7/28/2019 The Skin Integument System

1/4

1

NOTES IN BIOLOGY Prepared by: N.R. Bautista

THE SKIN or INTEGUMENT SYSTEM

Structure of the Skin.

The skin has 3 distinct regions.The (1) epidermis is an externallayers composed of dead keratinizedcells. Underneath this is the (2)dermis, which is mostly dense,actively dividing squamousconnective tissues that cushion thebody from everyday stress andstrains. Beneath this is the (3)hypodermis or subcutaneous layer, atissue that anchors the skin to theflesh below and yet allows it somefreedom of movement.

Fats stored in the hypodermisinsulates the body against cold andprotects some organs, such as theuterus, against injury.

The skin is the largest organ in the body, about 12-15% of body weight, with a surface area of 1-2 meters. The skin is continuous with, but structurally distinct from mucous membranes that linethe mouth, anus, urethra, and vagina. Two distinct layers occur in the skin: the dermis andepidermis. The basic cell type of the epidermis is the keratinocyte, which contain keratin, afibrous protein. Basal cells are the innermost layer of the epidermis. Melanocytes produce the

pigment melanin, and are also in the inner layer of the epidermis. The dermis, or a layerbeneath it, contains nerve endings, sensory receptors, capillaries, and elastic fibers.

Skin structure varies considerably. Most of your skin is as thin as a paper towel, it thickens onlyon the soles of your feet, palms of the hand and in other regions subjected to pounding orabrasion. Some fishes have hard dermal scales, others have bare skin coated with slimymucus. The scales, feathers, hair, beak, hooves, horns, claws, nails and quills of differentvertebrates are all produced by cell differentiation in epidermal tissues.

Each day, millions of dead cells at your skins surface are worn off by abrasion. Fortunately, youget new top layers of skin every thirty-five to forty-five days. In the process of keratinization,cells in mid-epidermal regions die and become dead bags with a lot of keratin ( a water

insoluble protein ) inside. Rapid cell divisions below them push the bags toward the skinsurface. The rapid divisions contribute to skins capacity to mend itself after abrasion, cuts, orburns. Keratinized cells at the surface form a barrier against dehydration, bacteria, and manytoxic substances.

Three pigments melanin, hemoglobin, and carotene contribute to skin color. Cells in deepepidermal layers produce melanin, a brownish-black pigment that protects cells againstultraviolet radiation. Suntanned skin has increased melanin concentrations in the epidermis.

7/28/2019 The Skin Integument System

2/4

2

Pale skin has very little melanin. Its pinkishcast results from hemoglobin, a pigmentgiving red blood cells their color. Redshows through thin-walled blood vesselsand through the epidermis, both of whichare transparent. Carotene, a yellow-orange

pigment, occurs in the uppermost layers ofthe epidermis, and is abundant in the skinof most Asians.

The skin is the largest organ of the body. Itincludes the skin and all structures derivedfrom it or associated with it. The skin evenmaintains its shape in spite of repeatedstretching and washings.

Function of the Skin:1. Covers and protects the body from

mechanical injury infection (abrasion andpuncture). Thick epidermal layers (callus)form at areas most often subjected tostress. Pigmentation in skin protects theinner tissues from ultraviolet rays from the

Sun.2. Protects the body from bacterial infection / even kills some bacteria on contact .3. Protects the inner tissues from drying. Aided by the oil glands, the skin is nearlywaterproof. Little water passes through it, except outward through the pores.4. As sense organ, the skin serves as location of the nerve receptors that respond to touch,pressure, pain and temperature.5. It serves as a supplementary excretory organ. The skin helps the kidney in the excretion of

excess water, salts and some urea (body wastes) in the form of sweat.6. Controls the loss of body heat through the evaporation of perspiration. At the bodysurface, as the sweat evaporates, heat is withdrawn from the outer tissues. In elephants, heatfrom arteries is released in the ear.7. Site where vitamin D is made upon exposure to sunlight.8. Produces skin secretions like pheromones (makes the animal, usually males or females to besexually attractive / beautiful or influence the behavior of other members); also repugnantsubstances.9. For some animals particularly amphibians (e.g. salamanders), the skin becomes anaccessory breathing or respiratory apparatus.10. Serve as camouflage (skin pigmentation) to hide from predators (e.g. octopus, chameleonand some tree frogs).

11. Conserve body heat through the use of hairs, feathers or thick layer of fat.12. Serve as excretory system removes (through sweat) excess water, salt and waste fromblood).13. Erector pili muscles connected to hair shafts makes hair (or feathers in birds) stand up,creating goose bumps. For animals, it help in making some animals look bigger than actual.

