A presentation summarising the key features of the main tissues for 1st year medical school histology.

1. Histology
1st year medical school
Cambridge University
by Christiane Riedinger
2011

2. Aim of this presentation
When starting to learn histology, I was looking for simple
overviews presenting the key features of each tissue type
or tissue found in the body.
Since I could not find that anywhere, I made it myself!
This presentation should be used with a standard
histology textbook (or the internet ;-)) showing you
slides/pictures of the structures described here.
Pictures of particular stains (part I) have been cited.
C.Riedinger

3. Contents
1. staining and fixing techniques
2. histological properties of human tissue types
2.1. connective tissue
2.2. muscle tissue
2.3. nervous tissue
2.4. epithelial tissue
3. histological properties of anatomical structures
4. ways to identify tissues/cells
• blood cells (connective tissue)
• ganglia (nervous tissue)
• components of the urinary system
C.Riedinger • tissue types of the GI tract

4. 1. staining and fixing techniques
C.Riedinger

5. 1. staining and fixing techniques (2)
C.Riedinger

6. 1. staining and fixing techniques (3)
C.Riedinger

7. 1. staining and fixing techniques (4)
C.Riedinger

8. 2. tissue types: connective tissue
Overview of tissue types: C.Riedinger
tissue layers/comp
function cell types appearance stains
type onents
- binds - fibroblasts - collagen types: - masson's trichrome
functional cell (excrete ECM), mostly I, II in 1. Loose (10-20% C) (collagen) -
groupings come from cartilage, II in 2. Dense (40-50% C, van gieson (collagen)
together mesoderm skin, vessels, IV in tendons 90%) - elastin stain (elastin)
- regulation - adipocytes epithelium of 3. elastic - eosin (collagen, but not
- chondroblasts basement lung, skin, bladder, specific)
- myofibroblasts membranes vessels, - silver stain (reticulin)
- immune cells: - elastic fibres change with age
macrophages, (stain poorly) 4. cartilage
histiocytes, mast - ground 70% ground
cells, white blood substance substance
cells (= gel embedding 5. bone
collagen and = cartilage with 70%
elastin) salts
connec- 6. fat
tive white or brown
7. blood
(mesoderm)
C.Riedinger

9. 2. tissue types: muscle tissue
Overview of tissue types: C.Riedinger
tissue layers/comp
function cell types appearance stains
type onents
- no striations, spindles
- masson's trichrome:
- 1 elongated centrally
located nucleus (muscle, connective
- irregularly branching tissue)
fasciculi, can have ganglia
- shorter, often layered
- unicellular: - fasciculi aren't in parallel
- surrounded by
myoepithelial cells - no myofibrils
lamina
(secretory glands), - caveolae
- attached via link - gap junctions
pericytes (like
proteins
smooth muscle,
- endomysium: - intermediate
surrounds blood - appears striated
supp. tissue around
vessels, called - 1-2 central nuclei
each individual
multiunit smooth - intracellular boundaries hard
muscle fibre to see
- contraction muscle as each unit
muscular functions
- perimysium: - cells appear continuous
(funct. Syncytium)
(embryologically a surrounds each
individually), - branched ends
subtype of muscle cell bundle
myofibroblasts - long, cylindrical
connective from = fascicle - rich capillary network
(contractile and
mesoderm) - epimysium: - intercalated discs (Z)
collagen, scarring)
around groups of - gap junctions
- no end plates, tendons!
fasciculi, dense
- multicellular: - diad (SR + T)
collagenous sheeth
smooth (lots of
around whole
cells function as - extremely elongated
muscle
single unit), - multinucleate (in
transverse section may not
cardiac, skeletal
be seen)
- nucleus at periphery
- striated
- parallel fasciculi
- triad = SR terminal
cisterna + T-tubule
C.Riedinger

