Microscope Types
The use of a microscope is to provide a
magnified view of objects (that are
being analysed) that are otherwise to
small to be seen by the naked eye. They
can be described according to their
illumination and lens arrangement. (i)
Microscopes are able to use either
light or electrons as their illumination
source, which are respectively known
as light powered and electron microscopes.
(ii) Monocular microscopes have a
single eye piece where as binocular
microscopes posses two eye pieces,
position side by side for simultaneous
viewing with both eyes. (iii) A simple
microscope consists of one single lens
system where as a compound microscope
consists of two main lens systems, an
ocular and objective, which are
superimposed over each other to provide greater
magnification. In Biology,
microscopes can also be described according to some
specific purpose such as
dissecting microscopes, which are commonly referred, as
dissectors are
especially suitable for use while dissecting very small or
delicate
specimens. Microscopes are usually equipped with a series of
interchangeable
eyepiece lenses (oculars), each with different individual
magnifications.
Majority of ocular magnification is as followed: X4, X5, X6, X7,
X8, X10,
X12, and X15. On a typical monocular microscope objectives
magnification
found is as followed: X4 = SCANNING POWER = S.P. X10 = LOW POWER =
L.P.
X40 = HIGH POWER = H.P. To find the overall magnification factor
obtained
when using any microscope is calculated by the following
mathematical formula:
OCULAR magnification X OBJECTIVE magnification =
OVERALL magnification The
condenser lens is situated below the stage and
causes light rays to converge on
to the specimen situated on the stage, thus
illuminating is adequately when
magnified by the viewing lens. The amount of
light passing through the condenser
lens can be varied by opening and closing
the iris diaphragm, situated at the
bottom of the condenser. AIM: (i) To
become familiar with the features and
function of the monocular and stereo
microscopes. (ii) To gain first hand
experience in sketching scientific
diagrams from prepared slides. EQUIPMENT
USED: Monocular microscopes,
microscope lamp, lens cleaning tissue,
lens-cleaning fluid, and various
prepared slides. PROCEDURE: When using a
monocular microscope, adjust the
condenser lens so that it comes to rest against
the bottom of the stage. Wind
it down about 2mm below this level; now its in
the ideal position. The iris
diaphragm should also be readjusted each time a
slide is moved from S.P to
L.P. H.P. Obtain the first of the prepared slides and
examine it under the
scanning power. (ALWAYS begin with the S.P. then the L.P.
and finally the
H.P.! NEVER the other way round!). Adjust the course focussing
mechanism
followed by the fine focus knob this will assure maximum
clarity.
Having adjusted the course focus whilst operating the scanning
power setting,
there is no need to use it again with either the L.P. or H.P.
magnifications.
Use only the FINE FOCUS with these magnifications. N.B
When operating either
focussing mechanism, ALWAYS adjust the two wheels
TOWARDS yourself, NEVER away
from you! This will insure that the objective
moves AWAY from the side NOT
towards it, therefore the objective it CANNOT be
rammed through the specimen
slide! In Scientific sketching, try to keep BOTH
eyes open, using one to peer
down the microscope, and using the other eye to
draw with. In addition, the
sketches should ALWAYS include: A Title,
Magnification factor, Labels (if
possible) and be approximately Ύ -1 full
page in size. DISCUSSION/CONCLUSION:
Microscopes have many components,
but one component was used at all times and
most likely without even noticing
you used it. That component is sits at the top
of the microscope, which you
look through and it is call the ocular. The ocular
is interchangeable with
different individual magnifications including X10, which
was used in
examining all prepared slides. Therefore, even if the objective
magnification
was X4 (S.P.), X10 (L.P.), or X40 (H.P.) the ocular did not change
it was
still the same magnification of X10. By using the mathematic formula
of
Ocular times, Objective will equal to the overall magnification you
were using
while examining a slide. These magnifications were: OCULAR X
OBJECTIVE = OVERALL
MAGNIFICATION FACTOR X10 X X4 = 40 times = S.P. X10 X
X10 = 100 times = L.P. X10
X X40 = 400 times = H.P. The specimens that
are on slides come in many come
colours and shape it depends on what specimen
and which stain is used. In this
experiment the prepared side specimens that
were examined were an Ovary and
Testes Colon Appendix that were pink,
Striated Muscle was a purple red colour,
and Grass Root Tip came in three
colours red light blue and cream. Each slide
was examined with Scanning
power, Low power, and High power, there are
tremendous amounts of differences
between the sides. Cause of out five the sides
selected four are of from
different parts of an animal and one is a plant slide.
