The Integumentary System PDF

THE INTEGUMENTARY SYSTEM PHC411 Dr Gurmeet Kaur Surindar Singh (L7,FF1) Outline ❑ Anatomical and histological structures of the skin ❑ Functions of the skin and relate them to its structure ❑ Explain the process of cutaneous wound healing ❑ Describe the different types of skin...

THE INTEGUMENTARY SYSTEM PHC411 Dr Gurmeet Kaur Surindar Singh (L7,FF1) Outline ❑ Anatomical and histological structures of the skin ❑ Functions of the skin and relate them to its structure ❑ Explain the process of cutaneous wound healing ❑ Describe the different types of skin conditions & disorders  Structure of the skin (superficial thinner portion; Compose of epithelial tissue; avascular) (deeper thicker connective Tissue; vascular) (Consist of aveolar and adipose tissue; store Fat and large amount of blood vessels) Epidermis Dendritic/Langerhans cell (not present in thin skin) Dendritic/Langerhans cell Reference: https://courses.lumenlearning.com/wmopen-biology2/chapter/structure-and-function-of-skin/ Epidermis Keratinized stratified squamous epithelium 4 Major Types of Cells: 1) Keratinocytes Great majority of epidermal cells Synthesize keratin (tough fibrous protein that provides protection) Lamellar granules – water repellent sealant 2) Melanocytes Occur only in stratum basale Synthesize pigment melanin that shields DNA from ultraviolet radiation and contribute to skin color Epidermis 3) Dendritic (Langerhans) cells Macrophages arise from red bone marrow and migrate to epidermis - that guard against pathogens Found in stratum spinosum and granulosum Involved in immune responses. 4) Tactile (Merkel) cells In basal layer of epidermis contact with the flattened process of a sensory neuron (nerve cell) a structure called Merkel (tactile) disc – both detect touch sensation stimulating sensory nerves that the brain perceives as touch Epidermis Epidermis  Epidermis Layers of the epidermis: Stratum basale A single layer of cuboidal to low columnar stem cells and keratinocytes resting on the basement membrane Melanocytes and tactile cells are scattered among the stem cells and keratinocytes. New cells cannot regenerate if large layer destroyed – require skin graft Stratum spinosum Produce more and more keratin filaments which causes cell to flatten; the higher up in this stratum, the flatter the cells appear. Langerhans cells and projection of melanocytes are found throughout this stratum. Epidermis Stratum granulosum Consists of 3 - 5 layers of flat keratinocytes undergoing apoptosis. Contains coarse dark-staining keratohyalin granules and lamellar granules. Stratum lucidum Seen only in thick skin- present only in fingertips, palms, soles Consists 4-6 flattened clear, dead, keratinocytes with large amount of keratin and thickened plasma membrane Stratum corneum Up to 30 layers of dead, scaly, keratinized cells (multiple layer protect deeper layer against injury and microbial invasion). Form durable surface layer Surface cells flake off (exfoliate). Resistant to abrasion, penetration, and water loss Callus : constant exposure of skin to friction increases cell and keratin production causes abnormal thickening of this layer Keratinization and growth of the Epidermis Keratinization is the process of replacing viable cells in the stratum basale with more and more of the waxy keratin protein as cells move from the deepest layer to the surface layer. Dandruff is an excess of keratinized cells shed from the scalp.  Psoriasis http://1.bp.blogspot.com/-H89QblBFUps/TxI7pkGw_yI/AAAAAAAAAx0/X3MNS-2FUD8/s400/psoriasis-herbal-treatments.jpg Psoriasis is a chronic skin disorder in which keratinocytes divide and move more quickly than normal from the stratum basale to the stratum corneum Immature keratinocytes makes abnormal keratin that forms flaky silver scales Dermis Composed of dense irregular connective tissue containing collagen and elastic fibers Thicker than epidermis depending to region of body Consist of fibroblast, some macrophages and few adipocytes. Blood vessels, nerves, glands, and hair follicles are embedded in the dermal layer Divided into thin superficial papillary region and a thick deeper reticular region. Dermis Papillary region 1/5 of total thickness, Surface area is greatly increased by dermal papillae Consists areolar connective tissue containing thin collagen and elastic fiber dermal papillae contains capillary loops, corpuscles of touch and free nerve endings Reticular region dense irregular connective tissue containing thick collagen and elastic fibers, adipose cells (deepest part), hair follicles, nerves, sebaceous (oil) glands, and sudoriferous (sweat) glands. Finger Prints In a growing fetus, fingerprints form where the cells of the stratum basale meet the papillae of the underlying