1478 



HUMAN ANATOMY. 



The arteries of the gland are derived from the lachrymal, and the veins empty 

 into the ophthalmic vein. The nerves include sensory fibres from the lachrymal 

 branch of the ophthalmic, as well as secretory fibres from the sympathetic. 



Accessory lachrymal glands are found in both the upper and lower fornices, from 

 eight to thirty being present in the upper lid and from two to four in the lower. 

 They are very small and situated chiefly near the outer angle of the palpebral fissure. 



FIG. 1234. 



Alveoli 



Ducts 



FIG. 1235. 



Beginning of duct 



'Fat-cells 

 Section of lachrymal gland, under low magnification, showing general arrangement of alveoli. X 20. 



The lachrymal passages (Fig. 1236) begin by minute openings, the lachrymal 

 puncta, which are usually placed at the summit of the conical lachrymal papillae. 

 The latter occupy the margins of the eyelids, near the mesial extremity, at a point 



where the arched palpebral borders pass over into the 

 approximately horizontal boundaries of the lachrymal 

 lake. The upper punctum is situated 6 mm. from the 

 inner canthus ; the lower one is slightly larger and a 

 trifle farther removed from the canthus. 



The puncta open into the lachrymal canaliculi, 

 which at first are vertically directed, then bend abruptly 

 mesially and, taking a nearly horizontal course parallel 

 with the borders of the lachrymal lake, run as far as the 

 inner canthus, where they empty usually by a common 

 canal into the lateral and slightly posterior wall of the 

 lachrymal sac. Occasionally the two canaliculi do not 

 unite but open separately into a diverticulum of the sac, 

 known as the sinus of Maier. Each canalicultis is from 

 8-10 mm. in length. The lumen of the canal measures 

 only .1 mm. in diameter at the punctum, presents a diverticulum i mm. in diameter 

 at the bend, and continues with an approximately uniform calibre of . 5 mm. in its 

 horizontal portion. 



The structure of the canaliculi includes a lining of stratified squamous 

 epithelium, which rests upon a delicate tunica propria rich in elastic fibres, muscular 

 fibres from the orbicularis palpebrarum affording additional support. The muscle 

 bundles run parallel to the horizontal portion of the canaliculi, but are arranged as a 

 circular sphincter about the vertical portion. 



The lachrymal sac (saccus lacrimnlis) may be regarded as the upper dilated 

 portion of the naso-lachrymal duct, the lower part of which passes through a bony 

 canal and opens into the inferior nasal meatus beneath the lower turbinate bone, 



Alveoli of lachrymal gland more 

 highly magnified. X 235. 



