HISTOLOGY OF CONNECTIVE TISSUE IN ANATOMY

1. BY
DR. UCHENNA STEPHEN
AYOGU , MBBS, Msc.
1
HISTOLOGY OF
CONNECTIVE TISSUE

2. LEARNING
OBJECTIVES:
1.To understand the characteristics that define
connective tissue and the common features of
connective tissue.
2.To understand the major functions of connective
tissue.
3.To define the cell types that form connective tissue.
4.To define the cells types that, although they do not
form connective tissue, migrate into the connective
tissue.

3. LEARNING
OBJECTIVES CONT,D
 To define the different types of connective tissue
including: mesenchyme, adipose tissue, loose
connective tissue, dense regular connective tissue
and dense irregular connective tissue, and to be able
to recognize these in a micrograph.
 To understand the components of the extracellular
matrix in connective tissue, including the various
fibres present and the components of ground
substance.
 Clinical correlate of connective tissue disorders.

4. CONNECTIVE TISSUE
4
 Unlike the other major
tissues (e.g. epithelia) that
are made up mainly of cells,
with relatively little
extracellular space,
connective tissue consists of
cells embedded in large
quantities of extracellular
matrix.
 This extracellular matrix is
composed of protein fibres,
amorphous ground
substance and tissue fluid.

5. FUNCTIONS OF CONNECTIVE
TISSUE
5
1. Space filler and mechanical support.
2. Attachment and protection
3. Highway for nutrients
4. Main fat store and calcium store
5. Site of many immunological defence
reactions

6. 6
CONNECTIVE TISSUE
 Subdivided into three types:
1. Soft connective tissue: Tendons, ligaments,
mesentery, stroma of organs,
dermis of the skin, etc
2. Hard connective tissue: Bone and cartilage
3. Blood and lymph: many authors consider
blood and lymph as a specialized form
of connective tissue

7. CONNECTIVE TISSUE
 Consists of:
 Cells:
 Extracellular matrix:
 The type of connective tissue is determined by the types
and relative amounts of these two components.

8. CELLS PRESENT IN CONNECTIVE
TISSUE
8
 Resident Cells of
Connective Tissue:
• Fibroblasts
• Adipose cells
• Osteocytes: cells of
bone
• Chondrocytes: cells of
cartilage
 We will deal with osteocytes and
chondrocytes in future lectures
 Immigrant cells of
Connective
Tissue:
 Lymphocytes
 Leukocytes
 Mast cells
 Macrophages

9. FIBROBLASTS
9
 Fibroblasts:
elongated cells with
tapered ends that are
widely distributed and
that produce and
maintain the
extracellular matrix.
Tissue damage
causes fibroblasts to
divide and they are
very important in
wound repair.
 Notice the prominent
rough endopasmic
reticulum (rER) and
Golgi apparatus (G)
typical of a protein

10. ACTIVE FIBROBLASTS
10
Note the enlarged
prominent nucleus.
These are plastic
sections: in the
more commonly
seen paraffin
sections stained with
H&E it is very
difficult to
differentiate between
the fibroblast
cytoplasm and the

11. ADIPOSE CELLS
11
Adipose cells (fat cells):
In adults these cells have a
single giant fat droplet and
with the release of fatty
acids into the bloodstream
provide energy for other
cells.
Adipocytes (another
name for adipose cell) are
found scattered in many
connective tissues, but are
the predominant cell by far
in adipose tissue (fat).
This type of tissue is also
called‘white fat’ or unilocular

12. ADIPOSE CELLS: BROWN FAT
12
Brown fat is a special type of
fat that in humans occurs
mostly in the fetus and
neonate.
Cells in brown fat contain many
small fat droplets and very
numerous mitochondria.
When brown fat is oxidized, rather
than producing ATP, a large
amount of heat is generated
which helps keep the infant
warm.
This is called ‘non-shivering
thermogenesis’.
Brown fat is also called
multilocular fat.

13. ADIPOSE TISSUE
 Adipose tissue is the largest store of energy in
the body.
 It is in a continuous state of turnover and is
sensitive to both hormonal and nervous
stimuli.
 Subcutaneous layers of adipose tissue help to
shape the body, while deposits in the form of
pads act as shock absorbers, e.g. soles of feet
& palms.
 Elsewhere it fills up the spaces between
tissues and helps to keep some tissues in
position.

14. Cells Present in Connective Tissue
Cells you might see in Connective Tissue:
• During wound healing a type of cell
with properties intermediate between a
fibroblast
• And a smooth muscle cell can be
found called a myofibroblast.
• Myofibroblasts cause wound
contraction by producing collagen
fibres
• And tugging on them to draw together

15. Cells Present in Connective Tissue
Cont,d
Immigrant cells:
• Leukocytes (white blood cells):
• Lymphocytes, plasma cells, granulocytes
and macrophages are commonly found in
loose connective tissue.
• These migrate from the blood stream.
• The number of these cells increases
dramatically at sites of inflammation or
infection

16. Immigrant cells Found In
Connective Tissue Cont,d
Mast cells:
 Probably originate from a type of
leukocyte
 They contain granules of heparin,
histamine
 And substances that stimulate
inflammation and attract white blood

17. Immigrant cells Found In Connective
Tissue Cont,d
Leukocytes
 These migrate from the blood.
 1. Neutrophils leave the blood stream in response to
infection.
 2. Eosinophils are found in increased number during
allergic reactions and parasitic diseases.

