Histology Flashcards
What is histology
Looking at tissues
What do we use to look at cells and tissues?
Light microscope
What are the steps in preparing a sample?
- Tissue collection
- Fixation (10% formation) & trimming
- Dehydration, use a series of alcohols up to 100% concentration
- Paraffin embedding
- Sectioning with microtome (tend to curl up)
- Straighten sections on water bath
What measurements does microtome section it to?
3-4um
What are the two different counter stains most commonly used and what are their colours?
Haematoxylin —> blue
Eosin—> pink
What does haemolotoxin stain
Genetic material, so DNA and RNA
What does eosin stain?
Proteins
What is the epithelium?
The tissue that covers all of the internal and external surfaces of the body
What do all epithelium sit on?
Basement membrane
Does epithelium tissue contain blood vessels?
No
What are apical modifications/
When outer surface is specialised in one way
What is single epithelium
Every cell attached to basement memtsne
How can we classify epithelium?
- Morphology —> cell shape
- Function —> glandular vs non glandular
What are the four different types of simple epithelium
- Simple squamous —> single flat layer —> round blood vessels
- Simple cuboidal —> renal tubules
- Simple columnar —> tend to have apical modifications —> gall bladder
- Simple pseudostratified columnar—> nucleus at different levels so doesn’t really look like one layer —>trachea
What are endothelium?
Epithelium that line the blood vessels
What are stratified epithelium?
More than one cell layer
What are the different examples of stratified epithelium?
- Stratified squamous —> older more mature cells move up the layer and become flat —> oesophogus
- Stratified cuboidal —> nipple
- Stratified columnar —> nipple
- Transitional epithelium —> can change shape to allow tissue to stretch —> urinary bladder
What are some uses of simple cuboidal cells
Secretion/ absorption
In kidney, thyroid, ducts
What are some uses of simple columnar epithelial cells?
Secretion/ absorption
Intestine, female reproductive tract
What is the function of simple pseufodtratified epithelial cells
Secretion/ movement of particles along tubular organs
Trachea, bronchi etc.
What is stratified squamous epithelium used
Most common
Protects underlying tissues
Covers most external body parts
What is the difference in kerstinisation in small vs large animal?
Small —> in skin, outer layers. Doesn’t occur where tissues remain moist e.g. vagina, oral cavity (not internally)
Large —> in skin, oral cavity, oesphogous and non glandular part
What is the uses of stratified cuboidal and columnar epithelia?
Not abundant
In areas of transition between simple and stratified epithelia
Respiratory ducts
Ducts if exocrine glands
What can we classify epithelial glands
- Method of secretion (endocrine vs exocrine)
- Type of secretion (for exocrine0
- Shape
- Cell numbers
What are endocrine glands
Glands that lack a duct system and no connections to external or internal surfaces
Produce hormones
Near blood vessels
What are exocrine glands
Secrete to a lumen or free surface
What are the two classifications of exocrine glands
Number of cells —> unicellular vs multicellular
Shape of the secretory component —> tubular bs acinar
Shape of tubular system —. Simple (one unbranched tube) or compound (branched tubules)
Type of secreatory product —> serous (clear watery fluid) or mucous (more viscous fluid like goblet cells) or mixed
What are the three different types of secretion?
Merocrine —> exocytosis (cell membrane remains intact) most common
Holocene —> cell membrane ruptures (cell dies)
Apocrine —> decapitation secretion (pinches off)
What are the different types of apical modifications
Cillia-> motile (move)—> respiratory tract or oviduct
Microvilki —> don’t move —> increase SA for absorption
Stereocilla —> long villi —> male reproductive tract
What are adherent junctions
Anchoring
Cells must bind to each other and to the connective tissue
Forms the mechanical stiffness of the tissue
Cells together —> desmosomes
Cells to the extra cellular matrix (basement membrane) —> hemidesmosomes
What are tight junctions
Cells are involved in what enters the body
Entrance of nutrients and compounds must be controlled
Para cellular —> between the cells (controlled by epithelium)
Trans cellular —> through epithelium cells
What are gap junctions
Cells that must communicate with each other
Aqueous channels allowing small molecules to pass through
