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Questions and Answers
What is the main function of the nucleolus?
What is the main function of the nucleolus?
mRNA synthesis; facilitates protein-making activity
Which organelle is extensively present in cells with high secretory activity of proteins like neurons and pancreatic acinar cells?
Which organelle is extensively present in cells with high secretory activity of proteins like neurons and pancreatic acinar cells?
The _______ is a carbohydrate-rich covering of a cell membrane.
The _______ is a carbohydrate-rich covering of a cell membrane.
glycocalyx
The smooth endoplasmic reticulum lacks bound ribosomes (true/false)?
The smooth endoplasmic reticulum lacks bound ribosomes (true/false)?
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What is histology?
What is histology?
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Which type of tissue describes cells that produce extra-cellular matrix and serve to link or support other specialized tissues?
Which type of tissue describes cells that produce extra-cellular matrix and serve to link or support other specialized tissues?
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Marie F.X. Bichat introduced the term 'histology' in medical sciences.
Marie F.X. Bichat introduced the term 'histology' in medical sciences.
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What does cytology encompass?
What does cytology encompass?
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Histology is equally important as gross anatomy, biochemistry, molecular physiology, and the study of disease processes as they are all inter-related.
Histology is equally important as gross anatomy, biochemistry, molecular physiology, and the study of disease processes as they are all inter-related.
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What is the primary function of lysosomes in a cell?
What is the primary function of lysosomes in a cell?
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Which organelle is referred to as the 'powerhouse of the cell'?
Which organelle is referred to as the 'powerhouse of the cell'?
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What is the name of the organelle responsible for forming microtubules during mitosis? It is the _______
What is the name of the organelle responsible for forming microtubules during mitosis? It is the _______
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Microfilaments mainly consist of myosin for intracellular contractility.
Microfilaments mainly consist of myosin for intracellular contractility.
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Match the organelle with its function:
Match the organelle with its function:
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What is the most common protein found in animals?
What is the most common protein found in animals?
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Which type of collagen is present in skin, bone, and tendon?
Which type of collagen is present in skin, bone, and tendon?
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Elastic fibers provide 'springiness' and stretchability to tissues.
Elastic fibers provide 'springiness' and stretchability to tissues.
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Simple squamous epithelium is composed of one layer of thin __________ cells.
Simple squamous epithelium is composed of one layer of thin __________ cells.
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Which type of epithelium is fan-shaped and expands uniformly with the accumulation of mucin granules?
Which type of epithelium is fan-shaped and expands uniformly with the accumulation of mucin granules?
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What type of cells are interspersed between typical columnar cells?
What type of cells are interspersed between typical columnar cells?
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Keratinization normally occurs in all types of epithelium.
Keratinization normally occurs in all types of epithelium.
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What is the function of monocytes in the body?
What is the function of monocytes in the body?
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Goblet cells contain granules of ________.
Goblet cells contain granules of ________.
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Which of the following is classified as an apocrine gland?
Which of the following is classified as an apocrine gland?
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______ epithelium lines the walls of blood vessels, heart, and lymph vessels.
______ epithelium lines the walls of blood vessels, heart, and lymph vessels.
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Match the types of glands with their characteristics:
Match the types of glands with their characteristics:
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Myoepithelial basket cells regulate fluid flow and control the entry and exit of nutrients.
Myoepithelial basket cells regulate fluid flow and control the entry and exit of nutrients.
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What is the function of the Golgi silver stain?
What is the function of the Golgi silver stain?
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Cells are the basic structural units of all living organisms according to the cell theory.
Cells are the basic structural units of all living organisms according to the cell theory.
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Define shrinkage artifact in tissue processing.
Define shrinkage artifact in tissue processing.
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The __________ is the colorless material comprising the living part of a cell, including the cytoplasm, nucleus, and other organelles.
The __________ is the colorless material comprising the living part of a cell, including the cytoplasm, nucleus, and other organelles.
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Match the following cell properties with their functions:
Match the following cell properties with their functions:
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What is the function of microvilli?
What is the function of microvilli?
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What type of cells provide communication between adjacent cells?
What type of cells provide communication between adjacent cells?
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Basement membrane is a living substance produced by epithelial cells.
Basement membrane is a living substance produced by epithelial cells.
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The fibers in loose (areolar) connective tissue include collagen, elastic, and ________________ fibers.
The fibers in loose (areolar) connective tissue include collagen, elastic, and ________________ fibers.
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Study Notes
Histology: Definition and Importance
- Histology is the study of the structure of biological material and the ways in which individual components are structurally and functionally related.
