Chapter 4 - Skin and Body Membranes
I. Classification of Body Membranes
A. Epithelial Membranes- epithelial with a
layer of connective tissue underneath
1. Cutaneous Membrane- skin- surface is
keratinizing stratified Squamous and
the dermis is dense fibrous connective
tissue- it is a dry membrane
2. Mucous Membranes- line body cavities
that open to outside of body, usually
contain stratified squamous or simple
columnar, always moist, may be
adapted for absorption or secretion
3. Serous Membranes – line closed body
cavities, in pairs, made of simple
squamous on thin layer of areolar
connective tissue, layers may be
separated by clear serous fluid (no
friction)
*peritoneum- lines abdominal cavities
*pleura- surrounds lungs
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*pericardium- surrounds heart
B. Connective Tissue Membranes- synovial
membranes that contain no epithelial
cells, line capsules at joints to provide
smooth surface and lubricating fluid
II. Integumentary System (Skin)
A. Basic Skin Functions- see p. 99
1. protection
2. temperature control
3. excretion
4. vitamin D synthesis
B. Structure of the Skin
* the layers are usually well connected unless
separated by friction or burn- blister!
1. Epidermis- outer layer that can
harden (keratinize), made of 5 layers
(strata) that are avascular
a. keratin is fibrous protein produced
by keratinocytes- makes cells
water-repellent
b. stratum basale- deepest layer that
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is always going thru mitosis
c. new cells push up to form stratum
spinosum, then stratum granulosum
d. cells get flatter & contain more
keratin to form stratum lucidum, in
areas where skin is very thick and
hairless
e. outer layer is stratum corneum- 2030 cell layers thick, constantly
flaking off
f. melanin pigment is produced by
melanocytes in basale, protects
DNA from UV radiation
g. homeostatic imbalance- too much
sun damages skin & depresses
immune system, can change DNA in
skin cells (skin cancer)
Question: Water in a swimming pool is hypotonic
to human cells and body fluids. So why don’t we
swell up and burst open while swimming?
2. Dermis- dense connective tissue with
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subcutaneous tissue below (hypodermis)
a. papillary layer- upper region that is
uneven and has projections called
dermal papillae that house pain
receptors, Meissner’s corpuscles
(touch), and form fingerprints
b. reticular layer- deepest layer of
skin, contains blood vessels, sweat &
oil glands, pressure receptors
(Pacinian corpuscles), and
phagocytes to prevent infection
c. collagen and elastic fibers in dermis
decrease as you get older 
d. blood vessels in dermis help control
body temperature- can constrict to
conserve heat or dilate to release
excess heat
e. homeostatic imbalance- restriction
in blood supply to skin causes skin
cells to die, can cause ulcersdecubitus ulcers (bed sores) result
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from pressure that restricts blood
flow
C. Skin Color- 3 main pigments
1. amount and kind of melanin- yellow,
reddish brown, black in epidermis
2. amount of carotene in stratum
corneum and subcutaneous tissueorange-yellow pigment especially
abundant in carrots, deep yellow,
orange, leafy green veggies
3. amount of O2 bound to hemoglobin in
RBC in dermal blood vessels
Question: A 13 month old baby is brought to the
doctor’s office because his skin has turned
orange. Why did the doctor ask about the baby’s
diet?
4. homeostatic imbalancea. poorly oxygenated blood can cause
lighter skinned people to appear blue
(cyanosis),
may be due to circulatory/
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respiratory problems. Darker
skinned people do not appear blue
except in mucous membrane and nail
beds
b. erythema- redness- embarrassment,
fever, hypertension, allergy,
inflammation
c. pallor (paleness)- emotional stress,
low BP, anemia, impaired blood flow
d. jaundice (yellowish)- liver disorder
e. bruises, black & blue markshemotomas, where blood has clotted
in tissues, vitamin C deficiency,
hemophila
Question: After taking a patient’s history, the
nurse notes that the patient is cyanotic. What is
cyanosis and what can it indicate?
