Histology                                                                                                                     Stanley Shostak
BioSc 1450                                                                                                                  Spring 05

Lecture 1. Cells and Extracellular Material: Components of Tissues

My job is to teach you to think histologically, to second guess tissue activities from stained sections. Histology relies heavily on two primary staining reactions to characterize about 200 different cell types in six primary tissues and all their variations: basophilia (hematoxylin; generally blue-black) versus acidophilia (eosin [eosinophilia]; generally pink-red). If you keep in mind that tissues are made of and by cells and their products, then you should be able to use the basophilia and acidophilia seen in sections to interpret what cells and tissues are doing. Of course, you will also have to keep in mind everything else you know about cells (from cell division to protein synthesis). That is thinking histologically!

Plasma membrane (plasmalemma): phospholipid bilayer with peripheral proteins and embedded integral proteins and cholesterol; functions in cell-cell recognition, exocytosis (constituted pathway [non-clathrin coat] and regulated pathway [clathrin coat])and endocytosis (pinocytosis and phagocytosis)

fluid mosaic theory

receptors for signaling molecules; initiators and controllers of secondary messengers; receptor-mediated endocytosis (clathrin-coated endocytic vesicles); CURL (compartment for uncoupling receptors and ligands) early endosome

transport channels: passive: down simple diffusion or facilitated diffusion gradient; active: against concentration gradient; ion channels: gated (stimulus opens [ligands; neurotransmitter substance]) or ungated (always open);


gap: connexins (communicating)
macular densa (adherens)
zonula (zonula; zonulae) adherens; fassciae adherentes
zonula (zonula; zonulae) occludens (tight)
Organelles (suspended in cytosol) mitochondria: the mighty mites; generate ATP; synthesis lipids and some of their own proteins; contain DNA and ribosomes. membranous endoplasmic reticulum (ER [composed of tubules, sac {cisternae}; functions in synthesis and modification of proteins]); rough (rER [cytosolic surface with receptors for ribosomes and docking proteins (for signal recognition particles [SRPs]); cisternal surface functions in packaging proteins and lipid for export) and smooth (sER functions in synthesis of cholesterol and lipids and detoxification); integral membrane proteins (e.g., ribophorin I and II) may form transport channels; signal peptidase cleaves signal protein from polypeptide chain entering rER.

endosomes: function in destruction of endocytosed, phagocytosed and autophagocytosed material > endolysosomes > formation lysosomes. Membranes contain proton pumps acidifying contents; later endosomes: probably fuse with early endosome forming multivesicular body (type of lysosome)

lysosomes: vesicles containing hydrolytic enzymes functioning in intracellular digestion (phagolysosomes; autophagolysosomes) > residual bodies.

lysosomal enzymes and disease:
Gaucher's: spleenomegaly
Gout: urate crystals precipitate from saturated plasma in synovial cavities
Pompe's disease: hepatomegaly; absence of a -glucosidase > excessive storage glycogen
Tay Sachs

peroxisomes: vesicles containing oxidative enzymes and catalase (degrades hydrogen peroxide); function in formation of free radicals and hydrogen peroxide capable of destroying substances; function in detoxification and elongation of some fatty acids; formed by fission from preexisting peroxisomes.


golgi apparatus and trans-golgi network: flattened cisternae; cis- (forming), medial, and trans-(maturing) surface; function in modification and packaging of macromolecules directed outward.

forming surface: fuses with non-clathrin-coated transfer (transport) vesicles

maturing surface: sorting and packaging into trans-Golgi network; gives rise to secretory vesicles.

Cytosol: site of protein synthesis; instrumental in changes of cell shape; site of cascades and movement of intracellular receptors, secondary messengers, and signals. lipid droplets:

ribosomes: bipartite complex of ribosomal RNA (rRNA) and protein; functions in protein synthesis (translation).

Glycolysis and storage of glycogen

Chemical messengers: cytokines
(also note chemical messengers between cells: mediators: humoral factors; chemical factors in body as whole: hormones)

inclusions: pigments, lipofuscin

Filamentous cytoskeleton microfilaments: thin 5 nm actin subtypes actin: terminal web

dynamical structural framework: linking protein = predominantly filamin = cell cortex

intermediate filaments: 10-12 nm tonofibrils: cytokeratin: epidermis (several blistering diseases associated with mutant types)
vimentin: in mesodermal derivatives
desmin: muscle
neurofilament protein: nerve

microtubules: a & b tubulin [protofilaments]: 13 in cycle; 25 nm interpolar & kinetochor or chromosome microtubules
MOC (microtubular organizing center)
basal body & centriole: pinwheel (9 triplets)
axoneme of cilia & flagella: (generally) 9 (doublets) + 2 (singlets)

microtubule [motor] associated protein: dynein: moves along tubule toward nucleus; kinesin: moves along microtubule away from nucleus
Nucleus: envelope (inner and outer membranes enclosing perinuclear cisternal space) penetrated by nuclear pore complex; outer nuclear membrane continuous with rER and dotted with ribosomes; nucleolus: site of rRNA synthesis and assembly of ribosomal subunits; chromosomes: condensed DNA/protein in mitotic nucleus and during mitosis; location of nuclear genes; chromatin: dispersed DNA/protein in interphase nucleus. Mitotic Figures: chromosomes during any phase of mitosis but typically metaphase or anaphase (except in eggs where prophase of meiosis I is prolonged).

