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Body Tissues
Levels of Structural Organization
• Chemical – atoms combined to form
molecules
• Cellular – cells are made of molecules
• Tissue – consists of similar types of cells
• Organ – made up of different types of
tissues
• Organ system – consists of different
organs that work closely together
• Organismal – made up of the organ
systems
Levels of Structural Organization
Smooth muscle cell
Molecules
2 Cellular level
Cells are made up of
molecules.
Atoms
1 Chemical level
Atoms combine to
form molecules.
3 Tissue level
Tissues consist of
similar types of cells.
Smooth
muscle
tissue
Heart
Cardiovascular
system
Blood
vessels
Epithelial
tissue
Smooth
muscle
tissue
Connective
tissue
4 Organ level
Organs are made up
of different types
of tissues.
Blood
vessel
(organ)
6 Organismal level
The human organism
is made up of many
organ systems.
5 Organ system level
Organ systems consist of
different organs that
work together closely.
Figure 1.1
Levels of Structural Organization
Molecules
Atoms
1 Chemical level
Atoms combine to
form molecules.
Figure 1.1
Levels of Structural Organization
Smooth muscle cell
2 Cellular level
Cells are made up of
molecules.
Molecules
Atoms
1 Chemical level
Atoms combine to
form molecules.
Figure 1.1
Levels of Structural Organization
Smooth muscle cell
Molecules
2 Cellular level
Cells are made up of
molecules.
Atoms
1 Chemical level
Atoms combine to
form molecules.
3 Tissue level
Tissues consist of
similar types of cells.
Smooth
muscle
tissue
Figure 1.1
Levels of Structural Organization
Smooth muscle cell
Molecules
2 Cellular level
Cells are made up of
molecules.
Atoms
1 Chemical level
Atoms combine to
form molecules.
3 Tissue level
Tissues consist of
similar types of cells.
Smooth
muscle
tissue
Epithelial
tissue
Smooth
muscle
tissue
Connective
tissue
Blood
vessel
(organ)
4 Organ level
Organs are made up
of different types
of tissues.
Figure 1.1
Levels of Structural Organization
Smooth muscle cell
Molecules
2 Cellular level
Cells are made up of
molecules.
Atoms
1 Chemical level
Atoms combine to
form molecules.
3 Tissue level
Tissues consist of
similar types of cells.
Smooth
muscle
tissue
Heart
Cardiovascular
system
Blood
vessels
Epithelial
tissue
Smooth
muscle
tissue
Connective
tissue
4 Organ level
Organs are made up
of different types
of tissues.
Blood
vessel
(organ)
5 Organ system level
Organ systems consist of
different organs that
work together closely.
Figure 1.1
Levels of Structural Organization
Smooth muscle cell
Molecules
2 Cellular level
Cells are made up of
molecules.
Atoms
1 Chemical level
Atoms combine to
form molecules.
3 Tissue level
Tissues consist of
similar types of cells.
Smooth
muscle
tissue
Heart
Cardiovascular
system
Blood
vessels
Epithelial
tissue
Smooth
muscle
tissue
Connective
tissue
4 Organ level
Organs are made up
of different types
of tissues.
Blood
vessel
(organ)
6 Organismal level
The human organism
is made up of many
organ systems.
5 Organ system level
Organ systems consist of
different organs that
work together closely.
