skin and breast
TRANSCRIPT
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INTEGUMENTARY
SYSTEMHISTOLOGY SECTION
CPU-College of Medicine
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INTEGUMENTARY SYSTEM
Skin (Cutis, integument) and its
derivatives
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Epithelial skin appendages
(Epidermal derivatives of the skin)
Hair follicles and hair
Sweat (sudoriferous) glands
Sebaceous glands Nails
Mammary glands
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Major (Major) Functions
Barriermechanical, permeability and ultravioletbarriers
Provides immunologic information
Homeostasisregulates body temperature and water
loss
Conveys sensory information to the nervous system
Performs endocrinesecretes hormones, cytokines
and growth factors; convert precursor molecules intohormonally active molecules (Vit. D)
Excretionsweat, sebaceous and apocrine glands
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SKIN
Heaviest single organ of the body (16%
TBW)
Adults: 1.22.3 m2of body surface
Epidermis (ectodermal) and dermis
(mesodermal)
Papillae (junction)Epidermal ridges (rete pegs, epidermal
pegs)
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Hypodermis/subcutaneous tissue
(panniculus adiposus)
- Binds skin loosely to the subjacent
tissues and corresponds to the superficial
(subcutaneous) fascia
External layer: Impermeable to water
Receptor organ/Protection from external
impact and friction
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Melanin - produced in epidermis
- Protection against UV rays
Glands of the skin, blood vessels and
adipose tissue: thermoregulation, body
metabolism, and the excretion of various
substancesVitamin D3: is formed under the action of
UV
Elasticity: cover large areas in conditionsassoc. w/ swelling (edema and pregnancy)
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Thick or Thin
Thick Skin
- palms and soles
- subject to the most abrasion
- hairless and with thicker epidermal layer
Thin Skin
- with thinner epidermis
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Ridges and grooves
Ridges: first appear during intrauterine life(@ 13 wks in the tips of the digits) and
later in the volar surfaces of the hands and
feet
Dermatoglyphics: patterns assumed by
ridges and intervening sulci (loops, arches,
whorls or combinations)
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Dermatoglyphic Pattern (Palms and
Soles excluding flexion creases)
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Whorl (35%)
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Arch (5%)
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Loop (65%)
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EPIDERMIS
Mainly stratified squamous keratinizedepithelium (keratinocytes)
Also w/ 3 less abundant cell types:
melanocytes, Langerhans cells, andMerkels cells
Thick skin (glabrous/smooth and nonhairy)
found on the palms and soles; 400 to 600m in thickness
Thin skin (hairy)75 to 150 m
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Thick Skin
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Thin Skin
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EPIDERMIS
Five layers of keratinocytes:
Stratum basale (Stratum germinativum)
Stratum spinosumStratum granulosum
Stratum lucidum
Stratum corneum
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Stratum basale
SINGLE layer of basophilic columnar orcuboidal cells resting on the basal lamina@ the dermal-epidermal junction
The axes are perpendicular to the basallamina
Desmosomes: bind them in the lateral andupper surfaces
Hemidesmosomes (in basalplasmalemma): bind the to the basallamina
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With intense mitotic activity: for renewal of
epidermal cells (stem cells)
Human epidermis: renewed about 15-30
days, depending on age, the region of the
body, and other factors
Cells also have cytokeratins (intermediate
(tono)filaments about 10 nm in diameter)
and melanins (transferred from
melanocytes)
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Stratum basale
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Stratum spinosum
Consists of cuboidal, polygonal, or slightly
flattened cells w/ central nucleus and cytoplasm
(filled with bundles of filaments)
Filament bundles: converge into many smallcellular extensions, terminating w/ desmosomes
located @ the tips of these spiny projections
Cells: firmly bound together by the filament-filled
cytoplasmic spines and desmosome that
punctuate the cell surface (prickle-studded
appearance prickle cells)
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Tonofibrils: end and insert into the cytoplasmic
densities (node of Bizzozero) of the
desmosomes
Maintains cohesion among cells and resists theeffects of abrasion
Soles of the feet: with thicker stratum spinosum
and more abundant tonofibrils and desmosomes
Malphigian layer (Stratum basale and stratum
spinosum): where all mitotic activities are
confined
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Tonofibrils and Desmosomes
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Stratum granulosum
3-5 layers of flattened polygonal cellsCells: w/ centrally located nuclei and
coarse basophilic granule-filled cytoplasm
(keratohyalin granules)Granules: w/ phosphorylated histidine-rich
protein as well as cystine-containing
