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Tissue: The Living Fabric
Chapter 4
Chapter Outline
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Epithelial Tissue
Connective Tissue
Epithelial Membranes
Nervous Tissue
Muscle Tissue
Tissue Repair
Developmental Aspects of Tissue
Introduction to Tissue
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The human body is a multicellular
organism
– Its cells form tight communities that have
similar functions
– Cell specialization allows for division of
labor
– However, the risk is that loss of specialized
cells means the loss of that function and
potentially the individual
Introduction to Tissue
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A tissue is defined as a group of closely
associated cells that perform related
functions are similar in structure
Tissue do not consist entirely of cells as
between the living cells is nonliving
extracellular material
Tissue
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Groups of closely associated cells that are
similar in structure and function are
called tissues
Four primary tissues interweave to form
the “fabric” of the body
–
–
–
–
Epithelial
Connective
Muscle
Nervous
(covering)
(support)
(movement)
(control)
Organs
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Tissues are organized into organs
– Most organs contain all four tissue types
– However, most organs will have one
predominant tissue type present
– The arrangement and proportion of tissues
present determines the function of the organ
SECTION I
EPITHELIAL TISSUE
Epithelial Tissue
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Epithelial tissue is a sheet of cells that
covers a body surface, a body cavity, or
has a glandular function
Epithelia form the boundaries between
environments
Epithelial has many functions including;
protection, absorption, filtration,
excretion, secretion, and sensory reception
Epithelial Tissue
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Epithelial tissue constitutes all the inner and
outer surfaces of the body including;
–
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Skin
Viscera of the digestive and respiratory system
The lining of body cavities
Linings of blood vessels
Most glandular tissue
Special Characteristics of Epithelium
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Cellularity
Epithelial tissue is composed
almost entirely of close packed
cells with little extracellular
material lying in the space
between them
Specialized Cells form continuous sheets.
contacts
Adjacent cells are bound
together at many points
by
lateral contacts including,
tight
junctions and desmosomes
Special Characteristics of Epithelium
Junctions &
Desmosomes
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Tight junctions occur
where protein
molecules in adjacent
cells fuse together to
form an impermeable
junction
Desmosomes are
anchoring junctions
that bind adjoining
cells and prevent their
separation
Gap
Junctions
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Gap junctions allow
chemical substances to
pass to adjacent cells
Cells connected by
hollow connexons
Found in electrically
excitable tissues (heart
and smooth muscle)
Ion passage from one
cell to another helps to
synchronize electrical
activity
Special Characteristics of Epithelium
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Polarity
– All epithelial tissue has an upper (apical) surface
exposed to the body exterior or an internal cavity
– All epithelia exhibit polarity where the cells near
the apical surface differ from those at the basal
surface
– Apical surfaces can be smooth, most have
microvilli, and some have cilia
– The basal surface of epithelium is called the basal
lamina, which acts as a selective filter that
determines which molecules are allowed to enter
the epithelium
Special Characteristics of Epithelium
Special Characteristics of Epithelium
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The basal surface of epithelium lies on a thin
sheet called a basal lamina, which is part of the
basement membrane
Deep to the basal lamina is a layer of reticular
fibers belonging to the underlying connective
tissue
Together the reticular fibers and the basal
lamina form the basement membrane
Special Characteristics of Epithelium
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Supported by connective tissue
– All epithelial tissue sheets rest upon and are
supported by connective tissue
– Deep to the basal lamina is the reticular lamina, a
layer of extracellular material containing a fine
network of collagen fibers from the underlying
connective tissue
– The basement membrane reinforces the epithelial
sheet enabling it to resist stretching and tearing
– It also defines the epithelial boundary
Special Characteristics of Epithelium
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Innervated but avascular
– Epithelial tissues are supplied with nerve
cells
• Thus they can contribute to sensory function
– Epithelial tissues contain no blood vessels
• Epithelial tissue receive nutrients by substances
diffusing from blood vessels in the underlying
connective tissue layers
Special Characteristics of Epithelium
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Regeneration
– Epithelial cells have a high regenerative
capacity
– Epithelial cells are exposed to friction, others
are damaged by hostile substances in their
environment
– If nourished adequately, epithelial tissue can
replace lost cells rapidly by cell division
Classification of Epithelia
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Each epithelium is given two names:
– The first name references the number of
epithelial cell layers present
• Simple
• Stratified
– The second name describes the shape of the
cells present in the epithelial cell layer
• Squamous
• Cuboidal
• Columnar
Simple and Stratified Epithelium
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Simple epithelium is composed of a single
tissue layer
– It is usually found where absorption and
filtration occur, thus a thin layer facilitates
these processes
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Stratified epithelium consists of two or
more layers stacked one upon the other
– It is usually found in areas of high abrasion
and functions to protect underlying cell
layers
Epithelial cells
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All epithelial cells are hexagon shaped
This shape allows the cells to be tightly
packed with little wasted space
Epithelial cells look like a honeycomb
Epithelial cells vary in height and are
named on the basis of shape
– Squamous cells are flattened and scalelike
– Cuboidal cells are boxlike in appearance
– Columnar cells are tall and column shaped
Epithelial shape
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Squamous - flat
and scale-like
Cuboidal - boxlike
Columnar - tall
and column shaped
Simple Epithelia
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All the cells in the layer have the same
shape
There are four major classes of simple
epithelia
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–
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Simple squamous