Figure 1.1
Body Tissues
• Tissues
– Groups of cells with similar structure and
function
– Four primary types
•
•
•
•
Epithelial tissue (epithelium)
Connective tissue
Muscle tissue
Nervous tissue
4-1 Four Types of Tissue
• Epithelial Tissue
– Covers exposed surfaces
– Lines internal passageways
– Forms glands
• Connective Tissue
– Fills internal spaces
– Supports other tissues
– Transports materials
– Stores energy
4-1 Four Types of Tissue
• Muscle Tissue
– Specialized for contraction
– Skeletal muscle, heart muscle, and walls of
hollow organs
• Neural Tissue
– Carries electrical signals from one part of the
body to another
Epithelial Tissues
• Locations
– Body coverings
– Body linings
– Glandular tissue
• Functions
– Protection
– Absorption
– Filtration
– Secretion
– Sensation
Epithelium Characteristics
• Cells fit closely together and
often form sheets (cell junctions)
• The apical surface is the free
surface of the tissue
• The lower surface of the
epithelium rests on a basement
membrane (basal lamina)
• Avascular (no blood supply)
• Regenerate easily if well
nourished
Cell Junctions
• Tight junctions
– So close that are
sometimes impermeable
• Adherens junctions
– Transmembrane linker
proteins
• Desmosomes
– Anchoring junctions
– Filaments anchor to the
opposite side
• Gap junctions
– Allow small molecules to
move between cells
Figure 4-2a Cell Junctions
Tight junction
Adhesion belt
Terminal web
Spot
desmosome
Gap
junctions
Hemidesmosome
This is a diagrammatic view of an epithelial cell,
showing the major types of intercellular
connections.
Figure 4-2b Cell Junctions
Interlocking
junctional
proteins
Tight junction
Terminal web
Adhesion belt
A tight junction is formed by the fusion of
the outer layers of two plasma
membranes. Tight junctions prevent the
diffusion of fluids and solutes between
the cells. A continuous adhesion belt lies
deep to the tight junction. This belt is tied
to the microfilaments of the terminal web.
Figure 4-2c Cell Junctions
Embedded proteins
(connexons)
Gap junctions permit the
free diffusion of ions and
small molecules between
two cells.
Figure 4-2d Cell Junctions
Intermediate
filaments
Cell adhesion
molecules (CAMs)
Dense area
Proteoglycans
A spot desmosome ties
adjacent cells together.
Figure 4-2e Cell Junctions
Clear
layer
Dense
layer
Hemidesmosomes attach a
cell to extracellular structures,
such as the protein fibers in
the basement membrane.
Basement
membrane
Classification of Epithelia
• Number of cell
layers
– Simple—one layer
– Stratified—more
than one layer
Figure 3.17a
Classification of Epithelia
• Shape of cells
– Squamous
• flattened
– Cuboidal
• cube-shaped
– Columnar
• column-like
Figure 3.17b
Simple Epithelia
• Simple squamous
– Single layer of flat
cells
– Functions in
Absorption and
diffusion
– Usually forms
membranes
• Lines body
cavities
(Mesothelium)
• Lines hearts and
capillaries
(Endothelium)
Lining of Artery
Figure 4-3a Squamous Epithelia
Simple Squamous Epithelium
LOCATIONS: Mesothelia lining ventral body cavities; endothelia lining heart
and blood vessels; portions of kidney tubules (thin sections of nephron loops);
inner lining of cornea; alveoli of lungs
FUNCTIONS: Reduces friction; controls vessel permeability; performs
absorption and secretion
Cytoplasm
Nucleus
Connective tissue
Lining of peritoneal cavity
LM  238
Simple Epithelia
• Simple cuboidal
– Single layer of
cube-like cells
– Common in
glands and
their ducts
– Forms walls of
kidney tubules
– Covers the
ovaries
– Functions in
secretion and
absorption
Figure 4-4a Cuboidal and Transitional Epithelia
Simple Cuboidal Epithelium
LOCATIONS: Glands; ducts;
portions of kidney tubules; thyroid
gland
Connective
tissue
