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Fundamentals of
Histology
Part I
Mohammad R. Fath-Elbab
Alaa Sayed Abou-Elhamd
i
Histology
Part I
Mohammad R. Fath-Elbab
Professor of Histology.
Faculty of Veterinary Medicine.
Assiut University.
Alaa S. Abou-Elhamd
Lecturer of Histology.
Faculty of Veterinary Medicine.
Assiut University.
ii
Contents
1-THE CELL …………………………………………………………………..1
The structure of the cell 1 The cell organelles 2
The cell membrane 1 The cell inclusions 6
The cytoplasm 2 The nucleus 7
THE EPITHELIAL TISSUE…………………………………………………9
I- Epithelial membranes 9 II- Glands 12
Types 9 Modifications in cell surface 14
A) Simple epithelium 9 Modifications in cell constituents 16
B) Stratified epithelium 10
THE CONNECTIVE TISSUE……………………………………………….18
Structure 18 B) The connective tissue fibers 21
A) The cellular elements 18 C) The matrix 21
Types of connective tissue 21
I- Connective tissue proper 21
1- Loose connective tissue. 21 2- Dense fibrous connective tissue 22
II- Cartilage 23
1- Hyaline cartilage 24 2- Elastic fibrocartilage 24
3- White fibrocartilage 25
III- Bone 25
A) Bone cells 25 B) Matrix 26
Types of bones 26
1. Cancellous bone (spongy bone) 26 2. Compact bone 26
Ossification (development of bone) 27
1- Intramembranous ossification. 27 2- Intracartilagenous ossification 27
BLOOD…………………………………...……………………………………29
I- Erythrocytes 29
II- Leukocytes (white blood cells) 29
iii
Granular leukocytes 29 Neutrophil leukocytes 29
Eosinophil leukocytes. 30 Basophil leukocytes 30
Agranular leukocytes 30
A) Lymphocytes. 30 B) Monocytes 30
III- Blood platelets 31
THE MUSCULAR TISSUE………….………………………………………32
1. The smooth muscle 32 3- The cardiac musc 34
2. The skeletal muscle 33
THE NERVOUS TISSUE…………………………………………………….35
I- Nerve cells (Neurons) 35
A) The cell body 35 B) The cell processes 35
Types of nerve cells 36
II- Nerve fibers 36 Type of nerve fibers 36
Synapse (s) 37 Nerve trunk 37
Ganglia 38
Sympathetic ganglion 38 Spinal gangli 38
III- NeurogIia 39
A- Neuroglia proper 39
1-Astrocytes 39 2- Oligodendrocytes 40
3-Microglia 40
B- Other types of neuroglia 40
References……………………………………………………………………41
THE CELL
The cell is the structural unit of
the living organism. Organized
animals possess millions of cells
tissues organs systems.
The cells differ into:
Shape:
Flat (Fig. 1a)- spindle (Fig. 1b)-
cuboidal (Fig. 1c)- columnar (Fig.
1d) - triangular (Fig. 1 e) - spherical
(Fig. 1f)- irregular (star- shape, Fig.
1.g)- flagellated (Fig. 1h).
Size:
Small - large.
Fig.1: The morphology of a cell varies
according to its function.
The structure of the cell:
The cell (Fig. 2) consists of:
I. Cell membrane.
II. Cytoplasm.
III. Nucleus.
Fig: 2 Structure of the cell. 1. The nucleus, 2.
The nucleolus, 3. The nuclear membrane,
showing nuclear pores, 4. Rough endoplasmic
reticulum, 5. Smooth endoplasmic reticulum.,
6. Golgi apparatus, 7. Centrioles, 8. Secretory
granule, 9. Mitochondrion, 10. Phagocytosis,
11. Basal invagination, 12. Ribosome, 13. Cell
membrane, 14. Endocytosis, 15. Microvilli, 16.
Exocytosis, 17. Zonula occludens, 18. Zonula
adherens, 19. Desmosome, 20.
Hemidesmosome, 21. Basal lamina, 22.
Residual body, 23. Glycogen, 24.Microtubule.
I. The cell membrane
(Plasmalemma):
* L/M: Can not be seen.
* E/M: Unit membrane.
75-100 A° in thickness.
Trilaminar membrane (Fig. 3& 4)
consists of:
i) Osmiophilic layer: Electron dense.
ii) Osmiophobic layer: Less electron
dense.
iii) Osmiophilic layer: Electron
dense.
Fig. 3: The plasmalemma of two neighbouring
cells (arrows). Each is formed of trilaminar
membrane consisting of two dark lines
separated by an intermediate light zone.
Fig. 4: A. The ultrastructure of the cell
membrane: 1 + 2 - two electron dense
osmiophilic layers. 3 - A less electron dense
osmiophobic layer. B. The molecular structure
of the cell membrane: 1. Bimolecular lipid
layer. 2. Hydrophobic (nonpolar) ends. 3.
Hydrophilic (polar) ends. 4. Protein molecules.
5. Carbohydrate chains. 6. Cholestrol
molecules.
II- The cytoplasm:
Contains cell organelles and cell
inclusions.
A) The cell organelles:
Living materials.
Consist of:
i) Membranous cell organelles.
ii) Non-membranous cell organelles.
i) The membranous cell organelles:
1. Mitochondria:
* They are also called:
Power - house of the cell.
Energy - producing center.
Cell - respiration center.
* L/M: Appear as black filaments and
spheres when stained with iron-alum
haematoxylin or acidophilic with
trichrome (Fig. 5).
Fig. 5: The salivary duct, showing mitochondria
(acidophilic basal striation, arrows), trichrome
stain.
* E/M: Tubules (Fig. 6), each
consists of:
1. Outer membrane: smooth.
2. Inner membrane: folded
(cristae).
3. Outer chamber.
4. Inner chamber = Matrix:
Consists of:
Oxidative enzymes - DNA - RNA -
Granules.
Found into:
Muscle fibers.
Heart.
Liver.
Kidney tubules.
Sperms.
Fig. 6: The mitochondrion: 1. Outer membrane.
2. Inner membrane. 3. Cristae. 4. Inner
chamber. 5. Outer chamber.
2. Endoplasmic reticulum (ER):
* Types:
a) Rough endoplasmic reticulum
(rER):
* L/M: Basophilia of the cytoplasm
(Fig. 7).
* E/M: Irregularly branched
membranous tubules (CISTERNAE),
covered with fixed ribosomes (Fig.
8).
Found into:
Pancreas - Nerve cells - Endocrines -
Plasma cells.
