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4
Tissue Level
of Organization
PowerPoint® Lecture Presentations prepared by
Alexander G. Cheroske
Mesa Community College at Red Mountain
© 2011 Pearson Education, Inc.
Section 1: Epithelial Tissue
• Learning Outcomes
• 4.1 Describe epithelial tissues, including cell
shape, layers, and functions.
• 4.2 Discuss the types and functions of
intercellular connections between epithelial
cells.
• 4.3 Describe the structure and function of
squamous epithelium.
• 4.4 Describe the structure, function, and
locations of cuboidal and transitional
epithelia.
© 2011 Pearson Education, Inc.
Section 1: Epithelial Tissue
• Learning Outcomes
• 4.5 Describe the structure, function, and
locations of columnar epithelia.
• 4.6 Describe the structure, function, and
locations of glandular epithelia.
© 2011 Pearson Education, Inc.
Section 1: Epithelial Tissue
• Atoms  Molecules  Cells  Tissues
• Chemical level imaged only with special
techniques
• Cellular level imaged often with electron
microscope
• Body contains trillions of cells
• Only ~200 types of cells
• Tissue level can be imaged with light
microscope
© 2011 Pearson Education, Inc.
Section 1: Epithelial Tissue
• Tissues (cells working together)
• Histology (study of tissues)
• Four basic types
1. Epithelial
2. Connective
3. Muscle
4. Neural
© 2011 Pearson Education, Inc.
The tissue level of organization, which consists of four tissue types
The
Chemical
Level
MOLECULES
combine
to form
ATOMS
interact
to form
The
Cellular
Level
that
secrete
and
regulate
CELLS
EXTRACELLULAR
MATERIAL
AND FLUIDS
combine to form
The
Tissue
Level
TISSUES
with special functions
can be
classified as
EPITHELIAL TISSUE
• Covers exposed surfaces
• Lines internal passageways
and chambers
• Produces glandular
secretions
CONNECTIVE TISSUE
• Fills internal spaces
• Provides structural
support
MUSCLE TISSUE
• Contracts to
produce active
movement
NEURAL TISSUE
• Conducts electrical
impulses
• Carries information
• Stores energy
Figure 4 Section 1
© 2011 Pearson Education, Inc.
Module 4.1: Epithelial tissue
• Epithelial tissue
• Epithelia
• Cover exposed surfaces and internal
cavities/passageways
• Often contain secretory or gland cells
• Scattered among other cell types
• Glands (derived from epithelia but more secretory cells)
• Two types
1.
Exocrine glands
•
2.
Secrete on external areas
Endocrine glands
•
© 2011 Pearson Education, Inc.
Secrete hormones into interstitial fluid
The components of epithelial tissue
Epithelial Tissue
Includes
Epithelia
Glands
Epithelia cover exposed
surfaces and line internal
cavities and passageways;
they often contain
secretory cells, or gland
cells, scattered among the
other cell types.
Glands are derived
from epithelia, but
secretory cells
predominate; there are
two types:
Exocrine Glands
Endocrine Glands
Exocrine glands secrete
onto external surfaces or
into internal passageways
(ducts) that connect to the
exterior.
Endocrine glands secrete
hormones or precursors
into the interstitial fluid,
usually for distribution by
the bloodstream.
Figure 4.1
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1
Module 4.1: Epithelial tissue
• Functions of epithelial tissue
• Provide physical protection
• Control permeability
• Provide sensation
• Produce specialized secretions
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Module 4.1: Epithelial tissue
• Basic features of epithelial cells
• Apical surface (faces exterior or internal space)
• Microvilli often found on cells of digestive, urinary, and
reproductive tracts
• Cilia often found on cells lining respiratory and some parts
of reproductive tracts
• Faces lumen (space) when lining hollow organs
• Base (attached to adjacent tissues)
• Basolateral surfaces
• Includes base and lateral surfaces (attached to neighboring
cells)
• Have membranous organelles comparable to other cell types
© 2011 Pearson Education, Inc.
Module 4.1: Epithelial tissue
• Three epithelial cell shapes (perpendicular
section)
1. Squamous (thin and flat)
2. Cuboidal (small boxes)
3. Columnar (slender rectangles)
• Can be layered
•
Single layer (simple epithelium)
•
Several layers (stratified epithelium)
•
Generally located in areas that need protection
© 2011 Pearson Education, Inc.
Module 4.1 Review
a. List four essential functions of epithelial tissue.
b. Summarize the classification of an epithelium
based on cell shape and number of cell layers.
c. What is the probable function of an epithelial
surface whose cells bear many cilia?
© 2011 Pearson Education, Inc.
Module 4.2: Epithelial cells are extensively
interconnected
• Many types of connections to form complete
cover or lining
• Have ability to replace damaged or lost cells
• Lack blood vessels (avascular)
• Lowest cell layers must remain attached to
underlying tissues to be near blood vessels
Animation: Intercellular Connections
© 2011 Pearson Education, Inc.
Microvilli
The structures that connect epithelial cells to
each other and to adjacent tissues
APICAL SURFACE
Intercellular attachments
Occluding junctions form a
barrier that isolates the
basolateral surfaces and deeper
tissues from the contents of the
lumen.
An adhesion belt locks together
the terminal webs of neighboring
cells, strengthening the apical
region and preventing distortion
and leakage at the occluding
junctions.
Gap junctions permit chemical
communication that coordinates
the activities of adjacent cells.
Desmosomes (DEZ-mō-sōms;
desmos, ligament + soma, body)
provide firm attachment between
neighboring cells by interlocking
their cytoskeletons.
BASE
Basal Lamina
Hemidesmosome
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Figure 4.2
1
Module 4.2: Epithelial cells are extensively
interconnected
• Hemidesmosomes
• Made of peripheral and transmembrane proteins
• Attach deepest epithelial cells to basal lamina
• Basal lamina (basement membrane) layers
1. Clear layer (lamina lucida)
•
Contains glycoproteins and fine protein filaments
2. Dense layer (lamina densa)
•
Contains bundles of coarse protein fibers
•
Gives strength and restricts diffusion
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The structures that connect epithelial cells to
each other and to adjacent tissues
Basal Lamina
Intermediate
filaments of the
cytoskeleton
Hemidesmosome
The basal lamina, or basement membrane, is
a complex structure produced by the basal
surface of the epithelium and the underlying
connective tissue.
The clear layer, or lamina lucida (LAM-i-nah
LOO-si-dah; lamina, thin layer + lucida, clear)
contains glycoproteins and a network of fine
protein filaments.
