Transcript supporting connective tissue

CHAPTER 4
TISSUES
TYPES OF TISSUES
TISSUE- groups of cells having similar
structure and function
RECALL: HISTOLOGY- study of tissues
There are 4 primary kinds of tissues:
EPITHELIAL
CONNECTIVE
NEURAL
MUSCLE
- tissues combine to form organs of the body
EPITHELIAL TISSUE
Epithelial tissue includes EPITHELIA and
GLANDS
EPITHELIA (UM)- tissues that cover
surfaces and line internal structures and
cavities of the body
GLANDS- made up of secreting cells
derived from epithelia
CHARACTERISTICS
- cells are close together
- free surface exposed to environment or some
internal passageway
- attached to underlying connective tissue by a
BASEMENT MEMBRANE
- are AVASCULAR- having no blood vessels;
nutrients must be obtained from deeper tissues
or exposed surfaces
Epithelia cover external and internal body
surfaces:
- skin
- lining of digestive, respiratory, reproductive,
and urinary tracts
Separates deep tissues from external
environment
Epithelia also line internal cavities and
passageways:
- chest cavity
- fluid-filled chambers in brain, eye, and
inner ear
- inner surfaces of blood vessels and heart
FUNCTIONS OF EPITHELIA
Four essential functions:
1. Provide physical protection- protects
exposed surfaces from abrasion,
dehydration, destruction by chemical or
biological agents
2. Control permeability- controls substances
that enter and leave the body
3. Provide sensation- detect changes in the
environment and relay info. to the nervous
system
4. Produce specialized secretions- cells that
produce secretions are called GLAND
CELLS
- EXOCRINE secretions- discharged onto
surface of the skin or other epithelial
surface (Ex: perspiration)
- ENDOCRINE secretions- released into
surrounding tissue and blood (hormones)
INTERCELLULAR
CONNECTIONS
To be an part of an effective barrier,
epithelial cells must remain firmly attached
to one another
- accomplished by CELL JUNCTIONS
3 TYPES OF JUNCTIONS:
TIGHT JUNCTIONS- cell membranes are
fused together
GAP JUNCTIONS- proteins in the
membranes bind and create channels
between the 2 cells
DESMOSOMES- cells are attached by
protein filaments
Junctions
SURFACE OF EPITHELIA
Many epithelia have MICROVILLI- small,
finger-shaped projections of the cell
membrane
- increase the surface area of the cell
Some epithelial cells have CILIA- long,
finger-shaped extensions of the cell
membrane
- beat simultaneously to move materials
across the epithelial surface
BASEMENT MEMBRANE
Epithelial cells also must remained attached
to the rest of the body
- BASEMENT MEMBRANE- lies between
the epithelium and underlying connective
tissues
- consists of a network of protein fibers (no
cells)
- it provides strength, resists distortion, and
provides a barrier
CLASSIFYING EPITHELIA
Epithelia are classified by the number of cell
layers, and the shape of the exposed cells
2 TYPES OF LAYERING:
- Simple
- Stratified
3 CELL SHAPES:
- Squamous
- Cuboidal
- Columnar
LAYERS
SIMPLE EPITHELIUM- single layer of cells
covering the basement membrane
- thin
- only found in protected areas in the bodybody cavities, interior of heart and blood
vessels
STRATIFIED EPITHELIUM- several layers
of cells above basement membrane
- found in areas subject to mechanical or
chemical stresses
- surface of skin, linings of mouth and anus
CELL SHAPE
1. SQUAMOUS- cells are thin and flat; cells
look like fried eggs (due to nuclei) laid side
by side
2. CUBOIDAL- cells appear square; nuclei
lie near the center of each cell and form a
neat row
3. COLUMNAR- also square, but taller and
more slender; nuclei crowded into narrow
band close to basement membrane
SIMPLE SQUAMOUS
EPITHELIA
- found in protected regions where
absorption takes place or where a slick,
slippery surface reduces friction
- linings of body cavities; lining of blood
vessels and heart
Simple Squamous
SIMPLE CUBOIDAL
EPITHELIA
- provides limited protection and occurs in
regions where secretion or absorption
takes place
- secrete enzymes and buffers in the
pancreas; line portions of kidneys involved
in production of urine
Simple Cuboidal
SIMPLE COLUMNAR
EPITHELIA
- provides some protection and may also
occur in areas of absorption or secretion
- lines the stomach, intestinal tract, and
many excretory ducts