18. Immigrant cells Found In
Connective Tissue Cont,d
Macrophages
 Derived from monocytes in the bone marrow
 And circulate in the blood before migrating into the
connective tissue where they rapidly transform into
macrophages.
 They can proliferate locally.
 They are phagocytic cells that have a body-wide
distribution
 And live for several months. 10-30 µm in diameter.

19. Immigrant cells Found In
Connective Tissue

20. Immigrant Cells found in Connective Tissue
Mast Cells
Mast cells are the largest of the cells in the connective tissue
(20-30µm diameter) (except for adipocytes) and are widely
dispersed. Basophilic granules containing heparin (an
anticoagulant) fill the cytoplasm. Histamine is also present,
which increases the permeability of small blood vessels and,
in airways, causes increased mucous production and smooth
muscle contraction. Mast cells are sensitive to foreign
proteins and rapidly release their contents when these are
detected.
They are the cells which react in hay fever and asthma.
Mast cells share many characteristics with a type of leukocyte
(white blood cell) called a basophil.

21. Immigrant Cells found in Connective
Tissue

22. Immigrant Cells found in Connective
Tissue

23. Immigrant Cells found in Connective
Tissue

24. Extracellular Matrix of Connective
Tissue
 Extracellular matrix:
 Consisting of Fibres:
 Collagen, Reticular and Elastic fibres
 Ground substance: an amorphous, space
occupying material made of huge
unbranched polysaccharide molecules
called glycosaminoglycan (GAGs), most of
which are bound to protein cores to form
glycoproteins

25. COLLAGEN
 The most abundant protein in the human body
constituting 30-40% of the protein in the body.
 Collagen is synthesised in the fibroblasts and is
formed from three polypeptide chains. Collagen
molecules are approximately 300nm long and have
striations every 68nm.
 Collagen fibrils are inelastic and the most common
form (type I) has a tensile strength (on a weight for
weight basis) similar to mild steel, giving a tissue
which is both flexible and strong.

26. COLLAGEN FIBRILS

27. Reticular Fibres
 Reticular fibres are
thin fibres, made of a
special type of
collagen (Type III), that
forms a support
network in many
organs (indeed, the
word ‘reticular’ comes
from reticulum which is
Latin for a net).
 Reticular fibres form
the supporting
scaffolding in organs

28. Elastic Fibres
 Elastic fibres provide
elasticity to tissue.
 Elastic fibres are made up
of the proteins elastin
(which is a rubber-band-
like molecule) and the
microfibril, fibrillin and
forms random coils.
 Cross-links between
elastin molecules results
in an elastic array of
fibres.
 Elastic fibres are present,
for example in blood
vessels providing elastic
support and giving them
recoil.

29. Elastic Fibres Cont,d

30. Glycosaminoglycans
 Glycosaminoglycans (GAGs) are linear(unbranched)
polysaccharides formed by characteristic repeating
disaccharide units.
 With the exception of hyaluronic acid, these linear chains are
bound covalently to a protein core, forming a proteoglycan
molecule.
 This is a three dimensional structure resembling a test tube
brush, with the wire stem representing the protein core and
the bristles representing the GAGs.
 Gags help to give turgor and determine the diffusion of
substances through the extracellular matrix

31. Proteoglycans
 They are intensely hydrophilic due to the presence of
hydroxyl, carboxyl and sulphate groups in the
carbohydrate moiety of the proteoglycans and are
therefore intensely hydrated structures with a thick
layer of solvation water surrounding the molecule.
 The main proteoglycans are composed of a core of
protein associated with GAGS.
 Therefore proteoglycans trap water and act
somewhat like a sponge.
 This makes the structure resistant to compression if
distorted and much of the elasticity of cartilage is due
to this capacity of proteoglycans to absorb and hold
water.

32. Structural Glycoproteins
 These compounds can bind molecules on the surface of cells
as well as extracellular matrix components (e.g. collagen) and
so help establish structural continuity between the
cytoskeleton and the extracellular matrix.
 The most common are listed below:
 1. Fibronectin: can also bind ECM to ECM
 2. Laminin: found in basal lamina
 3. Chondronectin: found in cartilage

33. TYPES OF SOFT
CONNECTIVE TISSUE

34. MESENCHYME
 Mesenchyme is an
embryonic
connective tissue
that differentiates
into cells that
become fibroblasts,
chondrocytes,
adipocytes and
osteocytes (also
muscle). Cells with
this capacity persist
at various sites in
the body.

35. Types of Soft Connective Tissue: Loose

36. Types of Soft Connective
Tissue: Loose

37. Types of Soft Connective
Tissue: Dense

38. DENSE IRREGULAR CONNECTIVE
TISSUE

39. DENSE REGULAR CONNECTIVE
TISSUE

40. CLINICAL CORRELATE
Of connective tissue disorders
 SYSTEMIC LUPUS
ERYTHEMATOSUS (SLE)
 This is a systemic
autoimmune disease of
connective tissue which
leads to inflammation of
several organs.
 It affects organs like the
heart, joints, skin, lungs,
blood vessels and nervous
system.
 Lupus is characterized by
the presence of antibodies
directed against a persons

41. MARFANS SYNDROME
 This is a genetic disorder
caused by the misfolding
of fibrillin-1.
 It has a variable clinical
presentation ranging
from mild to severe
systemic disease.
 The most serious
manifestatation involve
defects of the heart
valves and aorta.