proteins (precursors of filaggrin):promoters in the aggregation of keratin
filaments into tonofibrils
Phosphates: intense basophilia
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Keratohyalin granules
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Lamellar granules (0.10.3 m)small, ovoid
or rodlike structure containing lamellar disks that
are formed by lipid bilayers
Fuse w/ cell membrane and discharge theircontents into the intercellular spaces of the
stratum granulosum where they are deposited in
the form of lipid-containing sheets
Acts a barrier to penetration by foreign materials
and provides a sealing effect in the skin
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Lamellar Bodies
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Stratum lucidum
A translucent, thin layer of extremelyflattened eosinophilic cells (more apparentin thick skin)
Organelles and nuclei: no longer evidentCytoplasm: consists primarily of denselypacked filaments embedded in an
electron-dense matrixDesmosomes are still evident betweenadjacent cells
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Stratum corneum
Consists of 1520 layers of desiccated,flattened nonnucleated keratinized cellswhose cytoplasm is filled with a
birefringent filamentous scleroproteinkeratin
Keratin: w/ at least 6 different polypeptideswith MW of 40,00070, 000
- 3 polypeptide chains coil around oneanother to form subunits (~ 47 nm long) ofthe tonofilament
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After keratinization: cells consist only of
fibrillar and amorphous CHON andthickened plasma membranes (horny
cells)
Lysosomal hydrolytic enzymes: w/ role in
the disappearance of the cytoplasmic
organelles
Cells that will desquamate accumulate
acid phosphatase: exfoliate keratinized cell
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In thin skin: st. granulosum and st. lucidum
are less developed; st. corneum is quite
thin
In thick skin: with a st. lucidum which is a
subdivision of the stratum corneum
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MelanocytesColor of the skin: melanin and carotene, numberof blood vessels in the dermis and the color ofblood flowing
Eumelanin: dark brown pigment produced by themelanocyte ( beneath or between the cells of the
stratum basale and hair follicles)Pheomelanin: giving the hair its red color andcontains cysteine
Derived from neural crest cells
With rounded cell bodies and irregularextensions branching into the epidermis, runningbetween the cells of the basaleand spinosumlayers
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EM: pale-staining cell containingnumerous small mitochondria, a well-developed Golgi complex, and short
cisternae of RERw/ Intermediate filaments (10 nm indiameter)
Not attached to the desmosomes butthrough hemidesmosomes to the basallamina
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Melanin synthesis
Occurs in the interior of the melanocyteTyrosinasesynthesized on ribosomes
Tyrosine - 3,4-dihydroxyphenylalanine(dopa)- dopaquinonemelanin
With 4 stages (in Melanin granulematuration):
Stage I: A vesicle is surrounded by a
membrane; in the peripheryelectron-dense strands show an orderlyarrangement of tyrosinase molecules on aprotein matrix
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Stage II: The vesicle (melanosome) is nowovoid in shape, in its interior, parallelfilaments w/ a periodicity of about 10 nm
or cross-striations of about the sameperiodicity; melanin is deposited on theprotein matrix
Stage III: Increased melanin formationmakes the periodic fine structure lessvisible
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Stage IV: Mature melanin granule is visible in
LM, and melanin completely fills the vesicle
No ultrastructure is visible; the mature granules
are ellipsoid in shape with a length of 1um and adiameter of 0.4 um
Melanin granules migrate w/in cytoplasmic
extensions of the melanocyte and are
transferred to cells of the st. germinativum and
spinosum
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Melanin Synthesis
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Cytocrine secretion: melanin granules
are injected into the keratinocytes
Once inside, melanin granules accumulate
in the supranuclear regionof the
cytoplasm
Epithelial cells: a depot and contain more
pigment than melanocytes
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Langerhans Cells
Star-shaped cells
Mainly in the stratum spinosum (2-8%)
Bone-marrow-derived macrophages
capable of binding and presenting
antigens to T lymphocytes and stimulate
them
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Langerhans Cells
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Langerhans (Birbeck) granules display a tennis-racket
configuration
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Merkels Cells
Present in the thick skinof palms andsoles
Resemble epidermal epithelial cells, but
with smaller dense granules in thecytoplasm
On its base: w/ free nerve endings thatform an expanded terminal disk
Serve as sensory mechanoreceptors anddiffuse neuroendocrine system
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This diagram depicts (1) a
dendritic Merkel cell (Mc)
with its desmosomal
attachments to adjacent
keratocytes (K),intranuclear rodlet, and
membrane-bound dense
core granules (G) and (2)
a mitochondria-richmyelinated axon (A) with
postsynaptic thickening of
its terminal membrane.
