Integumentary System

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Skin (cutaneous membrane) Subcutaneous tissue ≈below the skin Functions of the skin Epidermis and dermis Hypodermis Thick and thin skin Skin color Skin markings Accessory Structures Hair and nails Cutaneous glands; (Sweat glands, Sebaceous or oil glands, Mammary glands)

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Slide 1:

The Integumentary System By DR. ABDUL RASHEED CHUGHATTA M.B.B.S. , DCPS-H.C.S.M (MPH)

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The Integumentary System ANATOMY Of

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Includes: Skin ( cutaneous membrane) Subcutaneous tissue ≈below the skin Functions of the skin Epidermis and dermis Hypodermis Thick and thin skin Skin color Skin markings Accessory Structures Hair and nails Cutaneous glands; ( Sweat glands, Sebaceous or oil glands, Mammary glands) The Integumentary System

Overview:

Overview Most visible system and more attention paid to this organ system Inspection of the skin, hair, and nails is significant part of a physical exam Skin is the most vulnerable organ exposed to radiation, trauma, infection, and injurious chemicals Receives more medical treatment than any other organ system. The Integumentary System

Fun 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. The Integumentary System Fun Facts

Goose Bumps:

Goose Bumps 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. 'goose bumps‘ are due to depression of skin, as tiny muscles tighten and raise the hairs.

General Considerations:

The body’s largest and heaviest organ; covers area of 1.5 -2.0 m 2 15 % of body weight Consists of two layers: Epidermis – stratified squamous epithelium Dermis – connective tissue layer Hypodermis – another connective tissue layer below the dermis Most skin is 1 – 2 mm thick Ranges from 0.5 mm on eyelids to 6 mm between shoulder blades. Skin and Subcutaneous Tissue General Considerations

General Considerations:

Thick skin – on palms and soles, and corresponding surfaces on fingers and toes has sweat glands, but no hair follicles or sebaceous (oil) glands Epidermis 0.5 mm thick Thin skin – covers rest of the body Epidermis about 0.1 mm thick possesses hair follicles, sebaceous glands and sweat glands Skin and Subcutaneous Tissue General Considerations

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Epidermis develops from ectodermal germ layer, Dermis develops from mesodermal germ layer, At 8 weeks, fetal “skin” is simple cuboidal epithelium, At 10 weeks, nails begin to form, but do not reach the fingertip until the 9th month, By 11 weeks, dermis forms from mesoderm, By 16 Weeks, all layers of the epidermis are present, In 4 th and 5 th month, oil and sweat glands form, By 6 th month , delicate fetal hair ( lanugo ) has formed, Vernix caseosa : Slippery coating of oil and sloughed off skin present at birth. Development of the Skin

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Major derivatives of the embryonic germ layers Dermis of ventral body region Epidermis, hair, nails, glands of skin Dermatome, Dermis of dorsal body region

Physiology of the Skin:

Physiology of the Skin

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Physiology of the Skin Protection as physical barrier Regulation of body temperature Sensory receptors Excretion and absorption Synthesis of vitamin-D Psychological and social functions

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Physical, chemical and biological barrier; Intact skin (tight cell junctions) prevents the entry of micro-organisms into the body. The epidermis provides a barrier to fluid loss from the body (this protective function is impaired in patients with burns). Antimicrobial proteins are produced by the epidermis - they act by piercing holes in the outer membranes of micro-organisms Lipids released retard evaporation Physiology of the Skin « Protection »

Physiology of the Skin:

The skin provides a barrier to ultra-violet light . The melanocytes contain melanin, which absorbs UV radiation, and also distribute 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. Langerhans cells alert immune system. « Protection – Contd ……. » Physiology of the Skin

«Thermoregulation»:

Thermoreceptors: Vasoconstriction / vasodilation Releasing of sweat onto the skin; perspiration, & its evaporation lowers body temperature, Adjusting flow of blood to the body surface; in moderate exercise, more blood brought to surface helps lower temperature, with extreme exercise, blood is shunted to muscles and body temperature rises, Shivering and constriction of surface vessels; raise internal body temperature as needed. « Thermoregulation » Physiology of the Skin

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Most extensive sense organ: The integumentary system is well-supplied with receptors for touch, pain, temperature, vibration and pressure, Sensory information is relayed to the central nervous system via sensory nerves, Social interactions are influenced by facial expressions, blushing, touching, etc. Physiology of the Skin « Cutaneous Sensations »

«Excretion & Absorption»:

Skin can excrete water, salt, CO2 and small amounts of waste products such as ammonia and urea . 400 ml of water evaporates from it daily Transdermal absorption: 1-2 % oxygen absorption by diffusion through skin, Amino acids & steroids diffusing through skin attract mosquitoes, Physiology of the Skin « Excretion & Absorption »

