normal skin structure and function Flashcards
stratum basale
single layer of cubiodal/columnar of young keratinocytes that sit on the basal lamina. Basal keratinocytes screte type vii collagen (component of anchoring fibrils which reinforces the basal lamina)
keratinocytes
what the epidermis is made of. lots of cystine histadine and lysine rich keratin for crosslinking. desmisomes connect cells together, hemidesmisomes connect cells to basal lamina
stratum spinosum
keratinocytes from the basal layer turn into prickle cells that have lots of desmisomes and tonofibrils (made of keratin) for reinforcment. vitamin d made here in response to UV light.
stratum granulosum
one or few cell layers thick. has flat cells with keratohyalin granules which contain profilaggrin. fillaggrin cross links/organizes keratin filaments. acts as a moisturizer. breakdown of fillaggrin leads to acidification of stratum corneum which provides resistance to pathogens. contain membrane bound vesicles called lamerllar bodies which has glycolipid that helps waterproof skin.
stratum corneum
cells have lost their organelles and are dead. crosslinked with keratin and attached via desmisomes.
melanocytes, cytocrine secretion
stellate cells that are the source of skin pigment. melanin is synthesized from tyrosine. granules with melanin migrate out of the melanocyte processes and are transferred to keratinocytes in a process called cytocrine secretion. the keratinocytes engulf melanocyte processes with the granules. so granules with pigment are produced in melanocytes but found in kerationcytes
albinism, vitiligo
albanism- defect in tyrosinase enzyme so no melanin pigment made
vitiligo- patchy areas of depigmentation –caused by localized death of melanocytes
langerhans cells
immune system cells from monocyte lineage. they are apc’s
merkel cell
present mostly in thick skin of palms and soles. they are bound to keratinocytes via desmisomes and are associated with free nerve endings in the epidermis– role in mechanoreception
what is the dermis composed of
compsoed of collagen and elastic fibers, CT cells like fibroblasts, mast cells, macrophages. blood supply and lymph vessels, nerves, sensory receptors, hair follicles, sweat glands, sebaceous glands
papillary layer
layer of dermis directly under the epidermis. it forms dermal papillae which are projections of the dermis into the epidermis. the opposite projections of epidermis into the dermis are called rete ridges. these increase surface area for ahesion and metabolic exhange.
reticular layer
thick reticular second layer of the dermis has coarser collagen bundles
skkin blood supply
subpapillary plexus- between the two dermal layers
cutaneous plexus - between reticular layer of dermis and the hyodermis
there are shunts. shunting blood into the subpapillary plexus loses heat
shunting blood to cutaneous plexus conserves heat.
sebacous glands
found in the dermis along hair follicle. secretory portion drains via a duct that goes to epidermis of upper layer of hair follicle. rapidly dividing basal cells push sebaceous cells through duct –secretion called sebum is mostly lipid and dead cells. sebum softens the skin and decreases water loss . responsive to sex hormones
eccrine sweat glands
in dermis or hypodermis. coiled tube of myoepithelial cells and secretory cells. fluid produced is isotonic w plasma. sweat is water nacl urea amminia and uric acid. thermoregulation and excretion fct.
thin skin glands good for heat stress. thick skin respond to emotional stimuli.
apocrine sweat glands
coiled tubular glands derived from epidermis. big lumens sectrory cells make proteinaceous material. ducts open to upper part of hair follicle rater than surface. found in azxilla, areola and curcumanal regions
Nails
The nail is a plate of hard keratin on top of stratified squamous epithelium called the nail bed. The nail bed supports the nail but
does not contribute to its growth. Rather the nail plate epithelium
arises from the nail matrix, located at the proximal end of the nail. The eponychium or cuticle is formed by a fold of the stratum
corneum.
The whitish crescent visible at the proximal end of the nail plate is
the lunula. It is the visible part of the nail matrix.
Keratinocytes of the nail bed do not contain melanin. Measuring the color of the nail bed is used to check oxygenation.
Koilonychia, clubbing, beaus lines, pitting, Periungual telangiectasia, Onychomycosis, thyroid disease, marfans syndrome
- Spooning of the nails Associated with iron deficiency
- Liver disease, carcinoma, ulcerative colitis, cardiopulmndisease
- Lines that transverse the nail associated with disease.
- Pitting occurs in psoriasis
- Dilated capillaries near the entail fold. Suggests ct disease
- Not to be confused with onycholysis which is separation from nail and bed this is a fungal infection that disfigures but is asymptotic.
- Splitting from nail form bed common in thyroid disease
- Marfans results in long narrow nails.
Hair connective tissues sheath
Connective tissue sheath: The outermost layer of the follicle is a connective tissue sheath which surrounds the hair follicle; this
layer of connective tissue is invaginated into the base of the
follicle to form the connective tissue papilla, which supplies the cappilaries and Nerves. It is continuous with reticular layer of dermis.
Hair glassy membrane
Glassy membrane: The basal lamina of the hair follicle is very thick and is called the glassy memberane. It separates the
external root sheath from the dermis along the length of the hair shaft;
Hair external root sheath
External root sheath: The external root sheath is continuous
with the epidermis, and has the same structure as the epidermis along the length of the hair shaft; at the base of the follicle, the
external root sheath merges with the internal root sheath in a
cellular mass called the matrix.
Hair shaft.
Hair shaft: The hair is produced by epithelial cells above the
dermal papilla, from which they are separated by a basal lamina.
Melanocytes among these cells give pigment to the hair. As in the epidermis, a single layer of actively dividing cells supplies
overlying layers. These cells synthesize large amounts of keratin,
and undergo a process of programmed cell death yielding scales
which fuse to make up the hair. The hair has 3 layers:
• the central medulla (soft keratin; medulla often absent).
• the cortex (hard keratin), which makes up the bulk of the hair. • an outer cuticle formed by a layer of partially overlapping,
shingle-like cells.
Hair bulge
Hair bulge region: A population of cells in the outer root sheath at the insertion point of the arrector pili muscle serves as stem cells for regenerating the follicle as it is periodically shed and re-grown during the normal hair life cycle. These cells also provide stem
cells for regeneration of the epidermis after wounding
Hair loss
Telogen Effluvium occurs when too many follicles shift into
telogen. This is the cause of postpartum hair loss and can
also be triggered by illness.
Anagen Effluvium is hair loss due to chemotherapy
damage to proliferating follicular epithelium.
Other common hair loss conditions include:
Androgenetic Alopecia - male and female pattern hair loss
–is triggered by androgens in the genetically susceptible.
Alopecia areata is a autoimmune disease that appears to target several antigens and causes loss of hair
follicles. It can
show a remitting relapsing pattern and hair can regrow in
denuded areas, although hair loss may be permanent. It can occur at any age and has a familial component.