The main
difference is between the magnification factors, scanning power (S.P.)
is the
only one that enables you to view all or most of the specimen
section.
Viewing in S.P. the specimen section structure is very cramped
with every thing
very close together (refer to sketches). When changing to
low power (L.P.) the
specimen section structure is larger where the section
is a lot more free
enabling the viewer to view in between the sections
components (refer to
sketches). High power (H.P.) is where the specimen
section structures is huge
and more unattached compared to those of the S.P.
and L.P. Therefore, in H.P.
the structure can look total different from S.P.
and L.P., the specimen section
almost like its a completely different slide
altogether. By examining the
sides specimens and the sketches, this was drawn
while the slides specimens were
under the microscope. Through these sketches
and titles, it gave out enough
information to seek out and research the
suitable reference to complete this
report. OVARY Cortex The cortex of the
ovary is covered by a modified
mesothelium, the germinal epithelium. Deep to
this simple cuboidal to simple
squamous epithelium is the tunica albuginea,
the fibrous connective tissues
capsule of the ovary. The remainder of the
ovarian connective tissue is more
cellular and is referred to as the stroma.
The cortex houses the ovarian
follicles in various stages of development.
Primordial Follicles Primordial
follicles consist of a primary oocyte
surrounded by a single layer of flattened
follicular (granulosa) cells.
Primary Follicular (A) Unilaminar Primary
Follicles consists of a
primary oocyte surrounded by a single layer of
cuboidal follicular cells.
Primary Follicular (B) Multilaminar Primary
Follicles consists of a
primary oocyte surrounded by several layers of
follicular cells. The zona
pellucida is visible. The theca interna is beginning
to organised. Secondary
(Vesicular) Follicle The secondary follicle is
distinguished from the
primary multilaminar follicles by its larger size, by a
well-established
theca interna and theca externa. Especially by the presence of
follicular
fluid in small cavities formed from intercellular space of the
follicular
cells. These fluids filled cavities are known as Call Exner
bodies.
Graafian (Mature) Follicles the graafian follicles is very large,
the Call
Exner bodies have coalesced into a single space and the antrum is
filled
with follicular fluid. The wall of the antrum is referred to as the
membrane
granulosa and the region of the oocyte and the follicular cells jutting
into
the antrum is the cumulus oophorus. The single layer of follicular
cells
immediately surrounding the oocyte is the corona radiata. Long apical
processes
of these cells extend into the zona pellucida. The theca interna
and theca
externa are well developed; the former displays numerous cells and
capillaries,
where as the latter is less cellular and more fibrous. Atretic
Follicles (A)
Atretic follicles are in the state of degeneration. They
are characterised in
later stages by the presence of fibroblasts in the
follicle and a degenerated
oocyte. Medulla (B) The Medulla of the ovary is
composed of a relativity
loose fibroblastic connective tissue housing and
extensive vascular supply
including spiral arteries and convoluted veins.
Corpus Luteum (C) Subsequent
to the extrusion of the secondary oocyte with
its attendant follicular cells,
the remnant of the Graafian follicle becomes
partly filled with blood and is known as the corpus hemorrhagicum. Cells of the
membrane granulosa are
transformed into large granulosa lutein cells.
