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Chapter 4: Organization
at the Tissue Level
Tissues are collections of cells that serve
a collective purpose
 Collections of tissues form organs

Socrative app – course 701439
?1. What is your name
? 2. Name 4 types of tissue.
© 2012 Pearson Education, Inc.
An Introduction to Tissues

Tissues

Structures with discrete structural and
functional properties

Tissues in combination form organs, such as
the heart or liver

Organs can be grouped into 11 organ systems
? 3. List the 11 organ systems
© 2012 Pearson Education, Inc.
4-1 Four Types of Tissue

Tissue

Are collections of cells and cell products that
perform specific, limited functions

Four types of tissue
1.
Epithelial tissue
2.
Connective tissue
3.
Muscle tissue
4.
Neural tissue
© 2012 Pearson Education, Inc.
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
© 2012 Pearson Education, Inc.
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
© 2012 Pearson Education, Inc.
4-2 Epithelial Tissue

Epithelia

Layers of cells covering internal or external
surfaces

Glands

Structures that produce secretions
© 2012 Pearson Education, Inc.
4-2 Epithelial Tissue

Characteristics of Epithelia

Cellularity (cell junctions)


** Cell membrane features
Polarity (apical and basal surfaces)

** think apex (top; peak) and basement (below)

Attachment (basement membrane or basal lamina)

Avascularity


Without blood vessels
Regeneration
© 2012 Pearson Education, Inc.
Figure 4-1 The Polarity of Epithelial Cells
Cilia
Microvilli
Apical
surface
Golgi
apparatus
Nucleus
Mitochondria
Basement membrane
Basolateral
surfaces
© 2012 Pearson Education, Inc.
4-2 Epithelial Tissue

Functions of Epithelial Tissue
1.
Provide Physical Protection
2.
Control Permeability
3.
Provide Sensation
4.
Produce Specialized Secretions (glandular
epithelium)
© 2012 Pearson Education, Inc.
4-2 Epithelial Tissue

Specializations of Epithelial Cells
1.
Move fluids over the epithelium (protection)
2.
Move fluids through the epithelium (permeability)
3.
Produce secretions (protection and messengers)
© 2012 Pearson Education, Inc.
? 4. What are 4 functions of
epithelial cell?
© 2012 Pearson Education, Inc.
4-2 Epithelial Tissue

Intercellular Connections

Support and communication

CAMs (cell adhesion molecules)


Intercellular cement


Transmembrane proteins
Proteoglycans
Hyaluronan (hyaluronic acid)

Glycosaminoglycans
© 2012 Pearson Education, Inc.
4-2 Epithelial Tissue

Intercellular Connections

Cell junctions

Form bonds with other cells or extracellular
material
1.
Tight junctions
2.
Gap junctions
3.
Desmosomes
© 2012 Pearson Education, Inc.
Figure 4-2 Cell Junctions
Interlocking
junctional
proteins
Tight junction
Tight junction
Adhesion belt
Terminal web
Spot
desmosome
Adhesion belt
Gap
junctions
Hemidesmosome
Embedded proteins
(connexons)
Clear
layer
Dense
layer
Intermediate
filaments
Basement
membrane
Dense area
Cell adhesion
molecules (CAMs)
Proteoglycans
© 2012 Pearson Education, Inc.
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.
© 2012 Pearson Education, Inc.
4-2 Epithelial Tissue

Tight Junctions

Between two plasma membranes

Adhesion belt attaches to terminal web

Prevents passage of water and solutes

Isolates wastes in the lumen (open space
down the center of a tube)
© 2012 Pearson Education, Inc.
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.
© 2012 Pearson Education, Inc.
4-2 Epithelial Tissue

Gap Junctions

Allow rapid communication

Are held together by channel proteins
(junctional proteins, connexons)

Allow ions to pass

Coordinate contractions in heart muscle
© 2012 Pearson Education, Inc.
Figure 4-2c Cell Junctions
Embedded proteins
(connexons)
Gap junctions permit the
free diffusion of ions and
small molecules between
two cells.
© 2012 Pearson Education, Inc.
4-2 Epithelial Tissue

Desmosomes

CAMs, dense areas, and intercellular
cement

Spot desmosomes (“spot weld”)
 Tie
cells together
 Allow

bending and twisting
Hemidesmosomes
 Attach
© 2012 Pearson Education, Inc.
cells to the basal lamina
Figure 4-2d Cell Junctions
Intermediate
filaments
Cell adhesion
molecules (CAMs)
Dense area
Proteoglycans
A spot desmosome ties
adjacent cells together.
© 2012 Pearson Education, Inc.
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.
© 2012 Pearson Education, Inc.
Basement
membrane
? 5. What types of intercellular
connections are used to ‘glue’
epithelial cells together?
© 2012 Pearson Education, Inc.
4-2 Epithelial Tissue

Attachment to the Basement Membrane


Clear layer (lamina lucida)

Thin layer

Secreted by epithelia

Barrier to proteins
Dense layer (lamina densa)

Thick fibers

Produced by connective tissue

Strength and filtration
© 2012 Pearson Education, Inc.
4-2 Epithelial Tissue

Epithelial Maintenance and Repair

Epithelia are replaced by division of
germinative cells (stem cells)

Near basement membrane
© 2012 Pearson Education, Inc.
4-3 Classification of Epithelia