dermal layer (papillary layer), resulting in the formation of the ridges on your fingers that you recognize as fingerprints. Fingerprints are unique to each individual and are used for forensic analyses because the patterns do not change with the growth and aging processes  Not part of the integumentary system but important in stabilizing Subcutaneous layer the position of the skin relative to underlying tissues Transdermal drug administration: substance absorb through the skin. Drugs are dissolved in oils or lipid-soluble solvents to help carry drugs across plasma membrane. Movement is slow. eg nicotine patches, painkillers release slowly over time to control chronic pain. SC layer has moderate supply of blood compared to the muscle tissue (good supply of blood), so SC injection of drug (eg insulin) absorption will be moderate compared to muscle tissue (eg; vaccines = rapid absorption to stimulate antibody production) The structural basis of skin colour Melanin—most significant factor in skin color Melanocytes produce specific organelle called melanosomes, in which melanin pigment is synthesized and deposited. Accumulate in the keratinocytes of stratum basale and stratum spinosum Eumelanin—brownish to black Pheomelanin – yellow to red Melanocytes Melanocytes synthesis melanin in an organelle called melanosome. Tyrosine tyrosinase melanin Exposure to UV light increases the enzymatic activity and increase melanin production. Darkness increases on UV exp.-tan Melanin function: 1. absorb UV 2. prevent damage to DNA 3. Neutralizes free radical that forms following UV radiation.  Skin color People of different skin colors have the same number of melanocytes. Amount of melanin also varies with exposure to ultraviolet (UV) rays of sunlight Dark skin Light Skin 1. Melanin granules in keratinocytes Melanin clumped near keratinocyte more spread out than tightly clumped nucleus. 2. Melanin breaks down more slowly Melanin breaks down more rapidly 3. Melanized cells seen throughout the Little seen beyond stratum basale epidermis  Stratum corneum Stratum corneum Epidermis Epidermis Melanized cells of stratum basale Dermis (a) Dark skin (b) Light skin Hemoglobin—red pigment of red blood cells Adds reddish to pinkish hue to skin Carotene—yellow-orange pigment acquired from egg yolks and yellow/orange vegetables Concentrates in stratum corneum and subcutaneous fat Skin color Colors of diagnostic value Cyanosis - blueness of the skin from deficiency of oxygen in the circulating blood Airway obstruction (drowning or choking) Lung diseases (respiratory arrest) Cold weather or cardiac arrest Erythema - abnormal redness of the skin due to dilated cutaneous vessels Exercise, hot weather, sunburn, anger, or embarrassment Skin color Pallor - pale or ashen color when there is so little blood flow through the skin that the white color of dermal collagen is visible Emotional stress, low blood pressure, circulatory shock, cold, anemia Albinism—genetic lack of melanin that results in white hair, pale skin, and pink eyes Have inherited recessive, nonfunctional tyrosinase allele Tyrosine melanin requires tyrosinase. No tyrosinase = no melanin! Skin color Jaundice - yellowing of skin and sclera due to excess of bilirubin in blood Cancer, hepatitis, cirrhosis, other compromised liver function Blockage of ducts that drain the gall bladder Vitiligo - loss of melanocytes form patches of skin →irregular white spots. malfunction of immune system Accessory Structures of the Skin  Hair Hair is associated with the word “pili”. It is present on most surfaces except the palms, anterior surfaces of fingers, and the soles of the feet. It is composed of dead, keratinized epidermal cells. Genetics and hormones determines thickness and distribution. ❖ Hair helps with touch sensations and protects the body against the harmful effects of the sun and against heat loss.  Hair The parts of a hair include: The shaft (above the skin surface) The follicle/root (below the level of the skin) A root that penetrates into the dermis includes: An epithelial root sheath A dermal root sheath Hair follicle is the part that holds the hair & responsible in hair growth  Medulla: Core of loosely arranged cells Hair and air spaces Cortex- Constitutes 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 Hair follicle – surrounding the root of the hair – made up of external (downwards continuation of the epidermis) and internal root sheath (is produced by matrix). Dermal root sheath – dense dermis surrounding the hair follicle Bulb- base of each hair follicle and its surrounding dermal root sheath shape like onion Papilla of the hair contains areolar connective tissue and many blood vessels that nourish the growing hair follicle. The bulb also contains hair matrix – arise