Simple cuboidal
Simple columnar
Pseudostratified columnar (Highly modified
simple epithelium)
Stratified Epithelia
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There are also four major classes of
stratified epithelia
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Stratified squamous
Stratified cuboidal
Stratified columnar
Transitional epithelium (a modified
stratified squamous epithelium)
Simple Squamous Epithelium
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The simplest form of epithelium
A single layer of flattened cells
Thin and permeable, this type is often
found where filtration or diffusion is a
priority
Two simple squamous epithelium have
special names related to their location
– Endothelium (lining blood vessels)
– Mesothelium (found in serous membranes)
Simple Epithelia
Simple Squamous Epithelium
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Simple squamous
epithelium
forming walls of
alveoli (air sacs) of
the lung
Simple Epithelium:
Simple Cuboidal Epithelium
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Single layer of cube like cells
Important functions are secretion and
absorption
It forms ducts and secretary portions of
small glands and tubules in the kidneys
Simple Epithelium:
Simple Cuboidal Epithelium
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Simple cuboidal
epithelium in
kidney tubules
Simple Epithelium:
Simple Columnar Epithelium
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Consists of a single layer of tall, closely
packed cells
It lines the digestive tube from stomach
to anal canal
Important functions are secretion and
absorption and it forms a layer thin
enough for ion transport yet thick enough
to house the cellular structures of ion
transport
Simple Epithelia:
Simple Columnar Epithelium
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Consists of a single layer of tall cells
– unciliated in the digestive tract
• associated with absorption and secretion
• mircovilli add surface area and aid absorption
• globlet cells secret protective lubricants
– ciliated in the respiratory passages
• cilia “sweep” or propel mucus by ciliary action
Simple Epithelium:
Simple columnar epithelium
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Simple
columnar
epithelium of
the stomach
mucosa
Simple Epithelium:
Pseudostratified Columnar
Epithelium
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Single layer of cells of differing heights
The cell nuclei are located at differing
levels above the basement membrane
giving the false (pseudo) impression of
multiple cell layers
Ciliated in the upper respiratory tracts
Nonciliated in large body ducts
Simple Epithelium:
Pseudostratified Epithelium
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Pseudostratified
ciliated epithelium
lining the human
trachea
Stratified Epithelium:
Stratified Squamous Epithelium
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Tissue is composed of several cell layers
Surface cells are flattened (squamous)
while deeper cell layers are cuboidal or
columnar
Surface cells are full of keratin and dead,
while basal cells are alive and active in
cell mitosis
Protective in function, these cells are
found in areas subjected to abrasion
Stratified Epithelium:
Stratified Squamous Epithelium
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Stratified
squamous
epithelium
lining the
esophagus
Stratified Epithelium:
Stratified Cuboidal Epithelium
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Generally two layers of cube-shaped cells
Form large ducts of some glands
Function to protect
Relatively rare tissue type
Stratified Epithelium:
Stratified Cuboidal Epithelium
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Location
– Largest ducts of sweat glands, mammary
glands and salivary glands
– No table provided in Marieb A & P, 5th
edition
– Table 4.3f in 3th edition Marieb and Mallatt
Stratified Epithelium:
Stratified Cuboidal Epithelium
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Stratified
cuboidal
forming a
salivary
duct
Stratified Epithelium:
Stratified Columnar Epithelia
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Several Cell layers present
Basal cells are cuboidal while superficial
cells are columnar
Rare in the body; found in the large ducts
of some glands and in the male urethra
Functions include protection and
secretion
Stratified Epithelium:
Stratified Columnar Epithelium
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Stratified
columnar
epithelium
lining the male
urethra
Stratified Epithelium:
Transitional Epithelium
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Forms the lining of hollow urinary organs
Resembles both stratified squamous and
cuboidal
The cells vary in appearance depending on
the degree of distension of the organ
The ability of the epithelium to thin under
pressure allows for a greater volume of
urine to pass through these organs
Transitional Epithelium
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Transitional
epithelium
lining of the
bladder,
relaxed state
Epithelial Surface Features
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The apical, lateral and basal cell surfaces
of epithelia have special features
Apical surfaces have microvilli and cilia
Lateral surfaces have cell junctions
Basal surface has a basal lamina
Apical Surface Features
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Microvilli are fingerlike extension of the
plasma membrane of apical epithelial cells
They occur on almost very moist
epithelium in the body
Most abundant on epithelia that absorb
nutrients (small intestine) or transport
ions (kidney)
Microvilli maximize the surface area
across which small molecules enter or
leave cells
Apical Surface Features
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Microvilli are abundant on epithelia that
secrete mucus, where they help anchor the
mucus sheets to the epithelial surface
Finally, microvilli may act as “stiff knobs”
to resist abrasion
Apical Surface Features
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Cilia are whip-like,
highly motile
extensions of the
apical surface
membranes of
certain epithelia cells
Each cilium contains
a core of microtubules, nine pairs
which encircle one
pair
Apical Surface Features
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The center set of
microtubules is an
axonene and each
pair is called a
doublet
Ciliary movement is
generated when
adjacent doublets
grip one another with
side arms made of
the protein dynein
causing ocillation
Apical Surface Features
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When the side arms
start to oscillate the
doublets slide against
one another causing
the cilium to bend
The cilia on an
epithelium bend and
move in coordinated
waves
The waves push
mucus over its
surface
Apical Surface Features
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Each cilium executes a propulsive power
stroke, followed by a recovery stroke
This sequence ensures that fluid is moved in
one direction only
Apical Surface Features
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An extremely long, isolated cilium is
called a flagellum
