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Tissues

Groups of cells with a common function
Four primary tissues:
Epithelia
Connective tissues
Muscle
Nervous
Epithelial Tissues

Line body cavities and cover surfaces
Glandular epithelia: epithelial cells adapted to
make up glands:
 Exocrine glands: secretion into ducts to exterior of body
 Endocrine glands: secretion into the blood to carry
chemical messages throughout the body
 Functions of epithelium




Protection
Absorption, secretion, and ion transport
Filtration
Forms slippery surfaces
Studying Human Tissue:
Microscopy

 Tissue is fixed
 Preserved
 Cut
 Sliced thin enough to transmit light or electrons
 Stained
 Enhances contrast
Characteristics of Epithelial
Tissue: Polarity

 Cells have polarity
 Apical surface (upper free) exposed to exterior or
cavity
 Basal surface (lower, attached)
 Both surfaces differ in structure and function
Special Characteristics of Epithelia
Apical Surface of
Epithelial Tissues

 May be smooth & slick
 Most have microvilli (e.g., brush border of intestinal
lining)
 Increase surface area
 Some have cilia (e.g., lining of trachea)
Basal Surface of
Epithelial Tissues

 Noncellular basal lamina
 Glycoprotein and collagen fibers lies adjacent to basal
surface
 Adhesive sheet
 Selective filter
 Scaffolding for cell migration in wound repair
Epithelial Tissues:
Attachments

 Basement membrane:
 Structural support
 Attaches epithelial layer to underlying tissues
 Junctions: hold epithelial cells together:
 Tight junctions: nothing passes
 Adhesion junctions/spot desmosomes: some movement
between cells
 Gap junctions: protein channels
Epithelial Tissues

Classification of Epithelia

 All epithelial tissues have two names
 One indicates number of cell layers
 Simple epithelia = single layer of cells
 Stratified epithelia = two or more layers of cells
 Shape can change in different layers
 One indicates shape of cells
 Squamous
 Cuboidal
 Columnar
 In stratified epithelia, epithelia classified by cell
shape in apical layer
Shape:
Epithelial Tissues:
Classification

 Squamous: flattened cells, line vessels, part of lungs,
body surface
 Cuboidal: cube shaped, form lining of tubules,
glandular tissue
 Columnar: column shaped; line respiratory, digestive,
reproductive tracts
Epithelial Tissues:
Classification

Number of layers:
 Simple/single layered: adapted for diffusion across cell
barriers; line glands, and respiratory, digestive,
reproductive systems
 Stratified/multiple layered: protection, skin surface
Naming Epithelia

 Naming the epithelia includes both the layers (first)
and the shape of the cells (second)
 i.e. stratified cuboidal epithelium
 The name may also include any accessory structures
 Goblet cells
 Cilia
 Keratin
 Special epithelial tissues (don’t follow naming
convention)
 Pseudostratified
 Transitional
Simple Squamous Epithelium
 Function

 Passage of materials by passive diffusion and filtration
 Secretes lubricating substances in serosae
 Location
 Renal corpuscles
 Alveoli of lungs
 Lining of heart, blood and lymphatic vessels
 Lining of ventral body cavity (serosae)
Simple Squamous Epithelium
Simple
squamous lining
the walls of the
capillary
Simple Cuboidal Epithelium
Description

 single layer of cube-like cells with large, spherical
central nuclei
Function
 secretion and absorption
Location
 kidney tubules, secretory
portions of small glands,
ovary & thyroid follicles
Simple Cuboidal
Epithelium
Simple Columnar Epithelium
 Description

 Single layer of column-shaped (rectangular) cells with
oval nuclei
 Some bear cilia at their apical surface
 May contain goblet cells
 Function
 Absorption; secretion of mucus, enzymes, and other
substances
 Ciliated type propels mucus or reproductive cells by
ciliary action
Simple Columnar Epithelium
 Location
 Non-ciliated form
 Lines digestive tract,
gallbladder, ducts of
some glands
 Ciliated form
 Lines small bronchi,
uterine tubes, uterus
Pseudostratified Columnar
Epithelium

