Objectives

To explain the function of the integumentary system.

To identify the components of the epidermis.

To list the strata of the epidermis.

Definitions

Epi – upon, on top of Hypo – under Derm – skin Serous membrane – membranes that

line the body cavities Mucous membrane – membranes that

open to the outside of the body Synovial membrane – Membranes in

our joints

The Integumentary System: An Overview

Introduction

Organs are body structures composed of two or more different tissues.

The skin and its accessory organs make up the integumentary system

Parts of the integumentary system Skin – largest organ in our body Body membranes Hair Nails

Functions:

Protective covering Helps regulate body temperature

(homeostasis) Prevents water loss from deeper

tissues Houses sensory receptors Synthesizes biochemicals Excretes small quantities of waste

Consists of…

Cutaneous membraneEpidermis – Outermost layerDermis – Middle layer

Accessory structures- hair, sweat glands, sebaceous glands etc.

Subcutaneous layer (hypodermis) – innermost layer

Components

Figure 5.1

Cutaneous Membrane Cutaneous membrane is another word for

skin.Dry membrane

Act as protective covering from….Mechanical damage (bumps)Chemical damage (acids and bases)Bacterial damageUV radiationThermal damageDesiccation (drying out)

Cutaneous Membrane

Regulate body temperature Prevent water loss House sensory receptors

Send signals to your brain about what you can feel

Synthesize various biochemicalsLike Vitamin D

3 Layers of Cutaneous Membrane

Epidermis:Structure: Top layer; stratified squamous tissueFunction: protection

Dermis:Structure: middle layer, largest layer. Hair, sweat

glands, nails, oil glands

Hypodermis:Structure: Bottom layer. Loose connective tissue

and adipose tissue.Function: Insulation, houses major blood vessels.

The Epidermis

Thin Skin and Thick Skin The epidermis is composed of layers of

keratinocytes- cells that produce keratinThin skin = four layers (strata)Thick skin = five layers

Figure 5.2

The Epidermis Composed of stratified squamous epithelium Lacks blood vessels Older cells are pushed to the top and harden in

a process called keratinization.

Layers of the epidermis:

Stratum basale/ germinativum (cells undergoing mitosis)

Stratum spinosum Stratum granulosum Stratum lucidum (only occurs in thick, hairless

skin of palms and hands and soles of feet) Stratum corneum (cells filled with keratin to

protect and prevent water loss from skin)

From deep…….

…… to superficial

The Structure of the Epidermis

Figure 5.4

Epidermis Cell Layers Germinative

Basal cells (stem) are reproducing Spinosum- spiny layer Granulosum- grainy layer

Stops dividing, start producing keratin Lucidum

The clear layer found only in thick skin Corneum

Exposed to surface and shed every 2 wks.

Skin color depends on… GeneticsDiffering amounts of melanin and size of melanin

granules

Blood supply Interrupted blood supply leads to cyanosis- blue!

CaroteneOrange-yellow pigment found in orange vegetables

MelaninYellow-brown pigmentProtects deeper cells from UV radiationProduced by melanocytes

Melanocytes

Figure 5.5a, b

Epidermal cells Synthesize vitamin D3 (cholecalciferol) when

exposed to UV

Aids in absorption of calcium and phosphorus- needed for bone strength

Respond to epidermal growth factorGrowthDivisionRepairSecretion

Objectives

The explain the components of the dermis.

To understand why tattoos are permanent.

To identify accessory organs of the integument and explain their function.

The Dermis

Dermal Organization Located between epidermis and subcutaneous

layer Consists of connective tissue with collagen and

elastic fibers within a gel-like substance Anchors accessory structures- hair follicles,

sweat glands, blood vessels etc. Carry nutrients to upper layers of skin and

help regulate temperature. Two components:

Outer papillary layerDeep reticular layer

Layers of the Dermis

Papillary layerAreolar tissueContains blood vessels, lymphatics, sensory

nerves of epidermis

Reticular layerDense irregular connetive tissueContains network of collagen and elastic

fibers to resist tension

Stretch Marks

Caused by excessive stretching of the dermis

Patterns of collagen and elastic fibers form lines of cleavage

Lines of Cleavage of the Skin

Figure 5.7

Hypodermis (subcutaneous)

Elastic areolar tissue and adipose tissue Stabilizes skins position against

underlying organs and tissues Shock absorber and insulator Few capillaries and no vital organs Subcutaneous injection is useful to

administer drugs

Structures Hair papilla

Connective tissue containing capillaries and nerves

RootAnchors hair into skin

ShaftPart we see on the surfaceConsists of three layers

○ Cuticle- overlapping shingle layer○ Cortex- underlying layer- pigments○ Medulla- core of hair

Structures Contd. Sebaceous Glands

Also called holocrine glandsAssociated with hair folliclesDischarge oily substance into hair follicles

(waterproofs and moisturizes the hair shafts)Inhibits growth of bacteriaActivated at puberty

Arrector pili musclePulls on follicle, forcing the hair to stand upCold or emotional states- goosebumps

Anatomy of a Single Hair

Figure 5.9

Hair Follicles and Hair

Hair Follicles

Figure 5.10a-c

Hair

Hairs

Individual hairs develop from cells at the base of the hair follicle, an invagination of the lower epidermis that dips down into the dermis.

As new cells are formed, old cells are pushed outward and become keratinized, forming the hair shaft.

