Download Embryonic Connective Tissues

Connective Tissue
http://jpkc.fudan.edu.cn/s/426/main.htm
Prof. Hong CHEN, MD, PhD
Office: Room 304, Building 9 East
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Email: hchen30@hotmail.com; hchen@graduate.hku.hk
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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)
Cells
•
•
•
•
•
•
•
Fibroblasts
Macrophages
Plasma cells
Mast cells
Fat cells or Adipocytes
Undifferentiated Mesenchymal Cells
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
↑
↑
↑
Collagen bundles
Large active nuclei, basophilic cytoplasm, more
abundant & irregular cytoplasm process, more RER,
Golgi
Small, slim spindle-shaped, fewer
processes, less RER
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
Macrophages (TEM)
Macrophage w/ RBC (SEM)
Macrophage w/ RBC（1）
Macrophage w/ RBC（2）
Macrophage w/ RBC（3）
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 Cell
Mast Cell (TEM)
Mast Cell (TEM)
Secretion of Mast Cell
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)
Collagen Fibrils
(TEM, Cross section)
Production of Collagen Fiber by Assembly of
Type I Collagen
Type I collagen molecules
Fibrils
Fibers
Bundles
Gap region
Procollagen subunit
Procollagen molecule intertwined
A 67 nm periodicity
of cross striations
Gap region
Elastic Fibers
• Fresh in yellow, called
yellow fibers
• Bright pink in HE, purpleblue 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)
Elastic Fibers (Weigert Staining)
Elastin & Microfibril
Reticular Fibers
also 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 Substances
as both lubricant and a barrier to the penetration of
invaders
Sulfated
GAGs (side
chains)
Globular
proteins
Core protein
(vertical rod)
Glycoproteins
Proteoglycans
Branched chains of
monosaccharides
Ground Substances Proteoglycans
Hyaluronic
acids axis
Core
proteins
Link protein
Sulfated
GAGs
Ground Substances –
Glycoproteins
for cell recognization, adhesion, and migration
Fibronectin
Lamini
Classification of CT
• 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
Dense Regular Connective Tissue
Long, parallel bundles of collagen fibers and fibrocytes in a tendon
Classification of CT
• Connective tissue proper：
– 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
• Embryonic Connective Tissues:
– Mesenchyme, Mucous CT
White Adipose Tissue
unilocular (one large central droplet)
White Adipocytes
White Adipose Tissue
by osmium tetroxide
Brown Adipose Tissue
multilocular (multiple small lipid droplets)
Classification of CT
• Connective tissue proper：
– 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
• Embryonic Connective Tissues:
– Mesenchyme, Mucous CT
Reticular Tissue
Reticular fibers: irregular black lines
Reticular cells: heavily stained and dark
SUMMARY
• General Characteristics
• Classification
• Cells
• Fibers
• Ground substances
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.
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
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 Substances
as both lubricant and a barrier to the penetration of
invaders
Sulfated
GAGs (side
chains)
Globular
proteins
Core protein
(vertical rod)
Glycoproteins
Proteoglycans
Branched chains of
monosaccharides
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
Review Questions 1
• Compare and contrast the different types of
connective tissues as listed in the following table:
Types
Loose connective tissue
Dense connective tissue
Adipose tissue
Reticular tissue
Fibers
Cells
Matrix
Distribution
Function
Review Questions 2 & 3
• Summarize the structure and function
of the fibroblasts, macrophages, mast
cells, and plasma cells.
• Describe the mononuclear phagocytic
system.
THE END