Transcript Tissues.ppt

Tissues
Tissues are closely associated
cells that are similar in structure
and perform a common function.
Principle Types of Tissue
There are four primary tissue
types that interweave to form the
fabric of the body.
Principle Types of Tissue
1. Epithelial tissue:
Primary function is
protection
2. Connective tissue:
Primary function is support
3. Muscle:
Primary function is
movement
4. Nervous:
Primary function is control
Developmental Aspects of
Tissue
Embryonic and Fetal
Development
Primary Germ Layer
Formation
Development of Tissues Through
Adolescents
By the end of the second month of
development, the primary tissues have
developed and most organs are laid down.
Most tissue cells, except neurons,
continue to undergo mitosis until body size
is achieved, after which only epithelial and
connective tissues are routinely mitotic.
Effects of Aging on Tissue
With increasing age, epithelial sheets
become thin and more easily breached.
The amount of collagen in the body
decreases, making tissue repair less
efficient. Bone, muscle and nervous tissue
begin to atrophy.
Epithelial Tissue
Epithelial tissue, or epithelium, is subdivided
into two types:
1. membranous (covering or lining)
epithelium and
2. glandular epithelium
Functions of Epithelial Tissue
1.
2.
3.
4.
Protection
Absorption
Filtration
Secretion
Glandular epithelium’s chief function is
secretion.
Special Characteristics of
Epithelia
1. Cellularity: composed almost entirely of
cells
2. Specialized Contacts: fit close together
to form continuous sheets; bound by tight
junctions and desmosomes
3. Polarity: has one free (apical) surface;
the portion exposed to the body exterior
or the cavity of an internal organ
Special Characteristics of
Epithelia
4. Avascular: it has no blood vessels within
it; receives nourishment by diffusion of
substances from blood vessels in the
underlying connective tissue
5. Regenartion: able to replace cells rapidly
by mitotic division
Special Characteristics of
Epithelia
6. Basement Membrane: reinforces the epithelial
sheets, helping it to resist stretching and tearing,
defines the space that may be occupied by
epithelial cells; made up of a thin supporting
basal lamina (nonliving adhesive material) which
separates epithelial tissue from the underlying
connective tissue (secretes a similar
extracellular material called reticular lamina);
these two together for the basement membrane
Classification of Epithelia
Membranous Epithelium
Criteria for Classification
•
Cellular Shape: Irregularly polyhedral (many-sided) in
a cross section, differ in cell height; 4 common shapes
are:
–
–
–
–
Squamous: flattened and scale-like; nucleus is thin and
flattened
Cuboidal: as tall as they are wide; nucleus is spherical
Columnar: tall and column shaped; nucleus is elongated from
top to bottom
Pseudostratified columnar: one layer of oddly shaped
columnar cells that don’t always extend to the surface of the
membrane; some nuclei are located toward the top and some
toward the bottom
Membranous Epithelium
Criteria for Classification
• Cellular Arrangement (layers)
a. simple epithelia: composed of a single
layer of cells
b. stratified epithelia: multiple cell layers
stacked on top of each other
c. transitional epithelia: differing cell shapes
in a stratified, or layered sheet
Simple Epithelium
• Simple Squamous
Epithelium: function is
filtration and diffusion;
single layer of thin
flattened cells, like floor
tiles; nucleus is broad
and thin; lines air sacs of
lungs, forms walls of
capillaries, lines the
inside of the blood and
lymph vessels, and
covers the surfaces of the
pleura, pericardium, and
peritoneum
Simple Epithelium
• Simple Cuboidal
Epithelium: function is
secretion and absorption;
single layer of cubeshaped cells; centrally
located, spherical
nucleus; covers the
ovaries and lines most of
the kidney tubules and
ducts of certain glands
such as salivary, thyroid,
pancreas, and liver
Simple Epithelium
Simple Columnar Epithelium:
specialized for protection,
secretion, and absorption;
single layer of elongated cells;
nucleus is located at the same
level near the basement
membrane; lines the uterus
and most organs of the
digestive tract; flask-shaped
glandular cells called “goblet
cells” are scattered among
columnar cells of this tissue
and secrete a protective
mucus onto the tissue’s
surface
Simple Epithelium
Pseudostratified
Columnar Epithelium:
appear stratified or
layered, but are not;
possess cilia and goblet
cells; one nucleus that is
located at two or more