The only flagellated cells in the human
body are male sperm
Sperm use their flagella to swim through
the female reproductive tract
Lateral Surface Features
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Three factors act to hold epithelial cells
to one another
– Immunoglobulin-like proteins in the plasma
membranes are linked together
– The wavy contours of the membranes of
adjacent cells join in a tongue and groove
fashion
– There are special cell junctions seal off the
extracellular space
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Cells junctions are characteristic of
epithelia cells but can be found in other
tissue types as well
Lateral Surface Features
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Desmosomes are the main junctions for binding
cells together and are scattered along cell margins
Lateral Surface Features
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The surface of each plasma membrane has an area
called the circular plaque
Lateral Surface Features
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The plaques of adjacent cells are joined by linker
proteins called cadherins
Lateral Surface Features
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Cadherins project from the cell membranes of both
cells and interdigitate like the teeth of a zipper in
the extracellular space
Lateral Surface Features
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Intermediate filaments which are cytoskeletal
elements that resist tension insert into each plaque
from the inner cytoplasmic side
Lateral Surface Features
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Cadherins project from the cell membranes of both
cells and interdigitate like the teeth of a zipper in
the extracellular space
Lateral Surface Features
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Bundles of intermediate filaments extend
across the cytoplasm and anchor at other
desmosomes on the opposite side of the
same cell
This arrangement holds not only
adjacent cells together but also
interconnects all the intermediate
filaments of the entire epithelium into one
continuous network of strong “guy wires”
This distributes tension forces evenly
across the entire epithelial sheet
Lateral Surface Features
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Tight junctions seal off the extracellular space
Lateral Surface Features
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Tight junctions are typically located in the apical
region of most epithelial cells
Lateral Surface Features
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At tight junctions the adjacent cells are
so close that some proteins in their
plasma membranes are fuse
Fusion forms a seal that closes off the
extracellular space
This prevents molecules from passing
between the cells of epithelial tissue
Lateral Surface Features
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Gap junctions or nexus is a spot-like junction that
can occur anywhere along the lateral membranes of
adjacent cells
Lateral Surface Features
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Gap junctions let small molecules move
directly between neighboring cells
At gap junctions the adjacent plasma
membranes are very close and the cells
are connected by hollow cylinders of
protein (connexons)
Ions, simple sugars, and other small
molecules pass through these cylinders
from one cell to the next
Basal Lamina Features
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At the border between the epithelium and the
connective tissue is a supporting sheet called
the basal lamina
Basal Lamina Features
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The basal lamina is a thin, noncellular
sheet consisting of proteins secreted by
the epithelial cells in the overlying layer
Functionally, the basal lamina acts as a
selective filter
It determines which molecules from
capillaries in the underlying connective
tissue will be allowed to enter the
epithelium
Basal Lamina Features
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The basal lamina also acts as scaffolding
along which regenerating epithelial cells
can migrate
Regeneration can typically occur because
infections and mechanisms that destroy
the epithelial cells usually leave the basal
lamina intact
Without a basal lamina, regeneration of
the epithelial tissue is more difficult
Basal Lamina Features
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Directly deep to the basal lamina is a layer of
reticular fibers belonging to the underlying
connective tissue
Basal Lamina Features
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Combined the reticular fibers and the
basal lamina form the basement
membrane
While the basal lamina and the basement
membrane are different structures the
terms are sometimes used
interchangeably which is incorrect
Glandular Epithelia
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A gland consists of one or more cells that
make a secretion
Many epithelial cells make secretions
Secretions are usually water based fluids
containing proteins
Secretion is a process whereby gland cells
obtain needed substances from the blood
and transform them chemically into a
product that is discharged from the cell
Glandular Epithelia
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Glands are classified on where they release
their secretion:
– endocrine
– exocrine
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(internal secretion)
(external secretion)
Glands are classified by number of cells:
– unicellular exocrine glands
– multicellular exocrine glands
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Unicellular glands are scattered within
epithelial sheets
Multicellular glands develop by invaginating
into an epithelial sheet and connective tissue
Endocrine Glands
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All endocrine glands eventually lose their
ducts and are considered to be ductless
Endocrine glands produce hormones that
regulate body functions
These glands secrete directly into the
extracellular space
The hormones then enter the blood or
lymphatic fluid
– Pituitary, Thyroid, Parathyroid, Adrenal,
Thymus,, and others
Exocrine Glands
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Exocrine glands are far more numerous
than endocrine
These glands secrete their products
through a duct onto a body surface or
into a body cavity
These glands secrete mucous, sweat, oil,
saliva, bile, digestive enzymes, and many
other substances
Unicellular Exocrine Glands
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The only important example of a
unicellular gland is the goblet cell
Shaped liked a goblet
Distributed in the epithelial linings of the
intestinal and respiratory tract amid
columnar cells with other functions
Produces mucin which when dissolved in
water forms mucus, a slimy coating that
protects and lubricates surfaces
Goblet cells
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Found in
columnar
epithelium cells
lining the
intestinal and
respiratory
tract
Multicellular Exocrine Glands
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Multicellular exocrince glands have two
