AP1 Chapter 5 1

Chapter 5

The Integumentary System (IS)

Integument covering

Covers the outside of the body & is easily observed

Can be used as a diagnostic tool for determining health

AP1 Chapter 5 2

I. Functions of the Integumentary System

AP1 Chapter 5 3

I. Overview of the ISMajor Functions of the IS

1. Protection– Protects from abrasion & UV light– Prevents entry of microorganisms– Prevents water loss & thus dehydration

2. Sensation– Contains sensory receptors that detect temp, touch, pressure,

& pain

3. Temperature Regulation– Regulated via blood flow thru skin & activity of sweat glands

4. Vitamin D Production– When exposed to UV can produce molecules that may be

converted into Vit D

5. Excretion– Small amounts of wastes are excreted thru gland secretions

AP1 Chapter 5 4

II. SkinA. Epidermis

B. Thick & Thin Skin

C. Skin Color

D. Dermis

AP1 Chapter 5 5

II. SkinEpidermis

• Most superficial & made up of epithelial tissue

• Resists abrasion on skin surface

• Reduces water loss thru skin

Dermis

• Epidermis sits on top of dermis

• CT• Responsible for most of

the structural strength of the skin

Figure 5.1Pg 141

AP1 Chapter 5 6

II. Skin: Epidermis

• Strat. Squ. Epi separated from the dermis by a basement membrane

• Not very thick & contains no blood vessels relying on diffusion for nourishment and waste removal

Figure 5.2Pg 143

II. Skin: EpidermisCells that make-up the epidermis

1. Keratinocytes– Most of the cells of the epi

belong is this category b/c they prod a protein mixture called keratin wh/ makes cells hard

– This is the reason cells resist abrasion & reduce water loss

2. Melanocytes– Contribute to skin color

3. Langerhans Cells– Part of the immune system

4. Merkel Cells– Specialized cells associated

with nerve endings responsible for detecting light touch & superficial pressure

AP1 Chapter 5 7

Dead Keratinocytes

Keratinocytes

LangerhansCells

Melanocytes

Merkel cells

AP1 Chapter 5 8

II. Skin: Epidermis

• Cells of the epidermis are prod’d by mitosis in the deepest epi layer, as new cells are formed they push older cells toward the surface where they slough off (Desquamate). The outermost cells protect the deeper cells

• Keratinization – Cells D shape & internal chemical composition

becoming filled w/keratin– These cells eventually die & prod the outer layer of

dead-hard cells that resist abrasion & forms a permeability layer

II. Skin: Epidermis

1. Stratum Basale/Stratum Germinativum

2. Stratum Spinosum

3. Stratum Granulosum

4. Stratum Lucidum

5. Stratum Corneum

AP1 Chapter 5 9

5 layers of the epidermis

Figure 5.3 pg 144

Fig 5.3Pg. 144

II. Skin: Epidermis5 layers

1. Stratum Basale– Structure

• Deepest layer of the epi• Single layer of cube to

columnar shaped cells• Basement membrane

attaches the SB to the dermis

– Function• Prod’n of cells of the

most superficial layers• Melanocytes produce &

contribute to melanin in cells wh/ protects against UV

10

Fig

ure

5.3

pg 1

44

• Hemidesmosomes hold SB to basement membrane

• Desmosomes hold cells together• Keratinocytes undergo division every

19 days• 1 daughter pushes toward the surface

while the other stays in the SB• 40-56 days from start in SB to slough

off

II. Skin: Epidermis5 layers

2. Stratum Spinosum– Structure:

• 8-10 layers of many sided cells that flatten as the are pushed toward the surface

• Desmosomes are broken & reformed

• If cells are pulled apart they take on a spikey appearance thus the name

• There are additional keratin fibers & lipid filled organelles (Lamellar granules)

– Fxn:• Production of keratin fibers &

formation of lamellar bodies

11

Fig 5.3Pg. 144

II. Skin: Epidermis5 layers

3. Stratum Granulosum– Structure

• 2 to 5 layers of flattened diamond shaped cells

– Function• Prod’n of keratohyalin granules (makes

cells look grainy)• Lamellar bodies release lipids from

inside of the cells• Cells die (nucleus & other organelles

degenerate but keratin fibers and keratohyalin granules stay intact)

4. Stratum Lucidum– Structure

• 3 to 5 layers of clear dead cells w/indistinct boundaries

• Appear transparent & normally only in thick skin

– Function• Dispersion of keratohyalin around

keratin fibers12

Fig 5.3Pg. 144

II. Skin: Epidermis5 layers

5. Stratum Corenum– Structure:

• Most superficial layer of the epidermis

• 25 or more layers of dead squamous cells (Cornified)

