Prof. Hong CHEN, MD, PhD - fdjpkc.fudan.edu.cn

Connective Tissue

Prof. Hong CHEN, MD, PhD

Office: Room 304, Building 9 East

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http://jpkc.fudan.edu.cn/s/426/main.htm

mailto:[email protected]

mailto:[email protected]

http://jpkc.fudan.edu.cn/s/426/main.htm

Review: Tissues• Made of two interacting

components: – Cells

– Extracellular matrix (ECM)

★ Continuum: functions & reacts to stimuli and inhibitors together

• Four basic types of tissue:

★ cell-specific associations

– Epithelial Tissue

– Connective Tissue

– Muscle Tissue

– Nerve Tissue

Prof. Hong CHEN, Shanghai Med. College, Fudan Univ. 2

Review: Characteristics of Epithelia

• A sheetlike structure surrounding “free”

surfaces of body or cavity.

• More cells bound tightly together

structurally and functionally with little ECM.

• Polarity：Apical, Basal

• Rest on basement membrane underlying

connective tissue

• No blood vessels, rich nerve endings

• Functions：protecting surfaces,

absorption or transcytosis, secretion,

contractility, sensory.

Prof. Hong CHEN, Shanghai Med. College, Fudan Univ. 3

Microvilli

QUIZ 1 for Introduction & Epithelia

Prof. Hong CHEN, Shanghai Med. College, Fudan Univ.

General Characteristics of Connective

Tissue (CT)

• Few cells, more ECM.

• No polarity, inside located in

the body as its inner

environment

• Rich in blood and lymph

vessels, nerves.

• Originated from mesenchyme

• Supply a matrix for

connection, support,

nutrients, protection, etc.


Embryonic Mesenchyme • An embryonic tissue from

mesoderm

• Formed by elongated

undifferentiated cells, called

MESENCHYMAL CELLS

– Many thin cytoplasmic process

– Oval nuclei with prominent

nucleoli and fine chromatin

• More viscous ground

substances (hyaluronan) with

few collagen fibers

• Have the multi-potentials in

differentiation


Differentiation of Mesenchymal Cells

√

√


Mucous Tissue

• Mainly in the

umbilical cord and

fetal tissue

• Jellylike tissue, as

Wharton’s jelly

– Rich in hyaluronic

acid

– Few cells or fibers


Classification of CT

• Embryonic Connective Tissues:

Mesenchyme, Mucous CT

• Connective tissue proper：

Loose CT

Dense irregular/regular CT

• Specialized Connective Tissue:

Adipose tissue

Reticular tissue

Cartilage, Bone, Blood


Composition of Connective Tissue

---- Cells, ECM (Fibers, Ground Substances)


Cells1. Fibroblasts

2. Macrophages

3. Plasma cells

4. Mast cells

5. Fat cells or Adipocytes

6. Undifferentiated Mesenchymal Cells

7. Leukocytes


Fibroblasts• Most common cells

• Have two levels of activity:

active or quiescent.

• For active: fibroblasts

– With more abundant & irregular

cytoplasm process

– Have a basophilic cytoplasm

rich in RER, Golgi.

– Synthesize and secrete

• collagen and elastin forming fibers

• GAGs, proteoglycans and

multiadhesive glycoproteins

comprising the ground substances

• For quiescent: fibrocytes(small, slim spindle-shaped, fewer

processes, less RER)

Granulation tissue after a wound


Fibroblasts• Most common cells

• Have two levels of activity:

active or quiescent.

• For active: fibroblasts

– With more abundant & irregular

cytoplasm process

– Have a basophilic cytoplasm

rich in RER, Golgi.

