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Copyright 2009, John Wiley & Sons, Inc.
Chapter 4The Tissue Level of
Organization
Copyright 2009, John Wiley & Sons, Inc.
What is a Tissue?
A tissue is a group of cells Common embryonic origin Function together to carry out specialized
activities Hard (bone), semisolid (fat), or liquid (blood) Histology is the science that deals with the
study of tissues. Pathologist specialized in laboratory studies
of cells and tissue for diagnoses
Copyright 2009, John Wiley & Sons, Inc.
4 Types of Tissues Epithelial Covers body surfaces and lines hollow organs,
body cavities, duct, and forms glands Connective Protects, supports, and binds organs. Stores energy as fat, provides immunity
Muscular Generates the physical force needed to make body
structures move and generate body heat Nervous Detect changes in body and responds by
generating nerve impulses
Copyright 2009, John Wiley & Sons, Inc.
Development of Tissues
Tissues of the body develop from three primary germ layers: Ectoderm, Endoderm, and Mesoderm
Epithelial tissues develop from all three germ layers
All connective tissue and most muscle tissues drive from mesoderm
Nervous tissue develops from ectoderm
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Cell Junctions
Contact points between the plasma membranes of tissue cells 5 most common types: Tight junctions Adherens junctions Desmosomes Hemidesmosomes Gap junctions
Copyright 2009, John Wiley & Sons, Inc.
Tight Junctions
Web-like strands of transmembrane proteins Fuse cells together Seal off passageways
between adjacent cells Common in epithelial
tissues of the stomach, intestines, and urinary bladder
Help to retard the passage of substances between cells and leaking into the blood or surrounding tissues
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Adherens Junctions Dense layer of proteins called
plaque Resist separation of cells
during contractile activities Located inside of the plasma
membrane attached to both membrane proteins and microfilaments of the cytoskeleton
Transmembrane glycoproteins called cadherins insert into the plaque and join cells
In epithelial cells, adhesion belts encircle the cell
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Desmosomes
Contain plaque and cadherins that extends into the intercellular space to attach adjacent cells together Desmosome plaque
attaches to intermediate filaments that contain protein keratin
Prevent epidermal cells from separating under tension and cardiac muscles cells from pulling apart during contraction
Copyright 2009, John Wiley & Sons, Inc.
Hemidesmosomes
Resemble half of a desmosome Do not link adjacent cells
but anchor cells to the basement membrane
Contains transmembrane glycoprotein integrin
Integrins attach to intermediate filaments and the protein lamininpresent in the basement membrane
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Gap Junctions
Connect neighboring cells via tiny fluid-filled tunnels called connexons Contain membrane proteins
called connexins Plasma membranes of gap
junctions are separated by a very narrow intercellular gap (space) Communication of cells
within a tissue Ions, nutrients, waste,
chemical and electrical signals travel through the connexons from one cell to another
Copyright 2009, John Wiley & Sons, Inc.
Epithelial Tissues
Epithelial tissue consists of cells arranged in continuous sheets, in either single or multiple layers Closely packed and held tightly together Covering and lining of the body Free surface
3 major functions: Selective barrier that regulates the movement of materials
in and out of the body Secretory surfaces that release products onto the free
surface Protective surfaces against the environment
Copyright 2009, John Wiley & Sons, Inc.
General Features of Epithelial Cells
Surfaces of epithelial cells differ in structure and have specialized functions Apical (free) surface
Faces the body surface, body cavity, lumen, or duct
Lateral surfaces Faces adjacent cells
Basal surface Opposite of apical layer and adhere to extracellular
materials
Copyright 2009, John Wiley & Sons, Inc.
General Features of Epithelial Cells
Basement membrane Thin double extracellular layer that serves as the point of
attachment and support for overlying epithelial tissue Basal lamina
Closer to and secreted by the epithelial cells Contains laminin, collagen, glycoproteins, and proteoglycans
Reticular lamina Closer to the underlying connective tissue Contains collagen secreted by the connective tissue cells
Copyright 2009, John Wiley & Sons, Inc.
Epithelial Cells
Copyright 2009, John Wiley & Sons, Inc.
