Cytology
Cell: Introduction
History
• Robert Hooke introduced the term "cell" when he looked at cork and named his findings cellule / cellula.
• Some of his obversasions are basic principles of cell theory:
1. All living cells are comprised of cells
2. Cells are the smalles "living" unit in an organism
3. (Cells come from previously existing cells)
• Anton van Leeuwenhoek was a master of microscopy and was the first who observed living cells
• Three German scienists from the early 19 century completed the early observation to a modern cell theory
o Rudolf Virchow: founder of the modern pathology. "All cells come from preexisting cells"
o Schleiden (plants) & Schwann (animals) used the work of Virchow to better it
Cell-function
• Form-follows-function-principle
• Heredity: central definition of life
o Orderly structures are generated but without the same type of link between the pecularities of parents and of
the offspring
• Vehicle for hereditary information: an aggregate of more than 1013 cells generated by cell division from a single cell.
The single cell, therefore, is the vehicle for the hereditary information
• The four main families of small organic molecules in cells:
• Three families of macromolecules:
• Each macromolecule is a polymer formed from small molecules (called
monomers) linked together by covalet bond.
• Macromolecules are by weight the most abundant carbon-containing
molecules in a living cell
• Macromolecules with complementary surfaces can bind tightly through
noncovalent bonds
• Flow of logic in cell biology (cytology: only structures)
• Cell is composed of two basic parts / compartments:
o Cytoplasm
o Nucleus
• There is a difference between:
o Prokaryotic cells without distinct nucleus
o Eukaryotic cells keep their DNA in a nucleus
• Sometimes the nucleus is called organell, but it's complexety makes it a copartement
• Differences between prokaryotic and eukaryotic cells:
, • All cells are enclosed in a plasma membrane across which nutrients and waste materials must pass
• Membranes are formated by amphiphilic phospholpids which have a hydrophilic (water-loving, phosphate) head
group and a hydrophobic (water-avoiding, hydrocarbon) tail
Cytoplasm
• Cytosol - fluid component, in which are contained…
• Organelles: metabolically active structures
o Membranous
o Non-membranous
• Cytoskelleton: determines the shape and motility of eukaryotic cells
• Inclusions: deposits of carbohydrates, lipids, or pigments
• Cell types according to Cells:
o Small (5-10 microm.)
o Medium (11-30 microm.)
o Large (31-100 microm.)
o Giant (101-200 microm.)
• Levels of cellular organization:
• Cells can also differ in shape: Squamous, columnar, cuboidal, spherical, pyramidal, stellate, spindle-shaped,
polyhedral
• Cells can also differ in color:
o Most cells are colorless
o Some cells are pigmented:
• Red blood cells, muscle fibers
• Melanocytes, retinal pigment, epithelium cells
• The cytoskeleton is very important for the complexity of the eukaryotic body, f. e. by allowing skelleton muscles to
contract
• The variety of compartiments in a cell helps the cell to practice division of labor without interference
• Hepatocyte: cell of the liver, which is very active
• Peroxisomes are a type of organell involved in catabolism of branched chain fatty acids
Cell-shapes
• Blood cells have almost the size of a giant cellcs nucleus
• Squamous is the latin word for flakes. Squamos cells are very flat.
• Spherical cells surround a cell, f. e. the oocyte. This way the latter can have up to 200 micrometer, the size of the
eye, so they can be seen under the microscope.
• Osteocytes, the cells of bones, are so called "stellate cells". They can transfer molecules from one to another,
because their cytoplasms are connected
• The shape of hepatocytes have almost hexagonic shape.
• Die Dauer und damit die Häufigkeit des Einsatzes von Medikamenten hängt von den Enzymen ab, die die
verarbeitenden Zellen enthalten. Je nach Beschaffenheit werden Medikamente schneller oder langsamer abgebaut.