– Synthesize and secrete

• collagen and elastin forming fibers

• GAGs, proteoglycans, and

multiadhesive glycoproteins

comprising the ground substances

• For quiescent: fibrocytes (small, slim spindle-shaped, fewer

processes, less RER)

Granulation tissue after a wound


Fibroblasts & Fibrocytes

Small, slim spindle-shaped, fewer

processes, less RER

Large active nuclei, basophilic cytoplasm, more

abundant & irregular cytoplasm process, more RER,

Golgi

↑

↑

Collagen bundles↑


Fibroblast (TEM)

• Typical features of

a protein-secreting

cell: rich in RER,

Golgi

• Long cytoplasmic

extensions

• Extracellularly

abundant collagen

or other fibers


Fibrocyte (TEM)

• Inactive fibroblast, with

fewer cytoplasmic

processes

• Inactive in synthesis and

secretion of materials

making ECM

• Reversible to the

fibroblast, in case of

injury and other

repairing situations


Macrophages (1)

• Derived from monocytes

• More cytoplasmic

projections or pseudopodia

involved in amoeboid

movement

• Cytoplasm:

– Acidophilic

– More lysosomes,

phagosomes and

residual bodies.


Macrophages (2)

• Function ：

– Phagocytotic activity

– Antigen processing and

presenting to immune cells

– Secretion of growth factor,

cytokine, and the others

• The mononuclear phagocyte

system: see Table 5-2

– All derived from monocytes of the

blood

– Localized outside of blood vessels


Macrophages


Macrophages (TEM)


Macrophage w/ RBC (SEM)


Macrophage w/ RBC（1）


Plasma Cells

• Differentiated from B

lymphocytes

• Eccentrically spherical nucleus

as “cartwheel” or “clock face”

• Large and ovoid cells with

intensely basophilic cytoplasm

due to its richness in RER.

• Producing antibodies:

– IgG, IgM, IgA, IgD, IgE


Plasma Cells

• Most localized

in intestinal

mucosa,

respiratory

tract, and that

with chronic

inflammations.


Plasma Cell


Mast Cells

• More near small blood vessels

• 20 - 30 μm in diameter

• Cytoplasm full of basophilic secretory granules, METACHROMASIA (change the color of some basic dyes from blue to purple or red)

– Histamine

– Heparin

– Eosinophil chemotactic factors, ECF

• Function similar to basophilic leukocytes

• Play an important role in allergic reactions, such as asthma


Mast Cells


Mast Cell (TEM)


Secretion of Mast Cells

Allergens: pollen or bee venom


Fibers

• Collagen Fibers

• Elastic Fibers

• Reticular Fibers


Collagen Fibers

• The most abundant fibers

with various diameters

• Fresh in white

• Bright pink in HE staining

• Composed of collagen

fibrils

• Formed by collagen type I

& III

• Have 60-70 nm periodicity

of transverse striations


Collagen Fibrils (TEM, longitudinal section)


60-70 nm periodicity of

transverse striations

Collagen Fibrils (TEM, Cross section)


Production of Collagen Fibers by Assembly of

Type I Collagen

Type I collagen molecules Fibrils Fibers

Procollagen molecule intertwined

A 67 nm periodicity

of cross striations

Procollagen subunit

Gap region

Gap region

Bundles


Elastic Fibers

• Fresh in yellow, called

yellow fibers

• Bright pink in HE, purple-

blue in Weigert staining

• Thinner in diameter,

coiled in free ends

• Composed of microfibrils

and core elastins

• More resilience


Elastic Fibers Elasticity


Elastic Fibers (Weigert Staining)


Elastin & Microfibril


Reticular Fibersalso called Argyrophil Fibers

• Extremely thin, more branch, extensive networks

• Not visible in HE, easily stained in silver, Argyrophil fibers

• Collagen type III, 60-70 nm periodicity of transverse striations

• Localized in basal lamina

• Set up a network in various organs (liver, hematopoietic organs)


Ground Substancesas both lubricant and a barrier to the penetration of

invadersP

rote

og

lyc

an

s

Gly

co

pro

tein

s

Core protein

(vertical rod)

Sulfated

GAGs (side

chains)

Branched chains of

monosaccharides

Globular

proteins


Ground Substances –Proteoglycans linked to hyaluronan

Hyaluronic

acids axisLink protein

Sulfated

GAGsCore

proteins


Ground Substances –

Glycoproteins

for cell recognization, adhesion, and migration

Fibronectin LaminiProf. Hong CHEN, Shanghai Med. College, Fudan Univ.