«Excretion & Absorption – Contd………….»:

5- 18 Administration of certain drugs steadily through thin skin – adhesive patches Lipid soluble substances can be absorbed through the skin (vitamins A, D, E and K, acetone and dry-cleaning fluid, lead, mercury, arsenic, poisons in poison ivy and oak) Physiology of the Skin « Excretion & Absorption – Contd …………. »

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Sunlight activates a precursor to vitamin D, Enzymes in the liver and kidneys transform that molecule into calcitriol (most active form of vitamin D) Necessary vitamin for absorption of calcium from food in the gastrointestinal tract (obtained from the diet) Physiology of the Skin « Synthesis of Vitamin-D »

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Appearance & social acceptance, Facial expression and nonverbal communication, Acne, Birth marks, Scars. Physiology of the Skin « Psychological & Social Functions »

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Integumentary System Dermis Sebaceous gland Hair shaft Sweat gland pore Capillary Dermal papilla Basal layer Touch receptor Sweat gland duct Arrector Pili muscle Sweat gland Nerve fibre Hair follicle Epidermis Hypodermis (Subcutaneous layer) Blood vessles

Structure of the Skin:

Structure of the Skin Sensory nerve fibers Apocrine sweat gland Piloerector muscle Lamellar (pacinian) corpuscle (pressure receptor) Hair bulb Motor nerve fibers Cutaneous blood vessels Hypodermis (subcutaneous fat) Epidermis Merocrine sweat gland Hair receptor Dermal papilla Blood capillaries Hair follicle Sebaceous gland Hairs Sweat pores Dermis Tactile corpuscle (touch receptor)

The Skin - Layers:

Composed of keratinized stratified squamous epithelium, dead cells at the surface packed with tough protein – keratin, Avascular as it has no blood supply of its own, Depends on the diffusion of Oxygen and nutrients from the underlying dermis, sparse nerve endings for touch and pain Five structurally different layers can be identified: The Skin - Layers Epidermis - outer

The Skin - Layers:

The Skin - Layers Epidermis – 5 Layers 1- The stratum corneum, 2- The stratum lucidum, 3- The stratum granulosum, 4- The stratum spinosum, 5- The stratum basale . Dermis Superficial Deep

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Cell Types & Layers of the Epidermis

The Skin - Layers:

1. The stratum corneum, Makes up 3/4th of the epidermal thickness, Upto 30 cells-thick layer of dead, scaly, keratinized cells. Forms durable surface layer » surface cells are constantly shed from this part. Individual cells are difficult to observe because (1) nuclei can no longer be identified, (2) the cells are very flat and (3) the space between the cells has been filled with lipids, which cement the cells together into a continuous membrane. Somewhat looser appearance closest to the surface of the epidermis, Resistant to abrasion, penetration, and water loss, The protection of the body by the epidermis is due to the functional features of the stratum corneum . The Skin - Layers Epidermis – 5 Layers

The Skin - Layers:

2. The stratum lucidum: Thin translucent zone superficial to stratum granulosum, Several layers of flattened dead cells, Has a pale, featureless appearance with indistinct boundaries . Usually seen only in thick skin Keratinocytes are packed with eleidin, a precursor to keratin does not stain well cells have no nucleus or other organelles. The Skin - Layers Epidermis – 5 Layers

The Skin - Layers:

3. The stratum granulosum Consists of 3 to 5 layers of flattened keratinocytes (in thick skin), Contain coarse dark-staining keratohyalin granules Only one layer may be visible in thin skin. Produce lipid-filled vesicles that release a glycolipid by exocytosis to waterproof the skin. forms a barrier between surface cells and deeper layers of the epidermis The Skin - Layers Epidermis – 5 Layers

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4. The stratum spinosum , Several layers of keratinocytes thick, appear spiny due to shrinkage during histological preparation, Thickest stratum in most skin, Contains dendritic (Langerhans) cells (macrophages from bone marrow that migrate to the epidermis) 800 cells/millimeter 2 help protect body against pathogens by “presenting” them to the immune system. The Skin - Layers Epidermis – 5 Layers

The Skin - Layers:

5. The stratum basale; Single layer of cuboidal or low columnar cells sitting on basement membrane Cell types in this layer; Keratinocytes; undergo mitosis to replace epidermis most of cells of epidermis Melanocytes; synthesize and distribute melanin from cell processes, melanin picked up by keratinocytes & used to shade their nuclei from UV radiation Merkel cells are touch receptors associated with nerve fibers to form Merkel disc The Skin - Layers Epidermis – 5 Layers

The Skin - Layers:

Five types of cells of the epidermis Stem cells (in stratum basale ) undifferentiated cells that give rise to keratinocytes Keratinocytes great majority of epidermal cells synthesize keratin Melanocytes ( only in stratum basale ) synthesize pigment melanin that shields DNA from ultraviolet radiation branched processes that spread among keratinocytes The Skin - Layers Cells of Epidermis

