Integumentary SystemIntegumentaryIntegumentary SystemSystem

Dr. Carmen E. RexachAnatomy 35

Mt San Antonio College

Integumentary system• Components

– Skin – integument• Dermis and epidermis• Supported by hypodermis

– Accessory organs• Hair • Nails• Cutaneous gland

Functions• Protection from trauma and infection

– Sensory functions– Physical barrier– Immune effector cells

• Prevents desiccation and water imbalance– Keratin and waterproofing

• Synthesis of Vitamin D– Important for uptake of Ca++

• Sensory reception• Excretion by secretion• Regulation of temperature

– Insulation– Vasoconstriction and vasodilation

Layers of Epidermis

Stratum corneum

Stratum lucidumStratum

granulosum

Stratum spinosumStratum

basale

Dermis

Thick skin vs. thin skin

• Thick skin– Palms and soles– Epidermis = 400-

600μm thick– 5 layers– Has sweat glands– No hair follicles,

sebaceous glands, arrector pili muscles

• Thin skin– Rest of body– Epidermis = 75-150μm

thick– Thin stratum corneum– Stratum lucidum and

granulosum not present in distinct layers

Eccrine & apocrineeccrineeccrineSweat glands

YesYesNoSebaceous glands

YesYesNoArrector pili

YesYesNoHair

NoNoYesStratum lucidum

445# epidermal layers

Axillary skin (thin)Thin skinThick skinCharacteristic

Summary table

Stratum corneum• Up to 30 layers of

dead keratinized cells

• Water resistant

Stratum lucidum• Only found in thick

skin• Cells are anucleate

and lack organelles• Intermediate form

of keratin (eleidin) fills cells

Stratum granulosum• 3-5 layers of

flattened keratinocytes

• Contain keratohyalinegranules

• Also contains some dendritic cells

Stratum Spinosum

• Thickest stratum in thin skin

• Lower layers contain mitotic cells

• Cells flatten and fill with keratin as move to the top

• Connected by desmosomes = confers a spiny appearance

Stratum Basale• Germinative layer = mitosis• Single layer of cells resting

on basement membrane– Stem cells– Keratinocytes– Tactile cells– Melanocytes

• Cuboidal to low columnar• Gives rise to cells that are

moved to the upper layers

Epidermal cell types

• Keratinocytes• Nonkeratinocytes

– Melanocytes– Merkel cells– Langerhans cells

Keratinocytes

• 90% of epidermal cells• Undergo mitosis in stratum basale at

night• Life expectancy = 20-30 days• Accumulation of keratin filaments

causes death and sloughing off• Cytomorphosis of keratinocytes is

responsible for 5 tissue layers in epidermis

Langerhans cells

• Dendritic cells• 2-4% of epidermal

cells• APC’s• Replaced by cells

produced in bone marrow

Merkel Cells• Found in stratum

basale• Abundant in

fingertips, oral mucosa, base of hair follicles

• Associated with tactile discs

• Believed to be mechanoreceptors

Melanocytes• Stratum basale,

sometimes in superficial dermis

• Melanosomes = oval granules containing melanin

• Epidermal melanin unit

The Dermis

• papillary layer– folded area

immediately deep to the epidermis

– Areolar CT• reticular layer

– the deepest, largest part of the dermis

– Dense irregular CT– Source of leather in

animals

The Hypodermis

• Subcutaneous layer• deep to the dermis• contains adipose and

areolar CT• Very vascular• Function

– Binds skin to underlying tissues

– padding

Human Skin Pigments• Melanin

– Brown to black (eumelanin)– yellow to red (pheomelanin)– protection from UV light

• Carotene– yellowish pigment found in certain

vegetables (carrots) accumulates in the fatty parts of the dermis

• Hemoglobin– blood pigment, adds “redness” to skin color

Epidermal Derivatives and Accessory Structures

• Hair (Pili)• Nails• Glands

Hair (Pili)• Hard keratin growing

from hair follicle• Hairless areas (glabrous

skin)– Lips, nipples, soles, palms,

etc.• Function

– Insulation– Protection

• Types of hair– Lanugo– Vellus– Terminal hair

Types of hair• Lanugo

– Appears during 3rd trimester– Unpigmented, fine, downy hair replaced before

birth• Vellus

– Hair found on arms and legs throughout life– Lightly pigmented or unpigmented hair present

at birth• Terminal hair

– Coarse, pigmented– Grows on scalp, eyelashes, eyebrows, beard– Replaces vellus in axilla and pubic regions

during puberty

Types of hair

Structure of hair and follicle• Bulb

– Origin of hair in dermis• Root

– Hair in follicle• Shaft

– Above skin surface• Dermal papilla

– Vascular CT• Cross section

– Medulla, cortex, cuticle• Layers of follicle

– Epithelial root sheath– CT root sheath

Hair texture = cross sectional shape Hair color = pigment granules

Nails = Modified ScalesNail plate

Digital clubbing

onychomycosis

Glands of Integument

• sebaceous– Holocrine & branched

acinar– secretes sebum (hair oil)

Sudoriferous glands

• Eccrine (merocrine),– most numerous sweat

glands– react to temperature

increase.

Sudoriferous glands• Apocrine

• sweat glands in the axillary and pubic regions

• react to emotional stress.

• Mammary• modified in

females to secrete milk (apocrine)

Ceruminous glands

• secrete cerumen(holocrine)

• found only in the external auditory meatus

Skin cancer• UV light exposure often implicated• Types

– Basal cell carcinoma• Most common, from stratum basale• Least dangerous

– Squamous cell carcinoma• Keratinocytes of stratum spinosum• Can metastasize, early treatment usually effective

– Malignant melinoma• Most deadly• Melanocytes of preexisting mole

ABCD:What to look for

Malignant melanoma

basal cell carcinoma

Squamous cell carcinoma of lip from smoking

Evaluating skin lesions• Here is a great website that teaches

you how to distinguish between benign and malignant lesions!

• http://matrix.ucdavis.edu/tumors/new/tutorial-intro.html