Chapter 5 - Lecture notes ch 5 PDF

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Chapter 5: The Integumentary System 

An organ system consists of: o Skin o Hair o Nails o Sweat glands o Sebaceous (oil) glands Functions of the Skin 1) Protection a. Chemical- sweat, melanin b. Physical- multiple layers, damaged layers can easily be replaced c. Biological barrier- immune cells 2) Body temperature regulation 3) Cutaneous sensation a. Skin knows what’s happening on the outside 4) Metabolic function a. Chemical conversion 5) Blood reservoir 6) Secretion/excretion The Skin (integument) is Composed of 2 Distinct Layers 1. Epidermis a. Stratified squamous epithelium 2. Dermis a. Connective tissues proper 3. Hypodermis is not part of skin The Epidermis is Composed of 4 Different Types of Cells Keratinocytes  Produce keratin  Connected by desmosomes  Arise from a deeper mitotically active layer  Dead at surface-turnover 25-45 days Dendritic (Langerhans) Cells  Macrophage cells  Active immune system Tactile (Merkel) Cells  Epidermal-dermal junction  Associated with sensory nerve endings  Receptor for touch Melanocytes  Synthesize melanin  Found in deepest layer

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Form pigment shield to protect nucleus from sunlight

The Epidermis May Have 4 or 5 Different Layers Stratum Basale  Deepest layer, attached to dermis single row of youngest keratinocytes Melanocyte cell Stratum Spinosum  Several layers thick, flat irregular shaped keratinocytes, desmosome attachments Stratum Granulosum  1-5 layers thick  nuclei and organelles disintegrate  accumulate keratohylaine granules Stratum Carenum  20-30 layers thick of anuleate cells  keratinized dead cells, glycolipid between cells The Dermis has 2 Layers of Connective Tissue Which Include Other Cell Types and Structures 1. dermal papillae 2. reticular layer of dermis Papillary Layer  Superficial layer of areolar connective tissue  Rich in blood vessels  Loose fibers allow phagocytes to patrol for microorganisms  Dermal papillae: superficial region of dermis that sends fingerlike projections up into epidermis o Projections contains capillary loops, free nerve endings, and touch receptors  In thick skin, dermal papillae lie on top of dermal ridges, which give rise to epidermal ridges o Collectively ridges are called friction ridges  Enhance gripping ability  Contribute to sense of touch  Swear pores in ridges leave unique fingerprint pattern Reticular Layer  Makes up ~80% of dermal thickness  Consists of coarse, dense irregular connective tissue  Cutaneous plexus: network of blood vessels between reticular layer and hypodermis  Cleavage (tension) lines in reticular layer are caused by many collagen fibers running parallel to skin surface o Externally invisible o Important to surgeons because incisions parallel to cleavage lines heal more readily Cleavage Lines  The arrangement of the collagen fibers within a network  Incisions made parallel to cleavage lines heal more readily  Flexure lines

Landmarks and orientation Run longitudinally in the skin of head and limbs and in circular patterns around the neck and truck Skin Color  Melanin: made by melanocytes, skin color differences due to amount and form of melanin  Carotene: yellow to orange, palms and soles  Hemoglobin: Caucasians skin is more transparent, so hemoglobin shows through Skin Appendages Are derivatives of epidermis with a role of maintaining homeostasis  Sweat Glands (sudoriferous glands) o found everywhere except nipples and external genitalia  Eccrine (merocrine) o Most abundant o High density on palms, sole of foot and forehead o Secrete sweat via exocytosis  Hypotonic blood filtrate  99% H2O, some NaCl and other materials  acidic (pH 4-6)  Apocrine o Confined to axillary and anogenital area, little role in thermoregulation o Larger, ducts empty into hair follicles o Similarity to sexual scent gland- sexual foreplay increases activity Sebaceous (oil) Glands Puke to Keep Your Skin Soft and Smooth  Alveolar glands o Everywhere except palms and soles of feet  Secrete sebum (holocrine) o Lipid and cell fragments o Function  Lubrication  Skin: slowing water loss  Hair: prevents brittleness  Bactericidal function o Stimulated by androgens Acne Acne develops when:  Hair follicles become plugged with oil and dead skin cells  Bacteria then triggers: o Inflammation o Infection  Stages of acne o Normal follicle o Open comedo (blackhead) o Closed comedo (whitehead) o Papule  

o Pustule Why Do We Have Hair?  Hair is distributed everywhere on your skin except o Palms, soles, lips o Nipples and portions of the external genitalia Hair is filamentous strands of dead keratinized cells  Hair: o Shaft projecting from the skin o Root embedded in the dermis o Predominately dead keratinized cells  Cells contain hair keratin o Different from soft keratin in the epidermis  Consists of 3 layers of cells o Medulla: central core, large cells and air space o Cortex: layers of flattened cells o Cuticle: single layer of cells The Hair Follicle is Where the Action is!

Cross-sectional view of the Hair Follicle

Hair Care- a multibillion dollar business  Types of hair: o Terminal: eyebrow and scalp, longer and coarser  Androgens- hormone that signals body to create terminal hair instead vellus hair o Vellus: body hair of children and adult females, fine  Growth – 2.5mm/week o Growth cycles- active/dormant  Lose~ 90 hairs per days  Alopecia- hair thinning and baldness with age o Genetically determined and sex- influenced condition o Male pattern baldness- caused by follicular response to DHT  Dihydrotestosterone Not All Skin Cancers are Created Equal  Basal Cell Carcinoma o Least malignant o Stratum Basale cells proliferate and invade dermis o Sun exposed areas more common  Squamous Cell Carcinoma o Keratinocytes of the stratum spinosum o Grows rapidly, metastasizes, good outcome if caught early  Melanoma

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Most dangerous, highly metastatic, chemotherapy resistant Caner of melanocytes 1/3 from pre-existing moles 2 types of growth  radial or vertical

A Simple Rule of Thumb to Identify Skin Cancer ABCD Rule  Asymmetry- two sides don’t match  Border irregularity- indentations in border  Color- pigmented spot contains several colors  Diameter- larger than 6mm diameter (pencil eraser) Classification of Tissue Injury by Burns  First-degree- only the epidermis is damaged o Symptoms include localized redness, swelling and pain  Second-degree- epidermis and upper regions of dermis are damaged o Symptoms mimic first-degree burns but blisters also appear  Third-degree- entire thickness of the skin is damaged o Burned area appears gray-white, cherry red or black, there is no initial edema or pain (since nerve endings are destroyed) A Simple Rule of Thumb to Quantify Area Burned  Burned considered critical if: o Over 25% of the body has second degree burns o Over 10% of the body has third degree burns o There are third degree burners on face, hands or feet  Rules of Nines o Tools to estimate body fluid lost  Divide body into 11 regions (9%)...