60
UNIT 2
Basic Tissues
Figure 4-1A.
The origin of connective tissue cells.
The
left panel
shows cells arising from
undifferentiated mesenchymal cells
. These cells are formed in, and remain within, the
connective tissue and are also called
± xed cells
. The
panel on the right
shows cells arising from
hematopoietic stem cells
. These cells
differentiate in the bone marrow, and then must migrate by way of circulation to connective tissue where they perform their various
functions. They are also called
wandering cells
.
Undifferentiated mesenchymal cells
Hematopoietic stem cells
Chondroblast
Adipocyte
Fibroblast
Osteoblast
Neutrophil
Eosinophil
Basophil
Monocyte
Mast cell
B lymphocyte
Chondrocyte
(cartilage)
Osteocyte
(bone)
Macrophage
Osteoclast
Plasma cell
A
Figure 4-1B.
A representation of the main types of connective tissue cells in connective tissue proper.
The nuclei of these connective tissue cells are indicated in
purple
.
Note
:
Mast cells
,
eosinophils
,
basophils
, and
neutrophils
all
contain granules in their cytoplasm. The
light yellow circle
in the
adipocyte
(fat cell) represents its lipid droplet. These cells are not
drawn to scale; the adipocyte is much larger than the others.
D. Cui
Adipocyte
Fibroblast
Mast cell
Macrophage
Eosinophil
Basophil
Neutrophil
B lymphocyte
Plasma cell
B
SYNOPSIS 4-1
Functions of the Cells in Connective Tissue Proper
Fibroblasts
are responsible for synthesis of various F
bers and extracellular matrix components, such as collagen, elastic,
and reticular F bers.
Macrophages
contain many lysosomes and are involved in the removal of cell debris and the ingestion of foreign
substances;
they also aid in antigen presentation to the immune system.
Adipocytes
function to store neutral fats for energy or production of heat and are involved in hormone secretion.
Mast cells
contain many granules, indirectly participate in allergic reactions, and act against microbial invasion.
Plasma cells
are derived from B lymphocytes and are responsible for the production of antibodies in the immune response.
Lymphocytes
participate in the immune response and protect against foreign invasion (see Chapter 10, “Lymphoid System”).
Neutrophils
are the F rst line of defense against bacterial invasion.
Eosinophils
have antiparasitic activity and moderate allergic reactions.
Basophils
have a (primary) function similar to mast cells; they mediate hypersensitivity reactions (see Chapter 8, “Blood
and Hemopoiesis”).
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