10. 2. tissue types: muscle tissue (2)
C.Riedinger
striated:
light: I-band containing Z-line (made of actin fibres)
dark: A-band containing myosin fibres
H-band: myosin-only region in A-band
M-line: middle of A-band
T-tubules:
T-tubules are at level of Z-bands (cardiac, amphibian skeletal)
T-tubule at junction of A and I bands (skeletal)
Red skeletal muscle: (aerobic, stains more strongly)
rich in myoglobin, numeruous mitochondria, many capillaries
White skeletal muscle: (anaerobic, stain is more pale)
less myoglobin, fewer mitochondria, poorer blood supply
cardiac: junctions!
intercalated discs: black line perpendicular to length of fibre, parallelt o striations
membrane-to-membrane contact in intercalated discs (only visible at EM resultion):
1. Fascia adherens: intermediate junction, anchors actin at terminal sarcomeres - mechanical connection
2. desmosomes: (macular adherens), attachment of intermediate filaments to cytoskeleton - mechanical
3. Gap junctions: (nexus), exchange/transmission of ions and small molecules from cell to cell - electrical
result: functional syncytium!
purkjinje fibres: pacemaker cells, larger than cardiac muscle cells and sometimes binucleated
contain lots of mitochondria but less myofibrils (irregular), no T-tubules and intercalated discs
still have desmosomes and gap junctions, lots of glycogen (can stain for it specificlally!)
smooth:
dense bodies/plaques: points of attachment for actin filaments
caveolae: invaginations of the plasma membrane, help Ca2+ entry
macula - spot (latin)
C.Riedinger

11. 2. tissue types: nervous tissue
Overview of tissue types: C.Riedinger
tissue layers/comp
function cell types appearance stains
type onents
- electrically - neurons transverse: - large cell body - Nissl methylene blue
conduct signals (multipolar, - bundles of axons (rER)
bipolar, = fasciculi - large, round,
pseudounipolar) prominent but pale - Sudan black (for LM)
- glial cells - endoneurium = staining nucleus, and osmium (for EM)
(schwann cells, around each nerve dispersed chromatin (myelin and lipids,
oligodendrocyte, fibre along with connective dissue)
astrocytes, myelin - extensive basophilic
satellite cells) cytoplasm
- fibrocytes - perineurium =
dense conn. tiss - large and central
around bundles of nucleolus
nerve fibres = (transcriptional
fascicles activity)
nervous - epineurium = - in longitudinal
(from ectoderm?) loose conn. tiss section of nerve
around fascicles trunks: zig-zaggy
lines with round nuclei
Longitudinal: (of schwann cells!!!!)
dendride, nodes of
ranvier - abundant rER in
other: ganglia, nucleus and dendrites
myelin, axon (= Nissl substance
hillock, terminal from Nissl staining
RNA)
- ganglia: cell bodies
and/or synapses

12. 2. tissue types: epithelial tissue
Overview of tissue types: C.Riedinger
tissue layers/comp
function cell types appearance stains
type onents
- cover the body - very closely simple:
and line spaces packed epithelial = single layer
and tubes within cells - squamous - flat thin cells
it - subtype reflects difficult to distinguish
sometimes only nuclei
- protect function
visible
- absorb - goblet cells
- secrete (mucus secreting) - cuboidal - round centrally
located nucleus, often
- skin, nephrons, - hair cell (sensory)
polygonal
airways, glands, - gustatory (taste
gut... cell) - columnar - tall, elongated cells
may be ciliated
Even though not a - pseudostratified - mostly ciliated cells,
nuclei not in line
cell type: epithelial
epithelial tissue always
stratified:
(endoderm, contains a
basement = multiple layers
ectoderm)
membrane
(lamina densa) - squamous - NEVER CILIATED!
consisting of type (wear & tear)
IV collagen
- cuboidal - only top layer flat,
bottom layer cuboid
- columnar
- transitional - intermediate betw.
Stratified cuboidal and
squamous. But all
layers have the same
shape!
C.Riedinger

13. 3. anatomical structures: vessels
organs: vessels C.Riedinger
layers
blood
other
vessels internal elastic external elastic
1. Tunica intima 2. Tunica media 3. Tunica adventitia
lamina lamina
1a. Endothelium fenestrated - smooth muscle - supporting tissue:
(1 flat layer, cells difficult layer of elastin - collagen collagen
to distinguish in LM, often separating 1. - elastin less defined - contains innervation
see only nuclei) and 2.. In very - quite thick compared to and blood supply (for
layer of
1b. Basement large elastic intima very large vessels, vasa
general elasting
membrane vessels hard to vasorum)
separating 2.
1c. Connective tissue see as media - in continuation with
and 3.
has so many surrounding tissue
layers of
elastin.
+
very broad, contains
concentrically arranged
arteries,
+ + layers of elastin with + +
elastic
some smooth muscle
between layers, elastin
decreases with age
+
arteries, circumferentially
+ + + +
muscular arranged smooth
muscle
+ +
+
arteriole + (almost entirely smooth - (merges with <0.3mm diam
(thin)
muscle) surrounding tissue)
overall much
+ + thinner wall
vein - + -
(thin) (most prominent) compared to
(thin)
lumen
lymph like veins but no erys in lumen, few leucocytes and precipitaed lymp protein (artifact of preparation!)
continuous, fenestrated
+ (windows bridged by thin
capillaries (only 1a and 1b) - - - - diaphragm) or sinusuidal with
proper gaps
venule + - - - +
nuclei of endothelial cells are elongated in direction of vessel, smooth muscle nuclei are elongated circumferentially