levels within the cells;
lines the passages of
respiratory and
reproductive systems
Stratified Epithelium: two or more cell layers;
major function is protection because they are
considerably more durable
• Stratified Squamous
Epithelium: many cell
layers make this tissue
thick; cells reproduce
in the deeper layer
pushing older ones
farther and farther
outward; forms the outer
layer of skin (epidermis),
lines the mouth, throat,
vagina, and anal canal
Stratified Epithelium
Stratified Cuboidal
Epithelium: consist of
two to three layers that
line a lumen (space within
a tubular structure); lines
the larger ducts of the
mammary glands, sweat
glands, salivary glands,
and pancreas; also lines
developing ovarian
follicles and seminiferous
tubules
Stratified Epithelium
Stratified Columnar
Epithelium: layers of
cells; superficial cells
are elongated, while
the basal layers
consist of cubeshaped cells; found in
male urethra and vas
deferens, and in parts
of the pharynx
Stratified Epithelium
Stratified Transitional
Epithelium: specialized
to change in response to
increased tension; forms
the inner lining of urinary
bladder and the
passageways of the
urinary system; the walls
consist of several layers
of cuboidal cells, when
distended they flatten
Covering and Lining Epithelia
• Endothelia: simple epithelial
sheet composed of a single
layer of squamous cells
attached to a basement
membrane; provides a slick,
friction-reducing lining in all
hollow circulatory system
organs (lymphatic vessels,
blood vessels, and the heart;
capillary walls consist only of
endothelia because its
extreme thinness encourages
the exchange of nutrients and
wastes across capillary walls
Covering and Lining Epithelia
•
Mucous Membrane: epithelial membranes that line body cavities
that open to the exterior, such as those of the digestive,
respiratory, and urogenital tracts; they are “wet”, or moist
membranes bathed by secretions or, in the case of the urinary
mucosae, urine
•
Cutaneous Membrane: your skin; exposed to air and is a dry
membrane
•
Serous Membrane: moist membranes found in closed ventral
cavities; parietal layer that lines the cavity wall and visceral layer
that covers the outer surface of the organs within the cavity; each
layer secretes serous fluid which lubricates the facing surfaces of
the parietal and visceral layers, so that they slide across each
other; named according to site and specific organ association
Glandular Epithelium
Glandular Epithelia is made up of one or more
cells that produce and secrete a particular
product called a secretion (aqueous fluid,
containing proteins). Secretion can refer to both
the process of secretion formation and the
release of the product of glandular activity.
Glandular epithelium are classified according to
the route of secretion and the general function of
their products, and as unicellular or multicellular
on the basis of their structure.
Glandular Epithelium
• Endocrine Glands:
lose their ducts and
are called ductless
glands; produce
hormones which
they secrete directly
into the extracellular
space; not all
endocrine glands are
derivatives of
epithelia
Glandular Epithelium
• Exocrine Glands: more
numerous than endocrine
glands; secrete their
products through a duct
onto body surfaces or into
body cavities; include
sweat glands, salivary
glands, the liver (which
secretes bile), the
pancreas (which
synthesizes digestive
enzymes), mammary
glands, mucous glands,
and many others
Exocrine Glands
• Unicellular Glands: single
cells interposed in epithelial
tissue between cells with other
functions; have no ducts; all
such glands produce mucin ( a
complex glycoprotein that
dissolves in water and forms a
slimy coating (mucus) that
protects and lubricates
surfaces; includes the goblet
cells of the intestinal and
respiratory mucosae as well as
mucin-producing cells found in
other body regions
Exocrine Glands
Multicellular Glands: classified according to the
composition of their secretions and the method
by which secretion occurs
1. Merocrine Glands: secrete watery, protein rich
serous fluid by exocytosis ( salivary glands,
pancreatic glands, certain sweat glands)
2. Apocrine Glands: lose small portions of their
cytoplasm as fluid –filled packets (mammary
glands, certain sweat glands)
3. Holocrine Glands: the whole cell lyses during
secretion (sebaceous glands)
Exocrine Glands
Merocrine Gland
Apocrine Gland
Holocrine Gland
Connective Tissue
Connective tissue is found throughout the
body. It is the most abundant and widely
distributed of all the tissues.
