The Integumentary System (Outer Covering)

•Skin (cutaneous membrane)•Subcutaneous tissue below the skin•Accessory Structures

Sweat glands and Sebaceous or oil glandsHairNailshorns

•One of the largest organs-2 square meters; 10-11 lbs. -Largest sense organ in the body

It takes several forms…

Plasma membrane in animal-like protists

has spines and spikes in starfishes

moist and rough in earthworms

hardened as the plastron of turtles

mantle that covers organs in mollusks

scaly armor of pangolin  (only mammal on the planet armored with keratin scales)

tough and leathery in cattle

Functions of the Integumentary System

• outermost covering• first line of defense against

pathogens• protection against UV

radiation and protection from predators

• protection against physical injury and insulation (hairs and feathers)

Functions of the Integumentary System

•defense- nails, antlers and horns•glands release toxins/foul odors as warning to enemies•scent glands used to find prospective mates, mark territorial boundaries•sweat glands act as thermoregulators

Functions of the Integumentary System

•sensation to adapt to environment•mammary glands nourish young/ pouches of marsupials for protecting/nursing young•webbed feet of ducks act as oars in swimming

•in frogs, skin is a respiratory organ

Layers Of The Skin

• Epidermis – outer– composed of stratified

squamous epithelium

• Dermis – inner– anchored to a

subcutaneous layer

Epidermis• Composed of stratified squamous epithelium• Avascular as it has no blood supply of its own• Oxygen and nutrients diffuse from the underlying

dermis• The epidermis is a keratinized stratified squamous

epithelium. Five structurally different layers can be identified.

Stratum BasaleStratum Basale• Deepest layer• Columnar cells capable of continued cell division.• Newly made cells get pushed to surface where

there is less blood supply and they begin to die.

Stratum spinosumStratum spinosum• Multiple layered arrangement of cuboidal

cells• Are spiny or prickly in appearance, due to

molecular bridges that connect them to other cells

Stratum granulosumStratum granulosum• 3-5 rows of flattened cells• Cytoplasm of cells contain granules• The granules are protein that transforming into

waterproofing protein keratin (process starts)keratin (process starts)• Cells begin to die

Stratum lucidumStratum lucidum• Present in only the thick skin of palms

of hands and soles of feet• 3-4 rows of flattened dead cells

(Transparent)• Process of keratin formation

continues here

Stratum corneumStratum corneum• Most superficial• 20-50 rows flattened dead cells• Cells are “sloughed off” by normal wear• Each cell contain keratin, protects skin from

water loss• When skin is exposed to water for long

periods of time the water in skin moves outward by osmosis and causes wrinkles in the skin

Skin Color- MelanocytesSkin Color- Melanocytes• Determined by cells in between the dividing cells

of the Stratum basale.• Secrete a dark colored pigment called melanin• Greater amount melanin the darker the skin• Regulated by DNA but can be altered by UV light,

prolonged exposure can increase the melanin secretion and darken the skin (Tanning)

• Function of Melanocytes- protection from UV light.

Skin Color - CaroteneSkin Color - Carotene• Pigment• Present in the Stratum corneum and dermis• Most present in people with Asian origin,

gives a yellow hue• Pinkish color of Caucasian people is

attributed to small amounts of melanin and carotene, influenced by blood in blood vessels

Dermis- OverviewDermis- Overview• Region of connective tissue, located deep

to the epidermis.• Scattered apart unlike the epidermis• Contains a large amount of collagen• Blood vessels extend through to the

stratum basale

Dermis- reticular regionDermis- reticular region• Deep to the papillary region and is much thicker• Composed of dense irregular connective tissue• Named for the collagenous, elastic and reticular

fibers • These fibers give the dermis, strength,

extensibility, and elasticity• Wrinkles occur because of a change in these

fibers• The accessory organs are located here.

Dermis- papillary regionDermis- papillary region• Composed of loose (areolar) connective tissue.• Named for finger like projections called papillae,

that extend into the epidermis.• Papillae provide the dermis with a bumpy surface

that strengths the connection between the dermis and the epidermis.

• In the palms, fingers, soles and toes they form contours in the skin called friction ridges.

