ToB S1 - Microscopy and Epithelial Tissue Flashcards
Define tissue
Collection of cells specialised to perform a particular function
How many times bigger is a millimetre than a nanometre?
1,000,000 times larger
Define histology
Study of the structure of tissues by means of special staining techniques coupled with light and electron microscopy
Name the six common types of biopsy and a tissue that would be sampled from each?
Curettage - scooping/scraping Eg endometrium of the uterus Smear
Mechanical exfoliation Eg cervix, buccal cavity
Direct incision - cutting and removal Eg skin
Needle - Eg breast, brain, kidney muscle
Endoscope - e.g lung, colon
Transvascular - Eg heart and liver
Define biopsy
Removal of a small piece of tissue from an organ or part of the body for microscopic investigation
Name two common fixatives
1) Glutaraldehyde
2) Formaldehyde
Why is tissue fixed?
- Prevent autolysis and putrefaction
- Maintains cross-linked macromolecules
Outline the process of fixation
- Tissue dehydrated with ethanol
- Cleared with xylene
- Embedded in wax
- Sectioned
- Rehydrated (xylene-ethanol-water)
- Stained
- Dehydrated again (water-ethanol-xylene)
- Mount specimen on slide
What is Periodic acid–Schiff used to stain?
Carbohydrates and glycoproteins (magenta)
What cell component would haemotoxylin stain?
Acidic cell components; Nucleolus - RNA, Chromatin - DNA
What colour does eosin stain?
Pink
What are the four types of light microscopy?
1) Confocal - scanning one or more focused beams, labelled with fluorescent probes, can eliminate ‘out of focus flare’, enable formation of 3D images
2) Phase contrast - uses interference effects produced when two sets of waves combine, enhances image of living, unstained cells
3) Darkfield - light from side is scattered, only refracted light seen
4) Fluorescence - Uses antibodies coupled to fluorescent stain
What is the average diameter of a typical human cell?
10-20 micrometres
How are shrinkage artefacts produced?
The rehydration and dehydration process leaving abnormalities on the final slide
What does Eosin stain?
Basic components of a cell Eg most cytoplasmic proteins and extracellular fibres pink
What colour does haemotoxylin stain?
Blue/purple
Define epithelia
Sheets of contiguous cells, of varied embryonic origin that cover the external surface of the body and line the internal surfaces
Define mucous membrane
An interior surface that opens to the exterior Eg GI tract, respiratory tract, genitourinary
Define serous membrane
An interior surface that does not open out Eg pericardial sac, pleural sac, peritoneum, blood vessels, lymph vessels
Name 3 locations of squamous epithelium
Any from: lining of blood and lymph vessels, lining of body cavities (pericardium, pleura peritoneum), pulmonary alveolar epithelium, loop of Henle, Bowman’s capsule, inner and middle ear
Name 3 locations of cuboidal epithelium
Any from: thyroid follicles, small ducts of many exocrine glands, kidney tubules, surface of ovary
Name 3 locations of columnar epithelium
Any from: Stomach lining, gastric glands, small intestine and colon, gallbladder, large ducts of some exocrine glands, oviducts, uterus
Name 3 locations of pseudostratified epithelium
Any from: Lining of the nasal cavity, trachea and bronchi, epididymus, ductus deferens, auditory tube, lacrimal sac and large excretory ducts
Name locations of transitional epithelium
- Ureters, bladder, urethra, renal calyces
What is the function of the basement membrane?
Serves as a strong flexible layer to which epithelial cells adhere. It also serves as a molecular and cellular filter
Explain the reason for the different rates of renewal of each type of epithelium
- turnover rates depend on cell function and location - Epidermis of skin - 28 days
- Small intestine epithelia are replaced every 4-6 days (from the base of the crypts)
- Some epithelia aren’t renewed but proliferation can be triggered to replace damaged/lost cells
What are microvilli?
Apical extensions that greatly the surface area for selective absorption of intestinal contents
What are sterocilia?
Very long microvilli, extends from the surface of the ducts deferens and the epididymis. They may also have an absorptive function
What are cilia?
Extension from cells that beat in coordinated waves. Found in the lining of the trachea where they sweep mucus and dirt out of the lungs. Also found in the fallopian tubes, where they move the oven from the ovary to the uterus. Axoneme, 9+2 configuration