A hemidesmosome, which
attaches the deepest epithelial
cells to the basal lamina
The dense layer, or lamina densa, containing
bundles of coarse protein fibers, gives the
basal lamina its strength and acts as a filter
that restricts diffusion between the adjacent
tissues and the epithelium.
Figure 4.2
© 2011 Pearson Education, Inc.
2
Module 4.2: Epithelial cells are extensively
interconnected
• Types of intercellular attachments
• Occluding junctions
• Form barrier that prevents lumen contents from
getting past cells
• Adjacent plasma membranes tightly bound with
proteins
• Adhesion belt
• Attaches terminal webs of adjacent cells
• Reinforces occluding junctions
• Dense protein band surrounding cell
© 2011 Pearson Education, Inc.
The structures that connect epithelial cells to
each other and to adjacent tissues
At an occluding junction,
the lipid portions of the
two plasma membranes
are tightly bound
together by interlocking
membrane proteins.
An occluding junction
Figure 4.2
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3
The structures that connect epithelial cells
to each other and to adjacent tissues
An adhesion belt
Figure 4.2
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4
Module 4.2: Epithelial cells are extensively
interconnected
• Types of intercellular attachments (continued)
• Gap junctions
• Permit chemical communication to coordinate activities of
adjacent cells
• Formed by interlocking junctional proteins (connexons)
• Examples: ciliated epithelial tissues, cardiac muscle tissue
• Desmosomes (desmos, ligament + soma, body)
• Interlock cytoskeletons of adjacent cells
• Very strong
• Formed by:
• Cell adhesion molecules (CAMs)
• Intercellular cement (thin layer of proteoglycans, notably
hyaluronan)
© 2011 Pearson Education, Inc.
The structures that connect epithelial cells to
each other and to adjacent tissues
Connexons are channel
proteins that form a
narrow passageway and
let small molecules and
ions pass from cell to
cell.
An jap junction
Figure 4.2
© 2011 Pearson Education, Inc.
5
The structures that connect epithelial cells to
each other and to adjacent tissues
Cell adhesion
molecules (CAMs) are
transmembrane proteins
that bind to each other
and to extracellular
materials.
A desmosome
The membranes of
adjacent cells may also
be bonded by
intercellular cement,
a thin layer of
proteoglycans that
contain polysaccharide
derivatives, most notably
hyaluronan.
Figure 4.2
© 2011 Pearson Education, Inc.
6
Module 4.2 Review
a. Identify the various types of epithelial intercellular
connections.
b. How do epithelial tissues, which are avascular,
obtain needed nutrients?
c. What is the functional significance of gap
junctions?
© 2011 Pearson Education, Inc.
Module 4.3: Squamous epithelia
• Simple squamous epithelium (squama, plate or
scale)
• Thin and flat, irregular in shape
• Surface view: like fried eggs side to side
• Sectional view: jigsaw pieces with disc-shaped nucleus
• Found in protected regions
• Where absorption or diffusion takes place
• Examples: along kidney passages, inside eye, alveoli of
the lung
• Where a slippery surface reduces friction
• Lining ventral body cavity (mesothelium)
• Lining heart and blood vessels (endothelium)
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Simple squamous epithelia, which include the specially
named endothelium and mesothelium
Endothelium lining the
inside of the heart and
blood vessels
Mesothelium lining the
pericardial cavity and
the peritoneal cavity
Connective
tissue
Nucleus
Cytoplasm
Sectioned
epithelial cell
The surface
of a simple
squamous
epithelium
Section of
peritoneum
Simple squamous epithelium LM x 270
Figure 4.3
© 2011 Pearson Education, Inc.
1
Module 4.3: Squamous epithelia
• Stratified squamous epithelium
• Located where mechanical or chemical
stresses are severe
• Series of layers
• Example locations: skin, mouth, throat,
esophagus, rectum, anus, vagina
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A stratified squamous epithelium
Squamous
superficial cells
Stem cells
Basal lamina
Connective
tissue
Surface of the tongue
LM x 400
Figure 4.3
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2
Module 4.3: Squamous epithelia
• Stratified squamous epithelium
• Two types
1. Keratinized (with keratin proteins)
•
Tough and water resistant
•
Found at surface of skin
2. Nonkeratinized
•
Resists abrasion but can dry out
•
Found in oral cavity, pharynx, esophagus, anus,
vagina
© 2011 Pearson Education, Inc.
The structure of a keratinized stratified
squamous epithelium
Keratinized skin cells
Keratin fibers
Surface of human skin
Figure 4.3
© 2011 Pearson Education, Inc.
3
Module 4.3 Review
a. What properties are common to keratinized
epithelia?
b. Why do the pharynx, esophagus, anus, and
vagina have a similar epithelial organization?
c. Under a light microscope, simple squamous
epithelium is seen on the outer surface. Could this
be a skin surface sample? Why or why not?
© 2011 Pearson Education, Inc.
Module 4.4: Cuboidal and transitional epithelia
• Cuboidal epithelium
• Cells resemble hexagonal boxes with nucleus in center
• Types
1. Simple cuboidal epithelium
•
Locations
•
Lining exocrine glands and ducts
•
Portions of kidney
•
Secretory chambers of thyroid gland
2. Stratified cuboidal epithelium
•
Rare
•
Locations
•
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Ducts of various exocrine glands
Examples of cuboidal epithelia
Connective
tissue
Basal lamina
Simple
cuboidal cells
Lumen
of duct
Nucleus
A cuboidal epithelium
LM x 1400
The simple cuboidal epithelium in a sectioned
kidney tubule
Lumen
of duct
Stratified
cuboidal cells
Basal
lamina
Nuclei
Connective
tissue
The stratified cuboidal
epithelium in a sweat gland duct
© 2011 Pearson Education, Inc.
LM x 1413
Figure 4.4
1
–
3
Module 4.3: Squamous epithelia
• Transitional epithelium
• Unusual stratified epithelium that stretches and
recoils
• Transitional = changes
• Locations
• Urinary bladder
• Urethra
• Urine-collecting chambers of kidneys
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The transitional epithelium in an empty and a full urinary bladder
Epithelium in a Relaxed Bladder
In an empty urinary bladder,
the superficial cells are
typically plump and cuboidal.
Epithelium
(relaxed)
Basal lamina
Relaxed bladder
Connective tissue and
smooth muscle layers
LM x 400
Figure 4.4
© 2011 Pearson Education, Inc.