Moreover, the cells of the theca
interna also increase in size to become
theca lutein cells, although they remain
smaller than the granulosa lutein
cells. Corpus Albicans (D) The corpus
albicans is a corpus luteum that is
in the process of involution a
hyalinization. It becomes fibrotic with few
fibroblasts among the intercellular
materials. Eventually, the corpus
albicans will become scar tissue on the
ovarian surface. TESTES Capsule The
fibromuscular connective tissue capsule
of the testes is known as the tunica
albuginea, whose inner vascular layer is
the tunica vasculosa. The capsule is
thickened at the mediastinum testis from
which septa emanate subdividing the
testis into approximately 250 incomplete
lobuli testis, with each containing
one to four seminiferous tubules embedded in
a connective tissue stroma.
Seminiferous Tubules Each highly convoluted
seminiferous tubule is composed
of a fibromuscular tunica propria, which is
separated from the seminiferous
epithelium by a basal membrane. Seminiferous
Epithelium The
seminiferous epithelium is a composed of sustentacular
sertoli cells and a
stratified layer of developing male gametes. Sertoli cells
establish a blood
testis barrier by forming occluding junctions with each
other, thus
subdividing the seminiferous tubule into adluminal and basal
compartments.
The basal compartments house spermatogonia A (both light and
dark),
spermatogonia B, and the basal aspects of sertoli cells. The
adluminal
compartment contains the apical portions of sertoli cells primary
spermatocytes,
secondary spermatocytes, spermatids, and spermatozoa. Tunica
Propria The
tunica propria consist of loose collagenous connective tissue,
fibroblasts, and
myoid cells. Stroma loose, vascular, connective tissue
stroma surrounding
seminiferous tubules houses small clusters of large,
vacuolated appearing
endocrine cells, in the interstitial cells (of
leydig). COLON, APPENDIX Mucosa
the mucosa presents no specialised folds.
It is thicker than that of the
small intestine. Epithelium (A) The simple
columnar epithelium has goblet
cells and columnar cells. Lamina Propria (B)
The crypts of lieberkόhn of
the lamina propria are longer than those of the
small intestine. They are
composed of numerous goblet cells, a few APUD
cells, and stem cells. Lymphatic
nodules are frequently present. Muscularis
Mucosae (C) The muscularis
mucosae consist of inner circular and outer
longitudinal smooth muscle layers.
Submucosa The submucosa resembles
that of the jejunum or ileum. Muscularis
Externa The muscularis externa
is composed of inner circular and outer
longitudinal smooth muscle layers.
The outer longitudinal muscle is modified
into teniae coli, three flat
ribbons of longitudinally arranged smooth muscle.
These are responsible
for the formation of haustra coli (sacculation).
Auerbachs plexus
occupies its position between the two layers. Serosa (A)
The colon
possesses both serosa and adventitia. The serosa presents small, fat
filled
pouches, the appendices epiploicae. Appendix (B) The lumen of the
appendix
is usually stellate shaped, and it may be obliterated. The simple
columnar
epithelium covers a lamina propria rich in lymphatic nodules and some
crypts
of lieberkόhn. The muscularis mucosae, submucosa, and muscularis
externa
conform to the general plan of the digestive tract. It is covered by
serosa.
Anal Canal (C) The anal canal presents longitudinal folds, anal
columns,
that become jointed at the orifice of the anus to form anal valves
and
intervening anal sinuses. The epithelium changes from the simple columnar
of the
rectum, to simple cuboidal at the anal valves, to epidermis at the
orifice of
the anus. Circumanal glands, hair follicles, and sebaceous glands
are present
here. The submucosa is rich in vascular supply, while the
muscularis externa
forms the internal anal sphincter muscle. An adventitia
connects the anus to the
surrounding structures. STRIATED MUSCLES
Longitudinal Section (A) Connective
tissue elements are clearly
identifiable because of the presence of the nuclei
that are considerably
smaller than those of cardiac muscle cells. The connective
tissue is rich in
vascular components, especially capillaries. The endomysium is
present but
indistinct. Longitudinal Section (B) Cardiac muscle cells from
long,
branching, and anastomosing muscle fibers Bluntly oval nuclei are large,
are
centrally located within the cell, and appearing somewhat vesicular. A and
I
bands are present but are not as clearly defined as in skeletal
muscle.
