the integumentary system

The Integumentary system two major components 1. cutaneous membrane

A. epidermis /superficial epithelium B. dermis/underlying connective tissues. C. hypodermis/ Deep to the dermis

2. accessory structures hair, nails, exocrine glands, blood vessels,

sensory receptors for touch, pressure, temperature, and pain

functions of the skin Protection - organs against shocks, abrasion,

and chemical attack.(stratified squamous epithelium)

Excretion - salts, water, and organic wastes by glands.

Maintenance of temperature - insulation or evaporation

Synthesis of vitamin D3 - steroid converted to hormone calcitriol, important to normal calcium metabolism and membrane repair.

Storage - nutrients.lipids Detection - touch, pressure, pain, and

temperature

The Epidermis

There are four cell types found in the epidermis

Keratinocytes Produces a tough protein called keratin

Melanocytes Pigment cells located deep in the epidermis Produce melanin (skin color)

Merkel cells Sensory cells

Langerhans cells Fixed macrophages

The Epidermis

Thick and thin skin Thick skin

Found on palms and soles Made of five layers of cells Has stratum lucidum

Thin skin Found on the rest of the body Made of four layers of cells

LAYERS OF THE EPIDERMIS In order, from the basal lamina toward

the free surface, are the stratum germinativum(basale), stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum.

Stratum granulosumStratum spinosum

stratum germinativum/basale Dermal projections called dermal papillae

extend between adjacent epidermal ridges The contours of the skin surface follow the ridge

patterns - Fingerprints Large basal cells, or germinative stem cells,

dominate the stratum germinativum. Skin surfaces that lack hair also contain Merkel

cells that are sensitive to touch; when compressed, they release chemicals that stimulate sensory nerve endings.

The brown tones of skin result from the pigment cells called melanacytes, with cell processes extending into more superficial layers.

Stratum Spinosum Each time a stem cell divides, one of the

daughter cells is pushed from the stratum germinativum into the stratum spinosum,

The stratum spinosum consists of 8 to 10 layers of cells

Langerhans cells (fixed macrophages) present, stimulate a defense against (1) microorganisms that manage to penetrate the superficial layers of the epidermis and (2) superficial skin cancers.

Stratum Granulosum consists of three to five layers of keratinocytes

displaced from the stratum spinosum. By the time cells reach this layer, most have

stopped dividing & they begin making large amounts of keratin and keratohyalin

Keratin is a tough fibrous protein component of hair and nails.

Keratohyalin forms dense granules that dehydrate the cell and aggregate cross-linking of the keratin fibers.

The nuclei and other organelles disintegrate, and the cells die.

dehydration creates a tightly interlocked layer of cells of keratin fibers surrounded by keratohyalin.

Stratum Lucidum In the thick skin of the palms and

soles, a glassy stratum lucidum covers the stratum granulosum

The cells in the stratum lucidum are flattened, densely packed, and filled with keratin.

thick skin, on the palms and soles have five layers … lucidum is the 5th layer

Stratum Corneum At the exposed surface of both thick skin and

thin skin contains 15 to 30 layers of keratinized cells. remain tightly interconnected by desmosomes.

shed in large groups or sheets rather than individually.

15 to 30 days for a cell to move from the stratum germinativum to the stratum corneum.

The dead cells remain in the exposed stratum corneum layer for an additional two weeks before they are shed

insensible perspiration Water from interstitial fluids slowly evaporates into the surrounding air. You lose roughly 500 ml (about 1 pt) of water in this way each day.

