ZOOLOGY Laboratory Reviewer
The Microscope
Coarse adjustment knob - Causes the stage to
move upward or downward at a fast rate and is
used to focus on a specimen.
Arm - Serves as a handle to carry the
microscope
Condenser - Concentrates light onto specimen
Eyepiece (ocular) - Contains a lens at the top
of it
Iris/diaphragm - Increases the light intensity
Nosepiece - Part of which the objective lenses
are attached
Objective lens - After the light passes through
the specimen, it next enters this lens system
Stage - Platform that supports the microscope
slide
Light source - Shines through the specimen to
carry the specimen image to the viewer
Stage clip - Holds a microscope slide in position
Fine Adjustment Knob - Causes the stage to
move upward or downward at a slow rate and is
used to focus on a specimen.
Most animals are so small that they can
be studied only with the use of some magnifying
devices which provide an enlarged image of the
animal or parts of the animal. Simple hand
lenses will magnify a few diameters. For greater
magnification, however, a microscope is needed.
The compound microscope is the
microscope commonly used in classroom work
and
the
binocular
microscope
for
demonstration and dissection. The dissecting
microscope is used for examination of gross
specimens and for dissection under low power.
Some compound microscopes magnify about
2,000 times. Other types of microscopes, which
are more complicated and expensive, have
much greater magnifying power. The ultraviolet
microscope, for instance, magnifies up to
10,000 times while the electron microscope
up to more than 600,000 times.
Another type of microscope which
utilizes the refraction of light contrast the more
common types which use direct light is the
phase contrast microscope. It is especially
important in the study of living cells.
Parts of the Compound Microscope
Mechanical Parts
These consist of certain precise parts chiefly of
metal to support and the optical parts.
1. Bose - heavy Y-shaped foot on which the
microscope stands.
2. Pillar - short supporting piece arising from the
base.
3. Arm - short curved handle used in carrying
the microscope.
4. Inclination joint - joint between the pillar and
the arm used to tilt the upper parts.
5. Body tube - attached to the arm; bears the
lenses.
6. Draw tube - upper portion of the body tube
which bears the upper lenses.
7. Rotating nosepiece - revolving structure at
the lower end of the body tube which bears the
lower lenses.
8. Dust shield - metallic structure above the
nosepiece which protects the lower lenses.
9. Coarse adjustment screw - knob geared to
the body tube used to bring theobject into focus.
10. Fine adjustment screw - knob below the
coarse adjustment screw, used for more delicate
focusing.
11. Stage - platform with a central aperture and
two clips to hold the slide being studied.
12. Mechanical stage - mechanism attached to
the stage for ease in moving the slide.
Optical Parts
These consist principally of special types of
carefully ground and polished glasses aligned
on an optical axis for the enlargement of the
image of the object under
1. Mirror - found below the stage with concave
and flat surfaces to gather and direct the light to
illuminate the object.
2. Iris diaphragm - found above the mirror
consisting of several metal blades which form a
circular opening that may be enlarged or
reduced to control the amount of light reaching
the object.
3. Condenser - found immediately beneath the
stage; serves further to concentrate the light
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ZOOLOGY Laboratory Reviewer
rays on the specimen. The iris diaphragm and
the condenser constitute the substage.
4. Low power objective (L.P.O.) shorter lens
screwed to the rotating nosepiece; serves to
form a bigger image of the object within the body
tube.
5. High power objective (H.P.O) longer lens
screwed to the rotating nosepiece; serves to
form a bigger image of the object within the body
tube.
6. Ocular (eyepiece) - found in the draw tube
used for further magnification of the image.
Care of the Microscope
1. Always carry the microscope with two hands,
your left supporting the base and your right
graphing the handle firmly.
2. Never remove any parts of the microscope.
Report any missing or damaged part to your
instructor immediately.
3. Never let the lenses come in contact with any
chemical.
4. To clean the lenses, use lens paper or soft
tissue paper.
5. Return the microscope to its proper place with
the low power objective at its lowest limit, the
mirror in vertical position and the clips directed
forward.
Directions for Using the Microscope
1. Place the low power (shorter) ocular in the
draw tube.
2. Gently rotate the nosepiece to bring the LP.O.
into position. The low power objective is in
position when it is in exact alignment with the
central opening of the stage. The alignment is
indicated by a soft click as you turn the
nosepiece.
3. Look through the ocular with one eye and
adjust the mirror for even illumination. Never use
direct sunlight when you look through the
microscope as it may injure your eye. Keep both
eyes open and relaxed.
4. Raise and lower the substage and note how
the light intensity is changed. The amount of
light may be increased or decreased by opening
or closing the iris diaphragm. For every object
and at each magnification, there is a certain light
intensity at which a maximum of detail is seen.
Be able to recognize and to obtain this condition.
