fungal infections
Onycholysis
nail loss
Nail Psoriasis
pitting and white spots
Infected eponychium
hang nail
Dermal-epidermal junction
separates dermis from epidermis
Dermis
separated into papillary dermis and reticular dermis
Types of collagen in dermis
Type I - in reticular layer
Type III - in papillary layer
Living cells
keratinocytes
Dead cells
corneocytes
epidermis
divided into 5 layers to be discuss next. main function is to replenish the stratum corneum
Layers of epidermis
Basal, prickle, granular, clear, horny
Melanocytes
large round cell with finger like projections called dendrites that reach out to keratinocytes. Found in basal layer. Produce dark pigment granules containing melanin which can be released into the keratinocyte where it clusters around the nucleus .
Factors that influence color of skin
melanocytes, hemoglobin, and carotenes
Langerhans cells
important for immunological reactions, can be found in other organs, and found mostly in prickle layer
Merkel cells
in basal layer of epidermis, and connect to epithelial cells. involved in signaling to neuritt. Play active role in mechanotransduction.
Length of time for keratinoytes to go from dermis to epidermis
28 days, takes 14 to go through stratum corneum
How cells in basal layer are connected
Desmosomes. Match on each cell, connect via fibrils
Basal Layer
contains keratinocytes that are actively dividing. Has capacity for DNA synthesis. Contain K5 and K14 keratins
Spinous Layer/Prickle Layer
Keratinocytes begin process of differentiation - a process of regulated cell death and is controlled transcriptionally. K1 and K4 keratin is here. Produce loricrin
Loricrin
Protein that becomes part of the cornified envelope.
Prickle cell
named because of shape and filaments
Granular Layer
Where final tailoring of protein synthesis occurs, and where the last stage of metabolic activity occurs. Has typical cells but apoptosis occurs.
Fillagrin
the stacking protein that helps stack the keratin filament
Stratum Lucidum/Clear Layer
Visible only in thickest skin, thin layer of translucent flattened cells, the cells have no nuclei (almost dead), their cytoplasm is filled with filaments
Horney Layer/Stratum Corneum
Contains corneocytes. Uppermost layer, thickest on palms/soles (glabrous skin). Only contain proteins and lipids, and K1/K10 filaments
Corneocytes
flat squames surrounded by multilamellar lipid layers; there are 15-20 layers of these in the S.C.
Epidermal Proteins - Keratins
comprise 30% of the dry weight of visible epidermal cells and about 80% of the dry weight of S.C. Form coiled coil structure
Filaggrin
Histidine rich protein, plays role in aggregating the keratin filaments in the stratum corneum. Made in the cell as a very large precursor molecule that consist of many chains joined by linker regions.
Involucrin
A highly reactive, soluble, transglutaminase substrate protein present in keratinocytes. Helps in the formation of an insoluble envelope beneath the plasma membrane. It provides structural support to the cell, and resists invasion by micro-organism
Cornified Cell Envelope
Forms around corneocyte. Provides structure and protection of the corneocyte. Comprimised of epidermal proteins - tranasglutaminase, lorigin, and involucin. Surrounded by covalently bonded lipid layer - ceramide and fatty acid.
Key regulatory mechanisms of keratinocyte proliferation and differentiation
Nuclear hormone receptors, calcium second messenger signaling, immunomodulatory regulation, cytokines and growth factors.
Calcium second messenger signaling
Keratinocytes grown in low calcium proliferate, grown in high calcium differentiate. There is a calcium gradient in epidermis, low in the basal proliferating layer and higher in the superficial layers.
Inflammatory cytokines
Disruption of barrier with irritants like surfactants elicit production of two specific cytokines in the first phase. Act by binding to specific receptors in the cell membrane.
Immunomodulary Cytokine action in skin
Antigen presenting cell binds to the T cell in skin. T cell interacting with antigen is either Th-1 or Th-2 depending on the disease/irritant mechanism. Th cells release cytokines associated with the disease state that act on mast cells or recruit appropriate white blood cells.