4
Module 4.4 Review
a. Identify the epithelium that lines the urinary
bladder and changes in appearance as
stretching occurs.
b. Describe the appearance of simple cuboidal
epithelial cells in sectional view.
c. Stratified cuboidal epithelia are associated
with what epithelial structures?
© 2011 Pearson Education, Inc.
Module 4.5: Columnar epithelia
• Columnar epithelium
• Cells appear rectangular in sectional view
• Elongated nuclei near basal lamina
• Types
1. Simple columnar epithelium
•
Locations
•
Stomach
•
Intestine
•
Uterine tubes
•
Kidney ducts
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The simpler columnar epithelium in the
intestinal lining
Microvilli
Cytoplasm
Nucleus
Basal lamina
Loose connective tissue
LM x 350
Figure 4.5
© 2011 Pearson Education, Inc.
1
Module 4.5: Columnar epithelia
• Columnar epithelium
• Types (continued)
2. Pseudostratified columnar epithelium
•
Varying cell shapes and functions
•
Nuclei located at different areas of cell, so appears
stratified
•
Every cell attached to basal lamina
•
Cells typically possess cilia
•
Locations
•
Nasal cavities
•
Trachea
•
Larger airways of lungs
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The pseudostratified columnar epithelium in the trachea
Cilia
Cytoplasm
Nuclei
Basal
lamina
Loose
connective
tissue
LM x 394
Figure 4.5
© 2011 Pearson Education, Inc.
2
Module 4.5: Columnar epithelia
• Columnar epithelium
• Types (continued)
3. Stratified columnar epithelium
•
Relatively rare
•
Either two or multiple layers
•
•
In multiple layers, only superficial cells are
columns
Located in large ducts of salivary glands and
pancreas
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The stratified columnar epithelium in a salivary gland duct
Loose
connective
tissue
Basal
cells
Lumen
Superficial
columnar cells
Lumen
Cytoplasm
Nuclei
Basal
lamina
LM x 175
Figure 4.5
© 2011 Pearson Education, Inc.
3
Module 4.5 Review
a. Describe the appearance of simple columnar
epithelial cells in a sectional view.
b. Explain why a pseudostratified columnar
epithelium is not truly stratified.
c. The columnar epithelium lining the intestine
typically has ___________ on its apical surface.
© 2011 Pearson Education, Inc.
Module 4.6: Glandular epithelia
• Glands
• Collections of epithelial cells that produce
secretions
• Can be scattered cells or complex organs
• Two types of glandular organs
1. Endocrine glands (secretions into interstitial
fluid)
•
More information in later chapter
2. Exocrine glands (secretions into ducts that
open onto epithelial surface)
© 2011 Pearson Education, Inc.
Module 4.6: Glandular epithelia
• Exocrine glands
• Three types of secretion
1. Merocrine secretion (meros, part)
•
Product released from secretory vesicles by
exocytosis
•
Most common type of secretion
•
Mucin
•
Merocrine secretion that mixes with water to form
mucus
•
Used as lubricant, protective barrier, and trap for
foreign particles and microorganisms
© 2011 Pearson Education, Inc.
Module 4.6: Glandular epithelia
• Exocrine glands
• Three types of secretion (continued)
2. Apocrine secretion (apo-, off)
•
Loss of apical surface and cytoplasm with secretion
•
Example: mammary glands
•
Merocrine and apocrine secretions in milk
3. Holocrine secretion (holos, entire)
•
Entire cell bursts, releasing secretion and killing cell
•
Replaced by stem cell division
Animation: Mechanisms of Glandular Secretion
© 2011 Pearson Education, Inc.
Mucin is a merocrine secretion that
mixes with water to form mucus.
Mucus is an effective lubricant, a
protective barrier, and a sticky trap for
foreign particles and microorganisms.
Secretory vesicle
(containing mucin)
Golgi
apparatus
Nucleus
TEM x 3120
The three types of secretion by
glandular epithelial cells
In merocrine secretion (MER-u-krin; meros, part), the
product is released from secretory vesicles by exocytosis. This
is the most common mode of secretion.
Breaks
down
Regrowth
Salivary gland
Secretion
Golgi apparatus
Mammary
gland
Apocrine secretion (AP-ō-krin; apo-, off) involves the loss of cytoplasm
as well as the secretory product. The apical portion of the cytoplasm
becomes packed with secretory vesicles and is then shed. Milk production
in the mammary glands involves a combination of merocrine and apocrine
secretions.
Cells burst, releasing
cytoplasmic contents.
Hair
Cells produce
secretion, increasing
in size.
Sebaceous gland
Hair follicle
Start
Cell division replaces
lost cells.
Stem cell
Holocrine secretion (HOL-ō-krin; holos, entire), by contrast, destroys
the gland cell. During holocrine secretion, the entire cell becomes packed
with secretory products and then bursts, releasing the secretion and
killing the cell. Further secretion depends on the replacement of destroyed
gland cells by the division of stem cells.
© 2011 Pearson Education, Inc.
Figure 4.6
1
Module 4.6: Glandular epithelia
• Multicellular exocrine gland structure
• Gland classification
• Based on duct structure
•
Simple (single duct that does not divide)
•
Compound (duct divides one or more times)
• Based on structure of secretory area
•
Tubular (glandular cells form tubes)
•
Alveolar or acinar (glandular cells form sacs)
•
Tubuloalveolar (glandular cells form tubes and
sacs)
© 2011 Pearson Education, Inc.
A gland is branched if several secretory areas
(tubular or acinar) share a duct. Note that
“branched” refers to the glandular areas and
not to the duct.
Simple exocrine glands
Duct
Gland
cells
SIMPLE
TUBULAR
Examples:
• Intestinal glands
SIMPLE COILED
TUBULAR
Examples:
• Merocrine sweat
glands
SIMPLE BRANCHED
TUBULAR
Examples:
• Gastric glands
• Mucous glands of
esophagus, tongue,
duodenum
Glands whose glandular cells form tubes are
tubular; the tubes may be straight or coiled.
SIMPLE ALVEOLAR
(ACINAR)
Examples:
• A stage in the embryonic development
of simple branched
glands
SIMPLE BRANCHED
ALVEOLAR
Examples:
• Sebaceous (oil)
glands
Glands whose glandular cells form sac-like
pockets are alveolar (al-VĒ-ō-lar; alveolus,
sac) or acinar (AS-i-nar; acinus, chamber).
Figure 4.6
© 2011 Pearson Education, Inc.
2
Compound exocrine glands
Glands whose secretory
cells form both tubes
and sacs are called
tubuloalveolar.
