Cutaneous Membrane Accessory Structures

Made up of all 4 tissue types . . . .??

Two Major SubdivisionsTwo Major Subdivisions

• Cutaneous Membrane– Epidermis– Dermis– Hypodermis

• Accessory Structures – Excretory glands (?)– ?– ?

EpidermisEpidermis

• Type of Epithelium?

• _vascular

• Different layers (=strata)– 4 layers in

thin skin

– 5 layers in thick skin

Stratum germinativum

= stratumbasale

Innermost, single layer

Stratum GerminativumCell types:• Stem cells (basal cells)• Melanocytes• Merkel cells (touch receptors in hairless skin only)

Stratum spinosumSeveral cells

thick

Stratum Spinosum• Stem cell daughter cells (some can still divide)• Melanocytes & Langerhans cells• Establishment of Desmosomes

Stratum granulosum

Stratum Granulosum• Cells displaced from stratum spinosum Keratinocytes• Production of keratohyalin and keratin fibers• Cells start to die. Dehydration leaves interlocked layers of

keratin, keratohyalin & PL membranes

Stratum lucidum

Stratum Lucidum• In palms of hands and soles of feet • Cells do not stain well clear (lucid) looking

• Many layers of flattened, dead cells, filled with keratin• Continually shed in sheaths• Water-resistant but not water proof ( insensible

perspiration)• Relatively dry - advantage?• Keratinization occurs everywhere except for anterior

surface of eye

Stratum corneum15-30 layers

(much thicker in thick skin)

Stratum Corneum

Thin vs. Thick Skin

• Up to 6 x thicker• Where??

• Average 0.08 mm• Rest of body

Refers to epidermis

Contour of skin surface follows pattern of epidermal ridges. Advantage ??

Unique fingerprints

cc

Skin Color depends on 3 pigmentsHemoglobin (dermal blood supply)

– Reddish tones– Pale, due to?– Bluish (=?), due to?

Melanin – Produced by melanocytes of stratum basale

Carotene Obtained from plant foods

Number of melanocytes same in all people, production levels differ !

Melanocytes

Function ?

DermisDermis

Papillary layer loose c.t.

Reticular layer dense irregular c.t.

Papillary LayerPapillary Layer

• Dermal papillae project between epidermal ridges.

Consist of

• Loose c.t. = _____

• Capillaries

• Tactile receptors

M

Reticular LayerReticular LayerConsist of

• ______________ c.t.

• + ??

Pacinian corpuscule(deep pressure)

HypodermisHypodermis

• 2 other names ?2 other names ?

• Indistinct boundary (c.t. fibers interwoven)

Made up of– Loose c.t. + lots of . . .

Function– Stabilization of skin while

allowing for independent movement

Clinical Brief:

• Wrinkles• Stretch marks

(lineae albicantes)• Decubitus• Transdermal medication

– Advantage and disadvantage?– Examples?

• Hypodermic needles

Lines of cleavage

Accessory Structures: Hair Follicles & Hair

• 5 mio hair/hu body. (98% not on top of head)

• Three hair types (vellus – intermediate – terminal)

• Function ?

• Hair color

• Growth cycle

Skin Glands: 1) Sebaceous GlandsSkin Glands: 1) Sebaceous GlandsHolocrineSebum discharged into hair follicles

(lubrication & bactericidal)excessive shampooing leads to dry & brittle hair

Sebaceous follicles, = Large sebaceous glands, discharge directly to epidermis

Where ?Folliculitis; furuncle (boil); acne

2) 2) Apocrine Sweat GlandsSweat Glands• Have merocrine secretion!!

• Empty into hair follicle

• Location: armpits, groin, nipples

• Viscous, cloudy secretion good nutrient source for bacteria (odor !!)

• Secretion may contain Pheromones

• Secretion begins at puberty and is stimulated during emotional distress (cold sweat)

3) Merocrine Sweat Glands3) Merocrine Sweat Glands

• Empty directly onto skin surface

• Location: most all over body (esp. abundant on palms & soles: ~ 500/cm2)

• Clear, watery secretion (99% H2O; rest NaCl + some waste products)

• Sensible perspiration; Function: ?

For purpose of completion:

Other integumentary Glands:

• Mammary glands: Modified apocrine sweat glands

• Ceruminous glands: modified sweat glands in __________

Nails not covered.Skin and Aging Process