The The Integumentary Integumentary

SystemSystemChapter 6Chapter 6

General Information About General Information About the Integumentary Systemthe Integumentary System

Covers approx. 2 square Covers approx. 2 square meters (20 sq. ft.)meters (20 sq. ft.)

Accounts for 15% of total Accounts for 15% of total body weightbody weight

Major organ is the skin, but Major organ is the skin, but also includes hair, glands, also includes hair, glands, receptors, and blood vesselsreceptors, and blood vessels

FunctionsFunctionsProtection – physical barrier Protection – physical barrier

against loss of body fluids, physical against loss of body fluids, physical injury, UV light, and pathogensinjury, UV light, and pathogens

Regulates body temperature – Regulates body temperature – sweat, blood circulationsweat, blood circulation

Communication – sensory Communication – sensory receptors relay info. regarding receptors relay info. regarding heat, cold, touch and pain to brainheat, cold, touch and pain to brain

Functions cont’dFunctions cont’d

Excretion of waste – sweat Excretion of waste – sweat glands release small glands release small amounts of ureaamounts of urea

Vitamin D production – Vitamin D production – when exposed to UV light, when exposed to UV light, aids in absorption of calciumaids in absorption of calcium

The SkinThe Skin

Largest organ of integumentary Largest organ of integumentary systemsystem

Thin, superficial layer of Thin, superficial layer of stratified squamous epithelial stratified squamous epithelial tissue called the epidermistissue called the epidermis

Thick, deeper layer of connective Thick, deeper layer of connective tissue called the dermistissue called the dermis

The Skin cont’dThe Skin cont’d

Between skin and muscle Between skin and muscle is the hypodermis, also is the hypodermis, also called the superficial called the superficial fascia or subcutaneous fascia or subcutaneous layerlayer

The EpidermisThe EpidermisDynamic sheet of cells that Dynamic sheet of cells that

forms a waterproof, forms a waterproof, protective wrap over the protective wrap over the body’s surfacebody’s surface

Millions of cells in the Millions of cells in the epidermis are worn away by epidermis are worn away by the activities of everyday lifethe activities of everyday life

Made of stratified squamous Made of stratified squamous epitheliumepithelium

The Epidermis cont’dThe Epidermis cont’d

Deepest layer contains living, Deepest layer contains living, rapidly dividing columnar cells rapidly dividing columnar cells that push older cells toward the that push older cells toward the surfacesurface

Older cells flatten and die as Older cells flatten and die as they near the surface; cell they near the surface; cell contents are replaced by a contents are replaced by a protein called keratinprotein called keratin

Layers of EpidermisLayers of Epidermis

Stratum Stratum corneumcorneum

Stratum lucidumStratum lucidum Stratum Stratum

granulosumgranulosum Stratum Stratum

spinosumspinosum Stratum basaleStratum basale

Stratum BasaleStratum Basale

Deepest layer of epidermisDeepest layer of epidermis Columnar / cuboidal cells form Columnar / cuboidal cells form

bottom layer, closest to vascular bottom layer, closest to vascular dermisdermis

Require nutrients for rapid cell Require nutrients for rapid cell divisiondivision

Push previously formed cells Push previously formed cells toward the surfacetoward the surface

Stratum spinosumStratum spinosum

Multiple-layered Multiple-layered arrangement of cuboidal arrangement of cuboidal cellscells

Contain molecular bridges Contain molecular bridges that connect them to that connect them to adjacent cells, gives them a adjacent cells, gives them a “prickly” appearance“prickly” appearance

Stratum spinosum cont’dStratum spinosum cont’d

Nuclei are often darkened, a Nuclei are often darkened, a condition called pyknosis, condition called pyknosis, which is an early sign of cell which is an early sign of cell deathdeath

Cells begin to die because Cells begin to die because they’re cut off from supply they’re cut off from supply of nutrients and oxygenof nutrients and oxygen

Stratum granulosumStratum granulosum

3 to 5 rows of partially 3 to 5 rows of partially flattened cellsflattened cells

Cells contain granules of Cells contain granules of proteins that stain dark and proteins that stain dark and are intermediate to the are intermediate to the formation of keratinformation of keratin

Stratum lucidumStratum lucidum

Present only in the thick Present only in the thick skin of the palms and solesskin of the palms and soles