- It is equally important as gross anatomy, biochemistry, molecular physiology, and study of disease processes as they are all inter-related.
- Knowledge of normal histological appearances is essential as it is a prerequisite in studying abnormal or pathological structures.
History of Histology
- Histology began with the discovery and development of the first microscopes and techniques for preparing microscopic specimens.
- French gross anatomist Marie F.X.Bichat introduced the word "tissue" in medical sciences in the 18th century.
- Bichat classified tissues into four types: epithelial, muscular, nervous, and connective tissues.
Methods of Studying Histology
Cell Culture Technique
- Involves growing cells in a controlled environment.
Microscopic Examination of Tissue Sections
- There are two types: paraffin technique and frozen section technique.
- Paraffin technique involves steps such as fixation, washing, dehydration, clearing, embedding, sectioning, and staining.
- Frozen section technique involves rapid freezing and sectioning of tissue samples.
Other Techniques
- Stained smears
- Transmission Electron Microscopy (TEM)
- Scanning Electron Microscopy (SEM)
- Freeze-Fracturing Technique
- Autoradiography
- Immunocytochemistry
- Histochemistry
Paraffin Technique
Fixation
- Stops postmortem autolysis (self-digestion) of tissue samples.
- Minimizes changes in the in vivo morphology of tissues.
Washing
- Removes excess fixative from tissue samples.
Dehydration
- Removes water from tissue samples and introduces ethanol.
Clearing
- Removes ethanol from tissue samples and introduces a clearing agent.
Embedding
- Infiltrates tissue samples with a solution that later solidifies to allow thin sectioning.
Sectioning
- Cuts tissue blocks into thin sections using a microtome.
Staining
- Uses dyes to distinguish different components of tissue sections.
Electron Microscopy
Transmission Electron Microscopy (TEM)
- Uses an electron beam to provide contrast and resolution.
Scanning Electron Microscopy (SEM)
- Uses an electron beam to provide depth of focus and three-dimensionality.
Artifacts
- Structures or features in tissue resulting from poor handling or improper processing.
- Examples: shrinkage, dark precipitates, folds, wrinkles, scratches, chatter, and bubbles.
Cell Theory
- Enunciated by Theodore Schwann in 1838 and 1839.
- States that all living things are composed of cells, and that cells can only arise from pre-existing cells.
Protoplasm
- The colorless material comprising the living part of a cell.
- Functions: metabolism, irritability, contractility, secretion, conductivity, endocytosis, exocytosis, growth, maintenance, and reproduction.### Cellular Structure and Function
- Cell is the basic structural and functional unit of living organisms.
- Cellular structure consists of:
- Protoplasm (cytoplasm and nucleoplasm)
- Nucleus (control center of the cell)
- Cell membrane (plasma membrane)
- Cellular function includes:
- Growth (increase in number or size of cells)
- Maintenance (renewal and replacement of cells)
- Reproduction (increase in number of cells through mitosis)
- Excretion (removal of waste products)
Nucleus
- Nucleus is the command and control center of the cell.
- Parts of the nucleus:
- Nuclear membrane (envelope)
- Nucleoplasm (ground substance of the nucleus)
- Chromatin (DNA-containing granules)
- Nucleolus (site of mRNA synthesis)
- Nucleus is broken down and reconstructed during each cell cycle.
Cell Morphology
- Cell shape is influenced by functional specialization.
- Cells have organized structures with predictable positions.
- Cell size varies among different species and within the same species.
Organelles
- Organelles are living components of the cell.
- Classified as active and passive organelles.
- Active organelles:
- Participate in metabolic processes
- Classified as membranous (e.g., cell membrane, ER, Golgi apparatus) and non-membranous (e.g., ribosomes)
- Passive organelles:
- Do not participate in metabolic processes
- Include inclusions (e.g., glycogen, lipids, pigments)
Cell Membrane
- Cell membrane is a selective barrier that controls the movement of materials in and out of the cell.
- Structure of the cell membrane:
- Trilaminar (three-layered) structure with inner and outer dark (osmiophilic) leaflets of lipids separated by a middle light (osmiophobic) leaflet of fatty acids
- Cell coat (glycocalyx) is a carbohydrate-rich covering of the cell membrane
Cytoplasm
- Cytoplasm is the medium in which the various formed elements are suspended.
- Parts of the cytoplasm:
- Cytosol (matrix or ground substance)
- Formed elements (organelles and inclusions)
Endoplasmic Reticulum (ER)
- ER is a system of hollow membranous structures (tubules or flattened vesicles) extending throughout the cytoplasm.