Description
 All cells originate at basement membrane
 Only tall cells reach the apical surface
 May contain goblet cells and bear cilia
 Nuclei lie at varying heights within cells
 Gives false impression of stratification
Function
 secretion of mucus; propulsion of mucus by cilia
Pseudostratified Columnar
Epithelium
 Locations
 Non-ciliated type
 Ducts of male reproductive
tubes
 Ducts of large glands
 Ciliated variety
 Lines trachea and most of
upper respiratory tract
Stratified Epithelia

 Contain two or more layers of cells
 Regenerate from below
 Major role is protection
 Are named according to the shape of cells at apical
layer
Stratified Squamous Epithelium

 Description
 Many layers of cells – squamous in shape
 Deeper layers of cells appear cuboidal or columnar
 Thickest epithelial tissue – adapted for protection
Stratified Squamous Epithelium
 Specific types

 Keratinized – contain the protective protein keratin
 Surface cells are dead and full of keratin
 Non-keratinized – forms moist lining of body openings
 Function
 Protects underlying tissues in
areas subject to abrasion
 Location
 Keratinized – forms epidermis
 Non-keratinized – forms lining of
esophagus, mouth, and vagina
Stratified Squamous
Epithelium
Non-keratinized vs. Keratinized
Stratified Cuboidal
Epithelium
Description
 generally two layers
of cube-shaped cells
Function
 protection
Location
 Forms largest ducts
of sweat glands
 Forms ducts of
mammary glands
and salivary glands
Stratified Columnar
Epithelium
 Description
 several layers; basal
cells usually
cuboidal; superficial
cells elongated
 Function
 protection and
secretion
 Location
 Rare tissue type
 Found in male
urethra and vas
deferens, largest
ducts of salivary
glands, nasopharynx
Transitional Epithelium
Description
 Basal cells usually
cuboidal or columnar
 Superficial cells domeshaped or squamous
Function
 stretches and permits
distension of urinary
bladder
Location
 Lines ureters, urinary
bladder and part of
urethra
Glandular Epithelium

 Ducts carry products of exocrine glands to epithelial
surface
 Include the following diverse glands





Mucus-secreting glands
Sweat and oil glands
Salivary glands
Liver and pancreas
Mammary glands
 May be: unicellular or multicellular
Exocrine Glands

 Secretions released onto body surfaces (skin) or into
body cavities
 More numerous than endocrine glands
 Secrete products into ducts
 Examples include mucous, sweat, oil, and salivary
glands
Unicellular Exocrine
Glands

 The only important unicellular glands are mucous
cells and goblet cells
 Found in epithelial linings of intestinal and
respiratory tracts
 All produce mucin
 Dissolves in water to form mucus
 Slimy protective, lubricating coating
 Mucin + water  mucus
Goblet cell (unicellular exocrine gland)
Microvilli
Secretory
vesicles
containing
mucin
Golgi
apparatus
Rough ER
Nucleus
.
Connective Tissues

Exocrine Vs. Endocrine
Glands
 Endocrine Gland Characteristics:
 Ductless glands
 Secrete substances directly into bloodstream
 Produce molecules called hormones
Which is
Which?
Connective Tissue

Most diverse and abundant tissue
Main classes
 Connective tissue proper
 Blood – Fluid connective
tissue
Supporting connective tissues
 Cartilage
 Bone tissue
Components of connective tissue:
 Cells (varies according to tissue)
 Matrix
 Protein fibers (varies according to tissue)
 Ground substance (varies according to tissue)
Major Functions of
Connective Tissue

 Binding and support
 Protecting
 Insulating
 Storing reserve fuel
 Transporting substances (blood)
Structural Elements of
Connective Tissue

 Three elements
 Ground substance
 Fibers
 Cells
 Composition and arrangement varies in different
connective tissues
Ground Substance