• Friction ridges occur in patters that are genetically determined. (Fingerprints)

Malfunctioning Melanocytes

• Albinism – melanocytes completely fail to secrete melanin. Hair, skin, and iris are white.

• Vitiligo – loss of pigment in certain areas of the skin producing white patches.

•Freckles and moles are formed when melanin becomes concentrated in local areas.•Malignant melanoma – a cancerous change in a mole that may metastasize (spread) rapidly and is most difficult to treat. Exposure to sunlight increases risk.

Other Pigments in Skin• Carotene – a yellow pigment in skin usually hidden

by the effects of melanin. Asians have little melanin which allows the yellow to show more than other nationalities.

• Pinkish color – seen in fair-skinned persons because the vascular dermis is visible.

• Cyanosis – blue look to skin due to poorly oxygenated blood

• Blushing – caused by dilation of blood vessels• Pale by fright – caused by restriction of vessels

Response to Disease

• Jaundice – caused when bilirubin is deposited in skin because a diseased liver is unable to excrete this pigment

• Skin may appear bronzed due to the deposit of excess melanin when a person’s adrenal gland is functioning poorly.

• A bruise indicates that blood has escaped from the blood vessels and has clotted under the skin.

• Over eating carotene-rich vegetables such as carrots may cause skin to have a yellow tint.

Accessory Structures of the SkinHair• A characteristic feature of the human skin is the

apparent lack of hair on most of the body surface. This is actually not quite true. Most of the skin is haired although the hair in most areas is short, fine and only lightly pigmented.

• Truly hairless are only the palms of hands and soles of feet, the distal phalanges and sides of fingers and toes and parts of the external genitalia.

Accessory Structures of the Skin• In those parts of the skin which we perceive as

"hairy" we find terminal hairs. The free part of each hair is called the shaft.

• The root of each hair is anchored in a tubular invagination of the epidermis, the hair follicle, which extends down into the dermis and, usually, a short distance into the hypodermis.

•The hair that you groom daily is actually dead keratinized cells. •Each hair follicle has an associated bundle of smooth muscle, the arrector pili muscle. This muscle inserts with one end to the papillary layer of the dermis and with the other end to the dermal sheath of the hair follicle. This makes your hair stand up on its end.

Hair Color and Texture• Hair color is determined by the amount and type

of melanin present.• Melanocytes become less active with age. Gray

hair is a mixture of pigmented and non-pigmented hairs.

•Red hair results from a a modified type of melanin that contains iron.•The shape of the hair shaft determines texture.–Round shaft – straight hair–Oval shaft – wavy hair–Flat shafts – curly or kinky hairPerms use chemicals to flatten shafts and makes hair curly.Alopecia is the term for hair loss.

Accessory Structures of the Skin

• Nails– Plates of stratified squamous epithelial cells with

hard keratin– Protect distal ends of phalanges– Cells are keratinized in the nail root– Nail growth occurs in the lunula– Cuticle is a fold of stratum corneum on the proximal

end of nail

Exocrine Glands• or oil glands are simple branched areolar

glands. They secrete the sebum (seb = oil) an oily product.

-secreted into a hair follicle-it helps hair from becoming brittle- prevents excessive evaporation of water from the skin-keeps the skin soft and contains a

bactericidal agent that inhibits the growth of certain bacteria.

• Sebaceous glands are scattered all over the surface of the skin except in the palms, soles and the side of the feet.

•Vernix caseosa - white covering on fetus.•Blackhead•Pimple

Sebaceous glands

Exocrine Glands• Sweat glands or sudoriferous glands are simple coiled tubular

glands. They are divided into two principal types: eccrine and apocrine.

a. Apocrine glands are found mainly in the skin of the armpits, of the anogenital areas and of the areola of the breasts. b. Eccrine glands are the most common. Their secretory portion can be located in the dermis or in the hypodermis. They produce sweat, a watery mixture of salts, antibodies and metabolic wastes. Sweat prevents overheating of the body and thus helps regulate body temperature.

• Ceruminous glands (or ear wax glands) and mammary glands are modified apocrine sweat glands.