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DERMIS
Composed of connective tissue
Surface: very irregular and has manyprojections (dermal papillae) that
interdigitate with projections (epidermalpegs or ridges) of the epidermis
Determines the developmental pattern ofthe overlying epidermis
In soles of the feet: induces the formationof a heavily keratinized epidermis
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Basal lamina: found between the stratum
germinativum and the papillary layer of the
dermis
Lamina reticularis: delicate net of reticularfibers underneath the basal lamina
Basement membrane: Basal lamina and
lamina reticularis
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Schematic representation of the dermoepidermal junction as visualized by electron microscopy. Within a basal
keratocyte, tonofilaments (TF) are attached to a hemidesmosome (HD) that parallels the cytoplasmic leaflet of
the plasma membrane (PM). The lamina lucida (LL), an electron-lucent zone, separates the lower border of a
plasma membrane from the electron-dense lamina densa (LD), known also as basal lamina. Within the lamina
lucida, a sub-basal dense plaque (SBDP) is situated beneath a hemidesmosome and is traversed by fine
anchoring filaments (AFT) that extend perpendicularly from the plasma membrane to mesh with the basal
lamina. Cross-banded anchoring fibrils (AFL) and dermal microfibril bundles (DMB) extend downward from thebasal lamina to interweave with type III collagen fibers in the papillary dermis
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With two layers:
- Outermost papillary layer
- Deeper reticular layer
Thin papillary layer:composed of looseconnective tissue, fibroblasts and otherslike mast cells, macrophages and
extravasated leukocytes- Constitutes the major part of the dermalpapillae
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Anchoring fibrils (structures): special
collagen fibrils inserting into the basal
lamina and extending into the dermis
Reticular layer:much thicker; composedof irregular dense connective tissue
(mainly type I collagen), thus has more
fibers and fewer cells
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The glycosaminoglycans vary in different regionsSkin: dermatan sulfate (principal
glycosaminoglycans)
From the reticular layer, thicker fibers gradually
become thinner and end by inserting into the
basal lamina; as these progress toward the
basal lamina, they lose their amorphous elastin
component, and only microfibrillar componentinserts into the basal laminathis elastic
network is responsible for the skins elasticity
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Elastic fibers in the papillary dermis are thin and, in the main, oriented somewhat
perpendicular to the epidermis, whereas elastic fibers in the reticular dermis are
thicker and tend to be arranged mostly parallel to the skin surface
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With rich network of blood and lymph vessels
(can accommodate about 4.5 % of the blood
volume)
Anastomoses/shunts: temperature and BPregulation
Rich capillary network (in papillary layer):
surrounds the epidermal ridges and functions in
regulating body core temperature and nourishingthe overlying epidermis
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Arcades of Capillaries
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Meissners corpuscle that mediates the
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Meissner s corpuscle that mediates the
sensation of touch
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Vascular supply to microlobules in the
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subcutaneous fat
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HAIRS
Elongated keratinized structures derived frominvaginations of epidermal epithelium
Everywhere except on: palms, soles, lips, dorsal
parts of the fingers and toes, prepuce and glanspenis, clitoris, labia minora and inner surface of
the labia majora, nipples
Face: 600 hairs/cm2
Remainder of the body: 60/cm2
Duration of growth and rest periods varies
according to the region of the body
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Scalp (anagen/growth periods)last forseveral years
Scalp (catagen and telogen/rest periods)
average 3 months
Arises from an epidermal invagination
(hair follicle) having a terminal dilatation
(hair bulb)
Hair bulb base- w/ dermal papilla
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Hair Cycle
2 PHASES: Resting (quiescent) Phaseshorter follicles
and the epithelium closely resembles that ofthe epidermis.