The Skin - Layers:

Tactile (merkel) cells (in stratum basale) touch receptor cells associated with dermal nerve fibers, Dendritic (langerhans) cells macrophages originating in bone marrow that guard against pathogens, found in stratum spinosum and granulosum stand guard against toxins, microbes, and other pathogens that penetrate skin. The Skin - Layers Cells of Epidermis

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Dermal blood vessels Tactile cell Melanocyte Dead keratinocytes Exfoliating keratinocytes Living keratinocytes Dendritic cell Stem cell Dermis Stratum lucidum Stratum basale Stratum granulosum Stratum spinosum Stratum corneum Sweat pore Tactile nerve fiber Dermal papilla Sweat duct Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cell Types & Layers of the Epidermis

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Stem cells, in stratum basale, produce keratinocytes; some deepest keratinocytes in stratum spinosum also multiply and increase their numbers, Abundant amount of oxygen and nutrients, required for mitosis is supplied from blood vessels in nearby dermis; Mitosis ceases, once epidermal cells migrate more than two or three cells away from the dermis, Newly formed keratinocytes push the older ones toward the surface, Keratinocytes – Life History

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In 30 - 40 days a keratinocyte makes its way to the skin surface and flakes off; slower in old age, faster in skin injured or stressed; calluses or corns – thick accumulations of dead keratinocytes on the hands or feet Cytoskeleton proliferates as cells are shoved upward, Cells grow flatter, Produce lipid-filled membrane-coating vesicles (lamellar granules), Keratinocytes – Life History

Slide 36:

In stratum granulosum three important developments occur; Keratinocyte nucleus and other organelles degenerate, cells die, Keratohyalin granules release a protein “ filaggrin” that binds the keratin filaments together into coarse, tough bundles, Membrane-coating vesicles release lipid mixture that spreads out over cell surface and waterproofs it. Keratinocytes – Life History

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Forms between stratum granulosum and stratum spinosum and consists of; Lipids secreted by keratinocytes, Tight junctions between keratinocytes, Thick layer of insoluble protein on the inner surfaces of the keratinocyte plasma membranes, Critical to retaining water in the body and preventing dehydration, cells above the water barrier quickly die; Barrier cuts them off from nutrients below, Dead cells exfoliate (dander), Dandruff – clumps of dander stuck together by sebum (oil). Epidermal Water Barrier

The Skin - Layers:

A layer of dense fibrous connective tissue, beneath the epidermis, Composed mainly of collagen with elastic fibers , reticular fibers , and fibroblasts , Much thicker than the epidermis, Ranges from 0.2 mm (eyelids) – 4 mm (palms & soles), Well supplied with blood vessels, sweat glands, sebaceous glands, and nerve endings (sense pain, temperature, pressure, and touch) In thick skin, dermal papillae create a very irregular border between epidermis and dermis. The Skin - Layers Dermis ( Corium) – Inner

The Skin - Layers:

The Skin - Layers Dermis ( Corium) – Inner Hair follicles and nail roots are embedded in dermis, Smooth muscle ( piloerector muscles ) associated with hair follicles, contract in response to stimuli, such as cold, fear, and touch – goose bumps Dermal papillae – upward fingerlike extensions of the dermis; friction ridges on fingertips that leave fingerprints.

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Papillary Layer – superficial zone of dermis; Thin zone of areolar tissue in and near the dermal papilla, Allows for mobility of leukocytes and other defense cells should epidermis become broken, Rich in small blood vessels, Reticular Layer – deeper and much thicker layer of dermis; Consists of dense, irregular connective tissue Stretch marks (striae) – tears in the collagen fibers caused by stretching of the skin due to pregnancy or obesity. The Skin - Layers Dermis ( Corium) – Inner

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Integumentary System - Dermis Dermis Sebaceous gland Hair shaft Sweat gland pore Capillary Dermal papilla Basal layer Touch receptor Sweat gland duct Arrector Pili muscle Sweat gland Nerve fibre Hair follicle Epidermis Hypodermis (Subcutaneous layer) Blood vessles

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(a) (a) Papillary layer of dermis (b) Reticular layer of dermis Structure of the Dermis

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Subcutaneous tissue, More areolar and adipose than dermis, Pads body, Binds skin to underlying tissues, Drugs introduced by injection; Highly vascular & absorbs them quickly Subcutaneous fat; Energy reservoir, Thermal insulation, 8% thicker in women. The Skin - Layers Hypodermis – Subcutaneous Layer

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Integumentary System - Hypodermis Dermis Sebaceous gland Hair shaft Sweat gland pore Capillary Dermal papilla Basal layer Touch receptor Sweat gland duct Arrector Pili muscle Sweat gland Nerve fibre Hair follicle Epidermis Hypodermis (Subcutaneous layer) Blood vessles