5. Secure the mounted slide on the stage with
one of the clips, preferably the right one so that
the slide can be moved about easily while
focusing.
6. Center the slide over the stage opening and
bring the tip of the objective about
one or two millimeters above the coverglass.
7. Look through the ocular and slowly turn the
coarse adjustment screw counterclockwise until
the object is clearly in view; then use the fine
adjustment screw to get a sharp image. Never
focus with the coarse adjustment screw while
looking through the microscope as you are liable
to crush the slide and damage the lens.
a. If you cannot see the object, it means
you have not placed it at the center of
the microscopic field.
b. Re-center the object and repeat the
focusing procedure until you see it.
8. Leaving the focus obtained with the L.P.O.
unchanged, rotate the H.P.O. and bring it over
the object. If the two objectives are parfocal, the
object will be seen right away. If they are not
parfocal, the image is either blurred or totally
invisible. In either case, the fine adjustment
screw should be used to bring the image into
focus. If the adjustment and focusing have been
made correctly, only a much enlarged portion of
the object can be seen.
Magnification
The magnification of a microscope means the
number of times the image of an object is
enlarged compared with the actual size of the
object when seen by the unaided eye. The
approximate magnification of gross specimens
may be determined in the following manner:
1. Measure the object with a millimeter ruler
before it is magnified.
2. Place the object under the L.P.O. 3. Place a
millimeter ruler along the right side of the stage.
4. Look into the microscope with one eye and at
the millimeter ruler with the other eye. Both the
object and the ruler can be seen at the same
time.
5. Take the measurement of the image.
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ZOOLOGY Laboratory Reviewer
6. Divide the size of the image by the actual size
of the object. The result of this computation
preceded by the sign "X" is used to indicate the
magnification. Thus, the symbol X 20 placed
under a drawing means that the figure has been
drawn 20 times larger than the actual size.
To
accurately
determine
the
magnification of microscopic objects, a
micrometer ocular and a stage micrometer are
used.
The
total
magnification
of
a
microscope is the product of the separate
magnifying powers of the objectives and oculars.
The magnifying capacities are stamped on the
oculars and objectives. An ocular 10 X when
working with an objective 10 X will magnify 100
times. Various degrees of magnification may be
obtained with the use of different combinations
of oculars and objectives. Be sure to understand
the magnifying capacity assigned to you.
Mount on a slide a few strands of cotton
fibers, a drop of water and some fine particles of
dust or stain powder. Examine the mount under
the microscope. Distinguish the cotton fibers,
bubbles, and particles of dust or stain powder as
seen under the L.P.O. and H.P.O. Hair and bits
of tissue paper may also be used as particle
materials. These will help familiarize the student
with these common object or parts of objects
that will be studied especially in fresh mounts.
The Animal Cell
The body of living things, whether plants or
animals, is composed of a living substance
called protoplasm. This substance is partitioned
into
microscopic,
variously
shaped
compartments known as cells immersed in a
liquid called tissue liquid. In the protozoan and
the lowest form of life the bacteria, the whole
body, consist of a single cell, in the higher forms,
an individual consists of many different cells.
These are the two principal types of cells in a
multicellular animal: The somatic cells, which
make up the main bulk of the body, and the
germ or egg cells, which have to do with the
reproduction of the individuals.
The study of a cell, its structure and activities is
known as cytology. For the cytological studies,
a small section is sliced from the body of an
animal. This is "killed" and preserved, washed,
dehydrated, cut into thin sections with a
precision machine, the microtome, mounted on
a microscope slide and stained to bring out the
cellular structures. Live cells may be treated with
stains to make the parts visible. Many cell parts
may be seen only when stained with appropriate
dyes or with the use of the electron microscope.
The unit in measuring cells is the micron (plural,
micra) which is one thousandth (1/1000) of a
millimeter. A few cells, like the eggs of birds and
reptiles, are very large. The ostrich egg is
believed to be the largest, about 80 millimeters
in diameter while the single-celled bacteria are
at the visibility limits of most microscopes.
Parts of the Cell
1. Plasma membrane or Cell membrane is a
thin
doubled
layered,
semi-permeable
membrane enclosing the cell. This membrane
can form little pockets into which nutrients flow.
Then the pocket is closed, trapping the food
solution inside the cell. Plant cells in contrast to
animal cells, have an additional thick cell wall
exterior to the membrane, of variable
composition and which serves for support.
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2. Cytosome or cell body is the more or less
homogeneous part which constitutes the matrix
of the cell enclosed by the cell membrane. The
protoplasm in the cytosome is referred to as
cytoplasm, and in which a large number of
inclusions including crystals, droplets of fats,
carbohydrates and protein granules either
egested or produced by the cell, remain
suspended.
