Vocabulary Cornu - horn; stratum corneum Cutis – skin; cutaneous

Vocabulary

Cornu - horn; stratum corneumCutis – skin; cutaneousDerma – skin; dermisEpi- above or over; epidermisFacere – to makeGerminate – to start growing, stratum

germinativumKeros – horn, keratinKyanos – blue; cyanosis

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Vocabulary

Luna – moon; lunulaMelas – black; melaninOnyx – nail; eponychiumPapilla – a nipple-shaped mound;

dermal papillae


Integumentary Structure/Function

Integumentary System consists of skin, hair, nails, and various glands

It is the most visible organ system



Integumentary System Components (2 major ones)1. Cutaneous membrane - skin

• Epidermis• Dermis• Accessory structures – hair, nails, and a

variety of exocrine glands2. Subcutaneous layer (aka -hypodermis):

attaches the integument to much deep structures such as muscles and bones


Functions

Main Functions of the Integument (5)1. Protection: covers and protects

underlying organ systems while prevent the loss of bodily fluids

2. Temperature maintenance: regulates heat exchange with the environment

3. Synthesis and storage of nutrients:makes vitamin D, a steroid building

block needed for calcium uptakeStores lipids in adipose tissue

Functions

Main Functions of the Integument (5)4. Sensory reception: receptors

detect, touch, pressure, pain, and temperature – information goes to the nervous system

5. Excretion and secretion: glands excrete salts, water, and organic wastes


Integumentary Structure/FunctionComponents of the Integumentary System

Figure 5-1

Epidermis

The Epidermis•Stratified squamous epithelium•Several distinct cell layers

• Thick skin — 5 layers•On palms and soles•About 0.5 mm thick

• Thin skin — 4 layers•On rest of body•About 0.08 mm thick


Layers of The Epidermis (5)

Cell Layers of The Epidermis (5) – in order from the basement membrane

1. Stratum germinativum (stratum = layer + germinare = start growing)

2. Stratum spinosum3. Stratum granulosum4. Stratum lucidum (only in thick skin)5. Stratum corneum

• Dying superficial layer• Keratin accumulationCopyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Integumentary Structure/FunctionThe Structure of the Epidermis

Figure 5-2

Layers of The Epidermis (1 of 5) 1. Stratum germinativum: Deepest layer -

attached to the basement membrane which separates the epidermis from loose connective tissue of the dermis• Forms epidermal ridges – extends into the

dermisHas dermal projections called dermal papillae – extend upward into

between adjacent ridges• Increases the surface area


Layers of The Epidermis (1 of 5)1. Stratum germinativum: •Contains Stem cells

• Cell division layer• Source of replacement cells

•Contains Melanocytes•Synthesize melanin (yellow-brown

brown or black pigments produced by Melanocytes)


Layers of The Epidermis (2, 3, and 4 of 5)

• Intermediate strata As they grow upwards they become specialized

2. Stratum spinosum (spiny layer)Superficial to stratum germinativum – cells may

continue to divide3. Stratum granulosum (grainy layer)

No cell division –replaced by Stratum spinosumStarts making keratin – coats the skin and makes the

basic structure of hair and nails4. Stratum lucidum (clear layer)

Densely packed and flattened cells filled with keratin


Layers of The Epidermis (5 of 5)

5. Stratum corneum• Most superficial layer• Flattened (squamous) cells – 15 to 30 layers• Dead cells• Abundant keratin

•Keratinized (also, cornified)•Tough, water-resistant protein

• Tightly Pack – shed in sheets•Keratinized

Epidermis Sources of Skin Color•Melanocytes

• Make melanin• Melanin provides UV protection• Gives reddish-brown to brown-black color

•Carotene• Contributes orange-yellow color• Provided from diet

•Hemoglobin• Blood pigment


Epidermis

Melanocytes

Figure 5-3

Integumentary Structure/FunctionEffects of UV Radiation•Beneficial effects

• Activates synthesis of vitamin D3 Beneficial effect

• Activates synthesis of vitamin D3

•Harmful effects• Sun burn• Wrinkles, premature aging

Integumentary Structure/Function•Harmful effects (cont.)

• Skin cancer – most common cancerBasal cell carcinoma – most common and

originates in the stratum germinavitum (basal layer)

Squamous cell carcinoma – involves superficial layer

Malignant melanoma – extremely dangerous - metastasize through the lymphatic system

Integumentary Structure/FunctionTwo Important Types of Skin Cancer

Figure 5-4


Skin Cancer Facts

Most of the more than 1 million cases of non-melanoma skin cancer diagnosed yearly in the United States are considered to be sun-related. Melanoma will account for about 60,000 cases of skin cancer and most (about 80%) of the deaths due to skin cancer each year.

