Integumentary System

Anatomy & Physiology

Body Membranes

Cover surfaces, line body cavities and form protective sheets around organs

2 major groups Connective tissue membranes Epithelial membranes

Connective Tissue Membranes

AKA synovial membranes Made of connective tissue, no epithelial cells Line fibrous capsules of synovial joints, bursae

and tendons Secrete a lubricating fluid, providing a smooth

surface

Epithelial Membranes

1. Mucous membranes Typically stratified squamos epithelium or simple

columnar epithelium Epithelium resting on the lamina propria

(connective tissue sheet) Many secrete a mucous Lines all cavities open to the exterior; very moist Functions in absorption and secretion

Epithelial Membranes

2. Serous Membranes Layer of simple squamos epithelium laying on layer of

areolar tissue Lines cavities closed to exterior Occur in pairs

Parietal layer lines the wall of the cavity Visceral layer lines the organ within that cavity Cavities separated by serous fluid Fluid allows for decreased friction between mobile organs

and cavity walls

Epithelial Membranes

3. Cutaneous Membrane Aka the skin Exposed to air and is a dry membrane

The Integumentary System

The skin, hair, nails, sweat and oil glands Mostly functions in protection but there are 6

separate functions of the skin 1.) Protection 2.) Body Temp. Regulation 3.) Cutaneous Sensation 4.) Metabolic Functions 5.) Blood Reservoir 6.) Excretion

Skin Functions

1. Protection: 3 types of barriers A. Chemical barriers

Includes skin secretions and melanin Acid mantle: kills bacteria on skin

B. Physical Barrier Provided by continuity of the skin and hardness of

keratinized cells Glycolipids: waterproof skin, blocking water & water

soluble substances Only lipid solubles can pass through

CO2, O2, oleoresins, vitamins A,D,E & K

Skin Functions

C. Biological Barrier Langerhan’s cells and macrophages

2.) Body Temp. Regulation Elevated: Blood vessels dilate & sweat glands

are stimulated Lowered: Blood vessels constrict to conserve

body heat

Skin Functions

3.) Cutaneous Sensation Exteroreceptors respond to external stimuli

4.) Metabolic Functions Sunlight reacts with cholesterol in the body to form vitamin

D which helps to metabolize calcium 5.) Blood Reservoir

Holds large volumes of blood 6.) Excretion

Wastes eliminated through sweat

Skin Regions

Skin contains 2 major skin regions: dermis and epidermis

1. Epidermis: thick, stratified squamos epithelium Contains 4 different types of cells

Keratinocytes Melanocytes Langerhans cells Merkel cells

Epidermis Cell Types

1.) Keratinocytes Makes keratin Renews every 25-45

days Found throughout

epidermis Younger cells found in

deeper layers Cells start to die as they

reach the surface

2.) Melanocytes Makes the pigment

melanin Accumulates on the

sunny side of the cell Forms a pigment shield

against UV rays

Epidermis Cell Types

3.) Langerhans From bone marrow A type of macrophage Activates immune

system

Can you break the word macrophage down?

4.) Merkel Cells Sensory receptors for

touch

Epidermal Skin Layers

Thick skin: has 5 layers of skin Thin skin: only has 4 layers of skin Layers:

Stratum Basale Stratum Spinosum Stratum Granulosum Stratum Lucidum Stratum Corneum

Stratum Basale

The Basal Layer Deepest layer Attached to dermis Only 1 row of cells- the youngest keratinocytes 10-20% of melanocytes

Stratum Spinosum

Prickly Layer Several layers thick Has tension resistant filaments to toughen skin Holds many langerhans, melanocytes and older

keratinocytes

Stratum Granulosum

The Granular Layer 3-5 cell layers thick Contains flattened keratinocytes Water proof glycolipids in extracellular space Plasma membranes thicken

Stratum Lucidum

The Clear Layer Present only in thick skin Holds a few layers of clear, flattened, dead

keratinocytes

Stratum Corneum

The Horny Layer Outermost layer 20-30 cell layers thick Holds keratin and thickened plasma membranes Glycolipids for water proofing

Remember….

The epithelium is AVASCULAR so…. Nutrients diffuse into epidermis from dermis Layers above the granulosum too far away to

receive nutrients from diffusion Dead cells shed from scalp and skin ~ 40-50

pounds in one lifetime

Dermis

The second major skin region Made of flexible connective tissue Functions to bind body together Holds sensory receptors, blood vessels,

lymphatic vessels, hair follicles, oil & sweat glands

Has different cell types and 2 major layers

Dermal Cell Types

Fibroblasts For renewal

Macrophages For protection

White Blood Cells For protection

Dermal Skin Layers

Papillary Layer Thin and superficial Holds many blood vessels Holds dermal papillae: small projections with

nerve endings, capillary loops and touch receptors

Papillae enhance gripping ability on palms and soles

Dermal Skin Layers

Reticular Layer 80% of dermis Made of dense, irregular connective tissue Bundled collagen fibers-run in many directions Collagen gives skin strength and prevents cuts Elastin fibers provide stretch and recoil

