SKIN AND BODY MEMBRANESChapter 4

BODY MEMBRANES-FUNCTIONS

Line or cover body surfaces Protect body surfaces Lubricate body surfaces

EPITHELIAL MEMBRANES

Made of epithelium connected to underlying connective tissue

Skin Cutaneous

membrane Exposed to air = Dry

membrane Made of keratinized

stratified squamous epithelium

EPITHELIAL MEMBRANES, CONT.

Mucous membranes Type of epithelium depends on location of

membrane Most are stratified squamous OR simple columnar

Lines all body cavities open to exterior Respiratory tract Digestive tract Urinary & Reproductive tracts

Wet membranes (bathed in secretions continuously)

Underlying connective tissue is lamina propria

EPITHELIAL MEMBRANES, CONT. Serous Membranes

Simple squamous tissue on areolar tissue Line cavities that are closed to exterior Occur in pairs

Parietal layer-lines wall of a cavity Visceral layer-covers the outside of the organs inside the

cavity Layers separated by fluid secreted by both

membranes Allows organs to slide easily across cavity walls and each

other Reduces friction (good for heart pumping, stomach

churning, etc) Peritoneum-lining of abdominal cavity/covers organs Pleura-surrounds lungs Pericardium-surrounds heart

EPITHELIAL MEMBRANES, CONT.

CONNECTIVE TISSUE MEMBRANES

Synovial Membranes Made of areolar

tissue-NO epithelial cells

Line joint capsules Provide smooth

surface Secrete fluid for

lubrication (reduces friction)

Also provide cushion for movements of tendons over bones Tendon sheath

INTEGUMENTARY SYSTEM

AKA…SKIN! AKA…Cutaneous membrane AKA…Integument

Means “covering” Keeps water and nutrients IN the body Keeps water and other things OUT

We don’t get waterlogged when we shower or swim!

SKIN FUNCTIONS

Protects body from: Mechanical damage (bumps)

Physical barrier and pressure receptors Chemical damage

Impermeable cells; pain receptors Bacterial damage

Skin secretions acidic; inhibit bacteria UV radiation

Contains melanin Thermal damage

Heat/cold damage Has heat/cold/pain receptors

Dessication Drying out

SKIN FUNCTIONS, CONT.

Aids in heat loss/retention Activates sweat glands and allows blood to flush

into capillaries for heat loss Not allowing blood to flush into capillaries for

heat retention Helps excrete urea and uric acid

Sweat glands Makes vitamin D

Sunlight converts cholesterol in skin to vitamin D

SKIN STRUCTURE Epidermis

Outer layer Keratinized stratified

squamous cells No blood supply of its

own (avascular) Dermis

Dense connective tissue

Can separate from epithelium due to burns/friction

Causes blisters

Hypodermis (Subcutaneous Tissue) Technically…not part

of skin Adipose (fat) Anchors skin to

underlying organs Shock absorber Insulates deeper

tissues from extreme temp. changes

EPIDERMIS LAYERS

Stratum basale Deepest layer Next to dermis Cells are undergoing mitosis

AKA Stratum germinativum Cells get nutrients via diffusion from dermis Cells get pushed up to move farther away from

nutrient supply Stratum spinosum Stratum granulosum

EPIDERMIS LAYERS, CONT.

Stratum lucidum Clear, flattened cells full of keratin Only in areas where skin is hairless and extra thick

Palms of hands Soles of feet

Stratum corneum Outermost layer Shingle-like cells Dead cells Provides protective “coat” for body Rubs/flakes off slowly We have a totally new epidermis approximately

every month!

MELANIN

Pigment produced by melanocytes In stratum basale

Exposure to sunlight causes melanocytes to make melanin

More melanin = more skin pigmentation = TAN

Amount of melanin produced depends on: Amount of sun exposure Genetics

Freckles/Moles Concentration of melanin in one spot

DERMIS

“Hide” Strong, stretchy, holds body together Two regions

Papillary layer Contains fingerlike projections “dermal papillae” Has capillary loops for nutrient supply Pain/touch receptors Makes up our fingerprints (whorls, ridges)

Reticular layer Deepest skin layer Contains blood vessels, sweat glands, oil glands Has pressure receptors

SKIN STRUCTURE

SKIN COLOR DETERMINATION

Amount/kind of melanin in epidermis Can be yellow, reddish brown, or black

Amount of carotene Yellowish-orange pigment (think carrots)

If you eat LOTS of foods this color, your skin will look this color also!

