Transcript Integumentary System

Integumentary System
Body Membranes
• Body membranes cover surfaces, line body
cavities, and form protective sheets over organs
• Two major groups:
– Epithelial membranes – cutaneous (skin), mucous,
and serous membranes
– Connective tissue membranes – synovial
membranes
Epithelial Membranes
• Epithelial membranes – covering and lining
membranes
• Contain an epithelial sheet, but it is always
combined with a connective tissue layer
• 2 tissues = These membranes are actually
simple organs
Cutaneous Membrane = Skin
• Its superficial epidermis is
composed of keratinizing
stratified squamous
epithelium.
• Underlying dermis is
mostly dense (fibrous)
connective tissue.
• Exposed to air = dry
membrane
Mucous Membrane = Mucosa
Varied types
Stratified squamous epithelium in mouth,
esophagus
Simple columnar epithelium in digestive
tract
• Composed of
epithelium resting on
loose connective
tissue called lamina
propria.
• Lines all body cavities
that open to exterior
• Wet membranes
bathed in secretions
or urine
• Adapted for
absorption or
secretion
Serous membrane = serosa
• Simple squamous
epithelium resting on
areolar connective tissue
• Line body cavities that
are closed to exterior
• Occur in pairs:
– Parietal layer lines the
wall of the ventral cavity
– Visceral layer covers the
outside of those organs
• Layers separated by
serous fluid, which allows
organs to slide without
friction (heart, stomach)
Serosa
• Serosa lining the abdominal cavity and
covering its organs = peritoneum
• Membrane surrounding lungs = pleura
• Membrane around the heart = pericardium
Synovial Membranes
• Composed of soft areolar
connective tissue and
contain no epithelial cells.
• Line the fibrous capsules
surrounding joints and
tendon sheaths
• Secrete lubricating fluid to
cushion organs during
muscle activity
Tattoos
• Tattoos are made
by using a needle
to deposit
pigment in the
dermis.
• Risk of Hepatitis C
is about 15x
higher in people
who have
tattoos…
Cutaneous Membrane = Skin
• Skin and its glands (sweat, oil), along with hair
and nails, make up the integumentary system
• Integument (covering):
– keeps water and other molecules in the body
– Insulates and cushions body organs
– Protects body from mechanical (bumps), chemical
(acids and bases), thermal (heat and cold), UV (solar
radiation), and bacteria damage.
• Uppermost layer of skin is full of keratin and is
cornified (hardened) to help prevent H2O loss.
Capillary Network in Skin
• Capillary network and sweat glands
regulate heat loss
• Urea, salts, and water are lost as
sweat
• Manufactures proteins important to
immunity and synthesizes Vitamin D
(sunlight converts cholesterol in skin
into vitamin D).
• Cutaneous sensory receptors are
located in skin – sense pain,
pressure, temperature, touch
Skin Structure
• Tissues in skin:
• Epidermis – stratified squamous epithelium,
keratinizing (can become hard)
• Dermis – dense connective tissue
• Subcutaneous layer (hypodermis) – below
dermis, adipose tissue, anchors skin to organs.
Skin Structure
• Subcutaneous layer
– shock absorber
and insulation from
extreme T changes
• Thicker in women
than in men
(adipose tissue)
Epidermis
• Five layers / strata:
– Stratum Corneum
– Stratum Lucidum
– Stratum Granulosum
– Stratum Spinosum
– Stratum Basale
• Epidermis is avascular (no blood supply)
– Ex: shaving is cutting off cells w/ no blood (usually)
Stratum Basale
• Most cells of epidermis are keratinocytes
(keratin cells) which produce keratin
• Keratin –protein that makes epidermis tough
• Deepest layer of epidermis / closest to dermis
• Daughter cells pushed upward into superficial
layers
Epidermis
• Stratum basale
constantly
undergoing mitosis,
a.k.a. stratum
geminativum
• New cells become
increasingly flatter
and full of keratin
• Stratum Spinosum –
cuboidal cells
• Stratum granulosum
– cells granular
Epidermis
• As new cells die they form the stratum
lucidum
• This layer is only present where skin is hairless
and thick (palms of hands, soles of feet)
• Stratum corneum – ¾ of epidermal thickness
• Cornified or horny (cornu = horny) cells,
completely keratinized
Melanin
• Melanin is a pigment that ranges from yellow to
brown to black
• Produced by melanocytes, found in stratum
basale.
• Everyone has same number of melanocytes
• Complexion determined by quantity of melanin
produced
• Heredity – genes specific for melanin production;
mutant genes can cause lack of melanin
Albinism
• Albinism results when
genetic changes result
in a lack of pigment
(melanin) production
• Can have eye problems
(light scattering, optic
nerve problems)
Dermis = your hide
• Two major regions
– Papillary – upper dermal region
• Dermal papillae (papill=nipple) – house pain receptors,
send nutrients to epidermis, form fingerprints
– Reticular – deepest skin layer
• Contains blood vessels, sweat and oil glands, and
pressure receptors (Pacinian corpuscles)
• Collagen (toughness) and elastic (stretch when
growing) fibers found in dermis
• Many receptors for nervous system
Skin Appendages
• Cutaneous glands –
exocrine. Release secretions
to skin surface via ducts.
– Sebaceous (oil) glands –
often open into hair follicles.
Everywhere but palms and
soles.
• Secrete sebum – oil that keeps
skin soft and kills bacteria.
Increased amount in
adolescence
Acne = infection of sebaceous gland
• When sebaceous
gland’s duct is blocked
by sebum, a whitehead
appears on skin surface
• If the material
accumulates and dries
it darkens to form a
blackhead.
Sweat Glands
• Sweat (Sudoriferous) Glands – more than 2.5
million per person. Two types:
– Eccrine glands – most numerous, all over body.
Produce sweat (water plus salts and vitamins)
• Sweat is acidic (pH 4-6) so inhibits growth of bacteria
– Apocrine glands – confined to armpits and genital
areas of the body. Secrete fatty acids and proteins
• Function unclear but activated during stress, pain, sex
Hair
• Millions of hairs
• Minor protection:
– Head bumps
– Eyelashes
– Nose hairs
• Early humans –
provided insulation
from cold weather
Hair
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Produced by hair follicle
Flexible epithelial structure
Root in follicle
Shaft projects from skin
Matrix (growth zone) of
hair bulb at end of follicle
• Pigment made by
melanocytes
Nails
• Scale-like modification of
epidermis
• Free edge
• Body (visible portion)
• Mostly nonliving
keratinized cells