common structural elements
– An epithelium derived duct
– A secretory unit consisting of secreting cells
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In all but the simplest glands connective
tissue surrounds the secretory unit
supplying it with blood an nerve fibers
Often the connective tissue forms a
fibrous capsule and may subdivide the
gland into lobes
Multicellular Exocrine Glands
Structural Classification
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On the basis of their duct structures,
multicellular exocrine glands are either
simple or compound
– Simple glands have a single unbranched duct
– Compound glands have a branched duct
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The glands are further categorized by
their secretory units
– Tubular (forms tubes)
– Alveolar (forms sacs)
– Tubuloalveolar (contains both types)
Simple Duct Structure
Compound Duct Structure
Multicellular Exocrine Glands
Modes of Secretion
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Merocrine glands (salivary, sweat, pancreas)
– Secret their products by exocytosis and gland is
not altered
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Holocrine glands (sebaceous oil glands)
– The entire cell ruptures releasing the secretions
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Apocrine glands (mammary?)
– The apex of the secretory cell pinches off and
release its secretion
Chief Modes of Secretion
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Merocrine glands
– Secrete products
by exocytosis
– Secretions do not
alter gland
– Secretions leave
gland via duct
Chief Modes of Secretion
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Holocrine glands
– Accumulate their
products within
the gland until
they rupture
– They are replaced
by the division of
underlying cells
– Sebaceous oil
glands are the only
true example in
humans
Chief Modes of Secretion
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Apocrine glands
– Accumulate
products just
beneath free surface
– Apex of the cell
pinches off releasing
its contents
– Cell repairs the
damage and the
process is repeated
– Some controversy
as to its presence in
humans
CONNECTIVE TISSUE
SECTION II
Connective Tissue:
An Introduction
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Connective tissue is found everywhere in
the body but the proportion present in a
tissue varies
Its major functions are:
–
–
–
–
support and binding
holding body fluids
defending the body against infection
Storing nutrients as fat
Common Characteristics
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Common origin
– All tissue arise from mesenchyme layer
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Varying degrees of vascularity
– Tissue vary from rich vascular supply to
avascular
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Extracellular matrix
– The living cells are widely distributed within
a matrix of nonliving extracellular
substances
– The matrix creates the ability to bear weight,
withstand tension, and abrasion
Connective Tissue: Cells in a Matrix
Structural Elements
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Any connective tissue is made up of three
elements; ground substance, fibers, and
cells
Ground substance and fibers make up the
extracellular matrix
The composition and arrangement of
extracellular elements yields the diversity
of connective tissues
It can be delicate and fragile, or thick,
dense and strong
Ground Substance
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Ground substance is an unstructured material
that fills the space between cells and contain
the fiber that support the tissue
It is composed of interstitial fluid, cell
adhesion proteins, and proteoglycans
The ground substance holds fluid and
functions as a medium through which
nutrients and substances can diffuse between
blood vessels and cells
Ground Substance
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Nutrients and oxygen diffuse out of the
capillaries and travel through a watery fluid
in the extracellular matrix to reach the
surrounding cells
Waste molecules from cells diffuse back
through this fluid into the capillaries to be
taken away by the bloodstream
The fluid through which these substances
move is interstitial fluid (tissue fluid) and it
derives from the blood itself
Ground Substance
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
Ground substance is a jelly-like material
consisting of large sugar and sugar-protein
molecules that soak up fluid
The molecules are called glycosaminoglygens
and proteogylcans
Adhesion Proteins
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
Adhesion proteins serve as the “glue”
that allows connective tissue cells to
attach to matrix elements
Adhesion proteins include:
– Fibronectin
– Laminin
Proteoglycans
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Proteoglycans consist of a protein core to
which (GAGs) attach
GAG’s (glycoaminoglycans) are large,
negatively charged polysaccharides that
stick out from the core protein like fibers
of a bottle brush
The polysaccharides trap water and
determine the properties of the matrix
The matrix may vary from fluid to a semi
stiff gel
Connective Tissue: Fibers
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The fibers within connective tissue provide
support
Three type of fibers are found in
connective tissue matrix
– Collagen
– Elastic
– Reticular
Collagen Fibers
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Collagen fibers are extremely tough and
have a high tensile strength
Fibers are able to withstand great
longitudinal stresses
Collagen fibers align along lines of stress
Collagen fibers are located wherever
support is needed to reinforce an organ
or joint
Elastic Fibers
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Elastin has a randomly coiled structure
that allows it to stretch and recoil
Elastin in the matrix gives it a resilient
quality
Collagen fibers limit distension of the
tissue and elastin fibers return the tissue
to its normal length and shape
Found where elasticity is needed
– Skin, lungs, walls of blood vessels
Reticular Fibers
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Fine collagen fibers with a special type of
collagen unit fibril
Form branching networks of delicate
fibers that surround blood vessels and
support soft tissue of organs
Very apparent where connective tissue
abuts other tissue types
– Basement membranes of epithelial cells
Connective Tissue: Cells
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Each major class of connective tissue has
a fundamental cell type
Actively mitotic cells are called “blast”
which implies a forming cell
The primary cells types of connective
tissue are:
–
–
–
–
fibroblast - connective tissue
chondroblast - cartilage
osteoblast - bone
hemocytoblast (hematopiotetic stem cell)blood
Cells (con’t)
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Once the blast cells have synthesized the
matrix they become less active and are
referred to (chrondocyte)
Mature cells maintain the health of the
matrix
If the tissue is damaged they become
active to repair and regenerate the matrix
Cells (con’t)

