HISTOLOGY

Question 1

list the tissue fixative and stain used in routine optical microscopy

Answer 1

fixative =
10% neutral buffer formalin [NBF]

stain =
hematoxylin and eosin [H&E]

Question 2

describe H&E staining

Answer 2

hematoxylin [basic dye]
stains acidic components like nucleic acids [found in nucleus] blue-purple colour

eosin [acidic dye]
stains basic components like proteins [cytoplasm] = pink/red

eg
RBCs = pink/red because they have no nuclei/RNA in cyotplasm
fibrous CT = pink
cell nuclei = blue

Question 3

list the FOUR basic tissue types

Answer 3

1. epithelial
2. connective
3. muscle
4. nervous

Question 4

list the THREE embryological germ layers and what they give rise to

Answer 4

1. endoderm
   * lining of uterus, vagina, blood vessels [endothelial cells], GI tract
2. mesoderm
   * muscle
   * soft/hard CT
   * bone/cartilage
   * blood cells
   * lymphoid tx
3. ectoderm
   * epidermis
   * most of oral mucosa
   * enamel
   * salivary glands

Question 4

describe epithelial tx and their 7 functions

Answer 4

• line all body cavities + hollow organs, cover all body sufaces
• are the major tx in glands

functions
1. protection [eg epidermis, oral mucosa]
2. secretrion [eg salivary glands]
3. absorption [eg GIT lining]
4. excretion [eg kidney]
5. filtration [eg kidney, liver]
6. contraction [eg myoepithelium]
7. sensory reception [neuroepithelium, taste buds, retina]

Question 5

describe glandular epithelium and 5 types

Answer 5

glandular epi. classified as either
1. endocrine [secretion directly to bloodstream]
2. exocrine [secretion via ducts into a surface]

1. salivary glands
   - exocrine
   - secrete saliva –> oral mucosal surface
   - func = lubrication, antibacterial
2. sweat glands
   - exocrine
   - skin skin they modulate body temp
3. sebaceous glands
   - exocrine
   - prod oily and protective secretion
4. thyroid gland
   - endocrine
   - prod thyroid hormone
5. adrenal gland
   - endocrine
   - prod cortisol, androgenic hormones, adrenaline

Question 6

describe the types of epithelial cells [3]

Answer 6

1. squamous epithelium
   - flat and scale like cells
   - found as epidermis, lining of mouth, esophagus, single cell layer lining BV + alveoli of lungs
   - form the outer later of statified squamous epithelia
2. cuboidal epithelium
   - cube shaped
   - found in glands + ducts
   - can be simple, stratified, pseudostratified
3. columnar epithelium
   - column shaped
   - can be further div into ciliated columnar and glandular columnar
   - can be simple, stratified, pseudostratified

Question 7

describe stratified squamous epithelium

Answer 7

forms
- epidermis
- oral mucosa epi
- esophageal epi
- other sites eg vagina, eye

varies in thickness

undergoes keratinisation
1. orthokeratin [nuclei ABSENT in nuclei of superficial keratinised layer]
2. parakeratin [nuclei PRESENT in nuclei of superficial keratinised layer]

Question 8

describe the basal lamina/basement membrane

Answer 8

assoc w all lining epithelia in addition to
- secretory units of glands eg alivary/kidney
- fat cells, skeletal muscle fibres, nerve tx
- outer capillary surface

forms 2D sheet under lining epithelial and envelopes structures eg glandsm muscle fibres, fat cells

main components
1. type IV collagen
2. laminin [GP]
3. glycoproteins
4. entactin [GP]
5. PGs eg perlecan
6. receptors [dystroglycans + integrins]

Question 8

outline the THREE types of intercellular epithelial junctions

Answer 8

1. tight junctions
   - permeability barrier
   - characterised by fusion [close approximation] of plas.mem
2. anchoring/adhering junctions
   - hemidesmosomes + desmosomes act as prickles bridging adjacent cells = strong intercellular binding]
   - provide mech support + stability
3. gap junctions
   - complex, tightly packed intercellular channels = comms between adjacent cells