Human Body
Chapter 4
Skin and Body Membranes
Classification of Body Membranes
• Membranes cover surfaces, line body cavities,
and forms protective sheets around organs
Two Major Groups
1. Epithelial Tissue Membranes- include
cutaneous, mucous, and serous membranes
2. Connective Tissue Membranes- include
synovial membranes
Epithelial Membranes
• These membranes contain and epithelial
sheet with an underlying layer of connective
tissue.
• These membranes are actually simple organs.
Cutaneous Membranes
• This is your skin!
• The upper layer is keratinizing stratified
squamous epithelium.
• The lower layer is dense fibrous connective
tissue.
• The membrane is exposed to air and is a dry
membrane
Cutaneous Membrane
Mucous Membranes
• Composed of various types of epithelium
resting on loose connective tissue called
lamina propria.
• This membrane type lines all body cavities
that open to the exterior, such as those hollow
organs of the respiratory, digestive, urinary,
and reproductive tract.
Mucous Membranes
• Wet, moist that are almost continuously
bathed in secretions or in the case of urine
mucosae, urine.
• Function: absorption and secretion with the
exception of mucosae of the respiratory and
digestive system that secretes large amounts
of protective, lubricating mucus.
Mucous Membranes
Serous Membranes
• Composed of simple squamous epithelium
resting on a thin layer of areolar connective
tissue.
• Lines cavities that are closed to the exterior.
• Occur in pairs:
• Parietal Layer-lines a specific portion of the ventral
cavity
• Visceral Layer- covers the outside of the organs
Serous Membranes
• The layers are separated by a thin layer of
fluid called serous fluid.
• The serous fluid allows the organs to slide
against each other and the walls without
friction.
• The name of specific serous membranes
depends in location
Serous membranes
• Peritoneum:
• Pleura:
• Pericardium:
Connective Tissue Membranes
• Synovial Membranes
– Composed of connective tissue and no epithelial
tissue
– Line the fibrous capsules surrounding joints
– Provide a smooth surface and secrete a lubricating
fluid
– Line small sacs of connective tissue called bursae
and the tube-like tendon sheaths
– Cushion organs moving against each other
Integumentary System (Skin)
• Cutaneous membrane
• Skin, Sweat Glands, Oil Glands, Hair, and Nails
• Function is mostly protective
Basic Skin Functions
• Protects:
– entire body from mechanical damage (bumps and
cuts)
– chemical damage (acids and bases)
– Thermal damage (hot and cold)
– Ultraviolet radiation
– Bacteria
** also insulates and cushions deeper body
organs**
Basic Skin Functions
• Outer layer is hardened to prevent water loss.
• Capillaries and Sweat Glands regulate heat
loss.
• Mini excretory system ( urea, salts, and H20)
• Manufactures several proteins for immunity
and Vitamin D synthesis.
• Sensory Receptors ( pain, pressure,
temperature, and touch)
Structure of the Skin
• Composed of two kinds of tissue:
1) The Epidermis- composed of stratified squamous
epithelium that is capable of keratinizing.
2) The Dermis- made up of dense connective tissue
**The epidermis and dermis are firmly connected**
**A burn or friction can cause them to separate
causing a blister**
Structure of the Skin
• Hypodermis:
– located deep to the dermis
– Essentially Adipose Tissue
– Anchors the skin to underlying organs
– Shock absorber and insulator
– Responsible for curves (female)
Epidermis
• Composed of 5 zones or layers called strata
1. Stratum Basale
2. Spinosum
3. Granulosum
4. Lucidum
5. Corneum
**Epidermis is avascular**
**most cells are keratinocytes**
Melanin
• A pigment that ranges from yellow to brown
to black-produced by melanocytes
• Found in stratum basale
• When skin is exposed to sunlight it stimulates
the melanocytes to produce more melanin
pigment=tanning.
• Freckles and moles are melanin concentrated
in one spot.
Melanin
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•
•
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Excessive UV exposure can damage the skin
Elastic fibers clump causing leathery skin.
Depresses the immune system
Can alter the DNA of skin cells leading to skin
cancer
• Melanin can act like a natural sunscreen
Dermis
• “Hide” strong, stretchy, envelope that helps
hold the body together.