Connective tissue also harbor an
assortment of other cell types
– white blood cells - infection
• Neutrophils, eosinophils, lymphocytes
– mast cells - detect foreign substances and
initiate a local inflammatory response
– macrophages - phagocytize a broad variety
of foreign molecules and bacteria
Defense Cells Fight Infection
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
Areolar connective tissue is the main
battlefield in the body’s war against
infectious microorganisms such as
bacteria, viruses, fungi and parasites
Every effort is made by the body to
destroy infection at the entry site to
prevent entry into the circulatory system
and the potential spread throughout the
body
Defense Cells Fight Infection
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Areolar connective tissue contains a
variety of defense cells that originate as
blood cells and migrate to the connective
tissues by leaving the capillaries
These defensive cells gather at infection
sites in large numbers
These cells fights infection using a variety
of mechanisms
Defense Cells Fight Infection
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Macrophages are
cells ruffled by
pseudopods
These cells are
non-specific
phagocytic cells
that devour a
variety of foreign
materials
Marcophages will
also dispose of
dead tissue cells
Defense Cells Fight Infection
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Plasma cells secrete protein molecules called
antibodies
Antibodies bind to foreign micro organisms
and mark them for destruction
Once marked a greater amount are destroyed
Defense Cells Fight Infection
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Mast cells lie near
small blood vessels
Mast cells possess
many small granules
containing chemicals
that mediate
inflammation
especially in severe
allergies
Defense Cells Fight Infection

