THE TISSUE LEVEL OF ORGANIZATION
A.
TYPES OF TISSUES
List three characteristics of a tissue?
1.
2.
3.
Group of similar cells AND their extracellular matrices
Share a common embryological origin
Function together as a group to carry out particular functions
What determines the functions and properties of a tissue?
The functions and properties of a tissue are determined by the nature of
the cells and the extracellular matrix, if present, created by and
surrounding the cells.
List the four basic tissue types and give a brief description of each.
B.
1.
Epithelial tissues – cover the body surfaces; line hollow organs,
body cavities, and ducts; form glands
2.
Connective tissues – protect and support the body and its organs;
binds organs together; store energy reserves as fat; provide
resistance to disease in association with the immune system
3.
Muscular tissues – responsible for movement and generation of
force
4.
Nervous tissue – initiate and transmit action potentials (nerve
impulses) that help coordinate body activities
EPITHELIAL TISSUES
1.
GENERAL FEATURES
Describe the general features of epithelial tissues.
1.
2.
3.
4.
Closely packed cells with little or no extracellular material
between them
Cells arranged into continuous sheets, in either single or
multiple layers
Epithelial cells have an apical surface that is exposed to a
body cavity, lining of an internal organ, or the exterior of the
body.
Epithelial cells have a basal surface that is attached to a
basement membrane
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5.
6.
7.
8.
2.
The basement membrane (basal lamina) is a connective
tissue matrix that attaches the overlying epithelium to the
underlying connective tissue
Epithelia are avascular, meaning that they have no blood
supply. They receive their nutrition by diffusion from the
underlying connective tissues.
Epithelial have a nerve supply.
Since epithelia are subject to a certain amount of wear, tear,
and injury, they have a high capacity for mitosis.
COVERING AND LINING EPITHELIA
a.
ARRANGEMENT OF LAYERS
b.
CELL SHAPES
c.
CLASSIFICATION
Covering and lining epithelia are arranged into continuous sheets of
cells consisting of one of three layer types depending upon the
function of the tissue.
Covering and lining epithelia are also classified according to the
shape of the cells that lie on the apical surface of the epithelium.
Describe the following:
1.
simple epithelium – If the function is absorption or filtration,
or the tissue is in an area of minimal wear and tear, the cells
form a single layer, and is thus called a simple epithelium.
2.
stratified epithelium – If the tissue is in an area with a high
degree of wear and tear, then the cells are stacked into
layers, and is thus called a stratified epithelium
3.
pseudostratified epithelium – A third less common arrangement is the pseudostratified epithelium that has a single
layer of cells, so it is simple, but some cells do not reach the
apical surface, giving it a multilayered appearance.
Describe each of the following:
1.
squamous cells – squamous cells are flattened and scalelike
2.
cuboidal cells – cuboidal cells are usually cube-shaped in
cross-section, being roughly as tall as they are wide
3.
columnar cells – columnar cells are tall and cylindrical or
somewhat rectangular, and generally taller than they are
wide
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4.
d.
transitional cells – Transitional cells readily change shape
and are found where there is a continuous amount of
stretching then relaxation, such as in the urinary bladder.
The apical layer may range from squamous to cuboidal.
PHOTOMICROGRAPHS
tissue
location(s)
description
function(s)
simple squamous
lining heart (endocardium)
and blood vessels
(endothelium), lymphatic
vessels, alveoli of lungs,
glomerular capsule of
kidneys, part of serous
membranes
keratinized form forms
epidermis; nonkeratinized
forms line mouth and tongue,
pharynx, esophagus, anal
canal, and vagina
lines kidney tubules and small
ducts of many glands, covers
ovary, forms pigmented
epithelium of retina
relatively rare; lines larger
ducts of some glands and
part of the male urethra
consists of a single
layer of flattened, scalelike cells, much like a
tile floor
diffusion, osmosis, and
filtration
consists of multiple
layers flattened on
surface; cuboidal to
columnar in deepest
layers
consists of a single
layer of cube-shaped
cells, about as tall as
they are wide
consists of two or more
layers of cells, the upper
most being cuboidal in
shape
single layer of
rectangular (columnar)
cells, often has
interspersed goblet cells
protection against wearand-tear
not truly stratified; all
cells contact basement
membrane, but not all
reach apical; surface
secretion from goblet
cells, movement of
mucous across surface
by ciliary action
variable; apical cells
vary from squamous to
cuboidal depending on
degree of stretch of
organ
allows distention of
organ without causing
an increase in tension in
wall of organ
stratified
squamous
simple cuboidal
stratified cuboidal
simple columnar
pseudostratified
transitional
3.
