5 - Dr. Jerry Cronin

5 - Dr. Jerry Cronin

Follicle wall Connective tissue root sheath Glassy membrane External epithelial root sheath Internal epithelial root sheath Hair Hair shaft Arrector

pili Sebaceous gland Hair root Cuticle Cortex Medulla (b) Photomicrograph of a cross section of a hair and hair follicle (250x)

Hair bulb Copyright 2010 Pearson Education, Inc. Figure 5.6b Hair Follicle Extends from the epidermal surface into dermis Two-layered wall: outer connective tissue root sheath, inner epithelial root sheath Hair bulb: expanded deep end Copyright 2010 Pearson Education, Inc.

Hair Follicle Hair follicle receptor (root hair plexus) Sensory nerve endings around each hair bulb Stimulated by bending a hair Arrector pili Smooth muscle attached to follicle Responsible for goose bumps Copyright 2010 Pearson Education, Inc. Hair shaft

Arrector pili Sebaceous gland Hair root Hair bulb Follicle wall Connective tissue root sheath Glassy membrane External epithelial root sheath Internal epithelial root sheath Hair root

Cuticle Cortex Medulla Hair matrix Hair papilla Melanocyte (c) Copyright 2010 Pearson Education, Inc. Subcutaneous adipose tissue Diagram of a longitudinal view of the expanded hair bulb of the follicle, which encloses the matrix

Figure 5.6c Follicle wall Connective tissue root sheath Glassy membrane External epithelial root sheath Internal epithelial root sheath Hair root Cuticle Cortex

Medulla Hair matrix Hair papilla Subcutaneous adipose tissue Copyright 2010 Pearson Education, Inc. Hair shaft Arrector pili

Sebaceous gland Hair root Hair bulb (d) Photomicrograph of longitudinal view of the hair bulb in the follicle (160x) Figure 5.6d Types of Hair Velluspale, fine body hair of children and adult females Terminalcoarse, long hair of eyebrows,

scalp, axillary, and pubic regions (and face and neck of males) Copyright 2010 Pearson Education, Inc. Types of Hair Hair Growth Growth phase (weeks to years) followed by regressive stage and resting phase (13 months) Growth phase varies (610 years in scalp, 34 months in eyebrows)

Copyright 2010 Pearson Education, Inc. Hair Thinning and Baldness Alopeciahair thinning in both sexes after age 40 True (frank) baldness Genetically determined and sex-influenced condition Male pattern baldness is caused by follicular response to DHT Copyright 2010 Pearson Education, Inc.

Structure of a Nail Scalelike modification of the epidermis on the distal, dorsal surface of fingers and toes Copyright 2010 Pearson Education, Inc. Lateral nail fold Lunule (a) Free edge Body

of nail of nail Eponychium (cuticle) Nail bed Proximal nail fold Root of nail Nail matrix

(b) Hyponychium Copyright 2010 Pearson Education, Inc. Phalanx (bone of fingertip) Figure 5.7 Functions of the Integumentary System 1. Protectionthree types of barriers Chemical Low pH secretions (acid mantle) and defensins retard bacterial activity

Copyright 2010 Pearson Education, Inc. Functions of the Integumentary System Physical/mechanical barriers Keratin and glycolipids block most water and water- soluble substances Limited penetration of skin by lipid-soluble substances, plant oleoresins (e.g., poison ivy), organic solvents, salts of heavy metals, some drugs Biological barriers Dendritic cells, macrophages, and DNA

Copyright 2010 Pearson Education, Inc. Functions of the Integumentary System 2. Body temperature regulation ~500 ml/day of routine insensible perspiration (at normal body temperature) At elevated temperature, dilation of dermal

vessels and increased sweat gland activity (sensible perspirations) cool the body 3. Cutaneous sensations Temperature, touch, and pain Copyright 2010 Pearson Education, Inc. Functions of the Integumentary System 4. Metabolic functions

Synthesis of vitamin D precursor and collagenase Chemical conversion of carcinogens and some hormones 5. Blood reservoirup to 5% of bodys blood volume 6. Excretionnitrogenous wastes and salt in sweat

Copyright 2010 Pearson Education, Inc. Skin Cancer Most skin tumors are benign (do not metastasize) Risk factors Overexposure to UV radiation Frequent irritation of the skin Some skin lotions contain enzymes in liposomes that can fix damaged DNA

Copyright 2010 Pearson Education, Inc. Skin Cancer Three major types: Basal cell carcinoma Least malignant, most common Squamous cell carcinoma Second most common Melanoma Most dangerous Copyright 2010 Pearson Education, Inc.