Präsentation: Methods
• Thicker things normally have tissues which can be sliced very easily, others do not. Therefore they must be
processed: They get fixated, dehydradet (wasser wird durch ethanol ersetzt), cleared (ethanol wird entfernt),
infiltrated and embedded. The tissues are now surrounded by paraffin, which can be cutted by a microtone
, • Kryomicrotone freezes the tissue, helping to skip some steps of the histological processing
• H&E (HE), hematoxylin and eosin are the most common basis of all dyes. Hematoxylin stains the DNA, eosin the
other cytoplasmic components
• PAS stains help to indentify different celltypes
Methods
• Methods of study <> organizational levels:
o Atoms
o Molecules
o Cells
o Tissues
o Organs
o Organ systems
• Corrosion cast:
o Injection of a stained fluid
o Hardening of the material
o Processing with concentrated acid or alkaline solution to dissolve tissue content
o Conservation of the cast
• Preparation of tissues (histological processing):
o Most common procedure: preparation of histological sections or tissue slices that can be studied with the aid
of the light miscroscope
o Under the light microscope, tissues are examined via light beam
o Tissues and organs must be sectioned to obtain thin, translucent sections
• Stages of preparation (1-2 days):
o Fixation: object is placed in fixative solutions
o Dehydration: series of increasingly more concentradet alcohol solutions which effectively removes all water
from the tissue
o Clearing: alcohol and melted paraffin.
o Infiltration: At 58°, the object ecomes completely infiltrated with melted paraffin
o Embedding: Parrafin is allowed to harden. The resulting paraffin block is trimmed to expose the tissue for
sectioning.
o Slicing: The object is sectioned in a Microtome
• An alternate way is rapid freezing of the object through a cryostat. This process is much more faster than the
normal embedding (~30 minutes), so it is commonly used within surgeries.
• Staining:
o Microscopically sections must be stained
o Tissue components with a net negativ charge (anionic) stain more readily with basic dyes and are termed
basophilic
o Cationic components, such as proteins with many ionized amino groups, have affinity for acidic dyes and are
termed acidophilic
• The most commonly used dye is a combination of hematoxylin and eosin (H&E)
o Hematoxylin stains DNA of the cell nucleus and other acidic structures (such as RNA-rich portions of the
cytoplasm and the matrix of cartilage) blue
o Eosin stains other cytoplasmic components and collagen pink
• Peioric acid-Schiff (PAS) reaction shows glycoproteins:
o A ubiquitous free polysaccharide in animal cells is glycogen, which can be demonstrated by PAS in liver,
striated muscle, and other tissues where it accumulates
o With PAS, staining is most intense at the cell surface, where projectin microvilli have a prominent layer of
glycoproteins (arrow head) and in the mucin-rich secretory granules of goblet cells
Microscopy
• Light Microscopy (LM)
o Based on the interaction of light and tissue components
o Used to reveal and study tissue features
o Maxmal resolving power of the light microscope is approx. 0,2 microm.; this power permits good images
magnified 1000-1500 times. Objects smaller or thinner than 0,2 microm. Cannot be distinguished
• Two types of LM:
o Bright-field microscopy - stained preparations are examined by means of ordinary light that passes through
the specimen
o Fluorescence microscopy: tissue sections are irradiatet with a certain wavelength of light and the emission is
in another wavelength
• Resolving power R - the smalles distance between two particles at which they can be seen as seperate objects
, • Digital imagining techniques
o Employ computer technology to capture and manipulate histologic images, without the use of film
o Advantages
• Immediate visualizatio
• Digital modification
• Capability of enhancing
• Phase-contrast microscopy
o Lens system that produces visible images from transparent objects
o Based on the principle that light changes speed when passing through structures with different refractive
indices
o Structures appear lighter or darker
o Does not require fixation or staining: observation of living cells possible.
• Differential interference microscopy (Nomarski optics): Produces an image with a more apparent three-
dimensional aspect than in routine phase contrast microscopy
• Epifluorescence (conventional fluorescence): a method of collecting reflected visible light emitted by UV
excitation
• Confocal microscopy:
o Avoids stray light and achieves greater resolution by using
• Small point of high intensity light provided by a laser
• A plate with a pinhole aperture in front of the image detector
o Creating optical sections at series of focal planes through the specimen allows them to be digitally
reconstructed into a 3D image
• Deconvolution: looks at each voxel (3D pixel) and determines its relationship with the voxels around it. It then
either substracts out what it thinks is blur from nearby bright voxels (easy way) or moves out focus light back to its
voxel of origin (hard way)
Cell: Introduction
History
• Robert Hooke introduced the term "cell" when he looked at cork and named his findings cellule / cellula.
