Skin

Integumentary system

•Composed of the skin and a number of skin derivatives (hair, nails, and glands).

•Largest organ in the body

•Accounts for 15 % of body’s weight


Functions:

1. Protectiona) Physical barrierb) Waterproofsc) Protects against sun’s

ultraviolet light – pigment in the skin called melanin


Functions:

2. Temperature regulation skin allows body to lose heat by

evaporation, convection, conduction, and sweat

3. Excretion excretes water, fatty substances

and ions


Functions:

4. Metabolism Vitamin D

5. Absorption if applied to the skin will

absorb Vitamin A, E, and K, steroid hormones released by glands


Functions:

6. CommunicationStimuli are received by skin

receptors which will communicate with the central nervous system


2 Layers of the Skin

Epidermis - Top layer of stratified squamous epithelium

Dermis - Layer underneath the epidermis made of connective tissue


Other parts of the skin:Epidermal – dermal junction is where the epidermis and dermis meet.

Hypodermis – is the layer of tissue under the dermis.

Epidermal-dermal junction


Two Layers of the Dermis:1. Papillary layer Upper dermis Has ridges that protrude up into

the epidermis called the dermal papillae

It is composed of loose connective tissue


Functions of Dermal papillae:•Increased blood flow to epidermis

•Increased surface area for dermis and epidermis to connect to each other to hold it strongly together


Functions of Dermal papillae:

•Contains sensory touch receptors

•Keeps skin from tearing

•Aids in gripping

•Gives you finger prints

Dermal papillae = finger prints


Layers of the dermis:1. Papillary layer

2.Reticular layer Lower dermis Further keeps from tearing Contains deep pressure sensors Contains sweat glands, lymph

vessels, smooth muscle, and hair follicles


Layers of the dermis:1. Papillary layer2. Reticular layer

Made of dense irregular connective tissue

Has criss-cross collagen fibers that give it a strong elastic network

This forms lines of cleavage or Langer’s Lines or Line of tension

Langer’s Lines

Note: Incisions parallel to the Langer’s Lines will heal faster and with less scarring.


HypodermisMade of adipose tissue to insulate and loose connective tissueFunctions to:

1.Conserve heat2.Connects skin to layer below3.Contains blood, lymph, base of hair follicles and sweat glands4. Stores lipids and cushions the body

Integumentary systemHypodermisFunctions to:

Hypodermis is 8% thicker in females than males

Integumentary systemHypodermis

Also known as the subcutaneous tissue

Where medical personal will give a subcutaneous injection because of the rich blood supply


Blister – a separation between the epidermis and the dermis

Burn - destruction of the different layers of the skin and the structures within the skin.

The severity of the burn is dependent upon the depth of the damage.


Three Classifications of burns:1. First degree or 1 is when there

has been some damage to the epidermis


Three Classifications of burns:

2. Second degree or 2 is when the epidermis is completely destroyed and there is some damage to the dermis



2. Second degree

Note: New epidermis will be regenerated from the cells surrounding the hair follicles. The hair follicles are lined with epidermal cells non-keratinized.



3. Third degree or 3 is when the epidermis and dermis are completely destroyed and there is

damage tothehypodermis.

Must have a skin graft to heal.


Layers of the epidermis:

composed of 4-5 layers depending on the region of skin being considered

Those layers in descending order are the stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum basale.

