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Body Tissues
rev 12-12
• 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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• Tissues combine to form organs
• Organs combine to form organ systems
• Organ systems combine to form the
organism (humans)
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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
– examples: skin, lining of mouth, lining of
digestive tract, etc.
• protects underlying tissues
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• reduces friction because it is smooth
• lines blood vessels and helps blood flow more
easily
• absorbs
• secretes
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• Forms glands
– glands are epithelial tissues that are
specialized to synthesize and secrete a
product
• 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 tissue by the basement
membrane
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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
– typically found where absorption and filtration
occur and a thin epithelial layer is adapted for
diffusion across barriers
• many layers--stratified epithelium
– common in high-abrasion areas where protection is
important i.e. lining of the mouth, skin surface
– second name describes the shape of the
cells
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4. Cells occur in 3 types
– squamous--thin and flat cells
• forms the thinnest possible layer for
diffusion & filtration; line vessels
–look like a pancake when viewed
from the side
– mostly found in air sacs of lungs, kidney
glomeruli, lining of vessels
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Classification
of Epithelia
• Squamous
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Figure 4.1b
– cuboidal--cube or rounded cells (about as tall
as are wide)
• major function is secretion but may also be
involved in absorption
– line the ducts of many glands
• has round shaped nucleus which stains very darkly
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Classification
of Epithelia
• Cuboidal
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Figure 4.1b
– columnar--cylindrical cells (tall and column
shaped)
• tall cell with oval shaped nucleus
• mostly associated with absorption, secretion
of enzymes and mucus, and movement of
materials (ciliated cells)
—line the stomach, small and large intestines and a few ducts
• these tissues may also have microvilli, cilia, or
goblet cells (secrete mucus to lubricate
tissues and trap bacteria, viruses and irritating
particles)
– line small bronchi, uterine tubes
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Classification
of Epithelia
• Columnar
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Figure 4.1b
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.
– The basement membrane anchors the
epithelial layer to the stronger connective
tissue underneath.
• Epithelial cells can also be attached to each
other by different types of cell junctions made
up of proteins: 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
– These are very important in epithelial layers
that must control the movement of substances
into or out of the bodydigestive tract,
bladder, kidney tubules
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• Adhesion junctions: (also called spot
desmosomes) are looser in structure and
allow for some movement between cells
so the tissues can stretch and bend i.e.
skin
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• Gap junctions: are connecting protein
channels that permit the movement of ions
or water between 2 adjacent cells i.e. liver,
heart, some muscle tissue
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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
(non-living extracellular matter) which is made by
connective tissue cells and released into the space
between them. The strength of the connective tissue
comes from the matrix, not from the living cells
themselves
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• Matrix is composed of water stabilized by
carbohydrates, glycoproteins, minerals. This
provides mechanical and nutritional support to
the cells. It permits free diffusion of nutrients
and metabolites.
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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 (matrix):
• Collagen fibers--provides strength and slight
flexibility
• Elastic—thin and very flexible coiled elastic
fibers made from the protein elastin; can stretch
without breaking
• 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 made of water, polysaccharides and
proteins that range in consistency from gel to
rubbery.
– It contains many types of cells including fat
cells, mast cells (immune cells that detect
foreign substances in tissue spaces and
initiate an inflammatory response), various
WBC, and fibroblasts (the cells responsible
for producing and secreting the proteins that
compose the collagen, elastic and reticular
fibers).
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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 and
around muscles, and around blood vessels,
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
– primarily attaches muscles to bones or to
other muscles, bones to bones
– usually found in tendons, ligaments and
joint capsules
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Elastic Connective Tissue:
• Surrounds organs that have to reguarly change
shape or size
– Stomach, bladder, vocal cords
• 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 (this
is why it functions as a cushion)
– Because there are no blood vessels, mature
cells obtain nutrients by diffusion through the
ground substance (matrix).
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• Maintains the shape of certain body parts i.e. tip
of your nose
• Protects and cushions joints; cartilagenous disks
cushion the vertebrae, forms the tough covering
of bones at joints (and helps reduce friction)
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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
to body cells and carry away the waste products.
• White blood cells 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) (large, round cells which look
empty but really contain an oil droplet which takes up
most of the cell and pushes the nucleus to one side)
• Primary role is insulation and cushioning; stores
energy; forms a protective layer around internal
organs
• Found below skin, around various organs, and
around certain muscles
• The number of adipocytes you have is partly
determined by genetics
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Other Tissue Types
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.
– Is located in the brain, spinal cord and nerves
• Neuron: specialized nervous system cell which
generates and transmits impulses.
– Structural components: cell body, dendrites,
axon
– Glial (Neuroglial) cells: support neuron cells
and supplies with nutrients
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INTEGUMENTARY SYSTEM
(also known as 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; no blood vessels
– 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.
– Primary reason for differences in skin color is the
activity (not number) of melanocytes. In darker races,
melanocytes are always active; in lighter skinned
people, the melanocytes are activated by UV radiation.
• 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 (a fibrous protein,
also a component of fingernails and hair)
• When cells are dead and water has evaporated, keratin
forms a tough barrier which microorganisms generally
have a tough time entering
– Provides protection from abrasion, cells can be rubbed off
and will be replaced; also protects our body from drying
out
• Skin continually being renewed throughout our life
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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 because the number of
fibers in the dermis decreases.
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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. Because of the
waste products of bacteria who live off of
apocrine sweat glands, we can have an odor
in these areas.
– Sweat helps in temperature regulation and
contains an antibiotic called dermicidin
• Arrector pili muscles which make our hair
stand up; produce “goose bumps”
• Blood vessels: supply nutrients, remove waste,
assist in temperature regulation
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• Nails: a scale like modification of the epidermis
that forms a clear protective covering on the
dorsal surface of the ends of fingers and toes
• 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
(primarily muscles)
• 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:
–
–
–
–
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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
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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
for 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 it
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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