Transcript Chapter 4 Skin and Body Membranes

Chapter 4 Skin and Body
Membranes
Biology 110
Tri-County Technical
College
Pendleton, SC
Membranes and more…
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Body membranes cover surfaces, line
body cavities, & form protecting (often
lubricating) sheets around organs fall
into TWO major groups
EPITHELIAL membranes include the
CUTANEOUS, MUCOUS, and SEROUS
membranes
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All contain epithelial sheet always combined
with underlying connective tissue
These membranes are actually simple
organs
Membranes, cont.
CONNECTIVE tissue membranes
represented by SYNOVIAL
membranes
 Two major categories of body
membranes, EPITHELIAL and
CONNECTIVE are classified in part
according to their tissue makeup
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Cutaneous Membranes
Cutaneous membrane is the SKIN
 Its superficial EPIDERMIS
composed of keratinizing stratified
squamous epithelium
 Underlying DERMIS is mostly
dense (fibrous) connective tissue
 Unlike other epithelial membranes,
CUTANEOUS membrane is exposed
to air and is a DRY MEMBRANE
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Mucous Membranes
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Mucous membrane (mucosa) composed
of epithelium resting on loose
connective tissue membrane called
LAMINA PROPRIA
Lines ALL body cavities open to the
exterior
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Hollow organs of respiratory, digestive,
urinary, and reproductive tracts
Stratified squamous (mouth and
esophagus) or Simple columnar (rest of
digestive tract)
Mucous Membranes, cont.
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“WET” or moist membranes
continually bathed in secretions
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Urinary mucosa bathed with urine
Mucosa epithelium adapted for
ABSORPTION/SECRETION
 Mucosa of respiratory/digestive
tracts secrete large amounts of
protective, lubricating mucus
 Urinary tract DOES NOT secrete
mucus
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Serous Membranes
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Composed of layer of simple squamous
resting on thin layer of areolar
connective tissue
Line ALL body cavities closed to exterior
(except for dorsal body cavity and joint
cavities)
SEROUS membranes occur in PAIRS
PARIETAL LAYER lines specific portion of
wall of ventral body cavity then folds
back on itself to form VISCERAL LAYER
which covers outside of organs in cavity
Serous membranes, cont.
In body, serous membranes
separated by thin, clear fluid called
SEROUS FLUID that is secreted by
both membranes
 Allows organs to slide easily across
cavity walls and one another
without friction
 Extremely important when mobile
organs such as pumping heart and
churning stomach are involved
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What’s in a name?
Specific names of serous
membranes depend on their
locations
 PERITONEUM is serous lining
abdominal cavities and covering its
organs
 PLEURA is serosa lining the lungs
 PERICARDIUM is serosa lining
around the heart
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Connective Membranes
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Composed of connective tissue and contain
NO epithelial cells
Line fibrous capsules surround joints
Provide smooth surface and secrete
lubricating fluid called SYNOVIAL FLUID
Also line small sacs of CT called BURSAE
and tubelike TENDON SHEATHS
Both of these cushion organs moving
against each other during muscle activity
(movement of tendon across a bone’s
surface)
Skin and more…
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Skin is major organ of integumentary
system
Insulates, cushions, & protects from
mechanical damage (bumps/cuts),
chemical damage (acids/bases),
thermal damage (heat/cold), UV
radiation (sunlight), and bacteria
Uppermost (outermost) layer full of
KERATIN and CORNIFIED (hardened) to
prevent water loss from body surface
Skin, cont.
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Capillary network and sweat glands play
role in regulating heat loss from body
surface
Acts as mini-excretory system: urea, salts,
and water lost via sweat
Manufactures several proteins important in
immunity and synthesizes vitamin D
CUTANEOUS sensory receptors (NS) located
in skin
Tiny sensors include touch, pressure,
temperature, and pain receptors
Skin Structure
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Skin composed of two kinds of tissue
Outer EPIDERMIS=stratified squamous
capable of keratinizing (becoming
hard/tough)
Underlying DERMIS=dense connective
tissue
Epidermis and dermis firmly connected
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Burn causes separation = blister
Epidermis composed of 5 layers called
STRATA
From inside out: stratum BASALE,
SPINOSUM, GRANULOSUM, LUCIDUM, and
CORNEUM
Skin Structure, cont.