• Connective tissue proper：– Loose CT: the cells as the majors

– Dense CT: the fibers as the majors• Irregular：

• Regular：– Tendon：collagen fibers

– Ligament：elastic fibers, elastic tissues

• Specialized Connective Tissues:– Adipose tissue

– Reticular tissue

– Cartilage, Bone, Blood

• Embryonic Connective Tissues:– Mesenchyme, Mucous CT


Dense Irregular Connective Tissue


Loose CT (L) & Dense Irregular CT (D)


Dense Regular Connective Tissue

Long, parallel bundles of collagen fibers and fibrocytes in a tendon




– Loose CT: the cells as the majors

– Dense CT: the fibers as the majors

• Specialized Connective Tissues:

– Adipose tissue: adipocytes + ECM• White adipocytes:

– unilocular (one large central droplet)

– more common

• Brown adipocytes: – multilocular (multiple small lipid droplets)

– Reticular tissue



White Adipose Tissueunilocular (one large central droplet)


White Adipocytes


unilocular (one large central droplet)

White Adipose Tissue by osmium tetroxide


Brown Adipose Tissuemultilocular (multiple small lipid droplets)




– Loose CT: the cells as the majors

– Dense CT: the fibers as the majors

• Specialized Connective Tissues:

– Adipose tissue: adipocytes + ECM

– Reticular tissue: • Reticular cells

• Reticular fibers



Reticular Tissue

Reticular fibers: irregular black lines Reticular cells: heavily stained and dark


SUMMARY

• General Characteristics

• Classification

• Cells

• Fibers

• Ground substances


SUMMARY 1

General Characteristics of

Connective Tissue (CT)

• Few cells, more ECM.

• No polarity, inside located in

the body as its inner

environment

• Rich in blood and lymph

vessels, nerves.

• Originated from mesenchyme

• Supply a matrix for

connection, support,

nutrients, protection, etc.


SUMMARY 2: Classification of CT

• Connective tissue proper：Loose CT

Dense irregular/regular CT

• Embryonic Connective Tissues:

Mesenchyme, Mucous CT

• Specialized Connective Tissue:

Adipose tissue

Reticular tissue


SUMMARY 3: Cells

• Fibroblasts (fibrocytes): the major cell producing ECM

• Macrophages: the short-lived cells derived from monocytes

function as APC & phagocytosis

• Plasma cells: the short-lived cells derived from B lymphocytes

function as antibody-producing cells

• Mast cells: more METACHROMASIA granules

• Adipocytes (Fat cells): storage of triglycerides by forming adipose

tissue

• Undifferentiated Mesenchymal Cells: stem cell

• Leukocytes


SUMMARY 4: Fibers

• Collagen Fibers:

– The most important & abundant fibers

– Fibrils of Type I collagen bundled together

– 60-70 nm periodic crossbanding

• Reticular Fibers

– Fibrils of Type III collagen bundled together

– 60-70 nm periodic crossbanding

– Stained by silver as dark lines, as Argyrophil fibers

– Abundant in immune and lymphoid tissues

• Elastic Fibers, or sheets called elastic lamellae

– Composed of the proteins Elastin and fibrillin

– Exist in a stretchable conformation


Ground Substancesas both lubricant and a barrier to the penetration of invaders

Pro

teo

gly

ca

ns

Gly

co

pro

tein

s

Core protein

(vertical rod)

Sulfated

GAGs (side

chains)

Branched chains of

monosaccharides

Globular

proteins


SUMMARY 5:

Review Questions 1

• Compare and contrast the different types of

connective tissues as listed in the following table:

Types Fibers Cells Matrix Distribution Function

Loose connective tissue

Dense connective tissue

Adipose tissue

Reticular tissue


Review Questions 2 & 3

• Summarize the structure and function

of the fibroblasts, macrophages, mast

cells, and plasma cells.

• Describe the mononuclear phagocytic

system.


QUIZ 2 for Connective Tissue


Standards of

QUIZ 1

for Introduction &

Epithelia



Standards of

QUIZ 2

for Connective

Tissue

THE END


Prof. Hong CHEN, MD, PhD - fdjpkc.fudan.edu.cn

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