Project deep into the dermis and often into the hypodermis

Hair Color

Melanin produced by melanocytes at the hair papilla

Red hair also contains the pigment trichosiderin

Determined by genetics

Function of Hair Head

Protection from UV lightCushion a light blow to headInsulation

Nostrils, ears, and eyesPrevent entry of particles

SensorySensory nerve fiber at base of every hair

Appendages of the Skin

Appendages of the Skin

Exocrine Glands- Reach Outside

Sebaceous glands (Oil glands)Associated with hairSecrete sebum, which lubricates and

inhibits bacteria growthAcne- condition when they are clogged

Sweat glands (Watery Glands)2 kinds

○ Eccrine: all over the body ○ Apocrine: armpits and groin (hormonal)

Sweat Glands Eccrine – respond to body temperature;

open via duct to pore on skin surface Apocrine – responds to body temperature,

stress; ducts empty into hair follicles Ceruminous glands – modified sweat

glands that secrete wax in the ear canal Mammary glands – modified type of sweat

glands that secrete milk

Sebaceous Glands and Hair

Figure 5.11

Sweat Glands

Figure 5.12 Sweat Glands

Figure 5.12a, b

Sweat and Its Function Composition:

Mostly waterSalts and vitamin CSome metabolic wasteFatty acids and proteins (apocrine only)

Function:Helps dissipate excess heatExcretes waste productsAcidic nature inhibits bacteria growth

Odor is from associated bacteria

Regulation of body temperature Heat may be lost to surroundings from the

skin. Body responds to excessive heat by

dilation of dermal blood vessels and sweating.

Body responds to excessive cooling by constricting dermal blood vessels, inactivation sweat glands and shivering.

Nails

Keratinized cells that protects the tips of fingers and toes

Stratified squamous overlying the nail bedLunula is the most actively growing

region of the nail root

Structures Nail Body

Covers an area of the epidermis called the nail bed

Nail RootWhere nail production occursNot visible on surface

CuticlePortion of stratum corneum

Structure Contd.

LunulaPale crescent area near the root were

blood vessels are absent

Figure 5.13 The Structure of a Nail

Figure 5.13

Loss of Homeostasis in Skin

Skin Homeostatic Imablance Infections

Athlete’s foot (tinea pedis) – fungal infectionBoils and carbuncles – bacterial infectionCold sores – caused by virus

Skin Homeostatic Imbalance

Skin Homeostatic Imabalance Burns

Tissue damage and cell death caused by heat, electricity, radiation, or chemicals

Associated dangers○ Dehydration○ Electrolyte imbalance ○ Circulatory shock

Severity of Burns

First-degree burnsOnly epidermis is damagedSkin is red and swollen

Second-degree burnsEpidermis and upper dermis are damagedSkin is red with blisters

Third-degree burnsDestroys entire skin layerBurn is gray-white or black

Severity of Burns

Critical Burns

Burns are considered critical ifOver 25% of the body has second-degree

burnsOver 10% of the body has third-degree

burnsThere are third-degree burns on the face,

hands, or feet

Healing of Wounds Inflammation – blood vessels dilate and become more

permeableCauses tissues to become red and swollenThis is the body’s normal response to injury

Superficial cuts are filled in by reproducing epithelial cells

Deeper cuts are closed off by clots, covered by scabs and eventually filled in by fibroblasts, making connective tissue.

Blood vessels extend into the area, the injured tissues are replaced, and the scab falls off.

Large wounds leave scars and helping may be accompanied by the formation of granulations.

Skin Cancer

Cancer – unregulated mitotic cell division producing abnormal mass

Classified in two waysBenign – does not spreadMalignant – metastasized (moves) to

other parts of the body

Skin cancer is the most common type of cancer!!

Basal Cell Carcinoma

Least malignant Most common type Arises from stratum basale

Squamous Cell Carcinoma Metastasizes to lymph nodes if not removed

Early removal allows a good chance of cure

Believed to be sun-induced Arises from stratum spinosum

Malignant melanoma Most deadly of skin cancers Caner of melanocytes Metastasizes rapidly to lymph and

blood vessels Detection uses ABCD rule

ABCD rule

A = AsymmetryTwo sides of pigmented mole do not match

B = Border irregularityBorders of mole are not smooth

C = ColorDifferent colors in pigmented area

D = DiameterSpot is lager than 6 mm in diameter

The Skeletal System

• The Skeletal System provides structural support• The Integumentary System

synthesizes vitamin D3, essential for calcium and phosphorus absorption (bone maintenance and growth)

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The Muscular System

• The Muscular System’s facial muscles pull against skin of face, producing expressions important in communication

• The Integumentary System synthesizes vitamin D3 , essential for normal calcium absorption (calcium ions play an essential role in muscle contraction)

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The Nervous System

• The Nervous System controls blood flow and sweat gland activity for thermoregulation; stimulates contraction of arrector pili muscles to elevate hairs

• The Intergumentary System’s receptors in dermis and deep epidermis provide sensations of touch, pressure, vibration, temperature, and pain

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The Endocrine System

• The Endocrine System includes the sex hormones that stimulate sebaceous and apocrine gland activity, and develop secondary sexual characteristics; suprarenal hormones alter blood flow to skin and mobilize lipids from fat cells

• The Integumentary System synthesizes vitamin D3, precursor of calcitriol, a hormone produced by the kidneys

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The Cardiovascular System

• 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

• The Integumentary System’s mast cells produce localized changes in blood flow and capillary permeability

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The Lymphatic System

• The Lymphoid System assists in defending the integument by providing additional macrophages and mobilizing lymphocytes

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

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The Respiratory System

• The Respiratory System provides oxygen and eliminates carbon dioxide

• The Integumentary System’s hairs guard entrance to nasal cavity

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The Digestive System

• The Digestive System Provides nutrients for all cells and lipids for storage by adipocytes

• The Integumentary System synthesizes vitamin D3, needed for absorption of calcium and phosphorus

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The Urinary System

• The Urinary System excretes waste products, maintains normal body fluid pH and ion composition

• The Integumentary System assists in elimination of water and solutes; keratinized epidermis limits fluid loss through skin

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