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DERMIS composed of 2 zones or layers
From inside out: RETICULAR LAYER and
DERMAL PAPILLAE
Deep to dermis is the SUBCANTANEOUS
TISSUE (HYPODERMIS) which is essentially
adipose tissue
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NOT considered part of the skin
Serves as shock absorber and insulates deeper
tissues
Responsible for curves that are more a part of a
woman’s anatomy than a man’s
De layer…de layer
STRATUM BASALE is deepest layer of
epidermis
 Lies closest to the DERMIS
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Cells in this layer constantly
undergoing mitosis
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Contains the ONLY epidermal cells that
receive adequate nourishment (diffusion)
of nutrients from dermis
Also called stratum germinativum
Millions of new cells produced DAILY
Stratum Spinosum
Stratum spinosum layer situated above
stratum basale and means “spiny
layer”
 Consists of 8 to 10 layers of cells,
mostly KERATINOCYTES (most
abundant epithelial cells) bound
together by desmosomes
 Begin to become flatter and
increasingly full of keratin
 Cells in this layer continue to divide
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Stratum Granulosum
“Grainy” layer superficial to stratum
spinosum
 3-5 layers of keratinocytes that have
stopped dividing
 Become more flatter and produce
copious amounts of keratin
 Cell membrane thickens, nuclei and
organelles disintegrate
 Cells die and dehydrate creating
tightly interlocked layer of keratin
fibers surrounded by KERATOHYALIN
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Stratum Lucidum
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This layer occurs ONLY where skin
is hairless and extra thick
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Palms of hands and soles of feet
Glassy stratum lucidum (clear
layer) covers stratum granulosum
 Cells in this layer are flattened,
densely packed, and filled with
keratin
 Doomed because NOT able to get
adequate nutrients and oxygen
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Stratum Corneum
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Found at surface of thick and thin skin
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Normally 15-20 layers of keratinized cells
Keratinization (cornification) occurs in
exposed skin surfaces except anterior
surfaces of the eye
OMG, Darling, you are very beautiful…but
Dead cells within each layer remain tightly
interconnected by desmosomes
Shed as large sheets rather than single cells
Layer is water-resistant but not waterproof
Journey from stratum basale to stratum
corneum takes about 15-30 days
Dead cells remain in stratum corneum for
Melanin and the Body
Beautiful
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Melanin is a pigment that ranges from
yellow to brown to black
Produced by special cells called
MELANOCYTES
Melanocytes found primarily in stratum
basale
Skin exposed to sunlight, melanocytes
stimulated to produce more melanin =
tanning
Pigment umbrella
Freckles/moles are seen where melanin
is [ ]ed in one spot
Dermis and beyond
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Dermis is strong, stretchy envelope that
helps hold body together
Dense fibrous connective tissue making up
dermis consists of two major regions
PAPILLARY LAYER is upper dermal region
Uneven with fingerlike projections from its
superior surface called DERMAL PAPILLAE
which indent epidermis above
Many dermal papillae contain capillary loops
which supply nutrients to epidermis
Dermis, cont.
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Other dermal papillae house pain receptors
(free nerve endings) and touch receptors
(Meissner’s corpuscles)
On palms of hand and soles of feet, papillae
arranged in definite pattern that forms
looped and whorled ridges on epidermal
surface that increase friction and enhance
gripping ability of fingers and feet
Ridges of fingertips covered with sweat
pores and leave identifying film of sweat
called FINGERPRINTS on nearly everything
they touch
Dermis, cont.
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RETICULAR LAYER of dermis is deepest skin
layer
Contains blood vessels, sweat and oil glands,
and deep pressure receptors (Pacinian
corpuscles)
Many phagocytes found in reticular layer
Both collagen and elastic fibers found with
layer
Collagen = toughness of dermis but also
attracts and binds water
Elastic = skin elasticity during youth
Aging decreases # of collagen and elastic
fibers, skin begins to sag and wrinkle…tell
Sidebar on Skin Colors
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Three pigments contribute to skin color
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Melanin, carotene, and hemoglobin
Amount and kind of melanin (yellow, reddish
brown, or black) in the epidermis (basale)
 Amount of carotene deposited in stratum
corneum and subcutaneous tissue (yelloworange pigment)
 Amount of oxygen bound to hemoglobin
(pigment in RBCs) in dermal blood vessels
Example: lots of melanin = brown skin tone
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Skin Colors, cont.
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Light skinned people, crimson color of
oxygen-rich hemoglobin in dermal blood
supply shows through = “rosy glow”
Large amounts of carotene-rich food
consumed, skin takes on yellow-orange cast
CYANOSIS-occurs when hemoglobin is
poorly oxygenated and blood/skin of
Caucasians appear BLUE
ERYTHEMA (redness)-name given reddened
skin and may indicate embarrassment,
fever, hypertension, inflammation, or
allergy
Skin Colors, cont.