Epithelial Tissues Own nerve supply Avascular or lacks its own blood supply Blood vessels in the connective tissue bring in
nutrients and eliminate waste High rate of cell division for renew and repair Numerous roles in the body (i.e. protection and
filtration) Covering and lining epithelium
Outer covering of skin and some internal organs
Glandular epithelium Secreting portion of glands (thyroid, adrenal, and sweat
glands)
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Covering and Lining Epithelium
Normally classified according to: Arrangement of cells into layers Shapes of cells
Copyright 2009, John Wiley & Sons, Inc.
Covering and Lining Epithelium
Arrangement of cells in layers Consist of one or more layers depending on function Simple epithelium
Single layer of cells that function in diffusion, osmosis, filtration, secretion, or absorption
Pseudostratified epithelium Appear to have multiple layers because cell nuclei at different
levels All cells do not reach the apical surface
Stratified epithelium Two or more layers of cells that protect underlying tissues in
areas of wear and tear
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Different Types of Covering and Lining Epithelium Cells vary in shape depending on their
function Squamous
Thin cells, arranged like floor tiles Allows for rapid passage of substances
Cuboidal As tall as they are wide, shaped like cubes or hexagons May have microvilli Function in secretion or absorption
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Different Types of Covering and Lining Epithelium Columnar
Much taller than they are wide, like columns May have cilia or microvilli Specialized function for secretion and absorption
Transitional Cells change shape, transition for flat to cuboidal Organs such as urinary bladder stretch to larger size
and collapse to a smaller size
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Simple Epithelium
Simple squamous epithelium Simple cuboidal epithelium Simple columnar epithelium (nonciliated and
ciliated) Pseudostratified columnar epithelium (nonciliated
and cilated)
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Simple squamous epithelium
Single layer of cells that resembles a tiled floor on the surface Nucleus is centrally located and appears flattened oval or
sphere Found at sites for filtration or diffusion
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Covering and Lining Epithelium
Endothelium The type of simple squamous that lines the heart,
blood vessels, and lymphatic vessels Mesothelium The type of epithelial layer of serous membranes
such as the pericardium, pleura, or peritoneum Unlike other epithelial tissue, Both are
derived from embryonic mesoderm
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Simple cuboidal epithelium
Cuboidal shaped cells Cell nuclei round and centrally located Found in thyroid gland and kidneys Functions in secretion and absorption
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Simple columnar epithelium
Column shaped cells Oval nuclei at near base Nonciliated and ciliated
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Nonciliated simple columnar epithelium
Contains columnar cells with microvilli at their apical surface and goblet cells
Secreted mucus serves as lubricant for the lining of digestive, respiratory, reproductive and urinary tracts
Also prevents the destruction of the stomach lining by acidic gastric juices
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Ciliated simple columnar epithelium Columnar epithelial cells
with cilia at the apical surface In respiratory tract,
goblet cells are interspersed among ciliated columnar epithelia
Secreted mucus on the surface traps inhaled foreign particles. Beating cilia moves particles to the throat for removal by coughing, swallowing, or sneezing
Cilia also moves oocytes to the uterine tubes
Copyright 2009, John Wiley & Sons, Inc.
Covering and Lining Epithelium
Pseudostratified columnar epithelium Appears to have several layers due to nuclei are
various depths All cells are attached to the basement membrane
in a single layer but some do not extend to the apical surface
Ciliated cells secrete mucus and bear cilia Nonciliated cells lack cilia and goblet cells
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Covering and Lining Epithelium
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Stratified Epithelium
Two or more layers of cells Specific kind of stratified epithelium depends
on the shape of cells in the apical layer Stratified squamous epithelium Stratified cuboidal epithelium Stratified columunar epithelium Transitional epithelium
Copyright 2009, John Wiley & Sons, Inc.
Stratified Squamous Epithelium Several layers of cells that are flat in the apical layer
New cells are pushed up toward apical layer As cells move further from the blood supply they dehydrate, harden,
and die Keratinized form contain the fibrous protein keratin
Found in superficial layers of the skin Nonkeratinized form does not contain keratin
Found in mouth and esophagus
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Stratified Cuboidal Epithelium
Fairly rare type of epithelium Apical layers are cuboidal Functions in protection
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Stratified columnar epithelium
Also very uncommon Columnar cells in apical layer only Basal layers has shorten, irregular shaped cells Functions in protection and secretion
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Transitional Epithelium Found only in the urinary system Variable appearance In relaxed state, cells appear cuboidal Upon stretching, cells become flattened and appear
squamous Ideal for hollow structure subjected to expansion
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Glandular Epithelium: Endocrine Glands
Secretions, called hormones, diffuse directly into the bloodstream
Function in maintaining homeostasis
Copyright 2009, John Wiley & Sons, Inc.