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Subcutaneous Fat Distribution

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Melanin – is the most significant factor in skin color; produced by melanocytes and accumulated in the keratinocytes of stratum basale and stratum spinosum, Eumelanin – brownish black, Pheomelanin - a reddish yellow sulfur-containing pigment, The number of melanocytes is the same in all races, but more melanin is released in darker skinned individuals. Skin Colour

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Stratum corneum Epidermis Dermis (a) Dark skin (b) Light skin Melanized cells of stratum basale Dermis Skin Colour

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Heredity and environment determine skin color, Ultraviolet light and X-rays stimulate melanocytes to synthesize melanin, Dark skinned people; produce greater quantities of melanin, melanin granules in keratinocytes more spread out than tightly clumped, melanin breaks down more slowly, melanized cells seen throughout the epidermis, Light skinned people; melanin clumped near keratinocyte nucleus, melanin breaks down more rapidly, little seen beyond stratum basale , Factors influencing Skin Colour

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Oxygenated blood creates a pink tint to skin, Hemoglobin – Iron-containing red pigment of RBCs, adds reddish to pinkish hue to skin, The red and yellow hues of the skin are due to hemoglobin in the red blood cells , which pass through the capillaries beneath the epidermis, Lack of oxygen results in cyanosis where the skin appears bluish, Factors influencing Skin Colour

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Carotene , – A yellowish pigment, found in yellow/orange vegetables (such as carrots), and egg yolks, accumulates in fat cells found in the dermis and hypodermis, Can create a yellow or ashen tint to skin, Usually hidden by the effects of melanin, Asians have little melanin which allows the yellow to show more than other nationalities. Other Factors influencing Skin Colour

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Melanocytes: The brown skin color is due to melanin , which is produced in the skin (epidermis) itself in cells called melanocytes , the melanin is located in membrane-bound organelles called melanosomes. Melanocytes can transfer melanin to keratinocytes - mainly to the basal cells. Melanocytes eumelanosome phaeomelanosome Melanocyte Melanin granules Golgi Apparatus Melanocyte Nucleus Cellular Extension of Melanocyte premelanosome dendrite

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Melanin Melanin protects the chromosomes of mitotically active basal cells against light-induced damage. Hormones produced by the pituitary and the adrenal glands also affect pigmentation. Melanocyte Melanin Diseases of these two endocrine organs often result in changes of pigmentation of the skin.

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Albinism – (from Latin albus , "white“), also called achromia, achromasia, or achromatosis is a genetic disorder characterized by the complete or partial lack of melanin pigment due to absence or defect of an enzyme, tyrosinase, involved in the production of pigment, that results in white hair, pale skin and pink eyes. Malfunctioning Melanocytes

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Vitiligo – is a condition that causes depigmentation of patches of skin, It occurs when melanoctyes (cells responsible for skin pigmentation) die or are unable to function. Malfunctioning Melanocytes

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A freckle (ephelis) is an increase in pigment in the deep (basal) layer of the epidermis, A mole (nevus) is a small elevated melanized patche often with hair, Composed of cluster of melanocytes in the basal layer of the epidermis, Should be watched for changes in color, diameter, or contour, May suggest malignancy (skin cancer). Malfunctioning Melanocytes

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Malignant melanoma – is a cancerous change in a mole that may metastasize (spread) rapidly and is most difficult to treat, Exposure to sunlight increases risk. Malfunctioning Melanocytes

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Cyanosis – blue look to skin due to poorly oxygenated blood; Airway obstruction (drowning or choking), Lung diseases (emphysema or respiratory arrest), Cold weather or cardiac arrest, Jaundice – yellowing of skin and sclera due to excess of bilirubin in blood, caused by liver malfunction; cancer, hepatitis, cirrhosis, other compromised liver function Adrenal gland Disease : Skin may appear bronzed due to the deposit of excess melanin, Hematoma – (bruise); indicates mass of clotted blood showing through skin. Response to Disease

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Erythema – abnormal redness of the skin due to dilated cutaneous vessels, Blushing – caused by dilation of blood vessels; Exercise, hot weather, sunburn, anger, or embarrassment, pallor – pale or ashen color caused by constriction of vessels, resulting in so little blood flow through the skin that the white color of dermal collagen shows through; emotional stress, low blood pressure, circulatory shock, cold, anemia Response to Disease

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Skin color – one of the most conspicuous sign of human variation, Results from combination of evolutionary selection pressures; especially differences in exposure to ultraviolet radiation (UVR), UVR has a desirable effect: stimulates synthesis of vitamin D necessary for dietary calcium absorption, UVR has two adverse effects: causes skin cancer, breaks down folic acid needed for normal cell division, fertility, and fetal development. Skin Colour Evolution of