Hypodermis

The “other” skin layer Not a major skin region Subcutaneous tissue deep to skin Made of areolar and adipose tissues Stores fat, anchors skin to muscles Shock absorption & insulation

Skin Markings

Dermal Tearings Extreme stretching of

skin Appear as silvery, white

scars AKA Striae: stretch

marks

Blister Separation of epidermal

& dermal layers by a fluid filled pocket

Flexure Lines Dermal modifications Skin attached to deeper

structures to allow joint movements

Skin Color

1.) Melanin:Melanin: only pigment made in skin Ranges from yellowish-red to brown to black Amount and shade varies The number of melanocytes relatively the same among

people 2.) CaroteneCarotene

Yellow to orange pigment Found in plant products Accumulates in stratum corneum and hypodermis

Skin Color

HemoglobinHemoglobin Pinkish hue of fair skin Oxygen carrying protein

in skin Red in oxygenated blood

CyanosisCyanosis Bluish tint due to low

oxygen levels

Redness/ErythemaRedness/Erythema Embarrassment, fever,

inflammation or allergy

JaundiceJaundice Yellow cast Signifies liver problems

Skin Color

Black and Black and BlueBlue Marks Marks Contusions or bruises Broken capillaries

causes blood to leak

Pale skin Emotional stress Low blood pressure Impaired blood flow

Skin Appendages

1. Sweat glands

2. Sebaceous glands

3. Hair

4. Nails

Sweat Glands

AKA Sudoriferous Glands Located everywhere except nipples & external

genitalia Over 25 million glands/person 4 types

Eccrine Apocrine Ceruminous Mammary

Eccrine Glands

Most abundant gland, especially palms, soles & forehead

Pores connect ducts to skin surface Releases sweat: 99% water, salt, vitamin C,

antibodies, wastes (urea), lactic acid Unable to control Assists thermoregulation

Eccrine Glands

Heat induced sweat Starts on forehead and spreads inferiorly

Emotionally induced sweat Begins on palms, soles and armpits, then spreads

Apocrine Glands

Larger glands and ducts Empty into hair follicles Same composition as eccrine sweat +

proteins and fatty substances Viscous, milky/yellow color Odorless, but bacteria decomposes it on skin

creating B.O.

Apocrine Glands

Starts functioning @ puberty Activated during pain and stress Analogous to pheromones in animals

Sweat Glands Continued

Ceruminous In the ear Releases wax to deter

insects & block entry of foreign materials

Mammary glands Specialized sweat glands Secretes milk

Sebaceous Glands

Oil Glands Located everywhere EXCEPT palms and

soles Secretes SEBUM via hair follicles or skin

pores Softens, lubricates hair and skin Stimulated by hormones activated @ puberty Glands involved in acne

Hair and Hair Follicles

Function: Detects stinging insects Guards head from physical trauma, heat loss &

sunlight Eyelashes shield eyes Filters particles & insects from air inhaled through

nose

Hair and Hair Follicles

Structure Made of hard keratin Stronger, more durable Doesn’t flake like soft

keratin of skin

Regions: Root: embedded in the

skin Shaft: projects from skin Shape of shaft

determines hair type Flat, ribbon-like Oval Round

Hair Layers

Hair made of keratinized cells 1. Medulla: central core of hair; large cells

separated by air spaces 2. Cortex: bulky layer; surrounds medulla

with several layers of flattened cells 3. Cuticle: single layer of overlapping cells;

most heavily keratinized

Hair Structure

Hair Parts

Hair Follicle Extends from epidermal

surface into the dermis

Hair Bulb Expanded part of deep

end of follicle

Root Hair Plexus Knot of sensory nerve

endings wrapped around hair bulb

Hair Matrix Actively dividing area of

new hair cells; older cells have more keratin

Hair Parts

Arrector Pili Muscle Small muscle cells Contraction pulls hair follicle to upright position &

dimples skin surface In response to fear and cold

Hair Extras

Split Ends: an abrasion causing cuticle to wear away, allowing cortex and medulla to “frizz out”

Hair color: pigment made by melanocytes Gray and white hairs due

to decreased melanin production

Vellus hair: body hair of kids and adult females; pale and fine

Terminal hair: coarser and longer; darker; grows in response to hormones

Hair Extras

Rate of growth: varies, but on average 2mm/week

Growth cycles: has active and resting stages

Hair life span: Scalp: active for ~4

years; inactive for ~2 months

Lose ~ 90 scalp hairs/day

Eyebrows active for 3-5 months

Nails

Structure: Scale-like modifications of the epidermis Contains hard keratin

Functions: Used as tools Same growth pattern as hair and skin

Skin Development

Lanugo: downy hair “cloak” covering fetus body, shed at birth

Vernix caseosa: white substance made by sebaceaous glands to protect skin in womb

Baby’s skin: thin and transparent, thickens and moistens with age

Skin Development

Adolescence: oily, acne Prime time for skin in 20’s-30’s Visual changes occur due to abrasion,

chemicals, wind and sun, air pollutants and bacteria

Old age: skin thins; decreases elasticity Prevention: good diet, fluids, cleanliness,

sun avoidance