Transcript Chapter 3--Tissues - Tri-County Technical College

Chapter 3--Tissues
Biology 110
Tri-County Technical College
Pendleton, SC
Definition and Types


Tissue is group of cells that are “similar” in
structure and function
There are four primary tissue types in the
human body:




Epithelium
Connective
Nervous
Muscle
Epithelial Tissue Function



Is the lining, covering, and glandular tissue
of the body
Functions include: Protection, absorption,
filtration, and secretion
Epithelium has some special characteristics


Cells fit close together to form continuous
sheets
Neighboring cells bound together by cell
junctions including desmosomes and tight
junctions
Epithelial Functions, ctd.

Membranes all have ONE free (unattached)
surface or edge




This apical surface exposed to body’s exterior
or to cavity of internal organs
May be slick/smooth or covered with
microvilli or cilia
Lower surface rests on BASEMENT
MEMBRANE-structureless material secreted
by cells
Epithelial cells have NO blood supply of their
own (avascular)-depend on diffusion from
capillaries in underlying connective tissue
Classifying Epithelium (layering)





Each epithelium is given two names
First indicates relative number of cell
layers it has
Second describes the shape of its cells
SIMPLE is composed of only ONE layer of
cells
STRATIFIED is composed of MORE than
one cell layer

Stratified named for cells at free surface and
NOT those resting on basement membrane
Epithelium Classification, ctd.





SQUAMOUS epithelium cells are flattened
like fish scales
CUBOIDAL epithelium cells are cubeshaped like dice
COLUMNAR epithelium cells are shaped
like columns
Terms describing arrangement and shape
are combined to describe epithelium fully
Use arrangement name first and shape
name second
Simple Squamous



Single layer of thin squamous cells resting
on basement membrane
Usually forms membranes where filtration
or exchange of substances by rapid
diffusion occurs
Composes air sacs of lungs, walls of
capillaries, and the SEROUS
MEMBRANES (serosae), the slick
membranes that line ventral body cavities
and cover organs in that cavity
Simple Cuboidal


ONE layer of cuboidal cells resting on BM
Common in glands and their ducts


Salivary glands and pancreas for examples
Forms wall of kidney tubules and covers
surface of the ovaries
Simple Columnar






ONE layer of columnar cells resting on BM
Tall cells that fit closely together
Specialized for absorption and secretion
GOBLET CELLS often found in this
epithelium type—produce lubricating
mucus
Line entire digestive tract from stomach to
anus
Epithelial membranes that line body
cavities open to body exterior called
MUCOSAE or mucous membranes
Pseudostratified Columnar






All pseudostratified columnar epithelium
cells rest on basement membrane
Some shorter than others and their nuclei
appear at different heights above BM
Results in psuedo (false) impression that its
stratified
Specialized for absorption and secretion
Ciliated variety lines most of respiratory
tract
Mucus produced by GC traps dust/debris
and cilia propel mucus upward away from
lungs
Stratified Squamous





Most common stratified epithelium in body
Cells close to edge are squamous whereas
cells close to BM are cuboidal/columnar
Usually consists of several layers of cells
Found in sites that receive abuse or friction
Esophagus, mouth, and outer portion of
skin
Stratified Cuboidal & Columnar





Stratified Cuboidal usually 2 layers thick
Found along ducts of sweat glands and
larger ducts of mammary glands
Stratified Columnar basal cells vary in size
and shape
Provides protection along portions of
pharynx, epiglottis, urethra, anus, salivary
gland ducts, and along few large excretory
ducts
Both are fairly rare in the human body
Transitional Epithelium






Is highly modified stratified squamous epithelium
that forms lining of only few organs
Found in urinary bladder, ureters, and part of
urethra
Found where “stretching” is necessary
Basal cells are cuboidal/columnar while those at
surface vary in appearance
Ability of cells to “slide past” each other and
change shape allows “stretching”
Ureter wall/urethra/urinary bladder…enough said
Glandular Epithelium

Gland consists of one or more cells that
make/secrete particular product (secretion)



Usually proteins in aqueous fluid
Two major types of glands form from
epithelial sheets
ENDOCRINE glands lose connection to
surface; called “ductless glands”


Their secretions (hormones) diffuse directly
in blood vessels that run through the glands
THYROID, ADRENALS, PITUITARY, ETC.
Glandular Epithelium, ctd.