Fig. 7: Serous acinus, showing basal basophilia
(rER), H & E stain.
Fig. 8: Rough endoplasmic reticulum (asterisks)
into a pancreatic acinar cell
b) Smooth endoplasmic reticulum
(sER)
* L/M: Cannot be seen.
* E/M: Irregular branched
membranous tubules (CISTERNAE)
with no ribosomes (Fig. 9).
Found into:
Testis - Skeletal muscles fibers -
Heart.
Fig. 9: Smooth endoplasmic reticulum into a
liver cell (Arrows).
3. Golgi apparatus:
* L/M: Appears as clear unstained
area near the nucleus (negative Golgi
image) when stained with H&E.
Apears as dark brown filaments and
granules when stained with silver
impregnation or Osmic acid (Fig.
10).
* E/M:
A- Membranous saccules (STACKS),
Fig. 11, each has:
i) Convex surface: immature
(forming) face.
ii) Concave surface: mature
(secretory) face.
B- Transfer vesicles.
C- Secretory vesicles.
Found into:
Pancreas - Liver - Nerve cells.
Fig. 10: A nerve cell, showing Golgi apparatus
(arrowheads) surrounding the nucleus (arrow),
silver impregnation.
Fig. 11: The Golgi apparatus. 1. The nuclear
membrane. 2. Rough endoplasmic reticulum. 3.
Transfer vesicles. 4. Forming face of Golgi
apparatus. 5. Secretory face of Golgi apparatus.
6. Secretory vesicle.
4. Lysosomes:
* L/M: Histochemically (Acid
phosphatase reaction).
* E/M: Membranous vesicles
containing lytic enzymes (Fig. 12).
Types:
a) Primary lysosomes:
Fresh vesicles.
b) Secondary lysosomes:
Primary vesicles fused to phagocytic
vesicles.
Found into:
Macrophages - Neutrophil leukocytes
- Monocytes.
Fig. 12: Lysosomes into the adrenal cortex
(Arrows).
5. Peroxisomes = Microbodies:
* L/M: Can not be seen.
* E/M: Membranous spheres (Fig.
13) containing enzymes e.g. catalase.
Found into:
Liver cells.
Fig. 13: Peroxisomes (Microbodies) into a liver
cell.
ii) The non-membranous cell
organelles:
1. Ribosomes:
* L/M: Cytoplasmic basophilia.
* E/M: Granules of RNA. (large
subunit + small subunit).
Types:
i) Monoribosomes: single.
ii) Polyribosomes: groups.
Found into: Pancreas - Endocrines -
Plasma cell.
2. Centrioles:
* L/M: Two spherical bodies.
* E/M: Two hollow cylinders
perpendicular on each other.
The wall of each cylinder consists of
9 triplets of microtubules (Fig. 14&
15).
Found into:
Ciliated cells, Sperms and Epidermis
(skin).
Fig. 14: The cytoplasmic microtubule and
centriole. A- C.S. of microtubule: 1.
Protofilaments (n=13). B-L.S. of centriole: 1 +
2 + 3 = Microtubular triplets. 4- Protein links.
Fig. 15: Centriole into a pancreatic acinar cell.
(Transverse section).
3. Cytoskeleton:
* L/M: Could not be seen.
* E/M: Consists of:
i) Microfilaments (Fig. 16): Actin -
myocin (sk. muscles).
Fig. 16: Myofilaments (L.S.) into a skeletal
muscle fiber
ii) Microtubules: 13 protofilaments
(Cilia).
iii) Intermediate filaments:
(Absorptive cells).
iv) Microtrabeculae:
Connect microfilaments and
microtubules with the cell organelles.
B) The cell inclusions
(Paraplasma):
Non-living materials.
1. Stored food:
a) Carbohydrates = glycogen (Best's
carmine Red). (PAS purple,
Fig. 17).
E/M: rosette- shape particles (Fig.
18).
Fig. 17: Glycogen granules into the liver cells,
PAS (asterisks).
Fig. 18: Glycogen particles into a hepatic cell
(E/M). Notice the rosette- shape particles of
glycogen (alpha- particles, arrows).
b) Lipids = Fat (Sudan black
black), (Fig. 19).
Fig. 19: Lipid droplets (arrows) into a Sertoli
cell (E/M).
c) Proteins = (Bromophenol blue
blue)
2. Secretory granules:
Zymogen granules (H & E Red,
Figs. 7& 20).
Fig. 20: Secretory granules into the pancreatic
acinar cells (asterisks), Azan stain.
3. Pigments:
i) Exogenous = Carotin - dust -
lipochrome.
ii) Endogenous = Haemoglobin –
melanin (Fig. 21).
Fig. 21: Melanin pigments (arrows) into a
pigment cell from the iris (E/M).
III- The nucleus:
Shape = spherical - oval - crescent -
segmented (lobulated).
Size = small - large.
Structure:
1. Nuclear membrane:
• Double unit membrane (outer –
inner (Fig. 22).
• Perinuclear space.
• Nuclear pores.
Fig. 22: A nuclear membrane (arrows) into an
erythroblast
2. Chromatin:
i) Euchromatin: extended (active).
ii) Heterochromatin: condensed
(inactive, Fig. 23).
Sex chromatin = condensed x-
chromosomes (in females):
* Drum-stick (in neutrophil
leukocytes, Fig. 24).
* Small dense granules adhering to
the nuclear membrane (in oral
epithelium).
Fig. 23: Acinar cell from the pancreas. Notice
the nuclear structure. Nucleolus. Nuclear
membrane (arrows). Nuclear pores
(arrowheads). Chromatin.
Fig. 24: The sex chromatin in a
polymorphonuclear leukocyte (female). It has a
drum-stick shape (arrowhead).
3. Nucleolus:
(Fig. 23)
i) Pars granulosa (RNA).
ii) Pars fibrosa (DNA + RNA).
iii) Perinucleolar chromatin.
iv) Intranucleolar chromatin (DNA).
v) Matrix (RNA).
4. Nuclear sap:
Colloidal solution.
THE EPITHELIAL TISSUE
The epithelial tissue is formed of
closely aggregated cells with a very
little intercellular substance.
It forms either membranes or glands.
I- Epithelial membranes:
General features:
• Line body cavities.
• Cover body surfaces.
• Originate from the 3 germ layers.
• Lack blood vessels.
• Have terminal sensory nerves.
• Have a basement membrane.
• Divide mitotically.
