Introduction to Histology Flashcards
What is Histology?
The study of microscopic structure of biological tissues. Microanatomy. The study of normal cells and tissues using microscopes.
What is Histopathology?
The microscopic study of changes that occur in tissues.
What is a Cell?
the functional unit of all living organisms.
Name the three components of cell theory.
- All living things are composed of one or more cells.
- The cell is the basic unit of life.
- New cells arise from pre-existing cells.
What is a Prokaryote?
A cell with no nucleus. bacteria.
What is an Eukaryote?
A cell with Cytoplasm and a nucleus bounded by a nuclear membrane.
What is the Extracellular matrix?
The material between cells.
- most cells are anchored together by cell junctions.
Name the parts of an Eukaryotic cell.
- Plasma membrane
- Nucleus
- Cytoplasm
- Cytosol
- Cytoskeleton
- organelles
What is the role of the plasma membrane?
- The ‘gate keeper’. It is a physical barrier. Allows ions in and secretion of waste products.
- Regulation. It is sensitive to the environment. homeostasis.
- Selectively permeable.
- Some have specialisations like cilia or microvilli.
What are the role of cilia?
Cilia can beat to move the cell or move structures across the cell.
What are the role of microvilli?
Increase surface area of the cell to increase absorption.
What is the nucleus?
Most cells have only 1. It contains the DNA. The largest organelle.
What is the Cytoplasm?
- Fills the rest of the cell.
- Contains various structures called organelles which have defined functions.
- Cytosol
- Cytoskeleton
What is the Cytosol?
Intracellular fluid
what is the Cytoskeleton?
Network of protein filaments that give the cell structure and maintains polarity.
What are organelles?
Individual structures with varying functions.
What are tissues?
- A group of similar cells working together to carry out a common function.
- Tissues = cells + extracellular matrix
What are the functionally specialised cells in tissues and organs called?
Parenchyma - working tissue.
What are the supporting tissues called in tissues and organs?
Stroma - Scaffold and nurition it is surrounding tissue which provides support.
Name the four types of Tissues and their function.
- connective - protects + supports.
- Epithelial - covers/lines body surface (skin).
- Muscle - cells contract to generate force.
- Nervous - generate electrical signals in response to environment.
What is an Organ?
Made up of several tissue types comprised in a recognisible structure.
They perform specific set of fucntions.
What is dedifferation?
when a cell looses its specialisation and begins to compete with other cells for resources.
Occurs in Cancer.
What is metastasis?
Spread of disease producing agency.
What are cells held together by?
Intercellular junctions and the extracellular matrix.
What factors can make the same tissue appear different when using microscopy?
- The method of prep for staining.
- The type of microscopy used.
What is the order for tissue processing for Histology?
- Fixation
- Embedding
- Sectioning
- Staining
What is fixation and the methods to carry it out?
Fixation = preserving the tissue
by …
1. Freezing - at - 80c using dry ice or liquid nitrogen.
2. Chemical Fixation - aldehyde based. Most common method.
What is the benefit of using Chemical Fixation?
The chemical used binds with certain proteins and denatures other ones, hardening the tissue and inactivating enzymes that could damage it.
This kills of bacteria to enhance staining.
What is Embedding and the methods to carry it out?
Provides support for tissue when sectioning by putting into another liquid.
by…
1. Frozen samples
2. Parrafin Wax (most common). - wax insoluble in water so need extra step where water replaced by solvent called Zylene and during this adipose tissue removed so don’t see lipids on imaging.
Artifacts can be introduced at this stage.
What is Sectioning?
Using a Microtome to cut tissue to tiny thin sections.
The thinner the slice the higher the resolution.
It is a 2D representation of a 3D object.
What is Staining?
Staining some cell components bright and a counter stain that colours the rest a different colour based on if the strucutre is Acidic or basic.
This allows you to differentiate between structures.
What is the most common stain used?
H + E - Haemotoxylin + Eosin
H = basic stains acidic structures purplish blue.
E = Acidic stains basic structures red or pink.
What different colours to the Acidic dyes dye basic structures?