EXOCRINE glands retain their ducts and
their secretions empty through ducts to
epithelial surface
Glands located both internally/externally
Sweat and oil glands
Liver and pancreas (be careful with
pancreas, it also has endocrine function)
Connective Tissue Overview



Connects body parts and is most abundant
and widely distributed of tissue types
Connective tissue has some common
characteristics
Most are well vascularized (good blood
supply) but there are exceptions



Tendons and ligaments have poor blood
supply
Cartilages are avascular
As result, these structures heal very slowly
(if at all) when injured
CT Overview, ctd.

Connective tissues composed of many different
cell types plus varying amounts of nonliving
substances found outside cells called
EXTRACELLULAR MATRIX


Matrix produced by CT cells and secreted to
exterior



Is what makes connective tissue so different
May be liquid, semisolid/gel-like, or very hard
Because of EC matrix, CT able to stand stretching
and other abuses (abrasion) that no other tissue
could endure
As always, there are exceptions
CT Overview, ctd.




Fat tissue (adipose) mostly cells with soft
EC matrix
Bone and cartilage tissue has very few cells
and large amounts of hard EC matrix which
makes them very strong
Various types/amounts of fibers deposited
in and form part of EC matrix
Collagen (white) fibers, Elastic (yellow)
fibers, and Reticular (fine collagen) fibers

Made by CT cells and secreted to outside
CT Overview, ctd.




Connective tissue performs many
functions: Protecting, Supporting, &
Binding together other body tissues
All CT consist of living cells surround by a
matrix
Their major differences reflecdt fiber type
and number of fibers in their matrix
From the overview to the specific-let us
discuss the Connective Tissue
Bone Tissue




Often called “osseous tissue”
Composed of bone cells in cavities called
LUCUNAE
Surrounded by layers of very hard matrix
containing calcium salts and large numbers
of collagen fibers
Because of this hardness, bone has
exceptional ability to protect/support other
body organs
Hyaline Cartilage





Less hard and more flexible than bone
Hyaline cartilage is most widespread
Has abundant collagen fibers hidden by
rubbery matrix with blue-white appearance
Forms supporting structures of larynx
(voice box), attaches ribs to breastbone,
and covers ends of bones where they form
joints
**skeleton of fetus made of hyaline
cartilage
More Cartilage…Yeah!!

ELASTIC cartilage found where structure
with elasticity desired


Supports external ear
FIBROCARTILAGE highly compressable

Forms cushionlike disks between vertebrae of
spinal column
Dense Fibrous Tissue






Also known as Dense Connective Tissue
Has collagen fibers as main matrix
Crowded between collagen fibers are rows of
FIBROBLASTS (fiber-forming cells)
Forms strong, ropelike structures such as tendons
and ligaments
TENDONS attach skeletal muscles to bone
Ligaments connect bone to bone at joints


More stretchy/contains more elastic fibers
Makes up lower layers of skin (arranged in
sheets)
Areolar Tissue




Also known as Loose Connective tissue &
is most widely distributed CT variety
Soft & pliable tissue that cushions/protects
body organs it wraps
Functions as universal packing tissue and
“glue” because it helps hold internal organs
together and in their proper positions
Soft layer of areolar tissue (LAMINA
PROPRIA) underlies all mucous
membranes
Areolar Tissue, ctd.




Fluid matrix contains all types of fibers in
loose network
Provides reservoir of water and salts for
surrounding tissues
**Essentially all body cells obtain their
nutrients from and release their wastes into
this “tissue fluid”
When body region inflamed, areolar tissues
in area soak up excess fluid like sponge
and area swells and becomes puffy

This condition is called EDEMA
Adipose Tissue




Is an areolar tissue in which fat cells predominate
Glistening drop of fat occupies most of cell’s
volume
Often called “signet ring cells”
Forms subcutaneous tissue beneath skin




Insulates body
Protects some organs individually
Kidneys surrounded by capsule of fat; cushions
eyeballs in sockets
Fat “depots” in body (hips/breasts) store fat (fuel)
Reticular Connective Tissue




