Jones Quain.

Quain's Elements of anatomy (Volume 3:4) online

. (page 3 of 44)
Online LibraryJones QuainQuain's Elements of anatomy (Volume 3:4) → online text (page 3 of 44)
Font size
QR-code for this ebook


Thomson.) -.

p, parotid gland ; p', socia paro-
tidis ; d, the duct of Stensen before it
perforates the buccinator muscle ; a,
transver.se facial artery ; n, n, branches
of the facial nerve emerging from below
the gland ; /, the facial artery passing
out of a groove in the submaxillary
gland and ascending on the face ; am,
superficial portion of the submaxillary
gland.

muscle, and behind by the ex-
ternal meatus of the ear, the
mastoid process, and sterno-
mastoid muscle. Its anterior
border, which lies over the
ramus of the lower jaw, is
more irregular, and stretches
forwards to a variable extent
on the masseter muscle. It is
from this anterior border of the
gland that the excretory duct
passes off; and there is fre-
quently found in connection with the duct, and lying upon the masseter muscle, a
small process or a separated portion of the gland (p'), which is called glandula socia
parotidis. On trying to raise the deeper part of the parotid gland from its position,
it is found to extend far inwards, between the mastoid process and the ramus of the
jaw, towards the baso of the skull, and to be intimately connected with several
deep-seated parts. Thus, above, it reaches into and occupies the posterior part of
the glenoid cavity ; behind and below, it touches the digastric muscle, and rests on
the styloid process and styloid muscles ; and, in front, under cover of the ramus of
the jaw, it advances a certain distance between the external and internal pterygoid
muscles.

The internal carotid artery and internal jugular vein are close to the deep surface
of the gland. The external carotid artery, accompanied by the temporo-maxillary
vein, passes through the parotid gland, and in that situation divides into the
temporal and internal maxillary arteries, the former soon giving off its auricular and
transverse facial branches. The gland is also traversed by the facial nerve, which




16 ORGANS OF DIGESTION.

divides into branches within its substance, and it is pierced by branches of the great
auricular nerve, while the auriculo-temporal nerve ascends beneath its upper and
posterior part.

The parotid duct, named also Sten sen's duct (d. tStenonianus), appears at the
anterior border of the gland, about one finger's breadth below the zygoma, and runs
forwards over the masseter muscle, accompanied by the socia parotidis, when that
accessory portion of the gland exists, and receiving its duels. At the anterior
border of the masseter, the duct (d) turns inwards through the fat of the cheek and
pierces the buccinator muscle ; and then, after running for a short distance obliquely
forwards beneath the mucous membrane, opens upon the inner surface of the
cheek, by a small orifice on a papilla opposite the crown of the second molar tooth
of the upper jaw. Its direction across the face may be indicated by a line drawn
from the lower margin of the concha of the ear to a point midway between the
red margin of the lip and the ala of the nose. The length of the Stenonian duct
is about two inches and a half (62 mm.), and its diameter rather less than ^th of
an inch (3 mm.). At the place where it perforates the buccinator, its canal is as
large as a crowquill, but at its orifice it is smaller than in any other part, and will
only admit a fine probe.

Blood-vessels and nerves. The vessels of the parotid gland enter and leave
it at numerous points. The arteries are derived directly from the external carotid,
and from those of its branches which pass through or near the gland. The veins
correspond. The lymphatics join the deep and superficial set in the neck ; and there
are often one or more lymphatic glands embedded in the substance of the parotid.
The nerves come from the sympathetic plexus on the external carotid artery, and
also from the facial, the auriculo-temporal and great auricular nerves. In the dog
and cat it has been experimentally shown that the parotid derives its cerebro-spinal
nerve-supply from the glosso-pharyngeal, through the lesser superficial petrosal nerve
and the otic ganglion, the fibres finally passing to the gland by a branch of the
auriculo-temporal.

VARIETIES. An instance is recorded by Gruber of a remarkable displacement of the
parotid on one side ; the whole gland being situated on the masseter muscle as if it were an
enlarged socia parotidis (Virchow's Archiv, xxxii.). Its absence has also been recorded by
Poirier (Bulletins de la societe anat. de Paris, 1888).

The submaxillary gland. The submaxillary gland (fig. 4, 11 ; fig. 20, sm), the
next in size to the parotid, is of a spheroidal form, and weighs about 2 or 2| drachms
(8 to 10 grammes). It is situated immediately below the base and the inner surface
of the inferior maxilla, and above the digastric muscle. In this position (fig. 4, 11)
it is covered by the skin, fascia, and platysma myoides, and its inner surface rests on
the mylo-hyoid, hyo-glossus, and stylo-glossus muscles ; above, it corresponds with a
depression on the inner surface of the jaw-bone ; and it is separated behind from the
parotid gland merely by the stylo-maxillary ligament. The facial artery, before it
mounts over the jaw-bone, lies in a deep groove upon the back part and upper border
of the gland ; while the vein is placed on the superficial surface of the gland.