Glandular Epithelium: Exocrine Glands
Secrete products into ducts that empty onto the surfaces of epithelium
Skin surface or lumen of a hollow organ Secretions of the exocrine gland include mucus, sweat, oil,
earwax, saliva, and digestive enzymes Examples of glands include sudoriferous (sweat) glands
Copyright 2009, John Wiley & Sons, Inc.
Structural Classification of Exocrine Glands Multicellular glands are categorized
according to two criteria: Ducts are branched or unbranched Shape of the secretory portion of the gland
Simple gland duct does not branch Compound gland duct branches Tubular glands have tubular secretory parts Acinar glands have rounded secretory parts Tubuloacinar glands have both tubular and rounded
secretory parts
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Structural Classification of Exocrine Glands
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Functional Classification of Exocrine Glands
Copyright 2009, John Wiley & Sons, Inc.
Connective Tissue
Most abundant and widely distributed tissues in the body
Numerous functions Binds tissues together Supports and strengthen tissue Protects and insulates internal organs Compartmentalize and transport Energy reserves and immune responses
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Extracellular matrix of Connective Tissue Extracellular matrix is the material located
between the cells Consist of protein fibers and ground substance
Connective tissue is highly vascular Supplied with nerves Exception is cartilage and tendon. Both have little
or no blood supply and no nerves
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Cells and Fibers in Connective Tissue
Copyright 2009, John Wiley & Sons, Inc.
Connective Tissue Cells Fibroblasts
Secrete fibers and components of ground substance Adipocytes (fat cells)
Store triglycerides (fat) Mast cells
Produce histamine White blood cells
Immune response Neutrophil and Eosinophils
Macrophages Engulf bacteria and cellular debris by phagocytosis
Plasma cells Secrete antibodies
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Connective Tissue Extracellular Matrix Ground substance
Between cells and fibers Fluid, semifluid, gelatinous, or calcified
Functions to support and bind cells, store water, and allow exchange between blood and cells
Complex combination of proteins and polysaccharides
Fibers Collagen fibers Elastic fibers Reticular fibers
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Classification of Connective Tissues
Embryonic connective tissue Mesenchyme and mucous connective tissue
Mature connective tissue Loose connective tissue
Areolar, adipose, and reticular Dense connective tissue
Dense regular, dense irregular, and elastic Cartilage
Hyaline, fibrocartilage, and elastic cartilage Bone tissue Liquid connective tissue
Blood and lymph
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Embryonic Connective Tissue Mesenchyme Gives rise to all other connective tissues
Mucous (Wharton’s Jelly) Found in umbilical cord of the fetus
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Loose Connective Tissue: Areolar Connective Tissue
Most widely distributed in the body Contains several types of cells and all three fibers
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Loose Connective Tissue: Adipose Tissue
Contains adipocytes Good for insulation and energy reserves White (common) and brown adipose tissue
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Loose Connective Tissue: Reticular Connective Tissue
Fine interlacing reticular fibers and cells Forms the stroma of liver, spleen, and lymph nodes
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Dense Connective Tissue Dense connective tissue
Contains numerous, thicker, and denser fibers Packed closely with fewer cells than loose connective tissue
Dense regular connective tissue Bundles of collagen fibers are regularly arranged in parallel
patterns for strength Tendons and most ligaments
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Types of Mature Connective Tissue: Dense Irregular Connective Tissue
Collagen fibers are usually irregularly arranged Found where pulling forces are exerted in many directions Dermis of skin and heart
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Dense Connective Tissue: Elastic Connective Tissue
Contain branching elastic fibers Strong and can recoil to original shape after stretching Lung tissue and arteries
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Types of Mature Connective Tissue: Cartilage Cartilage is a dense network of collagen
fibers and elastic fibers firmly embedded in chondroitin sulfate Chrondrocytes
Cartilage cells found in the spaces called lucunae Pericondrium
Covering of dense irregular connective tissue that surrounds the cartilage
Two layers: outer fibrous layer and inner cellular layer No blood vessels or nerves, except
pericondrium
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Hyaline cartilage
Most abundant cartilage in the body Surrounding by perichondrium (some exceptions like
articular cartilage) Provide flexibility and support. Reduces friction
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Fibrocartilage Chondrocytes are scattered among bundles of collagen
fibers within the extracellular matrix Lack a perchondrium Strongest type of cartilage Found in intervertebral disc (between vertebrae)
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Elastic Cartilage
Chrondrocytes are located within a threadlike network of elastic fibers
Pericondrium is present Provides strength and elasticity
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Repair and Growth of Cartilage
Cartilage grows slowly When injured or inflamed, repairs is slow due
to its avascular nature. Two patterns of cartilage growth: Interstitial growth
Growth from within the tissue
Appositional growth Growth at the outer surface of the tissue
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Bone tissue Bones are organs composed of several different
connective tissues: bone (osseous) tissue, periosteum, and endosteum.
