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Four Types of Tissues
Tissues are collections of cells and cell
products that perform specific, limited
functions
Types of tissue
Epithelial tissue
Covers exposed surfaces
Lines internal passageways
Forms glands
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Four Types of Tissues
Types of Tissue (cont’d)
Connective tissue
Fills internal spaces
Supports other tissues
Transports materials
Stores energy
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
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Epithelial Tissues
Epithelia
Layers of cells covering internal or external
surfaces
Glands
Structures that produce secretions
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Epithelial Tissues
Characteristics of Epithelia
Cellularity (cell junctions)
Polarity (apical and basal surfaces)
Attachment (basal lamina)
Avascularity
Regeneration
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Epithelial Tissues
Figure 4–1 The Polarity of Epithelial Cells.
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Epithelial Tissues
Functions of Epithelial Tissue
Provide physical protection
Control permeability
Provide sensation
Produce specialized secretions (glandular
epithelium)
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Epithelial Tissues
Specializations of Epithelial Cells
Move fluids over the epithelium (protection)
Move fluids through the epithelium (permeability)
Produce secretions (protection and messengers)
Free Surface and Attached Surface
Polarity
Apical surfaces:
– microvilli increase absorption or secretion
– cilia (ciliated epithelium) move fluid
Basolateral surfaces
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Epithelial Tissues
Figure 4–2 Intercellular Connections
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Epithelial Tissues
Intercellular Connections
Cell junctions
Form bonds with other cells or extracellular material:
– occluding (tight) junctions
– gap junctions
– macula adherens (desmosomes)
Intercellular Connections
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Epithelial Tissues
Attachment to the Basal Lamina
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
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Epithelial Tissues
Epithelial Maintenance and Repair
Epithelia are replaced by division of
germinative cells (stem cells)
Near basal lamina
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Classification of Epithelia
Singular epithelium; plural epithelia
Classes of Epithelia
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
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Classification of Epithelia
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Classification of Epithelia
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Classification of Epithelia
Squamous Epithelia
Simple squamous epithelium
Absorption and diffusion
Mesothelium
Lines body cavities
Endothelium
Lines heart and blood vessels
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Classification of Epithelia
Figure 4–3 Squamous Epithelia.
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Classification of Epithelia
Squamous Epithelia
Stratified squamous epithelium
Protects against attacks
Keratin protein adds strength and water resistance
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Classification of Epithelia
Figure 4–3 Squamous Epithelia.
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Classification of Epithelia
Cuboidal Epithelia
Simple cuboidal epithelium
Secretion and absorption
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Classification of Epithelia
Figure 4–4 Cuboidal Epithelia.
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Classification of Epithelia
Cuboidal Epithelia
Stratified cuboidal epithelia
Sweat ducts and mammary ducts
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Classification of Epithelia
Figure 4–4 Cuboidal Epithelia.
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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)
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Classification of Epithelia
Figure 4–4 Cuboidal Epithelia.
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Classification of Epithelia
Columnar Epithelia
Simple columnar epithelium
Absorption and secretion
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Classification of Epithelia
Figure 4–5 Columnar Epithelia.
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Classification of Epithelia
Columnar Epithelia
Pseudostratified columnar epithelium
Cilia movement
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Classification of Epithelia
Figure 4–5 Columnar Epithelia.
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Classification of Epithelia
Columnar Epithelia
Stratified columnar epithelium
Protection
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Classification of Epithelia
Figure 4–5 Columnar Epithelia.
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Classification of Epithelia
Glandular Epithelia
Endocrine glands
Release hormones:
– into interstitial fluid
– no ducts
Exocrine glands
Produce secretions:
– onto epithelial surfaces
– through ducts
Mechanisms of Glandular Secretion
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Classification of Epithelia
Modes of Secretion in Glandular Epithelia
Merocrine secretion
Is produced in Golgi apparatus
Is released by vesicles (exocytosis)
For example, sweat glands
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Classification of Epithelia
Figure 4–6 Modes of Glandular Secretion.
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Classification of Epithelia
Modes of Secretion in Glandular Epithelia
Apocrine secretion
Is produced in Golgi apparatus
Is released by shedding cytoplasm
For example, mammary gland
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Classification of Epithelia
Figure 4–6 Modes of Glandular Secretion.
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Classification of Epithelia
Modes of Secretion in Glandular Epithelia
Holocrine secretion
Is released by cells bursting, killing gland cells
Gland cells replaced by stem cells
For example, sebaceous gland
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Classification of Epithelia
Figure 4–6 Modes of Glandular Secretion.
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Classification of Epithelia
Glandular Epithelia
Types of secretions
Serous glands:
– watery secretions
Mucous glands:
– secrete mucins
Mixed exocrine glands:
– both serous and mucous
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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
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Classification of Epithelia
Glandular Epithelia
Gland structure
Multicellular glands:
– 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)
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Classification of Epithelia
Figure 4–7 A Structural Classification of Exocrine Glands.
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Classification of Epithelia
Figure 4–7 A Structural Classification of Exocrine Glands.
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Tissue Injuries and Repair
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Tissue Injuries and Repair
Tissues respond to injuries to maintain
homeostasis
Cells restore homeostasis with two processes
Inflammation
Regeneration
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Tissue Injuries and Repair
Inflammation = inflammatory response
The tissue’s first response to injury
Signs and symptoms of the inflammatory
response include
Swelling
Redness
Heat
Pain
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Tissue Injuries and Repair
Inflammatory Response
Can be triggered by
Trauma (physical injury)
Infection (the presence of harmful pathogens)
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Tissue Injuries and Repair
The Process of Inflammation
Damaged cells release chemical signals into the
surrounding interstitial fluid
Lysosomes release enzymes that destroy the injured cell
And attack surrounding tissues. Tissue destruction is called
necrosis
As cells break down
Necrotic tissues and cellular debris (pus) accumulate
in the wound
Injury stimulates mast cells to release
Histamine, Heparin, Prostaglandins
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Tissue Injuries and Repair
The Process of Inflammation
Dilation of blood vessels
Increases blood circulation in the area
Causes warmth and redness
Brings more nutrients and oxygen to the area
Removes wastes
Plasma diffuses into the area
Causing swelling and pain
Phagocytic white blood cells
Clean up the area
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Tissue Injuries and Repair
Regeneration
When the injury or infection is cleaned up
Healing (regeneration) begins
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Tissue Injuries and Repair
The Process of Regeneration
Fibrocytes move into necrotic area
Lay down collagen fibers
To bind the area together (scar tissue)
New cells migrate into area
Or are produced by mesenchymal stem cells
Not all tissues can regenerate
Epithelia and connective tissues regenerate well
Cardiac cells and neurons do not regenerate (or regenerate
poorly)
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Aging and Tissue
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Aging and Tissue
Aging and Tissue Structure
Speed and efficiency of tissue repair
decreases with age, due to
Slower rate of energy consumption (metabolism)
Hormonal alterations
Reduced physical activity
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Aging and Tissue
Effects of Aging
Chemical and structural tissue changes
Thinning epithelia and connective tissues
Increased bruising and bone brittleness
Joint pain and broken bones
Cardiovascular disease
Mental deterioration
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Aging and Tissue
Aging and Cancer Incidence
Cancer rates increase with age
1 in 4 people in the United States develops cancer
Cancer is the #2 cause of death in the United
States
Environmental chemicals and cigarette smoke
cause cancer