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PALLOR (blanching)-certain types of
emotional stress (fear, anger, & others)
cause some people to become PALE
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JAUNDICE (yellow cast)-name given
abnormal yellow skin tone; usually signifies
liver disorder
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Pale skin may also signify anemia, low blood
pressure, or impaired blood flow to area
Excess bile pigments absorbed into blood and
deposited in body tissues
Bruises/Black and blue marks-reveal sites
where blood has escaped from circulation
and clotted in tissue spaces
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Such clotted masses called HEMATOMAS
Unusual tendency to bruise may be indicate
deficiency of vitamin C or hemophilia
Skin Appendages
Skin appendages are cutaneous
glands, hair and hair follicles, and nails
 Each arises from epidermis and plays
unique role in maintaining
homeostasis
 CUTANEOUS GLANDS
 Are all EXOCRINE glands that release
their secretions to skin surface via
DUCTS
 Are two groups of cutaneous glands:
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Sebaceous glands and sweat glands
Sebaceous glands
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These “oil glands” are found all over body
except on palms of hands and soles of feet
Ducts usually open into hair follicles but
some open onto skin surface
SEBUM is lubricant that keeps skin soft and
moist and prevents hair from becoming
brittle
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Also contains chemicals that kill bacteria
Sebaceous glands become very active when
male sex hormones produced in > amounts
(in both sexes) during adolescence
Sebaceous glands, cont.
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Skin becomes oilier during this period of life
Sebaceous gland’s duct becomes clogged =
whitehead
Accumulated material oxidizes and dries =
blackhead
ACNE is active infection of sebaceous glands
accompanied by “pimples” on skin
SEBORRHEA (cradle cap) in infants caused
by overactivity of sebaceous glands
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Scalp turns pink, raised lesions gradually form
yellow to brown crust that sloughs off as oily
dandrull
Sweat of one’s brow…
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Two types of sweat glands: eccrine and
apocrine
ECCRINE sweat glands most numerous and
are found all over the body
Produce SWEAT-clear secretion that is
primarily water plus some salts (sodium
chloride), vitamin C, traces of metabolic
wastes (ammonia, urea, & uric acid), and
lactic acid (attracts mosquitoes)
Sweat is usually acidic (pH 4-6) helping
inhibit growth of bacteria
Eccrine Sweat glands,
cont.
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Typically sweat reaches skin via duct
opening externally as funnel-shaped pore
Eccrine glands play important part of body’s
heat regulating equipment
Supplied with nerve endings that cause
them to “sweat” when external temp or
body temp is high
As sweat evaporates, carries large amounts
of body heat with it
Can lose 7 liters of body water a day in very
hot temps
Heat regulating functions important to
maintaining life
Apocrine Glands
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Apocrine glands largely confined to axillary
and genital areas of body
Usually > than eccrine glands and their ducts
empty into hair follicles
Secretions contain fatty acids and proteins
as well as “stuff” in eccrine gland secretion
Secretion is “odorless” but bacterial growth
may impart musky, unpleasant odor
Begin to function at puberty (androgens)
Play minimal role in thermoregulation
Activated by nerve fibers during pain, stress,
and/or sexual foreplay/activity
Neither “hair” nor there
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HAIR is produced by a root follicle and is
flexible epithelial structure
HAIR ROOT is part of hair enclosed in follicle
HAIR SHAFT is part projecting from surface
of skin or scalp
Hair formed by division of well-nourished
cells in stratum basale epithelial cells in
growth zone (hair bulb matrix)
Bulk of hair shaft, like bulk of epidermis, is
dead material
Goose bumps…or whatever
Small bands of smooth muscle cells
called ARRECTOR PILI connect each
side of hair follicle to dermal tissue
 When these muscles contract (cold,
frightened, …not going there), hair
is pulled upright
 Dimples skin surface with “goose
bumps”
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If I had a hammer…
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NAIL is scalelike modification of epidermis
similar to hoof/claw of other animals
EACH nail has FREE EDGE, BODY (visible,
attached portion), and ROOT (embedded in
the skin)
Borders of nail over overlapped by skin folds
called nail folds
Thick, proximal nail fold is called the
CUTICLE
STRATUM BASALE of epidermis extends
beneath nail as the NAIL BED
Nails, cont.
