THE SKIN • Function

– Protective covering

• Bacterial infection

• Physical trauma

– Receptors

• Touch, pressure, pain, heat and cold

– Vitamin D production

• UV light

– Regulation of body temperature

• Dilation or constriction of blood vessels

• Sweat glands

Epidermis

Dermis

Hypodermis

(Subcutaneous

Layer)

SKIN REGIONS

SKIN REGIONS

• Epidermis

– Protective outer

epithelial layer

– Avascular

Dermis

Tough, fibrous

connective tissue

layer

Largest region of

the skin

Vascular

SKIN REGIONS

Hypodermis

Region just deep to

the dermis

Adipose and areolar

C.T.

Anchors the skin

SKIN REGIONS

Stratum corneum

Stratum lucidum

Stratum granulosum

Stratum spinosum

Stratum basale

LAYERS of the EPIDERMIS

THE EPIDERMIS

• Definition

– Keratinized, stratified squamous E.T.

• Layers

– Five layers in thick skin

– Four in all other skin

THE EPIDERMIS

• Cells

– Keratinocytes

• Most numerous cell type

• Produce the protein keratin for waterproofing and

protection

• Replaced every 25 to 45 days

EPIDERMAL LAYERS

• Stratum Basale

– Deepest layer

– Attached to dermis

– Single layer of cuboidal

keratinocytes

– Mitotic layer

– Contains melanocytes

• Produce the pigment melanin

– Contains Merkel’s discs =

• Sensory nerve endings

• Pressure

melanocytes

EPIDERMAL LAYERS:

Stratum basale

EPIDERMAL LAYERS

Stratum spinosum

Several layers of

keratinocytes with a “spiny”

appearance

Scattered melanin granules

Langerhans cells =

macrophages

EPIDERMAL LAYERS:

Stratum Spinosum

EPIDERMAL LAYERS

Stratum granulosum

Thin region of dark-

staining cells

Flat cells with

keratohyaline granules

Cells above are dead

EPIDERMAL LAYERS:

Stratum Granulosum

EPIDERMAL LAYERS

Stratum lucidum

Only present in thick

skin

Thin, translucent layer

of dead keratinocytes

EPIDERMAL LAYERS:

Stratum Lucidum

EPIDERMAL LAYERS

Stratum corneum

Outer, loose layer of

dead, flaky cells

Protects skin from:

Abrasion or penetration

EPIDERMAL LAYERS:

Stratum Corneum

THE DERMIS

Definition

A thick, flexible C.T. layer

Rich in nerve fibers

Very vascular

Layers

Papillary layer

Reticular layer

THE DERMIS

Papillary Layer

Loosely woven

Highly vascular

Contains:

Dermal papillae

Meissner’s corpuscles

• Detect touch

Free nerve endings

• Detect pain

Larger dermal folds form

ridges = fingerprints

On palms of hands and

soles of feet

dermal papillae Meissner’s

corpuscle

LAYERS of the DERMIS

dermal papilla

epidermal peg

STRUCTURES of the DERMIS

Meissner’s Corpuscle

STRUCTURES of the DERMIS

Reticular Layer

Makes up 80% of the

dermis

Dense, irregular C.T. rich

in collagen

Contains:

Hair follicles

Sebaceous glands

Blood vessels and nerves

Pacinian corpuscles in

deep regions

• Detect crude touch; deep

pressure

Pacinian corpuscle

LAYERS of the DERMIS

Pacinian Corpuscle

STRUCTURES of the DERMIS

Three Pigments Determine Skin Color

Melanin

Brown to black pigment

Prevents UV damage

Carotene

Yellowish, orange pigment

Noticeable in the palms and soles

Hemoglobin

Red pigment when oxygenated

Gives the skin a bluish or gray appearance when

poorly oxygenated (cyanosis)

SKIN COLOR

Definition

Keratinized cells produced by hair follicles

Hair Structure

Papilla

At the hair base

Supplies the cells with nutrients

Arrector pili

Smooth muscles

Pull hair upright

APPENDAGES of the SKIN:

Hair and Hair Follicles

papilla

epidermal tissue

Hair and Hair Follicles

Arrector Pili Muscle

Hair and Hair Follicles

Types of Hair

Vellus Hair

Soft body hair of children and adult females

Terminal Hair

Coarse, longer growing hair

Found:

• Eyebrows, head, armpits, pubic regions of

adults

• Face, chest, arms and legs of adult males

APPENDAGES of the SKIN:

Hair and Hair Follicles

Definition

Epidermal modifications

Protects the dorsum of the

fingers and toes

Contain keratin

APPENDAGES of the SKIN:

Nails

Two Types:

Eccrine Sweat Glands

Open to skin surface

Regulation of body temperature

Merocrine

sweat gland

APPENDAGES of the SKIN:

Sudoriferous (Sweat) Glands

Apocrine Sweat Glands

Open into hair follicles

in anal, groin and

axillary region

Active at puberty

Not important in thermoregulation

Active during stress

Apocrine

sweat gland

APPENDAGES of the SKIN:

Sudoriferous (Sweat) Glands

Sudoriferous (Sweat) Glands

Definition

Modified sweat glands

Within breasts

Produce milk following

childbirth

mammary

glands

APPENDAGES of the SKIN:

Mammary Glands

Definition

Simple alveolar glands

found all over the body

except on the palms

and soles

Near hair follicles

Secretes sebum

Sebaceous

gland

APPENDAGES of the SKIN:

Sebaceous (Oil) Glands

Sebaceous (Oil) Glands

Hyperthermia

An abnormally high body temperature

Can result in:

• Heat exhaustion (headache, vomiting, and

tiredness)

• Heat stroke (dizziness, confusion, delusions)

• Increased fluid intake and possible medical

care are needed in both cases

Fever

• Hyperthermia brought on by illness

• Body’s attempt to fight off infection

SKIN DISORDERS

Hypothermia

An abnormally low body temperature

Results in:

• Shivering, incoherent speech and lack of

coordination

• Body functions slow and death occurs when

metabolism stops completely

• Person must be warmed immediately

SKIN DISORDERS

Skin Cancer

Squamous cell carcinoma and basal cell

carcinoma

Most common

Likely caused by sun exposure

Surgical removal is the standard treatment

Melanoma

Arises from melanocytes

Can metastasize

SKIN DISORDERS

Basal Cell

Carcinoma

Squamous Cell

Carcinoma

Malignant

Melanoma

SKIN CANCER

Burns

Factors affecting burn severity

Depth of burn

Extent of area burned

Classification of burns

1st degree burns

• Epidermis is burned: redness and pain

• Damaged skin peels off

SKIN DISORDERS

Burns

Classification of burns

2nd degree burns

• Extends through epidermis and part of the dermis

• Results in redness, pain and blisters

• May result in scarring

SKIN DISORDERS

Burns

Classification of burns

3rd degree burns

• Entire thickness of skin is burnt

• Blood vessels, sweat glands, and other skin

accessories are also burnt

• Fluid and heat loss and bacterial infection

• Skin grafting required

• Survival chances are not good if large area

SKIN DISORDERS

2nd Degree Burn 3rd Degree Burn

1st Degree Burn

BURNS