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Connective Tissue
LiDongMei
[email protected]
1. Introduction

Connective tissue is versatile，the types including
Connective Tissue proper and the specialized
Cartilage ，Bone and Blood.

Connective tissue comprises a diverse group of
cells embedded in a tissue-specific extracellular
matrix（ECM）.
1.1 Classification

Connective Tissue proper
Loose connective tissue ※
Dense connective tissue
Adipose tissue
Reticular tissue
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Cartilage ※
Bone ※
Blood ※
1.2 Component
Cell
Connective
tissue
amorphous Ground
substance
Extracellular
matrix（ECM）
Fiber
1.3 Characteristics
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Have small number of cells but have much
extracellular matrix.
all of them originate from mesenchymeembryonic CT
have functions of connection, supporting,
protecting, nutrition, defence and repairing
mesenchymal cell
structure:
1)stellate in shaped with processes
2)a large nucleus,with clear nucleoles
3)slight basophilic cytoplasm
function:
1) undifferentiated cell
2) multiple developmental potential
1.4 Functions

have functions of connection, supporting,
protecting, nutrition, defence and repairing
2. Connective tissue proper
Loose(areolar) connective tissue※
Dense connective tissue
Adipose tissue
Reticular tissue
2.1 Loose connective tissue
1) functions: connection,
supporting, defence and repairing
2）consists of 7 types of cells, 3
types of fiber and ground
substance
2.1.1 Cells in loose connective tissue
there are 7 types of cells present in LCT
Fibroblast※
Macrophage※
Plasma cell
Mast cell
Fat cell
undifferentiated mesenchymal cell
Leukocytes
※
① fibroblast
---structure:
LM:
•large,flattened cell in shaped
•Large ovoid pale nucleus
with clear one-two nucleoli
•Weakly basophilic
EM:
 rich in RER, Golgi complex
and free ribosome
---function: synthesize fibers
and ground substance
Synthesis of collagenous fiber in three steps:
a. synthesis of procollagen (RER) → process
(Golgi) → procollagen → out of cell
b. procollagen→ tropocollagen → fibril
c. fibril → collagenous fiber
*fibrocyte: still state or inactive fibroblast
---structure:
• spindle-shaped, small
• N:small,dark stained
• Acidophilic cytoplasma
• EM: less organelles
---function: become into fibroblast for
repairing
②macrophage
（The mononuclear
phagocyte system）
---structure:
LM:
 round or ovoid-irregular in shape
 Small and dark nucleus
 Acidophilic cytoplasm
EM: rich in
 a. lysosome
 b. Phagosome
 c. Remnant
Function:
a. Phagocytosis:
 Special phagocytosis: recognize
Bacterium, virus and foreign cell
 Non special: carbon particles, dust and
dead cells
B. secretion: cytokines, growth factors and
complement protein.
C. antigen presenting function:
*capture antigen→processes→+ MHC II
molecule (major histocompatibility complex
molecules) →antigen-MHC II complexes→T
lymphocytes
The mononuclear phagocyte system
Monocyte in blood is the precursor of macrophages
Liver: Kupffer cells
 Central nervous system: microglial cells
 Skin: Langhans cells
 Lymph node: dendritic cells
 Bone: osteoclast

Langhans cell
③plasma cell
---derive from
B lymphocyte
---structure:
LM:
round or ovoid
Round eccentrically-located nucleus with
more spot-liked heterochromatin
Basophilic cytoplasm
EM: rich in parallelly arranged RER, free
ribosome and Golgi complex
---function: synthesize and secrete
antibody（immunoglobulin）
④mast cell
---structure:
LM:
round and large cell
Small dark-stained nucleus
Basophilic secreting granules
EM
Membrane bound granules
A few Mitochondria
A little RER
function:
cause allergic reaction
⑤fat cells (adipose cells)
---structure:
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large, round or polygonal
flattened ovoid nucleus
located on one side of cell
thin layer of cytoplasm
a large lipid droplet
--- function: synthesize and
store fat
⑥undifferentiated mesenchymal cell
---structure:similar to fibrocyte
---function: multidifferentiating potential
⑦leukocytes:
Granulocyte: neutrophil, eosinophil and
basophil
Agranulocyte: lymphocyte (B, T)
monocyte
Myofibroblasts, Pigment cells
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summary
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A. Classification of CT
B. 7 types of cell in LCT
1. fibroblast
2. macrophage
3. plasma
4. mast cell
5. fat cell
6. undifferentiated mesenchymal cells
7. leukocyte
Questions:
• 1. What kind of cells present in loose
connective tissue? And what are the
functions of those cells?
• 2. What is (are) the structure cell(s) of
connective?
2.1.2 fibers
Collagenous fiber
Elastic fiber
Reticular fiber
Collagenous
fiber(white fiber)
LM:
 1-20 um in diameter
 Belt-liked wave and
branch to form a
network
 Acidophilic
are inelastic and have great
tensile strength
EM: parallel-arranged fibrils
Fibril:
 20-200nm in diameter
 formation: Extracellular polymerize
collagen molecule (type I and III) →collagenous fibril →
collagenous fiber
elastic fiber
(yellow fiber)
LM:
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thinner and less
Slight red(HE), purple or blue(special stained)
Branch and form a network
EM：
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core: elastin
Peripheral: microfibril
reticular fiber
LM:
 thin and less,0.2-1.0 um in diameter
 Branch to form network
 black (silver impregnation method)
---distribution:
 reticular tissue
 connecting portion, e.g.reticular lamina
2.1.3 ground substance
---amorphous colloidal substance
---consists of proteoglycan, glycoprotein
and tissue fluid
Function of the ground substance
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Connection
affect the differentiation and movement
of cells
a barrier to the penetration of foreign
particles
Summary
Loose connective Tissue
3 fibers and 7 kinds of cells

2.2 Dense connective tissue
---Abundant fibers and few cells
---connection and supporting
Dense regular CT; Dense irregular CT;Elastic CT
2.2.1 regular DCT:
 parallelly-arranged collagenous fibers
 tendon cells: /special fibroblast
/wing-liked processes
distribution:
tendons, ligament and
cornea
2.2.2 irregular DCT:
 Fiber arranged in bundles,runing in different
direction
 Fibroblast
 less ground substance
---distribution: dermis, sclera and capsule of
some organs
2.2.3 Elastic Tissue:
 elastic fiber in bundles or in membrane
 ligament and large artery
2.3 adipose tissue
---LCT+fat cells
---white fat T:
 single fat cell
---brown fat T:
 fat cell contain many small lipid droplets,
 rich in large mitochondria
 centrally-located nucleus
2.4 reticular tissue
components:
Reticular cells
reticular fibers
ground substance
distribution:
hemopoietic tissue
lymphatic tissue