10. Centrosphere - clear, spherical area around
the centrioles where several radiating fibers, the
aster, may be seen.
11. Golgi bodies - protein-filled sacs with
perforated edges.
3. Nucleus - the large spherical body found at or
near the center of the cell enclosed by a
perforated nuclear membrane. Protoplasm
inside the nucleus is referred to as
nucleoplasm or karyolymph.
4. Endoplasmic reticulum or ER it is a network
of exceeding fine, parallel membranes with the
space between. In some parts of the cell they
form snaking channels which is transverse the
cytoplasm
from
membrane
to
nuclear
membrane.
5. Ribosome - the small spheres along the
edges of most of the ER. These serves as the
protein factories.
6. Lysosomes are little sacs filled with granules.
They are known to breakdown defective cell
structures or destroy a foreign material that
enters the cell.
7.
Mitochondria
are
sausage-shaped
organelles. Red blood cells lack mitochondria
but other cells may contain anywhere from 50 to
50,000 of them. Called the powerhouse of the
cell, mitochondria provide the energy for all cell
activities.
8. Microsomes - these are exceedingly tiny
granules and only visible under the electron
microscope. Present in all cells, they contain
nucleoproteins and enzymes required in many
synthesis reactions.
9. Centrioles - one or two darkly staining
spherical bodies near the nucleus.
Shapes of Animal Cells
Cells vary in shape according to their
organization and functions. Some cells are
known to undergo changes in shape. Although
there is a diversity of cell shapes. The shapes of
all nuclei are generally spherical. It is chiefly the
cytostome that exhibits modified shapes. Below
is the list of easily differentiated cell shapes.
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ZOOLOGY Laboratory Reviewer
1. Spherical or globular - egg cells or ova
2. Squamous or pavement (thin or flat) surface cells of the skin.
3. Polygonal - cells of the liver
4. Tall and columnar - cells lining the intestines
5. Cuboidal - cells of kidney tubules.
6. Pyramidal - cells lining certain glandular
structural structures.
7. Fusiform (spindle-shaped) - smooth muscle
cells of the stomach and intestines.
8. Stellate (star-like) - bone cells
9. Spider-like - bone cells
10. Amorphous (constantly changing shape)
- white blood cells
11. Oval - red blood cell of frog and camel
12. Circular or disc-shaped - red blood cells of
man
13. Thread-like- sperm cells
14. Goblet-shaped - goblet cells of intestines.
15. Net-like - cardiac muscle cells
16. Filamentous - voluntary muscle cells
17. Ciliated (with numerous short hair-like
protoplasmic processes known as cilia on its
exposed surface) - cells of the trachea of
mammals and lining of roof buccal cavity of the
frog.
18. Flagellated (with one or more slender
whip-like cytoplasmic processes or flagella)-cells
of the inner lining of the gastro-vascular cavity of
Hydra.
Different Cells and their Classification and
Part of the Body where they may Found
Ovum Cell - found in ovaries
Sperm cells - are produced in men's testicles
Egg cells - are produced in women's ovaries.
Smooth Muscle Cell - spindle-shaped and have
single elongated nuclei.
Simple Squamous - epithelia are found lining
the cavities of the body including the pericardial,
pleural, and peritoneal cavity.
Epithelial Cell - a type of a cell that lines the
surfaces of your body.
Simple Cell - one of two main physiological
types of cell in the primary visual cortex.
Pseudostratified Columnar - the type of
respiratory epithelium found in the linings of the
trachea as well as the upper respiratory tract.
Simple Cuboidal - found along the respiratory
airways
Nerve Cell - are the fundamental units of the
brain and nervous system.
Red Blood Cell - A type of blood cell that is
made in the bone marrow and found in the
blood.
Immune Cell - A cell that is part of the immune
system and helps the body fight infections and
other diseases.
Movement of Substance in the Cell
Every cell whether it is of a single-celled
plant or animal, or one of the billion cells in man,
must be continuously supplied with the nutrients
in order to perform its various metabolic
functions.
Molecules of liquids and gasses tend to
move in all directions; they are spread evenly
throughout the available space. Their movement
from a region of high concentration is known as
diffusion.
Diffusion of nutrients and waste
products on the is governed largely by the
membrane that surrounds the cell and its
components. A membrane is said to be
permeable if it permits no substance to pass
through, and semi permeable if it allows only
certain substances to diffuse through.
When an unequal concentration of
dissolved substances occur on the opposite
sides of a semi permeable membrane, the
resulting differences in diffusion pressure cause
an exchange of water and of the dissolved
substance through the membrane until there is
equilibrium on both sides. The diffusion of water
is a process called osmosis. When two fluids
contain equal concentration of dissolved
substances, they are said to be isotonic. A
solution which has less dissolved substances
than the material is known as hypertonic.
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