lines GI tract from stomach to
anal canal, ducts of some
glands, gallbladder; ciliated
form lines oviducts, uterus,
central canal of spinal cord
lines much of lower
respiratory system down to
bronchiolar level; nonciliated
form may be found in some
gland ducts, epididymis, and
part of male urethra
urinary bladder, portions of
ureters and urethra
absorption and
secretion
protection
secretion and
absorption
GLANDULAR EPITHELIA
Glandular epithelium forms the secretory portions of glands. Name the
two major types of glands in the body and give a brief description of each.
1.
Endocrine glands – endocrine glands are ductless; secrete
hormones into the blood
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2.
a.
Exocrine glands – exocrine glands secrete their product(s)
either onto the apical surfaces of the cells or into ducts for
transport to the free surface.
STRUCTURAL CLASSIFICATION
List the two major structural classifications of exocrine glands and
give a brief description of each.
b.
1.
Unicellular glands – The best example of a unicellular
gland is the goblet cell. This single cell secretes its
product directly onto the free surface of many
epithelia.
2.
Multicellular glands – A multicellular gland consists of
a secreting organ found deep to the free surface and
attached to it via a duct.
FUNCTIONAL CLASSIFICATION
What is the basis for the functional classification of glands?
Functional classification is based on whether a secretion is a
product of a cell or consists of entire or partial glandular cells
themselves.
Describe each of the following:
1.
holocrine secretion – In holocrine secretion the cells
accumulate secretory product in their cytosol, die, and are
discharged with their contents as the secretion.
2.
merocrine secretion – In merocrine (eccrine) secretion the
cells form a secretory product, store it in the cytoplasm in
secretory vesicles, and release it by exocytosis.
3.
apocrine secretion – In apocrine secretion vesicles with
product accumulate in the apical portion of the cells. That
portion pinches off from the rest of the cell to form the
secretion.
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C.
CONNECTIVE TISSUES
1.
GENERAL FEATURES
Name the three basic elements of all connective tissues.
1.
2.
3.
cells
ground substance (ground substance is a more or less
homogeneous, amorphous, water-based background
substance in which the specific differentiated elements of a
connective tissue are suspended)
fibers
Name the three basic fiber types of the connective tissues.
1.
collagen
2.
elastin
3.
reticular fibers
What is matrix?
Matrix is ground substance embedded with fibers that separate the
cells.
2.
CLASSIFICATION
Mature (adult) connective tissues are classified into five categories. List
each of them, give their subdivisions, and the primary cell type of each.
1.
loose connective tissues
areolar tissue (fibroblast)
adipose tissue (adipocyte)
reticular tissue (fibroblast)
2.
dense connective tissues
dense regular connective tissues (fibroblast)
dense irregular connective tissues (fibroblast)
elastic connective tissues (fibroblast)
3.
specialized connective tissues
cartilage
hyaline cartilage (chondrocyte)
elastic cartilage (chondrocyte)
fibrocartilage (chondrocyte and fibroblast)
bone (to be discussed later)
blood (to be discussed later)
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3.
