4The Integumentary System Integument is skinSkin and its appendages make up the integumentary systemA fatty layer (hypodermis) lies deep to itTwo distinct regionsEpidermisDermis
5Functions of skin Protection Synthesizes vitamin D with UV Cushions and insulates and is waterproofProtects from chemicals, heat, cold, bacteriaScreens UVSynthesizes vitamin D with UVRegulates body heatPrevents unnecessary water lossSensory reception (nerve endings)The melanocytes contain melanin, which absorbs UV radiation, and also distributes the pigment to neighboring cells. Skin exposed to sunlight becomes wrinkled and creased. Changes seem to be due to disruption of collagen and elastin in dermis, and loss of fibroblasts which make new proteins.
6Epidermis Avascular as it has no blood supply of its own Oxygen and nutrients diffuse from the underlying dermisThe epidermis is a keratinized stratified squamous epithelium. Oxygen and nutrients diffuse from the underlying dermis. Five structurally different layers can be identified:
7Layers (from deep to superficial) Stratum basale or germinativum – stem cells or mitotic cells. Cells here are constantly dividing and as new cells form, older ones are pushed toward the skin surface.Stratum spinosum – Consist of prickle cells that interlock to support the skin.
9Stratum granulosum - This layer initiates Keratinization Stratum granulosum - This layer initiates Keratinization. This process starts the death of epithelial cells ( cells that make up the skin)Stratum lucidum- This layer is made up of translucent cells. This thick layer appears only in frequently used areas used areas such as the palms of the hands and the soles of the feet.Stratum corneum – horny layer (cells dead, many layers thick). The cells here are filled with keratin which keeps the skin elastic and protects underlying cells from drying out.
10Four types of cellsKeratinocytes – deepest, produce keratin (tough fibrous protein)Melanocytes - make dark skin pigment melaninMerkel cells – associated with sensory nerve endings for touch sensationsLangerhans cells – macrophage-like dendritic cells, which helps the immune system.
11The stratum basaleis the deepest layer of the epidermis (closest to the dermis).It is found close to the dermal blood supply.It consists of a single layer of columnar or cuboidal cells which rest on the basement membrane.Basal cells are the stem cells of the epidermis.Their mitotic activity replenishes the cells in more superficial layers as these are eventually shed from the epidermis.
12stratum corneumcells are keratinized and form a layer that is about 30 cells thick.Closest to the surface of the epidermis,Cells are constantly shed from this part of the stratum corneum. This layer makes up three fourths of the epidermal thickness. The protection of the body by the epidermis is due to the functional features of the stratum corneum.
13The renewal of the epidermis takes about 3 to 4 weeks in humans as millions of cells are produced daily.Cells die as they are pushed away from the source of nourishment. Cells undergo keratinization as a tough protein, keratin, is deposited within the cell.Keratin hardens and flattens the cells as they move outward and it waterproofs the skin.
14Skin color Three skin pigments Melanin: the most important Carotene: from carrots and yellow veggiesHemoglobin: the pink of light skin
15Other Pigments in SkinCarotene – 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.
16Cyanosis – blue look to skin due to poorly oxygenated blood Blushing – caused by dilation of blood vesselsPale by fright – caused by constriction of vessels
17Response to DiseaseJaundice – caused when Bilirubin is deposited in skin because a diseased liver is unable to excrete this pigmentA bruise indicates that blood has escaped from the blood vessels and has clotted under the skin.Malignant melanoma – a cancerous change in a mole that may metastasize (spread) rapidly and is most difficult to treat. Exposure to sunlight increases risk.Skin may appear bronzed due to the deposit of excess melanin when a person’s adrenal gland is functioning poorly.
18DermisThe dermis, or corium, consists of dense fibrous connective tissue with numerous collagenous and elastic fibers.The dermis is much thicker than the epidermis. In thick skin, dermal papillae create a very irregular border between epidermis and dermis.Blood vessels, nervous tissue, some muscle tissue, certain glands, hair and nails are found in the dermis.
19Strong, flexible connective tissue: your “hide” Fiber types: collagen, elastic, reticularCritical role in temperature regulation (the vessels)Nerve endings allow us to sense pain, temperature, pressure, and touch.
20Divisions of the Dermis The Papillary Layer: has loose connective tissueThis layer lies directly beneath the epidermis and connects to it via Papillae ( fingerlike projections).Some papillae contain capillaries that nourish the epidermis; others contain Meissner’s Corpuscles( touch receptors).A double row of papillae in finger pads produces the ridged fingerprints on finger tips.2. The Reticular layer which has dense connective tissueThese layers are so closely connected that they are difficult to differentiate.