Types:
A) Simple epithelium:
One layer.
i) Simple squamous epith.:
Peritonium - pleura-blood vessels
(Figs. 25& 26).
Fig. 25: Simple squamous epithelium (surface
view). Endothelium of vein (A) and artery (B).
Fig. 26: Simple squamous epithelium, A:
(Lateral view, arrowheads), Blood capillary
(Azan stain). B: (Surface view), Buccal
mucosa.
ii) Simple cuboidal epith.:Thyroid –
ovary (Fig. 27).
Fig. 27: Simple cuboidal epithelium into a
collecting tubule (arrowheads, Kidney). A:
(Azan stain), B: H & E.
iii) Simple columnar epith.:
• Nonciliated: Stomach - intestine.
• Ciliated: Oviduct (Fig. 28).
Fig. 28: Simple columnar epithelium. A: H &
E. B: (Diagrammatic illustration) notice the
kinocilia (arrows).
iv) Pseudostratified columnar epith.:
Tall cells + short cells.
• Non ciliated: uterus.
• Ciliated:
a- Kinocilia: trachea (Fig. 29).
b- Stereocilia: epididymis.
Fig. 29: Pseudostratified columnar ciliated
epithelium with goblet cells (Trachea,
arrowheads): A: Diagram, B: (Azan stain). C
(Diagrammatic illustration) showing steriocilia
(arrows).
B) Stratified epithelium:
Several layers.
i) Stratified squamous epithelium:
• Basal: Columnar cells.
• Middle: Polyhedral, cells.
• Superficial: Flat cells.
Types:
• Non cornified: Oesophagus
(Fig.30A).
• Cornified: Hard palate (Fig.30B&
C).
Fig. 30: A) Stratified squamous non-cornified
epithelium. B) Stratified squamous cornified
epithelium. C) Stratified squamous cornified
epithelium (Azan stain). 1. Columnar or
cuboidal cells. 2. Polyhedral cells. 3. Squamous
cells. 4. Horny layer (keratin).
ii) Stratified columnar epithelium:
• Basal: Columnar cells.
• Middle: Polyhedral cells.
• Superficial: Columnar cells.
• Large ducts of salivary glands (Fig.
31).
Fig. 31: Stratified columnar epithelium
(Azan stain).
iii) Stratified cuboidal epithelium:
Two layers of cuboidal cells (Fig.
32).
• Ducts of the mammary glands.
Fig. 32: Stratified cuboidal epithelium (H & E).
iv) Transitional epithelium:
• Basal: Cuboidal cells (Fig. 33a).
• Middle: Pear – shaped cells (Fig.
33b) .
• Superficial: dome-shaped cells (Fig.
33c).
• Ureter - Urinary bladder (empty)
In case of full bladder:
• Basal : Cuboidal.
• Superficial: flat.
Fig. 33: Transitional epithelium (Azan stain).
II- Glands:
1. Endocrine glands: Ductless-secrete
hormones.
2. Exocrine glands:
i) Unicellular glands: Goblet cells
(intestine).
ii)Multicellular glands: Duct(s) +
End-piece(s).
Classification:
According to:
1. The shape:
i) Simple glands: Single duct.
• S. tubular (sweat glands, Fig. 34a).
• S. alveolar (sebaceous glands, Fig.
34b).
• S. tubulo-alveolar (small salivary
glands, Fig. 34c).
ii) Branched glands: Branched end-
pieces.
• B. tubular (gastric glands, Fig. 34d).
• B. alveolar (tarsal glands, Fig. 34e).
• B. tubulo-alveolar (prostate, Fig.
34f ).
iii) Compound glands: Branched
ducts.
• C. tubular (liver, kidney, Fig. 34g).
• C. alveolar (mammary gland, Fig.
34h).
• C. tubulo – alveolar (pancreas, Fig.
34i ).
Fig. 34: Classification of the multicellular
glands according to the shape: a- Simple tubular
gland. b- Simple alveolar gland. c- Simple
tubulo-alveolar gland.d- Branched tubular
gland. e- Branched alveolar gland. f- Branched
tubulo-alveolar gland.g- Compound tubular
gland. h- Compound alveolar gland. i-
Compound tubulo-alveolar gland.
2. The nature of secretion:
i) Serous end-pieces:
• Pyramidal cells.
• Rounded nucleus.
• Narrow lumen.
• Pancreas – parotid (Fig. 7& 35).
Fig. 35: Serous gland, H & E.
ii) Mucous end - pieces:
• Cuboidal cells.
• Flat nucleus.
• Wide lumen.
• Palatine salivary gland (Fig. 36).
Fig. 36: Mucous gland (Trichrome stain).
iii) Mixed end-pieces:
• Crecents.
• Cell by cell.
• Acinus by acinus.
• Mandibular salivary glands (Fig.
37A& B).
Fig. 37: A: Mixed gland (Trichrome stain). B:
Mixed end-piece, H & E.
3. The mode of secretion:
i) Merocrine glands:
• No loss of cytoplasm.
• Pancreas.
ii) Apocrine glands:
• Loss of the cell apex.
• Mammary gland.
iii) Holocrine glands:
• Destruction of the whole cell.
• Sebaceous gland (Fig. 38).
Fig. 38: Sebaceous gland, H & E.
Modifications of the epithelial cells
to correlate certain functions:
I- Modifications in cell surfaces:
A) Basal border:
a- Basal infoldings: Long
invaginations of the basal plasma
membrane.
Found into: ion-transport cells
e.g. the proximal convoluted tubules
of the kidney (Fig. 39).
b- Hemidesmosomes: These
structures take the form of half a
desmosome on the epithelial cell
plasmalemma. They probably serve
to bind the epithelial cell to the
subjacent basal lamina. Found into
epidermis.
Fig. 39: Ion - transport cell: Showed 1 -
Invaginations of the basal cell membrane. 2-
Basement membrane. 3- Mitochondria. 4 -
Invaginations of the lateral cell surface. 5-
Apical microvilli.
The basal border rests on a basement
membrane which consists of :
1. Basal lamina: granular
(glycoprotein).
2. Middle layer: amorphus (protein +
polysacch.).
3. Reticular layer: reticular fibers.
B) Apical border:
1. Striated border = Microvilli (Fig.
39).
2. Cilia:
a) Stereocilia (Fig. 29).
b) Kinocilia (Fig. 28& 40):
•Peripherally: 9 double microtubules.
• Centrally: 1 double microtubule.
Fig. 40: The cilium (Kinocilium): a - The shaft;
1. Cell membrane. 2. Two central microtubules.
3. Central sheath. 4. Nine double peripheral
microtubules. 5. 2-3 protofilaments. 6. Nexins.
