This presentation is the first presentation for the laboratory
component of our course, and this laboratory deals with cytology, and this
lab exercise is intended to give you an appreciation for the extreme diversity
in the cell size and shape. Now you'll come to appreciate that the structure of
individual organelles is surprisingly similar among the various cell types, but
the concentration and distribution of organelles within different cell types
varies considerably with the individual cell function. You're going to be
responsible for identification of the different cell types that we show in
this presentation, but only after we introduce them to you in our lecture
presentations. So this is just intended to be an overview to help you begin to
get started in the laboratory. This first slide shows spinal ganglion. You can see
several big spinal ganglion cells here. You can identify a nucleus like this, and
a nucleolus. You can identify this particulate material in the cytoplasm,
this actually consists of ribosomes and rough endoplasmic reticulum,
and in neurons this is given the name nissel substance. You can also see nuclei of
satellite cells, or supporting cells, in this spinal ganglion cluster. These cells
essentially provide physical support for the neurons, and I'd like to make one
more point on this slide. You see where I'm highlighting with my pointer, this
structure, you might be tempted to call it the nuclear envelope, and I want to
caution you. At the light microscopic level you're not able to resolve the
nuclear envelope, or for that matter most of the other organelles. What you're
seeing here is just a diffraction pattern of the light as it's just
bending around the nuclear envelope, and of course the stain has just coalesced
in that area. Here is a multi polar neuron. You can see the nucleus. You can see cell
processes. These are actually dendrites that are coming into the cell body. Right
here is probably a profile of the axon hillock. We'll talk about that later in
the course. Here are some views of smooth muscle
cells. Smooth muscle have a typical spindle, or a few C form shape. You can
see the nucleus in many of the individual cells, and you should be aware
what the contractile elements are in these smooth muscle cells, and I'm not
going to tell you that at this point. We'll cover that in much more detail in
muscle, but you're gonna find as you work through our laboratory that there are
many instances where there are questions, and these questions are meant to help
you focus your study. So for example, on this slide I'd say, "This is smooth muscle.
Identify the nuclei core, smooth muscle cells are spindle shaped in that
contractile," and I would ask you, "What are the contractile elements in the
cytoplasm of these cells called," and I hope you would realize that it's actin
and myosin as the contractile elements. Here's an electron micrograph of a
capillary, and there are two cells that make up this capillary. They're shown in
this view so I can trace one cell like this, and the nucleus is in the plane of
section of this cell. Here I'm tracing it all around like so, and then a profile of
another capillary endothelial cell here on this cell. The nucleus is not in the
plane of section. Here is the capillary lumen. On the next slide we're going to
show a higher power view of the junction between these two endothelial cells. I
want to point out for you, on the low power you can see a lot of micro
pinocytotic vesicles. This would be how material traverses this capillary lumen,
and the luminal diameter in capillaries is just barely big enough to accommodate
a red blood cell. You don't necessarily appreciate that yet on this electron
micrograph, but you're going to come to realize as you go through the histology
laboratories that you can identify red
blood cells in tissue sections, and oftentimes you can identify capillaries
as just the very smallest vessel that contains a single red blood cell. Here is
a higher power view of the junctional complex between these two capillary
endothelial cells. You can see the nice detailed view of the plasma membrane on
one cell, and on another cell you can see some junctional complexes highlighted
here between these endothelial cells. Here would be the capillary lumen. Here
is a profile of some of these micro pinocytotic vesicles, and here is the
basal lamina. Another question to help focus your study, what is the composition
of the basal lamina and what cells are responsible for the synthesis of the
basal lamina? I'm not going to answer those questions for you here, those are
things that I would like you to look up to focus your study. We will of course come
to these as we progress through the course. Here is a profile of the wall of
the small intestine. The small intestinal wall is made up of simple columnar
epithelial cells. You can see the nuclei of these columnar epithelial cells. You
can see the lumen of the GI tract here, the slit-like lumen, because this is a
relatively high power light micrograph. These blue cells are goblet cells. They,
of course, secrete a mucus type material that we will talk about when we get into
the GI tract in more detail. This mucus material is important for the
function of the GI tract. On the next slide we're going to show a higher power
image of the electron microscopic level of an area like this. So we'll be looking
at this, the details of the brush border. Here is the brush border, this is
essentially elaborate membrane folding into micro villi. This membrane folding
functions to increase the surface area. So if I go back for one minute, here is
the lumen, and here it is on this slide. So this is the portion of one cell, the
portion of a second cell, the portion of another cell, and
yet the portion of another cell again. Here is the adsorbed glycocalyx that
we'll talk about later in the course, and in this high-power view of some of
these epithelial cells, you can see some organelle profiles. So for example, here
are a couple of mitochondria, here are a few more mitochondria. This is a fairly
high power view of rough endoplasmic reticulum. You can note the dilated
cisternae at some profiles. They're highlighted by these little dark
asterisks, and you can clearly see the individual ribosomes bound onto this
rough ER. This is an unusual preparation of a
spinal ganglion a disdain. Here is osmium impregnation. I don't expect you to know
that, but the dark colors from this osmium impregnation highlighting the
golgi apparatus. You're going to come to appreciate that the golgi tends to pick
up heavy metal staining, and so at the light microscopic level it's an easy way
to view the golgi. Here is a higher power electron micrograph, and here you can see
the typical arrangement of the golgi. Notice it's a series of stacked
membrane compartments. You can observe the cisternae that are highlighted here,
and you can observe lots of little vesicles that bud off from the golgi, and
then some larger vesicles that are related to the golgi. This is an example
of some lysosomal activity. These heterogeneous electron dense bodies, they're
just highlighted by the red arrows. This is an electron micrograph of a portion
of the proximal convoluted tubule of the kidney, and I put this in so that you'll
notice the numerous mitochondria that are inter digitated among the membrane
in foldings here. This is a very typical arrangement of cells that are involved
in active transport, and you're going to come to appreciate, later in the course,
that cells in the proximal convoluted tubule of the kidney are very much
involved in reabsorption of material, and they have a lot of mitochondria to
generate the energy for active transport for those cells to perform
their reabsorptive functions. This is a high-power view, both of a mitochondria
and rough ER. I think there'd be no trouble
with you identifying these. You can actually see the mitochondria. You can
see the mitochondrial matrix with some electron dense calcium deposits within
the matrix, and you can clearly see the inner mitochondrial membrane with the so
called cristae, and in some areas you can actually see the space between the inner
and outer mitochondrial membranes. Here is a profile of a pair of centrioles.
..right angles to each other. Here's one cut in, more like, a
longitudinal section, and here is one cut in the cross-section, and look at this.
You can actually observe the nine triplet arrangements of the microtubules,
and if you count around this- one two three four five six seven eight- nine
triplet microtubules that make up the structure of these centrioles. This is an
example of phagocytosis. This section probably came from a lymph node, maybe in
the lung, and you can observe a lot of black dust particles, and in these
macrophages the sample was probably taken from a patient that may have had
black lung disease, and here, just a high-power view of the nucleus. You can
see areas where the nuclear pores are formed. This is at the nuclear pores
discontinuity between the inner and outer nuclear membranes, and you can get
a sense here that the outer portion of the nuclear envelope, the outer nuclear
membrane, is actually continuous with the rough ER, it is a profile of that coming
like so. Here you get a sense of some ribosomes bound to the rough ER, and so
it goes without saying that the space between the inner and outer membranes of
the nuclei envelope is in continuity with the
luminal space of the ER.