Simple Columnar
PSEUDOSTRATIFIED
EPITHELIA
- columnar epithelia that appears layered
because nuclei are situated at varying
distances from the surface, but is not
actually layered
- typically has cilia
- lines nasal cavity, trachea, bronchi,
portions of male reproductive tract
Pseudostratified Ciliated
Stratified Columnar Ciliated
STRATIFIED SQUAMOUS
EPITHELIA
- found where mechanical stresses are
severe
- surface of skin, lining of mouth, tongue,
esophagus, and anus
Stratified Squamous
CONNECTIVE TISSUE
- most diverse tissues of the body
All have 3 basic components:
1. Specialized cells
2. Protein fibers
3. Ground substance- a fluid that varies in
consistency
- 2 and 3 make up the MATRIX that
surrounds the cells
- connective tissues are made up mostly of
this matrix
- never exposed to outside environment
FUNCTIONS:
- Support and protection
- Transport of materials
- Storage of energy reserves- fats
- Defense of the body- production of
antibodies
CLASSIFYING CONNECTIVE
TISSUES
3 classes of connective tissue based on the
physical properties of their matrix:
1. CONNECTIVE TISSUE PROPER- has many
types of cells and fibers surrounded by a syrupy
ground substance
- tissues underlying the skin, fatty tissue, tendons,
and ligaments
2. FLUID CONNECTIVE TISSUES- have
distinctive population of cells suspended in
a watery ground substance containing
dissolved proteins
- blood and lymph
3. SUPPORTING CONNECTIVE TISSUEScartilage and bone
- less diverse cell population, dense matrix
CONNECTIVE TISSUE
PROPER
CELL TYPES:
1. FIBROBLASTS- most abundant; produce
and maintain connective tissue fibers and
the ground substance
2. MACROPHAGES- engulf damaged cells
or pathogens
3. FAT CELLS- adipose cells; number varies
from one connective tissue to another
4. MAST CELLS- contain chemicals that are
released in times of defense
- WHITE BLOOD CELLS- produce
ANTIBODIES when tissue is damaged
3 TYPES OF FIBERS IN CONNECTIVE
TISSUE:
1. COLLAGEN FIBERS- long, straight,
unbranched; most common; strong;
flexible
2. ELASTIC FIBERS- contain protein elastin;
branched and wavy; after stretching will
return to original length
3. RETICULAR FIBERS- least common;
thinner than collagen; form branching,
interwoven network in organs
GROUND SUBSTANCE
- fills space between cells and surrounds
connective tissue fibers
- normally clear, colorless, similar in
consistency to maple syrup
CONNECTIVE TISSUE PROPER:
LOOSE CONNECTIVE TISSUE
- least specialized connective tissue in body
- contains all cells and fibers in connective
tissue proper
- forms a layer that separates the skin from
underlying muscles
- provides padding
Loose Connective
CONNECTIVE TISSUE PROPER:
ADIPOSE TISSUE
- FAT
- loose connective tissue containing large
numbers of fat cells
- loose connective tissue becomes adipose
tissue when it is dominated by FAT CELLS
- more padding; shock absorption;
insulation; energy storage
- skin of sides, buttocks; fills sockets behind
eyes
CONNECTIVE TISSUE PROPER:
DENSE CONNECTIVE TISSUE
- consists mostly of collagen fibers
TENDONS- cords of dense connective
tissue that attach skeletal muscles to
bones
LIGAMENTS- bundles of fibers that connect
one bone to another
- contain elastic fibers and collagen fibers
(stretchy)
Tendon
FLUID CONNECTIVE TISSUE:
BLOOD AND LYMPH
BLOOD and LYMPH contain distinct
collections of cells in a fluid matrix
- RED BLOOD CELLS- account for more
than ½ the volume of blood; transport
oxygen
- PLASMA- watery matrix of blood
- WHITE BLOOD CELLS- important
components of immune system
- PLATELETS- cell fragments that function in
blood clotting
SUPPORTING CONNECTIVE TISSUE:
CARTILAGE AND BONE
- provide strong framework that supports the
rest of the body
CARTILAGE
- firm gel containing embedded fibers
- only cells found within the matrix are
CHONDROCYTES, which live in small
pockets called lacunae
- cartilage is avascular
SUPPORTING CONNECTIVE TISSUE:
CARTILAGE
There are 3 major types of cartilage:
1. HYALINE CARTILAGE- most common
- tough and somewhat flexible
- connects ribs to sternum, covers surfaces
of bones within joints
2. ELASTIC CARTILAGE- contains
numerous elastic fibers that make it very
flexible and resilient
- outer ear, epiglottis (covering of larynx)
