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);
junctions
desmosomes
gap: connexins (communicating)
hemidesmosomes
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
Fabry's
Nieman-Pick
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.
hydrogenosomes
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)
Autophagia: cells break down as a group
without macrophages
Apoptotic
figures: frequently accompanied
by macrophages
karyorrhexis >
karyolysis
pycnotic figures
cytolysis
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)
Giemsa
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
Fixation
dehydration
infiltration
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
Expanding
Proliferative/Differentiating
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