Melanocytes contains no melanin.
Shrunken bulb, there is a small cluster of cells thatare remnants of the papilla.
Active Phaseresumption of melaninproduction and follicles take fully differentiatedforms.
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A Ph
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Anagen Phase
C t Ph
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Catagen Phase
T l Ph
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Telogen Phase
The root of an anagen hair is pigmented and surrounded by a translucent inner
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g p g y
sheath, in contrast to the base of a telogen hair, which is unpigmented and is
enveloped by an inner sheath.
Hair Segment
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Hair Segment
PARTS OF THE HAIR
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PARTS OF THE HAIR
Hair follicle
External root sheath
Internal root sheath
Cell Matrix
E t l R t Sh th
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External Root Sheath
Outer follicular epithelium
Covered by a thick basal lamina called
Vitreous (Glassy) Layer.
In the bulbous portion of the hair follicle, it
is a single layer of cells corresponding to
the stratum basale of the epidermis.
I t l R t Sh th
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Internal Root Sheath
3 LAYERS:
Henles layer outer single rowof low
elongated cells in close contact with the
innermost cells of the external root sheath Huxleys layer made up of 2-3 rowsof
flattened cells that form the middle plate of the
internal root sheath.
Cuticleflat scale-like cells imbricated with
their free edges directed downward.
C ll M t i
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Cell Matrix
Mass of cells in the interior of the bulbaround the papilla.
Their proliferation, differentiation and
upward movement of these cells gives riseto the hair.
Medulla
Cortex
Cells of the follicular matrix differentiate along seven separate lines. A. Schematic view, from
outside inward shows outer sheath; Henles layer only one cell thick and the first to cornify;
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outside inward, shows outer sheath; Henle s layer, only one cell thick and the first to cornify;
Huxleys layer, two cells thick and characterized by brightly eosinophilic-staining trichohyalin
granules; cuticle of inner sheath; cuticleof hair; cortex of hair; and medulla of hair
T i h li G l
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Tricohyaline Granule
Resembles keratohyaline granules butdiffers in their staining & chemical
properties.
High content of glutamic acid, glutamateand citrulline.
H i C ti l
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Hair Cuticle
Very heavily keratinized matrix cells.
Proliferation & differentiation of the most
peripheral cells of the hair matrix gives rise
to the inner root sheath.
Melanocytes within the cells of the matrix
Graying of the hair in old age is attributed
to the gradual loss in the capacity of thesecells to produce tyrosine.