Chemical mediators include histamine,
heparin and proteases (protein degrading
enzymes) and are secreted in response to
infections
– Histamine increases the permeability of the
nearby capillaries, causing more tissue fluid
to leave the bloodstream with the subsequent
swelling of the areolar tissue with fluid is a
major symptom of infection
Defense Cells Fight Infection

Chemicals (continued)
– Heparin in mast cells binds and stores the
other mast cell molecules and regulate their
action

Mast cells also play a role in defense
against parasitic worms, our natural
immunity against bacteria, and the normal
repair of fibers, ground substance, and
blood vessels in connective tissue
Defense Cells Fight Infection


Neutrophils,
lymphocytes, and
eosinophils are white
blood cells that leave
the bloodstream to
fight infection
Neutrophils quickly
enter infected areas
and phagocytize
bacteria
Defense Cells Fight Infection
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
Additional defenses to infection comes
from both the ground substances and the
collagen fibers which slow the progress of
invading microorganisms
However, some bacteria secrete enzymes
that rapidly break down ground
substances or collagen
Connective Tissue: Mesenchyme




Mesenchyme tissue is the first tissue
formed from the mesodermal germ layer
It is made up of star shaped
mesenchymal cells
It is a gel-like ground substance
containing fine fibers
During embryonic development other
tissues differentiate from it
Mesenchyme
Connective Tissue:
Connective Tissue Proper

Loose Connective
Tissue
– Areolar
– Adipose
– Reticular

Dense Connective
Tissue
– Dense Regular
– Dense Irregular
– Elastic
Areolar Connective Tissue



A gel-like matrix with a loose arrangement of all three fiber types
Contains cells, fibroblasts, macrophages,
mast cells, and some white blood cells
Because of the loose nature of the tissue it
serves as a reservoir for water and salts
for the surrounding tissues
Areolar: Location






Most widely distributed type of connective
tissue
Serves as the universal packing material
between tissues
Packages organs
Surrounds capillaries
Forms subcutaneous tissue
Present in all mucus membranes
Areolar Tissue: Function




Wraps and cushions organs
Macrophages phagocytize bacteria
Plays important role in inflammation
Holds and conveys fluid
Areolar Tissue
Adipose (fat) Tissue





Adipose tissue is basically areolar
connective tissue in which the nutrient
storing functioning is greatly increased
Adipocytes predominate tissue as little
matrix is present
Oil (fat) occupies most of cell volume
Compression of the cell nucleus to one
side gives it a name of “signet” cells
Tissue is richly vascular owing to high
metabolic activity
Adipose Tissue: Location





Under skin
Around kidneys and eyeballs
In bones
Within abdomen
Within breasts
Adipose Tissue: Function



Provides reserve food source for fuel
Insulates against heat loss
Supports and protects organs
Adipose Tissue
Reticular connective tissue



Reticular connective tissue resembles
areolar tissue, but the only fibers in the
matrix are reticular
Fibers form a delicate internal network
along which fibroblasts are distributed
Widely distributed in the body, the tissue
provides internal support for many
lymphocytes within lymphatic tissues
such as lymph nodes, the spleen, and
bone marrow
Reticular Connective Tissue:
Location

Lymphoid organs
– Lymph nodes
– Bone marrow
– Spleen
Reticular Connective Tissue:
Function


Fibers form the soft internal skeleton
(stroma) that supports other cell types
Supports many free blood cells in
lymphatic tissue
Reticular Connective Tissue
Dense Regular Connective Tissue





A type of connective tissue consisting of
dense bundles of collagen fibers
Collagen fibers are arranged in parallel
that lie in the direction of pull or stress
Great resistance to tension
Slightly wavy alignment allows for some
degree of stretch
Has few other cells and is poorly
vascularized
Dense Regular Connective Tissue:
Location

Dense regular connective tissue forms:
– Tendons
– Aponeuroses
– Ligaments

Muscle to bone
Muscle to muscle or bone
Bone to bone
Ligaments have a little stretch, tendons
very little
Dense Regular Connective Tissue:
Function



Attaches muscle to bones or to muscles
Attaches bones to bones
Withstands great tensile stress when
pulling force is applied in one direction
Dense Regular Connective Tissue
Dense Irregular Connective Tissue



Same structural components as regular
variety
Dense bundles of collagen fibers are
thicker and arranged with fibers flowing
in more than one plane
Fibers form sheets of tissue that cope
with tension from a variety of directions
Dense Irregular Connective Tissue:
Location



Dermis of the skin
Submucosa of digestive tract
Fibrous capsules of organs and joints
Dense Irregular Connective Tissue:
Function


Able to withstand tension exerted in
many directions
Provides structural strength to many
diverse tissues and organs
Dense Irregular Connective Tissue
Cartilage