Singular = Epithelium; Plural = Epithelia

Classes of Epithelia
1.
2.
Based on shape

Squamous epithelia — thin and flat

Cuboidal epithelia — square shaped

Columnar epithelia — tall, slender rectangles
Based on layers

Simple epithelium — single layer of cells

Stratified epithelium — several layers of cells
© 2012 Pearson Education, Inc.
Table 4-1 Classifying Epithelia
© 2012 Pearson Education, Inc.
Table 4-1 Classifying Epithelia
© 2012 Pearson Education, Inc.
4-3 Classification of Epithelia

Squamous Epithelia

Simple squamous epithelium


Mesothelium


Absorption and diffusion
Lines body cavities
Endothelium

Lines heart and blood vessels
© 2012 Pearson Education, Inc.
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
© 2012 Pearson Education, Inc.
LM  238
4-3 Classification of Epithelia

Squamous Epithelia

Stratified squamous epithelium

Protects against attacks

Keratin protein adds strength and water resistance
© 2012 Pearson Education, Inc.
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
© 2012 Pearson Education, Inc.
LM  310
4-3 Classification of Epithelia

Cuboidal Epithelia

Simple cuboidal epithelium


Secretion and absorption
Stratified cuboidal epithelia

Sweat ducts and mammary ducts
© 2012 Pearson Education, Inc.
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
© 2012 Pearson Education, Inc.
LM  650
Figure 4-4b Cuboidal and Transitional Epithelia
Stratified Cuboidal Epithelium
LOCATIONS: Lining of some ducts
(rare)
FUNCTIONS: Protection, secretion,
absorption
Lumen
of duct
Stratified
cuboidal
cells
Basement
membrane
Nuclei
Connective
tissue
Sweat gland duct
© 2012 Pearson Education, Inc.
LM  500
? 6. What are the major classifications
of epithelial cells?
*** pg 116, 117***
© 2012 Pearson Education, Inc.
4-3 Classification of Epithelia

Transitional Epithelium

Tolerates repeated cycles of stretching and
recoiling and returns to its previous shape
without damage

Appearance changes as stretching occurs

Situated in regions of the urinary system (e.g.,
urinary bladder)
© 2012 Pearson Education, Inc.
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
© 2012 Pearson Education, Inc.
Basement membrane
Connective tissue and
smooth muscle layers
LM  400
LM  400
4-3 Classification of Epithelia

Columnar Epithelia

Simple columnar epithelium


Pseudostratified columnar epithelium


Absorption and secretion
Cilia movement
Stratified columnar epithelium

Protection
© 2012 Pearson Education, Inc.
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
© 2012 Pearson Education, Inc.
Basement
membrane
Loose
connective tissue
LM  350
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
© 2012 Pearson Education, Inc.
Loose
connective tissue
LM  350
Figure 4-5c Columnar Epithelia
Stratified Columnar Epithelium
LOCATIONS: Small areas of
the pharynx, epiglottis, anus,
mammary glands, salivary
gland ducts, and urethra
FUNCTION: Protection
Lumen
Loose
connective tissue
Deeper basal
cells
Superficial
columnar cells
Lumen
Cytoplasm
Nuclei
Salivary gland duct
© 2012 Pearson Education, Inc.
Basement
membrane
LM  175
4-3 Classification of Epithelia

Glandular Epithelia

Endocrine glands


Release hormones

Into interstitial fluid

No ducts (adrenal glands, ovaries, testes)
Exocrine glands

Produce secretions

Onto epithelial surfaces

Through ducts (sweat, salivary, mammary)
© 2012 Pearson Education, Inc.
4-3 Classification of Epithelia

Glandular Epithelia

Modes of Secretion
1.
Merocrine secretion
2.
Apocrine secretion
3.
Holocrine secretion
© 2012 Pearson Education, Inc.
4-3 Classification of Epithelia

Merocrine Secretion




Produced in Golgi apparatus
Released by vesicles (exocytosis)
For example, sweat glands
Apocrine Secretion



Produced in Golgi apparatus
Released by shedding cytoplasm
For example, mammary glands
© 2012 Pearson Education, Inc.
4-3 Classification of Epithelia

Holocrine Secretion

Released by cells bursting, killing gland cells

Gland cells replaced by stem cells

For example, sebaceous glands
© 2012 Pearson Education, Inc.
4-3 Classification of Epithelia

Glandular Epithelia

Types of Secretions

Serous glands


Mucous glands


Watery secretions
Secrete mucins
Mixed exocrine glands

Both serous and mucous
© 2012 Pearson Education, Inc.
4-3 Classification of Epithelia

Glandular Epithelia

Gland Structure

Unicellular glands

Mucous (goblet) cells are the only unicellular exocrine glands

Scattered among epithelia

For example, in intestinal lining
© 2012 Pearson Education, Inc.
4-3 Classification of Epithelia

Gland Structure

Multicellular glands
1.
2.
3.
Structure of the duct
 Simple (undivided)
 Compound (divided)
Shape of secretory portion of the gland
 Tubular (tube shaped)
 Alveolar or acinar (blind pockets)
Relationship between ducts and glandular areas
 Branched (several secretory areas sharing one duct)
© 2012 Pearson Education, Inc.
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
© 2012 Pearson Education, Inc.
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)
© 2012 Pearson Education, Inc.
COMPOUND ALVEOLAR
(ACINAR)
Examples:
• Mammary glands
COMPOUND
TUBULOALVEOLAR
Examples:
• Salivary glands
• Glands of respiratory
passages
• Pancreas
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