« PrécédentContinuer »
process termed the glenoid lobe is found, passing into the posterior or tympanic Fards === part of the glenoid fossa.
its coe Another runs into the interval between the sterno - mastoid and digastrie
1 muscles; and a pharyngeal process is occasionally found extending medially, anterior
tees in to the styloid process, towards the side of the pharynx.
bas rounded lymph glands, which can be recognised from the gland tissue by the this lis difference in their colour.
The OZEE | 2 ace <
Fig. 898.-HORIZONTAL SECTION THROUGH MOUTH AND PHARYNX AT THE LEVEL OF THE PALATINE TONSIL
carotid artery) are not indicated by reference lines.
The sup shich projer Tends bey
This sur saja and t
The facial process of the gland—often of considerable size—is a flat and somewhat triangular portion which runs forwards from the upper part of the front of the gland, and overlaps the masseter muscle to a varying extent; from its most anterior part the parotid duct emerges, and a separated portion of this process, often found lying immediately above the duct, is known as the glandula parotis accessoris (O.T. socia parotidis).
Ductus Parotideus (Stenonis).— The parotid duct (O.T. Stenson's) leaves the anterior border of the gland at its most prominent part (Fig. 897). It first runs forwards across the masseter, below the accessory parotid gland, and accompanied by branches of the facial nerve, and the transverse facial artery, which is commonly some distance above, though its relation is variable. Having crossed the masseter, it turns abruptly round the anterior' border of this muscle and runs
Toes of th pretenor be
The dele the mylo muscles.
Embedd lands, whi Tessels of t
mwards through the fat of the cheek, practically at right angles to the first part f its course, to reach the buccinator, which it pierces. Then passing for some listance (5 to 10 mm.) between the buccinator and the mucous membrane, it pens into the vestibule of the mouth by a very small orifice, on a variably leveloped papilla, opposite the crown of the second upper molar tooth.
The course of the duct, which is fairly constant, can be marked on the side of he face by drawing a line from the inferior edge of the acoustic meatus to a point nidway between the ala of the nose and the red of the lip; the middle third f this line corresponds fairly accurately, on the surface, to the course pursued
y the duct.
The duct measures from 15 to 2} inches (38 to 62 mm.) in length, and inch (3 to 4 mm.) a diameter. The calibre of the duct is very much greater than that of its orifice, which admits nly a fine bristle, and for this reason the duct may, to some extent, be looked upon as a eservoir for the saliva, as well as a duct for its conveyance. In the child it pierces the "sucking ad" on its way to the mouth.
A number of vessels and nerves are found in intimate relation to the parotid gland. These are: (1) The external carotid artery and its two terminal branches. This artery lies t first in a groove in the inferior and deep aspect of the gland. It then enters the gland substance nd lies deeply in it, as far up as to the neck of the mandible, when it divides into its two terminal ranches. The superficial temporal artery passes onwards and emerges from the superior supercial part of the gland, and the internal maxillary artery turns inwards and emerges from the eep part of the anterior surface. The transverse facial artery is given off in the substance of the gland, and emerges from between the zygomatic arch and the duct.
The posterior facial vein descends in the substance of the gland superficially, and divides in into the two terminal branches which emerge from the inferior part of the gland.
The facial nerve enters the posterior surface of the gland, slightly below its middle, and runs orwarus and laterally, dividing into its main branches within the gland, and lying superficial o the external carotid artery and posterior facial vein. Communicating branches from the uriculo-temporal and great auricular nerves to the facial also traverse the gland substance.
Vessels and Nerves.- The arteries which supply the gland arise from the external carotid rtery, and from the branches of this artery in relation to the gland.
The veins join the posterior facial vein and its tributaries. The lymph vessels pass to both he superficial and the deep cervical glands; there are also a few small parotid lymph glands, hich lie on the surface of the superior and inferior part of the parotid beneath the capsule. ome are said to be embedded in the substance of the parotid itself.
The nerves are derived (a) from the auriculo-temporal, great auricular, and facial, and 5) from the plexus caroticus externus. The fibres of the sympathetic are mainly vaso-constrictor.
The secretory fibres to the gland, arising in the brain-stem, pass out through the glossoharyngeal nerve, and pass from it through the lesser superficial petrosal nerve to the otic ganglion, nd from that ganglion to the gland in the auriculo-temporal nerve.
Glandulæ Submaxillares.-- The submaxillary glands are next in size to the arotid, and resemble them in their lobulation and colour. Each is placed partly n the submaxillary triangle and partly under cover of the mandible (Fig. 897).
In each gland two portions may be recognised, a somewhat superficial larger part, the body, lying in the submaxillary triangle, and a smaller deep part, the leep process, which springs from the middle of the deep surface of the body.
The superficial part, like the parotid, presents a superficial convex surface, which projects below the mandible, in the submaxillary triangle, but it frequently xtends beyond the limits of that space, and overlaps the digastric muscle.
