Body Membranes
 Cover surfaces, line body cavities, and form protective
(and often lubricating) sheets around organs
 Two main categories:
 Epithelial membranes – includes cutaneous, mucous,
and serous membranes
 Connective tissue membranes – synovial membranes
Epithelial Membranes
 Although they contain an epithelial sheet, it is always
combined with an underlying layer of connective
tissue  actually “simple organs”
 Cutaneous membrane (skin)
 Mucous membrane (mucosa)
 Serous membrane (serosa)
Cutaneous membrane
 The skin
 Superficial epidermis composed of a keratinizing
stratified squamous epithelium
 Underlying dermis is mostly dense (fibrous)
connective tissue
 Exposed to air  dry membrane
Mucous Membrane
 Mucosa
 Composed of epithelium resting on a loose connective
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tissue membrane called a lamina propria
Lines all body cavities that open to exterior, such as
those of the hollow organs of the respiratory, digestive,
urinary, and reproductive tracts
Most contain stratified squamous epithelium or simple
columnar epithelium
Adapted for absorption or secretion
A “wet” membrane
Serous Membrane
 Serosa
 Composed of a layer of simple squamous epithelium
resting on a thin layer of areolar connective tissue
 Line body cavities that are closed to exterior except for
dorsal body cavity and joint cavities
 Membranes occur in pairs  parietal layer lines a specific
portion of the wall of the ventral body cavity and folds in
on itself to form the visceral layer, which covers the outside
of the organs in that cavity
 Layers are separated by serous fluid, which is secreted by
both membranes  allows organs to slide easily without
friction
Serous Membrane
 Names depend on location in the body
 Peritoneum – serosa lining abdominal cavity and
covering its organs
 Pleura – serosa surrounding the lungs
 Pericardium – serosa surrounding the heart
Synovial Membrane
 Composed of soft areolar connective tissue; contain no
epithelial cells at all
 Line the fibrous capsules surrounding joints, providing
a smooth surface and secreting a lubricating fluid
 Line small sacs of connective tissue called bursae and
the tube-like tendon sheaths  cushion organs
moving against each other during muscle activity
Skin
 Also called integument, which means “covering”
 Insulates, cushions, keeps water and organs inside
body, protects against UV radiation and bacteria
 Contains many capillaries and sweat glands that play
important role in regulating heat loss
 Synthesizes vitamin D
 Contains receptors that detect touch, pressure,
temperature, and pain
Epidermis
 Outer layer of skin
 Made up of stratified squamous epithelium that is
capable of keratinizing, or hardening
 Avascular
Epidermis
 Five layers (strata)  from inside to outside: stratum
basale, spinosum, granulosum, lucidum, and
corneum
 Most cells are keratinocytes, which produce keratin,
the fibrous protein that makes the epidermis a tough
protective layer
 Stratum basale lies closest to dermis and contains the
only epidermal cells that receive adequate
nourishment via diffusion and produce new cells
 Daughter cells are pushed upward and away
Epidermis
 Stratum lucidum is only found where the skin is
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hairless and thick, such as the palms of hands or soles
of feet
Stratum corneum is outer most layer, 20-30 layers
thick  ¾ of all epidermal thickness
Melanin = pigment that ranges from yellow to brown
to black, produced by melanocytes in stratum basale
Exposure to sunlight stimulates melanin production 
tanning
Freckles and moles form where melanin is
concentrated in one spot
Dermis
 Directly below epidermis
 Made up of dense connective tissue
 Usually firmly connected to epidermis, but sometimes
they separate  could result in blister
Dermis
 Leather goods = dermis of animals
 Two major regions – papillary and reticular
 Papillary = upper dermal region, uneven with
fingerlike projections called dermal papillae
 Dermal papillae contain capillary loops, pain
receptors, and touch receptors  form fingerprints
and footprints
 Reticular = deepest skin layer, contains blood vessels,
sweat and oil glands, phagocytes, and deep pressure
receptors
Dermis
 Collagen and elastic fibers are found throughout
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dermis
Collagen attracts and binds to water
Elastic fibers give young skin elasticity
As we age, number of these fibers decreases 
wrinkles and saggy skin
http://www.youtube.com/watch?v=f46SpiboAew
Hypodermis
 Aka “subcutaneous tissue”
 Essentially adipose tissue
 Helps anchor skin to underlying organs
 Serves as shock absorber and insulation
Skin Color
 Three pigments contribute to skin color:
 The amount and kind (yellow, reddish brown, or black)
of melanin in the epidermis
 The amount of carotene (orange-yellow pigment found
in orange, yellow, or leafy green veggies) deposited in
the stratum corneum and subcutaneous tissue
 The amount of oxygen bound to hemoglobin in the
dermal blood vessels
 Lots of melanin = darker skin
 Oxygen-rich hemoglobin is easier to see in people with
lighter skin
Skin Color Indications
 Cyanosis = skin appears blue when hemoglobin is
poorly oxygenated
Skin Color Indications
 Erythema = Reddened skin, may indicate
embarrassment, fever, hypertension, inflammation, or
allergy
Skin Color Indications
 Pallor (blanching) = pale skin, may indicate
emotional stress, anemia, low blood pressure, or
impaired blood flow
Skin Color Indications
 Jaundice = yellow skin, usually signifies liver disorder
in which bile pigments are absorbed into blood and
deposited in body tissues
Skin Color Indications
 Bruising = black-and-blue marks, reveal sites where
blood has escaped from circulation and clotted in tissue
spaces  hematomas. Excessive bruising can be a sign
of vitamin D deficiency or hemophilia, among other
things
Skin appendages
 Cutaneous glands = exocrine glands (release
secretions to skin surface), fall into two groups
 Sebacious (oil) glands = found all over skin except for
palms of hands and soles of feet, ducts usually empty
into a hair follicle, produce sebum, a mix of oily
substances and fragmented cells. Sebum keeps the skin
lubricated, moist, and soft and helps kill bacteria.