• Some of his obversasions are basic principles of cell theory:
1. All living cells are comprised of cells
2. Cells are the smalles "living" unit in an organism
3. (Cells come from previously existing cells)
• Anton van Leeuwenhoek was a master of microscopy and was the first who observed living cells
• Three German scienists from the early 19 century completed the early observation to a modern cell theory
o Rudolf Virchow: founder of the modern pathology. "All cells come from preexisting cells"
o Schleiden (plants) & Schwann (animals) used the work of Virchow to better it
Cell-function
• Form-follows-function-principle
• Heredity: central definition of life
o Orderly structures are generated but without the same type of link between the pecularities of parents and of
the offspring
• Vehicle for hereditary information: an aggregate of more than 1013 cells generated by cell division from a single cell.
The single cell, therefore, is the vehicle for the hereditary information
• The four main families of small organic molecules in cells:
• Three families of macromolecules:
• Each macromolecule is a polymer formed from small molecules (called
monomers) linked together by covalet bond.
• Macromolecules are by weight the most abundant carbon-containing
molecules in a living cell
• Macromolecules with complementary surfaces can bind tightly through
noncovalent bonds
• Flow of logic in cell biology (cytology: only structures)
• Cell is composed of two basic parts / compartments:
o Cytoplasm
o Nucleus
• There is a difference between:
o Prokaryotic cells without distinct nucleus
o Eukaryotic cells keep their DNA in a nucleus
• Sometimes the nucleus is called organell, but it's complexety makes it a copartement
• Differences between prokaryotic and eukaryotic cells:
, • All cells are enclosed in a plasma membrane across which nutrients and waste materials must pass
• Membranes are formated by amphiphilic phospholpids which have a hydrophilic (water-loving, phosphate) head
group and a hydrophobic (water-avoiding, hydrocarbon) tail
Cytoplasm
• Cytosol - fluid component, in which are contained…
• Organelles: metabolically active structures
o Membranous
o Non-membranous
• Cytoskelleton: determines the shape and motility of eukaryotic cells
• Inclusions: deposits of carbohydrates, lipids, or pigments
• Cell types according to Cells:
o Small (5-10 microm.)
o Medium (11-30 microm.)
o Large (31-100 microm.)
o Giant (101-200 microm.)
• Levels of cellular organization:
• Cells can also differ in shape: Squamous, columnar, cuboidal, spherical, pyramidal, stellate, spindle-shaped,
polyhedral
• Cells can also differ in color:
o Most cells are colorless
o Some cells are pigmented:
• Red blood cells, muscle fibers
• Melanocytes, retinal pigment, epithelium cells
• The cytoskeleton is very important for the complexity of the eukaryotic body, f. e. by allowing skelleton muscles to
contract
• The variety of compartiments in a cell helps the cell to practice division of labor without interference
• Hepatocyte: cell of the liver, which is very active
• Peroxisomes are a type of organell involved in catabolism of branched chain fatty acids
Cell-shapes
• Blood cells have almost the size of a giant cellcs nucleus
• Squamous is the latin word for flakes. Squamos cells are very flat.
• Spherical cells surround a cell, f. e. the oocyte. This way the latter can have up to 200 micrometer, the size of the
eye, so they can be seen under the microscope.
• Osteocytes, the cells of bones, are so called "stellate cells". They can transfer molecules from one to another,
because their cytoplasms are connected
• The shape of hepatocytes have almost hexagonic shape.
• Die Dauer und damit die Häufigkeit des Einsatzes von Medikamenten hängt von den Enzymen ab, die die
verarbeitenden Zellen enthalten. Je nach Beschaffenheit werden Medikamente schneller oder langsamer abgebaut.
