Histology/Epithelium

Question 1

3 principles of cell theory

Answer 1

all living things composed of 1 or more cells, cells is the basic life unit, new cells arise from pre-existing cells

Question 2

describe the plasma membrane

Answer 2

physical barrier, sensitive to environment, gives support, selectively permeable, some have specialisations (cilia)

Question 3

name 3 cytoplasm components

Answer 3

cytosol (intracellular fluid), cytoskeleton (network protein filaments gives structure), organelles (ribosomes)

Question 4

define tissue and give 2 examples

Answer 4

tissue - groups of similar cells working together to carry out a common function
parenchyma - working tissue
stroma - scaffold and nutrition

Question 5

define organs

Answer 5

made up of several tissue types comprised in a morphologically recognisable structure to perform a specific set of functions

Question 6

name 2 components of tissue, describe one of the components and explain how cells are joined together in tissues

Answer 6

cells and extra cellular matrix, ECM is material between cells, joined at cell junctions

Question 7

define metastasis

Answer 7

the spread of a disease-producing agency from the primary disease site to other parts of the body

Question 8

describe the first 2 stages of histology tissue processing

Answer 8

fixation - freezing in liquid nitrogen or aldehyde based product to preserve the tissue
embedding - frozen sample in parrafin wax, provides support for tissue when sectioning

Question 9

describe the last 2 stages in tissue processing for histology

Answer 9

sectioning - thinner slice = higher resolution, use microtome to cut thin sections
staining - most cells are colourless and transparent, this colours the tissue

Question 10

describe H&E staining

Answer 10

haemotoxylin and eosin
H - basic, stains acidic (basophilic) structures purplish blue (nucleus)
E - acidic, stains basic (acidophilic) structures pink (cytoplasm)

Question 11

describe PAS staining

Answer 11

periodic-acid/schiff - for staining complex carbohydrates and glycogen
tissue stained with PAS is PAS+ (liver) and stains magenta
also stains mucus, basement membranes and brush borders in intestines

Question 12

name characteristic of epithelial tissue (8)

Answer 12

cells in close contact, cells are polarised and sit on basement membrane, not vascularised (nourished by CT), covers and protects surfaces in and out of cell, lines internal cavities (blood vessels/organs), forms glandular structures, forms barriers, combined with nervous tissue to make special senses (hearing/smell)

Question 13

name and explain the 2 types of epithelial tissue

Answer 13

covering epithelia - covers body surfaces, cavities, tubes
glandular epithelia - secretory epithelium arranged into glands, invaginations of epithelium, glandular organs (salivary)

Question 14

describe exocrine and endocrine glands

Answer 14

exocrine - retain continuity with surface and secrete via ducts
endocrine - lose contact with surface and secrete into bloodstream (thyroid)

Question 15

describe the layered names for epithelium

Answer 15

simple - one layer, good for absorption and secretion, fragile
stratified - 2 or more layers, good for protection
pseudostratified. one layer with mix of cell shapes

Question 16

name the 4 shapes of cells and 2 surface specialisations

Answer 16

squamous (flat), cuboidal (cube shaped), columnar (tall and cylindrical), transitional, readily changed (maybe due to stretching)
specialisations - cilia and keratin

Question 17

explain the structure, function and location of simple squamous epithelium

Answer 17

structure - single layer of flat hexagonal cells with flat nuclei
function - diffusion, filtration, secretion, friction protection
location - lines blood vessels and heart, alveoli, lines serous membrane of body cavities, lines kidney tubules

Question 18

shame the structure, function and location of simple cuboidal epithelium

Answer 18

structure - single cube shaped layer, some have microvilli (kidney tubules)
function - diffusion, secretion and absorption
location - kidney tubules, glands and ducts, lines terminal bronchioles in lungs and ovary surfaces

Question 19

explain the structure, function and location of simple columnar epithelium

Answer 19

structure - single layer of tall, narrow cells, some have cilia (bronchioles of lungs) or microvilli (intestines)
function - substance movement, secretion, absorption
location - glands and ducts, lung bronchioles, auditory tubes, uterine tubes, stomach, intestines, gallbladder, bile ducts, brain ventricles

Question 20

explain the structure, function and location of stratified squamous epithelium

Answer 20

structure - multiple layers of cells cube shaped on basal layer and flattened towards surface, can be non keratinised or keratinised
function - abrasion protection, infection barrier, reduced body water loss
location - keratinised: skin, non keratinised: mouth, throat, larynx, esophagus, anus, vagina, urethra, cornea

Question 21

explain the structure, function and location of pseudostratified epithelium

Answer 21

structure - single layer, nucleus at different levels, ciliated and associated with goblet cells (mucus secretors)
function - synthesise, secrete and move mucus containing foreign particles along the surface
location - nasal cavity lining, nasal sinuses, auditory tubes, pharynx, trachea, lung bronchi

Question 22

explain the structure, function and location of transitional epithelium

Answer 22

structure - cuboidal/columnar when not stretched, squamous when stretched, cell numbers per layer can also decrease
function - accommodate fluctuation of fluid level in organs/tubes, prevents against caustic (corrosive) effects of urine
location - lining bladder, ureters, superior urethra, pelvis of the kidney