Integrated Histology - Tissue types Flashcards
What does histology mean?
The study of tissue.
Describe the basic stages of tissue section separation.
1 - Tissue collection
2 - Fixation and trimming
3 - Dehydration by exposing to alcohol
4 - Embedded in paraffin which makes it embedded
5 - Sectioned with micrometer
6 - Straightened
7 - Transfer to slide
8 - Staining and cover slipping
What structures would we be looking at when staining a tissue sample with Haematoxylin (blue)?
Genetic material (DNA and RNA)
What structures would we be looking at when using Eosin (pink) to stain a tissue?
Mainly protein (Cytoplasm).
How can epithelium be classified?
Morphology - Cell shape and arrangement of cells
Function - Glandular vs Non-glandular.
What is meant by a ‘Simple epithelium’?
A single layer of cells.
Describe the structure of Simple Squamous epithelium.
- Very thin, best suited for passive transport
- Provide little protection and thus are no found on surfaces subject to high stress.
- Found in Alveoli, vessels and body cavities.
Describe the structure of simple cuboidal and columnar.
- Associated with secretion an/or absorption
- Columnar is made up of tall and thin cells (markedly polarised)
- Columnar also often has apical modifications (cilia and microvilli)
- Found in the intestine, female repro system
- Cuboidal: Thyroid, kidney, secretary portion of many glands
Describe the structure of Pseudostratified Epithelium.
- Nuclei not being orientated on one level, so gives the impression it is multilayered
- All cells rest on basement membrane
- Secretion and movement of particles along the tubular organs
- Also known as respiratory epithelium
- Found in Trachea, Bronchi, Epididymis
What is stratified epithelium?
Multiple layer of cells.
Describe the structure of Stratified squamous epithelium.
- Most common multi-layered epithelia
- Protection of underlying tissues and prevents their desiccation
- Small animal: In the skin, Outer layers undergo keratinisation.
- Large animals: Keratinising stratified squamous epithelium in the skin
Describe the structure of stratified columnar and cuboidal epithelium.
- Not abundant
- Found covering transition between simple and stratified epithelia.
- Respiratory tract, exocrine glands
Describe the structure of Transitional epithelia.
- Only found in the urogenital system and are also known as ‘urothelium’
- Subject to marked variation of internal pressure, cell shape depends on the degree of distension
- Appearance can change from thick stratified columnar to stratified squamous
How can the different tissues be classified?
- Methods of secretion (endocrine or exocrine)
- Type of secretion
- Shape
- Cell numbers
What is an Endocrine gland?
- Glands that lack ducts and have no connection to external or internal surfaces
- Produce hormones
- Near blood vessels
What is an Endocrine gland?
- Secrete its products into a lumen or a free space
- Can be unicellular or multicellular
What different secretary product can a gland produce?
- Serous: Clear, watery fluid
- Mucous: More viscous fluid
- Mixed: Combination of Serous and mucous
What are the different types of secretion?
Merocrine: exocytosis, cell membranes intact (most glands)
Holocrine: Cell membrane ruptures, detachment and cell death
Apocrine: ‘Decapitation secretion’ (pinches of a bit of its own surface wit the secretory product inside
What are thee different apical modifications that epithelia can have?
Cilia: Motile (can move), long cell processes
Microvilli: Non-motile, minute projections found in the epithelia specialised for absorption (massively increase SA)
Sterocilia: Long microvilli
What are the different types of junctions connecting tissue to on another?
- Adherent junctions
- Tight junctions
- Gap junctions
What is an adherent junction?
- Cells that must bind to each other and to basement membrane to assure tissue cohesion
Desmosomes - Cells together
Hemidesmosome - Cells to extracellular matrix
Wha is a Tight junction?
Occluding - Cells that are involved in controlling what enters the body
- Two pathways for this (paracellular and Transcellular pathway)
- The tight junctions limit the paracellular movement of water and molecules
What is a Gap junction?
- Cells from the body must communicate between themselves.
- This is controlled by gap junctions
- Aqueous channels (pore-like) allowing small molecules to pass between two adjacent cells