23Exocrine GlandsSebaceous glands or oil glands are simple branched areolar glands. They secrete the sebum (seb = oil) an oily product.Sebum is usually secreted into a hair follicle. Sebum is a natural skin cream: 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.
24Sebaceous glands are scattered all over the surface of the skin except in the palms, soles and the side of the feet.When the sebaceous glands oversecretes and bacteria acts on the secretions, a blackhead or pimple results.
25SweAT glandsSweat glands or sudoriferous glands are simple coiled tubular glands. They are divided into two principal types: eccrine and apocrine.Apocrine glands are found mainly in the skin of the armpits, of the anogenital areas and of the areola of the breasts. Their secretory portion can be located in the dermis or in the hypodermis. Their excretory ducts open into hair follicles. Their secretion is more viscous than that of the eccrine glands. They start secreting at puberty and may be analogous to the sexual scent glands of other animals.
26Eccrine 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.
27Accessory Structures of the Skin HairA 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.
28Hair development begins in the third fetal month ( 17th - 20th week) . By the fifth month of fetal life( 25th – 28th week), Lanugo ( fetal hair) covers the fetus.At 5 months after birth, lanugo disappears from every area except the scalp and eyebrows where coarser hair replaces it.Vellus ( a film of delicate hair) eventually covers the rest of the body.Terminal hair is the early coarse scalp and eyebrow hair and later armpit and genital hair that grow during puberty.
29Accessory 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.
30The 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.
31Hair Color and TextureHair color is determined by the amount and type of melanin present.Melanocytes become less active with age (and hydrogen peroxide is produced by hair follicle neutralized by an enzyme). Gray hair is a mixture of pigmented and non-pigmented hairs.Red hair results from a modified type of melanin that contains iron.
32The shape of the hair shaft determines texture. Round shaft – straight hairOval shaft – wavy hairFlat shafts – curly or kinky hairAlopecia is the term for hair loss.Functions of hairWarmth – less in man than other mammalsSense light touch of the skinProtection - scalp
35Accessory Structures of the Skin NailsPlates of stratified squamous epithelial cells with hard keratinProtect distal ends of phalangesCells are keratinized in the nail rootNail growth occurs in the lunulaCuticle is a fold of stratum corneum on the proximal end of nail
37Disorders of the integumentary system BurnsThreat to lifeCatastrophic loss of body fluidsDehydration and fatal circulatory shockInfectionTypesFirst degree – epidermis: redness (e.g. sunburn)Second degree – epidermis and upper dermis: blisterThird degree - full thicknessInfectionsFluid lossHeat loss
38Burns First-degree (epidermis only; redness) Second-degree (epidermis and dermis,with blistering)Third-degree(full thickness, destroying epidermis, dermis, often part of hypodermis)
39Critical burns Over 10% of the body has third- degree burns Estimate by “rule of 9’s”Over 10% of the body has third- degree burns25 % of the body has second- degree burnsThird-degree burns on face, hands, or feet
40How Skin HealsWhen your skin gets cut, your body springs into action to heal the wound. First, the body works to limit blood loss by reducing the amount of blood flowing to the wounded area.For wound healing to occur, certain factors are needed. A good nutritional status which includes adequate blood supply to provide oxygen and nutrients and also remove wastes.
41Primary healing ( wound Healing by primary intention) This method applies when there is minimal tissue destruction and when the wound edges are apposed. There are three (3) stages which overlap.InflammationProliferationMaturationInflammation:The cut surface becomes inflammed and cell debris and blood clot fills the gap between the cut surfaces in the first few hours. Phagocytes ( neutrophils, macrophages) and fibroblasts migrate into the blood clot.The phagocytes begin to remove the clot and cell debris.
42ProliferationEpithelial cells proliferate across the wound, through the clot. The epidermis meets and grows upwards until full thickness is restored. The clot above the new tissue becomes the scab and is shed after days. Granulation tissue and collagen is secreted by the fibroblasts. This invades the clot, restoring blood supply to the wound. Phagocytes remove the debris and bacteria.
43MaturationThe granulation tissue ( type 3 collagen) is then replaced by fibrous scar tissue.The collagen fibers are then rearranged and wound strength increases.The scar becomes less vascular, appearing after a few months as a fine line.