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Populations native to the tropics and their descendants tend to have well-melanized skin to screen out excessive UVR in order to prevent the overproduction of vitamin D, Populations native to far northern or southern latitudes where the sunlight is weak, tend to have light skin to allow for adequate UVR penetration in order to maximize vitamin D production. Ancestral skin color is a compromise between vitamin D and folic acid requirements, Women have skin averaging about 4% lighter than men; need greater amounts of vitamin D and folic acid to support pregnancy and lactation, Skin Colour Evolution of

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Skin Colour Evolution of Skin colour variations

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High altitude and dry air increases skin pigmentation; Andes, Tibet, Ethiopia UVR accounts for up to 77% of variation in human skin color, Other exceptions: Migration, cultural differences in clothing and shelter, Intermarriage of people of different geographic ancestries, Darwinian sexual selection – a preference in mate choice for partners of light or dark complexion. Skin Colour Evolution of

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The Andes Mountains Peru (South America); the longest and one of the highest mountain ranges in the world .

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Friction ridges: – the markings on the fingertips that leave oily fingerprints on surfaces we touch; everyone has a unique pattern formed during fetal development and remain unchanged throughout life, not even identical twins have identical fingerprints, allow manipulation of small objects. Flexion lines (flexion creases) – lines on the flexor surfaces of the digits, palms, wrists, elbows; marks sites where the skin folds during flexion of the joints, Freckles – tan to black flat, melanized patches, Moles - small elevated melanized patches, often with hair, Hemangiomas (birthmarks) – patches of discolored skin caused by benign tumors of dermal blood capillaries; some disappear in childhood -- others last for life. ( capillary hemangiomas, cavernous hemangiomas, port-wine stain) Skin Markings

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Hair Nails (Composed mostly of dead, keratinized cells) Sweat glands Sebaceous or oil glands Mammary glands Skin – Accessory Structures

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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. HAIR Skin – Accessory Structures

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Most of the human body is covered with hair, Truly hairless are only; palms and soles ventral and lateral surface of fingers and toes distal segment of the finger lips, nipples, and parts of genitals, Limbs and trunk have 55 – 70 hairs per cm 2 face about 10 times as many 30,000 hairs in a man’s beard 100,000 hairs on an average person’s scalp number of hairs does not differ much from person to person or even between sexes differences in appearance due to texture and pigmentation of the hair Distribution of Human HAIR

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Three kinds of hair grow over the course of our lives; Lanugo – fine, downy, unpigmented hair that appears on the fetus in the last three months of development, Vellus – fine, pale hair that replaces lanugo by time of birth; 2/3rds of the hair of women, 1/10th of the hair of men, all of hair of children except eyebrows, eyelashes, and hair of the scalp, Terminal – longer, coarser, and usually more heavily pigmented; forms eyebrows, eyelashes, and the hair of the scalp, after puberty, forms the axillary and pubic hair, male facial hair and some of the hair on the trunk and limbs. Types of Human HAIR

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The cuticle scale on a normal hair ( Electronmicrograph ) Slight lifting of the edge of the hair cuticle ( Electronmicrograph ) Hair is a slender filament of compact hard (due to numerous cross-linkages between keratin molecules) keratinized cells that grows from an oblique tube in the skin called a hair follicle , Pilus – another name for hair ( “ pili ” – plural) Structure of Hair

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Hair is divisible into three zones along its length Bulb – a swelling at the base where hair originates in dermis or hypodermis; Only living hair cells are in or near bulb, Root – the remainder of the hair in the follicle, Shaft – The free part of each hair above the skin surface, Dermal Papilla – bud of vascular connective tissue encased by bulb; provides the hair with its sole source of nutrition, Hair Matrix (Hair’s growth center) - region of mitotically active cells immediately above papilla; . Structure of Hair

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Structure of Hair Medulla Cortex Cuticle Three layers, in cross-section from inside out; Medulla:- core of loosely arranged cells and air spaces, Cortex:- constitutes the bulk of the hair; consists of several layers of elongated keratinized cells, Cuticle: composed of multiple layers of very thin, scaly cells that overlap each other, free edges directed upward.