7. Radial spokes. b- The base: 8. Nine triple
peripheral microtubules. 9. Basal body.
3. Flagella:
They are similar in structure to
cilia but are much longer and single.
They are found into spermatozoa.
C) Lateral border:
1. Zonula occludens (intestine) , Fig.
41.
2. Zonula adherens (intestine), Fig.
41.
3. Desmosome (intestine + skin) , Fig.
41& 42.
1+2+3 = Junctional complex
(intestine).
4. Gap junction (Heart - intestine),
Fig. 41& 43.
5. Interdigitated membranes
(Kidney).
Fig. 41: Specialization of the lateral border
Fig. 42: Macula adherentes (Desmosome):A:
1- Intercellular space. 2 - Electrons obaque
central line.3- Dense attachment plate. 4-
Microfilaments (tonofilaments). 5-
Transemembrane linker. B: (arrow).
Fig. 43: Gap junction: 1 - Parallel hollow tube-
like protein structure.
II- Modifications in cell
constituents:
1. Protein - secreting cell = Abundant
rER.
Found into: Pancreas.
2. Glyco-protein-secreting cell:
Abundant mucigen granules.
Found into: Goblet cell
3. Steroid-secreting cell = Abundant
sER.
Found into: Testis.
4. Iron-transport cell = Abundant
mitochondria (Fig. 39).
Found into: Kidney.
5. Neuro-epithelial cell = Abundant
microvilli (Fig. 44).
Found into: Taste buds.
Fig. 44: Taste bud: 1 - Neuroepithelial cell.
(Light cell). 2 - Nerve ending. 3 - Microvilli. 4 -
Basal cells. 5 - Supporting cells. (Dark cell).
6. Epithelial reticular cell = Abundant
cytofilaments (Fig. 45).
Found into: Thymus.
Fig. 45: Epithelial reticular cell: 1- Cytoplasmic
process. 2- Nucleus. 3- Cytofilaments. 4-
Desmosome.
6. Myoepithelial cell = Abundant myofilaments (Fig. 46).
Found into:
Salivary glands - mammary gland.
Fig. 46: Myoepithelial cell "Basket cell": 1 - Salivary adenomere. 2- Myoepithelial cell.
3- Cytoplasmic processes. 4- Nucleus. 5- Myofilaments. 6 - Cell organelles.
THE CONNECTIVE TISSUE
The connective tissue is formed of
widely scattered cells with plentiful
intercellular substance.
Structure:
The connective tissue consists of:
A) The cellular elements.
B) The connective tissue fibers.
C) The matrix or ground intercellular
substance.
A) The cellular elements:
1.Undifferentiated mesenchymal
cells (UMC):
• Small banching cells (Fig. 47).
• Large pale nucleus.
• Divide and differentiate into other
cell types.
Found into: The embryo around the
blood capillaries.
2. Fibroblast cells:
Two types:
a) Young active cells (Fibroblasts):
• Large cells with cytoplasmic
processes (Fig. 48A).
• Large pale nucleus.
• Basophilic cytoplasm (rich in rER).
b) Mature inactive cells (Fibrocytes):
• Smaller, spindle-shaped (Fig. 48B).
• Small dark nucleus.
• Acidophilic cytoplasm.
Fig. 47: Undifferentiated mesenchymal cell. 1.
Cytoplasmic processes. 2. Mitochondria. 3.
Rough endoplasmic reticulum. 4. Golgi
apparatus.
Fig. 48: A- Fibroblast: B - Fibrocyte: 1-
Cytoplasmic processes. 2- Nucleus. 3- Rough
endoplasmic reticulum. 4- Golgi apparatus.
3. Macrophages:
• Oval, rounded, branched cells (Fig.
49).
• Small, kidney-shaped nucleus.
• Many lysosomes - Many
mitochondria - Well developed Golgi
apparatus.
Fig. 49: Macrophage: 1. Cytoplasmic
processes. 2. Nucleus. 3. Golgi apparatus. 4.
Lysosome. 5. Rough endoplasmic reticulum. 6.
Free ribosomes. 7. Mitochondria.
4. Plasma cells:
• Large, round or oval cells (Fig. 50).
• Eccentric, rounded nucleus (cart -
wheel or clock – face chromatin).
• Highly basophilic cytoplasm (rER).
• Well developed Golgi apparatus
(Antibodies).
Fig. 50: Plasma cell: 1. Basophilic cytoplasm.
2. Juxtanuclear pale area. 3. Nucleus. 4. Rough
endoplasmic reticulum. 5. Golgi apparatus. 6.
Centrioles. 7. Mitochondria.
5. Mast cells:
• Large, oval, rounded or irregular
cells (Fig. 51).
• Central nucleus.
• Metachromatic cytoplasmic
granules (Heparin - histamin -
serotonin) - Toluidine blue Red.
Fig. 51: Mast cell: 1. Cytoplasmic processes. 2.
Coarse cytoplasmic granule. 3. Mitochondria.
4. Golgi apparatus.
6. White fat cells: "Unilocular
adipocytes".
• Large, oval or rounded cells (Fig.
52).
• Flat, peripheral nucleus.
• Cytoplasm is occupied by a large
fat globule (Signet - ring).
Fig. 52: White fat cell: (Unilocular adipocyte).
1. Cytoplasm (thin film). 2. Mitochondria. 3.
Fat globule. 4. Nucleus.
7. Brown fat cells: "Multilocular
adipocytes"
• Smaller, polygonal cells.
• Spherical eccentric nucleus.
• Cytoplasm contains multiple small
fat droplets and many cytochrome -
rich mitochondria (Fig. 53).
Fig. 53: Brown fat cell: (Multilocular
adipocyte). 1. Small lipid droplets. 2. Nucleus.
3. Nucleoli. 4. Cytoplasm (abundant). 5.
Mitochondria.
8. Pigment cells:
• Large, branched cells (Fig. 54).
• Small, rounded nucleus.
• Cytoplasm contains melanin
pigments.
Fig. 54: Pigment cell.
9. Eosinophil leukocytes:
• Rounded or oval cells (Fig. 55).
• Nucleus is bilobed.
• Cytoplasm contains coarse
acidophilic granules.
E/M:
The cytoplasmic granules consist of:
• Matrix.
• Equatorial band.
Fig. 55: Eosinophil leukocyte, A: 1 - Nucleus.