Parts of the Skin:1. Epidermis - is the outermost layer, made up of many layers of dead, flattened epithelialcells on its outer part, and more active and larger germinative layer of cells in the inner part.

7/28/2019 The Skin Integument System

3/4

3

2. Dermis - "true skin" is the layer of the skin beneath the epidermis, made entirely of livingcells. It is a thick active layer, compsed of tough, fibrous connective tissues supplied withmany blood vessels, lymph vessels, and nerve endings.

3. Subcutaneous tissue or Hypodermis - lies immediately below the dermis; composed of

loose connective tissue and is the principal storage site of fat. It also contains tiny bloodcapillaries, and nerve endings.

Terms to Remember:1. Keratin - water-insoluble protein which compose the waxy secretion that covers theepidermis, making it water-resistant.

2. Melanin - the pigment which gives the skin its color.

3. Freckles - localized collection of pigment granules in deeper parts of the epidermis.

4. Burns - injured by heat, caustic chemicals or electricity

a. First Degree - this usually reddens the skin;b. Second Degree - this usually reddens the skin and produce blisters;c. Third Degree - this usually destroys the skin, creating a wound.

Other Diseases or Abnormalities in skin:

Corns and calluses (Kalyo) thick epidermal in regions of the palm or sole of the feet inresponse to abrasion;

Acne (Pimples) caused by bacterial infection of oil / sebaceous glands

Dandruff (Balakubak) flaking out of epidermal cels in scalp, either due to allergy toshampoo or other reasons.

Black Heads excessive accumulation of sebum, secreted by the sebaceous gland thatare filling the pore of the skin. It is found on the nose.

"An-An" (Tinea versicolor) a white patch discoloration of the skin caused by a fungus(yeast), Pityrosporon ovlae or Malassezia furfur and M. glubosa;which causes itchiness.

Ringworm of the Scalp (Tinea capitis) - caused by 2 organisms; (a) Microsporon canisfrom dogs and cats (Tagalog = "galis"); contagious, first start as a pimple-like growth,and spreads out and leaves scaly patches or red rings in skin, with boggy swellings andbroken hairs; disease is worsened by scratching the itchy region with long fingernails,which causes wounds and irritation.

Ringworm of Groin or Jockey Itch -- (Tagalog = "Halas") also from infected animals,humans or from soil; first appears as a ring-like lesions in groin area and graduallyenlarges peripherally, ring usually contains fluids or pus, when healed, usually leaves

ring-like patches on skin, usually itchy. Ringworm of the Foot (Athlete's foot) (Tagalog = Alipunga) scientifically called "Tinea

pedis", which is a fungal infection of the skin of the foot caused the by

Ringworm of the Hand (Tinea manus or manuum), fungal infection of the skin of thehand. It is typically more aggressive than tinea pedis but similar in look. Itching, burning,cracking, and scaling are observable and may be transmitted sexually or otherwise,whether or not symptoms are present.

7/28/2019 The Skin Integument System

4/4

4

Boil (Tagalog: Pigsa), also called a furuncle, is a deep folliculitis, infection of the hairfollicle. It is most commonly caused by infection by the bacterium Staphylococcusaureus, resulting in a painful swollen area on the skin caused by an accumulation of pusand dead tissue

Skin cancer uncontrolled cell growth coming from the skin, usually Caucasians are themost susceptible, as the disease arise from too much exposure to UV radiation. Some

types are deadly. Sun burn reddening of skin exposed to too much sunlight.

.----------

PimplesAllergies and ItchingDermatitis, Poison Ivy, Hives, Eczema, Itching, Anal Pruritus, Skin Irritation due to weather,Chapping, Frostbite, Chilblain, Chafing,Pricky Heat (Bungang Araw),Calluses and CormsFungus infections -- Ringworm, Athlete's Foot

ScabiesBacterial Infection -- Boils, Carbuncles, ImpetigoBarber's itch - fungal infection of the scalp caused by ____. Also called dundruff?Erysipelas

Viral Infection -- Cold sores, shingles, warts, Sebaceous cyst, Acne,PsoriasisPigment Disorders and Birthmarks -- Freckles, Liverspots, Moles, Vitiligo, BirthmarksCancer - uncontrolled cell division of skin cells.

Athlete's foot, bedsores, birthmarksBurns

Allulitis, chiken pox, exzemaEhlers-Danlos SyndromeEpidermalysis Bullosa, Gangrene, Hidradenitis suppurativa, Hyperhidrosis Itchthyosis, JockyItch, Keratosis Pilaris, Leprosy, Penaphigus vulgaris, Pityriasis rosea, Pioson ivy, Oak, sumar,Porphyria, Psoriasis, Rosaceae, Scleroderma, Shingles, Skin Cancer, Vitiligo, Pseudofolliculitis,Barbae