Veterinary Systems Unit 1

Why do we stain tissue?

To add color, contrast, and differentiation

Hematoxylin

plant dye combined with metal ion to become a blue cationic dye

Eosin

A fluorescent anionic red dye derived from fluorescein

What does hematoxylin stain?

nucleic acids, nuclei, nucleoli, ribosome-rich cytoplasm, rough ER, and hyaline cartilage matrix

what does eosin stain?

mitochondria, cytoskeleton, extracellular protein matrix proteins (collagen and elastin), many secretory granules, protein-rich cytoplasm, muscle fibers, and red blood cells

basophilic

loves base, binds to hematoxylin

eosinophilic

loves eosin

plane of section

orientation of cut

level of section

where along the structure the cut is made

what we see in a microscope depends on

3d organization, stain used, and plane and level of section

sectioning makes a 3d image

into a 2d image

1. longitudinal section 2. transverse sections 3. oblique section

longitudinal section

cut parallel to long axis of structure

transverse/cross section

cut perpendicular to long axis of structure

oblique section

cut at an angle between longitudinal and transverse sections

tangential section

cut barely passes through structure

nucleus

stores DNA and regulates gene expression

nucleolus

produces rrna and assembles ribosomes

ribosomes

synthesize proteins from mrna

rough endoplasmic reticulum (RER)

synthesizes and secretes membrane proteins

golgi apparatus

modifies, sorts, and packages proteins

secretory granules

store and release secreted products

plasma membrane

controls transport and cellular signaling

smooth endoplasmic reticulum (SER)

synthesizes lipids, detoxifies, and stores calcium

mitochondria

generate ATP through oxidative phosphorylation

cytoskeleton

maintains shape and enables cellular movement

lysosomes

digest and recycle cellular materials

lipid droplet

stores lipids for energy

why are some secretory granules basophilic?

they contain acidic anionic glycoproteins

euchromatin

being used, so more dispersed and lighter staining

heterochromatin

not being used, so more condensed and darker staining

poorly stained H&E structures

lipid droplets, golgi, glycogen, mucus, plasma membrane

why are lipid droplets and golgi not stained well?

hydrophobic and H&E are water based dyes

why are glycogen and mucus not well stained?

poorly preserved

why is plasma membrane poorly stained?

too thin to see