Tissues

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Body Tissues
rev 9-11
• Tissue: group of cells that are similar in
structure and perform a common function
• 4 primary tissue groups
– Epithelial
– Connective
– Muscle
– Nervous
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Epithelial Tissue
• sheet of cells that covers a body surface
or lines a body cavity;
• helps form boundaries between different
body environments
• protects underlying tissues
• reduces friction because it is smooth
• absorbs
• secretes
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• Forms glands
• Characteristics of Epithelial Tissue
1. Cells are packed closely together
2. One surface of the tissue is free while the
other surface is attached to the underlying
connective
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3. Epithelial tissues are typically given 2
names--first name indicates the number of
cell layers present
• one layer of cells is called simple epithelium
• many layers--stratified epithelium
– second name describes the shape of the
cells
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4. Cells occur in 3 types
– squamous--thin and flat cells
– cuboidal--cube or rounded cells
– columnar--cylindrical cells
• these tissues may also have microvilli, cilia,
or goblet cells
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Basement Membrane
• Underneath the cells of epithelial tissue is a
supporting non-cellular layer called the
basement membrane and beneath that is
typically a layer of connective tissue.
• Epithelial cells can also be attached to each
other by different types of cell junctions:
– Tight junctions,
– Adhesive junctions,
– Gap junctions
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• Tight junctions: seal plasma membranes of
adjacent cells so tightly that nothing can pass
between the cells
• Adhesion junctions: (also called spot
desmosomes) are looser in structure and allow
for some movement between cells so the tissues
can stretch and bend
• Gap junctions: are connecting protein channels
that permit the movement of ions or water
between 2 adjacent cells
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Connective Tissue
found everywhere in the body
Major functions:
1. Binding or connecting of body parts
2. Support of organs against gravity
3. Protection
4. Cushioning, insulation; energy storage; fat
storage
5. Produces blood cells
6. Transportation
• Has comparatively few cells and a lot of matrix
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Types of Connective tissue:
• Fibrous-connects various body parts; provides
strength, support and flexibility
– consists of several types of fibers and cells
embedded in a gel-like ground substance:
• Collagen fibers--provides strength and slight
flexibility
• Elastic—thin and very flexible coiled elastic
fibers made from the protein elastin
• Reticular—made of thinner collagen fibers which
interconnect with each other; serves as internal
framework for some organs; fiber flexibility is
between elastic and collagen fibers
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• The various fibers are set in a ground
substance (called the matrix)
• It contains many types of cells including fat cells,
mast cells, various WBC, and fibroblasts.
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Fibrous connective tissues are subclassified
according to the density and arrangement of
their fibers:
Loose Areolar connective tissue
• most common type
• contains collagen fibers and elastic fibers in a
“loose” irregular pattern; is very flexible but
not strong
• usually found below the skin, between
muscles, and around blood vessels, muscles
and organs.
• Spaces between fibers are good storage
areas.
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Dense (Regular) Connective Tissue
– fibers are densely packed and run in the
same direction
• is very strong when stress is in the same
direction as the fibers run
• has few blood vessels and takes a long time to
heal
• functions to bind, protect and connect
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Elastic Connective Tissue:
• Surrounds organs that have to reguarly change
shape or size
• Contains a high proportion of elastic fibers
Reticular connective Tissue:
• Also called lymphoid tissue
• Serves as the internal framework of soft organs
such as the liver, lymphatic system organs
• Is made up of thin, branched reticular fibers
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Specialized connective tissues:
Cartilage: is the transition tissue from which bone
develops
• Produced by chondroblasts which become trapped
and enclosed in areas called lacunae; no blood
vessels, high collagen fiber and water content
• Because there are no blood vessels, mature cells
obtain nutrients by diffusion through the ground
substance.
• Maintains the shape of certain body parts
• Protects and cushions joints; cartilagenous disks
cushion the vertebrae, forms the tough covering of
bones at joints
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Bone: connective tissue which contains only a few
living cells
• inorganic matrix with calcium and phosphate
salts for hardness
Blood: cells are suspended in a fluid matrix called
plasma. Considered a connective tissue
because all blood cells derive from earlier stem
cells located within bone.
• Red blood cells transport oxygen and nutrients
• White blood cells (WBC) function in the
immune system
• Platelets help to form blood clots following an
injury.