 Unstructured material that fills space between
cells
 Medium through which solutes diffuse between blood
capillaries and cells
 Components
 Interstitial fluid
 Cell adhesion proteins ("glue" for attachment)
 Proteoglycans
 Protein core + large polysaccharides (chrondroitin sulfate
and hyaluronic acid)
 Traps water in varying amounts, affecting viscosity of
ground substance
Ground Substance
 Interstitial (tissue) fluid within which are one or more
of the molecules listed below:
 Hyaluronic acid: a polysaccharide. Very slippery;
serves as a good lubricant for joints. Common in
most connective tissues.
 Proteoglycans: protein and polysaccharide complex.
Polysaccharides called glyocosaminoglycans
(chondroitin sulfate, keratin sulfate). Protein part
attaches to hyaluronic acid. Able to trap large
amounts of water.
 Adhesive molecules: hold proteoglycan aggregates
together. Chondronectin in cartilage, osteonectin in
bone, fibronectin in fibrous connective tissue.
 Functions as a molecular sieve through which nutrients
diffuse between blood capillaries and cells
Connective Tissue Fibers

 Three types of fibers provide support
 Collagen
 Strongest and most abundant type
 Tough; provides high tensile strength
 Elastic fibers
 Networks of long, thin, elastin fibers that allow for stretch
and recoil
 Reticular
 Short, fine, highly branched collagenous fibers (different
chemistry and form than collagen fibers)
 Branch, forming networks that offer more "give"
Extracellular Matrix - ECM
ECM has 3 major components
1. Protein fibers
2. Ground substance
3. Fluid
Protein fibers
 Collagen fibers. Composed of the protein collagen.
Strong, flexible, inelastic; great tensile strength (i.e.
resist stretch). Perfect for tendons, ligaments
 Elastic fibers. Contain molecules of protein elastin that
resemble coiled springs. Returns to its original shape
after stretching or compression. Perfect for lungs,
large blood vessels
 Reticular fibers. Formed from fine collagenous fibers;
form branching networks (stroma). Fill spaces between
tissues and organs.
"Blasts" cells
Cells

 Immature forum; mitotically active; secrete ground
substance and fibers
 Fibroblasts in connective tissue proper
 Chondroblasts in cartilage
 Osteoblasts in bone
 "Cyte" cells
 Mature form; maintain matrix
 Chondrocytes in cartilage
 Osteocytes in bone
Connective Tissue Cells
 Fibroblasts - secrete the proteins needed for fiber
synthesis and components of the extracellular matrix
 Adipose or fat cells (adipocytes) - Common in some
tissues (dermis of skin); rare in some (cartilage)
 Mast cells -Common beneath membranes; along small
blood vessels. Can release heparin, histamine, and
proteolytic enzymes in response to injury.
 Leukocytes (WBC’s) - Respond to injury or infection
 Macrophages - Derived from monocytes (a WBC).
Phagocytic; provide protection
 Chondroblasts - form cartilage
 Osteoblasts - form bone
Other Cell Types in Connective
Tissues
 Fat cells

 Store nutrients
 White blood cells
 Neutrophils, eosinophils, lymphocytes
 Tissue response to injury
 Mast cells
 Initiate local inflammatory response against foreign
microorganisms they detect
 Macrophages
 Phagocytic cells that "eat" dead cells, microorganisms;
function in immune system
Connective Tissue Proper Classifications

Loose Connective Tissue
 Areolar
 Reticular
 Adipose

Dense Connective Tissue (also called fibrous connective
tissues)
 Regular
 Irregular
 Elastic
Areolar Connective Tissue

 Support and bind other tissues
 Universal packing material between other tissues
 Most widely distributed
 Provide reservoir of water and salts
 Store nutrients as fat
 Fibroblasts
 Loose arrangement of fibers
 Ground substance
 When inflamed soaks up fluid  edema
Areolar Connective Tissue
Description

 Gel-like matrix with:
 all three fiber types (collagen, reticular, elastic) for support
 Ground substance is made up by glycoproteins also made
and secreted by the fibroblasts.
 Cells – fibroblasts, macrophages, mast cells, white
blood cells, adipocytes
 Highly vascular tissue
Areolar Connective Tissue
 Location
 Widely distributed under epithelia
 Packages organs
 Surrounds capillaries
Adipose Tissue

 White fat
 Similar to areolar but greater nutrient storage
 Cell is adipocyte
 Stores nutrients
 Scanty matrix
 Richly vascularized
 Shock absorption, insulation, energy storage
 Brown fat
 Use lipid fuels to heat bloodstream not to produce ATP
Adipose Tissue
 Description
 Closely packed adipocytes
 Have nucleus pushed to one
side by fat droplet Function
 Provides reserve food fuel
 Insulates against heat loss
 Supports and protects organs
 Location
 Under skin
 Around kidneys
 Behind eyeballs, within
abdomen and in breasts
Reticular Connective
Tissue

