Tissue and cells

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HISTOLOGY BIOL 4000
INTRODUCTION

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Basic Terminology
Histology :
•Might be better defined as the study of the
structure of tissues.
•histos - tissue
•logos - study of
•So, study of tissue.

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SO WHAT IS THE SCIENCE OF
HISTOLOGY?

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•Tissue is derived from the French word, tissu which means "weave or texture".
•So, for example, a fine,
lightweight fabric was called a
tissue, or a group of connected
falsehoods is referred to as a
"tissue of lies".
•Prior to the late 1700s, “tissue” did not refer to organic, cellular layers, but rather to
anything woven or textured.

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The term “tissue” as it is used in Histology
Came into usage in the English language
in the late 1700s
Coined by the French scientist Bichat
Marie Francois Xavier Bichat (1771-
1802)

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http://home-and-garden.webshots.com/photo/1092738817041241628bWnrML
Bichat based his descriptions of tissues on the
results of gross dissection (what he saw with his
“naked” eyes). Based on such observations, he
described 21 “weaves” or “textures” that he called
tissues - Bichat’s 21 textures.
It's important to realize that all Bichat’s work was
done without a microscope
Other scientists of that period made use of the
microscope that had been much improved by the
efforts of the Dutch scientist Leeuwenhoek, to
delve more deeply into the nature of the weaves
or tissues that Bichat had described.
Antony van Leeuwenhoek
(1632-1723)

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A Brief History of the Microscope:
First microscopes were constructed in the Netherlands during the late 1500s.
Actual inventor uncertain, but credit is often given to Zacharias Janssen; however, other
possible inventors are Hans Lippershey (inventor of the first real telescope) and Zacharias’
father, Hans Janssen
Magnification 3 - 9X, images poor
http://www.southwestschools.org/jsfaculty/Microscopes/history.html

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History of the microscope:
1. First microscope with “high” magnification and good image quality was developed
by Anthony van Leeuwenhoek (1633 - 1723) about 1670.
2. Leeuwenhoek used beads formed from drops of molten glass as his lenses.
3. These were mounted in a metal plate that had an adjustable stage on which the
specimen to be examined was mounted.
4. Natural light or light from a candle flame was used to illuminate the specimen.
http://www.college-optometrists.org/index.aspx/pcms/site.college.What_We_Do.museyeum.online_exhibitions.microscopy.early/

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History of the microscope:
Microscope design quickly evolved from better simple microscopes (one lens) to more
sophisticated compound (more than one lens in series) models with greatly improved
image quality and magnification.
http://www.college-optometrists.org/index.aspx/pcms/site.college.What_We_Do.museyeum.online_exhibitions.microscopy.early/

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1. The specimen is placed on the staged
2. Light is reflected or projected through or onto the specimen.
3. Reflected or projected light from the specimen passes through the objective lenses
which magnify the resultant image (e.g. 10 X).
4. The light forming the image from the objective then passes through the eyepiece
lenses which again magnify the image (e.g. 10X).
5. The spacing of the of the lenses relative to each other and to the specimen and the
position of ones eyes acts to focus the image on the retina.
6. In the example above, the magification of the image would be, …… 10
x 10 = 100X
How a compound microscope works:
http://www.yesmag.bc.ca/how_work/microscope.html

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17th century
1670 - Robert Hooke examined cork with a
microscope and found it was composed of tiny
“chambers”.
http://www.realcork.org/html/prod_cork_properties.php
Hook called these chambers cells because they
reminded him of the small rooms or chambers found
in monasteries that, at that time, were described by
the the latin word “cella”.
Hooke published this information, as well as the
results of other microscopic research he had
performed in his Micrographia.
Tissues and Cells

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Similar compartments were found to be present in animal tissue.
Additional study revealed that, in living tissues, these compartments were filled with a fluid
substance which is, of course, the cell cytoplasm.

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The Cell Theory
1832 - Schleiden and Schwann independently hypothesized
that all plant and animal tissues are composed of cells.
They believed that cells were the “ultimate” units of living
organisms.
This is in part correct since cells are the smallest, potentially
independent unit of a living organism.
However, further study revealed that these small cells
contained even smaller structures in their cytoplasm.
THEODOR SCHWANN
1810 - 1882
MATTHIAS JAKOB SCHLEIDEN
1804 - 1881

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Stains were not used to examine cells in these early studies. Scientists using the microscope relied
entirely on differences in refractive index to make structures in tissues visible.
Initially only the nucleus (nut) of the cell was noted,
but it soon became obvious that there was an even
smaller structure within the nucleus that was given the
name “nucleolus” which means “small nut”.
http://faraday.physics.uiowa.edu/movies/MPEG/6a40.30.mpg
This didn’t work very well - not enough contrast

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Various stains were introduced to increase contrast.
Basophil - granules contain heparin and
histamine.

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We now know that all the tissues of the body are formed from 4
basic types of tissue.
• Epithelial tissue
• Connective tissue
• Muscle tissue
• Nervous tissue

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•tissues - interwoven masses of cells and extra cellular material
•cells - living, more or less self-sufficient entities that form tissues. Surrounded by a
membrane.
•organelles - membrane bound structures within cells (e.g. mitochondria, golgi bodies,
lysosomes)
•inclusions - various non-membrane bound structures within cells (e.g. glycogen
granules)
•molecules and atoms - well, hopefully you know what these are
Definitions

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What is meant by structure?
As we have already stated, histology is the study of the
structure of tissues.
• Tissue structure - how cells combine together with extracellular
material and each other to form a tissue
• Cellular structure - how a cell is shaped, and how the components
inside cells are organized to support that cells specific function
• Sub-cellular structure - detailed analysis of organelles and inclusions
and finally,

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• Histochemical structure - molecular analysis of cellular
structure
1. Energy storage molecules - lipid, protein, carbohydrate - energy for
cell metabolism.
2. Structural molecules - such as phospholipids and cholesterol,
proteins such as tubulin, actin, myosin, etc. Raw materials for
synthesis and construction of enzymes, membranes, microtubules,
micro-filaments, organelles, cells, etc.
3. Information molecules - DNA, RNA
4. Catalysts, reaction initiators - special proteins called enzymes.
5. Antigenicity - interaction of cell molecular structure with proteins
called immunoglobulins (antibodies - the immune system)

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Tissues, Cells, Cell Theory, Stains, Structure:
Put it all together
Friedrich Gustav Jacob Henle (1801-
1885) - credited with creating the first
“histology” that was based on a
detailed examination of tissues with
the microscope,
1838 - presented report on epithelia in
the human body. Demonstrated that all
internal and external surfaces of the
body were covered by epithelia.
- you get Histology, a science:

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Henle developed a classification for epithelia:
pavement - squamous
cylindrical - cuboidal or columnar
ciliated - having cilia
e.g. loop of Henle
Also recognized that the epithelium lining the bladder changed
shape as the bladder filled - what we call a transitional
epithelium today.
Was also an anatomist and cytologist - many anatomical,
tissue and cellular structures are named after him.