• Two major regions:
1. Papillary Region
2. Reticular Region
Skin Color
• Three pigments contribute to skin color:
– The amount and kind
– The amount of carotene deposited in the stratum
corneum and subcutaneous layer
– The amount of O2 bound to the hemoglobin in
the dermal blood vessel
Skin Color
• Carotene- orange-yellow pigment found in
abundant amounts in carrots
• People who produce a lot of melanin have
darker colored skin
• Crimson color of O2-rich hemoglobin flushes
through the transparent layer to give rosy
color
Skin Color
• Skin takes on a yellow-orange cast when large
amounts of carotene are eaten
• Cyanosis-turning blue from a lack of O2
• In black people skin does not appear cyanoticmasked by melanin-nail beds and mucous
membranes
Skin Color
• Redness or Erythema
– Embarrassment, fever, hypertension,
inflammation or allergy
Skin Color
• Pallor or Blanching
– Emotional stress, anemia, low blood pressure,
impaired blood flow to an area
Skin Color
• Jaundice or Yellow Cast
– Liver disorder-excess bile pigments are absorbed
in the blood, circulated through the body and
deposited in body tissues
Skin Color
• Bruises or Black and Blue Marks
– Reveal sites where blood has escaped circulation
and has clotted in tissue spaces
– Hematomas
– Vitamin C deficiency or Hemophilia
Appendages of the Skin
• Arise from the epidermis
• Play a role in maintaining homeostasis
• Include Cutaneous glands, Hairs, Hair follicles,
and Nails
Cutaneous Glands
• Exocrine glands that release their secretions
to the skin surface via ducts.
Two Types
1. Sebaceous Glands
2. Sweat Glands
* Located in the dermis, deep tissue layer
Sebaceous Gland
• Oil Glands
• Found all over the skin except the palms of
hands and soles of feet.
• The ducts usually deposit into the hair follicle
but some will empty on the surface of the skin
• Sebum(grease)-mixture of oily substances and
fragmented cells
Sebaceous Glands
• Sebum:
– Keeps skin soft and moist
– Prevents hair from becoming too brittle
– Contains chemicals that kill bacteria, prevents the
bacteria on skin from invading deeper tissue layers
– Become very active when make sex hormones are
produced(adolescence)
Sebaceous Glands
• If gland’s duct gets blocked by sebum
“whitehead” occurs. If material oxidizes, it
forms a “blackhead”
• Acne=active infection of the sebaceous gland.
• Seborrhea=cradle cap in infants is caused by
over activity of the sebaceous glands
Sweat Glands
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•
•
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Also called Sudoriferous Glands
Widely distributed throughout the skin
2.5 million per person
Two types: eccrine and apocrine
Eccrine Glands
• Numerous and found all over the body
• Produce Sweat(clear mostly H2O, salts,
vitamin C, trace amounts of metabolic wastes,
lactic acid)
• Sweat is acidic-prevents bacteria growth
• Sweat reaches skin’s surface through pores.
Eccrine Glands
• Highly efficient part of body’s heat regulating
equipment.
• Supplied with nerve endings that are sensitive
to external temps.
• Hot day possible to lose up to 7 liters of body
H2O
Apocrine Sweat Glands
• Confined to axillary and genital areas
• Larger than eccrine glands and their ducts
empty into hair follicles.
• Secretions contain fatty acids and proteins as
well as those secreted by the eccrine glands
• Secretions take on a milky or yellowish color.
• Bacteria that live on the skin will use the
proteins and fatty acids causing smell.
Apocrine Glands
• Begin to function around puberty under the
influence of androgens.
• Minimal role in thermoregulation.
• Activated by nerve fibers during pain, stress,
and sexual foreplay
Hairs and Hair Follicles
• Millions of hairs scattered all over the body.
• Serve several functions: guarding head against
bumps, shielding the eyes, preventing foreign
particles from getting into the respiratory
tract.
• Lost ancient function
Hair
• See pictures on pg. 100
• Come in a variety of sizes and shapes
• The shape of the hair shaft will determine the
look of the hair
• Arrector pili muscle
Nails
• Scale-like modification of the epidermis that
corresponds to the hoof or claw in other
animals
• Consists of: Free edge, body, root, nail folds,
nail bed, nail matrix
• Transparent or nearly colorless but look pink
because of the oxygen rich blood supply under
the dermis.
Homeostatic Imbalances of the Skin
• Loss of homeostasis in the body cells and
organs can reveal itself in the skin
• The skin can develop more than 1000 different
types of aliments.
• The most common types of skin disorders
result from allergies, bacterial, viral, or fungal
infections.
Infections and Allergies
• Athlete’s Foot-Itchy, red, peeling condition
between the toes of the feet. Fungal infection
Infections and Allergies
• Boils and Carbuncles- Inflammation of the hair
follicles and sebaceous glands, common on
dorsal neck
• Carbuncles are composite boils caused by
Staphylococcus Aureus- Staph Infection
Infections and Allergies
• Cold Sores- small fluid filled blisters that sting
and itch.
• Caused by Herpes Simplex Infection
• Virus localizes in cutaneous nerve where it will
remain dormant until emotional upset, fever,
UV radiation
Infections and allergies
• Contact Dermatitis- Itching, redness, swelling
of the skin, progressing to blistering
• Caused by exposure to chemicals that provoke
allergic reactions (poison ivy)
Infections and Allergies
• Impetigo-pink, water-filled raised lesions that
develop a yellow crust and eventually rupture
• Highly contagious staphylococcus infection
• Common in elementary school children
Infections and Allergies
• Psoriasis- Chronic condition characterized by
reddened epidermal lesions covered by dry,
silvery scales.