45Wound Healing by Secondary Intention This method follows destruction of a large amount of tissue or when the wound edges can’t be apposed. E.g. large ulcers The stages for wound healing are the same in primary healing. Inflammation Inflammation develops on the surface of healthy tissue and the necrotic tissue sloughs off due mainly to the action of phagocytes. Proliferation Granulation tissue is deposited at the base of the cavity and grows upwards towards the surface. Phagocytes prevent infection by ingesting bacteria. Granulation tissue can’t contract like normal skin tissue. When granulation tissue reaches the level of the dermis, epithelial cells at the edges proliferate and grow towards the center.
46maturationThis occurs by fibrosis, in which scar tissue replaces the granulation tissue. This occurs over several months until the full thickness of the skin is restored. Wound contraction is caused by increased numbers of myofibroblasts. Scar tissue is shiny and doesn’t contain sweat glands, hair follicles or sebaceous glands.
47Temperature regulation In hot conditionsSweat glands under the skin secrete sweat (a fluid containing mostly water with some dissolved ions) which travels up the sweat duct, through the sweat pore and onto the surface of the skin. This causes heat loss via evaporative cooling however, a lot of essential water is lost.
48The hairs on the skin lie flat, preventing heat from being trapped by the layer of still air between the hairs. This is caused by tiny muscles under the surface of the skin called arector pili muscles relaxing so that their attached hair follicles are not erect. These flat hairs increase the flow of air next to the skin increasing heat loss by radiation. When environmental temperature is above core body temperature, sweating is the only physiological way for humans to lose heat.
49Arterioles Vasodilation occurs, this is the process of relaxation of smooth muscle in arteriole walls allowing increased blood flow through the artery. This redirects blood into the superficial capillaries in the skin increasing heat loss.
50Cold TemperaturesIf the skin temperature drops below 37°C a variety of responses are initiated to conserve the heat in the body and to increase heat production. These includeVasoconstriction to decrease the flow of heat to the skin.Cessation of sweating.Shivering to increase heat production in the muscles.In lower animals, the erection of the hairs and fur to increase insulation.
53The major types of primary lesions are: Macule: A small, circular, flat spot less than 0.4 in (1 cm) in diameter. The color of a macule is not the same as that of nearby skin.
54Vesicle: A raised lesion less than 0 Vesicle: A raised lesion less than 0.2 in (5 mm) across and filled with a clear fluid. Vesicles that are more than 0.2 in (5 mm) across are called bullae or blisters.Pustule: A raised lesion filled with pus. A pustule is usually the result of an infection, such as acne, impetigo, or boils.
55pAPULEA solid, raised lesion less than 0.4 in (1 cm) across. A patch of closely grouped papules more than 0.4 in (1 cm) across is called a plaque. Papules and plaques can be rough in texture and red, pink, or brown in color. Papules are associated with such conditions as warts, seborrheic keratosis.
56nODULEA solid lesion that has distinct edges and that is usually more deeply rooted than a papule. It can be felt as a hard mass distinct from the tissue surrounding it. A nodule more than 0.8 in (2 cm) in diameter is called a tumor. Ex: acne vulgaris
57wHEALA skin elevation caused by swelling that can be itchy and usually disappears soon after erupting. Wheals are generally associated with an allergic reaction, such as to a drug or an insect bite.
58Scale. A dry, horny build-up of dead skin cells that often flakes off the surface of the skin. Diseases that promote scale include fungal infections, psoriasis.Crust. A dried collection of blood, serum, or pus. Also called a scab, a crust is often part of the normal healing process of many infectious lesions.
59ErosionLesion that involves loss of the epidermis.
60UlcerLesion that involves loss of the upper portion of the skin (epidermis) and part of the lower portion (dermis).An ulcer that appears as a deep crack that extends to the dermis is called a fissure.
61Fun Facts House dust is mainly skin flakes! If you laid out all your skin on a flat surface, it would have an area of about 2 square meters.Skin weighs about 2.5 kilograms - the largest organ in the body.What hurts if you pull it, but doesn't hurt if you cut it? Your hair, of course!Skin is elastic - it springs back into shape when stretched. Some medicines (estrogen, nicotine) can pass through the skin, but others cannot (insulin). Why is that? Because only fat-soluble substances can enter the skin, not water-soluble ones.Your hair stands on end and you develop 'goose bumps' because there are tiny muscles attached to the hair follicles and they contract when you are frightened or cold.