FUNCTIONS: Limited protection,
secretion, absorption
Nucleus
Cuboidal
cells
Basement
membrane
Kidney tubule
LM  650
Simple Epithelia
• Simple
columnar
– Single layer
of tall cells
– Often
includes
mucusproducing
goblet cells
– Lines
digestive tract
– Functions in
absorption
and secretion
Figure 4-5a Columnar Epithelia
Simple Columnar Epithelium
LOCATIONS: Lining of
stomach, intestine, gallbladder,
uterine tubes, and collecting
ducts of kidneys
FUNCTIONS: Protection,
secretion, absorption
Microvilli
Cytoplasm
Nucleus
Intestinal lining
Basement
membrane
Loose
connective tissue
LM  350
Simple Epithelia
•
Pseudostratified columnar
– Single layer, but some cells
are shorter than others
– Often looks like a double layer
of cells
– Sometimes ciliated, such as in
the respiratory tract
– May function in absorption or
secretion
– Cilia movement
Figure 4-5b Columnar Epithelia
Pseudostratified Ciliated Columnar Epithelium
LOCATIONS: Lining of
nasal cavity, trachea, and
bronchi; portions of male
reproductive tract
Cilia
Cytoplasm
FUNCTIONS: Protection,
secretion, move mucus
with cilia
Nuclei
Basement
membrane
Trachea
Loose
connective tissue
LM  350
Table 4-1 Classifying Epithelia
Stratified Epithelia
• Stratified squamous
– Cells at the apical
surface are flattened
– Found as a
protective covering
where friction is
common
– Locations
• Skin
• Mouth
• Esophagus
Protects against attacks
Keratin protein adds strength and water
resistance
Figure 4-3b Squamous Epithelia
Stratified Squamous Epithelium
LOCATIONS: Surface of skin; lining of mouth, throat, esophagus, rectum,
anus, and vagina
FUNCTIONS: Provides physical protection against abrasion, pathogens,
and chemical attack
Squamous
superficial cells
Stem cells
Basement
membrane
Connective
tissue
Surface of tongue
LM  310
Stratified Epithelia
• Stratified cuboidal—two layers of cuboidal
cells
- Found in sweat ducts and mammary
glands
– Rare in human body
– Found mainly in ducts of large glands
LOCATIONS: Lining of some ducts
(rare)
FUNCTIONS: Protection, secretion,
absorption
Lumen
of duct
Stratified
cuboidal
cells
Basement
membrane
Nuclei
Connective
tissue
Stratified Epithelia
• Stratified columnar—surface cells are
columnar, cells underneath vary in size
and shape
– Rare in human body
– Found mainly in ducts of large glands
Stratified Columnar Epithelium
LOCATIONS: Small areas of
the pharynx, epiglottis, anus,
mammary glands, salivary
gland ducts, and urethra
FUNCTION: Protection
Loose
connective tissue
Deeper basal
cells
Superficial
columnar cells
Cytoplasm
Nuclei
Basement
membrane
Stratified Epithelia
• Transitional
epithelium
– Shape of cells
depends upon the
amount of stretching
– Lines organs of the
urinary system
Tolerates repeated cycles of stretching
and recoiling and returns to its
previous shape without damage
Figure 4-4c Cuboidal and Transitional Epithelia
Transitional Epithelium
LOCATIONS: Urinary
bladder; renal pelvis;
ureters
FUNCTIONS: Permits
expansion and recoil
after stretching
Epithelium
(relaxed)
Basement membrane
Empty bladder
Connective tissue and
smooth muscle layers
LM  400
Epithelium
(stretched)
Full bladder
Urinary bladder
Basement membrane
Connective tissue and
smooth muscle layers
LM  400
LM  400
Pap Smear (Papanicolaou Test)
• Involves
examining
cells from
the
stratified
squamous
epithelium
Glandular Epithelium
• Gland
– One or more cells responsible for secreting a particular product
• Two major gland types
– Endocrine gland
• Ductless since secretions diffuse into blood vessels (interstitial
fluid)
• All secretions are hormones
• RELEASE hormones
– Exocrine gland
• Secretions empty through ducts to the epithelial surface
• Include sweat and oil glands