COMPOUND
TUBULAR
COMPOUND ALVEOLAR
(ACINAR)
COMPOUND
TUBULOALVEOLAR
Examples:
• Mucous glands (in mouth)
• Bulbo-urethral glands (in
male reproductive system)
• Seminiferous tubules of
testes
Examples:
Examples:
• Salivary glands
• Glands of respiratory
passages
• Pancreas
• Mammary glands
Figure 4.6
© 2011 Pearson Education, Inc.
3
Module 4.6: Glandular epithelia
• Unicellular glands
• Individual, scattered secretory cells (mucous
cells)
• Secrete mucin
• Apical cytoplasm filled with large secretory
vesicles
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A mucous cell in a ciliated
columnar epithelium
Mucin
Golgi
apparatus
Nucleus
Mucous cell
Figure 4.6
© 2011 Pearson Education, Inc.
4
Module 4.6 Review
a. Name the two primary types of glands.
b. What mode of secretion occurs in the secretory
cells of sebaceous glands, which fill with
secretions and then rupture, releasing their
contents?
c. Which type of gland has no ducts to carry the
glandular secretions, and the gland’s secretions
are released directly into the interstitial fluid?
© 2011 Pearson Education, Inc.
Section 2: Connective Tissues
• Learning Outcomes
• 4.7 Describe the structure, function, and
locations of areolar connective tissue,
adipose tissue, and reticular tissue.
• 4.8 Describe the structure, function, and
locations of dense connective tissues and
fluid connective tissues.
• 4.9 Describe the structure, function, and
locations of cartilage.
© 2011 Pearson Education, Inc.
Section 2: Connective Tissues
• Learning Outcomes
• 4.10 Describe the structure and function of
bone.
• 4.11 Describe the arrangements of epithelial
and connective tissues in the four types of
membranes.
© 2011 Pearson Education, Inc.
Section 2: Connective Tissues
• Connective tissues
•
•
•
Vary in appearance and function
Throughout body but never exposed to outside
Many have blood vessels and sensory receptors
•
All share three basic components
1. Specialized cells
2. Extracellular protein fibers
3. Fluid (ground substance)
•
Extracellular fibers and fluid make up matrix that
surrounds cells
• Fewer cells and more extracellular material compared to
epithelial cells
© 2011 Pearson Education, Inc.
The three types of connective tissue and
examples of each
Connective Tissue
The various types of connective tissue are situated
throughout the body but they are never exposed to the
outside environment. Many types of connective tissue
are highly vascular (that is, they have many blood
vessels) and contain sensory receptors that detect
pain, pressure, temperature, and other stimuli.
Connective Tissue Proper
Connective tissue proper
includes those connective tissues
with many types of cells and
extracellular fibers in a syrupy
ground substance.
Fluid Connective Tissues
Supporting Connective Tissues
Fluid connective tissues
have distinctive populations of
cells suspended in a watery
matrix that contains dissolved
proteins.
Supporting connective tissues
differ from connective tissue proper
in having a less diverse cell
population and a matrix containing
much more densely packed fibers.
Supporting connective tissues
protect soft tissues and support the
weight of part or all of the body.
Loose
Dense
Blood
Lymph
Cartilage
Bone
Fibers create loose,
open framework
Fibers densely
packed
• dense regular
• dense irregular
• elastic
Flows within
cardiovascular
system
Flows within
lymphatic
system
Solid, rubbery
matrix
Solid, crystalline
matrix
• areolar tissue
• adipose tissue
• reticular tissue
• hyaline cartilage
• elastic cartilage
• fibrous cartilage
Figure 4 Section 2
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Section 2: Connective Tissues
• Connective tissue types
• Connective tissue proper (many types of
cells, fibers with syrupy ground substance)
• Loose (fibers create loose, open framework)
• Dense (fibers densely packed)
• Fluid connective tissues (watery matrix)
• Blood (in cardiovascular system)
• Lymph (in lymphatic system)
© 2011 Pearson Education, Inc.
Section 2: Connective Tissues
• Connective tissue types (continued)
• Supporting connective tissues (less diverse
cells, matrix with densely packed fibers)
• Cartilage (solid, rubbery matrix)
• Bone (solid, crystalline matrix)
© 2011 Pearson Education, Inc.
Figure 4 Section 2
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Module 4.7: Loose connective tissues
• Connective tissue proper components
• Extracellular protein fibers
• Viscous ground substance
• Two classes of cells
1. Fixed
•
Stationary
•
Function in maintenance, repair, and storage
2. Wandering
•
Move throughout tissue
•
Function in defense and repair
© 2011 Pearson Education, Inc.
Module 4.7: Loose connective tissues
• Connective tissue proper components (continued)
• Extracellular protein fibers (continued)
• Reticular fibers (strong and form branching network)
• Collagen fibers (thick, very strong)
• Elastic fibers (slender, very stretchy)
© 2011 Pearson Education, Inc.
Module 4.7: Loose connective tissues
• Connective tissue proper components (continued)
• Ground substance
• Clear
• Colorless
• Viscous (syrupy) due to presence of proteoglycans
and glycoproteins
© 2011 Pearson Education, Inc.
Module 4.7: Loose connective tissues
• Connective tissue proper components (continued)
• Fixed cells
• Melanocytes (synthesize melanin pigment)
• Fixed macrophage (engulfs cell debris and
pathogens)
• Mast cells (stimulate inflammation and mobilize
defenses)
• Fibroblasts (synthesize extracellular fibers)
• Adipocytes (store lipid reserves)
© 2011 Pearson Education, Inc.
Module 4.7: Loose connective tissues
• Connective tissue proper components (continued)
• Wandering cells
• Plasma cells (immune cell producing antibodies)
• Free macrophages (engulf debris and pathogens)
• Mesenchymal cells (stem cells that aid
tissue repair)
• Neutrophils and eosinophils (phagocytic
blood cells)
• Lymphocytes (immune system cells)
© 2011 Pearson Education, Inc.
The components of areola tissue
Fibers
Reticular
fibers are
strong and form
a branching
network.
Collagen fibers are
thick, straight or wavy,
and often form
bundles. They are very
strong and resist
stretching.
Elastic fibers are
slender, unbranching,
and very stretchy.
They recoil to their
original length after
stretching or
distortion.
Fixed Cells
Wandering Cells
A melanocyte is a
fixed pigment cell that
synthesizes melanin, a
brownish-yellow
pigment.
A plasma cell is an
active, mobile immune
cell that produces
antibodies.
A fixed macrophage
is a stationary
phagocytic cell that
engulfs cell debris and
pathogens.
Free macrophages
are wandering
phagocytic cells that
patrol the tissue,
engulfing debris or
pathogens.