2 - rER (Few). 3 - Free ribosomes. 4 -
Mitochondria (small). 5- Cytoplasmic granules.
6 - Equatorial band. B: Blood film.
B) The connective tissue fibers:
1. White collagenous fibers:
• Run in wavy bundles.
• The bundles branch but the fibers
do not branch.
• Stain blue with Mallory's stain.
• Found into tendons (Fig. 56).
Fig. 56: A: The collagenous fibrils showing
periodicity of light and dark bands. B: Tendon
(L.S.) H&E.
2. Yellow elastic fibers:
• Thin-long (Fig. 57).
• Branch and form networks.
• Stain brown with orcein or deep
blue with Resorcin-fuchsin.
• Found into lung - aorta.
Fig. 57: Elastic fibers into the wall of aorta,
orcein stain.
3. Reticular fibers: (Argyrophilic
fibers).
• Very thin.
• Branch and form fine networks.
• Stain black with Ag N03 (Fig. 58).
• Found into spleen - liver.
Fig. 58: Reticular fibers within the hepatic
lobule (silver impregnation).
C) The matrix:
Consists of:
1. Amorphous viscid (jelly - like)
substance (mucopolysacch.).
2. Tissue fluid.
Types of connective tissue:
I- Connective tissue proper:
1. Loose connective tissue:
• All c.t. cells (Fig. 59).
• All c.t. fibers.
• Matrix.
Found into: subcutaneous c.t.
Fig. 59: Loose connective tissue.1. Fibroblasts.
2. Fibrocytes. 3. Fat cells. 4. Pericytes.5.
Macrophages. 6. Mast cells. 7. Lymphocytes. 8.
Plasma cells. 9. Eosinophilic leukocyte.10.
Monocyte. 11. Reticular fibers. 12. Collagenous
fibers. 13. Elastic fibers. 14. Lymphatic vessels.
15. Blood vessels. 16. Nerve fibers.
2. Dense fibrous connective tissue:
A) Dense white fibrous c.t.:
= Dense regular white fibrous c.t.:
• Collagenous fibers (Dense parallel
bundles), Fig. 60.
• Fibroblasts (compressed).
• Matrix - poor in blood vessels.
Found into: Tendons.
Fig. 60: Tendon (L. S.), Picrocarmine stain.
B) Dense elastic connective tissue:
= Dense regular elastic c.t.:
• Elastic fibers (parallel), Fig. 57.
• Few collagenous fibers.
• Fibroblasts.
Found into: Ligamentum nuchae.
3. Adipose connective tissue:
A) White adipose tissue:
• White fat cells - (lobules - lobes).
• Reticular fibers.
• Numerous blood vessels.
Found into: hump of camel -tail of
sheep.
Fig. 61: White adipose c. t. A: 1. Fat cells
(signet ring). 2. Reticular fibers. 3. C. t. septa.
4. Blood vessel. B: Oil red O.
B) Brown adipose tissue:
• Brown fat cells, Fig. 62.
• Reticular fibers.
• Many blood vessels.
Found into: rodents.
Fig. 62: Brown adipose tissue. 1. Nucleus. 2.
Lipid droplets.
4. Reticular connective tissue:
• Reticular fibers, Fig. 63.
• Reticular cells (similar to UMC).
Found into: spleen - liver.
Fig. 63: Reticular connective tissue 1. Reticular
fibers. 2. Reticular cells.
5. Embryonic connective tissue:
A) Mesenchymal c.t.:
• UMC, Fig. 64.
• Amorphous ground substance.
• Few fibroblasts.
Found into: the embryo.
Fig. 64: Mesenchymal connective tissue, Azan
stain.
B) Mucous c.t.:
• Fibroblasts (Fig. 65, arrowheads).
• Amorphous ground substance.
• Fine collagenous fibers.
Found into: umbilical cord.
Fig. 65: Mucous c. t. fibroblasts (arrowheads),
H & E.
II- Cartilage:
Formed of:
A) Cartilage cells:
1. Chondroblasts:
• Flat.
• Basophilic cytoplasm.
• Oval nucleus.
• Present into the perichondrium.
2. Chondrocytes:
• Oval - rounded - semicircular.
• Cytoplasm is granular with Golgi
apparatus + rER + Glycogen.
• Nucleus is rounded - vesicular.
• Located in lacunae surrounded by
capsules.
• May be found in groups (2 - 4 - 8
cells) = isogenous groups.
• Produce collagen and elastic fibers.
B) Intercellular substance:
a) Collagenous or elastic fibers.
b) Matrix = glycoprotein.
Perichondrium:
a) Outer fibrous layer.
b) Inner chondrogenic layer
(chondroblasts).
Types of cartilage:
1. Hyaline cartilage:
• Matrix: basophilic (chondroitin
sulphate), Fig. 66.
• Collagenous fibers (few).
Found into: larynx-trachea.
2. Elastic fibrocartilage:
• Network of elastic fibers (Fig. 67).
Found into: Ear pinna - epiglottis.
Fig. 66, A: Hyaline cartilage. 1. Perichondrium.
2. Chondrocyte (single). 3. Chondrocytes
(group). Inset: 1. Chondrocyte. 2. Lacuna. 3.
Capsule. 4. Matrix. B: Hyaline cartilage,
Trichrome stain.
Fig. 67: Elastic cartilage. Epiglottis. 1.
Perichondrium. 2. Chondrocyte single. 3.
Chondrocytes (isogenous group). 4. Elastic
fibers. B: Elastic cartilage, Resorcin-fuchsin
stain.
3. White fibrocartilage:
• Small groups of chrondrocytes
arranged into rows (Fig. 68).
• Bundles of Collagenous fibers.
• No perichondrium.
Found into: Intervertebral discs.
Fig: 68: White fibrocartilage. A: Intervertebral
disc. B: Light microscopic magnification. 1-
Chondrocytes. 2- Collagenous fibers. C: White
fibrocartilage, H&E
III- Bone:
Formed of
A) Bone cells:
1. Osteogenic cells:
• Similar to UMC.
2. Osteoblasts:
• Small – branched cells.
• Nucleus is oval, pale, eccentric.
• Basophilic cytoplasm.
• Found into periosteum and
endosteum (Fig.69).
Fig. 69: Osteoblasts. 1. Nucleus. 2. Cytoplasm.
3. Cytoplasmic processes
3. Osteocytes:
• Almond – shape cells (Fig. 70).
• Nucleus is elongated.
• Basophilic cytoplasm.
• Cytoplasmic processes.
• Located within lacunae - canaliculi.