The duct of the submaxillary gland, named Wharton's duct (d r , fig. 21), which is
about two inches (50 mm.) in length, leaves the main gland posteriorly, together with
a thin process of 'the glandular substance, and passing round the posterior border of
the mylo-hyoid muscle (nih}, runs forwards and inwards above that muscle, between
it and the hyo-glossus and genio-glossus, and beneath the sublingual gland, to
reach the side of the frasnum linguae. Here it terminates, close to the duct of the
opposite side, by a narrow orifice, which opens at the summit of a soft papilla
(fig. 5, 5} seen beneath the tongue. The obvious structure of this gland is like that



THE SALIVARY GLANDS. 17

of the parotid ; but its lobes are larger, its surrounding areolar web is finer, and its
attachments are not so firm. Moreover, its duct has much thinner cqats_than the
parotid duct.

Blood-vessels and nerves. The blood-vessels of the submaxillary gland are
branches of the facial and lingual arteries and veins. The nerves include those
derived from the submaxillary ganglion, and through this from the chorda tympani,
from the lingual branch of the inferior maxillary (and in rare cases from the mylo-
hyoid branch of the inferior dental nerve), and from the sympathetic.

VARIETIES. Gruber (Virchow's Archiv, Bd. cii.) has recorded a case of complete absence
of both submaxillary glands.

The sublingual gland. The sublingual gland (fig. 1, 8, and fig. 21, si), the
smallest of the salivary glands, is of a narrow oblong shape and weighs scarcely one
drachm (4 grammes). It is situated along the floor of the mouth, where it forms a
ridge between the tongue and the gums of the lower jaw, covered only by the mucous
membrane. It extends from the fraenum linguge in front, where it is in contact
with the gland of the opposite side, obliquely backwards and outwards for rather
more than an inch and a half. On its inner side it rests on the genio-glossus ;

Fig. 21. VlEW OF THE RIGHT SUBMAXILLARY AND
SUBLINUUAL GLANDS FROM THE INSIDE. (Alien

Thomson. )

Part of the right side of the jaw, divided from the
left at the symphysis, remains ; the tongue and its
muscles have been removed ; and the mucous mem-
brane of the right side has been dissected off and hooked
upwards so as to expose the sublingual glands ; s m,
the larger superficial part of the submaxillary gland ;
/, the facial artery passing through it ; s m', deep
portion prolonged on the inner side of the mylo-hyoid
muscle m h ; s I, is placed below the anterior large part
of the sublingual gland, with the duct of Bartholin
partly shown ; s I', placed above the hinder small end
of the gland, indicates one or two of the ducts per-
forating the mucous membrane ; d, the papilla, at which the duct of Wharton opens in front behind
the incisor teeth ; df, the commencement of the duct ; h, the hyoid bone ; n, the lingual nerve ; close to
it is the submaxillary ganglion.

below, it is supported by the mylo-hyoid muscle (mh\ which is interposed between
it and the main part of the submaxillary gland ; and it is here in close contact
with the Whartonian duct, with the accompanying deep portion of the last-named
gland, and also with the lingual branch of the fifth nerve.

The lobules of the sublingual gland are not so closely united together as
those of the other salivary glands, and the ducts from many of them open separately
into the mouth, along the ridge which indicates the position of the gland. These
ducts, named ducts of Rivinus, are from eight to twenty in number. Some of
them open into the duct of Wharton. One, longer than the rest (which is
occasionally derived in part also from the submaxillary gland), runs along the
Whartonian duct, and opens either with it or very near it ; this has been named the
duct of Bartholin, but it is inconstant in its occurrence (Chievitz, Suzanne).

Blood-vessels and nerves. The blood-vessels of this gland are supplied
by the sublingual and submental arteries and veins. The nerves are numerous,
and are derived from the lingual branch of the fifth, the chorda tympani and the
sympathetic.