• PRODUCE hormones
Classification of glands
• By where they release their product
– Exocrine: external secretion onto body
surfaces (skin) or into body cavities
– Endocrine: secrete messenger molecules
(hormones) which are carried by blood to
target organs; “ductless” glands
• By whether they are unicellular or
multicellular
Exocrine glands
unicellular or multicellular
Unicellular: goblet cell
scattered within epithelial
lining of intestines and
respiratory tubes
Product: mucin
mucus is mucin & water
Multicellular exocrine glands
Gland Structure
• Multicellular glands
1. Structure of the duct
» Simple (undivided)
» Compound (divided)
2. Shape of secretory portion of
the gland
» Tubular (tube shaped)
» Alveolar or acinar (blind
pockets)
3. Relationship between ducts
and glandular areas
» Branched (several secretory
areas sharing one duct)
Figure 4-7 A Structural Classification of Exocrine Glands
SIMPLE GLANDS
Duct
Gland
cells
SIMPLE
TUBULAR
Examples:
• Intestinal glands
SIMPLE COILED
TUBULAR
Examples:
• Merocrine sweat
glands
SIMPLE ALVEOLAR
(ACINAR)
Examples:
• Not found in adult; a
stage in development
of simple branched
glands
SIMPLE BRANCHED
TUBULAR
Examples:
• Gastric glands
• Mucous glands
of esophagus,
tongue, duodenum
SIMPLE BRANCHED
ALVEOLAR
Examples:
• Sebaceous (oil)
glands
Figure 4-7 A Structural Classification of Exocrine Glands
COMPOUND GLANDS
COMPOUND
TUBULAR
Examples:
• Mucous glands (in mouth)
• Bulbo-urethral glands (in
male reproductive system)
• Testes (seminiferous
tubules)
COMPOUND ALVEOLAR
(ACINAR)
Examples:
• Mammary glands
COMPOUND
TUBULOALVEOLAR
Examples:
• Salivary glands
• Glands of respiratory
passages
• Pancreas
Examples of exocrine gland products
•
•
•
•
•
•
•
Many types of mucus secreting glands
Sweat glands of skin
Oil glands of skin
Salivary glands of mouth
Liver (bile)
Pancreas (digestive enzymes)
Mammary glands (milk)
Endocrine glands
• Ductless glands
• Release hormones into extracellular space
– Hormones are messenger molecules
• Hormones enter blood and travel to
specific target organs
Connective Tissue
• Found everywhere in the body
• Includes the most abundant and widely
distributed tissues
• Functions
- Structural support
- Fluid transport
- protection of organs
- binds tissues together
- energy storage
- defense against microbes
Connective Tissue
Characteristics
• Specialized cells
• Variations in blood supply
– Some tissue types are well vascularized
– Some have a poor blood supply or are
avascular
• Extracellular matrix
– Non-living material that surrounds living cells\
– Makes up majority of tissue volume
– Gives cells speciality
Specialized Cells
• Fibroblasts – (most abundant) secretes proteins
• Fibrocytes – (2nd most abundant) – maintains tissue fiber
• Adipocytes – fat cells
• Mesenchymal cells – stem cells that respond to injury
• Macrophages – large white blood cells (fixed or free)
• Mast cells – stimulate inflammation after injury
• Lymphocytes – specialized immune cells
• Microphages – phagocytic blood cells
• Melanocytes – cells that produce and store melanin (skin
pigment)
Extracellular Matrix
• Two main elements
– Ground substance—mostly water along with
adhesion proteins and polysaccharide
molecules
– Fibers
• Produced by the cells
• Three types
– Collagen (white) fibers
– Elastic (yellow) fibers
– Reticular fibers
4-4 Connective Tissue
• Collagen Fibers
– Most common fibers in connective tissue
proper
– Long, straight, and unbranched
– Strong and flexible
– Resist force in one direction
– For example, tendons and ligaments
4-4 Connective Tissue
• Reticular Fibers
– Network of interwoven fibers (stroma)
– Strong and flexible
– Resist force in many directions