Consists of delicate network of interwoven
reticular fibers associated with RETICULAR
CELLS which resemble fibroblasts
Limited to certain sites
Forms STROMA (bed/mattress) which is internal
supporting framework
Stroma can support many free blood cells (mostly
lumphocytes) in lymph organs such as lymph
nodes, spleen, and bone marrow
Blood Connective Tissue




Blood (vascular tissue) composed of blood
cells surrounded by nonliving matrix
(blood plasma)
Fibers are soluble protein molecules that
become visible only during blood clotting
Transport vehicle for cardiovascular system
Carries nutrients, wastes, respiratory gases,
and many other substances throughout
body
Nervous Tissue





Functional unit is the NEURON
Neurons receive and conduct electrochemical
impulses from one part of body to another
IRRITABILITY and CONDUCTIVITY are two
major functions of nervous tissue
Neurons may be quite long (up to 3 feet) because
cytoplasm may be drawn out into extensions
Neurons along with supporting cells (called glial
or neuroglial cells that insulate, support, and
protect neurons) make up structures of nervous
system

Brain, spinal cord, and nerves
Muscle Tissue Overview


Highly specialized to contract (shorten)
Muscle cells elongated to provide long axis
for contraction


Called muscle “fibers”
Three types of muscle tissue

SKELETAL, CARDIAC, and SMOOTH
Skeletal Muscle, and more…



Packaged by connective tissue sheets into
organs called skeletal muscles which are
attached to skeleton
Can be controlled voluntarily and form
flesh of body (word of caution here)
When contract, they pull on bones or skin



Result is body movement of change in facial
expressions
Cells are long, cylindrical, and
multinucleate
Have obvious striations (stripes)
That’s the beat of a heart…





Cardiac muscle found only in the heart
Has striations, uninucleate, branching cells
that fit tightly together at junctions called
INTERCALATED DISKS
Contain gap junctions that allow ions to
free pass from cell to cell
Results in rapid conduction of exciting
electrical impulse across heart
Involuntary/not under conscious control
Smooth Muscle Tissue






Also called VISCERAL muscle because NO
striations are visible
Spindle shaped cells with single nucleus
Found in walls of hollow organs (stomach,
bladder, uterus, and blood vessels)
When contracts, cavity of organ constricts or
dilates so that substances are propelled through
organ along specific pathway
Contracts much more slowly than skeletal/cardiac
PERISTALSIS is wavelike motion that keeps
food moving through small intestine (typical of
smooth muscle tissue)
Tissue Repair





Tissue injury stimulates body’s inflammatory and
immune responses and healing process begins
almost immediately
Tissue repair (wound healing) occurs in 2 major
ways
REGENERATION is replaced of destroyed tissue
by the same kind of cell
FIBROSIS involves repair by dense (fibrous) CT;
i.e., formation of SCAR tissue
Which of these occurs depends on TYPE of tissue
damaged and SEVERITY of injury
Tissue Repair, ctd.




Clean cuts (incisions) heal more
successfully that ragged tears (lacerations)
Tissue injury triggers series of events
CAPILLAIRES become very permeable
allowing fluids rich in clotting proteins to
seep into injured area
Leaked clotting proteins form clot,
stopping blood loss, holds edges of wound
together, and seals off damaged area

Prevents bacteria (other harmful stuff) from
spreading to surrounding tissues
Tissue Repair, ctd.


Clot exposed to air, dries and hardens to
form scab
GRANULATION tissue next phase



Delicate, pink tissue composed largely of
capillaries that grow into damaged area
Capillaries are delicate and bleed freely
Also contains phagocytes and connective
tissue cells (fibroblasts) that synthesize
collagen fibers (scar tissue) to permanently
bridge the gap
Tissue Repair, ctd.




Surface epithelium begins to regenerate
and cover granulation tissue beneath scab
Final result is fully regenerated surface
epithelium that covers area of fibrous scar
Scar is either invisible or visible as white
line depending on severity of wound
Epithelial tissues such as skin epidermins,
mucous membranes, and fibrous
connective tissue regenerate beautifully
Tissue Repair, ctd.



Skeletal muscle regenerates poorly, if at all
Cardiac and nervous tissue replaced only
by SCAR tissue
Scar tissue is strong but lacks flexibility of
more normal tissues


Is unable to perform normal functioning of
tissue it replaces
May hamper functioning of an organ
(bladder, heart, etc.)