Skin Cancer ABCs

Skin Cancer Facts

How do you protect yourself from skin cancer?

Key NoteThe epidermis is a multi-layered, flexible, self-repairing barrier that prevents fluid loss, provides protection from UV radiation, produces vitamin D3, and resists damage from abrasion, chemicals, and pathogens


Epidermis

DermisComponents of the Integumentary System

Figure 5-1

Dermis

Dermis: found beneath the epidermis. It has two major components

1. Papillary layer2. Reticular Layer

Dermis: 1. Papillary Layer

Underlies epidermis• Named for dermal papillae• Loose connective tissue• Supports, nourishes epidermis• Provides sensory nerves,

lymphatics, and capillaries

Dermis: 2. Reticular Layer

Tough, dense, fibrous layer• Collagen fibers - Limit stretch• Elastic fibers - Provide flexibility• Blends into papillary layer (above)• Blends into subcutaneous layer

(below)


Dermis

Other Dermal Components•Epidermal accessory organs•Cells of connective tissues proper•Communication with other organ systems

• Cardiovascular (Chapter 13)• Lymphatic (Chapter 14)• Nervous (Chapter 9)

•Sensation•Control of blood flow and secretion



Key NoteThe dermis provides mechanical strength, flexibility, and protection for underlying tissues. It is highly vascular and contains a variety of sensory receptors that provide information about the external environment.


Subcutaneous LayerComponents of the Integumentary System

Figure 5-1

Subcutaneous Layer

The Subcutaneous Layer•Composed of loose connective tissue•Stabilizes skin position

• Loosely attached to dermis• Loosely attached to muscle

•Contains many fat cells• Provides thermal insulation• Cushions underlying organs

•Safely receives hypodermic needlesCopyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Accessory Structures

Accessory Structures (4 main structures)1. Hair 2. Sebaceous glands3. Sweat Glands4. Nails


Accessory Structures - Hair

Hairs project above the surface of the skin almost everywhere except the side and soles of the feet, the palms of the hands, sides of the fingers and toes, and the lips


Hairs are non-living and produced in organs called follicles

There are about 2.5 million hairs on the human body!

• About 500,000 on the scalp that protect the head from UV light, provide insulation, and help cushion the skull form a light blow.

• Eyelid and nostril hair have a function


Shaft•Medulla – the inside core of the hair•Cortex – the outside core of the hair•Cuticle•Arrector pili muscle



Figure 5-5(a)

Hair Follicles


Hair Follicles

Figure 5-5(b)

Integumentary Structure/FunctionHair Follicles

Figure 5-5(c)


Accessory Structures•Hair growth cycle

• 0.3 mm/day growth rate• 2–5 years growth• 2–5 years follicle rest• Follicle reactivation• Old hair shedding



Accessory Structures•Sebaceous glands (oil glands)

• Holocrine gland• Oily secretion

•Sebum•Hair shaft lubricant

• Sebaceous follicle•Skin lubricant•Skin waterproofing


Integumentary Structure/FunctionThe Structure of Sebaceous Glands and Their

Relationship to Hair Follicles

Figure 5-6


Sweat Glands•Apocrine

• Odorous secretion (“funky”)• Absent before puberty• Present in axilla, areola, groin

•Merocrine• Watery sweat (~1% NaCl)• For heat loss• Widely present in skin (up to

500/cm2)Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Integumentary Structure/FunctionSweat Glands

Figure 5-7


Key NoteThe skin plays a major role in controlling body temperature. It acts as a radiator, with the heat being delivered by the dermal circulation and removed primarily by the evaporation of sweat or perspiration.


Accessory Structures: NailsForms on the dorsal surface of finger and toes

•Nail body- visible part of the nail• Dense mass of keratinized cells

•Nail bed – body of the nail which covers a layer of epidermis

•Nail root – where nail production takes place•Cuticle (eponychium) – portion of stratum

corneum of the fold that extends over the exposed nail closest to the root

• Lunula – area where underlying blood vessels are obscure



Figure 5-8

The Structure of a Nail

Skin Injury and Repair

Four Stages in Skin Healing1. Inflammation

• Blood flow increases• Phagocytes attracted

2. Scab formation3. Cell division and migration4. Scar formation


Figure 5-92 of 5Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Bleeding occurs at the site of injury immediately after the injury, and mast cells in the region trigger an inflammatory response.

