Chp. 5 Lec: The Integumentary System

Protection of underlying tissues and organs

Function of the integument

Excretion of salts, water, and organic wastes

Function of the integument

Maintenance of normal body temp.

Function of the integument

Production of melanin

Function of the integument

Production of keratin

Function of the integument

Storage of lipids

Function of the integument

Detection of touch, pressure, pain, etc.

Function of the integument

Coordination of immune response

Function of the integument

Epidermis is made of this tissue

Stratified squamous epithelium

Epidermis is avascular, which means

There few to no blood vessels

Nutrients and oxygen diffuse from capillaries in the dermis

Epidermis

What is the cell of the epidermis called?

Keratinocytes

Body’s most abundant epithelial cells

Keratinocytes

Have large amounts of keratin

Keratinocytes

Keratins form

Tissues of the hair, nails, and the outer layer of the skin

The 2 types of skin are

Thin skin and and thick skin

Covers most of the body

Thin skin

Has 4 layers of keratinocytes

Thin skin

Covers palms of the hands and soles of feet

Thick skin

Has 5 layers of keratinocytes

Thick skin

Thick as wall of plastic sandwich bag

Thick skin

\# of strata (layers) of keratinocytes in thick skin

5

The strata of keratinocytes in thick skin are from

Basement membrane to free surface

Stratum basale

Strata of keratinocytes in thick skin

Stratum spinosum

Strata of keratinocytes in thick skin

Stratum granulosum

Strata of keratinocytes in thick skin

Stratum lucidum

Strata of keratinocytes in thick skin

Stratum corneum

Strata of keratinocytes in thick skin

\-Multiple layers of flattened, dead, interlocking keratinocytes

\-Water resistant not waterproof

Stratum Corneum

Appears as glassy layer in thick skin

Stratum lucidum

\-Keratinocytes produce keratin

\-Keratin fibers develop as cells become thinner and flatter

\-Over time plasma membrane thickens, organelles disintegrate, and cells die

Stratum granulosm

Keratinocytes are bound together by desmosomes

Stratum spinosum

\-Deepest, basal layer

\-Attachment to basement membrane

\-Has basal cells (stem cells), melanocytes, and tactile cells (Merkel cells)

Stratum basale

“Horny layer”

Stratum corneum

\-Exposed surface of skin

\-Exposed cells shed after 2 weeks

Stratum corneum

In the Stratum corneum, water is lost from skin in 2 ways

\-Insensible perspiration

\-Sensible perspiration

•Water diffuses across stratum corneum and evaporates from skin

•500 mL per day

•Rate increases if stratum corneum is damaged (e.g., from burns)

Insensible perspiration

Water excreted by sweat glands

Sensible perspiration

“Clear layer”

Stratum lucidum

Found only in thick skin

Stratum lucidum

Covers stratum granulosum

Stratum lucidum

“Granular layer”

Stratum granulosum

–Three to five layers of keratinocytes

–Produced from cells of stratum spinosum

–Most cells stop dividing, produce keratin and keratohyalin

–After the production of proteins, cells die

Stratum granulosum

–Forms dense granules

–Promotes cellular dehydration and cross-linking of keratin fibers

Keratohyalin

“Spiny layer”

Stratum spinosum

–Eight to ten layers of keratinocytes bound by desmosomes

–Cells appear spiny in histological sections

–Produced by division of cells in stratum basale, some of which continue dividing

Stratum spinosum

Has dendritic (Langerhans) cells

Stratum spinosum

Dendritic (Langerhans) cells

Active in immune response

Stratum germinativum is also know as

Stratum basale

–Forms a strong bond between the epidermis and dermis

–Has epidermal ridges

–Has many basal cells (germinative cells)

Stratum basale

Lie next to dermal papillae in dermis

Epidermal ridges

Connective tissue and blood vessels that give nutrients to the epidermis and help control the temp. of skin

Dermal papillae

Stem cells that replace superficial keratinocytes

Basal cells (germinative cells)

Specialized structures of stratum basale

\-Tactile discs

\-Melanocytes

•Tactile (Merkel) cells with sensory nerve endings

•Found in hairless skin 

•Respond to touch

Tactile discs

**Contain the pigment melanin**

Melanocytes

Found between the epidermis and subcutaneous layer

Dermis

Anchors epidermal accessory structures (e.g., hair follicles and sweat glands)