• Produce bone matrix.
Fig. 70: Osteocytes. 1. Nucleus.2. Cytoplasm.
3. Lacuna. 4. Canaliculus.5. Cytoplasmic
processes.
4. Osteoclasts:
• Large - branched – motile cells.
• Multinucleated (5 - 50 nucleus),
Fig.71.
• Cytoplasm is acidophilic
(lysosomes).
• Found within grooves = Howship's
lacunae.
• Brush border = comb - shaped.
• Produce proteolytic enzymes.
Fig. 71: A: Osteoclast. 1. Microvillous
cytoplasmic processes. 2. Howship's lacunae. 3.
Belt of cytoplasm free of organelles 4.
Microvillous processes. Nuclei (arrows) B:
Osteoclast, H&E.
B) Matrix:
= Bone lamellae
Consist of collagenous fibers and
calcium salts.
Types of bones:
1. Cancellous bone (spongy bone):
Branched bone trabeculae = formed
of bony lamellae containing
osteocytes and are covered by
osteoblasts (Fig.72).
Found into: - Head of long bones.
- Ribs.
- Sternum.
Fig. 72: Cancellous bone (Spongy bone).
2. Compact bone:
Consists of:
a) Haversian system(s) = Osteon(s):
• Haversian canal (Bl. ves.).
• Haversian lamellae (concentrically
arranged).
• Osteocytes (concentrically
arranged).
b) Interstitial lamellae (non-
Haversian system).
c) Outer circumfrential lamellae.
d) Inner circumfrential lamellae.
Found into: Shaft of long bones ,
Fig.7 3.
Volkmann's canals:
Transverse canals between the
Haversian canals.
Periosteum and endosteum:
Consists of:
a) Outer fibrous layer.
b) Inner vascular layer.
(containing the osteoblast cells).
Fig. 73: Compact bone. 1. Periosteum. 2. Outer
circumferential lamellae. 3. Haversian system
(osteon). 4. Interstitial lamellae. 5. Medullary
cavity (marrow cavity). 6. Inner circumferential
lamellae. 7. Concentric bone lamellae. 8.
Haversian canal. 9. Osteocytes. 10. Volkmann's
canals
Ossification (development of bone):
1- Intramembranous ossification:
Occur within a membrane of
mesenchymal c.t. which is converted
into bone.
e.g. Flat bone of the skull.
2- Intracartilagenous ossification:
In this method cartilage is replaced
by bone.
e.g. epiphyseal plate of cartilage.
Stages: Fig. 74
I- Resting cartilage: A piece of
hyaline cartilage.
II- Zone of Proliferation: The
chondrocytes are increase in number
and arrange themselves into rows.
III- Zone of hypertrophy or
maturation: The chondrocytes
increase in size, accumulate glycogen
and become rich in phosphatase.
The lacuna also widen and become
separated by thin bars of matrix.
IV- Stage of calcification:
The chondrocytes deposit calcium
salts around themselves, die and
degenerate.
The lacunae open on each other
forming longitudinal canals.
V- Stage of ossification (stage of
invasion).
The osteoblasts deposit bone lamellae
on the calcified matrix.
VI- Stage of spongy bone.
Fig. 74: A& B. Intracartilagenous ossification; I- Resting cartilage. II- Zone of proliferation.
Ill- Zone of hypertrophy. IV- Stage of calcification. V- Stage of ossification. B: Azan stain.
BLOOD
Consists of:
65% blood plasma.
35% formed elements.
Formed elements:
I- Erythrocytes (Red blood
corpuscles):
A) Mammalian erythrocytes:
• Non-nucleated, rounded, biconcave
discs (Fig.75A.1 & B).
• Contain haemoglobin.
• Largest in dogs (7 mic.).
• Smallest in sheep (4 mic.).
In camel and llama (Tylopoda):
• Elliptical, non -nucleated
(Fig.75A.2).
B) Avian erythrocytes:
• Oval, biconvex, nucleated
(Fig.75A.3 & C).
C) Reptiles, Fish, Frog
erythrocytes:
• Ovoid, biconvex, nucleated.
II- Leukocytes (white blood cells):
1. Granular leukocytes:
"Granulocytes"
a) Neutrophil leukocytes:
= Polymorphonuclear leukocytes.
• Nucleus: 3-5 segments (Fig. 76).
• Neutrophilic cytoplasmic granules.
E/M:
• Large granules = lysosomes.
• Small granules = bacterial
substance.
Fig. 75: Red blood corpuscles: A.1& B-
Mammals. A.2- Tylopoda (camel and llama).
A.3& C- Birds.
Fig. 76: Neutrophil or polymorphonuclear
leukocyte. A: 1- Nucleus. 2- Large azurophilic
granules. 3- Small specific granules. 4-
Cytoplasmic arms. 5- Bacterium. 6- Phagocytic
vacuole. 7- Specific granule joining a
phagocytic vacuole.8-Pseudopodia. B: Blood
Film.
b) Eosinophil leukocytes:
See page 20.
c) Basophil leukocytes:
• Nucleus: bilobed (Fig. 77).
• Coarse basophilic cytoplasmic
granules.
E/M:
The cytoplasmic granules are
electron dense.
Fig. 77: Basophil leukocyte A: 1. Nucleus. 2.
Electron dense granules. 3. Cytoplasmic
organelles (Few). B: Blood film
2. Agranular leukocytes:
"Agranulocytes"
A) Lymphocytes:
a) Large lymphocytes: "Active"
• Large cells.
• Large indented nucleus.
• Abundant cytoplasm with numerous
ribosomes.
b) Small lymphocytes: "Inactive"
• Small rounded cells.
• Large rounded deeply stained
nucleus (Fig. 78).
• Few cytoplasm with few
azurophilic granules (lysosomes).
Fig. 78: Lymphocyte (Activated). A: 1-
Nucleus. 2- Mitochondria (Few). 3- Free
ribosomes. 4- rER (Few). 5- Centrioles. 6-
Azurophilic granules (lysosomes). B: Blood
film.
B) Monocytes
• Nucleus: Kidney – shaped (Fig. 79).
• Cytoplasm: Abundant - greyish blue
(numerous lysosomes).
• Highly phagocytic.
Fig. 79: Monocyte. A: 1- Nucleus. 2-
Centrioles. 3- Golgi apparatus. 4- Lysosomes.
5- Mitochondria. 6- Ribosomes. 7- rER. B:
Blood film.
Ill- Blood platelets:
"Thrombocytes"
In mammals:
• Non-nucleated cytoplasmic
fragments (Fig. 80).