– Fxn:• Provision of structural strength by

keratin within cells Soft Keratin– Soft Keratin:

» Keratin fibers + keratohyalin– Hard Keratin:

» Found in nails & hair

• Prevention of water loss via lipids surrounding cells

• Sloughing off the most superficial layers resists abrasion – Desmosomes\ eventually break– XSV sloughing dandruff

13

Fig 5.3Pg. 144

AP1 Chapter 5 14

• Classified based on the structure of the epidermis• “Thickness of the skin” (Epi + Dermis) varies dependent on location

ex/eyelid = 0.5mm shoulder/back = 5mm• Skin subjected to XSV friction or pressure will eventually develop a

callus (extra corneum) and these can develop on thick or thin skin• Corn cone shaped callus will develop over boney processes that

extends deep into epidermis and can be painful

• 4 epidermal layers• Covers the rest of the body• Granulosum often consists of

only 1 or 2 layers• Hair is only found on thin skin.• More flexible than thick skin

II. Skin: Thick and Thin Skin

Thick Skin

• All 5 epidermal layers & stratum corneum has many extra layers of cells

• Found in areas subjected to pressure & friction

• Palms, fingers, & soles

Thin Skin

AP1 Chapter 5 15

II. Skin: Skin Color

• Skin color is determined by:– Pigments w/in the skin– Blood circulating thru the skin– Thickness of the Stratum Corneum

AP1 Chapter 5 16

II. Skin: Skin Color- Melanin• Group of pigments responsible for skin, hair, & eye color• Provides UV protection• High Melanin:

– Freckles, moles, nipples, areolae of the breasts, axillae, & genitallia

• Low Melanin:– Lips & palms

• Originates from tyrosine & can be Ded into several different pigments ranging from black/brown to red/yellow

Pg 144 Figure5.4

AP1 Chapter 5 17

II. Skin: Skin Color- Melanin

1. Genetic Factors– Different races or those w/in the same race– Amounts & types of melanin prod’d– Size, #, & distribution of melanosomes– # of melanocytes usually doesn’t D but amount of melanin

prod’d does– 1 mutation can lead to albinism

2. Exposure to light– Darkens the melanin that is present & stimulates the prod’n of

more

3. Hormones– Pregnancy induces the prod’n of estrogen & melanocyte

stimulating hormone…thus increasing melanin prod’n• Line down middle of the belly, darkened nipples, areolae, & genetalia,

mask of pregnancy• Addison’s disease can also cause D in color

• Melanin production is based on 3 things

AP1 Chapter 5 18

II. Skin: Skin Color

Erythema

• Bld flowing thru skin imparts a reddish hue

• Induced by:– Inflammatory response– Colds, blushing, flushing

when angry or hot

• Decrease in bld flow (shock) can make skin pale

• Cyanosis: blue tint b/c of lack of O2

Carotene

• Yellow pigment found in plants (corn & carrots)

• Usually ingested and used as a source of Vit A

• XS ingestion can cause a discoloration (thus turning the skin yellow-orange)

AP1 Chapter 5 19

II. Skin: Dermis• CT with a few adipocytes &

macrophages as well the primary fiber is collagen

• Compared to hypodermis the bld vessels & adipose is minimal

• Present:– Nerve endings– Hair follicles– Smooth muscles– Glands– Lymphatic vessels

• If skin is overstretched dermis may rupture leaving epidermal scars called stretch marks

Fig 5.1Pg. 141

AP1 Chapter 5 20

Nerve endings of the Dermis

1. Free nerve endings:– Pain, itch, tickle,

temp

2. Hair follicle receptors– Light touch

3. Pacinian Corpuscle– Deep pressure

4. Meissner Corpuscle– Detect simultaneous

stimulation on 2 points on the skin

5. Ruffini End organs– Continuous touch or

pressure

Figure 14.2Pg. 464

II. Skin- 2 major layers of the Dermis1. Papillary Layer

– Superficial layer containing dermal papillae that extend toward the epidermis

– Contains bld vessels that supply epi w/nutrients & removes wastes as well as aiding in body temp regulation

– Thick skin responsible for finger prints wh/ fxn in increasing friction & improving grip

2. Reticular Layer– Deep layer composed of DICT– Continuous w/hypodermis &

forms a mat of irregularly arranged fibers that are resistant to stretching in many directions

– Cleavage/tension lines elastin & collagen arrangement that prod patterns in skin (Stitching)

