histology - kamil espiritu - med 1b 2012 Lecture 14

INTEGUMENTARY SYSTEM

INTEGUMENT → skin + specialized appendages

SKIN - largest single organ of the body- comprising 16% of total body weight

function: - protection- thermoregulation- sensation / sensory perception- metabolic functions

-- adipose cells in hypodermis is a major storage of energy (triglycerides)

-- vitamin D synthesis-- enzymes from epidermal cells

(carboxylase, phosphatase, sulfatase) - principal organ for sexual attraction

layers:

EPIDERMIS- stratified squamous keratinizing epithelium- derived from the ectoderm

DERMIS ( corium / cutis vera )- dense irregular CT- derived from the mesoderm- provides mechanical support and a vascular bed

HYPODERMIS ( subcutaneous tissue / subcutis )- not considered to be part of the skin- layer of varying thickness of adipose tissue beneath

the dermis

EPIDERMO-DERMAL JUNCTION- uneven and irregular lines because of alternating

⋅ downward projections epidermal ridges / rete pegs

⋅ upward projections dermal papillae

Cells of the Epidermis

KERATINOCYTES- most numerous cell of the epidermis -- 90%- produces keratin

stratum characteristics

Basale or Germinativum or Cylindricum

⋅single layer of basophilic tall columnar cells with mitotic figures to replace desquamated cells

Spinosum orPrickle Cell Layer

⋅several layers of polyhedral cells with intercellular ridges spiny projections that interconnect the cells

⋅ presence of desmosomes

Granulosum ⋅intensely basophilic diamond-shaped cells with keratohyalin granules

Lucidum ⋅consists of non-nucleated cells with clear or eleidin droplets

Corneum or Horny Layer

⋅ superficial layer of dead cornified cells

Stratum Malphigii = Stratum Basale + Stratum Spinosum

MELANOCYTES- scattered between keratinocytes of the stratum basale

and stratum spinosum

- differentiate from melanoblasts from the neural crest

- synthesizes melanin is formed on a specific cell particle mature melanosome

- in routine preparations: body is clear and cannot be identified but is made visible with “DOPA” reagent (dihydroxyphenylalanine) which colors them black

- tyrosinase is responsible for synthesis of melanin from tyrosine

- activity of melanocytes increases with exposure to X-rays and UV light

histology - kamil espiritu - med 1b 2012 LANGERHAN'S CELLS- star-shaped cells with numerous dendritic processes

- found principally in the stratum spinosum

- appear as clear cells but sharply delineated by impregnation with gold chloride

- EM: indented nucleus, well-developed Golgi complex and RER, clear cytoplasm with rod-like inclusion called Birbeck granules

- with immunological function

- responsible for contact dermatitis

MERKEL'S CELLS- found in the stratum germinativum, often in assoc

with intraepithelial nerve endings

- irregularly-shaped nuclei with less electron-dense cytoplasm containing tonofilaments

- function as mechanoreceptors

Layers of the Dermis

Thin PAPILLARY or SUB-EPITHELIAL Layer- typical loose CT composed of a meshwork of thin

collagenous and elastic fibers thrown into the papillae

- contains vascular and nervous papilla

- rich capillary bed in the dermis acts as thermoregulators and nourishment for the epidermis

Thick RETICULAR Layer- main fibrous bed of the dermis

- with coarse collagenous and bundles of elastic fibers

- direction of the fibers form the “Langer’s line” wherein surgical incision are made for less scar formation

additional info…

Hypodermis- constitute the superficial fascia- with fat cells : panniculus adiposus on the abdomen- devoid of fat : eyelids, penis, scrotum

Thick Skin Thin Skin

⋅ palms of hands, fingers, soles, toes

⋅ thickness of epidermis & prominent strat corneum

⋅ abundant sweat glands

⋅ no pilosebaceous follicles

⋅ prominent grooves and ridges because of tall dermal papillae

⋅ numerous arterio-venous anastomosis

⋅ all regions of the skin except palms, soles, fingers, toes

⋅ thin epidermal layer & less prominent strat corneum

⋅ few sweat glands

⋅ presence of pilosebaceous follicles

⋅ lacks ridges and grooves with checkered network of lines

⋅ absent or few arterio-venous anastomosis

SKIN APPENDAGES

SEBACEOUS GLANDS

- assoc with a hair follicle pilosebaceous unit

- simple or branched alveolar

(saccules) in

histology - kamil espiritu - med 1b 2012 morphology appearing like a bunch of grapes

- holocrine gland-- total disintegration of

secretory cells with sebum (destruction!)

