Veterinary Systems Exam 1

Why are stains used in histology?

To provide contrast

How does plane of section alter the 2D appearance of 3D structures?

It reduces 3D objects to thin, flat slices

What is histology?

The study of microscopic tissues and cells

What is stain in histology?

Dyes used to create contrast for tissue/cellular recognition

What is hematoxylin?

A plant dye combined with a metal ion to become a blue, positively charged (cationic) dye

What is eosin?

A fluorescent red dye derived from fluorescein (negatively charged)

What is H&E?

Hematoxylin and eosin stain

What is basophilic?

Loves base (binds to basic dyes)

What is eosinophilic?

Loves eosin (binds to eosin)

What is the purpose of staining?

Provide contrast to introduce color, shape, and texture cues

(T/F) Staining allows for visual pattern recognition

True

What are the chemical properties of hematoxylin stain?

Plant dye combined with a metal ion to become a blue positive charged (cationic) dye

What are the chemical properties of eosin stain?

A fluorescent red dye derived from fluorescein (negatively charged)

Hematoxylin is _______, while Eosin is _______

Cationic, Anionic

The combination of visual cues to recognize patterns and identify structures is a process within _________

histology

Why is it difficult for us to recognize structures on an unstained slide?

Little contrast makes it difficult to distinguish cellular and tissue structures

(T/F) Histologic stains bind differently to tissue components

True

Which two stains allow for the recognition of general tissue architecture?

Hematoxylin and eosin

Hematoxylin is ______ in color

blue

Eosin is _______ in color

pink

Hematoxylin binds to _______

acids

Eosin binds to _______

proteins

Which stain is dark blue in color, basic (cationic), binds to acidic/negative-charged structures, and often stains nucleic acids used to visualize the nucleus and ribosomes?

Hematoxylin

Which stain is basic and binds to acidic/negatively-charged strcutures?

Hematoxylin

Which stain is pink/red in color, acidic (anionic), binds to basic/positively-charged structures, and often stains cytoplasmic proteins/collagen/muscle fibers to visualize the cytoplasm and matrix?

Eosin

Nuclei, nucleoli, ribosome-rich cytoplasm, rough ER, and hyaline cartilage matrix are _________ structures

basophilic

Protein-rich cytoplasm, muscle fibers, collagen fibers, and red blood cells are _________ structures

Eosinophilic

DNA/chromatin, abundant rRNA, membrane-bound ribosomes, and sulfated GAGs and proteoglycans are _________ structures

basophilic

Abundant cytoplasmic proteins, actin and myosin, extracellular protiens, and hemoglobin are _________ structures

eosinophilic

(T/F) Tissue sections allow us to study microanatomy, but they have limitations

True

Routine light microscopy requires tissue to be cut into thin sections so that ______ can pass through

light

_________ converts a three-dimensional structure into a two-dimensional structure

Sectioning

The ______ of section describes the orientation of the cut

plane

The ______ of section describes where along the structure the cut is made

level

What is a longitudinal section?

Cut parallel to the long axis of the structure

What is a transverse section (cross-section)?

Cut perpendicular to the long axis

What is an oblique section?

Cut at an angle between longitudinal and cross sections

What is a tangential section?

Cut barely passes through the edge of a structure

The nucleus, nucleolus, chromatin, euchromatin, heterochromatin, RER, SER, Golgi apparatus, perinuclear halo, mitochondria, cytoskeleton, and secretory granules are...

major cellular structures visible in H&E sections

Which cellular structure is responsible for storing DNA and regulating gene expression?

Nucleus

Which cellular structure is responsible for producing rRNA and assembling ribosomes?

Nucleolus

Which cellular structure is responsible for synthesizing proteins from mRNA?

Ribosomes

Which cellular structure is responsible for synthesizing secreted and membrane proteins?

Rough endoplasmic reticulum (RER)

Which cellular structure is responsible for modifying, sorting, and packaging proteins?

Golgi apparatus

Which cellular structure is responsible for storing and releasing secreted products?

Secretory granules

Which cellular structure is responsible for controlling transport and cellular signaling?

Plasma membrane

Which cellular structure is responsible for synthesizing lipids, detoxification, and storing calcium?

Smooth endoplasmic reticulum (SER)

Which cellular structure is responsible for generating ATP through oxidative phosphorylation?

Mitochondria

Which cellular structure is responsible for maintaining the shape and enabling cellular movement?

Cytoskeleton

Which cellular structure is responsible for digesting and recycling cellular materials?

Lysosomes

Which cellular structure is responsible for storing lipids for energy?

Lipid droplet

What are 4 basophilic structures in H&E?

Nucleus, nucleolus, high concentrations of ribosomes (RER), and secretory granules

Which cellular structure is usually the most prominent basophilic structure in H&E sections?