Acid Fuschin = red
Aniline Blue = blue
Eosin = red
Oragne G = Orange
What different colours to the Basic dyes dye acidic structures?
Methyl Green = Green
Methylene Blue = blue
Pyronin G = Red
Toludine Blue = blue
What is PAS staining and when would you use it?
Periodic-Acid/ Schiff
For complex Carbohydrates + Glycogen staining.
Tissues stained with PAS are PAS +
(e.g.) liver as lots of glycogen, mucus, basement membrane and brush borders in the intestines.
What happens when you stain lipids?
Tey are optically empty. They show up white as they are dissolved in the process.
What is the Epithelium?
A tightly cohesive sheet of cells that covers or lines body surfaces and forms the functional unit of secretory glands.
What are some key characteristics of Epithelial tissue?
- cells are in close contact
- cells are polarised
- Avascular and noursihed by the BVs in CT instead.
- Covers and protects.
- form glandular structures
- combines with nervous tissue to make special senses.
- line internal cavities, BVs, respiratory/digestive/urinary + reproductive organs.
What are the two types of epithelial tissue?
- Covering epithelia = covers and lines all body surfaces/cavities/tubes.
- Glandular Epithelia = secretory epithelium arranged into glands. invaginations (inside out) epithelium. Glandular organs.
What are exocrine glands?
Retain continuity with surface (secrete via duct).
What are endocrine glands?
lose contact with surface and secrete directly into blood stream.
What are the names for describing epithelia based on the number of layers they have?
- Simple = single layer, fragile, good for absorption + secretion.
- Stratified = 2 or more layers, good for protection.
- Pseudostratified = one layer with mixture of cell shapes - looks stratified but not.
What are the names for describing epithelia based on their shape?
Squamous = flat Cuboidal = cube Columnar = tall cylindrical Transitional = readily change shape to accomodate stretching.
Describe the structure, function and location of
Simple Squamous Epithelium.
Structure: single layer of flat/hexagonal cells. Nuclei flat.
Functon: mainly diffusion, filtration, secretion, absorption, very little barrier protection.
Location: lining of BVs and the heart. Alveoli. lining of serous membranes and some kidney tubules.
Describe the structure, function and location of
Simple Cuboidal Epithelium.
Structure: single layer of cube-shaped cells. some have microvilli.
Function: diffusion, secretion, absorption.
Location: kidney tubules, glands + ducts, lining of terminal bronchioles, surface of ovaries.
Describe the structure, function and location of
Simple Columnar Epithelium.
Structure: single layer of tall thin cells, some have cilia or microvilli.
Function: movement of substances, absorption and secretion, more protection than flatter cells.
Location: glands + some ducts, bronchioles, auditory tubes, uterus, uterine tubes, stomach, intestines, gallbladder, bile ducts, ventricles of brain.
Describe the structure, function and location of
Stratified Squamous Epithelium.
Structure: multiple layers of cells that are cube-shaped in basal layer and progressively flatten toward the surface.
can be.. nonkeratinized (moist) or keratinized.
Function: protection against abrasion, a barrier against infection, reduction of water loss.
Location: keratinized - skin
non = mouth, throat, larynx, esophagis, anus, vagina, inferior urethra, cornea.
in keratinized - cytoplasm of cells at the surface is replaced by keratin and these cells are dead.
Describe the structure, function and location of Pseudostratified Epithelium
Structure: single layer but some cells reach the surface and some don’t. All touch basement membrane. Nuclei are at different levels. Almost always associated with goblet cells.
Fucntion: synthesize and secrete mucus + move mucus that contains foreign particles over the surface.
Location: lining of nasal cavity, nasal sinuses, auditory tubes, pharynx, trachea, bronchi.
Describe the structure, function and location of
Transitional Epithelium.
A unique type of stratified epithelium.
Structure: cuboidal/ columnar when not stretched, squamous/flattened when stretched.
Number of layers decreased when stretched as cells shift on top of eachother.
Function: accomodate fluctuations in volume of fluid in organs or tubes. Protects against the caustic effects of urine.
Location: lining of urinary bladder, ureters, superior urethra, pelvis of the kidney.