Layers of the epidermis

http://upload.wikimedia.org/wikipedia/commons/2/20/Skinlayers.png



1. Stratum basale also referred to as "basal cell layer”

is the deepest layer

Single layer of cuboidal/columnar cells that

undergoes rapid mitosis



Layers of the epidermis:1. Stratum basale

Cells migrate upward from here and begin to differentiate

Also known as the stratum germinativum



2. Stratum spinosum is several cell layers thick

Carries out mitosis as well

Some cells produce Keratin



3. Stratum granulosum flat cells (squamous) Layer where keratinization begins cells overproduce the protein

keratin and smother themselves cells in this layer are beginning to

die


Integumentary systemLayers of the epidermis:

4. Stratum lucidum found only in the thick skin of the

palms of the hand and soles of the feet

cells in this layer are dead

three to four strata (layers) thick

Helps protect against UV rays




5. Stratum corneum outermost layer of squamous cellscells filled with keratin dead cells that have migrated up from the stratum granulosum is true protective layer of skin is 25 – 30 cell layers thick


Layers of the epidermis:5. Stratum corneum

these dead cells slough off and are continuously replaced by new cells

the sloughing off of cells is known as desquamation



Layers of the epidermis:5. Stratum corneum

Just for your additional information:

In the human forearm, for example, about 1300 cells/cm2/hr are shed and commonly accumulate as house dust

Desquamation – term in Latin for scaling a fish


MelaninIs a brown pigment found in the skin and hairprimary determinant of skin colorproduced by melanocytes in the stratum basalethrough phagocytosis vesicles of melanin will enter cells of stratum basale and spinosum


Melanin

Note: The concentration of melanocytes in the skin of people is about the same, but some don’t produce as much melanin due to genetics.

UV light willtrigger melanin production


Melanin

Some individual animals and humans have very little or no melanin in their bodies, a condition known as albinism.

There are a number of different types of melanin giving different colors of skin (ex. Eumelanin most common) and hair plus other pigments.


Skin CancersThere are three main types of skin cancer:

1. Malignant melanoma • cancer cells are found in the melanocytes

• characterized by uncontrolled mitosis of melanocytes in the stratum basale


Skin CancersThere are three main types of skin cancer:

1. Malignant melanoma usually occurs in adults is the rarest, but worst form of skin

cancer has the highest death rate and is

responsible for 75 percent of all deaths from skin cancer

Usually in fair-skinned people


Skin CancersThere are three main types of skin cancer: 1. Malignant melanoma

2. Squamous cell carcinomauncontrolled mitosis of cell of the stratum spinosum

Not as dangerous as melanoma, but more dangerous than basal cell carcinoma


Skin CancersThere are three main types of skin cancer: 1. Malignant melanoma2. Squamous cell carcinoma

95% cure rate when properly treatedmay appear as nodules, or as red, scaly patches of skin

second most common skin cancer found in fair skinned individuals


Skin CancersThere are three main types of skin cancer: 1. Malignant melanoma2. Squamous cell carcinoma

3. Basal cell carcinomaUncontrolled mitosis of stratum basale layer cells

usually appears as a small, fleshy bump or nodule on the head, neck, or hands


Skin CancersThere are three main types of skin cancer: 1. Malignant melanoma2. Squamous cell carcinoma3. Basal cell carcinoma

easily detected and has an excellent successful treatment, when properly treated

is the most common skin cancer, but most treatablefound in fair-skinned individuals


Skin Cancers

Myth: Darker skinned people can’t get skin cancer.The darker the skin the less likely, but the more fatal.Usually melanoma the worst kind.

Usually late diagnosis or diagnosed incorrectly


Skin CancersMyth: Darker skinned people can’t get skin cancer.

almost always arise on the sole of the foot, palms, fingers, toes, under the nails and mucosal surfaces like in the mouth


Hair Follicle part of the skin that grows hair by packing old cells together

Cover entire body except eyelids, palms, soles, and lips

Attached to the hair follicle is a sebaceous gland (oil gland)


Hair FollicleThe thicker density of hair, the more sebaceous glands are found

•Also attached to the follicle is a tiny bundle of muscle fiber called the arrector pili that cause hair to stand up and a goose bump.


