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Perspiration Insensible perspiration: –interstitial fluid lost by evaporation through the stratum...

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Perspiration Insensible perspiration: – interstitial fluid lost by evaporation through the stratum corneum Sensible perspiration: – water excreted by sweat glands
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Perspiration

• Insensible perspiration:– interstitial fluid lost by evaporation

through the stratum corneum

• Sensible perspiration: – water excreted by sweat glands

Water Loss Through Skin

• Dehydration results:– from damage to stratum corneum, e.g., burns and blisters (insensible perspiration)

– from immersion in hypertonic solution, e.g., seawater (osmosis)

Water Gain Through Skin

• Hydration:– results from immersion in hypotonic

solution, e.g., freshwater (osmosis)– causes stretching and wrinkling skin

Skin Color

• Skin color depends on:– the pigments carotene and melanin– blood circulation (red cells)

Melanocytes

• Skin color depends on melanin production, not number of melanocytes

Capillaries and Skin Color

• Oxygenated red blood contributes to skin color: – blood vessels dilate from heat, skin

reddens– blood flow decreases, skin pales

Characteristics of Dermis

• Strong, due to collagen fibers• Elastic, due to elastic fibers• Flexible (skin turgor)

Skin Damage

• Sagging and wrinkles (reduced skin elasticity) are caused by:– dehydration– age– hormonal changes– UV exposure

Stretch Marks

• Thickened tissue resulting from: – excessive stretching of skin due to:

• pregnancy• weight gain

Lines of Cleavage

• Collagen and elastic fibers in the dermis: – are arranged in parallel bundles– resist force in a specific direction

Clinical Importance

• Lines of cleavage establish important patterns:– a parallel cut remains shut, heals well– a cut across (right angle) pulls open

and scars

Lines of Cleavage

Figure 5–7

Nerves

• Nerve fibers in skin control:– blood flow– gland secretions– sensory receptors

• Tactile disks called Merkel cells

The Hypodermis

• The subcutaneous layer or hypodermis: – lies below the integument– stabilizes the skin– allows separate movement – not a skin layer

Structure of the Hypodermis

• The subcutaneous layer is:– made of elastic areolar and adipose

tissues– connected to the reticular layer of

integument by connective tissue fibers

Clinical Importance

• Subcutaneous layer:– has few capillaries and no vital organs– is the site of subcutaneous injections

using hypodermic needles

Adipose Tissue

• Deposits of subcutaneous fat:– have distribution pattern determined

by hormones– are reduced by cosmetic liposuction

Location of Hair

• The human body is covered with hair, except:– palms– soles– lips– portions of external genitalia

Functions of Hair

• Protects and insulates• Guards openings against particles

and insects• Is sensitive to very light touch

The Hair Follicle

• Is located deep in dermis• Produces nonliving hairs • Is wrapped in a dense connective-

tissue sheath• Base is surrounded by sensory

nerves (root hair plexus)

Layers in a Hair

• Medulla:– the central core

• Cortex:– the middle layer

• Cuticle– the surface layer

Types of Hairs

• Vellus hairs: – soft, fine – cover body surface

• Terminal hairs: – heavy, pigmented– head and eyebrows– other parts of body after puberty

Structure of Hair

Hair Color

• Produced by melanocytes at the hair papilla

• Determined by genes

Structure of Fingernail

Repair of Localized Injuries to the Skin: Step 1

• Bleeding occurs• Mast cells

trigger inflammatory response

Figure 5–13 (Step 1)

Repair of Localized Injuries to the Skin: Step 2

• A scab stabilizes and protects the area

Figure 5–13 (Step 2)

The Inflammatory Response

• Germinative cells migrate around the wound

• Macrophages clean the area• Fibroblasts and endothelial cells

move in, producing granulation tissue

Repair of Localized Injuries to the Skin: Step 3

• Fibroblasts produce scar tissue

• Inflammation decreases, clot disintegrates

Figure 5–13 (Step 3)

Repair of Localized Injuries to the Skin: Step 4

• Fibroblasts strengthen scar tissue

• A raised keloid forms

Figure 5–13 (Step 4)

Effects of Aging

• Epidermal thinning• Decreased numbers of Langerhans

cells

• Decreased vitamin D3 production

• Decreased melanocyte activity• Decreased glandular activity

(sweat and oil glands)

Effects of Aging

• Reduced blood supply• Decreased function of hair follicles• Reduction of elastic fibers• Decreased hormone levels• Slower repair rate

Importance of the Integumentary System

• Protects and interacts with all organ systems

• Changes in skin appearance are used to diagnose disorders in other systems


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