Week 1 - Intro to histology Flashcards
What is histology
Microscopic anatomy
What is a prokaryote
A cell that has no nucleus, for example bacteria
What is a eukaryote
Cells that have a nucleus and cytoplasm
What are the 3 main things that make up a cell and what are they
Cytosol (intracellular fluid)
Cytoskeleton (network protein filaments which give structure)
Organelles (a sub cellular structure which carries out one or more function)
What 3 roles of the cell membrane
To maintain the structure of the cell
To adhere to other membranes in order to form a barrier in skin cells for example
To maintain homeostasis
What is a cellular projection and name 2 examples
A cellular protuberance (dendrites, axons, cilia
What is the definition of a tissue
Groups of similar cells working together to carry out a common function
What 2 things make up tissues
Cells and extracellular matrix
What is a tissue containing the same type of cell
Simple tissue
What is a tissue containing multiple types of tissue
Compound tissue
What do you call a tissue that carries out a specific function in an organ
Parenchyma (working tissue)
What do you call a tissue that provides scaffolding and nutrition
Stroma tissue
What is an organ
Several tissue types which perform a specific function
What is an organ system
A system of organs that work together (e.g urinary system comprises of ureters, bladder)
Name 4 types of tissue and their function
Connective - supports and protects
Epithelial - lines/covers body surfaces
Nervous - generates electrical signals in response to environment
Muscle - contains cells which contract to generate a force
Describe briefly the process of epithelial cancer
One of the epithelial cells despecialises due to a genetic mutation. Cancerous cell proliferates. Cancerous cell spreads from the initial site/primary site to another part of the body through metastasis
What is metastasis
the spread of disease from primary site to secondary site
What is dissemination
Spread of disease
What are the 4 stages of tissue processing for histology and give a brief description of each step
Fixation - freezing sample (-80 degrees) or use an aldehyde such as formaldehyde
Embedding - sample is embedded in paraffin wax which provides support for sectioning
Sectioning - using a microtome to cut thin sections
Staining - specific and non-specific staining
What is the most common stain and what does each component target
H+E (haematoxylin and eosin) H is basic and therefore targets acids such as DNA
E is acidic and therefore targets bases such as the cytoplasm
What does PAS target and what does PAS stand for
Periodic acid/schiff targets carbohydrates and glycogen thus turning the liver since it contains lots of glycogen, mucus, basement membranes and brush borders
What colour do lipids appear as and why
They appear clear in colour since the lipids were dissolved by the paraffin wax (I think)
What can be used as an alternative to increase the resolution of histology
Electron microscopy
Where are cells joined together when they are bound by membranes?
cell junctions
Describe the basic structure of epithelial tissue
Continuous sheets of epithelial cells that are 1 or more layers thick
List 3 main epithelial cell locations and give examples
External body surfaces e.g epidermis layer of skin
Closed cavities
Body tubes e.g respiratory tract
Secretory portions of glands and ducts
Sensory receptive regions of sensory organs e.g ear/nose
Describe the density of epithelial cells
In close contact
What are the binding points called between epithelial cells
cell to cell junctions
What do gap junctions allow between epithelial cells
communication between cells
Where are epithelial cells positioned
They are always attached to the basement membrane
Why are epithelial cells bound to basement membrane
Since epithelial cells are polarised
What does the basement membrane act as
A selective filtration barrier
Describe the energy source of epithelial cells
Avascular so rely on nutrients from connective tissue below
Which region of epithelial cell points outwards
The apex
What can sometimes be found on the apex of cells
Cilia
Name 5 functions of epithelial cells
They can act as a barrier for example skin which is susceptible to abrasion
Can protect toxic molecules and microorganisms from entering the body
Some epithelium can allow substances through for example diffusion of o2/co2 across the lung epithelial tissue
Involved in secretion in the glands
Can make special senses such as hearing/smell through combining with nervous tissue
What are the 2 main types of epithelia and give a description
Covering epithelia - cover/line all body surfaces, cavities and tubes
Glandular epithelia - collections of secretory epithelial cells that synthesise and secrete products.
Which body system is glandular epithelia very common in
Gastroenterology
Name and describe the two subcategories of glandular epithelia
Exocrine epithelia which remain continuity with surface and secrete via a duct
Endocrine glands which lose contact with surface and secrete directly into bloodstream
Give an example of an exocrine gland
Salivary gland
Give an example of an endocrine gland
Thyroid gland
What does simple mean and give description
Single layer- good for absorption but fragile
Stratified
2 or more layers - good for protection
Pseudostratified
One layer with a mixture of cell shapes (looks stratified but not all cells reach the surface
Define squamous
Flat shaped
Cuboidal
Cube shaped
Columnar
tall cylindrical shape
Transitional
will readily change shape
Simple squamous epithelium
Flat, nuclei are squashed
Used for diffusion, secretion and absorption but little barrier/protection against friction
Found in lining of blood vessels
Simple Cuboidal
Single layer, cube shaped, some have microvilli
Good for diffusion, secretion absorption
Found in surface of ovaries
Simple Columnar
single layer of tall narrow cells, some have cilia
Used for movement of substances, absorption and secretion. More protection
Found in glands
Stratified squamous
Multiple layers, cube shaped, more flat towards surface. Can be keratinised or non-keratinised (moist)
Prevent water loss, protection from abrasion, infection barrier
Keratinised=skin
Non-keratinized = mouth, throat
What makes non-keratinised layer soft
a layer of fluid on outside
What makes keratinised stratified epithelium more rough
Keratinised layer with dead cells which have had their cytoplasm replaced by keratin
Pseudostratified Epithelium
Single layer but looks like lots of layers since some cells reach free surface and some do not. Usually have cilia.
Synthesises and secretes mucus and move foreign particles over the surface
Found in the lining of the nasal cavity, sinuses etc
Transitional Epithelium
Unique type of stratified epithelium that can change shape - cuboidal/columnar when not stretched/flattened when stretched. Number of layers decreases upon stretching since cells shift on top of each other
Used to accommodate fluctuations in the volume of fluid in organs. Protects against caustic effects of urine
Located in urinary bladder