STRUCTURE OP THE SALIVARY GLANDS

These glands are constructed on the compound racemose type (see Vol. I.,
Part ii., p. 399). Their ducts (traced backwards), after branching a certain number

VOL. III., PT. 4. C




18



ORGANS OF DIGESTION.





of times, terminate in fine ramuscules, into which the alveoli open. The alveoli of
the salivary glands do not always present the form usually regarded as typical of the
alveoli of a compound racemose gland. They are sometimes dilatations of the

Fig. 22. DIAGRAM OF THE CONSTRUC-
TION OP A LOBULE OF A TUBULO-

HACEMOSE (ACINO-TUBULAR) MUCOUS
OLA ND.(From Kolliker.)

r<. duct; 6, a I ranch of the duct;
c, alveoli as they lie together in the
gland ; d, the same separated, showing
their connection as an irregular tube.

extremities of the duct beset
with saccnlar enlargements, some-
times more tubular and even somewhat convoluted without marked saccnlation
(fig. 22) (acino-tubular variety), but there is no essential difference between the two
forms, transitions being met with between them. The alveoli are enclosed by a
basement membrane, which is not complete as in some glands, but forms a basket-
Fig. 23. MEMBRANA PROPRIA OF TWO ALVEOLI ISOLATED.
(Heidenhain, after Lavdovsky. )

The preparation is taken from the orbital gland of the dog,
which is similar in structure to a mucous salivary gland

like investment to the alveolus, the flattened cells
which form it being ramified and united together
by their branches (fig. 23). There is, however, in
addition a delicate homogeneous substance occupy-
ing the meshes between the cells (see the left-hand alveolus in fig. 23). The cells
of the basement membrane are said to send inwards processes to form a susten-
tacular network amongst the alveolar cells.

The alveoli are united by the blood- vessels and a small amount of loose connective

Fig. 24. SECTION OF PART OF THE HUMAN
SUBMAXILLARY GLAND. (Heidenhain. )

To the right of the figure is a group of
mucous alveoli, to the left a group of serous
alveoli.



tissue into lobules, and these again by
a larger quantity of the same tissue
into larger lobules. A considerable
? i mount of connective tissue also ac-
companies the blood-vessels and duct
in their ramifications through the
gland. The connective tissue, where
it is in larger amount, is lamellar in
character (Klein), and it contains,
besides the ordinary flattened cells, a
certain number of granular plasma -eel Is
and lymph-corpuscles, with fat cells
occasionally.

The alveoli of the salivary glands may be divided into two classes, according to
the nature of their secretion : those of the one kind yielding a ropy secretion
characterised by containing mucin, and those of the other kind, a thinner more
watery secretion, sometimes containing a considerable amount of serum-albumin, so




THE SALIVARY GLANDS.



19



that the secretion coagulates on being heated. The t\vo kinds of alveoli may
accordingly be distinguished as mucous and serous or albuminous (Heidenliain) ;
they differ from one another both in appearance and in the nature of their secreting
cells. In some cases an alveolus may contain mucous and serous cells side by side.

The human parotid and that of all mammals is composed of serous alveoli, and
the sublingual gland of mucous alveoli, but in man the submaxillary is a mixed
gland, containing both kinds of alveoli, although the serous are the more numerous
(fig. 24). In the dog and most other animals it is purely a mucous gland, and
in the rabbit and guinea pig it is purely a serous gland. Similar differences have
already been noticed (p. !)) in the small glands of the tongue. According to
Hermann a gland of tubular structure and furnishing a mucous secretion may
also be found attached to the submaxillary in man, and opening into ^Yharton'8
duct. In the guinea-pig and rabbit there are small flat mucous glands of tubular
structure connected both to the parotid and submaxillary, one to each, and sending




Fig. 25. SECTIONS OF THE SUBMAXILLARY GLAND OF THE DOG. A, DURING REST. 15, AFTER A
PERIOD OF ACTIVITY. (Ranvier. )

In A, most of the cells of the alveoli are large and clear, being filled with the material for secretion
(in this case, mucigen) which obscures their protoplasm, but some of the cells are small and proto-
plasmic, forming a crescentic group seen in most of the alveoli.

In B, the accumulated material (mucigenj is discharged from the mucin-secreting cells, which appear
in consequence shrunken and less clear. Both the cells and the alveoli are much smaller, and the pro-
toplasm of the cells is now more apparent. The marginal cells of Gianuzzi are enlarged.

c, "crescent " cells ; f/, mucus-secreting cells ; I, lumen of alveolus.

their ducts to open into the ducts of those glands (admaxillaries, Klein). Similar
tubular glands have been described in various other animals, and, as above men-
tioned, also in man. They are most frequently found in connection with the
submaxillary, where they form usually a glandular mass distinguishable to the
naked eye, and termed by Ranvier the retro-lingual (/land. Ranvier states, how-
ever, that he has not found this in the rabbit, hare, horse and sheep, or in man, but
it occurs constantly in all other animals examined.

