Bone remodeling, nasal.
is necessary during bone formation in
order to mold the bone into a proper shape to carry out its
function. Remodeling usually occurs on the surface of the
play different roles.
In order to achieve a certain shape, bone matrix is continu-
ally being deposited by
in one region, and, at
the same time, bone matrix is being absorbed by osteoclasts
in another area.
are large, multinucleated cells,
which originate from monocytes and act as phagocytes. They
often sit in the
by ongoing reabsorption) on the bone surface. Osteoclasts
are under the inﬂ uence of the hormone
, which is
synthesized by the
produced by the
inhibits osteoclast activity and reduces bone reabsorption.
indirectly increases osteoclast activity
and increases bone reabsorption.
are large, multinucleated cells derived from cells seen in circulating blood as monocytes, which are derived, in turn, from
progenitor cells in the bone marrow. Key features in identifying an osteoclast are multiple nuclei, abundance of
cytoplasm, and intimate attachment to the surface of bone matrix. The mitochondria provide the energy for pumping protons into
the space adjacent to the
. The cytoplasm near the matrix contains
, the acid hydrolases of which are secreted
into the space adjacent to the bone matrix. This area of the cytoplasm also contains numerous electron lucent
ably reﬂ ect
of degraded matrix components. In an active osteoclast, the
in the central part of the interface
between the cell and the matrix is highly folded into a rufﬂ ed border, a structure that is not discernible in this electron micrograph.
Lumen of venule