Blocked sebacious glands result in acne (whiteheads and
blackheads)
 Sweat glands = also called sudoriferous glands, two
main kinds: eccrine and apocrine
Sweat glands
 Eccrine glands = more numerous, found all over body,
produce sweat, a clear secretion that is primarily water plus
salts, vitamin C, metabolic wastes, and lactic acid and is
usually acidic. Sweat reaches skin through ducts called
pores (not to be confused with outlets for hair follicles)
 Apocrine glands = generally confined to axillary and
genital areas of body, usually larger in size with ducts that
empty into hair follicles. The secretion contains fatty acids
and proteins in addition to substances found in eccrine
gland secretions. The secretion is odorless on its own, but
when bacteria use its nutrients for growth, it takes on a
“musky” odor. These glands are activated during puberty.
Hair and Hair Follicles
 Serve a few minor protective functions, such as
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guarding the head against bumps, shielding the eyes
(eyelashes and eyebrows), and keeping foreign
particles out of respiratory tract (nose hairs)
Previously provided insulation
Hair is produced by a hair follicle
The part of the hair that is enclosed in the follicle is
the root
The part projecting from the surface is the shaft
Hair and Hair Follicles
 Hair is formed by the division of the well-nourished stratum basale
epithelial cells in the growth zone, or hair bulb matrix, at the inferior
end of the follicle.
 As the daughter cells are pushed farther away from the growing region,
they become keratinized and die, thus making the bulk of the hair shaft
dead material (almost entirely protein)
 Each hair consists of a central core called the medulla, which is
surrounded by a bulky cortex layer, which is enclosed by a cuticle layer.
The cuticle is a single layer of cells that overlap one another like shingles
on a roof.
Hair and Hair Follicles
 Hair pigment is made by melanocytes in hair bulb
 Hair follicles are actually compound structures. The
inner epidermal sheath is composed of epithelial
tissue and forms the hair. The outer dermal sheath is
actually dermal connective tissue, which supplies
blood vessels to the epidermal portion and reinforces
it.
 Arrector pili = small bands of smooth muscle cells
that connect each side of the hair follicle to the dermal
tissue. When they contract, the hair is pulled upright
 “goose bumps”
Nails
 Scalelike modification of the epidermis that corresponds to
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the hoof or claw of other animals
Each nail has a free edge, a body (visible attached portion),
and a root (embedded in skin)
Borders of nail are overlapped by skin folds, called nail folds
Cuticle = thick proximal nail fold
Stratum basale extends beneath nail as nail bed
Nail matrix = thickened nail bed responsible for nail growth
 nail cells become heavily keratinized and die
Nails are transparent and nearly colorless, but look pink due
to rich blood supply in underlying dermis
Lunula = white crescent shape at end of nail
Infections and Allergies
 Athlete’s foot = itchy, red,
peeling condition of the skin
between the toes, resulting
from fungal infection
 Boils and carbuncles =
inflammation of hair follicles
and sebaceous glands, common
on the dorsal neck. Carbuncles
are composite boils typically
caused by bacterial infection.
Infections and Allergies
 Cold sores = small fluid-filled
blisters that itch and sting, caused by
a herpes simplex infection. The virus
remains in a cutaneous nerve until it
is activated by emotional upset,
fever, or UV radiation. Usually found
around lips or oral mucosa of mouth.
 Contact dermatitis = itching,
redness, and swelling of skin,
progressing to blistering, caused by
exposure to chemicals that provoke
an allergic reaction.
Infections and Allergies
 Impetigo = pink, water-filled, raised
lesions, usually around mouth and
nose, that develop a yellow crust and
eventually rupture. Caused by a highly
contagious staph infection, common in
elementary school students.