This surface looks downwards and laterally; it is covered by the deep cervical ascia and the platysma and is crossed superficially by the anterior facial vein.
Deep to this surface the body of the gland is wedged upwards, between the medial surface of the mandible and the mylo-hyoid and hyoglossus muscles. It hus presents two surfaces, a lateral, which is in contact with the submaxillary Eossa of the mandible, and a medial, related to the mylo-hyoid, hyoglossus, the posterior belly of digastric, and stylo-hyoid muscles.
The deep process passes still further medially, around the posterior free margin of the mylo-hyoid muscle, and comes to lie between the mylo-hyoid and hyoglossus muscles.
Embedded in the substance of the gland are found a few submaxillary lymph glands, which are of importance from the connexion they have with the lymph vessels of the lip and of a portion of the tongue.
The external maxillary artery lies embedded in a groove in the superior and posterior part of the gland.
The gland is enclosed in an extremely delicate capsule of connective tissue derived from the deep cervical fascia.
In considering the relations of the gland, it is well to remark that there is in this region a three-sided space bounded laterally by the medial surface of the mandible below the mylo-hyoid line, medially and above by the mylo-hyoid muscle, and below by the skin and fascia passing from the margin of the jaw to the side of the neck. In this space the gland lies with lateral, medial, and inferior surfaces corresponding to the walls of the space.
The posterior end of the gland, which is its most bulky portion, either abuts against, or lies very close to, the sterno-mastoid, and is often overlapped by the inferior end of the parotid gland.
Ductus Submaxillaris.— The submaxillary duct (O.T. Wharton's) leaves the deep surface of the gland about its middle, and runs forwards beneath the mylo-hyoid muscle, along the superior and medial aspect of the deep process of
Surface of submaxil.
lary gland covered
Surface covered by
integument and fasciæ
Fig. 899.—THE SALIVARY GLANDS AND THEIR DUCTS.
the gland (Fig. 899). Pursuing its course forwards beneath the floor of the mouth, on the medial side of the sublingual gland, the duct crosses the hyoglossus and the genioglossus muscles, and finally opens on the floor of the mouth at the side of the frenulum linguæ, where its small orifice is placed on the summit of a soft papilla (caruncula sublingualis) close to its fellow of the opposite side.
While running forward beneath the floor of the mouth the duct, which is about two inches long (50 mm.), is crossed by the lingual nerve near the anterior border of the hyoglossus, that is opposite the 2nd molar tooth. The nerve passes from the posterior end of the mylo-hyoid ridge (against which it lies) forwards and medially in order to reach the inferior surface of the tongue, and it passes below the duct at the point indicated. As in the case of the parotid duct, the calibre of the submaxillary duct is much greater than that of the orifice by which it opens ; for this reason it likewise may be looked upon as forming, to some extent, a reservoir for the saliva secreted by the gland.
Vessels and Nerves. The arteries come chiefly from the external maxillary artery and its submental branch: the veins accompany the arteries. The nerves are derived through the submaxillary ganglion (which lies above the deep process of the gland), from the chorda tympani and lingual, and from the sympathetic plexus around the external maxillary artery. The lymph vessels pass to the submaxillary lymph glands.
Glandulæ Sublinguales.— The sublingual glands, the smallest of the principal salivary glands, are situated more deeply than the others.
Each lies immediately below the mucous membrane of the floor of the mouth, etween the tongue and the gum of the mandible, and there it causes the elevation n the floor of the mouth termed the plica sublingualis.
When the mucous membrane is removed from this region, the gland is found o be lying in the interval between the sublingual fossa (on the inner surface of he mandible above the mylo-hyoid line) and the genioglossus muscle, which asses from the mandible to the tongue. Below, it rests upon the deep surface f the mylo-hyoid muscle.
In shape it is almond-like, flattened from side to side, but is much wider (from bove downwards) anteriorly than posteriorly. It is usually from 11 to 1 inches (37 45 mm.) in length, whilst its bulk is about equal to that of two or three almonds.
Its detailed relations are as follows :—Its lateral surface rests against the inner aspect the body of the mandible above the mylo-hyoid line. Its medial surface is in contact with ne genioglossus, styloglossus, and hyoglossus muscles, as well as with the submaxillary
ct, which runs forwards between the gland and the muscles. Below, it rests on the ylo-hyoid, and at its posterior part on the deep process of the submaxillary gland; whilst
upper prominent border is covered only by the mucous membrane of the mouth, here ised up by the gland to form the plica sublingualis (Fig. 892). The anterior portion of e gland is much deeper and more bulky than the posterior half, and it meets its fellow the median plane beneath the frenulum linguæ. The posterior extremity grows gradually ore slender, but may extend to the posterior part of the mylo-hyoid ridge, where it lies ove the deep process of the submaxillary gland.