Mast cells are fixed
cells that stimulate
local inflammation and
mobilize tissue
defenses.
Mesenchymal cells
are mobile stem cells
that participate in the
repair of damaged
tissues.
Fibroblasts are fixed
cells that synthesize
the extracellular fibers
of the connective
tissue.
Neutrophils and
eosinophils are small,
mobile, phagocytic
blood cells that enter
tissues during infection
or injury.
Adipocytes (fat cells)
are fixed cells that
store lipid reserves in
large intracellular
vesicles.
© 2011 Pearson Education, Inc.
Red blood cell
in vessel
Ground substance fills the spaces between
cells and surrounds connective tissue fibers.
In all forms of connective tissue proper,
ground substance is clear, colorless, and
viscous (syrupy) due to the presence of
proteoglycans and glycoproteins.
Lymphocytes are
mobile cells of the
immune system.
Figure 4.7
1
Module 4.7: Loose connective tissues
• Three types of loose connective tissues
1. Areolar tissue
•
Most common connective tissue proper
•
Packing material of the body
•
Has all connective tissue proper cell types
2. Adipose tissue
•
Found deep to skin in various areas of body
•
Mostly cells (adipocytes)
© 2011 Pearson Education, Inc.
The structure of adipose tissue deep to the skin
Adipocytes
LM x 340
Figure 4.7
© 2011 Pearson Education, Inc.
2
Module 4.7: Loose connective tissues
• Three types of loose connective tissues
(continued)
3. Reticular tissue
•
Found in liver, kidney, spleen, lymph nodes,
and bone marrow
•
Provides support and resists distortion
•
Many reticular fibers forming network (stroma)
© 2011 Pearson Education, Inc.
The structure of reticular tissue in the liver
Reticular
fibers
LM x 375
Figure 4.7
© 2011 Pearson Education, Inc.
3
Module 4.7 Review
a. Identify the types of cells found in connective
tissue proper.
b. Which type of connective tissue contains
primarily lipids?
c. Describe the role of fibroblasts in connective
tissue.
© 2011 Pearson Education, Inc.
Module 4.8: Dense and fluid connective tissues
• Dense connective tissues
• Most volume occupied by extracellular fibers
• Three types
1. Dense regular connective tissue
•
Found in tendons, ligaments, organ cords
•
Has parallel collagen fibers
2. Dense irregular connective tissue
•
Found covering visceral organs; in superficial layers of
bones, cartilages, and peripheral nerves; in dermis
•
No consistent pattern of fiber arrangement
© 2011 Pearson Education, Inc.
Module 4.8: Dense and fluid connective tissues
• Dense connective tissues (continued)
• Three types (continued)
3. Elastic tissue
•
More elastic fibers than collagen
•
Is springy and resilient
•
Found between vertebrae, in walls of large blood
vessels, erectile tissues of penis
© 2011 Pearson Education, Inc.
The three types of dense connective tissues
Collagen
fiber
Fibroblast
nuclei
LM x 440
Dense regular connective tissue in a tendon from the triceps muscle
Collagen
fiber
bundles
LM x 111
Dense irregular connective tissue from the dermis
Elastic
fibers
Fibroblast
nuclei
LM x 887
Elastic tissue from a ligament between vertebrae
© 2011 Pearson Education, Inc.
Figure 4.8
1
–
3
Module 4.8: Dense and fluid connective tissues
• Fluid connective tissues
• Fluid matrix with many suspended proteins
• Normally without fibers
• Types
1. Blood
•
Components
•
Watery matrix (plasma)
•
Cells and cell fragments (formed elements)
2. Lymph
•
Components
•
Watery matrix (lymph)
•
Cells (mainly lymphocytes)
© 2011 Pearson Education, Inc.
Module 4.8: Dense and fluid connective tissues
• Formed elements of blood
•
Red blood cells (transport oxygen)
•
White blood cells (bodily defense)
•
•
Monocytes (large phagocytes)
•
Lymphocytes (uncommon in blood)
•
Eosinophils/neutrophils (small phagocytes)
•
Basophils (promote inflammation)
Platelets (involved in clotting response)
© 2011 Pearson Education, Inc.
Module 4.8: Dense and fluid connective tissues
• Fluid connective tissue locations and functions
•
Blood
•
•
Normally moved by heart through blood
vessels
•
Arteries (away from heart)
•
Capillaries (smallest vessels; sites of exchange)
•
Veins (toward heart)
Exchanges water and solutes between plasma
and interstitial fluid
© 2011 Pearson Education, Inc.
The formed elements in blood, a fluid connective tissue with a watery matrix called plasma
Red Blood Cells
White Blood Cells
Platelets
Red blood cells are
formed elements
responsible for the
transport of oxygen
(and, to a lesser
degree, of carbon
dioxide) in the blood.
White blood cells are formed elements
that help defend the body from infection
and disease.
Platelets are
formed elements
consisting of
membrane-enclosed
packets of
cytoplasm.
Red blood cells
account for roughly
half the volume of
whole blood and
give blood its color.
Monocytes
are phagocytes
similar to the
free macrophages in
other tissues.
Eosinophil
Lymphocytes are
uncommon in the
blood but they are the
dominant cell type in
lymph, the second
type of fluid
connective tissue.
Neutrophil
Basophil
Eosinophils and
neutrophils are
phagocytes. Basophils
promote inflammation
much like mast cells in
other connective tissues.
These cell
fragments are
involved in the
clotting response
that seals leaks in
damaged or broken
blood vessels.
Figure 4.8
© 2011 Pearson Education, Inc.
4
Module 4.8: Dense and fluid connective tissues
• Fluid connective tissue locations and functions
(continued)
•
Lymph
•
Located in lymphatic vessels
•
Collected from interstitial fluid
•
Returned to blood at large veins near heart
•
Functions to maintain solute levels, blood
volume, and alert immune system of infection
© 2011 Pearson Education, Inc.
Capillaries are the smallest and most
delicate blood vessels. All exchange
between the blood and interstitial fluid
occurs at capillaries.
Start
Arteries carry blood
away from the heart and
into the tissues of the
body.
Heart
Water and
solutes from
bloodstream
At capillary networks, blood
pressure forces water and small
solutes out of the bloodstream
and into the surrounding
interstitial fluid.
Lymph forms as interstitial fluid
enters lymphatic vessels.
Veins carry blood from
capillary beds to the
heart.
Lymphatic vessels form a
network that returns lymph to
large veins near the heart.
