Histology Flashcards
what are the 4 types of tissue found in the human body?
- epithelium
- connective
- nervous
- muscle
All epithelia are arranged as continuous sheets of tightly bound cells, what is the function of this?
- protection against microbial invasion
- regulation of movement of substances
How can the structure of epithelial tissues be described?
- continuous sheets of cells
- tightly bound together
- polarised
What shapes can epithelial cells be?
- squamous
- cuboidal
- columnar
What is the name of a single layer of epithelial cells?
simple epithelium
What name is given when there are two or more layers of epithelial cells?
stratified epithelium
What is the function of microvilli sometimes found on epithelial cells?
increase apical surface area
What is the function of cilia on epithelial cells?
movement of particulate matter
What is the function of a keratin layer on epithelial tissues?
strong protective apical layer
What epihelium is found in the oral cavity?
stratified squamous (protects against mechanical abrasion)
What can stratified squamous epithelium sometimes be that will enhance resistance to physical stress?
keratinised
How do epithelial cells become keratinised?
- accumulation of keratin filaments as they mature
- formation of tough, non-living surface layer
What is the proper term for a break in continuity of epithelium?
ulceration
What type of epithelium does a squamous cell carcinoma originate from?
stratified squamous epithelium
where does cell division take place within epithelial cells?
basal & suprabasal cells (basal layer)
What dense collagenous tissue supports the oral epithelium?
lamina propria
How does the lamina propria differ in the oral cavity in terms of location?
Highly mobile areas (eg soft palate & FOM)
- loose submucosal supporting tissue
Oral mucosa that overlies bone (eg hard palate)
- lamina propria is tightly bound to periostium
How do the cells of a malignant tumour present histologically?
- pleomorphism (variation in cell shape & size)
- numerous mitoses
- abnormal mitoses
- variable differentiation
What is the difference between LM (light microscopes) and EM (electron microscopes)?
Light microscopes = reveal basic cellular structure, resolution is 0.2microM
Electron microscopes = reveal ultrastructure, resolution is 1nm
What is the staining technique commonly used for histological practises?
H&E (haematoxylin & eosin)
- haematoxylin stains acidic structures blue/purple
- eosin stains basic structures red/pink
Histologically, what cells are seen in bone tissue?
- osteoblasts (synthesises & secretes bone tissue, gives rise to osteocytes)
- osteocytes (maintains mineralised bone tissue)
- osteroclasts (resorbs bone)
Describe the histological structure of skeletal muscle:
- individual muscle fibres separated by endomysium
- groups of muscle fibres grouped together in fasciculi
- each fasciculi surrounded by loose connective tissue (perimysium)
- entire muscle is externally surrounded by dense connective epimysium
- BV & nerves spread throughout these tissues
Name 2 classifications of neoplasia & their subgroups?
CLINICAL: benign / malignant
HISTOLOGICAL: epithelial / mesenchyme
How can histology help grade tumours?
Histological assessment of:
- invasion into underlying tissue
- degree of cellular atypia (mitotic activity, nuclear pleomorphism, differentiation, necrosis)
How does histology of a benign tumour present?
- resembles tissue of origin
- uniform cell/nuclear shape & size
- few mitoses
How does histology of a malignant tumour present?
- variable resemblance to tissue of origin
- cellular & nuclear pleomorphism
- many mitoses, abnormal
How does the mucosa of the cheek look histologically? (in reference to keratin)
NON-KERATINISED
How does the mucosa of the hard palate look histologically? (in reference to keratin)
KERATINISED (band along the top)
What do each of these arrows point to?
- Keratosis
- Acanthosis (hyperplasia of stratum spinosum)
- Elongated rete ridges (hyperplasia of basal cells)
What do these arrows point to?
Giant cells
What are the histological layers of epidermis?
- stratum coneum
- stratum granulosum
- stratum spinosum
- stratum basale
- dermis
What are the basic layers of mucous membranes histologically?
- epithelium
- lamina propria
What cells are found in the lamina propria?
- Fibroblasts
- Immune cells
What is found in the ECM of lamina propria?
- collagen
- elastin fibres
What are the gross types of oral mucosa?
- lining (buccal, soft palate)
- masticatory (hard palate)
- gustatory (tongue [specialised])
What are the functions of oral mucosa?
- Protection = barrier to microorganism
- Sensation = receptors that respond to touch, taste, pain etc
- Secretion = salivary glands
- Permeability & Absorption = feature utilised in drug delivery
How does a low-grade oral mucosa dysplasia present histologically?
- considerable amount of keratin production
- evidence of stratification
- well formed basal cell layer
- tumour islands are well defined & usually continuous with surface epithelium
How does a high-grade oral mucosa dysplasia present histologically?
- shows little resemblance to normal squamous epithelium
- considerable atypia
- invasion of surrounding tissues
- mitotic figures are prominent
