2 Support and Movement Fundamentals of Anatomy & Physiology Unit Frederic H. Martini PowerPoint® Lecture Slides prepared by Professor Albia Dugger, Miami–Dade College, Miami, FL Professor Robert R. Speed, Ph.D., Wallace Community College, Dothan, AL Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Chapter 5: The Integumentary System

What are the structures and functions of the integumentary system?

Size of the Integument The integument is the largest system of the body: 16% of body weight 1.5 to 2 m2 in area

Parts of the Integument The integument is made up of 2 parts: cutaneous membrane (skin) accessory structures

Parts of the Integumentary System Figure 5–1

Parts of the Cutaneous Membrane Outer epidermis: superficial epithelium (epithelial tissues) Inner dermis: connective tissues

Accessory Structures Originate in the dermis Extend through the epidermis to skin surface: hair nails multicellular exocrine glands

Connections Circulatory system: Nervous system: blood vessels in the dermis Nervous system: sensory receptors for pain, touch, and temperature

What is the relationship between the integument and subcutaneous layer?

The Subcutaneous Layer Subcutaneous layer (superficial fascia or hypodermis): loose connective tissue below the dermis location of hypodermic injections

Functions of Skin Protects underlying tissues and organs Excretes salts, water, and organic wastes (glands) Maintains body temperature (insulation and evaporation)

Functions of Skin Synthesizes vitamin D3 Stores lipids Detects touch, pressure, pain, and temperature

What are the main structures and functions of the epidermis?

Epidermis Avascular stratified squamous epithelium Nutrients and oxygen diffuse from capillaries in the dermis

Organization of the Epidermis Figure 5–2

Cells of the Epidermis Keratinocytes: contain large amounts of keratin the most abundant cells in the epidermis

Thin Skin Covers most of the body Has 4 layers of keratinocytes

Thick Skin Covers the palms of the hands and soles of the feet Has 5 layers of keratinocytes

Structures of the Epidermis The 5 strata of keratinocytes in thick skin Figure 5–3

Layers of the Epidermis From basal lamina to free surface: stratum germinativum stratum spinosum stratum granulosum stratum lucidum stratum corneum

Stratum Germinativum The “germinative layer”: has many germinative (stem) cells or basal cells is attached to basal lamina by hemidesmosomes forms a strong bond between epidermis and dermis

Structures of Stratum Germinativum Epidermal ridges (e.g., fingerprints) Dermal papillae (tiny mounds): increase the area of basal lamina strengthen attachment between epidermis and dermis

Ridges and Ducts Figure 5–4

Cells of Stratum Germinativum Merkel cells: found in hairless skin respond to touch (trigger nervous system) Melanocytes: contain the pigment melanin scattered throughout stratum germinativum

Stratum Spinosum The “spiny layer”: produced by division of stratum germinosum 8–10 layers of keratinocytes bound by desmosomes cells shrink until cytoskeletons stick out (spiny)

Cells of Stratum Spinosum Continue to divide, increasing thickness of epithelium Contain Langerhans cells, active in immune response

Stratum Granulosum The “grainy layer” Stops dividing, starts producing: keratin: a tough, fibrous protein makes up hair and nails keratohyalin dense granules cross-link keratin fibers

Cells of Stratum Granulosum Produce protein fibers Dehydrate and die Create tightly interlocked layer of keratin surrounded by keratohyalin

Stratum Lucidum The “clear layer”: found only in thick skin covers stratum granulosum

Cells of Stratum Lucida Flat Dense Filled with keratin

Stratum Corneum The “horn layer”: exposed surface of skin 15 to 30 layers of keratinized cells water resistant shed and replaced every 2 weeks

Keratinization The formation of a layer of dead, protective cells filled with keratin Occurs on all exposed skin surfaces except eyes

Skin Life Cycle It takes 15–30 days for a cell to move from stratum germinosum to stratum corneum

Perspiration Insensible perspiration: Sensible 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

What causes different skin colors?

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

Carotene Orange-yellow pigment Found in orange vegetables Accumulates in epidermal cells and fatty tissues of the dermis Can be converted to vitamin A

Melanin Yellow-brown or black pigment Produced by melanocytes in stratum germinativum Stored in transport vesicles (melanosomes) Transferred to keratinocytes

Function of Melanocytes Melanin protects skin from sun damage Ultraviolet (UV) radiation: causes DNA mutations and burns which lead to cancer and wrinkles

Melanocytes Figure 5–5

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

Cyanosis Bluish skin tint Caused by severe reduction in blood flow or oxygenation

Illness and Skin Color Jaundice: Addison’s disease: buildup of bile produced by liver yellow color Addison’s disease: and other diseases of pituitary gland skin darkening

Illness and Skin Color Vitiglio: loss of melanocytes loss of color

Vitamin D Epidermal cells produce cholecalciferol (vitamin D3): in the presence of UV radiation Liver and kidneys convert vitamin D into calcitriol: to aid absorption of calcium and phosphorus

Vitamin D Insufficient vitamin D: can cause rickets

Epidermal Growth Factor (EGF) Is a powerful peptide growth factor Is produced by glands (salivary and duodenum) Is used in laboratories to grow skin grafts

Functions of EGF Promotes division of germinative cells Accelerates keratin production Stimulates epidermal repair Stimulates glandular secretion

KEY CONCEPT The epidermis: is a multilayered, flexible, self-repairing barrier prevents fluid loss protects from UV radiation produces vitamin D3 resists abrasion, chemicals, and pathogens

What are the structures and functions of the dermis?