Mucous alveoli. In the mucous glands and mucous alveoli of mixed glands
most of the alveolar cells, when the gland is in the inactive condition, appear large,
clear, and almost spheroidal in shape, and nearly fill the alveoli, which are distended
by the cells (right-hand side of fig. 24). The nucleus of each cell is in the part of
the cell next to the basement membrane, against which it is generally flattened, and
the cells may cause the basement membrane to be bulged out opposite to them. In
preparations hardened in alcohol the cells are finely granular, and with the exception
of the part around the nucleus are scarcely stained by carmine (fig. 25, A).

When the cells of the mucous alveoli are isolated, they not unfrequently exhibit,

c 2



20



ORGANS OF DIGESTION.



processes, one from the base of each cell : the projection is flattened and overlaps the
base of a neighbouring cell (Kolliker). The peculiar clear appearance of these cells
is due to the accumulation within them of mucin (or of a substance " mucigen "
from which mucin is formed). When fragments of the fresh mucous glands are
examined in solutions of salt of a certain strength, it may be seen that the clear
material which is accumulated within the cells is in the form of minute globules
(Langley). When swollen by the addition of water, these run together, and the cell

Fig. 26. ISOLATED MUCIN-SECRETINU CELLS FROM THE

SUBMAXILLARY GLAND OF A DOG. (Langley.)

a and b, isolated in 2 p. c. salt solution ; a, from
loaded gland ; b, from discharged gland ; ', b', similar
cells after treatment with dilute acid.

then appears distended with clear secretion, with
threads of protoplasm intersecting it (see fig.
2G).

Besides the " mucin cells " there are met
with in most alveoli of these glands, cells of a
different character, which from their position
may be named ''marginal cells." In some
mucous glands, e.g., the submaxillary of the cat,

they form an almost complete outer layer, next to the basement membrane, and
enclosing the mucin-cells, but in the dog's submaxillary gland they occur only in
small semilunar masses (lunulic- or crescents of Gianuzzi) at the bottom of the
alveoli, flattened up between the basement membrane and the mucin-cells (fig. 25, A ;
fig. 28, s). These marginal cells are small and granular, and stain deeply with
carmine and haematein.

If the mucous glands are stimulated to secretion, the mucin-cells become
gradually smaller and less clear, their contents being exuded in the form of mucus,
which first fills the cavity of the alveolus and then passes on into the duct. At the
same time the cells are easily stained with carmine and their nuclei are no longer



A









Fig. 27. ALVEOLI OF SEROUS GLANDS. A, AT KHST. B, AFTER A SHORT PERIOD OF ACTIVITY.

C, AFTER A PROLONGED PERIOD OF ACTIVITY. (Langley. )

flattened, but assume a more rounded form and central position (fig. 25, B). If the
gland be strongly urged to activity, as by prolonged stimulation of its cerebral
nerves, the mucin-cells may undergo still more profound alterations, and may even,
according to Heidenhain, become partially or wholly disintegrated, but probably the
cell is normally never destroyed. It is possible, however, that, in extreme salivation,
some of the mucin-cells are occasionally destroyed, but whether the marginal cells
multiply and become filled with secretion, and thus serve to replace the mucin-cells
which are lost is doubtful, for it is rare to find evidence of cell-division during
functional activity of the gland.

Serous alveoli. In the serous glands and serous alveoli of mixed glands, the
cells, in the inactive condition of the glands, are in the fresh condition and in osmie



THE SALIVARY GLANDS.



21



preparations seen to be packed full of distinct granules, of an albuminous nature,
which obscure their nuclei (Langley). The granules are imbedded in_the proto-
plasm of the cells and the latter almost completely fill the alveoli, scarcely any
lumen being discernible (fig. 27, A).

After a short period of activity the granules are found to have disappeared in
the outer part of the cell, the inner part being still distinctly granular, and some
of the granules are apparently free within the lumen of the alveolus, now becoming
distinct" (fig. 27, B). With more prolonged activity (fig. 27, C) the clear outer
part increases in extent, and the granules are found only in the part of the cell which
is clcse to the lumen, and in those parts which are contiguous to the adjacent cells
(corresponding perhaps to fine capillary clefts which pass from the cavity of the
alveolus between the cells). The nuclei have now become distinct, and the cells are
smaller. We may suppose therefore that the granules, which no doubt contain the
specific elements of the secretion, are formed by or from the protoplasm of the
cells during rest, and are discharged into the lumen and dissolved during activity.
Probably however even during activity new granules are constantly being formed

Fig. 28. SECTION OF THE SUBMAXILLAKY
GLAND OF THE DOG, SHOWING THE
COMMENCEMENT OF A DUCT IN THK
ALVEOLI. MAGNIFIED 425 DIA-
METERS. (E. A. S.)