• Severe cases can be disfiguring
• Cause is unknown-hereditary, triggered by
trauma, infection, hormonal changes, and
stress
Burns
• Skin is about as thick as a sheet of paper towel
• When severely damaged it affects all other
systems in the body.
• Burn=tissue damage and cell death caused by
intense heat, electricity, UV radiation, or
certain chemicals
Burns
• There are few threats to skin more serious
then burns.
• Two life threatening events:
– Body loses precious supply of fluids containing
proteins and electrolytes as they seep from
burned surfaces.
– Dehydration and electrolyte imbalance follow
leading to kidney failure and circulatory shock
Burns
• In order to save a patient the lost fluids must
be replaced.
• Apply the Rule of Nines:
• Divides body into 11 areas each accounting for 9% of
the total body surface plus additional area surrounding
the genitals representing 1% of body surface
Burns
• Later infection becomes most important
threat and is leading cause of death.
• Burned skin is sterile for 24hrs after that
pathogens like bacteria and fungi invade area.
• Immune system becomes depressed within
one to two days.
Burns
• Burns are classified according to their severity.
– First Degree- epidermis is damaged, area becomes
red and swollen, not serious and heal in two to
three days. (sunburn)
– Second Degree- Injury to the epidermis and
upper dermis, skin is red and painful, blisters
appear, regeneration can occur, ordinarily no
permanent scars result
– * referred to as Partial-Thickness Burns
Burns
– Third- Degree Burns-destroys the entire thickness
of the skin=full thickness burns
– Burned area appears blanched or blackened,
nerve endings are destroyed so it is not painful,
regeneration is not possible.
Critical Burns
• Burns are considered critical when:
– Over 25% of the body has 2nd degree burns
– Over 10% of the body has 3rd degree burns
– 3rd degree burns on the face, hands, or feet
Skin Cancer
• Skin cancer is the single most common type of
cancer in humans
• Most important risk factor is over-exposure to
UV radiation in sunlight
• Frequent irritation of the skin by infections,
chemicals, or physical traumas also seem to
be predisposing factors
Skin Cancer
• http://video.about.com/dermatology/SkinCancer.htm
Skin Cancer
• Basal Cell Carcinoma
– Least malignant and most common
– Cells are altered so that they can not form keratin
no longer honor the boundary between epidermis
and dermis.
– Occur on sun exposed areas
– Full cure is the rule 99%percent of cases where
lesion is removed surgically.
Skin Cancer
• Squamous Cell Carcinoma
– Appears as a scaly, reddened elevation that
gradually forms a shallow ulcer with a firm raised
border.
– Scalp, ears, hands, and lower lip
– Grows rapidly and metastasizes to adjacent lymph
nodes if not removed
– Sun-induced cure is good when removed surgically
or by radiation therapy
Skin Cancer
• Malignant Melanoma
– Cancer of melanocytes
– 5% of skin cancer but incidence is rising and is
often deadly
– Can begin wherever there is pigment-appears as a
spreading brown to black patch that metastasizes
quickly to surrounding lymph and blood vessels
– Survival=50% early detection is important
Skin Cancer
• Sun worshippers should examine skin for new
moles or pigmented spots and apply ABCD
rule.
A=Symmetry-two sides of the pigmented spot or
mole do not match
B=Border Irregularity-the borders of the lesion
are not smooth but exhibit indentations
Skin Cancer
C=Color-the pigmented spot contains areas of
different colors (blacks, browns, tans, and
sometimes blues and reds
D=Diameter-the spot is larger than 6mm in
diameter (the size of a pencil eraser)
Developmental Aspects of Skin and
Body Membranes
• During the 5th and 6th months of fetal
development the fetus is covered in Lanugo
• Vernix Caseosa- white, cheesy-looking
substance produced by the sebaceous glands.
Protects the babies skin while it is in the
amniotic fluid
• Milia-white spots that appear on the baby’s
nose and forehead
Development cont.
• During adolescence skin and hair become
more oily
• Skin reaches its peak in our 20s and 30s then
changes occur as it is assaulted by abrasion,
chemicals, wind, sun and other irritants and as
pores become blocked with air pollutants and
bacteria
Development cont.
• During old age subcutaneous tissue decreases
leading to an intolerance to cold
• Skin gets drier can become itchy and
bothersome
• Thinning of the skin cause bruising
• Decreasing elasticity causes sagging skin-sped
up by sunlight
Development cont.
• Hair-loses luster as we age
• # of hair follicles reduced by 1/3 by 50 and
continues to decline
• Graying hair results from a decrease or
absence of the melanin deposited in the hair.