– Stabilize functional cells (parenchyma) and structures
– For example, sheaths around organs
4-4 Connective Tissue
• Elastic Fibers
– Contain elastin
– Branched and wavy
– Return to original length after stretching
– For example, elastic ligaments of vertebrae
4-4 Connective Tissue
• Ground Substance
– Is clear, colorless, and viscous
– Fills spaces between cells and slows
pathogen movement
Figure 4-8 The Cells and Fibers of Connective Tissue Proper
Reticular
fibers
Melanocyte
Fixed
macrophage
Plasma cell
Mast cell
Elastic
fibers
Free
macrophage
Collagen
fibers
Blood
in vessel
Fibroblast
Adipocytes
(fat cells)
Mesenchymal
cell
Ground
substance
Lymphocyte
4-4 Connective Tissue
• Categories of Connective Tissue Proper
– Loose connective tissue
• More ground substance, fewer fibers
• For example, fat (adipose tissue)
– Dense connective tissue
• More fibers, less ground substance
• For example, tendons
Connective Tissue Types
• Bone (osseous
tissue)
– Composed of
• Bone cells in lacunae
(cavities)
• Hard matrix of calcium
salts
• Large numbers of
collagen fibers
– Used to protect and
support the body
Connective Tissue Types
• Hyaline cartilage
– Most common type of
cartilage
– Composed of
• Abundant collagen
fibers
• Rubbery matrix
– Locations
• Larynx
• Entire fetal skeleton
prior to birth
Connective Tissue Types
• Elastic cartilage
– Provides elasticity
– Location
• Supports the external
ear
• Fibrocartilage
– Highly compressible
– Location
• Forms cushion-like
discs between
vertebrae
Connective Tissue Types
• Dense connective tissue
(dense fibrous tissue)
– Main matrix element is
collagen fiber
– Fibroblasts are cells that
make fibers
– Locations
• Tendons—attach skeletal
muscle to bone
• Ligaments—attach bone to
bone at joints
• Dermis—lower layers of the
skin
Connective Tissue Types
• Loose connective
tissue types
– Areolar tissue
• Most widely distributed
connective tissue
• Soft, pliable tissue like
“cobwebs”
• Functions as a packing
tissue
• Contains all fiber types
• Can soak up excess
fluid (causes edema)
Connective Tissue Types
• Loose connective
tissue types
– Adipose tissue
• Matrix is an areolar
tissue in which fat
globules predominate
• Many cells contain
large lipid deposits
• Functions
– Insulates the body
– Protects some organs
– Serves as a site of
fuel storage
Connective Tissue Types
• Loose connective
tissue types
– Reticular connective
tissue
• Delicate network of
interwoven fibers
• Forms stroma (internal
supporting network) of
lymphoid organs
– Lymph nodes
– Spleen
– Bone marrow
Connective Tissue Types
• Blood (vascular
tissue)
– Blood cells surrounded
by fluid matrix called
blood plasma
– Fibers are visible
during clotting
– Functions as the
transport vehicle for
materials
4-8 Muscle Tissue
•
Muscle Tissue
–
Specialized for contraction
–
Produces all body movement
–
Three types of muscle tissue
1. Skeletal muscle tissue
–
Large body muscles responsible for movement
2. Cardiac muscle tissue
–
Found only in the heart
3. Smooth muscle tissue
–
Found in walls of hollow, contracting organs (blood
vessels; urinary bladder; respiratory, digestive, and
reproductive tracts)
4-8 Muscle Tissue
• Classification of Muscle Cells
– Striated (muscle cells with a banded
appearance)
– Nonstriated (not banded; smooth)
– Muscle cells can have a single nucleus
– Muscle cells can be multinucleate
– Muscle cells can be controlled voluntarily
(consciously)
4-8 Muscle Tissue
• Skeletal Muscle Cells
– Long and thin
– Usually called muscle fibers
– Do not divide
– New fibers are produced by stem cells
(myosatellite cells)
Figure 4-18a Muscle Tissue
Skeletal Muscle Tissue
Cells are long, cylindrical,
striated, and multinucleate.