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Adipose (Fat) tissue: specialized for fat storage
– has few connective tissue fibers and almost
no ground substance; primarily made up of
adipocytes (fat cells)
• Primary role is insulation and cushioning; stores
energy; forms a protective layer around internal
organs
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Muscle Tissue: Contracts for Movement
Muscle tissue is made up of tightly packed cells
called muscle fibers. The muscle fiber cytoplasm
contains proteins which allow the cell to contract
3 types of muscle tissue
• Skeletal muscle moves body parts.
– Is connected to tendons which are connected
to bones.
– Voluntary, multinucleated
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Cardiac muscle:
– Found only in the heart
– Individual cells are shorter than skeletal, have single
nucleus
– Cells are arranged parallel to each other
– Have intercalated disks which function as gap
junctions for direct electrical contact with neighboring
cells. This allows one cell to activate all its
“neighbors” so the heart can contract in a coordinated
way.
– Involuntary muscle
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Smooth muscle:
– Surrounds hollow organs and tubes i.e. blood
vessels, digestive tract
– Smaller cells than skeletal muscles; have a single
nucleus
– Cells arranged parallel to each other
– Have gap junctions between cells so that it works in a
coordinated fashion
– Involuntary muscle
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Nervous Tissue: Transmit Impulses
• Nervous tissue is made up of cells which are
specialized for generating and transmitting
electrical impulses. It is a rapid communication
network for the body.
• Neuron: specialized nervous system cell which
generates and transmits impulses.
– Structural components: cell body, dendrites,
axon
– Glial cells: support neuron cells and supplies
with nutrients
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INTEGUMENTARY SYSTEM (SKIN)
Functions: --outer covering of the body
– protects from dehydration
– protects from injury
– protects against invasion by microorganisms
(bacteria and viruses
– helps regulate body temperature
– synthesizes vitamin D
– Sensory awareness: receptors for touch,
vibration, pain and temperature provide
information about the environment
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Skin consists of
– epidermis: outermost layer of stratified
squamous epithelial tissue
– is made up of 5 sub-layers: stratum
corneum, stratum lucidum, stratum
granulosum, stratum spinosum, and
stratum basale layers
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• Innermost layer: stratum basale undergoes almost
continuous mitosis. Cells are pushed upward by the
production of new cells beneath them and create
“new” skin
– Melanocytes are found here; they produce
melanin, a brown pigment.
• Stratum spinosum: thickest layer; cells
switch from a mitotic role to producing keratin.
– Keratin is a waterproofing protein which also
toughens the outer surface of the skin.
– Macrophages (phagocytes which protect us from
infection) are also present throughout this skin
layer
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• Stratum granulosum: acts as a protective
shield to the layers below it.
• Stratum lucidum: thin layer with keratin
production occurring
• Stratum corneum: outermost and toughest
layer of epidermis
– Outermost layers of epidermis are made up of
dead, dried out epithelial cells which contain
keratin
• When cells are dead and water has
evaporated, keratin forms a tough barrier
– Provides protection from abrasion, cells can be
rubbed off and will be replaced; also protects
our body from drying out
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• The dermis is primarily dense connective tissue
with collagen, elastic and reticular fibers in a
ground matrix.
– The fibers allow the skin to stretch when we
move
– give it strength to resist abrasion and tearing.
– Our skin becomes less flexible and more
wrinkled as we age.
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– composed of two sub-layers
– this layer “binds” the body together
– richly supplied with nerve fibers, blood
vessels, hair follicles, sebacious (oil)
glands, sweat glands and lymphatic
vessels
• Sensory nerve endings: for heat, cold,
touch, deep pressure, vibration; provide
information about the outside environment
– Nerve fibers: Meissner’s corpuscles-light
touch
Pacinian corpuscles-deep pressure
Free nerve endings-pain
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• There are 2 types of sweat glands:
– Eccrine which are throughout the body and
– Apocrine which are primarily in the groin and
underarm (axillary) areas. Sweat helps in
temperature regulation and contains an
antibiotic called dermicidin.
• Arrector pili muscles which make our hair
stand up
• Blood vessels: supply nutrients, remove waste,
assist in temperature regulation
• Nails: a scale like modification of the epidermis
• Ceruminous or wax gland
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• Hypodermis: supportive layer consisting of
loose connective tissue containing fat cells
• also called subcutaneous tissue or
superficial fascia
• anchors the skin to underlying structures
• is flexible so the skin can move and bend
• its fat cells insulate against excessive heat
loss and cushion against injury
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Diseases of the Skin
Impetigo
• A contagious, superficial infection in bullous
(blister like) and nonbullous forms
– Usually occurs on face, around the mouth and nose
– ITCHY!