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Dermal papilla Epithelial root sheath Hair medulla Hair matrix Dermal papilla Connective tissue root sheath Hair cortex Hair bulb Structure of Hair & Follicle

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Hair follicle – An oblique diagonal tubular invagination of the epidermis that dips deeply into dermis and may extend into hypodermis, Anchors the root of each hair, Epithelial root sheath is an extension of the epidermis (lies next to hair root); toward deep end widens into bulge - a source of stem cells for follicular growth, Connective tissue root sheath is derived from the dermis; surrounds epithelial root sheath, denser than adjacent connective tissue. Structure of Hair Follicle

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Hair receptors entwine each follicle, respond to hair movement, Arrector pili muscle Bundle of smooth muscle cells, associated with each hair follicle, Inserts with one end to the papillary layer of the dermis and with the other end to the dermal sheath of the hair follicle. Makes hair stand up on its end ~ goose bumps Structure of Hair Follicle

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Structure of Hair Follicle

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Ultramicroscopic picture of a Hair Follicle Structure of Hair Follicle

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Structure of Hair Follicle

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Most hair on trunk and limbs is vestigial; little present function, warmth in ancestors, Body hair too thin to provide warmth, Sensory functions; hair receptors alert of parasites crawling on skin, Scalp hair provides heat retention & sunburn cover, Gender identification: Sex and individual recognition, Functions of Hair

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Beard, pubic & axillary hair indicate sexual maturity & help distribute sexual scents Guard hairs (vibrissae) & eyelashes prevent foreign objects from getting into nostrils, ear canals or eyes Expression of emotions with eyebrows; nonverbal communication Functions of Hair

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Hair color:- is determined by the amount and type of melanin pigment present in the cells of the cortex; brown and black hair is rich in Eumelanin, Melanocytes become less active with age, Gray hair is a mixture of pigmented and non-pigmented hairs, Gray and white hair results from scarcity or absence of melanin in the cortex and the presence of air in the medulla, Red hair results from a a modified type of melanin that contains iron. Red hair has a slight amount of eumelanin but a high concentration of pheomelanin , Blonde hair has an intermediate amount of pheomelanin and very little eumelanin. Hair Color and Texture

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Texture and cross-sectional shape of hair: Texture – related to differences in cross-sectional shape of the hair shaft; Straight hair ~ round shaft, Wavy hair ~ oval shaft, Curly or kinky hair ~ flat shafts, Perms use chemicals to flatten shafts and makes hair curly. Hair Color and Texture

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Hair Colour and Texture, Blonde Hair Colour and Texture, Brunette Melanin Cortex Medulla Cuticle Brunette (brown hair) , has more eumelanin than blonde hair but much less than black. Blonde is due to a scanty amount of melanin pigment.

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Hair Colour and Texture, Red Hair Colour and Texture, Grey and White Air Trichosiderin Red hair is colored by an iron- containing pigment, trichosiderin . White hair is due to air in medulla & lack of pigment in cortex. Gray hair is a mixture of white and pigmented hairs.

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Hair follicles grow in repeated cycles. One cycle can be broken down into three phases. Anagen - Growth Phase Catagen - Transitional phase Telogen - Resting Phase Each hair passes through the phases independent of the neighboring hairs. The Hair Growth Cycle Anagen Telogen Catagen

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Approximately 85% of all hairs and 90% of scalp follicles are in the growing phase at any given time, Hair grows @ about 10cm per year, Any individual hair is unlikely to grow more than one meter long, The Hair Growth Cycle Anagen Phase/Growth Phase: (2 - 6 years)

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Epidermis Dermis Hair matrix Sebaceous gland Old club hair Piloerector New hair Bulge Club hair (detached from matrix) Club Dermal papilla Degeneration of lower follicle Hair bulb 3 Anagen /Growth Phase (2 – 6 Years) (Mature) (Early) The Hair Growth Cycle Stem cells multiply and push dermal papilla deeper into skin forming epidermal root sheath, Root sheath cells directly above dermal papilla form the hair matrix, Hair matrix cells multiply, synthesize keratin, and die as they are pushed upward, New hair grows up the follicle, often alongside of an old club hair from the previous cycle. Stem cells multiply, follicle grows deeper into dermis, hair matrix cells multiply and keratinize, causing hair to grow upward; Anagen /Growing Phase:

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Epidermis Dermis Hair matrix Sebaceous gland Old club hair Piloerector New hair Bulge Hair bulb 2 1 The Hair Growth Cycle Club hair (detached from matrix) Club Degeneration of lower follicle Dermal papilla Catagen /Transitional Phase: (2 – 4 weeks) Hair growth ceases; Hair bulb keratinizes and forms club hair; Lower follicle degenerates . Catagen/transitional phase: (2 – 4 weeks) The hair follicle shrinks to about 1/6 of the normal length, The lower part is degenerated and the dermal papilla breaks away to rest below Hair growth ceases and sheath cells below the bulge die, dermal papilla is drawn up toward the bulge, base of hair keratinizes into a hard club, forming; club hair, loses its anchorage & easily pulled out by brushing

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Epidermis Dermis Hair matrix Sebaceous gland Old club hair Piloerector New hair Bulge Club Hair bulb 2 (Resting phase, 1–3 months) Dermal papilla has ascended to level of bulge; club hair falls out, usually in telogen or next anagen. 1 Telogen Phase Telogen/resting phase: (5-6 weeks) Hair ceases to grow & stays attached to The follicle; Dermal Papilla stays in a resting phase below. Approximately 10-15 percent of all hairs are in this phase at an one time. The Hair Growth Cycle Hair ceases to grow & Stays attached to the follicle; Dermal Papilla in a resting phase below .

