EUSTACHIAN TUBE. 709 
auditive, having a length of about one inch; and (6) a postero-external, osseous 
part, the pars ossea tube auditive, measuring half an inch in length. The two 
portions are not in the same plane, the cartilaginous part inclining downwards a 
little more than the osseous portion and forming, with it, a wide angle. Its 
lumen is widest at the ostium pharyngeum, narrowest at the junction of “the bony 
and cartilaginous portions, forming here the isthmus, and again expanding towards 
the tympanic cavity; hence it presents, on longitudinal section, somewhat the 
appearance of an hour-glass. The pars ossea occupies the angle between the 
squamous and petrous parts of the temporal bone, and is separated by the processus 
cochleariformis from the canal containing the tensor tympani muscle, whilst imme- 
diately to its inner side is the carotid canal. The pars cartilaginea consists 
partly of cartilage and partly of fibrous membrane. The cartilage (cartilago tube 
auditive) presents the form of an elongated triangular plate, of which the apex is 
firmly attached to the inner end of the pars ossea, while the base is free and forms 
a projection on the upper and posterior aspects of the pharyngeal orifice. The 
upper edge of this cartilaginous plate is bent outwards in the form of a hook, and 
so produces a furrow open below and externally, the furrow being converted into 
a complete canal by the fibrous part of the tube. On transverse section (Fig. 518) 
the cartilage presents two laminze, continuous with each other superiorly: (@) 
lamina medialis, broad and thick; and (4) 
lamina lateralis, thin and hook-shaped. 
At the ostium pharyngeum the lamina 
medialis forms the entire inner wall of the 
tube, but it gradually diminishes in breadth lateralis 
on approaching the isthmus tub. J issures 
are often seen in the cartilage; sometimes 
it is completely separated into several _ pjtator yl) \ aries, 
pieces, or accessory islands may be observed “B® 77>) Nie ) medialis 
in the roof, floor, or membranous part. By CI AW We 
The upper and inner aspects of the 
Lamina 
cartilage are firmly fixed to the base of the Taumen 
. . : Hi Vis ot tube 
skull, where it lies in a groove, the sulcus... j y ae ss 
tube auditive, situated between the great salpingo- i: 
wing of the sphenoid and the petrous- ?™°"°™ Mf 
= : ees / Mucous 
temporal. Extending forwards on to the Mi; a) = sinids 
root of the pterygoid process this sulcus /), 
ends at a projection, the processus tubarius, 
on the middle of the internal pterygoid 
plate. The tensor palati muscle les to 
the outer side of the tube and receives 
5 : . Fic. 518.—TRANSVERSE SECTION OF THE 
some fibres of origin. from its lamina CARTILAGINOUS PART OF THE EUSTACHIAN TUBE. 
lateralis; these fibres constitute the dilator 
tube muscle of Riidinger. To the inner side of the cartilage are found the levator 
palati and the mucous membrane of the pharynx. The membranous part (lamina 
membranacea) consists of a strong fibrous membrane, stretching between the two 
edges of the cartilage, and so completing the under and outer “parts of the canal. 
Thin above, it becomes thickened below and forms the fascia salpingo-pharyngea 
of Troltsch, ‘which gives origin to some of the fibres of the tensor palati muscle. 
Between this fascia and the mucous lining of the tube is a layer of adipose tissue. 
The pharyngeal orifice of the Eustachian tube (ostium pharyngeum tube), tri- 
angular or oval in shape, is situated on the lateral wall of the naso-pharynx, the 
centre of the opening being on a level with the posterior end of the inferior tur- 
binated bone. It is bounded above and behind by a pad or cushion produced by 
the inner end of the cartilage, which here abuts against the mucous membrane. 
The posterior part of this cushion is very prominent and forms the anterior boundary 
of the fossa of Rosenmiiller. Prolonged downwards from it is an elevation 
of the mucous membrane, termed the plica salpingo-pharyngea, which covers the 
small salpingo-pharyngeus muscle. From the upper part of the cushion an indis- 
tinct fold, the plica salpingo-palatina, extends to the palate. 
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