Präsentation: Methods
• Thicker things normally have tissues which can be sliced very easily, others do not. Therefore they must be
processed: They get fixated, dehydradet (wasser wird durch ethanol ersetzt), cleared (ethanol wird entfernt),
infiltrated and embedded. The tissues are now surrounded by paraffin, which can be cutted by a microtone
, • Kryomicrotone freezes the tissue, helping to skip some steps of the histological processing
• H&E (HE), hematoxylin and eosin are the most common basis of all dyes. Hematoxylin stains the DNA, eosin the
other cytoplasmic components
• PAS stains help to indentify different celltypes
Methods
• Methods of study <> organizational levels:
o Atoms
o Molecules
o Cells
o Tissues
o Organs
o Organ systems
• Corrosion cast:
o Injection of a stained fluid
o Hardening of the material
o Processing with concentrated acid or alkaline solution to dissolve tissue content
o Conservation of the cast
• Preparation of tissues (histological processing):
o Most common procedure: preparation of histological sections or tissue slices that can be studied with the aid
of the light miscroscope
o Under the light microscope, tissues are examined via light beam
o Tissues and organs must be sectioned to obtain thin, translucent sections
• Stages of preparation (1-2 days):
o Fixation: object is placed in fixative solutions
o Dehydration: series of increasingly more concentradet alcohol solutions which effectively removes all water
from the tissue
o Clearing: alcohol and melted paraffin.
o Infiltration: At 58°, the object ecomes completely infiltrated with melted paraffin
o Embedding: Parrafin is allowed to harden. The resulting paraffin block is trimmed to expose the tissue for
sectioning.
o Slicing: The object is sectioned in a Microtome
• An alternate way is rapid freezing of the object through a cryostat. This process is much more faster than the
normal embedding (~30 minutes), so it is commonly used within surgeries.
• Staining:
o Microscopically sections must be stained
o Tissue components with a net negativ charge (anionic) stain more readily with basic dyes and are termed
basophilic
o Cationic components, such as proteins with many ionized amino groups, have affinity for acidic dyes and are
termed acidophilic
• The most commonly used dye is a combination of hematoxylin and eosin (H&E)
o Hematoxylin stains DNA of the cell nucleus and other acidic structures (such as RNA-rich portions of the
cytoplasm and the matrix of cartilage) blue
o Eosin stains other cytoplasmic components and collagen pink
• Peioric acid-Schiff (PAS) reaction shows glycoproteins:
o A ubiquitous free polysaccharide in animal cells is glycogen, which can be demonstrated by PAS in liver,
striated muscle, and other tissues where it accumulates
o With PAS, staining is most intense at the cell surface, where projectin microvilli have a prominent layer of
glycoproteins (arrow head) and in the mucin-rich secretory granules of goblet cells
Microscopy
• Light Microscopy (LM)
o Based on the interaction of light and tissue components
o Used to reveal and study tissue features
o Maxmal resolving power of the light microscope is approx. 0,2 microm.; this power permits good images
magnified 1000-1500 times. Objects smaller or thinner than 0,2 microm. Cannot be distinguished
• Two types of LM:
o Bright-field microscopy - stained preparations are examined by means of ordinary light that passes through
the specimen
o Fluorescence microscopy: tissue sections are irradiatet with a certain wavelength of light and the emission is
in another wavelength
• Resolving power R - the smalles distance between two particles at which they can be seen as seperate objects
, • Digital imagining techniques
o Employ computer technology to capture and manipulate histologic images, without the use of film
o Advantages
• Immediate visualizatio
• Digital modification
• Capability of enhancing
• Phase-contrast microscopy
o Lens system that produces visible images from transparent objects
o Based on the principle that light changes speed when passing through structures with different refractive
indices
o Structures appear lighter or darker
o Does not require fixation or staining: observation of living cells possible.
• Differential interference microscopy (Nomarski optics): Produces an image with a more apparent three-
dimensional aspect than in routine phase contrast microscopy
• Epifluorescence (conventional fluorescence): a method of collecting reflected visible light emitted by UV
excitation
• Confocal microscopy:
o Avoids stray light and achieves greater resolution by using
• Small point of high intensity light provided by a laser
• A plate with a pinhole aperture in front of the image detector
o Creating optical sections at series of focal planes through the specimen allows them to be digitally
reconstructed into a 3D image
• Deconvolution: looks at each voxel (3D pixel) and determines its relationship with the voxels around it. It then
either substracts out what it thinks is blur from nearby bright voxels (easy way) or moves out focus light back to its
voxel of origin (hard way)
