chapter 4: skin and body membranes

body membranes

function: cover body surfaces, line body cavities, form protective sheets around organs

classified according to tissue types

As cells progress from the deeper portion of the epidermis toward the surface, _______.

they tend to die

epithelial membranes

covering or lining

cutaneous membranes

skin

mucous membranes

mucosa

line body cavities open to the exterior (digestive, respiratory, urinary, reproductive)

serous membranes

mostly line body cavities closed off to the exterior

synovial membranes

connective tissue

provide fibrous yet smooth surfaces

cutaneous membrane

skin

dry membrane, outermost protective boundary

Superficial epidermis is composed of
keratinized stratified squamous epithelium
•Underlying dermis is mostly dense
connective tissue

stratified squamous epithelium

mouth, esophagus

mucous membrane

simple columnar epithelium

rest of digestive tract

mucous membrane

serous membranes

surface is layer of simple squamous epithelium

underlying layer is a thin layer of areolar connective tissue

lines open body cavities that are closed to the exterior of the body

occur in pairs seperated by serous fluid

visceral layer

covers the outside of the organ

parietal layer

lines a portion of the wall of ventral body cavity

peritoneum

abdominal cavity

pleura

around the legs

pericardium

around the heart

synovial membrane

connective tissue, lines fibrous capsules surrounding joints; secretes a lubricating fluid called synovial fluid

skin derivatives

sweat glands, oil glands, hair, nails

skin functions

protects deeper tissue from:

mechanical damage (bumps)

chemical damage (acids and bases)

bacterial damage

ultraviolet radiation

thermal damage (heat or cod)

dessication (drying out)

aids in body heat loss or heat retention as controlled by the nervous system

synthesizes vitamin D

epidermis

outer layer

Stratified squamous epithelium
•Cornified or keratinized (hardened by
keratin) to prevent water loss
•Avascular
•Most cells are keratinocytes

dermis

dense connective tissue

subcutaneous tissue (hypodermis_

deep to dermis

Not technically part of the skin
•Anchors skin to underlying organs
•Composed mostly of adipose tissue

stratum basale (stratum germinativum)

deepest layer, lies next to dermis, wavy borderline w dermis anchors two together

cells undergoing mitosis

daughter cells are pushed upward to become most superficial layers

stratum spinosum

several layers of cells that contain thick, weblike bundles of intermediate filaments made of pre keratin protein. cells in this ayer appear spiky

stratum granulosum

a thin layer named for the abundant granules its cells contain. at the upper border of this layer, cells are beginning to die

stratum lucidum

formed from dead cells of the deeper strata

occurs only in thick, hairless skin of palms of hands and soles of feet

stratum corneum

outermost layer of epidermis

shingle-like dead cells are filled with keratin (protective protein prevents water loss from skin)

Summary of layers from deepest to most
superficial

Stratum basale
•Stratum spinosum
•Stratum granulosum
•Stratum lucidum (thick, hairless skin only)
•Stratum corneum

melanin

Pigment (melanin) produced by melanocytes
•Melanocytes are mostly in the stratum basale
•Color is yellow to brown to black
•Amount of melanin produced depends upon
genetics and exposure to sunlight

dermis

two layers: reticular and papillary layer

Collagen and elastic fibers located
throughout the dermis
•Collagen fibers give skin its toughness
•Elastic fibers give skin elasticity
•Blood vessels play a role in body
temperature regulation

papillary layer

(upper dermal region)
• Projections called dermal papillae
• Some contain capillary loops
• Others house pain receptors and touch
receptors

reticular layer

(deepest skin layer)
• Blood vessels
• Sweat and oil glands
• Deep pressure receptors

carotene

Orange-yellow pigment from some vegetables

Hemoglobin

Red coloring from blood cells in dermal capillaries
Oxygen content determines the extent of red
coloring

Cutaneous glands

are all exocrine glands
•Sebaceous glands
•Sweat glands
•Hair
•Hair follicles
•Nails

Oil (sebaceous) glands

•Produce oil (sebum)
•Lubricant for skin
•Prevents brittle hair
•Kills bacteria
•Most have ducts that empty into hair
follicles; others open directly onto skin
surface
•Glands are activated at puberty

Sweat (sudoriferous) glands

•Produce sweat
•Widely distributed in skin

Two types of sudoriferous glands

eccrine and apocrine

ecrine

Open via duct to pore on skin surface
•Produce sweat (clear)

Apocrine

•Ducts empty into hair follicles
•Begin to function at puberty
•Release sweat that also contains fatty
acids and proteins (milky/yellowish color)

associated with the skin of the genitals and the axillary region

sweat

Composition
• Mostly water
• Salts and vitamin C
• Some metabolic waste
• Fatty acids and proteins (apocrine only)
Function
• Helps dissipate excess heat
• Excretes waste products
• Acidic nature inhibits bacteria growth
• Odor is from associated bacteria

hair

Produced by hair follicle
•Consists of hard keratinized epithelial cells
•Melanocytes provide pigment for hair color
•Hair grows in the matrix of the hair bulb in
stratum basale

anatomy

• Central medulla

• Cortex surrounds medulla

• Cuticle on outside of cortex

• Most heavily keratinized

hair follicle

Dermal and epidermal sheath surround
hair root

arrector pili muscle

Smooth muscle
•Pulls hairs upright when cold or frightened

responsible for goosebumps

Sebaceous gland

Sudoriferous gland

nails

Scale-like modifications of the epidermis
•Heavily keratinized
•Stratum basale extends beneath the nail bed
•Responsible for growth
•Lack of pigment makes them colorless

nail structures

Free edge
•Body is the visible attached portion
•Root of nail embedded in skin
•Cuticle is the proximal nail fold that projects
onto the nail body

burns

Tissue damage and cell death caused by
heat, electricity, UV radiation, or chemicals
•Associated dangers
•Dehydration
•Electrolyte imbalance
•Circulatory shock

rule of nines

Way to determine the extent of burns
•Body is divided into 11 areas for quick
estimation
•Each area represents about 9 percent of total
body surface area

first degree burns

Only epidermis is damaged
• Skin is red and swollen

second degree burns

Epidermis and upper dermis are damaged
• Skin is red with blisters

Third-degree burns

• Destroys entire skin layer; burned area is painless
• Burn is gray-white or black

critical burns

Burns are considered critical if
•Over 25 percent of body has second-degree
burns
•Over 10 percent of the body has third-
degree burns
•There are third-degree burns of the face,
hands, or feet

infections

Athlete’s foot (tinea pedis)
•Caused by fungal infection
Boils and carbuncles
•Caused by bacterial infection
Cold sores
•Caused by virus

infections and allergies

Contact dermatitis
•Exposures cause allergic reaction
Impetigo
•Caused by bacterial infection
Psoriasis
•Cause is unknown
•Triggered by trauma, infection, stress

skin cancer

Cancer—abnormal cell mass
•Classified two ways
•Benign
•Malignant

benign

Does not spread (encapsulated)

malignant

•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
•Cancer of melanocytes
•Metastasizes rapidly to lymph and blood
vessels
•Detection uses ABCD rule

ABCD rule

A = Asymmetry
•Two sides of pigmented mole do not match
•B = Border irregularity
•Borders of mole are not smooth
•C = Color
•Different colors in pigmented area
•D = Diameter
•Spot is larger then 6 mm in diameter