Has qualities that intermediate between
dense connective tissue and bone
It is tough but flexible, providing a
resilient rigidity to the structure it
supports
Cartilage is avascular and devoid of
nerve fibers
Ground substance contains large
amounts of GAG, a major adhesion
protein
Cartilage continued




Ground substance contain many collagen
fibers and in some cases elastic fibers to yield
a substance that is quite firm
Cartilage matrix is approximately 80%water
Movement of tissue fluid in its matrix
enables cartilage to rebound after being
compressed
Movement of tissue fluid helps to nourish
cartilage cells
Cartilage continued


The surfaces of most cartilage structures
are surrounded by a well vascularized
dense irregular tissue membrane called a
perichondrium
Nutrients diffuse from the perichondrium
to the matrix and then to the chondrocytes
Cartilage continued

Chondroblasts in growing cartilage
produce new matrix that becomes bone
– During interstitial growth chondroblasts
secrete new matrix to form the cartilage piece
from which a bone will develop
– During appositional growth chondroblasts
secrete new matrix on the superficial surface
of the cartilage structure

The firm cartilage matrix prevents the
cells from becoming widely separated
Hyaline Cartilage




Hyaline cartilage contains large amounts of
collagen fibers formed in an imperceptible
network
Hyaline cartilage provides firm support
with some pliability
It has resilient properties that resist
compression
Matrix appears blue-white with a smooth
almost slick surface
Hyaline Cartilage: Location




Forms most of the embryonic skeleton
Covers the ends of long bones in joint
cavities
Forms costal cartilages of the ribs
Cartilages of the nose, trachea, and
larynx
Hyaline Cartilage: Function



Supports and reinforces with some
pliability
Has resilient cushioning properties
Resists compressive stress
Hyaline Cartilage
Elastic Cartilage



Similar to hyaline cartilage but with
more elastic fibers in the matrix
Elastic fibers gives this tissue greater
resilience to repeated bending
Found where the tissue supports the
shape of the structure while allowing
great flexibility
Elastic Cartilage: Location


Supports the external ear
Epiglottis
Elastic Cartilage: Function

Maintain shape of structure while
allowing great flexibility
Elastic cartilage
Fibrocartilage




Consists of alternating rows of thick
collagen fibers
Matrix is similar to hyaline cartilage but
less firm
It is compressible and resists tension well
Located where strong support and the
ability to withstand heavy pressure is
required
Fibrocartilage: Location



Intervertebral disks of the vertebral
column
Pubic symphysis
Disks of knee joint
Fibrocartilage: Function

Tensile strength with the ability to absorb
compressive shock
Fibrocartilage
Bone




Bone matrix is similar to that of cartilage
but is harder and more rigid
Differs from cartilage in that it contains
more collagen fibers and an added matrix
element of inorganic calcium salts
Osteoblasts produce the matrix then bone
salts are deposited on and between fibers
Well supplied with blood vessels
Bone: Location



All structural elements of the skeletal
system
Appears as long, flat, short, and irregular
bones
Includes compact and spongy bone
Bone: Function





Supports the weight of the body
Protects vital organs and structures
Provides levels for muscles to act upon
Stores calcium, other minerals, and fat
Bone marrow is the site for blood cell
formation
Bone
Blood


Classified as a connective tissue because
it consists of blood cells surrounded by a
nonliving matrix
The fibers of blood are soluble protein
molecules that become visible only during
blood clotting
Blood: Location

Contained within blood vessels of the
circulatory system
Blood
Blood: Function


Transport vehicle of the circulatory
system
Carries nutrients, wastes, respiratory
gases, and many other substances
throughout the body
Blood
EPITHELIAL MEMBRANES
SECTION III
Epithelial Membranes:




Epithelial membranes incorporate both
connective and epithelial tissues
Epithelial membranes are a continuous
multicellular sheet composed of at least
two primary tissues
Can be considered a simple organ
The three common forms of epithelial
membranes are cutaneous, mucous, and
serous
Cutaneous membrane


It is an organ
system consisting
of ketatinized
stratified
squamous
epithelium
attached to a layer
of dense irregular
connective tissue
A dry membrane
Mucous membranes



Mucosae line body
cavities that are
open to the
exterior
These are moist
membranes
bathed by
secretions
Often adapted for
absorption and
secretion
Serous membranes



Moist membranes
found in the central
body cavities
Each consists of a
parietal and visceral
layer
Serous fluid
lubricates the two
layers
NERVOUS TISSUE
SECTION IV
Nervous Tissue



Nervous tissue makes regulates and
controls body functions
Neurons are highly specialized cells that
generate and conduct nerve impulses
Support cells are nonconducting tissue
that support, insulate and protect the
delicate neurons
Nervous Tissue: Location