from stratum basale, site of cell division. – thus responsible for growth of existing hair, and they produce new hair when old hair shed Hair growth 3 stages: 1. Growth stage (2-6 years) – cells of the hair matrix divides 2. Regression stage (2 or 3 weeks) – cells of hair matrix stop dividing, hair follicle shrinks, and hair stop growing 3. Resting stage (3 months) – following the resting stage, a new growth cycle begins, old hair pushed out the hair follicle, new hair grows in its place. ▪ Visible hair is dead but until pushed out by new hair, the portion of root in the scalp are alive ▪ Rate of growth and replacement is altered by illness, radiation therapy, chemotherapy, age, genetics, gender, severe emotional stress.  Hair Types of hairs Lanugo – fine, nonpigmented, downy hairs that cover the body of the fetus Vellus hairs – short, fine, pale hairs barely visible to the naked eye Terminal hairs – long, coarse, heavily pigmented hairs Hair color is determined by the amount and type of melanin (synthesize by melanocytes scattered at the matrix of bulb and passes into cells of the cortex and medulla of hair). Gray hair – progressive decline in melanin production Alopecia - thinning of hair or baldness Hirsutism - excessive/undesirable hairiness in area that not usually hairy (tumors of adrenal, testes, ovaries that produces excessive androgens)  Nails Nails are composed of hard, keratinized epidermal cells located over the dorsal surfaces of the ends of fingers and toes. Nail structures include: Free edge Transparent nail body (plate) with a whitish lunula at its base Nail root embedded in a fold of skin  Nails Hyponychium – beneath the free edge secures the nail to the fingertips. Eponychium – occupies the proximal border consist of stratum corneum. Nail matrix – cells divides mitotically to produce new nail cells – growth determine by the age, health and nutritional status. Average growth 1 mm per week. Slower growth in toe nail.  Skin Glands Sebaceous (oil) glands are connected to hair follicles. They secrete an oily substance called sebum (TG, cholesterol, protein & inorganic salts) which does 2 important things: Prevents dehydration of hair and skin Inhibits growth of certain bacteria Sebaceous gland  Skin Glands Sweat (sudoriferous) glands: Eccrine (merocrine) sweat glands Most numerous skin glands (skin of forehead, palms, soles). Watery perspiration that helps cool the body (thermoregulation) and eliminates small amounts of waste (urea, uric acid, ammonia). Apocrine sweat glands In groin, anal region, axilla, areola, bearded area in mature males Produce sweat that is thicker, milky, and contains fatty acids Scent glands that respond to stress and sexual stimulation Develop at puberty Much of body odor is due to apocrine sweat. Eccrine Apocrine Thermoregulation Yes No Eccrine sweat gland Emotional sweating Yes Yes Function After At Puberty Apocrine sweat gland birth  Skin Glands Ceruminous glands are modified sweat glands located in the ear canal. Along with nearby sebaceous glands, they are involved in producing a waxy secretion called cerumen (earwax) which provides a sticky barrier that prevents entry of foreign bodies into the ear canal. Functions of Skin 1. Thermoregulation - 2 ways liberating sweat at skin surface - in warm environment or during exercise, more sweat is secreted onto skin surface by the eccrine glands, where it is then is evaporated by excess body heat. adjusting the flow of blood in the dermis - in warm environment the arterioles dilates (vasodilation), which increases blood flow through the dermis and brings excess heat to the surface to be radiated to the environment. However, in cold environment body heat must be conserved, so arterioles constrict (vasoconstriction). This decreases the blood flow through the dermis and keeps heat within the core of the body. Functions of Skin 2. Blood reservoir – dermis houses extensive network of blood vessels that carry 8-10% of the blood flow in resting adults. 3. Protection ✓ keratin - protects microbes, abrasion, heat, chemicals, and tightly interlocked keratinocytes resists invasion by microbes. ✓ Lamella granules - release lipids that inhibit water evaporation – guarding against dehydration. ✓ Oil sebum from the sebaceous glands keeps skin and hairs from drying out and kills bacteria. ✓ acidic pH – retards the growth of some microbes. ✓ melanin – shield against damaging effect of UV ✓ Immunological protection- epidermal Langerhans cells alert the immune system to the presence by recognizing, then macrophages in the dermis phagocytosize bacteria and viruses Functions of Skin 4. Cutaneous sensations - sensation arise in the skin including tactile sensations – touch, pressure, vibration and tickling Thermal sensation- warmth and coolness 5. Excretion (eliminate substance –water, heat, salts, CO2, ammonia, urea) & absorption (fat soluble vitamin, certain drugs) 6. Synthesis of Vitamin D - Requires activation of a precursor molecule in the skin by small amount of UV rays in sunlight (10-15 min at least twice a week), enzymes in the kidney and liver then modify this activated molecule to produce calcitriol (active form of Vit D) that aids absorption of calcium from food.  