3. FIBROCARTILAGE- has little ground
substance; dominated by collagen fibers
- extremely durable and tough
- between vertebrae of spinal column- resist
compression, absorb shock
SUPPORTING CONNECTIVE TISSUE:
BONE
- also called OSSEOUS TISSUE
- volume of ground substance compared to
cartilage is very small
- matrix consists mainly of hard calcium
compounds and flexible collagen fibers
- lacunae within the matrix contain bone
cells, called OSTEOCYTES
- each bone is surrounded by a
PERIOSTEUM- covering made of fibrous
and cellular layers
Bone is constantly being remodeled
throughout life
- complete repairs can be made even after
severe damage
MUSCLE TISSUE
Muscle tissue is specialized for contraction
- muscle cell contraction involves
interactions between filaments of MYOSIN
and ACTIN, which are proteins found in
the cytoskeletons of cells
There are 3 main types of muscle tissue:
1. Skeletal
2. Cardiac
3. Smooth
MUSCLE TISSUE:
SKELETAL MUSCLE TISSUE
- contains very large, multinucleated cells
- skeletal muscles are long and slender, so
are usually called MUSCLE FIBERS
- these fibers are not capable of dividing, but
new ones are produced through the
division of stem cells in muscle tissue 
some repair is possible after an injury
MUSCLE TISSUE:
SKELETAL MUSCLE TISSUE
- because of how actin and myosin filaments
are arranged, skeletal muscle appears to
have a series of bands called
STRIATIONS
- skeletal muscle is described as STRIATED
VOLUNTARY MUSCLE because the
nervous system provides voluntary control
over its activities
MUSCLE TISSUE:
CARDIAC MUSCLE TISSUE
- found only in the heart
- cells are much smaller than skeletal
muscle fibers, and each cell usually has a
single nucleus
- also have striations
- cardiac muscle cells are interconnected at
INTERCALATED DISCS, special
attachment sites that have gap junctions
and desmosomes
- cells of cardiac muscle cannot divide;
tissue cannot regenerate
- cardiac muscle cells do not rely on nerve
activity to start a contraction; called
STRIATED INVOLUNTARY MUSCLE
MUSCLE TISSUE:
SMOOTH MUSCLE TISSUE
- found in the walls of blood vessels, around
hollow organs (urinary bladder), in layers
around respiratory, circulatory, digestive,
and reproductive tracts
- cells are small and slender, tapering to a
point at each end; each has one nucleus
- actin and myosin filaments are scattered,
so there are no striations
- cells can divide, so smooth muscle can
regenerate after an injury
- nervous system does not provide voluntary
control, so smooth muscle is known as
NONSTRIATED INVOLUNTARY MUSCLE
Neural Tissue
- also known as nerve tissue; is specialized
for the conduction of electrical impulses
from one part of the body to another
- most of this tissue is concentrated in the
brain and spinal cord
CONTAINS 2 TYPES OF CELLS:
1. NEURONS- control conscious and
unconscious thought processes
2. NEUROGLIA- provide physical support
for neural tissue, maintain the chemical
composition of the tissue fluids, defend the
tissue from infection
STRUCTURE OF A NEURON
- neurons are the longest cells in your body
(up to 1 m in length)
- limited ability to repair because are unable
to divide
- a typical neuron has a CELL BODY with a
large nucleus
- extending from the body are several
branches called DENDRITES and one
AXON
- DENDRITES receive information from
other neurons and AXONS carry that
information to other cells
TISSUE INJURY AND REPAIR
Tissue repair involves 2 related processes:
1. INFLAMMATION
- the injured area is isolated from
neighboring healthy tissue while damaged
cells, tissue components, and dangerous
microorganisms are cleaned up
- produces swelling, warmth, redness, and
pain
INFECTION- inflammation resulting from
presence of bacteria
2. REGENERATION
- damaged tissues are replaced or repaired
to restore normal functioning
- fibroblasts produce a network of collagen
fibers called SCAR TISSUE
- over time this scar tissue resumes a more
normal appearance
- regeneration is most successful in epithelia
and connective tissue
AGING
- there is a decrease in the speed and
effectiveness of tissue repair
- epithelia get thinner; connective tissue gets
more fragile
- individuals bruise more easily; bones
become brittle
- cancer rates also increase with age