Epidermis

Dermis


Bleeding occurs at the site of injury immediately after the injury, and mast cells in the region trigger an inflammatory response.

Epidermis

Dermis

After several hours, a scab has formed and cells of the stratum germinativum are migrating along the edges of the wound. Phagocytic cells are removing debris, and more of these cells are arriving with the enhanced circulationin the area. Clotting around the edgesof the affected area partially isolatesthe region.

Sweat gland

Scab

Macrophagesand

fibroblasts

Migratoryepithelialcells

Granulationtissue


One week after the injury, the scab has been undermined by epidermal cells migrating over the meshwork produced by fibroblast activity. Phagocytic activity around the site has almost ended, and the fibrin clot is disintegrating.

Fibroblasts


One week after the injury, the scab has been undermined by epidermal cells migrating over the meshwork produced by fibroblast activity. Phagocytic activity around the site has almost ended, and the fibrin clot is disintegrating.

Fibroblasts

After several weeks, the scab has been shed, and the epidermis is complete. A shallow depression marks the injury site, but fibroblasts in the dermis continue to create scar tissue that will gradually elevate the overlying epidermis.

Scartissue

Skin Injury and Repair

Table 5-1

Aging of the Skin

Major Age-Related Changes• Injury and infection increase• Immune cells decrease (by 50%)• Sun protection diminishes – melanin

production deceases• Skin becomes dry, scaly – reduced glandular

production•Hair thins, grays – follicles die or make thinner

hair, melanin production decreases


Aging of the Skin

Major Age-Related Changes• Sagging, wrinkles occur – thinner dermis with

reduced elastic properties•Heat loss decreases – blood supply to skin

reduced at the same time as glandular production reduction

•Repair slows – due to recurrent infections (at 65-75 it takes 6-8 weeks for a blister to heal compared to 3-4 weeks


The Integumentary System in Perspective

FIGURE 5-10 Functional Relationships Between the Integumentary System and Other Systems


Figure 5-101 of 11


Figure 5-102 of 11

• Provides structural support• Synthesizes vitamin D3,

essential for calcium and phosphorus absorption (bone maintenance and growth)

The Skeletal System


Figure 5-103 of 11

The Muscular System

• Contractions of skeletal muscle pull against skin of face, producing facial expressions important in communication

• Synthesizes vitamin D3 , essential for normal calcium absorption (calcium ions play an essential role in muscle contraction)


Figure 5-104 of 11

The Nervous System

• Controls blood flow and sweat gland activity for thermoregulation; stimulates contraction of arrector pili muscles to elevate hairs

• Receptors in dermis and deep epidermis provide sensations of touch, pressure, vibration, temperature, and pain


Figure 5-105 of 11

The Endocrine System

• Sex hormones stimulate sebaceous gland activity; male and female sex hormones influence hair growth, distribution of subcutaneous fat, and apocrine sweat gland activity; adrenal hormones alter dermal blood flow and help mobilize lipids from adipocytes

• Synthesizes vitamin D3, precursor of calcitriol


Figure 5-106 of 11

The Cardiovascular System

• Provides oxygen and nutrients; delivers hormones and cells of immune system; carries away carbon dioxide, waste products, and toxins; provides heat to maintain normal skin temperature

• Stimulation by mast cells produces localized changes in blood flow and capillary permeability


Figure 5-107 of 11

The Lymphatic System

• Assists in defending the integument by providing additional macrophages and mobilizing lymphocytes

• Provides physical barriers that prevent pathogen entry; macrophages resist infection; mast cells trigger inflammation and initiate the immune reponse


Figure 5-108 of 11

The Respiratory System

• Provides oxygen and eliminates carbon dioxide

• Hairs guard entrance to nasal cavity


Figure 5-109 of 11

The Digestive System

• Provides nutrients for all cells and lipids for storage by adipocytes

• Synthesizes vitamin D3, needed for absorption of calcium and phosphorus


Figure 5-1010 of 11

The Urinary System

• Excretes waste products, maintains normal body fluid pH and ion composition

• Assists in elimination of water and solutes; keratinized epidermis limits fluid loss through skin


Figure 5-1011 of 11

The Reproductive System

• Sex hormones affect hair distribution, adipose tissue distribution in subcutaneous layer, and mammary gland development

• Covers external genitalia; provides sensations that stimulate sexual behaviors; mammary gland secretions provide nourishment for newborn infant

Vocabulary Cornu - horn; stratum corneum Cutis – skin; cutaneous

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