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1. Connective tissue fibres
and types of the
connective tissue
Viktória Vereczki MD.,PhD.
Semmelweis Egyetem
Anatómiai, Szövet- és Fejlődéstani Intézet
5/10/2018 8:55 am

2.  Connective tissue cells
 Extracellular matrix
 fibres
 collagen
 reticular
 elastic
 amorphous background substance
 glycosaminoglycans: unbranched polysaccharides made up of
repeating disaccharides
 proteoglycans: a core protein is equipped with numerous GAG
molecules
 glycoproteins: globular proteins with branching chains of
monosaccharids
Basic concept of the connective tissue

3. Connective
tissues:
properties are
basicly
determined by
the extracellular
matrix (ECM).

4. Basic concept of the connective tissue
 Connective tissue cells
 Extracellular matrix
 fibres
 collagen
 reticular
 elastic
 amorphous background substance
 glycosaminoglycans
 proteoglycans
 glycoproteins
 electrolyte (water, salts)

5. Connective tissue fibres
collagen fibres elastic fibres
reticular fibres
Collagen and reticular fibres are the polimers of the collagen molecule, while elastic
fibres are formed by elastin and microfibrils .
from Dr. Puskár

6. Synthesis and structure of
collagen and elastin

7. procollagen alpha-chain
procollagen triple helix
cleavage by procollagen peptidase:
insoluble tropocollagen
Tropocollagene
Collagen
synthesis
glycine, proline, hydroxy-proline, hydroxy-lysine

8. Medical application: Keloid
Keloid is a local swelling caused by abnormally large amount of
collagen that form is scars of the skin. Keloids occur most often in
individuals of African descent. Not only they can be disfiguring but
excision is almost always followed by recurrence.

9.  Collagen types
Fibrillar collagens linking/anchoring collagens sheet-forming-collagens
Type I, II, III, V, XI TypeIX, XII or VII binds to type IV Type IV

10. Tropocollagen
covalent cross-links by lysyl oxidase enzyme: collagen fibrils (cross-striation)
collagen fibers
collagen bundles
Constitution of fibrillar collagen

11. • Collagen I: everywhere, 90% of total collagen in the body:skin, tendon,
bone, dentin
• Collagen II: main component of cartilage
• Collagen III: main component of reticular fibers
• Collagen IV: in the basement membrane (within the basal lamina)
• Collagen V: hair and placenta
Instead of getting lost in the details and the charts of the
histology textbooks... What you really have to know:
Note that type I, II, III and V are fibril-forming, while type IV
forms delicate networks!

12. Elastin synthesis
glycine, proline, lysine,
alanine, valine (hydrophobic
side-chains and are responsible
for elasticity.
Resambles collagen synthesis: water soluble proelastin is synthesized in the rER,
secreted into the extracellular space where it is cleaved by proelastin peptidase to form
insoluble tropoelastin. Tropoelastin combines with microfibrills and is cross-linked
into mature fibres by lysyl oxidase.

13. Elastin polipeptides , the major components of elastic fibers have multiple
random-coil domains that strenghten or strech under force, and then relax. Most
of the cross-links between elastin subunits consist of the covalent, cyclic
structure desmosine, each of which involves four converted lysisns into elastine
molecules.

14. Medical application
Mutation of fibrillin genes results in Marfan syndrome :lack of resistance in tissues rich in elastin
fibers.
The degree to which people are affected varies. People with Marfan tend to be tall, and thin, with
long arms, legs, fingers, and toes. They also typically have flexible joints and scoliosis, The most
serious complications involve the heart and aorta with an increased risk of mitral valve
prolapse and aortic aneurysm.

15. Basic histological properties of
connective tissue fibers
or how to recognize them in the histology lab...

16. Collagen fibers
Collagen is the most common type of fibers in the ECM and the only clearly
visible fiber when HE staining is used!

17. Reticular fibers
Form delicate branching network and contribute to the inner skeleton of all
parenchymal organs. They are of small diameter and resistant to most of the dyes.
Silver impregnation is commonly used to make them visible (argyrophil fibres).

18. Elastic fibers
Thin wavy fibres frequenty aggragating into thick elastic membranes.
Bind resorcin-fuchsin.

19. Note: each connective tissue fiber type
requires different staining method!
collagen fibres
(HE)
elastic fibres
(resorcin-fuchsin)
reticular fibres
(silver-impregnation)

20. Basic concept of the connective tissue
 Connective tissue cells
 Extracellular matrix
 fibres
 collagen
 reticular
 elastic
 amorphous background substance
 glycosaminoglycans: unbranched polysaccharides made up of
repeating disaccharides
 proteoglycans: a core protein is equipped with numerous GAG
molecules
 glycoproteins: globular proteins with branching chains of
monosaccharids

21. Glucosaminoglycans (GAGs) or
mucopolisaccharides
hexuronic acid or hexose
glucuronic acid, iduronic acid, galactose
hexosamine
glucosamine, galactosamine
COOH/CH2OH
O
CH2OH
O
NH2
-O -
S
S S
S
S S
S
S S
S
S S
S
S S
COOH/CH2OH
O
-OH
CH2OH
O
NH2
HO-
monomer

22.  Hyaluronic acid: the largest (100 to 1000 kDa) and the only non-sulphated
GAG.
 Chondroitin 4-sulphate
 Chondroitin 6-sulphate
 Dermatan sulphate
 Heparan sulphate
 Keratan sulphate
smaller (10to 40 kDa) GAGs covalently
bound to proteins to form proteoglycans
All the GAGs are intensly hydrophilic and bind a lot of water being responsible
for the high viscosity of the ground substance. GAGs are also polyanions binding
a great number of cations, mainly sodium ions.

