Innervation of the cavernous body of the human efferent tear ducts and function in tear outflow mechanism

The lacrimal sac and nasolacrimal duct are surrounded by a wide cavernous system of veins and arteries comparable to a cavernous body. The present study aimed to demonstrate the ultrastructure of the nervous tissue and the localisation of neuropeptides involved in the innervation of the cavernous body, a topic not previously investigated. Different S‐100 protein antisera, neuronal markers (neuron‐specific enolase, anti‐200 kDa neurofilament), neuropeptides (substance P, neuropeptide Y, calcitonin gene‐related peptide, vasoactive intestinal polypeptide) and the neuronal enzyme tyrosine hydroxylase were used to demonstrate the distribution pattern of the nervous tissue. The ultrastructure of the innervating nerve fibres was also examined by means of standard transmission electron microscopy. The cavernous body contained specialised arteries and veins known as barrier arteries, capacitance veins, and throttle veins. Perivascularly, the tissue was rich in myelinated and unmyelinated nerve fibres in a plexus‐like network. Small seromucous glands found in the region of the fundus of the lacrimal sac were contacted by nerve fibres forming a plexus around their alveoli. Many nerve fibres were positive for S‐100 protein (S 100), neuron‐specific enolase (NSE), anti‐200 kDa neurofilament (RT 97), calcitonin gene‐related peptide (CGRP), substance P (SP), tyrosine hydroxylase (TH), and neuropeptide Y (NPY). Vasoactive intestinal polypeptide (VIP) immunoreactivity was only demonstrated adjacent to the seromucous glands. Both the density of nerve fibres as well as the presence of various neuropeptides emphasises the neural control of the cavernous body of the human efferent tear ducts. By means of this innervation, the specialised blood vessels permit regulation of blood flow by opening and closing the lumen of the lacrimal passage as effected by the engorgement and subsidence of the cavernous body, at the same time regulating tear outflow. Related functions such as a role in the occurrence of epiphora related to emotional responses are relevant. Moreover, malfunction in the innervation of the cavernous body may lead to disturbances in the tear outflow cycle, ocular congestion or total occlusion of the lacrimal passages.     

The presence of a local immune system in the upper blind and lower part of the human nasolacrimal duct

The nasolacrimal duct is exposed to exogenous agents, including potentially harmful microorganisms, coming from the eye surface by the lacrimal sac, and from the nasal cavity by the inferior meatus of the nose. The upper blind and lower part of the human nasolacrimal duct were examined immunohistochemically to ascertain the presence and localization of immunoglobulin-producing cells and the epithelial expression of IgA, IgM, and IgG in order to verify the possible antimicrobial properties of this duct. IgA-, IgM-, and IgG-positive immunocompetent cells were recognizable in the lamina propria of the upper blind and lower part of the human nasolacrimal duct, while an evident immunoreactivity for sIgA, IgM, and IgG was demonstrated in the cytoplasm of the apical epithelial cells. The results suggest that all the effector components of the mucosal immune system are present in that area of the human nasal mucosa next to the opening of the nasolacrimal duct as well as in the human lacrimal sac.     

Gastroesophageal reflux disease and the presence of pepsin in the tears

The nasolacrimal duct in association with the lacrimal puncta, lacrimal canaliculi and lacrimal sac functions to collect and drain the tear film into the nasal cavity at the inferior nasal meatus where a fold of nasal mucosa, the so-called valve of Hasner, prevents mucous from entering the nose. High-resolution computed tomography demonstrated air inside the sac and nasolacrimal duct in approximately 29.3% of healthy patients suggesting that the system is not completely competent and that air and secretions might reach the precorneal film.     

The fine structure of the epithelium of the main outlets from the liver and pancreas of the domestic chicken (author's transl)]

Light- and electronmicroscopic and some histochemical investigations on the major excretory ducts of pancreas and liver was carried out on 24 adult chicken. The epithelium of both ducts was shown to include: cells with apical secretory granules, non-differenciated duct cells, ciliated cells and migrating cells. In addition the epithelium of the pancreatic ducts included goblet cells. The distal plasmalemm and the microvilli are covered with surfacecoat, which like the secretory granules produces precipitate with PA-silver. This area of the cell also shows a strong reaction to M++ and Ca++ activated ATPase.     