3 to 4 rows of flattened, 3 to 4 rows of flattened, dead cells that are mostly dead cells that are mostly transparenttransparent

Stratum corneumStratum corneum

Most superficial layerMost superficial layer20 – 50 rows of flattened, 20 – 50 rows of flattened,

dead cellsdead cellsAre “sloughed off” as a Are “sloughed off” as a

result of normal wear and result of normal wear and teartear

Stratum Corneum cont’dStratum Corneum cont’d

Entire journey from stratum Entire journey from stratum basale to surface takes basale to surface takes between 3 and 4 weeksbetween 3 and 4 weeks

By this time, cells are By this time, cells are nothing but “ghosts” having nothing but “ghosts” having their contents completely their contents completely replaced by keratinreplaced by keratin

Layers of EpidermisLayers of Epidermis

Stratum Stratum corneumcorneum

Stratum lucidumStratum lucidum Stratum Stratum

granulosumgranulosum Stratum Stratum

spinosumspinosum Stratum basaleStratum basale

Skin ColorSkin Color

Melanocytes produce the Melanocytes produce the primary skin pigment, primary skin pigment, melaninmelanin

Located between cells in Located between cells in the stratum basalethe stratum basale

Skin Color cont’dSkin Color cont’d

Melanin is a dark brown Melanin is a dark brown pigment, more melanin result in pigment, more melanin result in darker skin colorsdarker skin colors

Skin color is not determined by Skin color is not determined by number of melanocytes, but by number of melanocytes, but by how much melanin they produce how much melanin they produce (genetic and environmental (genetic and environmental factors)factors)

Skin Color cont’dSkin Color cont’d

Exposing melanocytes to UV Exposing melanocytes to UV radiation results stimulates radiation results stimulates them to produce more melanin, them to produce more melanin, a process called tanninga process called tanning

Melanin has the ability to Melanin has the ability to absorb UV light, protecting absorb UV light, protecting cells’ DNAcells’ DNA

Skin Color cont’dSkin Color cont’d

Skin color can also Skin color can also receive contributions receive contributions from carotene, a from carotene, a yellowish pigment yellowish pigment (most prominent in (most prominent in Asians, but also Asians, but also present in present in caucasians)caucasians)

The DermisThe Dermis

Dense mat of Dense mat of various various connective connective tissuestissues

Rich with Rich with blood vesselsblood vessels

Consistencey Consistencey of a firm wet of a firm wet spongesponge

The DermisThe Dermis

Papillary region Papillary region – contains – contains several papillae several papillae – form friction – form friction ridgesridges

Reticular Reticular region contains region contains accessory accessory organsorgans

Accessory OrgansAccessory Organs

Hair follicles, finger and toe nails, Hair follicles, finger and toe nails, sebaceous glands, and sweat glands sebaceous glands, and sweat glands are all referred to as are all referred to as epidermal epidermal derivatives derivatives because they all grow because they all grow from cells migrating to the dermis from cells migrating to the dermis from the epidermis during from the epidermis during developmentdevelopment

Blood vessels and nerve receptors Blood vessels and nerve receptors grow in from other areasgrow in from other areas

HairHair Protects skin from Protects skin from

injury that may be injury that may be caused by sunlight or caused by sunlight or foreign particlesforeign particles

Grown from a Grown from a downward growth of downward growth of the epidermis into the the epidermis into the dermis called a follicledermis called a follicle

Portion surrounded by Portion surrounded by follicle called the root, follicle called the root, portion above surface portion above surface is the shaftis the shaft

HairHair

Hair follicle and root consist of Hair follicle and root consist of mostly living cells, nourished from a mostly living cells, nourished from a cluster of blood vessels in the base cluster of blood vessels in the base or bulbor bulb

Growth of hair is similar to Growth of hair is similar to replacement of epidermis; cells are replacement of epidermis; cells are pushed to surfacepushed to surface

Hair is made mostly of keratinized Hair is made mostly of keratinized cellscells

HairHair

Hair grows at a rate of 1mm every 3 Hair grows at a rate of 1mm every 3 daysdays

Cutting or shaving it have no effect on Cutting or shaving it have no effect on rate of growthrate of growth