23. Proteoglycans in the ECM
AGGRECAN
monomer
Acidic groups of proteoglycans bind to the basic groups of
collagen.

24. Glycoproteins
Fibronectin and laminin: multiadhesive glycoproteins connecting cells
through their surface integrin moleculeswith the extracellular matrix
structures. Support adhesion and migration.
Glycoprotein

25. Summary of the ECM
 In contrast to the epithelial tissues, the extracellular space of the connective
tissues is abundant and basicly determins the properties of the connective
tissues.
 Glycosaminoglycans and proteoglycans due to their highly hydrophilic
character and sugar content bind a lot of water providing high viscosity, a
jelly-like consistance to the ground substance. This gelatinous substance is
structured and fixed by the connective tissue fibres.
 Mainly glycoproteins are responsible for linking connective tissue cells to the
ECM. These cells might be involved in synthesis of ECM (e.g. fibroblast,
osteoblasts) or protect ECM from the invasion of infective agents (immune
cells) or contribute to the renewal/remodelling/transformation of the
connective tissue (macrophages, chondroclast, osteoclasts).

26. 1. Embryonic connective tissue (umbilical cord)
2. Loose connective tissue (submucosa, adventitia)
3. Dense connective tissue
irregular (dermis, tunica albuginea, capsules of organs)
regular (ligaments, tendons, cornea)
4. Cell rich connective tissue
reticular (hemopoetic and lymphatic tissues)
spinocellular (ovarium, uterus)
5. Specialized connective tissues
blood
adipose tissue
bone
cartilage
Classification of connective tissues
supporting tissues

27. 1. Embryonic connective tissue
Mesenchymal cells (undifferentiated
connective tissue cells) and hyaluronic
acid predominantly in the early stage.
Later mesenchymal cells differentiate
into fibroblast which produce more and
more fibres, but the amorphous ground
substance remains abundant resulting in
a jelly-like consistence (Wharton jelly).
Basophilic staining of the mesenchymal
cells and fibroblast can be explained by
intense protein synthesis and well-
developed rER. T is also called as
mucoid tissue. It is aslo found in the
pulp cavities of young teeth as a
postnatal source of mesenhymal stem
cells.
from Dr. Puskár

28. 2. Loose connective tissue
The most common type of
connective tissues: connects and
separates, fills the gaps everywhere,
i.e. tunica adventitia of the vessels
and tubular organs; tela
submucosa.

29. 3a. Dense, irregular connective tissue
Rich in collagen (type I and
elastic fibers), no preferred
orientation. (e.g. dermis of the
skin, tunica albuginea of the
testicles)

30. 3b. Dense, regular connective tissue
Paralelly arranged bundles of collagen and tendocytes (a special type of
fibrocytes).

31. 4a. Cell rich connective tissue - reticular
reticulum cells and reticular
fibres (type III collagen)
tonsil
spleen

32. Ag-impregnation: reticular fibres in the lymph node.

33. Star-shaped, fibroblast-like reticulum cell in a lymphatic organ.

34. 4b. Cell rich connective tissue -
spinocellular
ovary
uterus

35. 1. Embryonic connective tissue
2. Loose connective tissue (submucosa, adventitia)
3. Dense connective tissue
irregular (dermis, tunica albuginea, capsules of organs)
regular (ligaments, tendons, cornea)
4. Cell rich connective tissue
reticular (hemopoetic and lymphatic tissues)
spinocellular (ovarium, uterus)
5. Specialized connective tissues
blood
adipose tissue
bone
cartilage
Classification of connective tissues
supporting tissues –

36. "Empty" signet ring cells.
Energy storage, thermal
insulation, thermogenezis in
brown adipose tissue, shock
absorbtion,, endocrine functions
(e.g. leptin)
signet ring cells - adipocytes
Adipose tissue

37. unilocular, white adipocytes multilocular, brown adipocytes
unilocular and multilocular cells frozen section, Sudan III staining

38. Thank you for your
attention!

39. References
Ross et al: Histology a text and Atlas, 3rd ed. 1995
Junqueira’a Basic Histology text and Atlas 13th ed.
2013
Dr. Márk Kozsurek’s lecture about Connective tissue
fibres
Prof. Mihály Kálmán’s lecture about Connective tissue
fibres
Szentagothai J, Réthelyi M: Funkcionális anatómia,
Medicina, 2014