 Resembles areolar but fibers are reticular fibers
 Fibroblasts called reticular cells
 Supports free blood cells in lymph nodes, the spleen,
and bone marrow
Reticular Connective Tissue
 Description – network of
reticular fibers in loose
ground substance
 Function – form a soft,
internal skeleton (stroma)
– supports other cell
types
 Location – lymphoid
organs
 Lymph nodes, bone
marrow, and spleen
Dense Regular Connective Tissue

 Closely packed bundles of collagen fibers running
parallel to direction of pull
 White structures with great resistance to pulling
 Fibers slightly wavy so stretch a little
 Fibroblasts manufacture fibers and ground substance
 Few cells
 Poorly vascularized
Dense Regular Connective Tissue
Description
 Primarily parallel collagen fibers
 Fibroblasts and some elastic fibers
 Poorly vascularized
Function
 Attaches muscle to bone
 Attaches bone to bone
 Withstands great stress in
one direction
Location
 Tendons and ligaments
 Aponeuroses
 Fascia around muscles
Dense Irregular
Connective Tissue

 Same elements but bundles of collagen thicker and
irregularly arranged
 Resists tension from many directions
 Dermis
 Fibrous joint capsules
 Fibrous coverings of some organs
Dense Irregular Connective Tissue
 Description
 Primarily irregularly
arranged collagen fibers
 Some elastic fibers and
fibroblasts
 Function
 Withstands tension
 Provides structural strength
 Location
 Dermis of skin
 Submucosa of digestive
tract
 Fibrous capsules of joints
and organs
Elastic Connective
Tissue

 Some ligaments very elastic
 Those connecting adjacent vertebrae
 Many of larger arteries have in walls
Figure 4.8f Connective tissues.
Connective tissue proper: dense connective tissue, elastic
Description: Dense regular
connective tissue containing a
high proportion of elastic fibers.
Function: Allows tissue to recoil
after stretching; maintains pulsatile
flow of blood through arteries; aids
passive recoil of lungs following
inspiration.
Location: Walls of large arteries;
within certain ligaments associated
with the vertebral column; within
the walls of the bronchial tubes.
Elastic
fibers
Aorta
Heart
© 2013 Pearson Education,
Inc.
Photomicrograph: Elastic connective tissue
in the wall of the aorta (250x).
Cartilage
Characteristics:
 Firm, flexible tissue
 Contains no blood vessels or
nerves
 Matrix contains up to 80%
water
 Cell type –
 chondroblasts and chondrocytes
Types:
 Hyaline
 Elastic
 Fibrocartilage
Cartilage

Lacks nerve fibers
Up to 80% water - can rebound after
compression
Avascular
 Receives nutrients from membrane surrounding it
 Perichondrium
Hyaline Cartilage
Description
 Imperceptible collagen fibers (hyaline = glassy)
 Chodroblasts produce matrix
 Chondrocytes lie in lacunae
Function
 Supports and reinforces
 Resilient cushion
 Resists repetitive stress
Location
 Ends of long bones
 Costal cartilage of ribs
 Cartilages of nose,
trachea, and larynx Location
Elastic Cartilage
Description
 Similar to hyaline cartilage
 More elastic fibers in matrix
Function
 Maintains shape of structure
 Allows great flexibility
Location
 Supports external ear
 Epiglottis
Fibrocartilage
Description
 Matrix similar, but less firm
than hyaline cartilage
 Thick collagen fibers
predominate
Function
 Tensile strength and ability
to absorb compressive
shock
Location
 Intervertebral discs
 Pubic symphysis
 Discs of knee joint
Connective Tissue Supports and
Connects Body Parts: Basement
Membrane
 Fibrous connective tissue:

 Loose: surrounds many organs, lines cavities around blood
vessels
 Dense: tendons, ligaments, deeper layers of skin
 Elastic: surrounds stomach and bladder, maintains shape
 Reticular: internal framework of soft organs (liver) and lymphatic
system
Bone