Hair Follicle and B lb
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Hair Follicle and Bulb
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Dermal papillaw/ capillary networks;loss of blood flow or vitality of the papilla
death of the follicle
Epidermal cells covering the dermalpapilla form the hair root that produces
and is continuous w/ the hair shaft, which
protrudes beyond the skin
Dermal Papilla
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Dermal Papilla
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Periods of growth: the epithelial cellsmaking up the bulb = cells in the stratumgerminativum
Cells divide constantly and differentiateinto specific cell types
Medulla: with large vacuolated andmoderately keratinized cells derived fromthe cells in the central region of the root ofthe apex of the dermal papilla
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Hair cortex: heavily keratinized, compactlygrouped fusiform cells derived from thosearound the central region of the root
Hair cuticle: layer of cells that are cuboidalmidway up the bulb and is produced bythe cells in the periphery; higher up,becomes vertical and form a layer of
flattened, heavily keratinized, shinglelikecells covering the cortex
Outermost layer gives rise to the internal
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Outermost layergives rise to the internal
root sheath (completely surrounding the
initial part of the hair shaft)External root sheathcontinuous w/
epidermal cells and near the surface
shows all the layers of epidermisGlassy membraneseparates the hair
from the dermis; a noncellular hyaline
layer
A t ili l ti th
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Arrector pili muscles: connecting the
follicle to the papillary layer of the dermis
Disposed in oblique direction, and the
contraction results in the erection of the
hair shaft to a more upright position
Contraction: causes depression of the skin
where the muscles attach to the dermis
(gooseflesh)
Arrector Pili Muscle
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Arrector Pili Muscle
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Hair color: due to the activity of themelanocytes located between the papilla
and the epithelial cells of the hair root
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Nail bedepidermis losses the stratumcorneum
Lunulaopaque, white crescent seen
through the semitransparent nail bed.
Paronychiaa painful inflammation and
swelling of the lateral folds.
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Only stratum basale and spinosum in thenail bed
Nail platearises from the nail matrix
Growth rate: 0.5mm/ week
Fingernails grow 4x faster than toenails.
Those in the middle finger are somewhat
faster than the others.
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GLANDS
Glands
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Glands
Group of specialized cells for secretion
Secretionprocess by which small
molecules are taken up and transformed,
by intracellular biosynthesis, into a morecomplex product that is then released from
the cell
Two Major Categories
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Two Major Categories
1. Exocrinedelivers their secretion into asystem of ducts opening onto an external
or internal surface.
2. Endocrinerelease their products intothe blood or lymph for transport to target
tissue in another part of the body.
Types of Release
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Types of Release
Cytokinesmolecules released by cells tomediate cell to cell communication.
Paracrinesignaling molecules diffuse to
cells in the immediate vicinity.Autocrineact upon the cell producing the
secretion.
Endocrineaffects the distant targetorgans.
Two Modes of Secretion
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Two Modes of Secretion
1. Regulated Secretory Pathwayglandular cells concentrate and store their
product until a neural or hormonal signal
calls for its release.2. Constitutive Secretory Pathway
transported directly to the cell surface.
GLANDS OF THE SKIN
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GLANDS OF THE SKIN
Sebaceous GlandsEmbedded in the dermis; 100/cm2butincreases to 400-900/cm2(face, forehead
and scalp)Are acinar glands (w/ several aciniopening into a short duct which ends in theupper portion of a hair follicle)
Glans penis, clitoris and lips: opensdirectly onto the epidermal surface
Sebaceous Gland
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Sebaceous Gland
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Sebocyte
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A type of Holocrine gland: product ofsecretion (mixtures of triglycerides, waxes,squalene, and cholesterol and its esters) isreleased w/ remnants of dead cells
Begin to function at puberty; men(testosterone); women (ovarian andadrenal androgens)
Functions: w/ weak antibacterial andantifungal properties
Cycle of a sebaceous gland
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Cycle of a sebaceous gland
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Sweat glands
Widely distributed except in the glans
penis
Eccrine (Merocrine) type:simple, coiledtubular glands whose ducts open at the
skin surface
Ducts: do no divide and the diameter isthinner than that of the secretory portion
Eccrine Unit
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Eccrine Unit