Interphase: nucleus of cell between divisions or following divisions; includes

G1 and sometimes G0: interval after mitosis and before DNA synthesis
S: interval of DNA synthesis
G2: interval after DNA synthesis and before mitosis

Programmed cell death (PCD)

cells break down as a group without macrophages
Apoptotic figures: frequently accompanied by macrophages
karyorrhexis > karyolysis
pycnotic figures

Cellular dimensions: mammalian red blood cell (typically 6-7 mm in diameter) used to estimate dimensions of other cells in a section.

Nuclear staining: vesicular; salt-pepper; dense

Heterochromatin: dense basophilic stained areas in nucleus

Euchromatin: pale basophilic stained nuclear staining; usually accompanied by nucleolus indicative of nuclear gene expression and cytoplasmic protein synthesis

Feulgen reaction: HCl hydrolysis (aldehyde in DNA; hydroxyl in RNA) + leucofuschin

Histochemical techniques cellular chemistry (precipitate; pigment; fluorescence; autoradiography) PAS (periodic acid hydrolysis + Schiff reagent: carbohydrate vs. Glycosamino glycan [GAG]; glycogen + salivary gland amylase digestion) + counterstaining
Enzyme histochemistry: e.g., phosphatases
Immunohistochemistry: immunoperoxidase
in situ hybridization: nucleic acid probe
Staining Basic dyes and Basophilia h(a)ematoxylin
Cresyl violet
Acridine orange (fluorescence)
Azan method: red basophilic dye (blue-green acidophilic dye)
Acid dyes and Acidophilia Eosinophilia supravital staining: brilliant cresyl blue on fresh blood > reticular precipitate (rRNA) metachromasia: e.g., staining basophilic granules with toludine blue
Tissue preparation & artifacts



embedding paraffin and plastic

Sectioning microtomy; utilizes microtome (device for advancing specimen or knife in measured quantities); thin and thick plastic sections (thinner than paraffin sections); cytological sections thinner than histological sections (typically 10 micro m).

Whole mounts; spreads; smears

Frozen sections

Electron microscopy: transmission and scanning

Tissue types: Cells and Extracellular material

adhesive materials between cells
CAMs: cellular adhesive materials (bind plasmalemmas directly to plasmalemmas)
JAMs: junctional adhesive materials (adhesive between juxtaposed plasmalemmas)
SAMs: substrate adhesive materials (bind plasmalemmas to extracellular [substrate] material

Standard vocabulary for tissues: cells and extracellular material
Virchow: 4: epithelia; connective; muscle; nervous textbook: 5: epithelia; connective and adipose tissue; blood; muscle & nervous Shostak: 6: epithelia; connective; muscle; nervous; blood & germ line. Other ways of identifying tissue types Parenchyma & stroma (functional specialized cells & less specialized supporting cells)
layers; tunica; strata; lamina
mucosa; submucosa; muscularis; adventitia; serosa
corext; medulla
endo-; peri-; epi- (followed by name of organ or organ system [e.g.,
-metrium; -neurium; -mysium)
Patterns of division facultative divider; constitutive divider
endomitosis; prolonged G2 (in liver)
Types of tissues (dynamics) Stationary
Satellit (adult stem cells)
Epithelia: cells broadly in contact with each other; minimal extracellular material; polarized; basal lamella (basement membrane); associated with surfaces or glands (i.e., secretory)
Polarity: Cell orientation: apical (luminal) versus basal; lateral surfaces.
striated border: infolding + mitochondria; typically Na+ pumps
specialized intercellular junctions (desmosomes [cadherins]; hemidesmosomes [integrins: receptors for laminin and collagen type IV]; junctional complexes (JAM); zona [fascia] occludens = tight junctions; zona adherens; macular densa [adherens]); gap [communicating] junctions

specialized apical cell surfaces: microvilli; stereo(villi)cilia; cilia and flagella; terminal web; terminal bar
Connective Tissue: maximum extracellular material; minimal cell contact; packing; between blood vessels and other tissues; skeletal; gap junctions in bone 

Blood and lymphatic: circulating cells (red and white blood; NK, B and T-type lymphocytes) suspended in plasma

Muscle: contractile tissue;

skeletal: striated; syncytium; stretch receptors; satellite (stem) cells
cardiac: striated; uninuclear (occassionally binuclear); gap junctions, fassciae adherentes and macular adherentes (desmosomes); conductile fibers
smooth muscle: generally in sheets or chords (uterus); dense bodies; gap junctions; calmodulin )calcium binding protein); desmin (skeletin) major intermediate filament; viemntin; visceral smooth muscle: spontaneous activity; peristaltic or rhymic contraction; multiunit smooth muscle (iris): highly innervated; derived from neural crest.

Nervous: conductile tissue; neurons: synaptic vesicles; synapitc junctions; glial cells; neurolemmocytes; myeline sheath; sensory organs

last revised Jan. 4, 2005