E/M:
Contain:
• Alpha granules = Azurophilic
granules.
• Beta granules = Mitochondria.
• Delta granules = Vacuoles.
• Marginal zone = Microtubules.
In birds:
• They are nucleated.
• Simulate R. B. Cs.
Develop from Megakaryocytes
(Large cell with lobulated nucleus).
Fig. 80: Blood platelet. A: 1 - Mitochondria. 2-
Vacuoles. 3- Azurophilic granules 4-
Microtubules. B: Blood film.
THE MUSCULAR TISSUE
The muscular tissue performs
mechanical work by contraction.
1. The smooth muscle:
• Narrow, elongated and tapering
cells (Fig. 81).
• 20 - 500 μm X 5 μm.
• Sarcolemma: is not clear.
• Nucleus: Single, oval, central,
spiral chromatin.
• Sarcoplasm: - Myofibrils.
- Glycogen.
- Pigments (myoglobin).
• C.S.: Large nucleated and small
non-nucleated cytoplasmic portions.
Found into:
- Small intestine.
- Uterus.
- Blood vessels.
- Ureter.
- U. bladder.
Fig. 81: Smooth muscle fibers. A, Upper:
Longitudinal section. Middle: Longitudinal
section (left). Cross section (right). Lower: L.S. in
smooth muscle fiber: 1. Broad nucleus-containing
portion. 2. Myofibrils. B, Smooth muscle fibers
with H & E. Upper: L. S. Lower: C. S.
2. The skeletal muscle:
• Regular cylindrical cells (Fig. 82).
• 1 -300 mm X 10-100 μm.
• Sarcolemma: is clear.
• Nucleus: multiple, flat, and
peripheral.
• Sarcoplasm:
A) Cell organelles:
• Myofibrils.
• Sarcoplasmic reticulum = sER (SR)
• Mitochondria (2%).
• Golgi apparatus.
• Ribosomes.
B) Cell inclusions:
• Glycogen.
• Pigments (Myoglobin).
The muscle fiber is transversely
striated (clear).
Fig. 82: Skeletal muscle fibers. A: H & E.
Upper: L. S. Middle: C. S. Lower: L. S. B:
Azan stain. C: Types of skeletal muscle
fibers. (Stained for myosin ATPase) 1. Red
muscle fibers. 2. White muscle fibers. 3.
Intermediate muscle fibers.
Myofibrils:
L/M: Are transversely striated (Fig.
83):
1. A- band: Dark band
bisected by H - band.
2. I - band: Light band
bisected by Z - line
E/M: Each myofibril is composed of:
1. Thick myofilaments (Myosin)
2. Thin myofilaments (Actin)
• The segment between two successive
Z lines = Sarcomere.
• Sarcomere = A - band + ½ I- band
on either side.
C.S.: The muscle fiber is polygonal in
shape with peripheral, flat nuclei.
Fig. 83: A: Banding pattern of skeletal muscle B:
Relationship of cross banding to the arrangement
of thin and thick myofilaments C: Skeletal
muscle fibers (L. S.), Notice: I- Band, Z- Line, A-
Band.
Types of skeletal muscle fibers:
1. Red muscle fibers: small - rich
sarcoplasm - poor in glycogen (Fig.
82C.1).
2. White muscle fibers: large - poor
sarcoplasm - rich in glycogen (Fig.
82C.2).
3. Intermediate muscle fibers (Fig.
83C.3).
3. The cardiac muscle:
• Elongated branching cells (Fig.
84a ).
• Form networks (syncytium).
• 50-120X20 μm.
• Sarcolemma is thin.
• Nucleus: single, oval, central.
• Sarcoplasm: abundant.
• Striation: less clear.
• Glycogen and lipofuscin:
numerous.
• Sarcoplasmic reticulum: less
developed than in skeletal muscle.
• Mitochondria: 40%.
• The muscle fibers are joined to
each other by intercalated discs
(step - wise pattern), Fig. 84B& C.
C.S.: The muscle fibers are
polygonal in shape with or without
central rounded nucleus (Fig. 84b).
Fig. 84: Cardiac Muscle. A: a, L.S. b, C.S. of the
cardiac muscle: 1-Cardiac muscle fiber. 2-
Nucleus. 3- Endomysium.B: Intercalated disc. C:
Cardiac muscle (L.S.). Notice the intercalated
discs (Arrows).
THE NERVOUS TISSUE
The nervous tissue is adapted to
receive stimuli from the outside, to
transform them to nervous
impulses, and to convey these
stimuli to other parts of the body.
The nervous tissue consists of:
Nerve cells - Nerve fibers -
Neuroglia.
I- Nerve cells (Neurons):
Structure:
A) The cell body:
Shape: Rounded - oval – pear
shaped – pyramidal – irregular (Fig.
85).
Size: Large – Small.
a) Nucleus : Large - spherical - pale
- central - 1 to 2 nucleoli.
b) Ctyoplasm:
Organelles:
• rER = Nissl's granules.
• Golgi apparatus: surrounds the
nucleus.
• Mitochondria.
• Neurofibrils.
No centrioles (do not divide)
Inclusions:
• Pigments.
• Secretory granules.
B) The cell processes:
One or more
Short
Thick
Divide
rER
One
Long
Thin
Does not divide
No rER
Fig. 85: The nerve cell. A: 1. Cell body. 2.
Dendrites. 3. Axon. B: The nerve cell. 1. Nucleus.
2. Golgi apparatus. 3. Nissl's granules. 4.
Mitochondria. 5. Neurofibrils. C: Multipolar
neuron, Luxol Fast blue.
The nerve cells are found into:
• Gray matter of the brain and spinal
cord.
• Retina.
• Ear.
• Olfactory region.
Types of nerve cells:
1. Unipolar neurons : Embryo (Fig.
86A)
2. Pseudo - unipolar neurons: Spinal
ganglia (Fig. 86B)
3. Bipolar neurons: Retina (Fig.
86C) .
4. Multipolar neurons: Gray matter
(Fig. 86D).
Fig. 86: Types of nerve cells.
II- Nerve fibers:
A nerve fiber = Axon + its sheathes
(Fig. 87)
1. Axon:
• Axolemma.
• Axoplasm: Mitochondria.
Neurofilaments.
2. Sheathes:
A) Myelin sheath:
• Lipid.
• Segments.
• Nodes of Ranvier.
B) Neurolemma: Schwann's cells:
Flat - one for each segment.