14. 3. anatomical structures: respiratory system
organs: respiratory system (lung) C.Riedinger
1. mucosa?
compart-
2. submucosa 3. cartilage stain
ment
1a. epithelium 1b. Lamina propria 1c. Smooth Muscle
- numerous - C-shaped hyaline - H&E
- pseudostratified
seromucinous cartilage
columnar ciliated - loose connective
glands - with layers of
- many mucus tissue fibroelastic tissue
- serous cells stain
trachea secreting goblet -
- many blood between cart. rings
cells strongly
vessels - submucosa
- unusually thick - mucous cells stain
poorly merges with its
basement
perichondrium
- pseudostratified - fewer - flatter,
columnar ciliated seromuceous glands interconnected
(less tall, smaller) - more dense plates of cartilage
bronchus - fewer goblet cells - more elastic + rather than rings
- not C-shaped
- simple columnar
-seems to be there -
ciliated
- <1mm diam. -very thin - is it but much less
- smaller bronchioles
+ glands and thinner thin-walled
there?
bronchioles pulmonary artery
cuboidal
prominent feature!
- less to no goblet branches can lie
cells, but Clara cells! next to bronchiole
(= resp. bronchiole)
- lined with pneumo- - alveolar ducts: smooth muscle cells, collagen and elastic fibres
cyte type I cells (40% - alveolar septum (wall): alveolar capillaries and sparse network of elastin and collagen
covering 90%)
with pneumocytes of the walls of the two adjacent alveoli next to it
- can only see nuclei
- 60/10% pneumocyte - septum also contains few fibroblasts
alveoli
type II (cuboidal, much - elastin and collagen condense around alveolar openings to form supporting network
CP, secrete surfactant) for lung parenchyma (parenchyme = bulk of a substance = lung material)
- endothelial cell on the
- 8um openings in septum: alveolar pores (of Kohn) for air exachange
blood side
- also alveolar macrophages (dust cells) with thin flattened, even nucleus

15. 3. anatomical structures: urinary system
organs: urinary system (kidneys) C.Riedinger
compartment epithelium other cells features (Wheater's p. 318, 320,325)
simple squamous endothelium 1. juxtaglomerular
afferent arteriole - modified smooth muscle cells
cells
simple squamous endothelium - podocytes - 1* and 2* foot processes
(fenestrated) - mesangial cells - embrace capillary loops
- filtration barrier: 1. Endothelial cells, 2. Basement
2. extraglomerular
membrane, 3. podocytes
mesangial cells
- contractive cells, phagocytotic (can reduce GFR)
glomerulus
JUXTAGLOMERULAR APPARATUS - surround glomerular capillaries
renal formed by comparments of - mesangium = supportive tissue similar to basement
corpuscle glomerulus, afferent arteriole and membrane, cytoplasm very stained
- flat, elongated continuous with glomerular mesang. cells
distal convoluted tubule
- conical mass, cytoplasmic processes
simple squamous epithelium - invaginated sphere
bowman's
- - visceral and parietal layer
capsule
(but where is visceral layer? Can't see it on EM)
simple cuboidal epithelium - brush border (aids reabsorbtion)
proximal convoluted tubule
- - many mitochondria, endocytotic vesicles and
(PCT)
lysosomes - FUZZY LUMEN!!!
thin descending and thin simple squamous epithelium
-
ascending loop of henle
thick ascending loop of simple cuboidal epithelium (low)
-
henle
3. macula densa - NO brush border!
simple cuboidal epithelium - smaller cells, stain less intensely
- CLEAR LUMEN!!!
(where in contact with
- nucleus protrudes into lumen
distal convoluted tubule glomerulus)
- cell volume smaller
(DCT)
- specialised epithelial cells
- closely packed, taller, thin basement membrane
- located on side of DCT that faces corpuscle
simple cuboidal epithelium - wider than CDT
collecting tubules (CT) -
- less regular in shape
simple columnar epithelium - principal cells - large diameter - pale cytoplasm, few organelles
collecting duct (CD) - a-intercalated cells - pale stained - short microvilli
- darker cytoplasm, many mitos, vesicles (H+)
stratified transitional epithelium - 3-6 layers
ureter, bladder - - thick luminal surface
- impermeable to urine/water