Nuclei
LOCATIONS: Combined
with connective tissues
and neural tissue in
skeletal muscles
FUNCTIONS: Moves or
stabilizes the position of
the skeleton; guards
entrances and exits to
the digestive,
respiratory, and urinary
tracts; generates heat;
protects internal organs
Muscle
fiber
Striations
Skeletal muscle
LM  180
4-8 Muscle Tissue
• Cardiac Muscle Cells
– Called cardiocytes
– Form branching networks connected at
intercalated discs
– Regulated by pacemaker cells
• Smooth Muscle Cells
– Small and tapered
– Can divide and regenerate
Figure 4-18b Muscle Tissue
Cardiac Muscle Tissue
Nucleus
Cells are short, branched,
and striated, usually with a
single nucleus; cells are
interconnected by
intercalated discs.
Cardiac
muscle
cells
LOCATION: Heart
FUNCTIONS:
Circulates blood;
maintains blood
(hydrostatic) pressure
Intercalated
discs
Striations
Cardiac muscle
LM  450
Figure 4-18c Muscle Tissue
Smooth Muscle Tissue
Cells are short, spindle-shaped, and
nonstriated, with a single, central
nucleus.
LOCATIONS: Found in
the walls of blood vessels
and in digestive, respiratory,
urinary, and reproductive organs
Nucleus
FUNCTIONS: Moves food,
urine, and reproductive tract
secretions; controls
diameter of respiratory
passageways; regulates
diameter of blood vessels
Smooth
muscle
cell
Smooth muscle
LM  235
4-9 Neural Tissue
• Neural Tissue
– Also called nervous or nerve tissue
• Specialized for conducting electrical impulses
• Rapidly senses internal or external environment
• Processes information and controls responses
– Neural tissue is concentrated in the central
nervous system
• Brain
• Spinal cord
4-9 Neural Tissue
• Two Types of Neural Cells
1. Neurons
• Nerve cells
• Perform electrical communication
2. Neuroglia
• Supporting cells
• Repair and supply nutrients to neurons
4-9 Neural Tissue
• Cell Parts of a Neuron
– Cell body
• Contains the nucleus and nucleolus
– Dendrites
• Short branches extending from the cell body
• Receive incoming signals
– Axon (nerve fiber)
• Long, thin extension of the cell body
• Carries outgoing electrical signals to their destination
Figure 4-19 Neural Tissue
NEURONS
NEUROGLIA (supporting cells)
Nuclei of neuroglia
Cell body
Axon
• Maintain physical structure
of tissues
• Repair tissue framework
after injury
• Perform phagocytosis
• Provide nutrients to neurons
• Regulate the composition of the
interstitial fluid surrounding neurons
Nucleolus
Nucleus
of neuron
Dendrites
LM  600
Dendrites
(contacted by
other neurons)
Mitochondrion
Nucleus
Axon (conducts
information to
other cells)
Microfibrils and
microtubules
Nucleolus
Contact with
other cells
Cell body (contains nucleus
and major organelles)
A representative neuron
(sizes and shapes vary widely)
Figure 4-19 Neural Tissue
Nuclei of neuroglia
Cell body
Axon
Nucleolus
Nucleus
of neuron
Dendrites
LM  600
Figure 4-19 Neural Tissue
NEUROGLIA (supporting cells)
• Maintain physical structure
of tissues
• Repair tissue framework
after injury
• Perform phagocytosis
• Provide nutrients to neurons
• Regulate the composition of the
interstitial fluid surrounding neurons
Figure 4-19 Neural Tissue
Dendrites
(contacted by
other neurons)
Mitochondrion
Nucleus
Axon (conducts
information to
other cells)
Microfibrils and
microtubules
Nucleolus
Cell body (contains nucleus
A representative neuron
and major organelles)
(sizes and shapes vary widely)
Contact with
other cells