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Secretory portion: embedded in the dermis andmeasures ~0.4 mm in diameter surrounded bymyoepithelial cells
Innervated by cholinergic nerves
2 types of cells: dark (mucoid cells) and clearcells
Dark cells:pyramidal cells lining most of theluminal surface; basal surface does not touchthe basal lamina; cytoplasmw/ rod-shapedmitochondria, well-developed Golgi complex,cisternae of RER, and numerous free ribosomes
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Clear cells:devoid of secretory granules butcontain an abundance of glycogen particles; thebasal plasmalemma has the numerousinvaginations characteristic of cells involved in
transepithelial salt and fluid transport; ductslined by stratified cuboidal epithelium
Fluid secretions: not viscous and contains littleprotein
Main components: water, sodium chloride, urea,ammonia, and uric acid
Dark and Pale Cells
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Dark and Pale Cells
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Sodium: 85 meq/L
An ultrafiltrate of the blood plasma (from
network of capillaries that intimately
envelop the secretory region of eachgland)
Eccrine Sweat Gland
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Eccrine Sweat Gland
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Apocrine type:present in axillary,areolar, and anal regions
Much larger (3-5 mm in diameter) than
eccrine sweat glands; embedded in thesubcutaneous tissue, and ducts open intohair follicles
With viscous secretion that is initially
odorlessInnervated by adrenergic nerve endings
Apocrine Gland
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poc e G a d
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Apocrine Sweat Gland
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p
Eccrine and Apocrine Glands
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p
Eccrine w/o hair follicle
Secretion starts at birth
cholinergic
Apocrine Appendage
Puberty
adrenergic
VESSELS AND NERVES
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Arterial vessels: w/ two plexuses (betweenpapillary and reticular layers and between
the dermis and subcutaneous tissue)
Veins: w/ three plexuses (2 in the positionas of the arterial, and the third in the
middle of the dermis)
Lymphatic vesselsalso w/ two plexuses
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EXOCRINE GLANDS
Exocrine Glands
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Glands that maintain their continuity withthe covering epithelium
Unicellular or multicellular
Classification of Exocrine Gland
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1. Unicellular2. Multicellular
a . Tubular
b . Alveolar
c . Tubulo-alveolar
d . Saccular
Unicellular Glands
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Composed of a single cellGoblet or mucous cells
Secretes mucin
Thecaexpanded cup-shaped rim of
cytoplasm filled with secretory droplets
Mucin is produced via the regulated
secretoy pathway
Lifespan: 4 days
Multicellular Glands
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Secretory epithelial sheetIntraepithelial gland
Glands with ducts
Secretory Epithelial Sheet
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y p
Refers to any covering epithelium wheremost, if not all, of the cells are secretory
Eg. ependyma, simple cuboidal
epithelium that lines the cavities of the
CNS
Intraepithelial Gland
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p
Refers to groups of secretory cells in acovering or lining epithelium that gather
together around a small orifice-that
serves as a duct-and from shallowinvaginations within the epithelial surface
Eg. epithelium lining the penile part of
the male urethra
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Simple Tubular Gland
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Glands with Ducts
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B. Simple coiled tubular coiled tubule connected to an unbranched
secretory ducts.
E.g. eccrine and merocrine sweat gland of theskin
Glands with Ducts
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C. Simple branched tubular The terminal excretory portion bifurcates or
may have unbranched short excretory duct.
Glands of the oral cavity (tongue), esophagus,mucus-secreting glands of the pylorus &
duodenum
Glands with Ducts
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D. Simple acinar (alveolar)single acinus is associated
with an unbranched duct-paraurethral and periurethral glands
E. Simple branched acinar (alveolar)several acini
clustered around a simple duct
-mucus-secreting glands of cardia (stomach) and
sebaceous glands (skin)
F. Compound acinar (alveolar) glands
Duct branches repeatedly
Terminal portions are bulbous or pear-shapedstructures made up of pyramidal cells around thesmall lumen
Excretory portion of pancreas, mammary glands
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Simple branched acinar
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Glands with Ducts
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Compound tubuloacinar (alveolar) glands
Secretory cells form the walls of short tubuleshaving a number of acini along their sides and
at their blind end.
E.g. submandibular salivary glands, mammarygland, lacrimal gland & pancreas, glands of
respiratory passages
Compound saccular glands
Great size and large lumen of their secretory
units.