PHOTOMICROGRAPHS
tissue
location(s)
description
function(s)
areolar
papillary dermis of skin,
hypodermis, mucous
membranes, blood vessels,
nerves, and around body
organs (i.e. everywhere)
strength, elasticity, and
support
adipose
hypodermis; around heart,
kidneys, and eyes; yellow
bone marrow; around joints
reticular
stroma of liver, spleen, lymph
nodes; red bone marrow;
basement membranes
tendons, aponeuroses, and
most ligaments
loosely woven fibers
embedded in ground
substance; many
different cell types
wander through;
fibroblasts form basic
tissue
adipocytes that store
fats, forming a
characteristic “signet
ring” appearance
net work of very short
interlacing collagen
fibers and fibroblasts
collagen fibers arranged
in parallel bundles, with
fibroblasts scattered
between
collagen fibers randomly
arranged and
fibroblasts, forming a
sheet
elastic fibers that branch
freely, forming sheets or
ligaments
provides extensibility
and elasticity to various
organs that must be
stretched
resists compressive
forces, provides smooth
surfaces for articulation
at synovial joints
support, fusion
(between pubic bones
and between vertebrae),
deepening of shoulder
and knee joints
allows structure to be
semi-rigid and
extensible; structure can
return to resting shape
support, protection,
storage, provides levers
for movement; provides
for blood cell formation
transport of gases,
immune function, blood
clotting
dense regular
dense irregular
elastic
hyaline cartilage
fibrocartilage
dense fascia, reticular dermis,
perichondrium, periosteum,
joint capsules, dura mater,
membrane capsules, heart
valves
lung, elastic arteries, trachea
and bronchial tree, true vocal
cords, vertebral ligaments,
suspensory ligament of penis
articular surfaces of bones;
anterior ribs; nose, parts or
larynx, trachea, and bronchial
tree; embryonic skeleton
pubic symphysis,
intervertebral discs, menisci
of shoulders and knees
elastic cartilage
epiglottis, external ear,
auditory tubes
bone
comprises the bones of the
skeleton
blood
within blood vessels and
heart
Chondrocytes
embedded in cartilage
matrix rich in collagen
fibers
consists of scattered
Chondrocytes with
hyaline cartilage matrix
among bundles of
collagen fibers
Chondrocytes
embedded in cartilage
matrix rich in network of
elastic fibers
osteocytes embedded in
a mineralized matrix of
collagen fibers and
ground substance
formed cellular
elements suspended ina
liquid matrix (plasma)
provide insulation,
energy storage,
protection from
mechanical injury
form framework of
organs, binds together
smooth muscle cells
provides strong
attachments between
parts
strength, support, and
protection
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D.
MEMBRANES
What is a membrane?
An epithelial membrane is formed by a the combination of an epithelium
and an underlying connective tissue layer.
Name the three true membranes and the one false membrane of the body.
mucous membrane (mucosa)
serous membrane (serosa)
cutaneous membrane (skin or integument)
synovial membrane (not a true membrane because there is no epithelium)
1.
MUCOUS MEMBRANES
In general, where are mucous membranes found?
Mucous membranes line body cavities that open directly to the
external environment.
What is the function of the epithelial layer?
The epithelial layer secretes mucous to protect the epithelium by
lubricating it and trapping harmful agents.
Specifically, what body parts are lined by a mucosa?
Mucosae are found lining the respiratory tract, the digestive tract,
and the genitourinary tract.
2.
SEROUS MEMBRANES
In general, where are serous membranes found?
Serous membranes line body cavities that do not open to the
exterior of the body and cover the external surfaces of the viscera.
What are the parietal and visceral layers of a serosa?
The portion of the serosa attached to the body wall is called the
parietal layer and the portion attached to an organ is called the
visceral layer.
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What is serous fluid, where is it found, and what does it do?
Between the layers of the serosa is a small amount of serous fluid
that lubricates the two layers and allows the organs to move freely
within the cavity
3.
CUTANEOUS MEMBRANE
The cutaneous membrane (epidermis) will be discussed with the skin.
4.
SYNOVIAL MEMBRANE
Where are synovial membranes located?
They line the joint cavity of synovial (freely movable) joints.
Why are they not considered to be true membranes?
Synovial membranes are not true membranes because they do not
contain an epithelial layer.
What is the structure of a synovial membrane?
Synovial membranes are composed of areolar connective tissue
with elastic fibers and varying amounts of adipose tissue. The cells
are synoviocytes that secrete synovial fluid.
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