AP1 Chapter 5 21

PapillaryLayer

ReticularLayer

Dermal Papilla

Epidermishttp://quizlet.com

/2510533/integument-and-related-structures-anim

al-flash-cards/

Fig. 5.5Pg. 145

AP1 Chapter 5 22

III. Hypodermis

a.k.a. Subcutaneous tissue

a.k.a. Superficial Fascia

AP1 Chapter 5 23

III. Hypodermis

• House Foundation Skin Hypodermis• Attaches to underlying bone & muscle, and supplies

upper layers w/bld vessels & nerves• Matrix Loose CT, collagen & elastic fibers• Cells: fibroblasts, adipose cells, & macrophages• ~ ½ of the bodies adipose is stored here

– Fxns: insulation, energy, & padding– Amount varies with age and sex

• Babies have more than adults• Women more than men in hips and breasts• Body shape can also change w/ fat stores

AP1 Chapter 5 24

IV. Accessory Skin StructuresA. Hair

B. Glands

C. Nails

IV. Accessory Skin Structures: Hair

• Hair is found almost every where except:– Palms, soles, lips, nipples, external

genitalia, & distal segments of the fingers & toes

• Hair types:– Lanugo

• 5th-6th mo of fetal development• Delicate unpigmented hair

– Terminal Hairs• Near birth• Long course pigmented hair replaces lanugo

on scalp, eyelids, & eyebrows

– Vellus Hairs• Replace rest of body hair• Short, fine, usually unpigmented

– Puberty: terminal hair replaces that of armpit (axillary) and pubic regions [Suggested* Wicks/protects from abrasion] AP1 Chapter 5 25

• Men chest, legs, arms 90% terminal hair

• Women 35%

Fig 5.6Pg. 149

AP1 Chapter 5 26

IV. A

cces

sory

Ski

n S

truc

ture

: Hai

rHair Structure

• Hair shaft: protrudes above the surface

• Hair Root: located below the surface

• Hair Bulb: expanded base of root• 3 concentric layers to hair

root/shafta. Medulla

• Central axis of the hair 2-3 layers of cells w/soft keratin

b. Cortex• Forms bulk of hair cells contain

hard keratin (more S in make-up)

c. Cuticle• Single layer of cells that forms hair

surface & overlap like shingles

Fig 5.6Pg. 149

AP1 Chapter 5 27

IV. Accessory Skin Structure: HairHair Structure

• Hair follicle:– Tube like invagination of the

epidermis that extends into the dermis from which the hair develops

– Consists of:

1. Dermal Root Sheath• Portion of the dermis that

surrounds the Epi root sheath

2. Epithelial Root Sheatha. External

All strata found in thin skin toward hair shaft but decreases as it goes down until it is only the stratum basale

b. Internal Holds hair in place, and

when hair is pulled it usually can be seen at the base

Fig 5.6Pg. 149

IV. Accessory Skin Structure: Hair

Hair Structure• Inside of the hair bulb

– Matrix: mass of undifferentiated

epithelial cells which prod the hair & the epithelial root sheath.

– Hair Papilla: Dermis of the skin projects into

the hair bulb at the base and contains blood vessels that provide nourishment for the cells of the matrix

AP1 Chapter 5 28

Hair Color • Melanin is prod’d by melanocytes w/in hair bulb matrix & is passed to keratinocytes in hair cortex & medulla

• Varying amounts & types of melanin cause different shades

• W/ age amount of melanin in hair can decrease; causing hair color to fade

Fig 5.6Pg. 149

AP1 Chapter 5 29

IV. Accessory Skin Structure: HairHair Growth

• Hair is prod’d in cycles

1. Growth Stage Hair is formed by matrix cells

that differentiate, become keratinized and die

Hair grows longer as cells are added to the base

2. Resting Stage Hair growth stops hair follicle

shortens & hold hair in place

• Eyelashes:– 30 days growth – 105 days rest

• Scalp:– 3 years growth– 1-2 years rest

• Ave. hair growth is 0.3mm a day

• Max hair length is determined by rate of hair growth & length of growing phase

AP1 Chapter 5 30

IV. Accessory Structures: Muscles

• Arrector Pili– Extend from the dermal

root sheath of the hair follicle to the papillary layer of the dermis

– This takes the hair from oblique angle to a more perpendicular angle to the skin surface (gooseflesh)

