Intro to Histology Flashcards
Define a tissue
a group of cells working together to carry out a common function
Define an organ
more tissues of a different nature in a morphologically recognizable
structure
What is parenchymal tissue?
Working tissue/performs the function of an organ
e.g. in heart, the working cells are muscle tissue
What is stromal tissue?
Provides structure and nutrition i.e connective tissue, blood vessels, nerves
What are the four types of tissue?
Describe them.
Muscle, epithelial, connective and nervous
Epithelium: cells closely connected, non-vascularised, polarised cells (ends of the cell are distinct)
Connective: well-vascularised
Describe the relationship between epithelial and connective tissue and how they interact with one another
Epithelial tissue provides protection against infection and dehydration
Connective tissue supports and provides nutrition (as it’s well vascularised)
What happens in epithelial cancer?
Cells lose their polarity, they multiply and break through the basement membrane to the connective tissue. The cancer cells spread from here.
Name the 4 components of the most common staining process
Fixation
Embedding
Sectioning
Staining
Describe the four steps in tissue processing
Fixation: this stops histological processes from happening
- it can be chemical, using aldehydes MOST COMMON
- freezing the tissue using dry ice or liquid nitrogen
Embedding: placing the tissue in a paraffin wax block so it sustains the specimen whilst cutting/sectioning. Pretreatment for paraffin treatment dissolves the fat, so the fat cells appear empty.
Sectioning: specimen is thinly sliced to gain higher resolution
Staining:
– Haemotoxylin-Eosin (MOST COMMON)
H = basic + blue
E = acidic + red
– PAS (Periodic Acid/Schiff)
This is used for staining sugars/carbohydrates = sugars dissolve
Stained cells are called PAS positive.
Give examples of different stains for cell components
Nuclei contain acid in DNA so they are basophilic. They are stained by haematoxylin.
Collagen and cytoplasm are basic and therefore acidophilic. They are stained by Eosin
Name the 2 main types of epithelium
Covering epithelium
Glandular epithelium
Name, describe and give examples of simple covering epithelia
Squamous: thin, flattened cells e.g. in lung alveoli, thin cells are needed for rapid diffusion
Cuboidal: one layer thick, made of cube-like cells e.g. found in smalle excretory ducts, salvia is taken in by ducts
Columnar: involved in secretion of digestive enzymes and absorption of digested food e.g. found in the intestine
Name and describe stratified epithelia
Squamous:
– Kertanised e.g. found in skin
- Non-keratinised: flat cells but thick epithelium for high mechanical resitance/protection
e. g. found in roof of mouth, mouth dries out due to lack of keratin and therefore dehydration
- Non-keratinised: flat cells but thick epithelium for high mechanical resitance/protection
Name and describe the two types of pseudostratified epithelium
Pseudostratified – looks like many layers but isn’t
Ciliated: mutliple rows of nuclei e.g. in trachea where cilia hairs sweep mucus
Stereocilia: non-motile, cilia-like structure, 2 rows of nuclei e.g. in the epididymis (duct beind testes)
Describe and give an example of trasnitional epithelium
Can transition between thick and thin epithelium
e.g. urothelium in the urinary bladder: when the bladder is full, epithelium is thin, when the bladder is full, foldings make it thick
