Cytology: Origin, Techniques and Classification

The term "cytology" is typically used to refer to the scientific study of cells, the smallest observable building blocks of all living organisms. 

• In 1665, an English scientist named Robert Hooke began microscopic studies of cork, marking the beginning of modern cytology. 
• Dead cork cells caught his eye, and he coined the term "cell" to characterize them.
• Urine cytology, sputum cytology, brush cytology, aspiration cytology, fluid cytology, imprint cytology, and countless others exist.

Read More: Parts of Cell

Key Terms: Cell, fundamental unit of life, Unicellular organism, Multicellular organisms, nucleus, organisms, organ

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Origin of Cytology 

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Both the German biologist Theodor Schwann (1839) and the German botanist Matthias Schleiden (1838) were the first to explicitly explain that cells are the fundamental elements of both animals and plants in the 19th century. In particular, the cell theory has been supported and broadened by numerous facts and explanations.

 

• German embryologist and anatomist Oscar Hertwig created cytology as a distinct field of study in 1892.
• It was based on his hypothesis that organismic activities are merely reflections of cellular processes.
• In 1902–1904, an American geneticist named Walter Sutton and a German naturalist named Theodor Boveri discovered the link between heredity and cell division, laying the groundwork for the field of cytogenetics. 
• In recent years, some experimental chemists and physicists have joined the ranks of cytologists to better understand biological processes.

Read More: Endoplasmic Reticulum

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Techniques of Cytology 

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Researchers in the field of modern cell biology examines several strategies for cultivating and manipulating cells outside of a living creature to advance our understanding of human physiology and anatomy and to develop more effective treatments. Some researchers have been able to improve their understanding of cells because of recent developments in microscopy and technology.

It can be divided into three types as given below

1. Cell culture: It takes advantage of the media's high proliferation rate, producing an abundance of a single cell type and facilitating quick analysis.
2. Fluorescence Microscopy: In this case, fluorescent markers like GFP are employed to label specific parts of a cell. After that, fluorescent markers are excited by a certain wavelength of light and then visualized.
3. Phase-Contrast Microscopy: It takes advantage of the optical property of light to represent the transitions between the solid, liquid, and gas phases as variations in intensity.

Read More: Cell Organelles Types and Functions

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Classification of Cells

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Classification of cells can be of two types– 

1. Prokaryotic cells
2. Eukaryotic cells

• Prokaryotic cells are distinguished from eukaryotic cells by the absence of a cell nucleus or other membrane-bound organelle. 
• As they are little in size compared to eukaryotic cells, prokaryotic organisms are the tiniest form of life. 
• Cytologists typically specialize in studying eukaryotic cells, while microbiologists examine prokaryotic cells.

Read More: What Are Tissues?

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Prokaryotic Cells

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Prokaryotic cells, which are shared by Archaea and Bacteria, do not contain a nuclear membrane. Both of these types of reproduction rely on binary fission. 

• The most common kind of bacteria is rod-shaped, although they can come in spherical and many other forms. 
• Cell wall composition is used to categorize bacteria as gram-negative or gram-positive. 
• Some examples of prokaryotic cells are explained below:

1. Bacterial cells: These microbes are unicellular and can be found in a wide variety of environments, including the human body.

• They vary in form and composition.
• Peptidoglycan is the structural component of the cell wall.
• Pili, flagella, and the bacterial capsule are all features that are only found in bacteria.
• These organisms have plasmids, which are extrachromosomal DNA.
• The ability to create the hard, inactive structures called endospores allows these organisms to endure adverse environments. Once conditions are favorable again, the dormant endospores start to germinate.

2. Archaeal cells: Archaebacteria, like bacteria, are unicellular creatures.

• Hot springs are only one of many harsh settings where they thrive; you can also find them in the dirt, wetlands, and even the bodies of humans.
• They're equipped with flagella and a cell wall. Archaeal cell walls lack peptidoglycan, a component of eukaryotic cell walls.
• Archaeal membranes contain lipids with a different stereochemistry than eukaryotic membrane lipids.
• Archaea, like bacteria, only have one chromosome, which is also circular. They are also plasmid carriers.

Read More: Discovery of Cells

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Eukaryotic Cells

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Cells of plants, animals, protozoa, and fungi are all eukaryotic; they range from unicellular to multicellular and contain organelles of all sizes and forms. The following organelles make up these particular cells:

1. Nucleus: The DNA in the nucleus is organised into chromosomes and serves as the cell's genome and its repository of genetic information. 

• The nuclear envelope protects the nucleus from the outer environment and contains the nuclear pores necessary for protein trafficking. 
• DNA replication and transcription from DNA to RNA both occur here. 
• After that, the RNA is processed and sent to the cytoplasm, where it will undergo translation into a functional protein.

2. Nucleolus: Inside the nucleus is a thick sphere-like structure called a nucleolus. 

• It's also where the rRNA, or ribosomal RNA, that's required for ribosome assembly, is made.

Read More: Discovery of Cells

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Cellular Processes

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Cell metabolism and cellular signaling both are very important processes for the regulation of cells.

1. Cell Metabolism: The series of chemical processes that take place within cells in living things in order to sustain life is known as cellular metabolism. 

• Complex series of regulated biochemical events, or metabolic pathways, are involved in cellular metabolism. 
• These mechanisms let organisms develop and reproduce, preserve their structural integrity, and adapt to changes in their environment.

2. Cell Communication and Signalling: Three processes are involved in cell signalling: signal receipt, signal transduction, and response. 

• However, some signalling molecules, like hormones, can cross the membrane to reach their internal receptors. 
• In the majority of signal receipt, a membrane-impermeable molecule, or ligand, induces a change in a membrane receptor. 
• The intracellular messengers can then convert the signal from the membrane receptor into a cellular response. 
• This intracellular reaction might involve changes in protein activation, transcription, or translation, among many other things.

Read More: Prokaryotic and Eukaryotic Cells

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Things to Remember

• In 1892, the German anatomist and embryologist Oscar Hertwig established cytology as a separate branch of research.
• The nucleus is the central part of the cell.
• Cells are divided into prokaryotes and Eukaryotes based on evolution.
• Plant cells have a cell wall and animal cells do not have it.
• There are different types of cells in the human body.
• Cells are the living building blocks that differentiate living organisms from non-living organisms.
• Cells combine together to form a tissue, tissues combine together to form an organ, organs together form an organ system, organ systems and the rest of the components then form an organism.

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Previous Year Questions

1. Extraction of metal from the ore cassiterite involves...[JEE Advanced 2011]
2. Commonly used vectors for human genome sequencing are...[NEET UG 2014]
3. Interfascicular cambium and cork cambium are formed due to​..
4. Pneumotaxic centre is present in​...[UP CPMT 2007]
5. Reaction of HBr with propene in the presence of peroxide gives….[NEET UG 2004]
6. Assuming the expression for the pressure exerted by the gas on the walls of the container, it can be shown that pressure is...[MHT CET 2016]
7. Which among the following is the strongest acid?...[TS EAMCET 2017]
8. Isopropyl alcohol on oxidation forms​..
9. A vector is not changed if​..
10. Which of the following arrangements does not represent the correct order of the property stated against it?...[JEE Main 2013]