– Cold or scared

Pg. 152

AP1 Chapter 5 31

IV. Accessory Skin Structures: Glands

• Major skin glands:

a. Sebaceous glands

b. Sudoriferous1. Eccrine

2. Apocrine

Pg. 152

AP1 Chapter 5 32

IV. Accessory Skin Structures: Glands

• Major skin glands:a. Sebaceous glands

– Located in the dermis– Simple/Compound alveolar

glands that produce sebum• Oily white substance rich in lipids

– Holocrine glands b/c lysis & death of cells that become part of secretion

– Connected via duct to hair follicle– Prevents drying & protects

against some bacteria– Very few open to skin surface

(lips, eyelids[meibomain], & genetalia)

Pg. 152

AP1 Chapter 5 33

IV. Accessory Skin Structures: Glands• Major skin glands:

b. Sudoriferous Sweat glands1. Eccrine

• Most common type found almost everywhere (including hands & soles of feet)

• Simple, coiled, tubular glands that open to skin surface through pores

• 2 regions:• Deep coiled region (dermis)

– Produces sweat (isotonic fluid that includes water, some salt, small amounts of urea, ammonia, uric acid, & lactic acid)

• Duct (passes to surface)• Help regulate temperature

2. Apocrine

Pg. 152

IV. Accessory Skin Structures: Glands• Major skin glands:

b. Sudoriferous Sweat glands

1. Eccrine

2. Apocrine• Simple coiled tubular glands that

open into hair follicles superficially to sebaceous glands

• In humans they are found in the axillae, genitalia, and around the anus

• Do not regulate temperature, but do release some chemicals that produce odor once bacteria process them (body odor)

• Only become active at puberty as a result of sex hormone stimulation

• May be a sign of sexual maturity.AP1 Chapter 5 34

Pg. 152

AP1 Chapter 5 35

IV. Accessory Skin Structures: Glands

Other glands• Ceruminous Glands:

– modified sweat glands located in the ear canal produce cerumen (earwax) to protect eardrum by preventing entry of dirt or small insects

• Mammary Glands:– Modified apocrine sweat glands in breasts

designed to produce milk

AP1 Chapter 5 36

IV. Accessory Skin Structures: Nail

• Distal ends of primate digit covered in nail

• Grow 0.5-1.2mm/Day• Finger nails grow faster than toe

nails• Unlike hair, there is no resting

stage meaning growth is continuous

• Fxn: – Protection, manipulation & grasping

of small objects & scratching

• Nail consists of 2 major parts:A. Nail Root (Proximal portion):

covered by skin

B. Nail Body (Distal Portion): visible portion

Fig. 5.8Pg. 153

AP1 Chapter 5 37

IV. Accessory Skin Structures: Nail

• Nail fold: Flaps of skin that cover the root & lateral edges

• Nail grove: holds edges of nail in place

• Eponychium: cuticle• Hyponychium: thickened

portion of stratum corneum beneath the free edge of the nail body

• Nail Root extends distally from nail matrix, which produces the majority of the nail

• Nail bed holds the nail body• Lunula- crescent shaped area

at the base of the nail that has almost no color because it is thicker that the rest of the nail

Fig. 5.8Pg. 153

AP1 Chapter 5 38

V. Summary of IS fxnsA. Protection

B. Sensation

C. Temperature regulation

D. Vitamin D Production

E. Excretion

Reread b4 presenting!!!!!

AP1 Chapter 5 39

V. Summary of IS Fxns

1. Protection

• Protects against abrasion, UV-light, prevents entry of microorganisms, helps regulate body temperature, & prevents water loss.

• Hair protects against abrasion & blocks UV-light & is a heat insulator

• Nails protect the ends of digits

2. Sensation

• Skin contains sensory receptors for:– Pain– Touch– Hot– Cold– Pressure

• These allow for proper response to the environment

AP1 Chapter 5 40

V. Summary of IS Fxns

3. Temperature Regulation

• Thru dilation & constriction of blood vessels, the skin controls heat loss from the body

• Sweat glands produce sweat, which evaporates & lowers body temperature

4. Vitamin D Production• Skin exposed to UV-light

produces cholecalciferol, wh/ is modified in the liver & then in the kidneys to form active Vit D.

• Vit D increases blood Ca levels by promoting Ca uptake from the intestine, the release of Ca from the bone, and the reduction of Ca loss from the kidneys.

AP1 Chapter 5 41

V. Summary of IS Fxns

5. Excretion

• Skin glands remove small amounts of waste products (i.e. urea, uric acid, & ammonia) but are not important to excretion like the kidneys.

AP1 Chapter 5 42

VI. FX of aging on IS

AP1 Chapter 5 43

VI. Effects of aging on the IS

• As the body ages, blood flow to the skin declines, thus skin becomes thinner & elasticity is lost

• Sudoriferous & sebaceous glands are less active and the number of melanocytes also decreases