Skin and Breast

8/12/2019 Skin and Breast

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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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y


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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

Documents

Skin and Breast