• Causes:
– Staph aureus usually causative organism
• When blister breaks, liquid (exudate) can cause
more lesions on rest of body
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• Treatment:
–
–
–
–
–
Antibiotics (penicillin, cephalosporin, zithromax
Anti-itch cream—itching spreads impetigo
Frequent washing of lesions with antibacterial soap
Patient has own towels, bedding, etc
Caretaker must wash hands carefully and frequently
Tinea (Skin Fungus) infections:
• can occur directly (through contact with infected
lesions) or indirectly (through contact with
contaminated articles-shoes, towels, or shower
stalls
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• Tinea capitis
– Small, spreading blister like rash on scalp
causing patchy hair loss and scaling
• Usually affects children; in babies called “cradle
cap”
• Tinea corporis (also known as ringworm):
– produces flat lesions on the skin which, as
they get bigger, have healed centers and
look like a ring
• Tinea pedis (Athlete’s foot)
– Scaling and blisters between the toes
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• Tinea cruris (Jock itch)
– Produces red, raised, sharply defined, itchy lesions in
the groin that can extend to the buttocks, inner thighs,
and the external genitalia.
– Warm weather and tight clothing encourage fungal
growth
• Treatment for all Tineas
– Usually topical creams
• Continue applying cream for 2 weeks after lesions
heal
• Observe for secondary infections
• Expose areas (when possible) to air
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Scabies
• Infection by the “itch mite” which causes a
sensitivity reaction
• Occurs primarily in areas with overcrowding and
poor hygiene
• Very contagious; transmitted through skin or
sexual contact
• Mite lives in the skin. Female burrows into the
skin to lay her eggs. The larvae emerge to
copulate and then reburrow under the skin
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• Causes itching which intensifies at night and can lead to
a secondary bacterial infection
• Lesions are usually excoriated, threadlike, about 3/8 inch
long and typically seen between fingers, on flexor
surfaces of wrist, on elbows, underarm, at the waistline,
and can be seen in genitalia
Treatment:
• Cream over entire skin surface and left on for 8-12 hours
to 5 days (depending on the specific type of cream)
• Application usually repeated in 1 week
• Oral antihistamine
• Wash clothes and bedding in very hot water or dryclean
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Lice or Pediculosis
• Pediculus capitis (head lice)
• Pediculus corporis (body lice)
• Pediculus pubis (crab lice)
– Lice feed on human blood and lay their eggs (nits) in
body hairs or clothing fibers
– After nits hatch, lice must feed within 24 hours or die.
Mature in 2-3 weeks
– When louse bites it injects a toxin into the skin that
produces irritation and a purpuric spot (spot
containing leaked blood).
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– Causes itching which can cause skin breakdown,
swollen lymph glands, rash
• Treatment:
– Special shampoo, creams
– Shampoo applied and washed off after 5-10 minutes
(depending on specific shampoo); repeat in 7-10 days
– After this, all nits should be combed out of hair with a
metal nit comb
– Wash clothing and bedding
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Psorias
• Chronic disease marked by epidermal
proliferation; skin is covered by scales
– Life cycle of normal skin is ~ 28 days and then if
sloughs off; life cycle of psoriatic skin is 4 days so the
cell can’t mature resulting in thick, flaky skin
• Has remissions and exacerbations
• Tendency to develop this is genetic
• Symptoms: itching; dry, cracked skin lesions
which can cause pain.
– Lesions commonly appear on scalp, chest, elbows,
knees, shins, back, and buttocks
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• Treatment:
– No permanent cure exists
– Lotions or tar preparations to help soften the scales
which then can be scrubbed off gently; ultraviolet light
to retard rapid cell production;
– Steroid creams to control disease
– Antihistamines to relieve itching
• Not contagious
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Eczema
• Chronic inflammatory response often associated
with allergies, irritating chemicals, temperature and
humidity, skin irritation (i.e. tight clothing), and
emotions.
– Lesions generally begin as raised areas on skin
– Typically flares and subsides repeatedly
• During flareups, itching and scratching can
cause edema, crusting and scaling
• Treatment: eliminate allergens and irritations
• Antihistamines to relieve itching, steroid
creams; Hydrate skin; Short baths/showers in
cool water
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