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Chapter 5: The Integumentary System. Size of the Integument. The integument is the largest system of the body: 16% of body weight 1.5 to 2 m 2 in area. Parts of the Integument . The integument is made up of 2 parts: cutaneous membrane (skin) accessory structures.

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Chapter 5 the integumentary system
Chapter 5: The Integumentary System

Size of the integument
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
Parts of the Integument

  • The integument is made up of

    2 parts:

    • cutaneous membrane (skin)

    • accessory structures

Parts of the integumentary system
Parts of the Integumentary System

Figure 5–1

Parts of the cutaneous membrane
Parts of the Cutaneous Membrane

  • Outer epidermis:

    • superficial epithelium (epithelial tissues)

  • Inner dermis:

    • connective tissues

Accessory structures
Accessory Structures

  • Originate in the dermis

  • Extend through the epidermis to skin surface:

    • hair

    • nails

    • multicellular exocrine glands

Functions of skin
Functions of Skin

  • Protects underlying tissues and organs

  • Excretes salts, water, and organic wastes (glands)

  • Maintains body temperature (insulation and evaporation)

Functions of skin1
Functions of Skin

  • Synthesizes vitamin D3

  • Stores lipids

  • Detects touch, pressure, pain, and temperature

What are the main structures and functions of the epidermis
What are the main structures and functions of the epidermis?


  • Avascular stratified squamous epithelium

  • Nutrients and oxygen diffuse from capillaries in the dermis

Layers of the epidermis
Layers of the Epidermis

  • From basal lamina to free surface:

    • stratum germinativum

    • stratum spinosum

    • stratum granulosum

    • stratum lucidum

    • stratum corneum

Stratum germinativum
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
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
Ridges and Ducts

Figure 5–4

Cells of stratum germinativum
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
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
Cells of Stratum Spinosum

  • Continue to divide, increasing thickness of epithelium

  • Contain Langerhans cells, active in immune response

Stratum granulosum
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
Cells of Stratum Granulosum

  • Produce protein fibers

  • Dehydrate and die

  • Create tightly interlocked layer of keratin surrounded by keratohyalin

Stratum lucidum
Stratum Lucidum

  • The “clear layer”:

    • found only in thick skin

    • covers stratum granulosum

Cells of stratum lucida
Cells of Stratum Lucida

  • Flat

  • Dense

  • Filled with keratin

Stratum corneum
Stratum Corneum

  • The “horn layer”:

    • exposed surface of skin

    • 15 to 30 layers of keratinized cells

    • water resistant

    • shed and replaced every 2 weeks


  • The formation of a layer of dead, protective cells filled with keratin

  • Occurs on all exposed skin surfaces except eyes

Skin life cycle
Skin Life Cycle

  • It takes 15–30 days for a cell to move from stratum germinosum to stratum corneum

Skin color
Skin Color

  • Skin color depends on:

    • the pigments carotene and melanin

    • blood circulation (red cells)


  • Orange-yellow pigment

  • Found in orange vegetables

  • Accumulates in epidermal cells and fatty tissues of the dermis

  • Can be converted to vitamin A


  • Yellow-brown or black pigment

  • Produced by melanocytes in stratum germinativum

  • Stored in transport vesicles (melanosomes)

  • Transferred to keratinocytes

Function of melanocytes
Function of Melanocytes

  • Melanin protects skin from sun damage

  • Ultraviolet (UV) radiation:

    • causes DNA mutations and burns which lead to cancer and wrinkles

      Skin color depends on melanin production and not the number of melanocytes


Figure 5–5

Capillaries and skin color
Capillaries and Skin Color

  • Oxygenated red blood contributes to skin color:

    • blood vessels dilate from heat, skin reddens

    • blood flow decreases, skin pales


  • Bluish skin tint

  • Caused by severe reduction in blood flow or oxygenation

Illness and skin color
Illness and Skin Color

  • Jaundice:

    • buildup of bile produced by liver

    • yellow color

  • Addison’s disease:

    • and other diseases of pituitary gland

    • skin darkening

Illness and skin color1
Illness and Skin Color

  • Vitiglio:

    • loss of melanocytes

    • loss of color

Vitamin d
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

Epidermal growth factor egf
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
Functions of EGF

  • Promotes division of germinative cells

  • Accelerates keratin production

  • Stimulates epidermal repair

  • Stimulates glandular secretion

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
The Papillary Layer

  • Consists of areolar tissue

  • Contains smaller capillaries, lymphatics, and sensory neurons

  • Has dermal papillae projecting between epidermal ridges

The reticular layer
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

Characteristics of dermis
Characteristics of Dermis

  • Strong, due to collagen fibers

  • Elastic, due to elastic fibers

  • Flexible (skin turgor)

Dermal circulation
Dermal Circulation

Figure 5–8


  • Cutaneous plexus:

    • a network of arteries along the reticular layer

  • Papillary plexus:

    • capillary network from small arteries in papillary layer


  • Venous plexus:

    • capillary return deep to the papillary plexus

  • Contusion:

    • damage to blood vessels resulting in “black and blue” bruising


  • Nerve fibers in skin control:

    • blood flow

    • gland secretions

    • sensory receptors

  • Tactile disks monitor Merkel cells

What are the structures and functions of the subcutaneous layer
What are the structures and functions of the subcutaneous layer?