Wound Healing ▪ Two kinds of wound-healing processes can occur, depending on the depth of the injury. Epidermal wound healing occurs following superficial wounds that affect only the epidermis. Return to normal function is the rule. Deep wound healing occurs when an injury extends to the dermis and subcutaneous layer. Loss of some function and development of scar tissue is the rule. Wound Healing Stop migrating due to contact inhibition  Wound Healing 4 phases: Inflammatory phase – a blood clot forms in the wound and loosely united the wound edges, macrophages phagocytize the microbes, mesenchymal cells develop into fibroblast. Migratory phase – clot becomes scab, epithelial beneath scab bridge the wound, fibroblast synthesize scar tissues (collagen fibers & glycoprotein), damage blood vessels regrow. Proliferation phase – extensive growth of epithelial cells beneath the scab, continued growth of blood vessels. Maturation phase – the scab slough off once epidermis reach normal thickness, collagen fiber become more organized, fibroblast decrease in number, and blood vessels restore to normal  Burns ▪ A burn is tissue damage caused by excessive heat, electricity, radioactivity, or corrosive chemicals that denature (break down) the proteins in the skin cells. Burns destroy some of the skin's important contributions to homeostasis—protection against microbial invasion, dehydration, and thermoregulation. ▪ Burns are graded according to their severity.  Burns ▪ A first-degree burn involves only the epidermis It is characterized by mild pain and erythema (redness) but no blisters and skin functions remain intact. Healing – 3-6 days, accompanied by flaking and peeling e.g. mild sun burn  Burns A second-degree burn destroys the epidermis and part of the dermis - some skin functions are lost. Redness, blister formation, edema, and pain In a blister, the epidermis separates from the dermis due to accumulation of tissue fluid between them If no infection, heals without skin grafting between 3-4 weeks, but may cause scarring.  Burns ▪ A third-degree burn is a full-thickness burn (destroys the epidermis, dermis, and subcutaneous layer). Most skin functions are lost, and the region is numb because sensory nerve endings have been destroyed. edema, and regeneration occurs slowly skin grafting may be required to promote healing and minimize scarring.  Burns According to the American Burn Association's classification of burn injury, a major burn includes: o 3 burns over 10% of body surface area; or o 2 burns over 25% of body surface area; or o Any 3 burns on the face, hands, feet, or perineum (which includes the anal and urogenital regions) When the burn area exceeds 70%, more than half the victims die.  Burns A quick means for estimating the surface area affected by a burn in an adult is the rule of nines: Count 9% if both the anterior and posterior surfaces of the head and neck are affected. Count 9% for both the anterior and posterior surfaces of each upper limb (total of 18% for both upper limbs). Count four times nine or 36% for both the anterior and posterior surfaces of the trunk, including the buttocks. Count 9% for the anterior and 9% for the posterior surfaces of each lower limb as far up as the buttocks (total of 36% for both lower limbs). Perineum – 1% Burns  Skin Cancer Skin cancer—induced by the UV rays of the sun Most common in fair-skinned people and the elderly One of the most common cancer Has one of the highest survival rates if detected and treated early Three types of skin cancer named for the epidermal cells in which they originate Basal cell carcinoma, squamous cell carcinoma, and malignant melanoma  Common Skin Disorders Alopecia Dermatitis Results in hair loss o Inflammation of skin or a rash Hirsutism Eczema Excessive body hair o Chronic dermatitis Folliculitis o Inflammation of hair follicles 24-49  Common Skin Disorders Herpes simplex Pediculosis Type 1 – cold sores Head lice Type 2 – genital Body lice Pubic lice Herpes zoster Shingles Psoriasis Inherited autoimmune Impetigo disorder Oozing skin lesions that eventually crust over 24-50  Common Skin Disorders Ringworm Scabies Tinea corporis Contagious skin Tinea capitis condition caused by Tinea pedis mites Warts Rosacea Harmless growths Dilation of small facial caused by a blood vessels papilloma virus 24-51