Brain and spinal cord of the central
nervous system (CNS)
All cranial and spinal nerves of the
peripheral nervous system (PNS)
Nervous Tissue: Function



Transmit electrical signals from sensory
receptors to the brain
Brain interprets impulse for potential
response
Signals from brain to effectors (muscles
and glands) control response
Nervous Tissue
MUSCLE TISSUE
SECTION V
Muscle Tissue:




Muscle tissues are highly cellular, wellvascularized tissue responsible for most
types of body movement
Muscle provides contractile force by
shortening their elongated shape
Muscle cells possess myofilaments
The three kinds of muscle tissue are
skeletal, cardiac and smooth
Skeletal muscle




Skeletal muscle is wrapped by connective
tissue into organs called muscles which
attach to bones
As skeletal muscle contracts it causes
gross body movements
Skeletal muscle is identified by its long
cylindrical form and obvious striations
Voluntary control
Skeletal muscle: Location


Skeletal muscle attach to bones of the
skeletal system
Occasionally muscle will attach to skin
Skeletal Muscle: Function

Produces movement
– Locomotion
– Manipulation of the environment
– Facial expression



Maintains posture
Stabilizes joints
Generates heat
Skeletal Muscle
Cardiac muscle



Occurs in the walls of the heart and no
where else in the body
Muscle cells are striated
Uninucleate cells fit together at unique
junctions called intercalated discs
Cardiac muscle: Location

Found only in the myocardium of the
heart
Cardiac Muscle
Smooth muscle



Smooth muscle is so named because its
fibers have no visible striations
Spindle shaped muscle cells contain one
centrally located nuclei
Closely arranged to form sheets
Smooth muscle: Location

Occurs mainly in the walls of hollow
organs
– digestive tract
– blood vessels
Smooth muscle: Function

Act to propel substances or objects along
internal passageways
– Food
– Urine
– Baby


Involuntary control
Long, sustained contractions
Smooth Muscle
TISSUE REPAIR
SECTION VI
Tissue Repair



Tissue repairs requires cells to divide and
migrate in response to hormones released
by damaged cells
Tissue repair occurs in two major ways:
by regeneration and by fibrosis
Which healing process to occur depends
upon:
– The type of tissue damaged
– The extent of the injury
Tissue Repair


Regeneration is the replacement of
destroyed tissue with the same kind of
tissue
Fibrosis involves the proliferation of
fibrous connective tissue called scar tissue
Tissue Repair: Inflammation




Inflammation of
injury site due to
release of histamine
Capillaries dilate,
become permeable
White blood cells,
antibodies, clotting
proteins arrive
Clotting isolates
injured area
Tissue Repair: Organization




Blood clot replaced
by granulation
tissue
Capillary buds
invade area
Fibroblasts secret
collagen fibers
Macrophages
digest and remove
dead cells
Tissue Repair: Regeneration




Surface epithelium
begins to
regenerate
Granulation tissue
is replaced by
epithelium
Fibrosed area is
found deep to
epithelium
Scar may not be
evident
Factors Affecting Tissue Repair






The type of tissue injured
Type of injury and the immediate care
received
Nutrition
Adequacy of blood supply
State of health of the individual
Age of the individual
Tissue Repair: Tissue Type





Epithelial tissues regenerate very well
Bone and fibrous tissue heal quite well
Smooth muscle and dense regular
connective tissue have very limited
capacity for regeneration
Skeletal muscle and cartilage regenerate
poorly
Cardiac and nerve tissue have no
regenerative capacity and are replaced by
scar tissue
DEVELOPMENTAL
ASPECTS OF TISSUES
SECTION VII
Developmental Aspects of
Tissue



One of the first events of embryonic
development is the formation of the three
primary germ layers
These three germ layers are the
ectoderm, mesoderm and endoderm
These primary germ layers begin to form
the four primary tissues from which all
body organs are derived
Tissue Origins



Epithelial tissue are formed from all
three tissue layers
Muscle and connective tissue form from
the mesoderm
Nervous tissue forms from the ectoderm
Embryonic Germ Layers
Cell Development



By the end of the second month of
development, the primary tissues have
appeared, and all major organs have been
laid down
Tissue growth continues on at a rapid rate
throughout the embryonic and fetal
periods
Most tissues cells except neurons continue
to undergo cell mitosis until adulthood
Adulthood




In adulthood only epithelia and blood
forming tissue are highly mitotic
With increasing age the amount of
collagen generated decreases making
tissue repair less efficient
Declining circulatory efficiency results in
less nutrients delivered to tissue
Dietary choices also influences tissue
repair
TISSUE: THE LIVING
FABRIC
END OF CHAPTER 4