16. 3. anatomical structures: glands
organs: glands C.Riedinger
type of gland arrangement main component ducts features other
acini (end pieces) =
intercalated ducts
clusters of mucus mucus secreting: bigger, sain pale lots of vessels, nerves,
lobules separated by leading to striated
secreting cells, serous with nuclei on side. Serous (parasympathetic) ganglions,
Salivary septa, surrounded by ducts, stain red.
secreting cells, or a mix of secreting: smaller, stain strongly, extretory ducts, connective
capsule Simple cuboidal epi,
both. Duct system more pyramidal/cuboidal cells tissue, lymphatic vessels
central round nucleus
prominent
acini (exclusively serous intercalated ducts
arranged circularly with abundant blood supply, network
with central nuclei, (difficult to ID with
lateral nuclei (apex towards of arterioles. in ducts:
surrounded by fine LM), leading to
inside, nucleus basal), tiny cells change from squamous or
network of supporting intralobular and
lobules separated by lumen, sometimes centroacinar cuboidal epithelium to stratified
tissue containing interlobular ducts (big
loose supporting tissue cells cuboidal in large ducts
sinusoids) lumen)
surrounded by
Pancreas collagenous capsule. immunological stain for glucagen
Exocrine (80-85%) and smaller, scattered pale staining (alpha-cells, smaller) or insulin
endocrine (1-2%) blobs of varying size, cells (beta-cells, stain with aldehyde
features! islets of langerhans - contained smaller than acinar fuchsin) reveals that glucagon is
cells, evenly distributed cells with produced in the periphery
evenly distributed nuclei whereas insulin is produced
centrally
polyhedral cells with round
nuclei, some binucleated,
hepatocytes and sinusoid arranged into branching sheaths
arterioles of 1 cell thickness, separated by
sinusoids which appear as empty macrophages (Kupffer cells)
spaces present in sinusoids to remove
polygonal lobules with
canaliculi with microvilli debris, sinusoids have gaps
thin boundaries of
Liver that run countercurrent between endothelial cells to
collagenous supporting
portal tracts/triads: entry to the sinusoids promote exchange of plasma
tissue
site of blood from thin-walled veins, thicker walled components with the
terminal branches of arteries, darkly staining bile hepatocytes (see EM).
portal vein and hepatic ducts. Also contains lymphatic
artery, leads to central tissue/ducts which is often
vein, exit of bile duct collapsed
(canaliculus).

17. 3. anatomical structures: glands (2)
organs: glands C.Riedinger
type of gland arrangement components products features other
follicles, contain thyroid morphology ~ activity: resting hormones bound to
hormones stored in tri-iodothyronine, 4- thyroid follicular cells flattened, thyroglobulin, a glycoprotein,
homogenous colloids, iodothyronine lots of colloid, active thyroid when stored. Thyroid gland is
lined with single layer of (=thyroxine) follicular cells large, columnar, unique in storing lots of hormone
Thyroid lobulated cuboidal follicular cells basal nucleus, less colloid when inactive!
scattered, lumps or single cells,
endoneurocrine, derived from
parafollicular cells calcitonin near fenestrated capillaries for
neural crest cells?
hormones to enter blood stream
poorly defined lobules large, round nuclei, resting cells have
chief/principal cells pale cytoplasm, prominent golgi, rER,
+ septa contained in PTH
(most common) secretory granules. When active
the capsule of thyroid glandular elements can be
smaller, more rER, stain more strongly
gland (septa [blue] = intermixed with adipose cells, in
Parathyroid
extensions of capsule age becomes infiltrated by
containing eosinophilic cytoplasm, numerous lymphocytes
neurovascular oxyphil cells (minor
unknown mitochondria, larger than
structures) component)
principal cells
glandular epithelium,
intimate vascular cords or clumps of cells, sinusoid
*50% somatrophs (GH)
connections with capillaries, collagen and reticulin
Anteroir 20% corcitutrophs (ACTH)
hypothalamus. GH, ACTH, LH, FSH, network, chromophobes:
pituitary blob 20% lactrotrophs (prolactin)
chromophobe and prolactin, thyrotrophin smallest, few granules,
(adeno) 5% gonadotrophs (LH, FSH)
chromophil cells = chromophils: acidophil or
5% thyrotrophs (thyrotrophin)
~troph cells with lots of basophil.
granules*
axons: lots of granules,
accumulate in distended
terminations = Herring bodies,
Posterior non-myelinated axons,
connects to granules contain hormone cell bodies of axons in
pituitary pituicytes (speciallised ADH, oxytocin
hypothalamus via stalk precursors generated in cell body, hypothalamus
(neuro) glial cells)
final hormone generated during
transport. Pituicyte EM: few
granules