- ↑ activity during puberty

- becomes plugged with sebum, debris and

bacteria resulting in blackheads and acne

HAIR FOLLICLE

- invagination of the epidermis consisting of

medulla:int epidermal root sheath

-- root sheath cuticle Huxley’s layer

Henle’s layer

cortex:ext dermal root sheath

-- derived from the dermis-- direct continuation of

the malphigian layer

- expands into a hair bulb at its deep end

ARRECTORES PILORUM MUSCLE- oblique bands of smooth muscle inserted into middle

of hair follicle creating a triangle with surface

- contraction cause hair to stand on its end"goose flesh appearance"

ORDINARY SWEAT GLANDS- found in palms, soles and foreheads

- simple coiled tubular in morphology made up of clear and dark cells

- merocrine / eccrine in type-- secretion discharged by exocytosis

- stimulus is heat, under control of hypothalamicthermostat (thermoregulation)

- duct -- opens into epidermis as sweat pore -- re-absorb sodium without water -- sweat becomes hypotonic

APOCRINE / ODORIFEROUS SWEAT GLANDS- found in axilla, mammary areola, labia majora and

circumanal region

- less coiledwider lumenmore numerous myoepithelial cellssecretion is thick milky fluid with lipid dropletsopens into a hair follicle

- stimulus: emotional stresssympathetic discharge

- responsible for the production of body odor

NAILS- found on dorsal surfaces of terminal phalanges- consists of clear cells with shrunken degenerated nuclei- contain hard keratin

- made up of

⋅ nail root - nail beneath a fold of skin with whitish lunula

⋅ nail body - attached on a covered portion w/c is

pink due to vascular tissue

⋅ free edge - anterior unattached extension

- nail growth occurs in matrix of nail plate, a semilunar area of proliferative cells on proximal ventral surface of nail groove

- protection and tactile

Blood Vessels of the Skin

blood supply comes from the large arteries in thesubcutaneous layer

Rete Cutaneum- vessels in the superficial part from a horizontally

oriented network at its junction between the dermis and hypodermis

Rete Subpapillare- network of blood vessels between the papillary and

reticular layers of dermis

Arterio Venous Anastomosis - common in deeper layers of dermis

Glomus Body- special type of AV anastomosis for temperature

regulation in the fingers, toes and beneath the nails

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

SHOUT OUTs:

histology - kamil espiritu - med 1b 2012 fIrst of aLL, i'd like to c0ngratuLAte the ust-fms w0men's

basketball team, f0r pLacing 3rd in the th0masian g0odwill

games.. r0ck n r0ll punks! -- karisse

B2, keLan ang next p0ker night?! hehe -- b0ss

fAn ako ni miKey, i want to meet him.. :) -- kamil

camila, gagaWa rin ak0 ng fans club m0.. -- mItch fan

hi subsec B1!! hello din kay k0key, baSha, babs, at antuKin,, group study na tayo ulit!! haha -- blackboy

waLa ak0 gUsto batiin.. -- plastic

et0, nagpapa-greet.. hello to mr. martin paul garcia!! =)

go kirsten-edison loveteam!! -- anonymous

t0xic!! G0dbless!! -- mj

jarren! d0nt play with the **jayjay m0del >_< -- mcneil

crush,, mLapit na vaLentine's dAy,, fl0wers k0 ah.. kaHit pitas lang taBi taBi, ok na.. -- ^_^