The continuous circulation of extracellular fluid, including the fluid connective tissue called lymph
Figure 4.8
© 2011 Pearson Education, Inc.
5
Module 4.8 Review
a. Which two types of connective tissue have a
liquid matrix?
b. Lack of vitamin C in the diet interferes with
the ability of fibroblasts to produce collagen.
How might this affect connective tissue
function?
c. Summarize the role of extracellular fluid in
maintaining homeostasis.
© 2011 Pearson Education, Inc.
Module 4.9: Cartilage
• Cartilage
• Matrix is firm gel containing polysaccharide
derivatives (chondroitin sulfates [chondros,
cartilage])
• Forms complexes with proteins producing
proteoglycans
• Cells (chondrocytes)
• Only cells in cartilage matrix
• Occupy small chambers (lacunae [lacus, lake])
© 2011 Pearson Education, Inc.
Module 4.9: Cartilage
• Cartilage properties
• Depend on matrix proteoglycans as well as type and
abundance of extracellular fibers
• Set apart from surrounding tissues by perichondrium
(peri-, around)
• Two layers of perichondrium
1. Outer layer of dense regular connective tissue
•
Mechanical support, protection, attachment
2. Inner cellular layer
•
© 2011 Pearson Education, Inc.
Where cartilage growth and maintenance occur
The perichondrium, which separates
cartilage from surrounding tissues
Perichondrium
Hyaline cartilage LM x 250
Figure 4.9
© 2011 Pearson Education, Inc.
4
Module 4.9: Cartilage
• Three types
1. Hyaline cartilage
•
Found between ribs and sternum, covering
bones in mobile joints, certain areas of
respiratory system
•
Stiff but flexible support and reduces friction
2. Elastic cartilage
•
Supports external ear and other smaller internal
structures
•
Increased flexibility
© 2011 Pearson Education, Inc.
Module 4.9: Cartilage
• Three types (continued)
3. Fibrous cartilage
•
Found within knee joint, between pubic bones
of pelvis, in intervertebral discs
•
Resists compression, prevents bone-to-bone
contact, and limits relative movement
© 2011 Pearson Education, Inc.
The three types of cartilage
Chondrocytes
in lacunae
Matrix
LM x 500
Hyaline cartilage from shoulder joint
Chondrocyte
in lacuna
Elastic fibers
in matrix
LM x 358
Elastic cartilage from external ear
Collagen
fibers in
matrix
Chondrocytes
LM x 400
Fibrous cartilage from intervertebral disc
© 2011 Pearson Education, Inc.
Figure 4.9
1
–
3
Module 4.9: Cartilage
• Cartilage growth
•
Two types
1. Appositional growth (at cartilage surface)
•
Chondroblasts (immature chondrocytes) divide
in cellular layer of perichondrium
•
Chondroblasts secrete new matrix
•
Once surrounded by matrix, chondroblasts
mature into chondrocytes
© 2011 Pearson Education, Inc.
Module 4.9: Cartilage
• Cartilage growth
•
Two types (continued)
2. Interstitial growth (within cartilage)
•
Chondrocytes divide within a lacuna
•
Daughter cells secrete additional matrix and move
apart
•
Both types occur during development
•
Normally no growth and repair in adults
•
With slight damage or with hormonal
stimulation, some appositional growth possible
© 2011 Pearson Education, Inc.
The types of cartilage growth
Appositional Growth
Fibroblasts
Dividing stem cell
Perichondrium
New matrix
Chondroblasts
Mature
chondrocytes
Older matrix
In appositional
growth, the
cartilage enlarges
by the addition of
cartilage to the
outer surface.
Cells in the cellular
layer of the
perichondrium
differentiate into
chrondroblasts (immature chrondrocytes).
The chondroblasts
secrete new matrix
and become
separated from each
other.
Divisions of stem cells in the
perichondrium continuously
produce additional
chondroblasts. Meanwhile,
chondroblasts completely
surrounded by matrix gradually
mature into chondrocytes.
Interstitial Growth
New
matrix
Matrix
Chondrocyte
Lacuna
In interstitial
growth, the
cartilage
expands from
within.
A chondrocyte undergoes
division within a lacuna
surrounded by cartilage
matrix.
As daughter cells secret additional
matrix, they move apart, expanding
the cartilage from within.
Figure 4.9
© 2011 Pearson Education, Inc.
5
Module 4.9 Review
a. Mature cartilage cells are called __________.
b. Which connective tissue fiber is characteristic
of the cartilage supporting the ear?
c. If a person has a herniated intervertebral disc,
which type of cartilage has been damaged?
© 2011 Pearson Education, Inc.
Module 4.10: Bone
• Osseous tissue (os, bone) structure
• Bony matrix
• Small volume of ground substance
• 2/3 of matrix is calcium salts (provide strength)
• Mostly calcium phosphate
• Some calcium carbonate
• Many collagen fibers (provide flexibility)
© 2011 Pearson Education, Inc.
Module 4.10: Bone
• Comparison of cartilage and bone
• Both support and protect
• Cartilage is avascular; bone is highly vascular
• Cartilage cannot grow/repair; extensive
remodeling and repair in bone
© 2011 Pearson Education, Inc.
Figure 4.10
© 2011 Pearson Education, Inc.
2
Module 4.10: Bone
• Typical long bone structure
• Hollow with two types of bone
1. Spongy bone
•
Lines internal cavity
2. Compact bone
•
Outer layer of bone
© 2011 Pearson Education, Inc.
The structure of a long bone, which consists
of compact bone and spongy bone
In compact bone the matrix is
organized in concentric layers
around branches of blood
vessels within the bone.
Compact
bone
Compact bone also has a
superficial layer of bone that
was deposited during
appositional growth of the
bone. Because the matrix is
solid and calcified, interstitial
growth cannot occur in bone.
Unlike cartilage, bone
is highly vascular.
Large vessels
outside the bone are
connected to smaller
vessels that supply
areas of compact
bone and the soft
tissues that fill the
interior cavity.
Spongy
bone
Figure 4.10
© 2011 Pearson Education, Inc.
1
Module 4.10: Bone
• Compact bone structure
•
Matrix organized in concentric layers
•
Organized into functional units (osteons)
•
Central canal contains blood vessels in center
•
Cells (osteocytes) located between layers
•
Canaliculi (little canals) connect osteocytes
•
Superficial layer of bone prevents interstitial
growth
© 2011 Pearson Education, Inc.
Module 4.10: Bone
• Compact bone structure (continued)
•
Surrounded by periosteum
•
Two layers
1. Outer fibrous layer allows attachment of ligaments
2. Inner cellular layer allows appositional growth and
repair
© 2011 Pearson Education, Inc.