- There are two types of ER:
- Rough ER (RER) with attached ribosomes that synthesize proteins for extracellular use
- Smooth ER (SER) with enzymes associated with various specialized functions
Golgi Apparatus
- Golgi apparatus is a complex of flattened membranous saccules and associated vesicles.
- Functions of the Golgi apparatus:
- Concentrates and packages secretory products
- Synthesizes polysaccharides
- Produces lysosomes
Lysosomes
- Lysosomes are membrane-bound vesicles containing enzymes called acid hydrolases.
- Functions of lysosomes:
- Degrade material taken up from outside the cell
- Digest obsolete components of the cell itself
- Types of lysosomes:
- Phagolysosome (heterophagic vacuole)
- Autophagic vacuole
- Multivesicular body
Mitochondria
- Mitochondria are the "powerhouse of the cell" as they generate ATP.
- Structure of mitochondria:
- Double membrane structure with outer and inner walls
- Inner wall forms platelike or tubular folds (cristae)
- Cristae contain matrix rich in granules (calcium ions)
- Functions of mitochondria:
- Generate ATP
- Participate in Kreb's citric acid cycle
- Contain DNA and RNA
Cytoskeleton
- Cytoskeleton is the internal skeleton of a cell.
- Components of the cytoskeleton:
- Microfilaments (actin)
- Myosin
- Microtubules
- Intermediate filaments
- Functions of the cytoskeleton:
- Maintains cell shape
- Participates in cell division
- Involved in cell migration and muscle contraction### Intermediate Filaments
- Diameter: 8-10 nm
- Types: neurofilaments, glial filaments, keratin filaments, and vimentin filaments
- Function: maintain cell shape, important in epithelial cell adhesion
Passive Organelles
- Do not participate in metabolic processes
- Provide anchorage or support to various cellular components
- Examples: centrioles, basal bodies, microbodies (peroxisomes), microtubules, and filaments & fibrils
Microfilaments
- Consist of actin protein
- Diameter: 5-8 nm
- Length: 1.0 um in muscle cells, microvilli, and stereocilia
- Function: involved in cell movement, changes in cell shape
Microtubules
- Composed of tubulin protein
- Diameter: 20-50 nm
- Function: form cytoplasmic support of cilia, flagella, and spindle fibers
- Involved in cell movement, separation of chromosomes during mitosis
Centrioles
- Contained within centrospheres
- Present in muscle cells
- Length: 1.5 um
- Diameter: 15 nm
- Function: form microtubules during mitosis
Basal Bodies
- Similar in structure to centrioles
- Form the base of cilia in ciliated cells
Microbodies or Peroxisomes
- Similar to mitochondria but smaller
- Function: not known
Microfilaments and Microfibrils
- Made up of tubulin
- Diameter: 6-10 nm
- Function: involved in cell adhesion, formation of terminal web
Inclusions
- Non-living, non-moving, membrane-bound materials
- Examples: secretory inclusions, nutritive inclusions, and miscellaneous inclusions
Secretory Inclusions
- Secretory products of cells
- Examples: enzymes, acids, proteins, mucus
Nutritive Inclusions
- Nutritive materials produced by or stored in the cell
- Examples: glycogen granules, lipid droplets
Miscellaneous Inclusions
- Examples: lipofuscin, melanin, and hemosiderin pigments
Tissues
- A group of similar cells and their extracellular products
- Perform a specific function or a spectrum of related functions
Connective Tissue
- Cells perform a specific function or a spectrum of related functions
- Composed of cells, intercellular substance, and fluid
- Intercellular substance: composed of collagen fibers, fibroblasts, chondroblasts, and osteoblasts
Collagen Fibers
- Predominant fiber in most connective tissue
- Composed of tropocollagen molecules
- Types: Type I, Type II, Type III, and Type IV
Elastic Fibers
- Provide "springiness" and stretchability to the tissue
- Stain with Verhoeff's stain
Reticular Fibers
- Composed of Type III collagen
- Stain with silver stain
- Form the framework of lymphoid organs
Nervous Tissue
- Makes up the organs of the nervous system
- Composed of cells, intercellular substance, and fluid
Epithelial Tissue
- Covers external surfaces of the body and forms exocrine glands
- Characterized by: polarity, avascularity, high turnover rate, and embryonic origin
- Types: simple squamous epithelium, simple cuboidal epithelium, simple columnar epithelium, and pseudostratified epithelium
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Description
This quiz covers the study of the structure of biological materials, including cell culture techniques, microscopic examination of tissue sections, and other methods used in histology.