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At the end of the Telogen phase the hair follicle re-enters the Anagen phase. The dermal papilla and the base of the follicle join together again and a new hair begins to form. The Hair Growth Cycle If the old hair has not already been shed the new hair pushes the old one out and the growth cycle starts all over again.

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Mitosis in stratum basale of epithelial root sheath; as become keratinized are pushed upward, Grows 1 mm every 3 days for 2 to 4 years dormant phase lasts 3 to 4 months as new hair begins to grow it pushes out old hair eyelashes and eyebrows only grow for 3 to 4 months Hair Growth and Loss

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Club hair may fall out during catagen or telogen; or pushed out by new hair in the next anagen phase We lose about 50 – 100 scalp hairs daily, In young adult the scalp follicles spend: 6 – 8 years in anagen, 2 – 3 weeks in catagen, 1 - 2 months in telogen, Hair growth - scalp hairs grow at a rate of 1 mm per 3 days (10 -18 cm/yr). Hair Growth and Loss

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Alopecia: is the term for patchy thinning or loss of hair loss, Pattern Baldness: is the condition in which there is hair loss from specific regions of the scalp rather than thinning uniformly, Combination of genetic and hormonal influence, Baldness allele is dominant in males and expressed only in high testosterone levels, Testosterone causes terminal hair in scalp (on top & then sides) to be replaced by vellus hair, Baldness in females if homozygous recessive with abnormal testosterone. Hair Growth and Loss Alopecia areata

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Hirsutism ~ A bnormal hairiness in women or children; Masculinizing ovarian tumors or adrenal cortex hypersecretion of testosterone, Hair Growth and Loss Male Pattern Baldness Hirsutism

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NAILS

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Fingernails and Toenails: Are clear, hard derivatives of the stratum corneum , Consist of a nail plate (dead stratified squamous epithelial cells, packed with hard keratin) over a growing epithelium of the nail bed on the skin surface. Flat nails allow for more fleshy and sensitive fingertips, tools for digging, grooming, picking apart food, and other manipulations, Protect distal ends of phalanges. Nails

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Nail matrix – growth zone of thicken stratum basale at the proximal end of nai;l mitosis here accounts for nail growth. new cells added by mitosis in the nail matrix, extends beneath the nail root and contains nerves, lymph and blood vessels, 1 mm per week in fingernails, slightly slower on toenails Lunule – the whitish crescent-shaped base of the visible nail; Is the region of most active growth. The nail bed is the skin beneath the nail plate The nail root is the base of the nail embedded underneath the skin. Nails - Anatomy

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The Nail plate or body of nail: Is the actual nail, made of several layers of dead, flattened cells, packed with translucent protein, Keratin , The free margin ( distal edge) : is the anterior margin of the nail plate corresponding to the abrasive or cutting edge of the nail. The hyponychium: is the epithelium located beneath the nail plate at the junction between the free edge and the skin of the fingertip. Forms a seal that protects the nail bed. Nails - Anatomy

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The eponychium: (cuticle) is the small band of epithelium that extends from the posterior nail wall onto the base of the nail, The nail fold: is the cutaneous fold overlapping the sides and proximal end of the nail, The nail groove is the cutaneous slit into which the lateral margin of nail is embedded, The paronychium: is the border tissue around the nail ~ scrub for operating room. Nails - Anatomy

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Free edge Nail body Nail Groove Lunule Eponychium (cuticle) Nail Matrix Eponychium (cuticle) Nail Bed Hypochondrium Free edge Nail body Nail Root Nail plate Nail fold Fingernail Structure

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The skin has Five types of glands; Sebaceous glands or oil glands, Merocrine sweat glands Apocrine sweat glands Modified sweat glands : Ceruminous glands secrete ear wax. Mammary glands secrete breast milk Cutaneous (Exocrine) Glands

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The relationship of the hair follicle, eccrine and apocrine sweat glands and sebaceous glands. Sebaceous gland Merocrine sweat gland Apocrine sweat gland Cutaneous (Exocrine) Glands

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Merocrine gland: One whose discharged secretion contains no part of the secreting cells, Apocrine Gland: One whose discharged secretion contains part of the secreting cells, Holocrine Gland: One whose discharged secretion contains the entire secreting cells . Exocrine Glands - Classification

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Are simple branched flask-shaped holocrine glands with short ducts opening into hair follicle, Holocrine gland – secretion consists of broken-down cells ~ replaced by mitosis at base of gland, They secrete an oily product, the sebum ( seb = oil), usually into a hair follicle. 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 Cutaneous (Exocrine) Glands