Skin Color Three pigments contribute (1) melanin - amount and kind (yellow, reddish brown, or black) (2) carotene - orange-yellow found in carrots & orange, deep

yellow, or leafy green vegetables. (3) oxygen – amount bound to hemoglobin people who produce a lot of melanin have brown-toned skin. the crimson color of oxygen-rich hemoglobin gives the skin a rosy

color When hemoglobin is poorly oxygenated, the skin appear blue, a

condition called cyanosis Cyanosis is common during heart failure and severe breathing

disorders. skin color signals disease states: • Rubor, Redness, or erythema - embarrassment (blushing),

fever, hypertension, inflammation, or allergy. • Pallor, or blanching - emotional stress (fear, anger, and others),

Pale skin may also signify anemia, low blood pressure, or impaired blood flow into the area. • Jaundice, or a yellow- cast – liver disorder excess bile pigments

in the blood Bruises - sites where blood has escaped and has clotted in the

tissue spaces.(hematomas) unusual bruising may signify a deficiency of vitamin C or hemophilia

melanin yellow to brown to black, is produced by melanocytes sunlight stimulates the melanocytes to produce more

melanin (tanning) basale cells phagocytize the melanin & forms a protective

"umbrella" over nuclei (DNA) from ultraviolet radiation in sunlight.

Freckles and moles are where melanin is concentrated in one spot.

excessive sun eventually damages the skin. It causes the elastic fibers to clump, leading to leathery skin. It

also depresses the immune system. herpes simplex cold sore virus - are more likely to have

an eruption after sunbathing. Overexposure to the sun can also alter the DNA of skin

cells and in this way lead to skin cancer.

Dermis The dermis is your "hide." It is leather The dense fibrous connective tissue has two

major regions— papillary and reticular The papillary layer is the upper region. It is

uneven and has fingerlike projections called dermal papillae that create fingerprints

They contain capillaries, pain receptors (free nerve endings) and touch receptors called Meissner's corpuscles

The reticular layer is the deepest skin layer. It contains blood vessels, sweat and oil glands, and deep pressure receptors called Pacinian corpuscles & phagocytes That attack bacteria

As we age we produce less collagen and elastin and fat decreases (wrinkles)

hypodermis

Foundation that attaches to bone and muscle Supplies skin with blood vessels and nerves Consists of loose connective tissue Called subcutaneous tissue or superficial

fascia ½ of the body’s fat is in hypodermis Insulates, energy, padding Used to calculate total body fat

Hairs and Hair Follicles millions of hairs all over the body Guards the head, shields the eyes

(eyelashes) keep foreign particles out of the

respiratory tract (nose hairs) A hair is produced by a hair follicle root - part of the hair enclosed in the

follicle Shaft - projecting from the surface of

scalp or skin hair bulb matrix - the growth zone at the

inferior end of the follicle As the daughter cells are pushed away

from the growing region they become keratinized and die.

medulla - a central core surrounded by a bulky cortex layer

cuticle - single layer of cells overlap like roof shingles most heavily keratinized region

pigment is made by melanocytes in hair bulb

dermal sheath - dermal connective tissue provides blood to hair bulb.

arrector pili - smooth muscle connecting hair follicle to dermal tissue (goose bumps)

glands of the SkinCutaneous Glands (all are exocrine glands)

Exocrine Glands - release secretions to surface via ductstwo groups: 1. sebaceous glands and 2. sweat glands. Both formed by stratum basale & push into dermis.

1. Sebaceous (Oil) Glands – - all over except on the palms of hands and feet. Their ducts usually empty into a hair follicle but some open directly onto the skin surface.(lips,

eyelids, genitalia) sebum (seb = grease), mixture of oily substances

and fragmented cells lubricate skin & kill bacteria, male sex hormones produced in both sexes during

adolescence increase sebum Whitehead - a sebaceous gland's duct becomes

blocked by sebum blackhead - the accumulated material oxidizes,

dries and darkens Acne - active infection of the sebaceous glands

can be mild or extremely severe, leading to permanent scarring.

Seborrhea ("cradle cap“) in infants – overactivity of the sebaceous glands on the scalp starts as pink, raised lesions that gradually form a yellow to

brown crust that sloughs off as oily dandruff.

2. Sweat Glands (sudoriferous= sweat)— more than 2.5 million per person. There are two types merocrine/eccrine and apocrine. Merocrine/eccrine glands - more numerous all over

the body. produce sweat, primarily water plus salts, vitamin C, traces of metabolic wastes (ammonia, urea, uric acid), and lactic acid (attracts mosquitoes).

Sweat is acidic (pH from 4 to 6), and inhibits growth of bacteria, which are always present on the skin surface.

