Page 133 - My FlipBook

PULP. 131

are in structure like large capillaries (Fig. 113). This peculiarity of the
bloodvessel walls is of great importance, as it renders the tissue specially
liable to such pathologic conditions as hyperemia and inflammation.

XEEVE OF THE TULP.
Several comparatively large bundles of medullated nerve fibers, con-
taining from six or eight to fifteen or twenty fibers, enter the pulp
in com pan V with the bloodvessels and pass occlusally through the
central j)ortion of the tissue. These bundles branch and anastomose
with each other very freely. Most of the fibers lose their medullary
sheath before reaeliing the layer of AVeil, in which position they form a
plexus of non-nieduUated fibers ; from these fibers free endings are given
off, which penetrate between the odontoblasts. In some cases these
have been followed over on to the dentinal ends of tiie odontoblasts,
but in no instance have they been followed into the dentinal tubules.

THE FUNCTIONS OF THE PULP.
The pulp performs two functions, a vital and a sensory.
The vital function is the formation of dentin, and is performed
bv the layer of odontoblasts. This is the principal function of the
pulp, and it is first manifested in the development of the tooth before
the dentinal papilla is converted into the dental jnilp by being inclosed
in the formed dentin. After the tooth is fully formed the vital func-
tion is not manifested unless the pulp is stimulated by some excitation
affecting trophic centres and which causes the formation of secondary
dentin. There are some exceptions where the formation is entirely
local.
The Sensory Function.—In regard to sensation, the pulp resembles
an internal organ. It has no sense of touch or localization, and re-
sponds to stimuli only by sensations of pain. The pain is usually
localized correctly with reference to the median line, but, aside from
that, is localized only as it is referred to some known lesion. If several
pulps on the same side of the mouth and in teeth of both the npj)er
and lower arches were exposed so that they could be irritated without
im])n'.-sions reaching the peridental membrane, and the patient were
blindfolded, it would l)e impossible for him to tell which of the pulps
was touched. The \x\\\\ originating from a tooth pulp may be referred
to the wrong tooth or to almost any point on the same side supplied by
the fifth cranial nerve.
The pulp is especially sensitive to changes of temperature, but is
incapable of differentiating between heat and cold ; this fact is often
made use of in differential diagnoses (see Chapter XVI.). The pulj) is