Connective Tissue
Chief subclasses include:
1. Connective tissue proper
2. Cartilage
3. Bone
4. Blood
Connective Tissue
Major functions include:
1. Binding
2. Support
3. Protection
4. Insulation
5. Transportation of substances within the
body
Common Characteristics of
Connective Tissue
Common Origin: arise from mesenchyme (an
embryonic tissue derived from the mesoderm germ
layer
Degrees of Vascularity: cartilage is avascular; dense
connective tissue poorly vascularized; other types
have a rich supply of blood vessels
Matrix: composed largely of nonliving extracellular
matrix, which separates the living cells of the
tissue; makes connective tissue able to bear
weight, withstand great tension, and endure
abuses such as physical trauma and abrasions
Structural Elements of
Connective Tissue
Connective tissues are placed into different
categories or types according to the
structural characteristics of the intercellular
material. The consistency of the
intercellular material varies from fluid to
semisolid to solid.
Fibers
• Collagenous: thick threads made from
molecules of the protein collagen; grouped in
long, parallel bundles; they are flexible but only
slightly elastic; they resist considerable pulling
force (tendons that connect muscle to bone);
tissues containing abundant fibers are called
dense tissue which appear white and are
referred to as white fibers.
• Elastic: composed of a protein called elastin;
fibers branch, forming complex networks; stretch
easily and can resume their original lengths and
shapes (vocal chords); yellow fibers
• Reticular: very thin collagenous fibers; highly
branched and form delicate supporting networks
in a variety of tissues
Cells
Resident Cells
1. Fibroblasts: most common; large and usually starshaped; produce fibers by secreting proteins into the
matrix around them
2. Mast Cells: large and widely distributed; located
near blood vessels; release heparin, which prevents
blood clotting, and histamine, which promotes
reactions associated with inflammation and allergies
Wandering Cells
1. Macrophages: almost as numerous as fibroblasts;
specialized to carry on phagocytosis; move about
and function as scavengers and defense cells that
clear foreign particles from tissue
Types of Connective Tissue
1. Embryonic Connective Tissue: Mesenchyme
a. Mesenchymal Tissue: first definitive tissue formed
from the mesoderm germ layer; arises during the
early weeks of development and eventually
differentiates into all other connective tissue; starshaped cells and a fluid ground substance
containing fine fibrils
b. Mucous Connective Tissue: temporary tissue;
derived from mesenchyme and similar to it; appears
In the fetus in very limited amounts (ex. Wharton’s
jelly, which supports the umbilical cord)
Types of Connective Tissue
2. Connective Tissue Proper:
Loose Fibrous
Areolar: soft and pliable;
serves as a type of
universal packing material
between other tissues;
the most widely
distributed in the body;
separates muscles, wraps
small blood vessels and
nerves, surrounds glands,
and forms the
subcutaneous tissue;
present in all mucous
membranes
Loose Fibrous
Adipose: (fat); develops when
certain cells store fat in
droplets within their
cytoplasm and enlarge; when
such cells are so numerous
that they crowd other cell
types, adipose tissue results;
cushions joints and some
organs (kidneys), insulates
beneath the skin, stores
energy in fat molecules;
located beneath the the skin,
inspaces between muscles,
around kidneys, behind
eyeballs, in certain
abdominal membranes, on
surface of the heart, and
around certain joints
Loose Fibrous
Reticular: delicate network
of interwoven reticular
fibers; limited to certain
sites such as: forms the
stroma, or internal
supporting framework of
lymph nodes, spleen,
bone marrow, and liver;
some are fibroblast-like,
others differentiate into
phagocytic
macrophages
Dense Fibrous
Regular: primarily parallel
collagen fibers, a few elastin
fibers, and major cell type is
the fibroblast; located in the
tendons, most ligaments, and
aponeuroses (sheet-like
tendon that separates
muscle from muscle);
attaches muscle to bone or
to muscles, bone to bone;
withstands great tensil stress
when pulling force is applied
in one direction
Dense Fibrous
Irregular: primarily irregularly
arranged collagen fibers,
some elastin, major cell type
is fibroblast; located in the
dermis of the skin,
submucosa of the digestive
tract, fibrous capsules of
organs and of joints, fascia
(white sheets that surround
the muscle); able to
withstand tension exerted in
many directions; provides
structural strength
Dense Fibrous
Elastic: predominant fiber
type is elastin; located
in the walls of the aorta,
