Download Tissue: The Living Fabric

Tissue: The Living Fabric
Chapter 4
Chapter Outline
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Epithelia 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
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
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
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 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
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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
– Together the basal and reticular lamina form the
basement membrane
– 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
– 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
–
–
–
–
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
–
–
–
–
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
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
Important functions are secretion and
absorption
In glands it forms the secretory portion
of the gland and portions of the ducts
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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Thick membrane composed of several
cell layers
Surface cells are flattened (squamous)
while deeper cell layers are cuboidal
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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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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Several cell layers
thick
Rare in the body it is
found in large ducts
and the male urethra
Functions are to
provide 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 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
Transitional Epithelium
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Transitional
epithelium
lining of the
bladder,
relaxed state
Glandular Epithelia
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A gland consists of one or more cells that
make a secretion
Secretions are usually water based fluids
containing proteins
Glands are classified by route of secretion:
– endocrine
– exocrine
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(internal secretion)
(external secretion)
Glands are classified by number of cells:
– unicellular exocrine glands
– multicellular exocrine glands
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 secret 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 secret their products
through a duct onto a body surface or
into a body cavity
These glands secret mucous, sweat, oil,
saliva, bile, digestive enzymes, and many
other substances
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
Glandular Epithelium:
Multicellular Exocrine Glands
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There are two categories of Multicellular
glands based on their duct structures
– Simple glands have an unbranched duct
– Compound glands have a branched duct
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The glands are also described by the
structure of their secretory parts
(tubular, alveolar or tuboloalveolar)
The glands are also described by the way
a gland secrets its products (merocrine,
holocrine, aprocrine)
Glandular Epithelium:
Modes of Secretion
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Merocrine glands (salivary)
– Secret their products by exocytosis
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Holocrine glands (sebaceous)
– 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
Mode of Secretion: Apocrine
Unicellular Exocrine Glands
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These are single cells interposed in an
epithelial sheet between cells with other
functions
These glands produce mucin which
dissolves in water to form mucus
These cells are secreted by the goblet cells
of the respiratory and digestive tracts
Goblet cells
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Found in
columnar
epithelium cells
lining the
intestinal and
respiratory
tract
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:
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–
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support and binding
protection
insulation
transportation
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 substances
– The matrix creates the ability to bear weight,
withstand tension, and abrasion
Connective Tissue: Model
Structural Elements
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Any connective tissue is made up of three
elements; ground substance, fibers, and
cells
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 fibers
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
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
attach to the core protein
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
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
Active mitotic cells are called blasts
which implies a forming cell
The primary cells types of connective
tissue are:
–
–
–
–
fibroblast - connective tissue
chondroblast - cartilage
osteoblast - bone
hemocytoblast - 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)
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Connective tissue also harbor an
assortment of other cell types
– white blood cells - infection
– mast cells - detect foreign substances
– macrophages - phagocytize a broad variety
of foreign molecules and bacteria
Connective Tissue:
Mesenchyme
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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
Mesenchyme
Connective Tissue:
Connective Tissue Proper
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Loose Connective
Tissue
– Areolar
– Adipose
– Reticular
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Dense Connective
Tissue
– Dense Regular
– Dense Irregular
– Elastic
Areolar Connective Tissue
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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 salt
for the surrounding tissues
Areolar: Location
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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
Areolar Tissue: Function
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Wraps and cushions organs
Macrophages phagocytize bacteria
Plays important role in inflammation
Holds and conveys fluid
Areolar Tissue
Adipose (fat) Tissue
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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
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Under skin
Around kidneys and eyeballs
In bones
Within abdomen
Within breasts
Adipose Tissue
Adipose Tissue: Function
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Provides reserve food source for fuel
Insulates against heat loss
Supports and protects organs
Adipose Tissue
Reticular connective tissue
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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
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Lymphoid organs
– Lymph nodes
– Bone marrow
– spleen
Reticular Connective Tissue
Reticular Connective Tissue:
Function
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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
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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
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Dense regular connective tissue forms:
– Tendons
– Aponeuroses
– Ligaments
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Muscle to bone
Muscle to muscle or bone
Bone to bone
Ligaments have a little stretch, tendons
very little
Dense Regular Connective Tissue
Dense Regular Connective Tissue:
Function
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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
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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
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Dermis of the skin
Submucosa of digestive tract
Fibrous capsules of organs and joints
Dense Irregular Connective Tissue
Dense Irregular Connective Tissue:
Function
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Able to withstand tension exerted in
many directions
Provides structural strength to many
diverse tissues and organs
Dense Irregular Connective Tissue
Cartilage
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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
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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
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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
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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
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
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
Hyaline Cartilage: Function
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

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
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
Fibrocartilage
Bone
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
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

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
All structural elements of the skeletal
system
Appears as long, flat, short, and irregular
bone
Includes compact and spongy bone
Bone
Bone: Function
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
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
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
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:
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
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
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

Mucosae line body
cavities that are
open to the
exterior
These are moist
membranes
bathed by
secretions
Often adapted for
absorption and
secretion
Epithelial Membranes:
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
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
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
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
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 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 decreases making tissue repair
less efficient
Declining circulatory efficiency results in
less nutrient delivered to tissue
Dietary choices also influences tissue
repair
TISSUE: THE LIVING
FABRIC
END OF CHAPTER