The Dermis Is located between epidermis and subcutaneous layer Anchors epidermal accessory structures (hair follicles, sweat glands) Has 2 components: outer papillary layer deep reticular layer

The Papillary Layer Consists of areolar tissue Contains smaller capillaries, lymphatics, and sensory neurons Has dermal papillae projecting between epidermal ridges

The Reticular Layer Consists of dense irregular connective tissue Contains larger blood vessels, lymph vessels, and nerve fibers Contains collagen and elastic fibers Contains connective tissue proper

Dermatitis An inflammation of the papillary layer Caused by infection, radiation, mechanical irritation, or chemicals (e.g., poison ivy) Characterized by itch or pain

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

Skin Cancer Figure 5–6

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

Dermal Circulation Figure 5–8

Arteries Cutaneous plexus: Papillary plexus: a network of arteries along the reticular layer Papillary plexus: capillary network from small arteries in papillary layer

Veins Venous plexus: Contusion: capillary return deep to the papillary plexus Contusion: damage to blood vessels resulting in “black and blue” bruising

Nerves Nerve fibers in skin control: blood flow gland secretions sensory receptors Tactile disks monitor Merkel cells

KEY CONCEPT The dermis: provides mechanical strength, flexibility and protection is highly vascularized contains many types of sensory receptors

What are the structures and functions of the subcutaneous layer?

The Hypodermis The subcutaneous layer or hypodermis: lies below the integument stabilizes the skin allows separate movement

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

Integumentary Accessory Structures Hair, hair follicles, sebaceous glands, sweat glands, and nails: are derived from embryonic epidermis are located in dermis project through the skin surface

What determines hair growth, texture, and color?

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)

Structures of Hair and Follicles Figure 5–9a

Accessory Structures of Hair Arrector pili: involuntary smooth muscle causes hairs to stand up produces “goose bumps” Sebaceous glands: lubricate the hair control bacteria

Regions of the Hair Hair root: Hair shaft: lower part of the hair attached to the integument Hair shaft: upper part of the hair not attached to the integument

Inside the Follicle Figure 5–9b

Keratin As hair is produced, it is keratinized: medulla contains flexible soft keratin cortex and cuticle contain stiff hard keratin

Hair Growth Cycle Growing hair: Club hair: is firmly attached to matrix Club hair: is not growing is attached to an inactive follicle

Hair Growth Cycle New hair growth cycle: follicle becomes active produces new hair club hair is shed

Types of Hairs Vellus hairs: Terminal hairs: soft, fine cover body surface Terminal hairs: heavy, pigmented head and eyebrows other parts of body after puberty

Hair Color Produced by melanocytes at the hair papilla Determined by genes

What are the skin glands and secretions?

Exocrine Glands Sebaceous glands (oil glands): Sweat glands: holocrine glands secrete sebum Sweat glands: merocrine glands watery secretions

Types of Sebaceous Glands Simple branched alveolar glands: associated with hair follicles Sebaceous follicles: discharge directly onto skin surface

Sebaceous Glands Figure 5–10

Sebum Contains lipids and other ingredients Lubricates and protects the epidermis Inhibits bacteria

What are the functions of sweat glands?

Types of Sweat Glands Apocrine: Merocrine: found in armpits, around nipples, and groin Merocrine: widely distributed on body surface especially on palms and soles

Apocrine Sweat Gland Figure 5–11a

Apocrine Sweat Glands Merocrine secretions, not apocrine Associated with hair follicles Produce sticky, cloudy secretions Break down and cause odors

Merocrine Sweat Glands Also called eccrine glands: coiled, tubular glands discharge directly onto skin surface sensible perspiration water, salts, and organic compounds

Merocrine Sweat Gland Figure 5–11b

Functions of Merocrine Sweat Cools skin Excretes water and electrolytes Flushes microorganisms and harmful chemicals from skin

Other Integumentary Glands Mammary glands: produce milk Ceruminous glands: protect the eardrum produce cerumen (earwax)

Homeostasis Thermoregulation: is the main function of sensible perspiration works with cardiovascular system regulates body temperature

KEY CONCEPT Skin plays a major role in controlling body temperature: acts as a radiator removes heat from dermal circulation works by evaporation of sensible perspiration

What is the structure of nails, and how do they grow?

Nail Functions Nails protect fingers and toes: made of dead cells packed with keratin metabolic disorders can change nail structure

Structure of a Nail Figure 5–12

How does injured skin respond and repair itself?

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 PLAY Integumentary Repair Figure 5–13 (Step 4)

Rule of Nines To estimate burn damage, surface area is divided into multiples of 9 Figure 5–14

What are the effects of aging on the skin?

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

How does the integumentary system work with other systems?

Importance of the Integumentary System Protects and interacts with all organ systems Changes in skin appearance are used to diagnose disorders in other systems

Interactions with the Integumentary System Figure 5–15

SUMMARY (1 of 12) Division of: integument into epidermis and dermis epidermis into thin skin and thick skin

SUMMARY (2 of 12) Layers of the epidermis: stratum germinosum stratum spinosum stratum lucidum stratum corneum

SUMMARY (3 of 12) Roles of epidermal ridges and dermal papillae

SUMMARY (4 of 12) Functions of specialized cells: Langerhans cells Merkel cells

SUMMARY (5 of 12) Skin pigments: carotene melanin

SUMMARY (6 of 12) Metabolic functions of epidermis: vitamin D3 epidermal growth factor

SUMMARY (7 of 12) Divisions of the dermis: papillary layer reticular layer

SUMMARY (8 of 12) Mobility of the dermis: stretch marks lines of cleavage

SUMMARY (9 of 12) Blood supply of the dermis: cutaneous plexus papillary plexus

SUMMARY (10 of 12) Role of the subcutaneous layer Structure of hair and hair follicles

SUMMARY (11 of 12) Glands of the skin: sebaceous sweat ceruminous

SUMMARY (12 of 12) Structure of nails Processes of inflammation and regeneration Effects of aging on the integument