Histology Prelab - Cell Staining and Organelles

Dark stained areas of the nucleus

Heterochromatin

Appears dark blue/purple when stained with hematoxylin (inactive cell - not transcriptionally active)

Heterochormatic Nucleus

Light stained areas of the nucleus

Euchromatin

Appears pale and exhibits a light blue/purple stain (active cell - transcriptionally active)

Euchromatic Nucleus

Labile, Stable, and Static

Classifications of stem cells

-Rapid renewal

-Short life-span (days-weeks)

-Regular mitotic activity

-Most susceptible to cytotoxic drugs

-epithelium, WBC & RBC

Labile stem cells

-Occasional renewal

-Viable for years

-Rare to see mitotic cells visible in most of the tissue

-Progenitor cells can be induced by external stimuli or damage

-bone, CT, liver, pancreas, smooth muscle, epithelium of kidney, and alveolar cells in lung

Stable Stem cells

-Rarely renew

-Long life span of tissue

limited source of stem cells

-tissue typically not replaced by stem cell when damaged

-neurons, cardiac, skeletal muscles

Static stem cells

Accidental cell death

-Irregular chromatin condensing, mitochondria swells, and breakdown of membrane and ribosomes

-Induces Inflammatory Reaction

Necrosis

Programmed Cell Death

-Nucleus and Cytoplasm break into fragments called apoptotic bodies

-No inflammation

Apoptosis

Site of transcription

Chromosomes (DNA) contain genetic information to encode all proteins in the body

Nucleus Function

Membrane-bound structure containing chromatin that can appear dispersed or tightly coiled (DNA and nuclear proteins)

Nucleus Description

-Heterochromatin (tightly coiled condensed chromatin) exhibits intense basophilia

-Euchromatin (extended and dispersed chromatin)

Nucleus Histological Appearance

Site of Ribosomal RNA Synthesis and ribosome assembly

Nucleolus Function

Dense non-membrane bound structure in the nucleus appearing as small circle in nucleus

Nucleolus Description

Appears basophilic by light microscopy due to high concentration of heterochromatin

Nucleolus Histological Appearance

(Nuclear envelope)

Mediates bi-directional and selective transport of molecules between nucleus and cytoplasm

Nuclear Membrane Function

Surrounds the nucleus, contains nuclear pore complexes (openings)

Nuclear Membrane Description

Visible in light microscopy, easiest to see in euchromatic nucleus (breaks down during mitosis)

Nuclear membrane histological appearance

-Divides cell from external environment

-Mediates Cellular Interactions/signaling with ext. environment

-Site of membrane transport via channels and receptor activation

-Semi permeable and selective barrier

Cell plasma membrane Function

lipid bilayer containing intrinsic proteins and external coat of complex carbohydrates known as the glycocalyx

Cell plasma membrane description

-Visible to light microscopy when stained (glycocalyx stained due to abundance of complex carbohydrates)

-Stains best with PAS

Plasma membrane histological appearance

Surface: site of protein synthesis

Lumen: site of post-translational modifications and folding of proteins synthesized by attached ribosomes

Rough Endoplasmic Reticulum Function

Extensive membrane system with ribosomes on surface

rER Description

-Appears as basophilic clumps in cytoplasm

-Cells with abundant rER reflects high amounts of protein synthesis

rER Histological appearance

(NB) term used to describe large amounts of rER in a nerve cell

Nissl bodies

POWERHOUSE OF THE CELL (site of ATP synthesis via 3 metabolic pathways)

Mitochondria Function

Double membrane bound organelle with folded inner membrane forming Cristae

Mitochondrial matrix contains DNA and enzymes

Mitochondria description

Stains pink (acidophilic) with H&E

Eosin preferentially binds to positively charged components (membrane proteins)

-High amounts of mitochondria in a cell may indicate active transport or a high demand for aerobic activity

Mitochondria Histological Appearance

contains enzymes synthesized in rER and function in:

-lipid metabolism

-steroid hormone synthesis

-Glycogen breakdown & detoxification

Smooth Endoplasmic Reticulum Function

Extensive membrane system without ribosomes

sER description

may appear vacuolated in H&E staining in stains involved in active lipid metabolism and steroid synthesis, otherwise indistinguishable

sER Histological appearance

-Site of post-translational modification of proteins

-Responsible for packaging and sorting of proteins

Golgi Function

Stacks of flattened membrane-bound cristernae

Golgi description

Flattened membrane vesicles in golgi and ER

Cristernae

Site of destruction of pathogenic organisms or degradation of intracellular waste products via acid hydrolase enzymes

Lysosome function

Membrane bound vesicle containing hydrolytic enzymes

Lysosome Description

Not visible by H&E

May be stained for specific proteins by immunohistochemistry or visible in EM

Lysosome Histological Appearance

Visible microscopy vs electron microscopy

VM vs EM

Site of beta-oxidation of long-chain fatty acids and control amount of hydrogen peroxide via catalase activity

Peroxisome Function

Membrane bound vesicle containing catalases and oxidative enzymes for detoxification

Peroxisome Description

Not visible by H&E

May be stained for specific proteins by immunohistochemistry or visible in EM

Peroxisome histological appearance

Energy storage

Glycogen Granules function

Non-membrane bound granules

Glycogen Granules description

By H&E, cytoplasm appears foamy with regions of acidophilia. Glycogen that accumulates is unstained (best stained with PAS)

Glycogen Granules Histological appearance

None

Lipofuscin Granules Function

Membrane bound accumulated waste of lysosomes

Lipofuscin granules Description

Appears as gold to brown accumulation in cytoplasm best-seen in non-dividing cells

Lipofuscin granules histological appearance

Energy storage

Lipid droplets (triglycerides) function

Non-membrane bound aggregates of lipid (Adipose contains aggregation)

Lipid Droplets description

Transport materials between different cell compartments and to plasma membrane for export

Secretory epithelial cells may produce and store mucus or proteins

Transport/Secretory Vesicle function

Membrane bound vesicles

Transport/Secretory vesicles Description

only observed if large and stain can depend on contents (mucus=light stained and enzymes=bright pink)

Transport/Secretory Vesicles Histological Appearance

Secrete Mucus from stored mucin granules

Goblet Cells

1. Look at staining characteristics

2. General Organization: Ordered or scattered (how many layers if ordered)

3. Appearance of cell

-shape of cell/nucleus

-staining pattern

-prominence/position or organelles

4. Variation of cells (hypertrophy or atrophy)

5. Density of cells (hyperplasia)

6. # of nuclei

Suggested Analysis Steps

Increase in cell size

Hypertrophy

Decrease in cell size

Atrophy

Increase in proliferation (increase in cell number)

Hyperplasia

More than one nucleus per cell

Multinucleated

Used to stain complex carbohydrates magenta

(glycogen, mucin, extracellular material containing carbohydrates (i.e. glycoproteins and glycolipds)

Periodic Acid-Schiff

Most common staining method

Hematoxylin (basic dye, stains purple) and Eosin (acidic dye, stains pink)

Hematoxylin and Eosin

Stains RBC orange and WBC cytoplasm blue

Wright-Giemsa Stain

Stains connective tissue (collagen = blue, nuclei = red, cytoplasm = pink)

Mallory-trichome

Stains elastic fibers black/purple (Elastic fibers, reticular fibers, nervous tissue)

Silver Stain