Cytology Lab Notes 10/3/13
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Mitochondria
o Come in different shapes/orientations, and that will help you tell the cell type
 Adrenal cortex mito = elongated
 Brown fat mito = circular
o Vary in their density depending on the cell
o Slide MC00004 – Slice of Kidney
 Iron stain used to identify mitochondria
 Kidney uses a lot of mitochondria because it’s transporting things rapidly across cell
membrane (uses lots of ATP, so needs lots of mitochondria)
 Medium grey region:
 Zoom in 5x; round structures are tubules (proximal, distal convoluted)
o Walls of tubules are epithelial cells (apical surface facing free space)
o Dark structures are nuclei (some cells are just blank grey because you haven’t
cut right through the nucleus)
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o
Zoom in fully
o Can’t see membrane, so can’t tell where cells end/begin (dye doesn’t stain
membrane very well so you can’t see the border)
o Apical surface is lighter than the basal surface
 Apical region has more ion exchange
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Darker region:
 Darker clumps (speckles or threads) around basal region are aggregates of
mitochondria
o Slide UC004
 Darker mitochondria-rich cells on the bottom
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Endoplasmic Reticulum
o Rough ER – continuous with the rest of the membrane
 Sometimes quantity of ribosomes is so high that you can see it stained (this occurs in neurons
because they have a very high protein turnover rate, and hence high ribosomal activity)
o Slide MCO0035 – Nissl Bodies
 In this slide, dorsal is down and ventral is on top (typically reversed)
 Spinal neurons (here shown above on ventral side) are very large neurons
 Dark dots within region are cell bodies of spinal motor neurons
 Located in ventral horns
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Zoom in 10x on large dark spots – neurons
 Traditional stain only shows cell bodies; lots of other interest components to neuron.
Highly branched, can be very long, etc
Zoom in 40x to top-left cell
 “Dead space” in middle is nucleus (appears lighter than soma)
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Smaller dark nucleoli surrounding the neurons are of glial cells
 Compared to neurons, which have their whole cytoplasm being stained (due to
ribosomes and rough ER), only nucleoli stained in glia
Golgi
o Normally you can’t see golgi in a microscope because they’re too small. In neurons, however,
because they do so much packaging of proteins in vesicles, you can see aggregate clumps of golgi.
o MCO0005 – dorsal root ganglion (spinal cord to peripheral parts of body wall)
 Take in information from body wall into dorsal horn of spinal cord (sensory neuron)
 Orange/brown stain stains the golgi
 Majority of brown speckles are just space
 Dark spots in the area are nuclei of glial cells
 Neurons = pink-staining structures with brown in them
 The ones with brown speckles are ones that’ll show golgi
 Brown speckles around pink nucleus are the aggregates of golgi
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Pretty large cells (20-30 microns, or 2-3x larger than average cell)
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Microfilaments
o LH0046
 Thick and thin filaments run in a very precise order/overlap with one another (produces the
striated appearance): hallmark of skeletal muscle
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Actin- and myosin-based filaments run in very precise arrays, allowing you to see this
aggregate (individually, the filaments are inconspicuous because they are spread out to
maintain cell shape; here, they are together to generate contractile force). Zoomed in:
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Smooth muscle does not have this precise array – no striations to be seen via microscope.
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Another look. Individual muscle cells can be a foot long (not very wide, but very long).
Note dark regions in the middle; nucleus and mitochondria all exist at the peripheral edge of
the cell (not in the middle). Cell is elongated, and nucleus is accordingly elongated to
accommodate the form. Cells are multinucleated (hundreds of nuclei per cell). Tensile
strength and contractile forces for such a long cell requires that much machinery to function.
Striations: dark regions = dense staining = filaments overlap; light regions = non-overlapping
regions; thin white horizontal lines = where the filaments anchor
Glycogen as a Cell Inclusion
o Not encapsulated (non membrane bound), other than the hydrophobicity that creates the round
droplet
o Hepatocytes offer the best opportunity to see this.
o MCO0002
 Round cells with greyish nucleus and dark nucleolus inside
 Red stain is for the glycogen (glucose reservoir)
 White space = blood vessels (liver cells line up on either side and extract plasma from them)
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Chromatin and Nuclear Structure
o Perinuclear region has lots of rough ER
o Euchromatin in the middle, heterochromatin near the border of the nucleus (heterochromatin is more
densely packed, and stains darker)
 Dense packing of heterochromatin protects it from degradation by proteins
o UW061
 Look at blood vessel structure: wall of artery is made of smooth muscle.
 Elongated dark entities around circumference of muscle = nuclei of smooth muscle
 Can be thin and stretched out, or shorter/twisted (corkscrew)
o Designed to regulate vessel diameter
o Contraction of smooth cell: when it shortens, it also twists, and the nucleus
shortens and twists
o MCO0658
 Squamous cells line the lumen (dark = nucleus)
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Smooth muscle cells change their length dramatically more than skeletal muscles do
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Mitosis
o Look up the different phases of mitosis on your own.
o MCO0001 – Animal Mitosis
 Anaphase. Yay.
o UC029 – White Fish Mitosis
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