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BODY EQUILIBRIUM AND CONNECTIVE TISSUE GALLOZZI
in relation among other things to the nature of the
tissue to which they belong and to the position
this takes up in the organism. Generally speaking,
it is possible to distinguish between the cells delegated
to form and maintain the matrix (represented
especially by fibroblasts, but also by cells
of similar nature present in other tissues), cells
delegated to defend the organism (macrophages,
mast cells and leukocytes) and cells delegated
to perform special functions, like the adipocytes
of the adipose tissue which store fats as an energy
reserve for the body (Figure 1).
FIBROBLASTS
Fibroblasts are the basic cells of connective
tissue; their function is to produce fibres and the
other components of the extracellular matrix
which constitute by far the most abundant element
of tissue and on which depend the support
functions of connective tissue. Fibroblasts
are generally of fusiform appearance, although
varieties exist which present quite different morphologies,
having a stellate or tentacular appearance
for example. They are generally to be found
scattered in the matrix they themselves have created
and in many cases they are arranged along
the fibres. When they cease their biosynthetic
activity, fibroblasts change into fibrocytes.
Therefore fibroblasts and fibrocytes represent the
two functional moments of the same cell. Cells
with a similar function are present in the different
subtypes of connective tissue, although in
some cases they present particular functional features.
Specifically:
— the chondroblasts produce the matrix of
cartilaginous tissue;
— the osteoblasts produce the matrix of bone
tissue, characterized by the fact of being calcified;
— the cementoblasts and the odontoblasts
produce the dental matrix.
MACROPHAGES
Macrophages are cells specialising in phagocytosis,
a mechanism they employ with a defensive
function. They are delegated to absorbing
and eliminating external elements such as viruses,
bacteria and also molecules and molecular
complexes that are dangerous for the organism.
These cells are also involved in the immune
response as their membranes present phagocyted
bacteria antigens, so enabling the lymphocytes
to recognize them. Under normal condi-
Figure 1.—Connective tissue cells.
Figura 1. — Cellule del tessuto connettivo.
cociti) e cellule deputate a funzioni speciali, come
gli adipociti del tessuto adiposo, che accumulano
grassi come riserva energetica del corpo (Figura 1).
FIBROBLASTI
I fibroblasti sono le cellule fondamentali del tessuto
connettivo; la loro funzione è quella di produrre le
fibre e gli altri componenti della matrice extracellulare,
che costituisce l’elemento di gran lunga più
abbondante del tessuto, e dalla quale dipendono le
funzioni di sostegno proprie del connettivo. I fibroblasti
sono generalmente di aspetto fusiforme, sebbene
ne esistano varietà che presentano morfologie anche
molto diverse, come un aspetto stellato o tentacolare.
Si trovano generalmente dispersi nella matrice
da loro stessi creata, ed in molti casi sono disposti lungo
le fibre. Quando cessano la loro attività biosintetica,
i fibroblasti si trasformano in fibrociti. Pertanto,
fibroblasti e fibrociti rappresentano i due momenti
funzionali di una stessa cellula. Cellule di funzione
analoga sono presenti nei diversi sottotipi di tessuto
connettivo, anche se presentano in alcuni casi peculiarità
funzionali. In particolare:
— i condroblasti producono la matrice del tessuto
cartilagineo;
— gli osteoblasti producono la matrice del tessuto
osseo caratterizzata dal fatto di essere calcificata;
— i cementoblasti e gli odontoblasti producono la
matrice nei denti.
MACROFAGI
I macrofagi sono cellule specializzate nella fagocitosi,
meccanismo che utilizzano con funzione
Vol. 62, N. 4 MEDICINA DELLO SPORT 387