, one of the alveoli, several of which
are in the section shown grouped around
the com men cement of the duct, d' ', a', an
alveolus, not opened by the section ; b,
basement membrane in section ; c, inter-
stitial connective tissue of the gland ; d,
section of a duct which has passed away
from the alveoli, and is now lined with
characteristically-striated columnar cells ;
s, sernilunar group of darkly-stained cells
at the periphery of an alveolus.

and passed onwards towards the
lumen. According to Langley,
the three processes of growth of
the clear protoplasm, conversion
of this into granules, and dis-
charge of these into the lumen, are all proceeding simultaneously in different parts
of the cell during activity.

In glands which have been hardened in alcohol the granules are no longer seen,
their place being occupied by a clear substance which does not stain with carmine.

Ducts. In the serous glands, and serous parts of mixed glands, the first or
intercalary part of the duct which conveys the secretion from the alveoli is narrow,
and lined with clear flattened cells with elongated nuclei. After a longer or shorter
course, this part passes by a somewhat narrower neck, lined with cubical cells with
small nuclei, into the intralobular ducts (Klein).

In the mucous glands the intercalary ducts are also lined (fig. 28, d'} with clear
cells continuous with the cells of the alveoli, but flattened against the basement
membrane so as to leave a considerable lumen.

This first part of the duct is generally shorter than the corresponding part in
the serous glands, and is regarded by Klein as representing only the part by him
termed the "neck"; more probably, however, it must be looked upon as repre-
senting both parts, although they are not here so clearly differentiated. The
intercalary part of the ducts is described by Klein as being lined, within the




OEGANS OF DIGESTION.




epithelium, by a special delicate nucleated membrane, which in some animals is
continued into the intralobular ducts.

In the next or mtralobular part of the duct (fig. 28, d) the character of the
epithelium changes abruptly, the cells becoming large and columnar or conical, the

Fig. 29. SECTION OF ALVEOLI OF SUBLINQUAL GLAND, HUMAN, PRE-
PARED BY GOLGl'g SILVER OHROMATE METHOD. (E. M tiller.)

I, lumen, stained, showing lateral diverticula proceeding between
and also into the cells of the alveoli ; h, diverticula penetrating into
" crescents. "

rounded or truncated apex being directed towards the
lumen of the tube. Each cell contains a spherical nucleus
near the centre (fig. 28). The part of the cell next
the lumen of the duct is granular in character, whereas
the part nearest the basement membrane is finely striated
longitudinally. This striated appearance is most distiuct
in the ducts of the submaxillary gland ; it is due to the
presence of a rod-like or fibrillar structure in that part of
the cell.

The lumen of the ducts is continued directly into the
alveoli, and its course there can be traced both by injec-
tion and in preparations stained by the silver chromate

method. By the latter method it has been shown that diverticula extend between
the cells of the alveoli, and minute channels are also traceable for a short distance
into the protoplasm of the cells. In the mucous alveoli a special diverticulum of
the lumen passes to each crescent of Gianuzzi, and ramifies within this between and
perhaps partly within its component cells (figs. 29, 30).

The larger ducts acquire a coating of fibrous and elastic tissue outside the
basement membrane, and, except in those of the sublingual gland, a few plain

Fig. 30. TKRMINAL NERVE- FIBRILS IN AN ALVEOLUS OF THK

SUBMAXILLARY GLAND OF THE DOG. (Gr. RetziuS. ) Chl'Omate

of silver method.

The extension of the lumen into the crescents of Gianuzzi is
also shown.

muscular fibre-cells are also to be found. The
columnar epithelium is here double, a second row
consisting of somewhat smaller cells lying outside,
and fitting between, the elongated cells which are
continuous with those of the smaller ducts.

Vessels and nerves. The blood-vessels of

the salivary glands are numerous, and form a close capillary network outside the
basement membrane both of the alveoli and the ducts.

The lymphatics commence in the form of lacunar clefts between and around
the alveoli, lying closer to these than do the networks of blood-capillaries
(Gianuzzi). The issuing lymphatics accompany the blood-vessels and ducts.

The nerves are large and numerous, and many of them exhibit minute ganglia,
especially those in the dog's submaxillary. There are fewer in the human sub-
maxillary gland, and no ganglia in the parotid (Klein). Some of them have been
observed to end in Pacinian corpuscles of a simple kind (Krause). Many, no doubt,



Online LibraryJones QuainQuain's Elements of anatomy (Volume 3:4) → online text (page 3 of 44)