Integumentary System

Functions

1. Covers and protects the body

What does the skin protect us from? Pathogens Injury Ultra-violet

radiation

Functions2. Regulate body

temperatureHow does it

regulate temperature?SweatingDilate/constrict

of blood vesselsGoose bumps

Functions

3. Excretes WasteWhatwastes are excreted?

Urea as sweat

subcutaneous

Functions4. Reduces water loss

Keeps the body from drying out!

Functions5. Houses sensory receptors

Mechano Chemo

Photo

Chemo

Mechano

Four basic types of integumentary tissue

Epithelium – epidermisConnective tissue - dermisMuscle tissueNervous tissue

There are 2 main layers of skin

I. Epidermis

II. Dermis

Epidermis Keratinized stratified squamous epithelium Four types of cells

Keratinocytes – deepest, produce keratin (tough fibrous protein)

Melanocytes - make dark skin pigment melanin Merkel cells – associated with sensory nerve endings Langerhans cells – macrophage-like dendritic cells

Layers (from deep to superficial) Stratum basale or germinativum – single row of cells

attached to dermis; youngest cells Stratum spinosum – spinyness is artifactual;

tonofilaments (bundles of protein) resist tension Stratum granulosum – layers of flattened keratinocytes

producing keratin (hair and nails made of it also) Stratum lucidum (only on palms and soles) Stratum corneum – horny layer (cells dead, many layers

thick) (see figure on next slide)

Deadkeratinocytes

Lamellar granules

Keratinocyte

Langerhans cell

Melanocyte

Merkel cell

Tactile discSensory neuron

Stratumcorneum

Stratumlucidum

Stratumgranulosum

Stratumspinosum

Stratumbasale

Dermis

Epidermis

Outer (surface) layers of skin10-30 cells thick

Two Parts:Inner part composed of living cellsOuter part is of dead cells

Epidermis Inner layers

Lowest layer of cells reproduce and push older cells toward the surface.

As cells near the surface, they flatten and their organelle disintegrate

These cells also begin producing Keratin a tough, fibrous protein.

This replaces cytoplasm.

Epidermis Inner layers

Epidermis – Outer layersThe Keratin producing

cells die as they move toward the surface.

Outer dead layer waterproofs and protects inner layers

It is shed continually and is completely replaced in 2 - 4 weeks

Epidermis

What do we find in the epidermis?Melanocytes

What are melanocytes?Cells that produce melanin.

What is melanin?A dark brown pigment

What does melanin do?Gives skin it’s colorProtects sensitive dermis from U-V radiation

Skin colorThree skin pigments

Melanin: the most importantCarotene: from carrots and yellow

vegiesHemoglobin: the pink of light skin

Melanin in granules passes from melanocytes (same number in all races) to keratinocytes in stratum basaleDigested by lysosomesVariations in colorProtection from UV light vs vitamin D?

EpidermisMelanocytesDo some people havemore melanocytesthan other people?

EpidermisSkin pigmentation is

due to the type and amount of melanin produced

Eumelanin produces darker pigments

Phaeomelanin produces lighter pigments and freckles

These often occur together in varying amounts

DermisDeeper layers of skin10-20 times thickerthan epidermis.

Top layer arrangedIn ridges.

Ridges help the epidermis bind to

the dermis.The uneven ridgescreate fingerprints

Dermis

Accessory Organs of the Dermis1. Hair follicles – tube-like depression

where the hair develops

Hair and hair follicles: complexDerived from epidermis and dermisEverywhere but palms, soles, nipples, parts of genitalia

*“arrector pili” is smooth muscle*

Hair papilla is connective tissue________________

Hair bulb: epithelial cells surrounding papilla

Functions of hairWarmth – less in man than other

mammalsSense light touch of the skinProtection - scalp

PartsRoot imbedded in skinShaft projecting above skin surface

Make up of hair – hard keratinThree concentric layers

Medulla (core)Cortex (surrounds medulla)Cuticle (single layers, overlapping)