Its ducts, generally known as the ductus sublinguales minores (O.T. ducts of vinus), are about twelve in number and of small size; they leave the superior rt of the gland, and, after a short course, open on a series of papillæ, visible to e naked eye, which are placed along the summit of the plica sublingualis.
The gland is not enclosed in a distinct capsule, thus differing from the parotid and submaxil. y glands; but its numerous lobules, which are smaller than those of the glands just mentioned,
held together by fine connective tissue, loosely, but still in such a manner as to make one ore or less consolidated mass out of what was, in the embryo, a number of separate glands.
As a rule all the ducts open separately on the summit of the plica sublingualis, and appartly none of them join the submaxillary duct. Frequently some of those from the anterior and pre bulky part of the gland are larger than the others, but the presence of a large duct nning alongside of the submaxillary duct, and opening with or beside it, ductus sublingualis major (O.T. duct of Bartholin), is very rare, and must be considered as an exceptional condition in man, although normal in the ox, sheep, and goat. The same may also be said of ducts from the sublingual, which are described as opening into the submaxillary duct.
Vessels and Nerves.—The arteries are derived from the sublingual artery, a branch of the lingual, and from the submental, a branch of the external maxillary. The nerves come from the lingual, chorda tympani, and the external maxillary plexus, through a branch of the submaxillary ganglion which joins the lingual, and is conveyed by it to the gland. The secretory fibres run in the chorda tympani nerve, and thence through the submaxillary ganglion to the gland.
The glandula lingualis anterior (Blandini, Nuhni) has been described with the tongue.
Structure of the Salivary Glands (Fig. 900). — Each of the principal salivary glands consists of a number of lobules, loosely united together by connective tissue. From each of them one or more ducts emerge. Each duct when traced onwards divides into branches, which terminate in a group of saccular or tubular alveoli.
The epithelium lining the ducts is columnar in character, but becomes flattened at the junction with the alveoli.
The epithelium lining the alveoli shows different characters in different glands. In the parotid, and the small salivary glands of the vallate papillæ in which the secretion is watery or albuminous, the cells are uniform in character, and of small size. When the gland is at rest, the cells are filled with small granules, which when the secretion is poured out are transformed into the gland ferment (ptyalin). After secretion, only the deeper parts of the cells show the presence of granules. The nuclei are rounded, and lie near the centre of the cells. In the sublingual, labial, buccal, and other glands of the mouth and palate the secretion is of a mucous character and the cells are larger, and the nuclei are placed deeply. The cells appear clear and swollen unless special methods of preparation are employed. In such cases, e.g., when examined in serum, the cells are seen to contain large and distinct granules of mucigen which in secretion are transformed into mucus.
In the submaxillary gland and the anterior lingual gland both varieties of cells are present. In these cases, the larger, clear mucous cells line the cavity of the alveolus, and the smaller granular serous cells are arranged upon the basement membrane, deep to the former cells, in crescentic masses, termed the crescents or demilunes of Gianuzzi. They communicate with the cavity of the alveolus by small channels between adjacent mucous cells.
After secretion, the mucous cells become smaller, and stain more deeply than when loaded with mucigen before secretion.
PHARYNX. The pharynx is the expanded upper portion of the alimentary canal which lies posterior to and communicates with the mouth, the larynx, and the nasal.cavities, and is continuous inferiorly with the superior end of the cesophagus or gullet (Fig. 901).
It extends from the base of the skull, above, to the level of the sixth cervical vertebra (Fig. 903) and the lower border of the cricoid cartilage, below.
Its total length varies from 5 to 5! inches (12.5 to 14:0 cm.).
The inferior portion alone, that is, the parts lying opposite and inferior to the opening of the mouth, is functionally a part of the alimentary canal, for the portion above the level of the soft palate is used for respiration only.
It is, however, convenient to study the structure and relations of the whole of the pharynx at once.
Structurally the pharynx is a fibro-muscular bag, of conical form, wide above and narrow below. The wall of the superior part of the pharynx, in the region of the base of the skull, is firmly attached to the surrounding bony structures, especially around the orifice of the choanæ, and hence in this superior portion of the pharynx there is a permanent cavity containing air.
The lower portion gradually assumes a more tubular form, and the anterior and posterior walls approach one another, so that below the level of the opening of the larynx they are in contact with one another, and the cavity is reduced to a slit, except during the passage of food.
Dimensions of the Pharynx.-- From the fornix pharyngis, i.e. the highest part of the roof, to the superior surface of the soft palate at its junction with the hard palate, measures about 11 inches, or 3 cm. The vertical extent of the oral part of the pharynx is about 21 inches, or 6 cm., and that of the laryngeal part is about 24 inches, or 7 cm.
The inferior end of the pharynx is usually about 5$ to 6} inches from the margins of the incisor tooth, in a line passing through the cavities of the mouth and of the oral and laryngeal parts of the pharynx.
The other diameters are as follows: the antero- posterior diameter (depth) of the superior