 Psoriasis = chronic condition
characterized by reddened epidermal
lesions covered with dry, silvery scales,
potentially disfiguring, cause unknown.
Burns
 Burn = tissue damage and cell death
caused by intense heat, electricity, UV
radiation, or certain chemicals
 Damage to skin can affect nearly every
body system, altering metabolism,
immune system, and cardiovascular
system.
 Body loses supply of fluids, dehydration,
electrolyte imbalance
 Rule of nines = helps determine how
much fluid is lost, divides body into 11
areas, each accounting for 9% of total body
surface area, plus additional area
surrounding genitals representing 1%.
Burns
 Burned skin is sterile for ~24 hours
 After that, pathogens such as bacteria and fungi invade
areas where skin has been destroyed and multiply in
the nutrient-rich environment
 Patient’s immune system becomes depressed within
one to two days after severe burn injury
Burns
 Classified by severity
 1st degree burns = only epidermis is
damaged, area becomes red and swollen,
usually heals in 2-3 days
 2nd degree burns = damage to epidermis
and upper layer f dermis, skin is red and
painful, blisters appear, regeneration of
epithelium can occur, no scars if care is
taken to prevent infection
 3rd degree burns = destroy entire thickness
of skin, burned area appears blanched
(grey-white) or blackened, nerve endings
destroyed  burned area is not painful,
regeneration is not possible, skin grafts
required
Burns
 Considered critical if:
 1. Over 25% of the body has second-degree burns
 2. Over 10% of the body has third-degree burns
 3. There are third-degree burns of the face, hands, or
feet
 Facial burns are dangerous because of the possibility
of burned respiratory passageways, which can swell
and cause suffocation
 Severe burns at joints can result in scar tissue that
limits joint mobility
Skin Cancer
 Most skin tumors are benign and do not
metastasize to other areas (ex. warts), but
some are malignant
 http://video.about.com/dermatology/SkinCancer.htm
 Basal cell carcinoma = least malignant and
most common skin cancer, cells of stratum
basale proliferate and invade dermis and
subcutaneous tissue, appear as shiny, dome
shaped nodules which develop central ulcers
with “pearly” beaded edges. Because it is so
noticeable and slow-growing, metastasis rarely
occurs. When removed surgically, there is a
99% chance for a full cure.
Skin Cancer
 Squamous cell carcinoma = arises
from cells in stratum spinosum, lesion
appears as a scaly, reddened papule
that gradually forms a shallow ulcer
with a firm, raised border, usually
found on scalp, ears, hands, and lower
lip. Grows rapidly and metastasizes to
adjacent lymph nodes if not removed,
believed to be sun-induced. If caught
early and removed, chance of
complete cure is good.
Skin Cancer
 Malignant melanoma = cancer of
melanocytes, accounts for only 5% of skin
cancers, often deadly, can begin anywhere
there is pigment, most appear spontaneously,
but some develop from moles. Usually
appears as spreading brown to black patch
that metastasizes rapidly to surrounding
lymph and blood vessels, ~50% survival rate,
early detection helps, ABCD rule:
 Asymmetry – two sides of pigmented mole
do not match
 Border irregularity – borders are not
smooth, but show indentations
 Color – pigmented spot contains areas of
different colors
 Diameter – spot is larger than 6 mm in
diameter (pencil eraser)
Developmental Aspects of Skin and
Body Membranes
 Lanugo = downy type of hair that covers
infants during 5th and 6th months of fetal
development, usually shed by birth
 Vernix caseosa = white, cheesy-looking
substance, produced by sebaceous glands,
protects baby’s skin while it is floating in
water-filled sac inside mother
 Milia = small white spots on baby caused
by accumulations in the sebaceous glands,
normally disappear by third week after
birth
Developmental Aspects of Skin and
Body Membranes
 In adolescence, the skin and hair become more oily as
sebaceous glands are activated  acne. This usually
subsides by adulthood
 Skin begins to visibly change around the 30s as it is
constantly exposed to abrasion, chemicals, wind, sun,
pollutants, bacteria, etc. causing pores to clog and skin
to be irritated  pimples, scales, dermatitis
Developmental Aspects of Skin and
Body Membranes
 Aging  subcutaneous tissue decreases,
skin becomes drier, collagen and elastic
fibers decrease, skin gets thinner
 Hair loses its luster, by age 50 the
number of hair follicles has dropped by
1/3, resulting in hair thinning or baldness
 Male pattern baldness – hair follicles
have become colorless and tiny
 Greying hair = usually genetically
controlled, amount of melanin deposited
decreases or becomes entirely absent,
can be caused by stressful events,
protein-deficient diets, chemotherapy,
etc.
 http://www.youtube.com/watch?v=lLgagxUKWaA&fe
ature=related
 http://www.youtube.com/watch?v=NRAYccnyfkY&fea
ture=related
 http://www.iteachbio.com/Anatomy-Physiology/anatphys.html