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Sebaceous gland Hair follicle Gland Sebaceous Glands

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Sebum: (a natural skin cream) oily secretion produced by sebaceous glands, a mixture of fatty material and cellular debris, prevents skin and hair from becoming dry, brittle, and cracked, keeps hair and skin soft and waterproof, contains a bactericidal agent that inhibits the growth of certain bacteria Lanolin – sheep sebum Acne - results from excess sebum secretion. Sebaceous Glands Cutaneous (Exocrine) Glands

Slide 107:

Are simple coiled tubular glands. Divided into two principal types; Merocrine (eccrine) sweat glands, Apocrine sweat glands, 1. Merocrine (eccrine) sweat glands, Most numerous simple tubular skin glands, 3 to 4 million in adult skin, Produce sweat that prevents overheating of the body and thus helps regulate body temperature. Watery perspiration helps cool the body, Myoepithelial cells – contract in response to stimulation by sympathetic nervous system and squeeze perspiration up the duct, Their secretory portion can be located in the dermis or in the hypodermis, Sweat (sudoriferous) Glands Cutaneous (Exocrine) Glands “Respond to increased body temperature and function in evaporative cooling”

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Myoepithelial cells Secretory cells Lumen Lumen Merocrine (Eccrine) Sweat glands Merocrine ( Eccrine ) Sweat Glands

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2. Apocrine sweat glands, Are found mainly in the skin of groin, anal region, axilla, areola, bearded area in mature males and the areola of the breasts. Their excretory ducts open into the nearby hair follicles, Produce sweat that is more viscous than that of the eccrine glands (thicker, milky, and contains fatty acids), They become active at puberty and secrete sweat that produces body odor when metabolized by bacteria, Analogous to the sexual scent glands of other animals, (scent glands that respond to stress and sexual stimulation), They can respond to pain, fear, and emotions. Their secretory portion can be located in the dermis or in the hypodermis. Sweat (sudoriferous) Glands Cutaneous (Exocrine) Glands

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2. Apocrine sweat glands – (contd…………) , Pheromones – chemicals that influence the physiology of behavior of other members of the species, Bromhidrosis - disagreeable body odor produced by bacterial action on fatty acids. Sweat (sudoriferous) Glands Cutaneous (Exocrine) Glands

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Lumen Secretory cells Apocrine Sweat glands Apocrine Sweat Glands

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Potassium ions, urea, lactic acid, ammonia, and some sodium chloride remain in the sweat, most sodium chloride reabsorbed by duct, Some drugs are also excreted in sweat, On average, 99% water, with pH range of 4 to 6; acid mantle – inhibits bacterial growth, Insensible perspiration – 500 ml per day; does not produce visible wetness of skin, Diaphoresis – sweating with wetness of the skin; exercise – may lose one liter of sweat per hour. Sweat “A protein-free filtrate of blood plasma produced by deep secretory portion of Sweat gland”

Slide 113:

Nervous system signals dermal blood vessels to dilate and sweat glands to secrete Body heat is lost to its surroundings Muscle activity generates body heat Body temperature drops below normal Normal Body temperature 37 0 C (98.6 0 F) Body temperature drops towards normal Body temperature Rises towards normal Hypothalamus Hypothalamic set point Body Temperature Regulation Nervous system Signals dermal blood vessels to constrict and sweat glands Remain inactive Body heat is conserved If body temperature continues to drop, nervous system signals Muscles to contract involuntarily Body temperature rises above normal

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Hypothermia or lowered body temperature is a dangerous condition resulting from cold exposure. Hyperthermia or increased body temperature can result from inadequate body cooling during exercise or in extreme heat. Problems in Temperature Regulation

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Found only in external ear canal their secretion combines with sebum and dead epithelial cells to form earwax (cerumen); keep eardrum pliable, waterproofs the canal, kills bacteria, makes guard hairs of ear sticky to help block foreign particles from entering auditory canal, Simple, coiled tubular glands with ducts that lead to skin surface, Ceruminous Glands

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Breasts (mammae) of both sexes contain very little glandular material, Mammary glands – milk-producing glands that develop only during pregnancy and lactation Modified apocrine sweat gland Richer secretion released by ducts opening into the nipple. Mammary Glands

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Mammary Glands Polythelia (Third Nipple) Milk lines Mammary ridges or milk lines : Two parallel lines, formed by thickenings of the epidermis, along the ventral surface of mammals of both sexes; Extend from the upper limbs (arms) to the lower limbs (legs) and give rise to the mammary glands and nipples, Otherwise usually not visible in the adult. two rows of mammary glands in most mammals, primates kept only anterior most glands, Polythelia : (Additional nipples) ~ may develop along milk line.

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