 Also called osseous tissue
 Supports and protects body structures
 Stores fat and synthesizes blood cells in cavities
 More collagen than cartilage
 Has inorganic calcium salts
 Osteoblasts produce matrix
 Osteocytes maintain the matrix
 Osteons – structural units
 Richly vascularized
Bone Tissue
Function
 Supports and protects
organs
 Provides levers and
attachment site for
muscles
 Stores calcium and
other minerals
 Stores fat
 Marrow is site for
blood cell formation
Location
 Bones
Blood Tissue
Description
 red and white blood cells
in a fluid matrix
Function
 transport of respiratory
gases, nutrients, and wastes
Location
 within blood vessels
Characteristics
 An atypical connective tissue
 Consists of cells surrounded by fluid matrix
Blood

 Also contains white blood cells and platelets
 Fibers are soluble proteins that precipitate during
blood clotting
Muscle Tissue

 Types
 Skeletal muscle tissue
 Cardiac muscle tissue
 Smooth muscle tissue
Muscle Tissue

 Highly vascularized
 Responsible for most types of movement
 Three types
 Skeletal muscle tissue
 Found in skeletal muscle
 Voluntary
 Cardiac muscle tissue
 Found in walls of heart
 Involuntary
 Smooth muscle tissue
 Mainly in walls of hollow organs other than heart
 Involuntary
Muscle Tissue: Contracts
for Movement

 Skeletal muscle:
 Moves body parts
 Voluntary, multinucleated
 Cardiac muscle:
 Function in the heart
 Involuntary, single nucleus
 Smooth muscle:
 Surrounds hollow structures
 Involuntary, single nucleus
Skeletal Muscle Tissue
 Characteristics
 Long, cylindrical cells
 Multinucleate
 Obvious striations
 Function
 Voluntary movement
 Manipulation of
environment
 Facial expression
 Location
 Skeletal muscles attached to bones (occasionally to skin)
Cardiac Muscle Tissue
Function
 Contracts to propel blood into circulatory system
Characteristics
 Branching cells
 Uni-nucleate
 Intercalated discs
Location
 Occurs in walls of heart
Smooth Muscle Tissue
 Characteristics
 Spindle-shaped cells with
central nuclei
 Arranged closely to form
sheets
 No striations
 Function
 Propels substances along
internal passageways
 Involuntary control
 Location
 Mostly walls of hollow organs
Nervous Tissue

Nervous Tissue

Main component of nervous system
 Brain, spinal cord, nerves
 Regulates and controls body functions
Neurons
 Specialized nerve cells that generate and conduct
nerve impulses
Neuroglia
 Supporting cells that support, insulate, and
protect neurons
Nervous Tissue:
Transmit Impulses

Neuron: specialized nervous system cell:
Structural components: cell body, dendrites, axon
Glial cells: support cells to neurons
Nervous Tissue
 Function
 Transmit electrical signals
from sensory receptors to
effectors
 Location
 Brain, spinal cord, and nerves
 Description
 Main components are brain,
spinal cord, and nerves
 Contains two types of cells
 Neurons – excitatory cells
 Neuroglial - supporting cells
Lateral Surface Features – Cell Junctions

 Tight junctions (zona occludens) – close off
intercellular space
 Found at apical region of most epithelial types
 Some proteins in plasma membrane of adjacent cells
are fused
 Prevent molecules from passing between cells of
epithelial tissue
Tight Junction
Lateral Surface Features – Cell
Junctions

 Adherens junctions (zonula adherens) – anchoring
junction
 Transmembrane linker proteins attach to actin
microfilaments of the cytoskeleton and bind adjacent
cells
 Along with tight junctions, form the tight junctional
complex around apical lateral borders of epithelial
tissues
Lateral Surface Features – Cell
Junctions

 Desmosomes – two disc-like plaques connected
across intercellular space
 Plaques of adjoining cells are joined by proteins called
cadherins
 Proteins interdigitate into extracellular space
 Intermediate filaments insert into plaques from
cytoplasmic side
Desmosome
Lateral Surface Features – Cell
Junctions

 Gap junctions – passageway between two adjacent
cells
 Let small molecules move directly between
neighboring cells
 Cells are connected by hollow cylinders of protein
Gap Junction