Nuceli

Nuclei can be described by their ________ pattern

chromatin

Which chromatin type is described as dispersed chromatin and appears to have lighter staining?

Euchromatin

Which chromatin type is described as condensed chromatin and appears to have darker staining?

Heterochromatin

(T/F) Most nuclei will rarely contain both euchromatin and heterochromatin

False (most nuclei WILL contain both euchromatin and heterochromatin)

Chromatin patter often reflects _________ activity

transcriptional

Which chromatin type is generally accessible and transcriptionally active?

Euchromatin

Which chromatin type is generally condensed and transcriptionally inactive?

Heterochromatin

What are 4 eosinophilic structures in H&E?

Mitochondria, cytoskeleton, ECM proteins (collagen & elastin), many secretory granules, and most proteins

Lipid droplets, golgi, glycogen, mucus, and the plasma membrane are _____ stained structures in the H&E

poorly

Why are lipid droplets poorly stained structures?

They are extracted during routine paraffin processing

Why are Golgi poorly stained structures?

They are mostly membrane and hydrophobic

Why does glycogen have poor staining properties?

It is often extracted or poorly visualized

Why does mucus have poor staining properties?

Often pale or poorly preserved (acidic mucins may be basophilic)

Why does the plasma membrane have poor staining properties?

It is too thin to resolve directly

How might fixation create histologic artifacts?

May pull cells and extracellular matrix away from one another, creating artificial clear/white spaces

How might processing create histologic artifacts?

Processing may extract material, creating blank/white gaps

How might sectioning create histologic artifacts?

Sectioning may create tears, folds, or knife/chatter marks, which alter the physical composition of tissues on slides

How might staining create histologic artifacts?

Unfiltered stain or acid-formalin reacting with blood may leave crystaline, black/brown, or deep purple granular debris on tissue sections

How might mounting steps create histologic artifacts?

Tears, folds, chatter/knife marks, shrinkage, precipitates, and dissolution/extraction are examples of common _________

artifacts

Thin tissue sections are prone to _________ during cutting or placement on the slide

tearing

Thin tissue sections are prone to _______ over during placement on the slide, causing a lack of uniformity and an uneven appearance

folding

Which artifact type is caused by microtome blade vibration, causing fine, parallel thick-and-thin bands across tissue?

Chatter marks

Which artifact type is caused by dull or knicked blades, leaving straight vertical scratches?

Knife marks

Fixation and dehydration pulls cells and the extracellular matrix away from one another, creating artifical clear or white artifacts/spaces, otherwise known as _________

shrinkage

Which artifact type is defined by an unfiltered stain or acid-formalin reacting with blood, leaving crystalline, brown/black, or deep purple granular debris resting on the tissue section?

Precipitates

Which artifact type is defined by fats and poorly fixed structures that are prone to dissolving or washing off the slide?

Dissolution/extraction

(T/F) When staining, real structures often follow predictable patterns

True

________ appear irregular or out of place and may cause hypo/hyper-staining

Artifacts

What is connective tissue?

One of the four primary tissue types

What are the functions of connective tissue?

Supports, connects, protects, stores, transports, and participates in tissue repair and defense

What is the difference between the stroma and parenchyma?

The stroma is the structural framework of an organ, and the parenchyma is the functional component of an organ

How many primary tissue types are there?

4

The connective tissue forms the _____ and supporting framework of most organs

stroma

Bone, adipose tissue, cartilage, and blood are specialized __________ tissues

connective tissues

What two components make up connective tissues?

Cells + Extracellular Matrix (ECM)

What two components make up the Extracellular Matrix (ECM)?

Fibers + Ground Substance

What are fibers?

Filamentous structural proteins that provide strength

Collagen, reticular fibers, and elastic fibers are examples of ______

fibers

What is ground substance?

Gelatinous material

Tissue fluid, glycosaminoglycans, proteoglycans, and adhesion proteins are examples of ________

ground substance

Which connective tissue component is responsible for ECM synthesis, remodeling, repair, immune surveillance/defense, energy storage, and insulation?

Cells

Which connective tissue component is responsible for providing strength, resistance, a supportive framework, stretch, and recoil?

Fibers

Which connective tissue component is responsible for binding water, maintaining hydration, resisting compressive forces, regulating diffusion of wastes/nutrients, and supporting cell adhesion/migration/signaling?

Ground substance

How can we differentiate loose and dense connective tissues?

Cellularity, fiber density, ground substance abundance, and mechanical properties

What are the 3 types of connective tissues?

Connective tissue proper, specialized connective tissue, and embryonic connective tissue

What is the most common connective tissue type?

Connective tissue proper