Intercalated discs, marking the boundaries of contiguous cardiac
muscle cell,
may be indistinct unless special staining techniques are used.
Purkinje fibers
are occasionally evident. ROOT TIP As root tissues
differentiate behind the
growing tip, they form a pattern of cylinders
(tubes) within the cylinders. Each
cylinder is composed of tissue that has a
specific role to play for the plant.
Epidermis The outermost cylinder
is only cell in thickness and is called the
epidermis. This encloses and
protects the underlying tissues. Some epidermis
cells differentiate into hair
cells. These stick out into surrounding soil
spaces and absorb water and
selected mineral ions. Cortex Parenchyma A very
thick cylinder is found
just under the epidermis. This called the cortex or
cortex parenchyma.
Parenchyma cells store excess nutrients, usually in the form
of starch. These
cells are loosely packed so that the spaces between them can
direct water and
mineral ions coming from root hairs and cortex spaces and
directs them into
the central vascular core. Pericycle Another thin cylinder
is found under
the endodermis, the pericycle. Pericycle cells can function like
meristem and
mitotically produce secondary or branch roots. The pericycle also
constitutes
the outer boundary of the vascular core, a structure that contains
the
internal, liquid transport highways of the plant in the form of
highly
specialised tube like or conducting tissues. Vascular Cylinder The
vascular
cylinder is comprised of tissues that transport nutrients. Water and
mineral
ions taken in by root hairs and concentrated into the core by the
endodermis are
transported up into the plant shoot by xylem tubes. Sugar
rich fluid,
sucrose, made in the leaves as glucose is transported by phloem
sieve tubes into
the root core, where it is distributed to root cells for
energy production or
storage as starch in the cortex parenchyma. Xylem and
phloem tissues are
excellent examples of how cell structure dictates
function. Xylem Cells (A)
Xylem cells have to die before they can serve
the transport needs of the plant.
Dead xylem cells leave behind a thick,
hollow, tubular wall, which joins end to
end with other xylem walls to form a
microscopic but strong and fixable tube,
which extends from root to leaf.
Xylem walls have slit like openings or
pits, which provide for the sideways
transfer of water and mineral ions into
surrounding tissue. Close examination
of these wall shows that their thickness
is due to cellulose and a cement
like substance call lignin. Lignin creates the
wood in woody plants some
walls are reinforced with internal rings or spirals.
These rings of
lignin help to support the plant. Xylem tubes are sometimes
called vessels,
i.e. composed of vessel cells, or elements. Primitive plants
such as pines
and firs have tracheid xylem which thinner walls and tapered ends.
Phloem
(B) Phloem is made up of two basic cell types, both of which are
living
when they serve the transport needs of the plant. The lager cell type is
a
sieve tube member; the small is a companion cell. The sieve tubes
member,
though living, does not have a nucleus and therefore does not control
its own
metabolism. What the needs it has are apparently provide for by the
tiny
companion cell that is attached to the sieve tube member. Sieve tubes
members
are very much smaller and have thinner walls than xylem, but like
xylem, they
join end to end to form sieve tubes that extend leaves to roots.
These take
their name from the tiny, sieve like pores in their walls and the
larger pores
called sieve plates that separate one member from another. Pores
provide for the
horizontal and vertical movement of the sugar rich sap that
slowly moves
down from the leaves, supplying energy, and elements to all
plant tissues. Large
parenchymal cells called pith may also be associated
with the vascular
cylinder
phloem.