Transcript Chapter 5
The Integumentary System Chapter 5 The Skin epithelial and connective tissues working together for specific purposes the largest organ of the body 1.5 - 2 square meters 4 - 5 kg variable thickness: 1.5 mm to 4 mm Skin Physiology - Many Functions regulation of body temperature – insulator, radiator protection – a physical barrier and for water conservation sensation - varied sensory nerve endings communication – to other humans by signals/expressions and by touch excretion – in sweat = H2O, salts, small organic compounds (a minor contribution to excretion) immunity – certain phagocytes in the epidermis are important from the immune system for defense the dermis is a significant blood reservoir synthesis of Vitamin D – for calcium absorption The Structure of the Skin 2 Principal portions 1. Epidermis - epithelium 2. Dermis – areolar and dense irregular fibrous connective tissue Hypodermis “beneath the dermis” the subcutaneous layer next to: adipose layer or muscle or bone The Epidermis Stratified Squamous Epithelium 4 cell types 1. Keratinocytes - 90% filled with keratin (protein) waterproof barrier 2. Melanocytes - 8% produce melanin (pigment) pass melanin to keratinocytes 3. Langerhans cells phagocytes (from immune system) easily damaged by UV light 4. Merkel cells in deepest layer of hairless skin sensory transduction - touch Epidermal Cell Layers Stratum basale A single layer of cuboidal/columnar cells Stem cells, melanocytes, Merkel cells Stem cells keratinocytes, mitosis pushes the other layers to the top Stratum spinosum 8 to 10 layers of closely packed cells Cell junctions - spot desmosomes Langerhan’s cells Epidermal Cell Layers Stratum granulosum 3-5 layers of flattened, with keratohyaline granules beginning breakdown of nucleus, cell death initiated Stratum lucidum only in thick skin (palms, feet) 3-5 layers of clear, flat dead cells with keratin Stratum corneum 20-30 layers of flattened, dead, keratin-filled cells continuously shed and replaced 2-4 weeks for each cell to form and to move from the stratum basale to the surface Epidermal Histology Stratum Corneum Stratum Granulosum Stratum Spinosum Stratum Basale The Dermis - General primarily irregular dense fibrous conn. tissue variable thickness - thicker on palms and soles; thicker on dorsal surfaces rather than on ventral; thicker on lateral surfaces than on medial surfaces few cells present - fibroblasts, macrophages, adipocytes matrix thick with many protein fibers: collagen, elastin, reticular the location for blood vessels, nerves and sensory receptors, glands, hair follicles Dermis - Structure Papillary region (layer) - outer layer - 20% areolar connective tissue, elastic fibers dermal papillae – mound-like projections to increase the surface area for nutrition from capillaries some papillae contain Meissner's corpuscles (for light touch) Dermis – Structure (cont.) Reticular region 80% dense, irregular connective tissue collagen, elastic fibers in a network surrounding the various cells fibers give strength, elasticity, extensibility tears in reticular region - "stretch marks“ - long straight red or white streaks Three Skin Pigments 1. Melanin - yellow to black Made by melanocytes Common in mucous membranes, penis, nipples, areolas, face, extremities The number of melanocytes is similar in all races – but the amount and type of melanin produced and distributed to the keratinocytes varies Freckles, livers spots - melanocyte clusters Melanin is synthesized from tyrosine (amino acid) UV radiation increases enzyme activity (negative feedback) melanin production protects the body against UV radiation Three Skin Pigments albino vitiligo Melanin Pathologies Albinism - inability to produce melanin; cannot breakdown tyrosine, no melanin, inborn error of metabolism; recessive trait Vitiligo - partial/complete loss of melanocytes from skin patches Three Skin Pigments 2. Carotene - yellow-orange pigment in the dermis Gives egg yolks, carrots, their color Used in the synthesis of a vision pigment Persons of Asian extraction have carotene in their stratum corneum, in the fatty areas of the dermis and in their subcutaneous layers 3. Hemoglobin – because the skin is translucent Caucasian skin – tinted red to pink depending on dermal capillary blood flow Skin Color Skin color Blood is bright red when carrying oxygen, dark red/purple when deoxygenated; the skin appears to have a blue or green or purple tinge depending on the individual The relative color of skin and exposed mucous membranes can give clues to a person’s oxygenation status Skin Color – Clinical Terminology Erythema skin redness exercise, embarrassment, high blood pressure, certain drugs, inflammation, etc. Pallor pale cold temperatures, stress or anemia Erythema: Parvovirus / “fifth disease” Cyanosis bluish, no oxygen babies not breathing, heavy smokers/emphysema Pernicious anemia Cyanosis Skin Color – Clinical Terminology Jaundice yellow/orange after internal hemorrhage liver problems disturbing the breakdown & removal of RBC's Bronzing Metallic appearance of skin Addisons disease – hypofunction of adrenal cortex Black and blue marks, bruises (contusions) Skin Pathologies Basal cell carcinoma From stratum basale Least malignant - 99% full cure Squamous cell carcinoma From stratum spinosum Prognosis is good if removed early Melanoma Melanocyte cancer Highly metastatic Resistant to chemotherapy ABCD Rule Asymmetry Border irregularity Color: several present Diameter: greater than 6 mm Skin Grafts Sometimes when the is skin severely damaged, it cannot regenerate itself Success is dependent on the site of origin of the transplanted tissue autograft from the same person donated from a different site can be tissue cultured first Autograft to knee isograft - identical twins homograft - skin from another human heterograft - skin from an animal Epidermal Derivatives: Hair = Pili Hair functions protection increase surface area for evaporative heat loss; increased length (scalp) for sunburn and heatstroke eyebrows, eyelashes - insects, foreign particles nostril hair – same ear hair - same mechanical dry lubricant for limb movements secondary sexual characteristic to attract mates touch receptors respond to changes in position rate of growth & replacement affected by many things: heredity, diet, illness, fever, blood loss, surgery, drugs, chemotherapy Hair Anatomy Shaft medulla - inner layer cortex - middle layer, pigments, air spaces cuticle - outermost layer, hard keratin Root similar to shaft, but within dermis Follicle - surrounds root Sheath - supports shaft & root Bulb - enlarged layered structure at base where hair is generated papilla - areolar connective tissue, blood vessels supply nutrients matrix - germination layer of papilla (stratum basale) builds hair shaft Sebaceous glands – release oil Arrector Pili – smooth muscle Hair Follicle Hair Color Brown, black - melanin deposited from the matrix of the bulb into the shaft Red, blond - variants of melanin with iron, sulfur in the molecule Grey – some loss of melanocytes reduces melanin deposition White - air bubbles accumulate in the cortex Hair and Hormones Testosterone Secretion increases at puberty Male pattern of hair growth and distribution begins Hirsutism excess testosterone production, tumor or hormonal imbalance excess hair production in females or prepubertal males Hair and Hormones Male pattern baldness Genetic predisposition – sex-linked trait – testosterone inhibits scalp hair growth in these individuals Finasteride (Propecia) - anti-testosterone agent must be taken for remainder of life Minoxidil (Rogaine) anti-hypertensive medicine widens blood vessels, increases blood flow topically (daily) promotes growth in people with reduced hair growth (not much but some); but not in truly bald individuals Male Pattern Baldness Skin Glands Sebaceous (Oil) Glands Sudoriferous (Sweat) Glands 1. Sebaceous (Oil) Glands Connected to hair follicles; located in the dermis Most secrete directly into follicles; some directly onto the skin Gland shape differs depending on location Holocrine gland Secrete sebum (oil) fats, cholesterol, proteins, inorganic salts keeps hair from drying prevents water evaporation from skin keeps skin soft, supple inhibits growth of many bacteria 2. Sudoriferous (Sweat) Glands Two types of typical glands 1. eccrine sweat glands the majority; especially abundant on the palms and soles and the forehead the secretory portion of the gland is located in the dermis Sudoriferous (Sweat) Glands Two types of typical glands 2. apocrine sweat glands located mainly in the axillary and anogenital regions, and the areolae of the breast secretory portion is located in the dermis or the subcutaneous region; secrete into hair follicles secrete more during emotional stress, sexual arousal a merocrine process http://faculty.une.edu/com/abell/histo/histolab3g.htm Modified Sudoriferous (Sweat) Glands Two types of modified sweat glands 1. Ceruminous glands – protect against ectoparasites (bugs) produce a bitter waxy secretion (cerumen) open into the external auditory meatus (ear canal) or into local sebaceous glands 2. Mammary glands – highly specialized for milk production hormonally regulated by estrogens, prolactin, and oxytocin Sweat produced primarily by the eccrine glands water, salts, urea, uric acid, amino acids, ammonia, sugar lactic acid, ascorbic acid – a plasma filtrate pheromones for sexual attraction pH between 4 and 6 salty and acidic solution inhibits most bacterial growth maintain body temperature, but insignificant for waste removal Glands Pathology CF = Cystic Fibrosis patients have an autosomal recessive inborn error of metabolism altered chloride transport which alters the characteristics of most glandular secretions detected in infants with a simple chloride sweat test – CF babies have elevated sweat chloride values primarily affects the respiratory and digestive systems with thick clogging secretions average lifespan approximately 30 years ~1/3900 newborns ~3/100 adults are carriers Nails tightly packed, hard, keratinized cells nail matrix - under root of nail site of nail growth transforms normal skin cells into nail cells which push forward 1mm/week in fingers; slower in toes the longer the finger the greater the growth rate Good Day!