some parts of the
trachea and bronchi,
forms the vocal cords
and the ligamenta flava
connecting the
vertebrae; yields easily
to a pulling force or
pressure and then
recoils to its original
length
Cartilage
partly rigid, partly flexible connective tissue;
provides support frameworks and attachements;
protects underlying tissues and forms structural
models for many developing bones; composed
of collagenous fibers embedded in a gel-like
ground substance; chondrocytes (cartilage cells)
occupy small chambers called lacunae and are
completely surrounded by matrix; avascular and
devoid of nerve fibers; different types of matrix
distinguish three types of cartilage
Cartilage
Hyaline: most common
type; very fine
collagenous fibers in its
matrix and looks
somewhat like white
plastic; found on the
ends of bones in many
joints, in the soft part of
the nose, and in
supporting rings of the
respiratory passages;
important in
development of most
bones
Cartilage
Fibrocartilage: very tough
tissue containing many
collagenous fibers;
shock absorber for
structures subjected to
pressure; forms pads
(intervertebral diswks)
between the individual
parts of the backbone,
cushions bones in the
knees and in the pelvic
girdle
Cartilage
Elastic: dense network
of elastic fibers;
more flexible than
hyaline cartilage;
provides framework
for the external ears
and parts of the
larynx
Bone (Osseous Tissue)
hard, calcified matrix
containing many collagen
fibers; very well
vascularized; supports and
protects, provides levers for
muscles to act on, stores
calcium and other minerals
and fat, marrow inside
bones is site for blood cell
formation (hematopoiesis);
contains osteocytes (bone
forming cells)
Blood (Vascular Tissue)
red and white blood
cells in a fluid matrix
(plasma); contained
within blood vessels;
transport of
respiratory gases,
nutrients, wastes,
and other
substances
Muscle Tissue
•
•
•
•
•
highly cellular
well vascularized
elongated shape
specialized myofilaments, composed of
contractile proteins actin and myosin
responsible for most types of body
movement
Muscle Tissue
Skeletal Muscle: long,
cylindrical,
multinucleated cells with
obvious striations;m
located in skeletal
muscles attached to
bones or occasionally to
skin; voluntary control;
functions in locomotion,
manipulation of
environment, facial
expressions
Muscle Tissue
Cardiac Muscle: branching,
striated generally
uninucleated cells that
fit together tightly at
unique junctions called
intercalated discs;
located only in the walls
of the heart; propels
blood into circulation as
it contracts; involuntary
control
Muscle Tissue
Smooth Muscle: spindleshaped cells with
central nuclei; cells
arranged closely to form
sheets; no striations;
mostly in the walls of
hollow organs; propels
substances or objects
(foodstuff, urine, a baby)
along internal passages;
involuntary control
Nervous Tissue
makes up the nervous system:
the brain, spinal cord, and
nerves that conduct
impulses to and from the
various body organs;
branching cells, cytoplasmic
extensions, that may be
quite long, extend from the
nucleus-containing cell
body; transmits electrical
signals from sensory
receptors and to effectors
(muscles and glands) which
control their activity; types of
cells:
Nervous Tissue
types of cells:
Neurons: highly
specialized cells that
generate and
conduct nerve
impulses; branching
cells cytoplasmic
extensions allow
conduction of
electrical impulses
over substantial
distances
Nervous Tissue
types of cells:
Neuroglial Cells:
nonconducting cells
that support,
insulate, and protect
the delicate neurons
Tissue Repair
The skin and mucosae, the ciliary activity of
epithelial cells lining the respiratory tract,
and strong acid (chemical barrier)
produced by stomach glands represent
three defenses exerted at the local tissue
level.
Tissue Repair
When injury does occur it stimulates the
body’s inflammatory and immune
responses.
Replacement of destroyed tissue by
proliferation of the same kind of cells is
called regeneration.
Tissue Repair
Proliferation of fibrous
connective tissue,
that is scar tissue, is
called fibrosis.
Tissue Repair
Organization is the process during which the temporary
blood clot is replaced by the ingrowth of granulation
tissue (a delicate pink tissue composed of several
elements:
1. extremely permeable capillaries bud from undamaged
capillaries and enter the damaged area; laying down a
new capillary bed
2. scattered macrophages and large, immature fibroblast
synthesize new collagen fibers to permanently bridge
the gap
3. macrophages digest and remove the original blood clot
4. secretes bacterium-inhibiting substances
5. granulation tissue becomes scar tissue