The structural features of compact bone, including its
functional unit, the osteon
Layers of the Periosteum
The fibrous layer assists in the attachment
of a bone to surrounding tissues and to
associated tendons and ligaments.
Except in joint cavities, where they are covered by a
layer of hyaline cartilage, bone surfaces are sheathed
by a periosteum (per-ē-OS-tē-um) composed of
fibrous (outer) and cellular (inner) layers.
The cellular layer functions in
appositional bone growth and participates
in repairs after an injury.
Lacunae in the matrix contain
osteocytes (OS-tē- ō-sīts), or bone cells.
The lacunae are typically organized
around blood vessels that branch
through the bony matrix.
Layers of matrix separate the lacunae.
These layers are oriented along the main
axis of the bone.
Canaliculi (kan-a- LIK-ū-lē; little canals)
are fine passageways that form a
branching network for the exchange of
materials between blood vessels and
osteocytes. This is important because
diffusion cannot occur through the
calcified matrix of bone.
A central canal at the center of an
osteon contains the blood vessels that
provide oxygen and nutrients to the
osteocytes.
Matrix
Osteon
Lacunae
Canaliculi
LM x 320
Figure 4.10
© 2011 Pearson Education, Inc.
3 –
4
Module 4.10 Review
a. Mature bone cells in lacunae are called
____________.
b. Distinguish between the two types of supporting
connective tissues with respect to their
characteristic fibers.
c. Explain why bone does not undergo interstitial
growth.
© 2011 Pearson Education, Inc.
Module 4.11: Membranes and fasciae
• Membranes
• Line or cover body surfaces
• Consist of epithelium supported by connective
tissue
• Four types
1. Mucous membranes
•
Line organs that communicate to exterior
•
Must be kept moist to facilitate movement, absorption, or
secretion
•
•
Lubricated by mucus or bodily fluids
Supported by areolar connective tissue (lamina propria)
© 2011 Pearson Education, Inc.
Module 4.11: Membranes and fasciae
• Membranes (continued)
• Four types (continued)
2. Serous membranes
•
Mesothelium supported by areolar connective tissue
•
Delicate and never connected to exterior
•
Transudate (liquid layer) coats surface
•
Three line subdivisions of ventral body cavity
•
Pleura (pleural cavity and lungs)
•
Peritoneum (peritoneal cavity and visceral organs)
•
Pericardium (pericardial cavity and heart)
© 2011 Pearson Education, Inc.
Module 4.11: Membranes and fasciae
• Membranes (continued)
• Four types (continued)
3. Cutaneous membrane
•
Covers surface of body
•
= Skin
•
Relatively thick, waterproof, and dry comparatively
© 2011 Pearson Education, Inc.
Module 4.11: Membranes and fasciae
• Membranes (continued)
• Four types (continued)
4. Synovial membranes
•
Line mobile joint cavities
•
Similar to epithelia but not
•
Develops within connective tissue
•
No basal lamina
•
Gaps between cells (up to 1 mm)
•
Exchange fluid (synovial fluid) and solutes with
cardiovascular capillaries
© 2011 Pearson Education, Inc.
Module 4.11: Membranes and fasciae
• Fasciae
• Connective tissue layers and wrappings
• Support and surround organs
• Three types
1. Superficial fascia
•
Under skin
•
Consists of areolar and adipose tissue
2. Deep fascia
•
Continuous with capsules, ligaments, and other
connective tissue structures
•
Consists of dense irregular connective tissue
© 2011 Pearson Education, Inc.
Module 4.11: Membranes and fasciae
• Fasciae (continued)
• Three types (continued)
3. Subserous fascia
•
Between serous membranes and deep fascia
•
Consists entirely of areolar tissue
© 2011 Pearson Education, Inc.
Connective Tissue Framework of Body
Body wall
Body
cavity
Skin
The Superficial
Fascia
The Deep
Fascia
The Subserous
Fascia
• Lies between the
skin and
underlying organs
• Forms a strong,
fibrous internal
framework
• Lies between
serous
membranes and
deep fascia
• Consists of
areolar tissue and
adipose tissue
• Consists of dense
irregular
connective tissue
• Consists entirely
of areolar tissue
• Is continuous
with or bound to
capsules,
ligaments, and
other connective
tissue structures
Serous membrane lining body cavity
Rib
Cutaneous membrane of the skin
The structure and function of fasciae
Figure 4.11
© 2011 Pearson Education, Inc.
1
Module 4.11 Review
a. Name the four types of membranes found in the
body.
b. Which cavities in the body are lined by serous
membranes?
c. A sheet of tissue has many layers of collagen
fibers that run in different directions in successive
layers. Which type of tissue is this?
© 2011 Pearson Education, Inc.
Section 3: Muscle Tissue and Neural Tissue
• Learning Outcomes
• 4.12 Specify the functions of muscle tissue and
neural tissue.
• 4.13 CLINICAL MODULE Describe the roles of
inflammation and regeneration in
response to tissue injury.
© 2011 Pearson Education, Inc.
Section 3: Muscle Tissue and Neural Tissue
• Muscle and neural tissue contribute
significantly to various systems in the body
• These two tissue types contribute the most
(muscle) and least (neural) to body weight
© 2011 Pearson Education, Inc.
Epithelial tissue
3%
Connective tissue 45%
Neural tissue 2%
Muscle tissue
50%
The relative
contributions of muscle
tissue and neural tissue to
the weight of the body
The three types of muscle tissue
Muscle Tissue
Skeletal Muscle Tissue
Cardiac Muscle Tissue
Smooth Muscle Tissue
Skeletal muscle tissue
moves the body by pulling
on bones of the skeleton,
making it possible for us
to walk, dance, bite an
apple, or play the ukulele.
Cardiac muscle tissue
contractions move blood
through the blood
vessels.
Smooth muscle tissue
contractions move fluids and
solids along the digestive
tract and regulate the
diameters of small arteries,
among other functions.
Figure 4 Section 3
© 2011 Pearson Education, Inc.
Module 4.12: Muscle tissue for contraction and
neural tissue for communication
• Muscle tissue
• All functions involve movement
• Movement of body
• Movement of blood around cardiovascular
system
• Movement of materials along digestive tract
• Three types
1. Skeletal muscle tissue
2. Cardiac muscle tissue
3. Smooth muscle tissue
© 2011 Pearson Education, Inc.