Nail’s thickened proximal area that
is responsible for nail growth is
called the NAIL MATRIX
 LUNULA is white crescent over the
thickened nail matrix
 Nails, like hair and the stratum
corneum cells, are mostly nonliving
material
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Infectious Disorders of the
Skin
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TINEA PEDIS (athlete’s foot)-itchy, red
peeling condition of skin between toes from
fungus infection
BOILS-inflammation of hair follicles and
sebaceous glands, common on dorsal neck
CARBUNCLES-composite boils typically
caused by bacterial infections
(Staphylococcus aureus)
COLD SORES-small fluid-filled blisters that
itch/sting caused by herpes simplex virus
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Localizes in cutaneous nerve where dormant until
activated by emotional upset, fever, or UV
radiation
Skin disorders, cont.
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CONTACT DERMATITIS-itching, redness and
swelling of skin, progressing to blisters
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Caused by exposure of skin to chemicals (poison
ivy, etc.) that promote allergic responses in
sensitive individuals
IMPETIGO-pink, water-filled lesions (around
mouth/nose) that develop yellow crust and
rupture
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Caused by highly contagious staphylococcus
infection
Common in elementary school children
Skin Disorders, cont.
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PSORIASIS-chronic condition
characterized by reddened epidermal
lesions covered with dry, silvery scales
If severe, may be disfiguring
Cause unknown, but heredity seems to be
implicated
Attacks often triggered by trauma,
infection, hormonal changes, and stress
Three Types of Burns
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BURN is tissue damage and cell death
caused by intense heat, electricity, UV
radiation, or certain chemicals
Burns are classified according to their
severity
FIRST-DEGREE-only epidermis is damaged
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Area becomes red and swollen
Temporary discomfort but “usually” NOT serious
Heal in 2-3 days without any special attention
Sunburn is “usually” a first-degree burn
Burns, cont.
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SECOND DEGREE-involve injury to
epidermis and upper region of dermis
Skin red/painful and BLISTERS appear
 Sufficient numbers of epithelial cells still
present, regrowth (regeneration) of
epithelium can occur
 Normally, no permanent scarring results
IF infection prevented
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First- and Second-degree burns
referred to as PARTIAL-THICKNESS
BURNS
Burns, cont.
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THIRD-DEGREE-destroy entire thickness of
skin and are called full-thickness burns
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Burned areas appear blanched (gray-white) or
blackened
Nerve endings in area destroyed so burn area
NOT painful
NO regeneration is possible so skin grafting
required to cover underlying exposed tissues
Considered CRITICAL if over 25% of body
has second-degree burns or if over 10% of
body has third-degree burns OR if there are
third-degree burns of face, hands, or feet
Rule of Nines
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Burns result in two life-threatening
problems
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Body loses supply of fluids containing proteins
and electrolytes as they seep from burned
surface
This dehydration/loss of electrolytes can lead to
shut down of kidneys and CIRCULATORY SHOCK
(inadequate circulation of blood due to low blood
volume)
Volume of fluid loss can be estimated
indirectly by determining how much of
surface has been burned using the RULE OF
NINE
Rule of Nine, cont.
Method divides body into 11 areas
each accounting for 9 percent of
total body surface
 Additonal area surrounding genitals
(perineum) = 1 percent
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Types of Skin Cancers
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Skin cancer most common cancer in
humans
BASAL CELL CARCINOMA-least malignant
and most common skin cancer
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Cells of stratum basale, altered so can no
longer form keratin, no longer honor boundary
between epidermis and dermis
Proliferate & invade dermis and subcutaneous
tissue
Occur most often on face as shiny, dome
shaped nodules that later develop central ulcer
with “pearly” beaded edge
Skin Cancers, cont.
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Slow-growing and seldom metastasizes
before discovery
Cure rate is 99% (surgical removal)
SQUAMOUS CELL CARCINOMA-arises from
cells of stratum spinosum
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Lesion is scaly, reddened papule (small, rounded
elevation) that gradually forms shallow ulcer
with firm, raised border
Appears on scalp, ears, dorsum of hands, lower
lip
Metastasizes rapidly to lymph nodes if not
removed
Believed to be ‘sun-induced” but recovery rate
Skin cancers, cont.
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MALIGNANT MELANONA-is cancer of
melanocytes
Accounts for 5% of skin cancers, rate is
rising, and CAN be deadly
Can begin anywhere there is pigment
(some begin at pigmented mole)
Usually appear as spreading brown/black
patch that metastasizes rapidly to lymph
nodes and blood vessels
Survival rate is about 50%
The ABCD Rule for
Melanomas
A (asymmetry)-two sides of pigment
spot or mole do NOT match
 B (border irregularity)-borders of
lesion are not smooth but exhibit
indentations
 C (color)-pigmented spot contains
areas of different colors (blacks,
browns, tans, and sometimes blue
and reds)
 D (diameter)-spot is larger than 6 mm
in diameter (size of pencil eraser)
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