The hypodermis
The Hypodermis

  • The subcutaneous layer or hypodermis:

    • lies below the integument

    • stabilizes the skin

    • allows separate movement

Structure of the hypodermis
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
Clinical Importance

  • Subcutaneous layer:

    • has few capillaries and no vital organs

    • is the site of subcutaneous injections using hypodermic needles

Adipose tissue
Adipose Tissue

  • Deposits of subcutaneous fat:

    • have distribution pattern determined by hormones

    • are reduced by cosmetic liposuction

Integumentary accessory structures
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

Location of hair
Location of Hair

  • The human body is covered with hair, except:

    • palms

    • soles

    • lips

    • portions of external genitalia

Functions of hair
Functions of Hair

  • Protects and insulates

  • Guards openings against particles and insects

  • Is sensitive to very light touch

The hair follicle
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)

Accessory structures of hair
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
Regions of the Hair

  • Hair root:

    • lower part of the hair

    • attached to the integument

  • Hair shaft:

    • upper part of the hair

    • not attached to the integument

Inside the follicle
Inside the Follicle

Figure 5–9b

How hair grows
How Hair Grows

  • Hair begins deep in the dermis:

    • the hair papilla contains capillaries and nerves

    • the hair bulb produces hair matrix

Hair matrix
Hair Matrix

  • A layer of dividing basal cells

  • Produce hair structure

  • Push hair up and out of skin

Layers in a hair
Layers in a Hair

  • Medulla:

    • the central core

  • Cortex:

    • the middle layer

  • Cuticle

    • the surface layer

Structure of a hair
Structure of a Hair

Figure 5–9d


  • As hair is produced, it is keratinized:

    • medulla contains flexible soft keratin

    • cortex and cuticle contain stiff hard keratin

Layers in the follicle
Layers in the Follicle

  • Internal root sheath:

    • the inner layer

    • contacts the cuticle in lower hair root

  • External root sheath:

    • extends from skin surface to hair matrix

  • Glassy membrane:

    • a dense connective-tissue sheath

    • contacts connective tissues of dermis

Hair growth cycle
Hair Growth Cycle

  • Growing hair:

    • is firmly attached to matrix

  • Club hair:

    • is not growing

    • is attached to an inactive follicle

Hair growth cycle1
Hair Growth Cycle

  • New hair growth cycle:

    • follicle becomes active

    • produces new hair

    • club hair is shed

Types of hairs
Types of Hairs

  • Vellus hairs:

    • soft, fine

    • cover body surface

  • Terminal hairs:

    • heavy, pigmented

    • head and eyebrows

    • other parts of body after puberty

Hair color
Hair Color

  • Produced by melanocytes at the hair papilla

  • Determined by genes

Exocrine glands
Exocrine Glands

  • Sebaceous glands (oil glands):

    • holocrine glands

    • secrete sebum

  • Sweat glands:

    • merocrine glands

    • watery secretions

Types of sebaceous glands
Types of Sebaceous Glands

  • Simple branched alveolar glands:

    • associated with hair follicles

  • Sebaceous follicles:

    • discharge directly onto skin surface

Sebaceous glands
Sebaceous Glands

Figure 5–10


  • Contains lipids and other ingredients

  • Lubricates and protects the epidermis

  • Inhibits bacteria

What are the functions of sweat glands
What are the functions of sweat glands?

Types of sweat glands
Types of Sweat Glands

  • Apocrine:

    • found in armpits, around nipples, and groin

  • Merocrine:

    • widely distributed on body surface

    • especially on palms and soles

Apocrine sweat gland
Apocrine Sweat Gland

Figure 5–11a

Apocrine sweat glands
Apocrine Sweat Glands

  • Merocrine secretions, not apocrine

  • Associated with hair follicles

  • Produce sticky, cloudy secretions

  • Break down and cause odors

Myoepithelial cells
Myoepithelial Cells

  • Squeeze apocrine gland secretions onto skin surface

  • In response to hormonal or nervous signals

Merocrine sweat glands
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
Merocrine Sweat Gland

Figure 5–11b

Functions of merocrine sweat
Functions of Merocrine Sweat

  • Cools skin

  • Excretes water and electrolytes

  • Flushes microorganisms and harmful chemicals from skin

Other integumentary glands
Other Integumentary Glands

  • Mammary glands:

    • produce milk

  • Ceruminous glands:

    • protect the eardrum

    • produce cerumen (earwax)

Control of glands
Control of Glands

  • Autonomic nervous system:

    • controls sebaceous and apocrine sweat glands

    • works simultaneously over entire body

  • Merocrine sweat glands:

    • are controlled independently

    • sweating occurs locally


  • Thermoregulation:

    • is the main function of sensible perspiration

    • works with cardiovascular system

    • regulates body temperature

Nail functions
Nail Functions

  • Nails protect fingers and toes:

    • made of dead cells packed with keratin

    • metabolic disorders can change nail structure

Nail production
Nail Production

  • Occurs in a deep epidermal fold near the bone called the nail root

Structure of a nail
Structure of a Nail

Figure 5–12

Structures of nails
Structures of Nails

  • Nail body:

    • the visible portion of the nail

    • covers the nail bed

  • Lunula:

    • the pale crescent at the base of the nail

Structures of nails1
Structures of Nails

  • Sides of nails:

    • lie in lateral nail grooves

    • surrounded by lateral nail folds

  • Skin beneath the free edge of the nail:

    • is the hyponychium

Structures of nails2
Structures of Nails

  • Visible nail emerges:

    • from the eponychium(cuticle)

    • at the tip of the proximal nail fold

Repair of localized injuries to the skin step 1
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
Repair of Localized Injuries to the Skin: Step 2

  • A scab stabilizes and protects the area

Figure 5–13 (Step 2)

The inflammatory response
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
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
Repair of Localized Injuries to the Skin: Step 4

  • Fibroblasts strengthen scar tissue

  • A raised keloid forms


Integumentary Repair

Figure 5–13 (Step 4)