Module 4.12: Muscle tissue for contraction and
neural tissue for communication
• Muscle tissue
• Three types
1. Skeletal muscle tissue
•
Found in skeletal muscle
•
Cells are long, cylindrical, banded (striated), and have
multiple nuclei (multinucleate)
•
Functions
•
Move skeleton
•
Guard organ entrances for digestive, respiratory,
and urinary system
•
Generate heat
•
Protect internal organs
© 2011 Pearson Education, Inc.
Module 4.12: Muscle tissue for contraction and
neural tissue for communication
• Muscle tissue (continued)
• Three types (continued)
2. Cardiac muscle tissue
•
Found only in heart
•
Cells are short, branched, and have a single nucleus
•
•
Interconnected with special junctions
(intercalated discs)
Functions to move blood and maintain blood
pressure
© 2011 Pearson Education, Inc.
Module 4.12: Muscle tissue for contraction and
neural tissue for communication
• Muscle tissue (continued)
• Three types (continued)
3. Smooth muscle tissue
•
Found throughout body (skin, blood vessel walls, many
organs of various systems)
•
Cells are short, spindle-shaped, nonstriated, have a single
nucleus
•
Functions
•
Move food, urine, and reproductive secretions
•
Control diameter of respiratory passageways and
blood vessels
© 2011 Pearson Education, Inc.
The structure and function of the three types of muscle tissue
Nuclei
Muscle
fiber
Striations
LM x 180
Skeletal muscles move or stabilize the position of the skeleton;
guard entrances and exits to the digestive, respiratory, and
urinary tracts; generate heat; and protect internal organs.
Nucleus
Cardiac
muscle cells
Intercalated
discs
Striations
LM x 450
Cardiac muscle moves blood and maintains blood
pressure.
Smooth
muscle cell
Nucleus
LM x 235
Smooth muscle moves food, urine, and reproductive tract secretions;
controls diameter of respiratory passageways and regulates diameter of
blood vessels.
© 2011 Pearson Education, Inc.
Figure 4.12
1
-
3
Module 4.12: Muscle tissue for contraction and
neural tissue for communication
• Neural tissue (nervous tissue)
• Specialized for conduction of electrical impulses
• 98% found in brain and spinal cord
• Two basic types of cells
1. Neurons (neuros, nerve)
2. Neuroglia or glial cells (glia, glue)
•
Various supporting cells
© 2011 Pearson Education, Inc.
Module 4.12: Muscle tissue for contraction and
neural tissue for communication
• Neurons
• Transfer information around body and perform
information processing
• = Conscious and unconscious thought in the
brain
• Vary in size and shape
• Longest cells in body are neurons (up to 1
meter)
© 2011 Pearson Education, Inc.
Module 4.12: Muscle tissue for contraction and
neural tissue for communication
• Neuron structure
• Dendrites (dendron, tree)
• Receive information
• Axon
• Conducts information to other cells
• Also called nerve fibers
• Cell body
• Contains large nucleus and other organelles
• Cell control center and site of information processing
• Most lack centrioles and cannot divide
© 2011 Pearson Education, Inc.
The shapes of different
types of neuroglia
Figure 4.12
© 2011 Pearson Education, Inc.
5
Module 4.12: Muscle tissue for contraction and
neural tissue for communication
• Neuroglia
• Several different structural types with
associated functions
• Maintain physical structure of neural tissue
• Repair neural tissue framework after injury
• Perform phagocytosis
• Provide nutrients to neurons
• Regulate the composition of the interstitial fluid
surrounding neurons
© 2011 Pearson Education, Inc.
Module 4.12 Review
a. Identify the three types of muscle tissue in the
body.
b. Which type of muscle tissue has small,
tapering cells with single nuclei and no
obvious striations?
c. Irregularly shaped cells with many fibrous
projections, some several centimeters long,
are probably which type of cell?
© 2011 Pearson Education, Inc.
Module 4.13 CLINICAL MODULE: Response to
injury
• Organs are comprised of different tissue types
• Damage to an organ affects many tissues
• Tissues respond in a coordinated way to restore
homeostasis
• Each tissue has a different ability to regenerate
• Epithelial, connective (except cartilage), and
smooth muscle regenerate well
• Other muscle types and neural tissue regenerate
poorly, if at all
• Scar tissue replaces tissues that do not regenerate
(= fibrosis)
© 2011 Pearson Education, Inc.
Module 4.13 CLINICAL MODULE: Response to
injury
• Injury
• Exposure to pathogens and toxins (infection)
• Stimulates mast cell activation, which causes inflammation
• Inflammation
• Familiar symptoms of swelling, redness, warmth, and
pain
• Occurs in connective tissue
• So can occur anywhere in body because part of all
organs
• Leads to increased oxygen/nutrients, phagocytosis,
and removal of toxins and wastes
© 2011 Pearson Education, Inc.
Module 4.13 CLINICAL MODULE: Response to
injury
• Regeneration
• Repair after tissue stabilized and inflammation ends
• Fibroblasts secrete collagen fibers to stabilize area (=
scar tissue)
• Gradually remodeled or replaced
• Normal conditions restored
© 2011 Pearson Education, Inc.
Inflammation
The events that occur during tissue injury and repair
Injury
When a tissue is injured, a general
defense mechanism is activated.
Exposure to Pathogens and Toxins
Mast Cell Activation
An injured tissue contains an
abnormal concentration of
pathogens, toxins, waste
products, and the chemicals
from injured cells.
When an injury damages
connective tissue, mast
cells release a variety of
chemicals. This process,
called mast cell activation,
stimulates inflammation.
stimulates
Histamine
Mast cell
Heparin
Prostaglandins
Figure 4.13
© 2011 Pearson Education, Inc.
1
Injury
Mast Cell Activation
Regeneration, the repair to the injured tissue
once inflammation has subsided.
Regeneration inhibits mast cell activation
Regeneration
Normal
tissue
conditions
restored
As tissue conditions return to normal,
fibroblasts move into the area, laying
down a network of collagen fibers that
stabilizes the injury site. This process
produces a dense, collagenous
framework known as scar tissue. Over
time, scar tissue is usually “remodeled”
and gradually assumes a more normal
appearance.
Over a period of hours to
days, the cleanup process
generally succeeds in
eliminating the inflammatory stimuli.
Inflammation
Scar
tissue
Figure 4.13
© 2011 Pearson Education, Inc.
3
Module 4.13 CLINICAL MODULE: Review
a. Identify the two processes in the response to
tissue injury.
b. What are the four indications of inflammation
that occur following an injury?
c. Why can inflammation occur in any organ in
the body?
© 2011 Pearson Education, Inc.