Type of nerve fibers:
1. Myelinated with neurolemma :
Spinal nerve.
2. Myelinated without neurolemma:
Optic nerve.
3. Unmyelinated with neurolemma:
Sympathetic nerve.
4. Unmyelinated without neurolemma:
Olfactory nerve.
Fig. 87: A, Myelinated nerve fiber with
neurolemma: 1- Axon. 2- Axolemma. 3- Myelin
sheath. 4- neurolemma. 5- Endoneurim. 6- Node
of Ranvier. 7 - Clefts of Schmidt - Lanterman. 8 -
Nucleus of Schwann cell. 9 - Mitochondria. 10-
Neurokeratin network. 11- Neurofilaments. B,
Myelinated nerve fibers (L. S.), Silver
impregnation.
Synapse (s):
- The connection between:
• neuron neuron.
• neuron muscle.
• neuron gland.
- Conduction of nerve impulses
occurs in one direction only.
- There is no actual continuity of
substance between the cells.
- Synapses are electrochemical
transmission sites.
Structure:
- Cell processes (e.g. axon) provide
synaptic end-bulb (boutons
terminaux), Fig. 88.
- The synaptic end-bulb contains
synaptic vesicles which contain the
Neuro-transmitter substance which
passes through
- The presynaptic membrane to
- The synaptic cleft to form
- The postsynaptic components
which pass through
- The post synaptic membrane.
Types: (Fig. 89).
1- Somato – somatic.
2- Dendro – dendretic.
3- Axo – axonic.
4- Axo – dendretic.
5- Dendro – somatic.
6- Axo – somatic.
Fig. 88: A synapse: 1- Nerve cell process
(presynaptic component). 2- Synaptic end - bulb.
3- Mitochondria. 4- Synaptic vesicles. 5-
Presynaptic membrane. 6- Synaptic cleft. 7-
Postsynaptic component of nerve cell process, 8-
Postsynaptic membrane.
Fig. 89: Types of synaptic patterns: 1- Somato-
somatic synapse. 2-Dendro- dendritic synapse. 3
- Axo- axonic synapse. 4- Axo- dendritic synapse.
5- Dentro- somatic synapse. 6- Axo- somatic
synapse.
Nerve trunk:
• Epineurium: surrounds the whole
nerve (Fig. 90).
• Perineurium: surrounds the nerve
bundle (Fig.91).
• Endoneurium: surrounds the nerve
fiber.
Fig. 90: Nerve trunk (Spinal nerve). A)
Whole nerve trunk. 1. Nerve bundle. 2. Nerve
fibers. 3. Perineurium. 4. Endoneurium. 5.
Perineurium. 6. Epineurium. 7. Blood vessels.
8. Adipose tissue. B) L.S. 1. Nerve fiber. 2.
Axon. 3. Myelin sheath. 4. Node of Ranvier.
5. Endoneurium. c) C.S. 1. Perineurium. 2.
Epineurium. 3. Nerve fibers. 4. Endoneurium.
5. Blood capillaries. 6. Axon.7. Myelin
sheath.
Fig. 91: Nerve bundle (C. S.), Silver
impregnation. 1. Axon. 2. Myelin sheath.
Ganglia:
A ganglion is a collection of nerve
cells and nerve fibers.
* Small
*Multipolar
*Singly
scattered
*Surrounded by
satellites in an
irregular
manner.
*Unmyelinated
with neurolemma
Fig. 92
*Large
*Pseudounipolar
*In groups
*Surrounded by
satellites in a
regular manner.
*Myelinated with
neurolemma.
Fig. 93
Fig.92: Section from a sympathetic ganglion of
the horse, showing the multipolar neurons (a)
surrounded by a less apparent layer of satellites
(b). Notice the sympathetic unmyelinated nerve
fibers (c).
Fig. 93. A: Section from the spinal ganglion
of a horse. a) Nerve cell (in groups). b) Single
layer of satellite cells or capsule cells
surrounding the nerve cells. B: Group of
pseudounipolar neurons within a spinal
ganglion. C: Pseudounipolar neurons
surrounded by satellite cells (arrowheads)
within a spinal ganglion.
III- NeurogIia:
Fig. 94
Connective tissue of CNS
A- Neuroglia proper :
1-Astrocytes:
a- Protoplasmic astrocytes (Fig.
94A & 95):
• Large cells.
• Numerous, thick, short and
branching cytoplasmic processes.
These processes form perivascular
feet.
• Numerous cytoplasmic granules
(gliosomes).
• Central, large, rounded nucleus.
• Found into the gray matter.
Fig. 94: Neuroglia. A- Protoplasmic astrocyte. B-
Fibrous astrocyte. C- Oligodendrocyte. D-
Microglia.
Fig. 95: Protoplasmic astrocytes, Silver
impregnation.
b- Fibrous astrocytes: (Fig. 94B& 96)
• Large cells.
• The cytoplasmic processes are long,
thin, straight and less branched.
These processes form perivascular
feet.
• The cytoplasm is not granular.
• Central,large ,rounded nucleus.
• Found into the white matter.
Fig.96: Fiberous astrocytes.
2- Oligodendrocytes:
• Small cells (Fig. 94C & 97).
• The cytoplasmic processes are
few, short and less branched.
• Small, rounded dark nucleus.
• Found into both gray and white
matters.
Fig. 97: Oligodendrocytes.
3-Microglia
=Mesoglia=Microphage:
• Small cells.
• Spindle shaped.
• The cytoplasmic processes are thin,
branched and arise from each of the
two poles of the cell (Fig. 94D & 98).
• Little thorns cover the cell and its
processes.
• Flat, oval, dark nucleus.
• Motile and phagocytic cells.
Fig. 98: Microglia cells, Hortega stain.
B- Other types of neuroglia:
a) Spongioblasts:
They are small cells with deeply
stained nucleus. They are capable of
differentiation into astrocytes and
oligodentrocytes.
b) Ependymal cells:
They are simple columnar ciliated
cells, which line the central canal of
the spinal cord.
c) Capsule (or satellite) cells:
They surround the neurons of the
ganglia (Fig. 93C).
d) Cells of Schwann:
They surround the peripheral nerve
fibers (axons), Fig. 87A.
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Applied Veterinary Histology
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Banks, W. J. (1993): Applied Veterinary Histology. Third edition, Mosby Year book. Inc. St.
Hewer's textbook of histology for medical students. Ninth edition. The English Language Book Society and William Heinemann medical books LTD
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Source: https://www.researchgate.net/publication/320431791_Histology