Compact or spongy Osteon or haversian system
Spongy bone lacks osteons. They have columns called trabeculae
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Liquid Connective Tissue
Blood tissue Connective tissue with liquid extracellular matrix called blood
plasma Lymph
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Membranes
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Epithelial Membranes
Mucous membranes Lines a body cavity that opens directly to the
exterior Epithelial layer is important for the body’s defense
against pathogens Connective tissue layer is areolar connective
tissue and is called lamina propria
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Epithelial Membranes
Serous membranes or serosa Lines a body cavity that does not open directly to
the exterior. Also covers the organs that lie within the cavity
Consist of areolar connective tissue covered by mesothelium (simple squamous epithelium) that secrete a serous fluid for lubrication
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Epithelial membranes: Mucous Membranes Membranes are flat sheets of pliable tissue
that cover or line a part of the body Epithelial membranes are a combination of
an epithelial layer and an underlying connective tissue layer Mucous, Serous, and Cutaneous membranes
Synovial membranes Lines joints and contains connective tissue but not
epithelium
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Muscular Tissue
Consists of elongated cells called muscle fibers or myocytes Cells use ATP to generate force Several functions of muscle tissue Classified into 3 types: skeletal, cardiac, and
smooth muscular tissue
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Skeletal Muscle Tissue
Attached to bones of the skeleton Have striations Voluntary movement or contractions by conscious control Vary in length (up to 40 cm) and are roughly cylindrical in
shape
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Muscular Tissue
Cardiac muscle tissue Have striations Involuntary movement or contraction is not consciously
controlled Intercalated disc unique to cardiac muscle tissue
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Smooth Muscle Tissue
Walls of hollow internal structures Blood vessels, airways of lungs, stomach, and intestines
Nonstriated Usually involuntary control
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Nervous Tissue Consists of two principle types of cells
Neurons or nerve cells Neuroglia
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Excitable Cells
Neurons and muscle fibers Exhibit electrical excitability The ability to respond to certain stimuli by
producing electrical signals such as action potentials
Actions potentials propagate along a nerve or muscle plasma membrane to cause a response Release of neurotransmitters Muscle contraction
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Tissue Repair: Restoring Homeostasis
When tissue damage is extensive both stroma and parenchymal cells are active in repair Fibroblast divide rapidly New collagen fibers are manufactured New blood capillaries supply materials for healing
All of these process create an actively growing connective tissue called granulation tissue
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Aging and Tissues
Tissue heal faster in young adults Surgery of a fetus normally leaves no scars Young tissues have a better nutritional state,
blood supply, and higher metabolic rate Extracellular components also changes with
age Changes in the body’s use of glucose,
collagen, and elastic fibers contribute to the aging process
Copyright 2009, John Wiley & Sons, Inc.
End of Chapter 4
Copyright 2009 John Wiley & Sons, Inc.All rights reserved. Reproduction or translation of this work beyond that permitted in section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Request for further information should be addressed to the Permission Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publishers assumes no responsibility for errors, omissions, or damages caused by the use of theses programs or from the use of the information herein.