Basal Cell Carcinoma Stratum basale cells proliferate and slowly invade dermis and hypodermis Cured by surgical excision in 99% of cases Copyright 2010 Pearson Education, Inc. Copyright 2010 Pearson Education, Inc. Figure 5.8a Squamous Cell Carcinoma Involves keratinocytes of stratum spinosum

Most common on scalp, ears, lower lip, and hands Good prognosis if treated by radiation therapy or removed surgically Copyright 2010 Pearson Education, Inc. Copyright 2010 Pearson Education, Inc. Figure 5.8b Melanoma Involves melanocytes

Highly metastatic and resistant to chemotherapy Treated by wide surgical excision accompanied by immunotherapy Copyright 2010 Pearson Education, Inc. Melanoma Characteristics (ABCD rule) A: Asymmetry; the two sides of the pigmented area do not match B: Border exhibits indentations C: Color is black, brown, tan, and sometimes red

or blue D: Diameter is larger than 6 mm (size of a pencil eraser) Copyright 2010 Pearson Education, Inc. Copyright 2010 Pearson Education, Inc. Figure 5.8c Burns Heat, electricity, radiation, certain chemicals

Burn (tissue damage, denatured protein, cell death) Immediate threat: Dehydration and electrolyte imbalance, leading to renal shutdown and circulatory shock Copyright 2010 Pearson Education, Inc. Rule of Nines Used to estimate the volume of fluid loss from burns Copyright 2010 Pearson Education, Inc.

4 1/2 % Totals Anterior and posterior head and neck, 9% Anterior and posterior upper limbs, 18% Anterior 4 1/2 % trunk, 4 1/2 % Anterior and posterior trunk, 36% 18%

9% 9% (Perineum, 1%) Anterior and posterior lower limbs, 36% 100% Copyright 2010 Pearson Education, Inc. Figure 5.9 Partial-Thickness Burns

First degree Epidermal damage only Localized redness, edema (swelling), and pain Second degree Epidermal and upper dermal damage Blisters appear Copyright 2010 Pearson Education, Inc. 1st degree burn

2nd degree burn (a) Skin bearing partial thickness burn (1st and 2nd degree burns) Copyright 2010 Pearson Education, Inc. Figure 5.10a Full-Thickness Burns Third degree

Entire thickness of skin damaged Gray-white, cherry red, or black No initial edema or pain (nerve endings destroyed) Skin grafting usually necessary Copyright 2010 Pearson Education, Inc. 3rd degree burn (b) Skin bearing full

thickness burn (3rd degree burn) Copyright 2010 Pearson Education, Inc. Figure 5.10b Severity of Burns Critical if: >25% of the body has second-degree burns >10% of the body has third-degree burns Face, hands, or feet bear third-degree burns

Copyright 2010 Pearson Education, Inc. Developmental Aspects: Fetal Ectoderm epidermis Mesoderm dermis and hypodermis Lanugo coat: covering of delicate hairs in 5th and 6th month Vernix caseosa: sebaceous gland secretion; protects skin of fetus Copyright 2010 Pearson Education, Inc. Developmental Aspects: Adolescent to

Adult Sebaceous gland activity increases Effects of cumulative environmental assaults show after age 30 Scaling and dermatitis become more common Copyright 2010 Pearson Education, Inc. Developmental Aspects: Old Age Epidermal replacement slows, skin becomes thin, dry, and itchy Subcutaneous fat and elasticity decrease, leading to cold intolerance and wrinkles

Increased risk of cancer due to decreased numbers of melanocytes and dendritic cells Copyright 2010 Pearson Education, Inc.

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