D. Appendages of the Skin
1. Cutaneous Glands- exocrine glands
a. Sebaceous (Oil) Glands- found
everywhere in varying amounts
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except palms of hands and soles of
feet
b. Sweat Glands (sudoriferous glands)
(1) over 2.5 million per person
(2) eccrine glands- produce sweatmostly water plus salts and lactic
acid- acidity inhibits growth of
bacteria, open to surface thru
pores, have nerve endings that
make them secrete sweat when
external or internal temp is high
(up to 7 liters/day)
(3) apocrine sweat glands- mostly
around axillary & genital areas,
ducts empty in hair follicles,
sweat contains fatty acids &
proteins that bacteria use,
causing odor- usually do not
function until puberty
2. Hairs and Hair Follicles
a. hair is produced by hair follicle
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b. part of hair enclosed by follicle is
root
c. hair shaft projects from surface of
skin & is formed by hair bulb matrix
in stratum basale
d. each hair has core called medulla
surrounded by layer called cortex,
which is covered by cuticle
e. hair follicle is made of epithelial
tissue and connective tissue
f. smooth muscle cells- arrector piliconnect to each side of follicle
3. Nails- scale-like modification of
epidermis
a. stratum basale forms nail bed
beneath nail
b. nail matrix is thickened area of
basale responsible for nail growth
c. pink except for white crescent
called lunula
E. Homeostatic Imbalances of the Skin
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1. Infections and Allergies
a. Athlete's Foot- fungal infection
b. Boils and Carbunclesinfection/inflammation of hair
follicles & sebaceous glands, often
caused by Staph
c. Cold Sores- caused by herpes
simplex virus, may be present but
stays dormant until activated
d. Contact Dermatitis- catch-all for
itching and redness, usually caused
by chemicals
e. Impetigo- very contagious Staph
infection, causes little pinks lesions
that break open & form yellow crust
f. Psoriasis- chronic, may be
disfiguring, reddened lesions with
dry silvery scales, idiopathic
2. Burns- tissue damage and death of
cells caused by heat, electricity,
radiation, or chemicals
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a. can result in life-threatening
problems- loss of proteins and
electrolytes, dehydration, kidneys
shut down, shock, later infection
b. estimate amount of fluid loss by
using rule of nines (see p. 108)- each
body area has about 9% of total
body surface
c. types of burns
(1) 1st degree- epidermis is damaged,
red, swollen, discomfort
(2) 2nd degree- epidermis and upper
dermis are damaged, skin is red,
blistered, painful- critical if they
cover over 25% of body
(3) 3rd degree- entire thickness of
skin is destroyed, may be white
or blackened, nerve endings are
damaged so may not be painful,
can’t regenerate- critical if they
cover over 10% of body or if they
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are on face, hands, feet
3. Skin Cancer
a. Basal Cell Carcinoma- stratum
basale, most common, least
malignant, slow-growing, 99% cure
rate if removed
b. Squamous Cell Carcinoma- stratum
spinosum- red, scaly, shallow ulcer,
grows rapidly and metastasizes if
not removed
c. Malignant Melanoma- cancer of
melanocytes, may develop from
pigmented moles, metastasizes
rapidly, 50% chance of survival with
early detection
KNOW YOUR ABCDs!
A- asymmetry- two sides are uneven, don’t
match
B- borders are irregular, not smooth
C- area contains more than 1 color- black,
brown, blue, tan, red
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D- diameter is larger than 6 mm- pencil eraser
Question: Mr. Bozo, late 60s, fisherman, has
small ulcers on both forearms, ears, and face.
They have been present for several years. What
is the likely diagnosis and cause?
Question: A 35 year old life guard complains
that his face is getting wrinkled and that he has
several darkly pigmented moles that are the size
of a dime. You think “ABCD”. What does that
mean and why should he be concerned?
III. Developmental Aspects of Skin and
Body Membranes
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