Apocrine glands - confined to axillary and genital areas

larger than eccrine glands, their ducts empty into hair follicles.

Their secretion contains fatty acids, proteins, salt & water may have a milky or yellowish color. odorless, but when

bacteria that live on skin use its proteins and fats it has an unpleasant odor.

Apocrine glands begin to function during puberty under the influence of androgens. Their precise function is not yet known, but they are activated

by nerve fibers during pain and stress and during sexual foreplay.

nails

A scalelike modification of the epidermis free edge body (visible attached portion) root (embedded in the skin) Nailfolds - overlapped skin folds cuticle - thick proximal nail fold nail bed - stratum basale beneath the nail nail matrix - thickened proximal area is responsible for nail growth produced by the matrix nails become keratinized and die

(nonliving) Nails look pink because of the rich blood supply in the underlying

dermis Lunula - white crescent over nail matrix

eyelopmental Aspects of Skin l/and Body Membranes During the fifth and sixth months of fetal develop ment, the soon-to-be-born infant is covered with a downy type of hair

called lanugo (lah-noo'go), but this hairy cloak has usually been shed by birth. When a baby is born, its skin is covered with vernix caseosa (ver'niks kah-se-o'sah). This white, cheesy-looking substance, produced by the seba ceous glands, protects the baby's skin while it is floating in its water-filled sac inside the mother. The newborn's skin is very thin, and blood vessels can easily be seen through it. Commonly, there are accumulations in the sebaceous glands, which ap pear as small white spots called milia (mil'e-ah), on the baby's nose and forehead. These normally disappear by the third week after birth. As the baby grows, its skin becomes thicker and moist, and more subcutaneous tat is deposited.

During adolescence, the skin and hair become ,,more oily as sebaceous glands are activated, and acne may appear. Acne usually subsides in early adulthood, and the skin reaches its optimal ap pearance when we are in our 20s and 30s. Then visible changes in the skin begin to appear as it is continually assaulted by abrasion, chemicals, wind, sun, and other irritants and as its pores become clogged with air pollutants and bacteria. As a re sult, pimples, scales, and various kinds of der matitis (der"mah-ti'tis), or skin inflammation, be come more common.

During old age, the amount of subcutaneous tissue decreases, leading to the intolerance to cold so common in the elderly. The skin also becomes drier (because of decreased oil production and de clining numbers of collagen fibers) and, as a result, it may become itchy and bothersome. Thinning of the skin, another result of the aging process, makes it more susceptible to bruising and other types of injuries. The decreasing elasticity of the skin, along with the loss of subcutaneous fat, allows bags to form under our eyes, and our jowls begin to sag. This loss of elasticity is speeded up by sunlight, so one of the best things you can do for your skin is to shield it from the sun by wearing sunscreens and protective clothing. In doing so, you will also be decreasing the chance of skin cancer. Although there is no way to avoid the aging of the skin, good nutrition, plenty of fluids, and cleanliness help delay the process.

Hair loses its luster as we age, and by age 50 the number of hair follicles has dropped by one-third and continues to decline, resulting in hair thinning and some degree of baldness, or alopecia (al"o-pe'she-ah), in most people. Many men become ob viously bald as they age, a phenomenon called male pattern baldness. A bald man is not really hairless— he does have hairs in the bald area. But because those hair follicles have begun to degenerate, the hairs are colorless and very tiny (and may not even emerge from the follicle). Such hairs are called vellus (veil = wool) hairs. Another phenomenon of aging is graying hair. Like balding, this is usually genetically controlled by a "delayed-action" gene. Once the gene takes effect, the amount of melanin deposited in the hair decreases or becomes entirely absent, which results in gray-to-white hair.

S Certain events can cause hair to gray or fall out prematurely. For example, many people have claimed that they turned gray nearly overnight be cause of some emotional crisis in their life. In addi tion, we know that anxiety, protein-deficient diets, therapy with certain chemicals (chemotherapy), ra diation, excessive vitamin A, and certain fungal dis eases (ringworm) can cause both graying and hair loss. However, when the cause of these conditions is not genetic, hair loss is usually not permanent. •