Hemoglobin Protein in red blood cells-carries oxygen

Lots of melanin = brown toned skin Oxygen rich hemoglobin causes skin to look

pink When Caucasians look “flushed”

IMBALANCES Cyanosis

When oxygen content in blood is low

Bluish-tinted skin (“cyan”)

Erythema Redness/”flushing” Caused by blood

rushing to capillaries near skin’s surface

Pallor/blanching Pale skin Can be due to

anemia, low BP, impaired blood flow

Jaundice Abnormal yellow skin

tone Can be due to liver

disorder Bruises

Sites where blood has escaped from circulation and clotted

Tendency toward unusual bruising could mean vit. C deficiency or hemophilia

SKIN APPENDAGES

Cutaneous Glands Exocrine glands

Release secretions to surface of skin through ducts Two types:

Sebaceous glands Sweat glands

SEBACEOUS (OIL) GLANDS

All over skin EXCEPT hands/feet

Ducts empty into hair follicle

Release sebum Oily substance and cell

fragments Lubricant

Keeps skin soft, keeps hair from being brittle

Antibacterial properties Glands become more

active during puberty

Pimples! Whitehead

Caused by blocked sebaceous gland

Blackheads When material inside

whitehead dries out

Cradle cap (seborrhea) In infants

Sebaceous glands are overactive

Looks like lots of oily dandruff on scalp

SWEAT GLANDS (SUDORIFEROUS GLANDS)

Eccrine Glands More numerous/all

over body Open to pores on

skin surface Produce sweat Important for heat

regulation

Apocrine Glands Only found in

axillary and genital areas

Larger than eccrine glands

Ducts empty into hair follicles

SWEAT Composition

Mostly water Waste products Fatty acids and

proteins (from apocrine glands only)

Color Clear (eccrine) Milky white/yellowish

(apocrine…due to FA’s and proteins)

Function Heat regulation (gets

rid of excess heat) Waste excretion Acidic-naturally

inhibits bacteria Odor

Sweat is ODORLESS!! The smell is from

bacteria on skin When bacteria use

sweat for nutrients, it is smelly!

SKIN APPENDAGES

Hair Produced by hair

bulb Made of keratinized

epithelial cells (dead…mostly protein)

Color comes from pigment in melanocytes

Found everywhere EXCEPT palms, soles, nipples, lips

HAIR ANATOMY Medulla

Central core Cortex

Surrounds medulla Cuticle

Outermost layer Single layer of

overlapping cells (like shingles)

Has the most keratin Provides strength Split Ends?

Caused when cuticle is worn away at the tip of the hair shaft…keratin frizzes out…hair “splits”

OTHER HAIR-RELATED STRUCTURES Hair Follicle

Inner epidermal sheath= hair

Outer dermal sheath= connective tissue

Supplies blood to epidermis

Arrector pili Smooth muscle Connects hair follicle to

dermis When contracted, we

see “goose bumps” and hairs are pulled upright

Sebaceous glands

SKIN APPENDAGES Nails

Modification of epidermis

Scale-like Contain lots of keratin Mostly non-living

material

Stratum basale under nail bed resposible for growth

Colorless No pigment Appear pink due to blood

supply in underlying dermis

BURNS

Tissue damage/cell death caused by heat, electricity, UV radiation (sunburn/tanning bed), chemicals

Can result in life-threatening problems Dehydration-lose fluid supply, electrolyte

imbalance Leads to kidney shutdown and circulatory shock Lost fluids must be replaced immediately!

BURNS

Rule of Nines How to estimate

fluid loss from a burn

Divides body into different regions, each being 9% (except genital area is 1%)

BURN CLASSIFICATION

First-degree Only epidermis is

damaged Red, swollen Regeneration occurs Ex: sunburn

Second-degree Damage to

epidermis and upper dermis

Red, painful, blisters Regeneration occurs

Third-degree Full-thickness burn Grayish white or

black (looks charred) Destroys nerve

endings Not painful

Regeneration NOT possible Must use skin grafting

BURNCLASSIFICATION

CRITICAL BURNS

Over 25% of body has second-degree burns

Over 10% of body has third-degree burns

There are third-degree burns on face, hands, or feet

Facial burns dangerous Possible burned

airways Can swell, cause

suffocation

Joint injuries Scar tissue can limit

joint mobility

SKIN CANCER

Most common type of cancer Risk factors:

Overexposure to UV radiation (sun/tanning bed)

Frequent skin infections or chemical irritation

Two Types Benign

Do not spread Malignant

Metastasizes (moves) to other parts of body

SKIN CANCER

Basal Cell Carcinoma Least malignant Most common Occur most often on

sun-exposed areas Slow-growing 99% have full cure if

lesion is removed surgically

Squamous Cell Carcinoma Scaly, red; eventually

forms shallow ulcer with raised border

Occurs most often on scalp, ears, hands, lip

Fast-growing Good chance of cure

if removed surgically or use radiation therapy

SKIN CANCER

Malignant Melanoma Cancer of

melanocytes (cells that make melanin)

5% of skin cancers Often deadly Can begin anywhere

there is pigment Develops

spontaneously, some from moles

50% survival rate

Examine skin for new moles or pigmented spots periodically

Use ABCD Rule of Detection

ABCD RULE OF DETECTION (A) Asymmetry

Two sides of mole do not match

(B) Border irregularity Borders of

mole/lesion are not smooth

(C) Color Spot has areas of

different colors instead of being one color throughout

(D) Diameter Spot larger than

6mm (larger than pencil eraser)