Body regions differ in hair growth rateBody regions differ in hair growth rate Approx. 100 scalp hairs are lost dailyApprox. 100 scalp hairs are lost daily Hair color determined by amt. of Hair color determined by amt. of

melanin present (blonde, brown, or melanin present (blonde, brown, or black); white by decrease in black); white by decrease in production of melanin and air in shaftproduction of melanin and air in shaft

Sebaceous GlandsSebaceous Glands

Also known as oil glands; associated with Also known as oil glands; associated with hair follicles, connected to follicle by a hair follicles, connected to follicle by a ductduct

Produce an oily secretion called sebum Produce an oily secretion called sebum (consists of water, fats, cholesterol, (consists of water, fats, cholesterol, protein, and salt)protein, and salt)

Sebum keeps hair and skin soft and Sebum keeps hair and skin soft and pliable, also increases water-resistancepliable, also increases water-resistance

Production of sebum is accelerated by sex Production of sebum is accelerated by sex hormoneshormones

Sebaceous GlandsSebaceous Glands

May become clogged by excess May become clogged by excess sebum, dead cells, or environmental sebum, dead cells, or environmental debris; forms blackheadsdebris; forms blackheads

If bacteria become established, If bacteria become established, forms a pimple or boilforms a pimple or boil

Sebaceous glands are distributed Sebaceous glands are distributed evenly over entire body except on evenly over entire body except on palms and solespalms and soles

Sebaceous Gland Sebaceous Gland (Yellow)(Yellow)

Sweat GlandsSweat Glands

Also known as sudoriferous glandsAlso known as sudoriferous glands Come in two varieties, eccrine and Come in two varieties, eccrine and

apocrineapocrine Eccrine – present entire life, Eccrine – present entire life,

secrete a watery sweat, function secrete a watery sweat, function primarily in coolingprimarily in cooling

Eccrine glands are distributed Eccrine glands are distributed throughout the bodythroughout the body

Sweat GlandSweat Gland

Apocrine GlandsApocrine Glands

Apocrine – become active during Apocrine – become active during puberty, secrete a thick sweat, highest puberty, secrete a thick sweat, highest concentration located in armpits and concentration located in armpits and groingroin

Proteins in apocrine sweat promote Proteins in apocrine sweat promote growth of bacteria normally found on growth of bacteria normally found on skin; bacteria produce odoriferous skin; bacteria produce odoriferous materialsmaterials

Active primarily in times of emotional Active primarily in times of emotional stressstress

NailsNails Formed from compressed outer Formed from compressed outer

layer of epidermis; mostly layer of epidermis; mostly keratinkeratin

Protect ends of fingers and Protect ends of fingers and toes, function in very fine toes, function in very fine grippinggripping

Visible surface of nail is the Visible surface of nail is the nail bodynail body, covered by flap of , covered by flap of stratum corneumstratum corneum, the , the cuticlecuticle

Deep to cuticle is nail root, Deep to cuticle is nail root, active stratum basale known active stratum basale known as as nail matrixnail matrix

Small, crescent-shaped Small, crescent-shaped portion of matrix is visible, portion of matrix is visible, called the called the lunulalunula

ReceptorsReceptors

Usually consist of the distal ends of Usually consist of the distal ends of nerve cells that are wrapped in nerve cells that are wrapped in connective tissueconnective tissue

Carry impulses toward the brain, Carry impulses toward the brain, millions found in the skinmillions found in the skin

Interpreted by the brain as heat, Interpreted by the brain as heat, pressure, fine touch, and painpressure, fine touch, and pain

Give important information necessary Give important information necessary for maintaining homeostasisfor maintaining homeostasis

HypodermisHypodermis

Connects skin to muscles beneathConnects skin to muscles beneath Contains loose connective tissue, Contains loose connective tissue,

adipose tissue, and dense connective adipose tissue, and dense connective tissuetissue

Insulates deep tissues from extremes Insulates deep tissues from extremes of heat and cold, also provides shock of heat and cold, also provides shock absorbing cushion and energy absorbing cushion and energy storagestorage

Temperature RegulationTemperature Regulation

Blood vessels in the dermis dilate Blood vessels in the dermis dilate (enlarge) or constrict (shrink) to (enlarge) or constrict (shrink) to release more or less heat to the release more or less heat to the environmentenvironment

Evaporation of sweat is an important Evaporation of sweat is an important factor in coolingfactor in cooling

Goosebumps and shivering warm up Goosebumps and shivering warm up the bodythe body