Types of hair Vellus: fine, short hairs Intermediate hairs Terminal: longer, courser hair

Hair growth: averages 2 mm/week Active: growing Resting phase then shed

Hair loss Thinning – age related Male pattern baldness

Hair color Amount of melanin for black or brown; distinct

form of melanin for red White: decreased melanin and air bubbles in

the medulla Genetically determined though influenced by

hormones and environment

Accessory Organs of the Dermis2. Sebaceous glands – secret oily

sebum to soften and waterproof skin

Sebaceous (oil) glandsEntire body except palms and solesProduce sebum by holocrine secretionOils and lubricates

Accessory Organs of the Dermis3. Nails – protective covers of ends of

fingers and toes.

NailsOf hard keratinCorresponds to hooves and clawsGrows from nail matrix

Accessory Organs of the Dermis4. Sweat glands:

secrete waste regulate heatproduces ear waxproduces milk during lactation

Sweat glandsEntire skin surface except nipples and part of

external genitalia

Prevent overheating

500 cc to 12 l/day! (is mostly water)

Humans most efficient (only mammals have)

Produced in response to stress as well as heat

Types of sweat glands

Eccrine or merocrine Most numerous True sweat: 99% water, some salts, traces of

waste Open through pores

Apocrine Axillary, anal and genital areas only Ducts open into hair follices The organic molecules in it decompose with

time - odorModified apocrine glands

Ceruminous – secrete earwax Mammary – secrete milk

Types of sweat glandsEccrine or merocrine

Most numerous True sweat: 99% water, some salts, traces of

waste Open through pores

Apocrine Axillary, anal and genital areas only Ducts open into hair follices The organic molecules in it decompose with

time - odorModified apocrine glands

Ceruminous – secrete earwax Mammary – secrete milk

Accessory Organs of the Dermis5. Blood vessels – to nourish skin cells

Accessory Organs of the Dermis6. Nerves – to send and receive

messages

Subcutaneous

Accessory Organs of the Dermis7. Erector pilli muscle

-smooth muscle-causes

“goosebumps”-causes

hair to stand erect

subcutaneous

Subcutaneous layer – connective tissueAnchors dermis to the bodyContains fatcells to protectand cushion

Subcutaneous layer

Some disorders of the integumentary systemBurns

Threat to life Catastrophic loss of body fluids Dehydration and fatal circulatory shock Infection

Types First degree – epidermis: redness (e.g.

sunburn) Second degree – epidermis and upper dermis:

blister Third degree - full thickness

InfectionsSkin cancer

Disorders of the integumentary systemBurns

Threat to life Catastrophic loss of body fluids Dehydration and fatal circulatory shock Infection

Types First degree – epidermis: redness (e.g.

sunburn) Second degree – epidermis and upper dermis:

blister Third degree - full thickness

InfectionsSkin cancer

Interesting Tidbits

Your body is composed of approximately 100 Trillion cells

About 16% of your body weight is skinThe skin is completely renewed every 27

daysYou will make almost 1000 new skins in a

lifetime If all the layers of your skin were laid out

on the ground, it would cover about 20 m2 or 2 parking spaces

Interesting TidbitsA fingernail or toenail takes about 6

months to grow from base to tipFingernails grow faster than

toenailsAn average human scalp has

100,000 hairsWe lose between 40 and 100 hairs

per dayBlondes have more hair than

brunettes

Interesting TidbitsFingerprints provide traction for grasping

objectsEven identical twins have different

fingerprintsEvery square inch of dermis contains

twenty feet of blood vesselsSkin on our hands and feet is thicker.

When we bathe, skin takes on water and swells slightly.

In the thicker areas, increased surface area creates crowding. The skin must wrinkle to accommodate the changes

Interesting TidbitsFriction of the epidermis causes cell

division to increase.This outward thickening is called a

callous.Sometimes growth is inward, creating a

corn.Humans shed about 600,000 particles of

skin per hour – about 1.5 pounds per year.

At age 70, you will have lost about 105 lbs of skin.