Dermis

\-Outer papillary layer

\-Deeper reticular layer

2 components of Dermis

–Consists of areolar tissue

–Has capillaries, lymphatic vessels, and sensory neurons

–Named for dermal papillae that project between epidermal ridges

Papillary layer

Becomes inflamed in **dermatitis**

Papillary layer

Skin irritation

Dermatitis

•Caused by infection, radiation, mechanical irritation, or chemicals (e.g., poison ivy)

•May produce itching or pain

Dermatitis

–Consists of dense irregular connective tissue

–Contains __collagen__ and __elastic__ fibers

–The dermis contains all cells of connective tissue proper

Reticular layer

\-Collagen fibers

\-Elastic fibers

\-Fibers and water provide flexibility and resilience

Dermal strength and elasticity

•Very strong, resist stretching

•Easily bent or twisted

•Limit flexibility to prevent tissue damage

Collagen fibers

•Permit stretching and then recoil to original length

•Provide flexibility

Elastic fibers

Fibers and water provide flexibility and resilience

Skin turgor

\-Loss of skin turgor

\-Distortion of skin from pregnancy or weight gain

Skin damage

•Dehydration (reversible)

•Aging

•Hormones

•UV radiation

Loss of skin turgor is caused by

Excessive distortion of skin from pregnancy or weight gain may cause

Stretch marks

Tension lines are also known as

Cleavage lines

–Produced by parallel bundles of collagen and elastic fibers in the dermis

–Resist forces applied to the skin

–A cut made parallel to a tension line remains shut and heals well

\-A cut at a right angle pulls open and scars

Tension lines

\-Cutaneous plexus

\-Subpapillary plexus

\-Contusion

Dermal blood supply

Deep network of arteries along the reticular layer

Cutaneous plexus

•Network of small arteries in papillary layer

•Capillaries drain into small veins that lead to larger veins in subcutaneous layer

Subpapillary plexus

Caused by damage to blood vessels in dermis

Contusion (Bruise)

Innervation of skin is due to

Nerve fibers

•Control blood flow

•Adjust gland secretion rates

•Monitor sensory receptors

Nerve fibers in skin

Sensory receptors respond to

\-Light touch

\-Deep pressure and vibration

\-T**actile (Meissner) corpuscles**

\-In dermal papillae 

Light touch

**-Lamellar (Pacinian) corpuscles**

\-In reticular layer

Deep pressure and vibration

The subcutaneous layer is also known as

Hypodermis

–Lies deep to dermis

–Connected to reticular layer by connective tissue

–__Stabilizes__ position of the skin

–__**Primarily adipose tissue**__

Subcutaneous layer

–Large arteries and veins in the superficial region

–Site of **subcutaneous injections** using __**hypodermic needles**__

–Distribution of subcutaneous fat determined by sex hormones

Subcutaneous layer

\-Short needle is used to inject a drug into the tissue layer between the skin and the muscle

**Subcutaneous injections**

A hollow needle used to inject substances into the body or extract fluids from it

__**Hypodermic needles**__

Skin color is influenced by 2 pigments in the epidermis

\-Melanin

\-Carotene

–Red-yellow or brown-black pigment

–Produced by __**melanocytes**__

–Stored in intracellular vesicles (melanosomes)

–Protects skin from **ultraviolet** (**UV**) **radiation**

Melanin

•Transferred to keratinocytes

•Dark-skinned people have large and numerous quantities

Melanosomes

\-Small amounts are beneficial

\-Too much damages DNA which causes cancer

UV radiation

\

Melanocyte cell

\-Orange yellow pigment

\-Found in orange vegetables

Carotene

\-Accumulates in epidermal cells, deep dermis, and subcutaneous layer

\-Can be converted into vitamin A

Carotene

Vitamin A is required for

\-The maintaining of the epithelia

\-Synthesis of photoreceptor pigments in eye

\-Blood flow

\-Oxygenation

Influence and contribute to skin color

Hemoglobin is what color when bound to oxygen?

Bright red

Blood vessels dilate from heat

Skin reddens

Blood flow to skin decreases

Skin pales

Hemoglobin is what color when oxygen is released?

Dark red