18. 3. anatomical structures: GI tract
C.Riedinger

19. 4. identify: blood cells (connective tissue)
BLOOD Wheater's: table page 64
1. red blood cells:
- total absence of organelles
- no nucleus
- flattened disc with elevated circumference
- reticulocytes (= precursors, <1% of circulating erys) have some residual nuclear material
- very young cells some rER and mitochondria
2. white blood cells: (1/1000 blood cells)
5 types, named based on staining properties of granules
granulocytes: Neutrophils do not stain in humans 60%
eosinophils pick up eosin and therefore stain orange 3%
basophils pick up azures and therefore stain blue, rarest cells 1%
single multilobed nuclei (polymorphonuclear)
originally believed to be polynuclear
mononuclear leucocytes: lymphocytes clear cytoplasm, rounded nucleus 34%
(agranular) monocytes large, indented curved nucleus 4%
non-lobulated nuclei
agranolucytes
3. platelets:
- small
- non-nucleated
- round or oval, biconvex
- cytoplasm purple stained
- granules = 20% of platelet volume
- many organelles
C.Riedinger

20. 4. identify: blood cells (connective tissue) (2)
C.Riedinger

21. 4. identify: type of ganglia (nervous tissue)
C.Riedinger
how to distinguish ganglia
cell bodies are large with smaller supporting cells around it
symp + parasymp: contain synapses (stellar ganglion = largest symp ganglion)
sensory: just contain cell bodies
appearance
sensory ganglion: many and larger nuclei of satellite (supporting cells), form neat circle around cell body, even larger cell bodies
pseudounipolar neurons!
sympathetic ganglion: smaller and more scattered satellites, smaller cell bodies
more space between cell bodies as axons and dendrites have to pass through!
same basic structure as sensory ganglia
parasymp. Ganglion: near target organ! Islands of connective tissue with blood vessels, nerves and ducts
nerve cell bodies lie within nerve trunk, are surrounded by support cells,
less satellites, smaller cell bodies
large cell bodies and axons
nerves in longitudinal section
zig-zaggy strands with nuclei of schwann cells visible
each myelin producing schwann cell covers ca. 1mm of the nerve fibre
in-between: nodes of ranvier
often stained black with pink connective tissue in-between individual myelinated fibres

22. 4. identify: GI tract
- looks more structured than
stomach C.Riedin
organs: alimentary system (gut)
- mucin stains more blue than
cyan
Wheater's: page 286, 287, for glands 97
How to distinguish different parts of the gut:
Are there villi?
* Yes Small intestine: Duodenum/Jejunum/Ileum
Are there brunner's glands?
* Yes Duodenum
* No Jejunum/Ileum
Are there peyer's patches?
* Yes Ileum
* No Oesophagus/Stomach/Colon * No Jejunum
Are there glands?
* Yes Stomach/Colon
What do the glands look like?
Straight and beautiful Colon
Thick very thick layer
underneath ducts, less Stomach
ordered
* No Stratified squamout epithelium? Oesophagus

23. 4. identify: urinary system
organs: urinary system (kidneys) C.Riedinger
adrenal gland
egulfed in dense supporting tissue that extends into gland to support secretory cells
zona glomerulosa 5-10%
secretes mineralocorticoids (e.g. aldosterone)
whorls of cells and capillaries
zona fasciculata 75%
narrow cords of large cels
sinusoid capillaries
cortex: rich in sER and lipids
"foamy"
secretes glucocorticoids (e.g. cortisol)
zona reticulosa irregular network of branching cords
numerous capillaries of wide diameter
smaller cells than other two layers
secretes androgenic steroids
medulla: chromaffin cells clumps and cords of cells
surrounded by fine supporting tissue
large nucleus (stains blue)
basophilic cytoplasm
secretes catecholamines (e.g. (nor)adrenaline)
steroid secreting cells: many mitochondria with unusual tubular cristae
sER
lipid droplets (if secreting cholesterol, in cortex)
membrane-bound granules (if secreting catecholamines in medulla, but those are not steroids)

24. The End.