E.g. mammary glands & prostate
Glands with Ducts
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Compound tubular- Submucosal glands of Brunner
(Duodenum), mucous gland in mouth,
bulbourethral glands and seminiferoustubule (testis)
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Nature of Secretion
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1. Mucoussecretes viscid fluid rich inmucopolysaccharide that has lubricating &protective function. Eg. Goblet cells, secretorycells of sublingual salivary glands, surface cells
of the stomach2. Serouswatery secretion rich in enzymes.Eg. Parotid gland and pancreas
3. Mixedthe bulk of the gland is made up of
mucous cells with flattened serous cells formingcrescentic caps over the end of the acini (serous
demilumes). Eg. Submandibular gland
Duct System
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Group of acini drain into: Intercalary ductsConverge: Intralobular ducts
Interlobular ducts
Lobar ducts
Main ducts
Organization
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Large exocrine gland (pancreas) enclosein a capsule and extend inward to
separate the gland into lobes.
Further subdivision by thinner septa:lobules
Lobules are made up of microscopic
subunits: acini or alveoli
Ducts Lining Epithelium
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Smallest ductsquamous epitheliumLarger ductscuboidal cells
Main ducts: columnar cells
Regulation of secretion:
1.Autonomic
2.Hormones3.Dual Mechanism
Mammary Gland
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MAMMARY GLANDS
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Each gland: w/ 15-25 lobes of thecompound tubuloalveolar type
Each lobe: has its own excretory
lactiferous ductDucts: 2-4.5 cm long, emerge
independently in the nipple (w/ 15-25
openings each about 0.5 mm in diameter)
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Breast Lobule
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Breast Lobule
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Embryonic Breast Development
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Appear in a 6-week-old human embryo: pair ofthickenings of the epidermis (milk lines)
Extend from the forelimb to the hindlimb on the
ventral side
Caudal portion: regress early in development
In the thoracic region (2ndtrimester): 15-25
ingrowths of the epithelium penetrate the
underlying connective tissue and give rise to thefuture lactiferous ducts
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Newborns (both sexes): glands havediameter of 3.5-9 mm and consist of ducts
that may be swollen with secretory
material
During Puberty and Adult
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Before puberty: mammary glands are composedof lactiferous sinuses and several branches of
lactiferous ducts
Breast enlargement: result of the accumulation
of adipose tissue and collagenous connective
tissue, w/ increased growth and branching of
lactiferous ducts
Ovarian estrogen: proliferation of the ducts andaccumulation of fats
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Lobule: characteristic structure of the adultfemale gland
Developed at the tips of the smallest ducts
(terminal interlobular ducts)Consists of several intralobular ducts that
empty into one terminal interlobular duct
Each lobule: embedded in loose, cellular,intralobular connective tissue
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Lactiferous sinusesdilatation of ductsnear the nipple opening
Lined by stratified squamous epithelium
EM: cells adjacent to the lumen are ductalepithelial cells; lying on the basal laminaare closely packed myoepithelial cells
Terminal interlobular ducts: lined by simple
cuboidal epithelium resting on basallamina
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Lymphocytes and plasma cells: found inthe intralobular connective tissue
Increases toward the end of pregnancy
Ovulation (estrogen is at its peak): w/ductal proliferation
Premenstrual phase: w/ greater hydration
of connective tissue
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Nipple epithelium: rests on a layer ofconnective tissue rich in smooth muscle
fibers (disposed in circle around the
deeper lactiferous ducts)
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Each alveolus: w/ 4-6 stellatemyoepithelial cells; between the alveolar
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y pepithelial cells and the basal lamina
Synergistic action (mainly estrogen,progesterone, prolactin, and humanplacental lactogen)
Lactation: milk is produced by theepithelial cells of the alveoli andaccumulates in lumens and inside
lactiferous ducts
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Secretory cells: become small and lowcuboidal, and their cytoplasm contains
spherical droplets (neutral triglycerides)
Lipids pass out of the cells into the lumenand enveloped with a portion of the apical
cell membrane
Postlactational Regression
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Alveoli undergo degenerationSloughing of whole cells and autophagic
absorption of cellular components
Dead cells and debris are removed bymacrophages
Myoepithelial cells and the basal lamina
persist and reused in the next pregnancy
Senile Involution of the Breast
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After menopause, mammary gland ischaracterized by a reduction in size and
the atrophy of secretory portion and ducts
Atrophic changes also occur in theinterlobular connective tissue
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END