Biomedical Engineering Reference
In-Depth Information
cf. Figure 1.17. According to Ottolenghi, the nerve fibers within the marrow cavity
fall into three main groups: (i) those that penetrate the walls of arterioles and
form delicate plexiform networks between the adventitia and the media, (ii) those
that surround the capillaries, and (iii) those that terminate between the cells of
parenchyma.
Fliedner
et al
. [26] studied the question concerning the mechanisms that allow
the bone marrow hemopoiesis to act as one cell renewal system although the
bone marrow units are distributed throughout more than 100 bone marrow areas
or units in the skeleton. The effect that ''the bone marrow'' acts and reacts as
''one organ'' is due to the regulatory mechanisms: the humeral factors (such as
erythropoietins, granulopoietins, thrombopoietins, etc.), the nerval factors (central
nervous regulation), and the cellular factors (continuous migration of stem cells
through the blood to assure a sufficient stem cell pool size in each bone marrow
''subunit'').
The nervous system is differentiated into efferent nerves and afferent nerves.
Efferent nerves - otherwise known as
autonomic or motor or effector neurons
- carry
nerve impulses
away
from the central nervous system to effectors such as muscles
or glands. The opposite activity of direction or flow is afferent (sensory) [121].
The majority of the skeletal innervation system is composed of sensory fibers
originating from primary afferent neurons located in the dorsal root and some
cranial nerve ganglia, whereas the other nerve fiber populations are adrenergic and
cholinergic in nature and originate from paravertebral sympathetic ganglia. The
50
µ
m
Figure 1.18
Nerve fibers in the canal between perios-
teum and proximal mataphysis of four-week rat tibia.
Growth-associated protein (GAP-43) and protein gene prod-
uct (PGP) 9.5 are visible. Courtesy of Litwin and Gajda.