Hair Follicle has two parts based on location:

1. Shaft – protrudes from the skin2. Root – imbedded beneath the skin

At the base of the root is the hair bulb

Hair shaft

Hair root

Hair bulb

http://upload.wikimedia.org/wikipedia/commons/4/49/HairFollicle.png


Hair has no nerves

Composed of hair structure and hair follicle

Has a protective function


Hair Strand has three layers:1. Medulla

center layer that is 2-3 cell layers thick

Composed of soft keratin (less sulfur) and air


Hair Strand has three layers:

2. Cortex middle layerComposed of many cell layersIs hard keratin (contains more

sulfur)Makes up most of hair strandcontains melanin and maybe red

hair pigments

Cortex

2. Cortex

Hair color:•melanin is produced and through

phagocytosis it is incorporated into cells of cortex

•the more melanin the darker the hair color

•red hair also contains a red pigment, the more melanin the darker the red

•gray hair lacks melanin at all


Hair Strand has three layers:

3. Cuticle outer most layer of hard keratinOne cell layer thick, but cells

overlap like shingles on the roof


Hair Follicle layers:

1. Internal epithelial root sheath2. External epithelial root sheath

Two layers are covered by dermal root sheath

Hair bulb – expanded end of follicle

Inner sheathOuter sheath

DermalRoot sheath

http://en.wikipedia.org/wiki/Image:Gray944.png


Hair Follicle

Papilla – extends into the bulb and provides nutrients


Hair Follicle

Hair matrix Is at the base of the hair bulb Where cell mitosis/reproduction

occurs Cells are undifferentiated (all look

the same) Hair electrolysis damages the cell in

the matrix cells don’t reproduce


Hair Growth

Not all hair grows at the same rate

Eyelashes/brows vs. hair on head

Hair grow and then stops

Integumentary systemHair Growth

Three stages of hair growth:1. Anagen a growth phase when hair is growing

in length Eyelids – spend 30 days in this phase Head strand of hair spends 3 – 7 years

in this phase 90% of head hair is in this phase


Three stages of hair growth:1. Anagen

2. Catagen

Hair stops growing; transition phase

Club hair or replacement hair is formed

Head hair spend 2-3 weeks in this phase


Three stages of hair growth:1. Anagen 2. Catagen

3. Telogen Resting phase – 10% of hair on

head is in this phase head hair spends about 100 days

in this phase, eyelids 9 months Hair falls out You lose about 100 hairs on your

head per day


Nails

Functions:protectionsreinforce the finger/toe tips

http://en.wikipedia.org/wiki/Image:Toes.jpg

Integumentary systemNails

Parts of the NailoNail body – the part that is visibleoNail root – extends underneath the skinoNail matrix – part of nail root where cells reproduce. Cells differentiate and fill with keratinoLunula – upper part of the nail matrix, is thicker and appears white

http://www.lionden.com/nail-01.jpg


Parts of the Nail

oNail bed – thick epithelial tissue that the nail rest on

oFree edge – part that sticks out past the digit

oCuticle – fold of skin on proximal end


Grow constantly – no growth and resting phases

Grow at a rate of about 3 mm a month


Glands

Two types based on what they secrete:1. Sweat – water and electrolytes,

sweat

2. Sebaceous - oil

Integumentary systemGlands

Two types of sweat glands:A. Merocrine

Found all over skin, heaviest in soles of feet and palms of hands

Secrete a clear liquid to surface of skin

Are a merocrine gland


Two types of sweat glands:A. Merocrine

Regulates body temperature

Smaller and more numerous than apocrine sweat glands

Don’t secrete into hair follicle


Two types of sweat glands:

B. Apocrine glands Found armpits, groin and nipples Secrete a milky substance; odorous Actually merocrine glands, but were

once thought apocrine Secrete into hair follicle Found deeper in skin than merocrine


Two types based on what they secrete:1. Sweat – water and electrolytes, sweat

2. Sebaceous - oil

Sebaceous glands

Secrete an oily matter called sebum into hair folliclesPore = opening of hair follicle to allow oil to lubricate the skinHolocrine glandsOverproduction of sebum = acne

Skin

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