lect 26 & 27 (T3): integument Flashcards
what does the dermis of the skin correspond to
lamina propria of a mucous membrane
what are characteristics of the primary dermal ridge
related to finger prints
found everywhere except forehead, external ear, perineum, and scrotum
formed during 3rd to 4th months of fetal life
subdivided into 2 secondary dermal ridges by inter papillary peg
what is the inter papillary peg
downward growth of epidermis along crest
what are characteristics of the secondary dermal ridge
occur in double rows, branched
thin, collagenous, reticular and elastic fibers
what is the dermal papillae
upward projections from each secondary dermal ridge
what are characteristics of thick skin
occurs only on palms and soles and is hairless
displays all 5 epidermal layers
what are characteristics of thin skin
occurs over rest of body thinnest in eyelids thickest on back thicker on extensor surfaces than flexor epidermal layers less distinct and lacking stratum lucidum
what are the layers of the epidermis
stratum basale (deepest) stratum spinosum stratum granulosum (represented by only a few cells in thin skin) stratum lucidum (absent in thin skin) stratum corenum (most superficial)
what types of cells are in the stratum basale
single layer cells held together by desmosomes (hemidesmosomes hold layer to basal lamina)
what does mitotic activity in the stratum basal produce
stem cells differentiating keratinocytes
what type of cells are in the stratum spinosum
polyhedral shaped cells (prickle cells)
what keratins are in stratum spinosum
keratins 1 and 10 (high molecule weight)
what keratins are in stratum basale
keratins 5 and 14 (low molecular weight0
what do the lamellar bodies in stratum spinosum contain
lipid, carbs, and hydrolytic enzymes
what do tonofibrils do
form intercellular bridges
what are characteristics of stratum granulosum
multilayerd keratins 2e and 9 flattened nucleated keratinocytes keratohylain aggregates membrane-coating granules (lamellar bodies) tonofilaments
keratokyalin aggregates do what
filagrin induces cross-linkage of keratin filaments by disulfide bonds
no limiting membrane
what are characteristic lucidum
flat keratinocytes lacking nuclei and organelles
only found in thick skin
contains eleiden
what are characteristics of stratum corneum
multilayered
thicker in thick skin
enucleated, flattened, dead keratinocytes
cytoplasm replaced by keratin
cytoplasm contains: keratin cross-linked with filaggrin (cornified cell envelope)
what are the layers of the cornfield cell envelope
extracellular: muti-lamellar lipid layer covalently linked to involucrine
intracellular: involucrine, small proline-rich proteins, loricrin, fillagrin and keratin complex
what do tight junctions in the stratum granulosum contain
claudin-1 and claudin-4 (components of the permeability barrier)
what are dermis characteristics
dense fibrous irregular CT layer beneath epidermis
derived from embryonic mesoderm
induces development of epidermis and epidermal derivatives
supports epidermis
hypodermis characteristics
loose CT that underlies dermis
corresponds to superficial fascia of gross anatomy
technically not part of skin
may contain fat cells that can form a thick layer called the panniculus adiposus
what are the 2 layers of the dermi
papillary and reticular layer
why are characteristics of papillary layer of ddermis
loose CT
separated from epidermis by basal lamina
network of fine elastic fibers and abundant capillaries
what are characteristics of reticular layer of dermis
dense irregular CT
includes fibrocytes, macrophages, and adipocytes
where do langerhans cells come from
monocytes
where do langerhans cells migrate from and to
migrate from epidermis to lymph nodes
where are merkel cells usually located
stratum germinativum
what does the periderm slough off to form
vernix caseosa
what does the inner cuboidal germinal layer of the epidermis proliferate to form
adult layers of the epidermis and derivatives
what is the dermis derived from
mesoderm
what are characteristics of sebaceous glands
holocrine glands
branched acinar glands with short ducts
found everywhere except palms and soles
continuously produce sebum (release into hair follicle)
growth is stimulated at puberty by sex hormones
what are characteristics of sweat (sudoriferous glands)
both merocrine and apocrine glands
what are characteristics of merocrine glands
coiled, simple tubular secretory portions lined by simple epithelium
apical dark secretory cells secrete glycoproteins
basal clear cells secrete water and electrolytes
myoepithelial cells
duct system
cholinergic endings
what does the duct system of merocrine glands consist of
stratified cuboidal epithelium except in epidermis
where are apocrine glands found
labia majora, areola, and axillary and anal regions
where do the excretory duct open into for apocrine glands
hair follicle
when do apocrine glands become active
puberty
what are the special types of sweat (sudoriferous) glands
ceruminous glands
glands of moll
how do apical dark cells secrete glycoproteins
by exocytosis (merocrine secretion)
what are the components of a hair follicle
root, free shaft, hair follicle
what are characteristics of a hair bulb
expanded lower part of hair follicle
matrix
vascularized dermal papilla
what is the external root sheath of hair follicle
down growth of epidermis
what is the internal root sheath of the hair follicle generated by
bulb matrix
what are the layers of the internal root sheath of hair follicle
Henle’s layer
huxley’s layer
cuticle (interlocks with cuticle of hair shaft)
what are the layers of the hair shaft
medula (innermost)
cortex
cuticle
where do the edges of the cuticle of the hair shaft tend to point
downward