Anatomy and histology of the lacrimal fluid drainage system

Five human specimens of the lacrimal canaliculus and sac were examined by light and scanning electron microscopy. The superior and inferior lacrimal canaliculi are lined with stratified squamous epithelium that is non-keratinized and non-mucin-producing. The common canaliculus is also lined with stratified squamous epithelium, but its lumen is much narrower than the lumen of the superior and inferior canaliculi. The common canaliculus opens into an ample space called the vestibule, where the epithelium changes to high pseudostratified columnar and then low pseudostratified columnar. The vestibule continues to the infundibulum of the lacrimal sac. The infundibulum is formed by several epithelial folds that radiate from the vestibular opening to the lacrimal sac. The vestibule and infundibulum are consistent transitional structures from the common canaliculus to the lacrimal sac. The connective tissue of the lamina propria from the common canaliculus to the lacrimal sac has two histological characteristics: numerous free cell aggregates (= lymphoid structure) and numerous venules and capillaries (= cavernous structure).     

The fine structure and histochemistry of human bile duct in obstruction and choledocholithiasis

Biopsies from the common bile ducts from seven patients undergoing surgery for biliary obstruction due to stones or malignancy were studied histochemically and electron microscopically. The surface of the bile duct is lined by a tall epithelium which extends into diverticula. Apically, they contain some neutral and sialated mucosubstances. Fucosyl residues were found in the Golgi apparatus and along the apical cell membrane. The latter is lined by microvilli. There was a well-developed rough endoplasmic reticulum and Golgi apparatus and a small number of apical secretory droplets. Large numbers of lipid droplets were present basally in some cells. Lipid-containing macrophages were also seen intra-epithelially and in the lamina propria. This suggests a possible pathway for lipid transport. The glands were lined by cuboidal cells, some containing much mucus--sulphated, sialated, and neutral with a basal nucleus. A well-developed endoplasmic reticulum and Golgi apparatus were found with abundant secretory droplets. The glandular epithelium contained lysozyme, alpha-1-antitrypsin, and alpha-1-antichymotrypsin. These may play a protective role. The lamina propria contained scattered smooth muscle cells amongst the fibroblasts and inflammatory cells.     

Fine structure of bat deep posterior lingual glands (von Ebner's)

We studied the morphology and ultrastructure of the bat (Pipistrellus k.k. and Rhinolophus f.e.) deep posterior lingual glands (Ebner's glands) during hibernation, summer and after stimulation with pilocarpine. Ebner's glands are formed by serous tubulo-alveolar adenomeres and by an excretory system organized in intercalated ducts, long excretory ducts and a main excretory duct. The latter opens in the vallum which surrounds the circumvallate papillae and in the groove of the foliate papillae. The secretory cells, which lack basal folds, show abundant and dense granules (PAS+, Alcian blue -), microvilli (scarce during hibernation), a Golgi apparatus (well developed during summer and after stimulation with pilocarpine), a large nucleus and RER cisternae stacked at the basal pole. Centrioles, lipid droplets, heterogeneous bodies (in content and density, probably lipofuscin bodies), lysosomal multivesicular bodies and large, dense granules with a microcrystalline structure were also encountered. The lateral membranes of adjacent cells are joined by desmosomes; their interdigitations are neither numerous nor prominent during summer. Microfilaments, often gathered in small bundles, lie in the lateral, peripheral cytoplasm without any relation with desmosomes. In summer and particularly after stimulation with pilocarpine, the apical pole of the secretory cells is characterized by many long microvilli, pedunculated hyaloplasmic protrusions and secretory granules. During hibernation the lumen is filled with secretory material. Myoepithelial cells are arranged among secretory cells or between them and the basal lamina. The short intercalated ducts show similarities with the analogous ducts of the parotid gland. Striated ducts are absent. Excretory ducts are endowed with: a) an inner layer of cuboidal cells characterized by poorly developed cytoplasmic organelles, rare dense granules and a few small microvilli; b) an outer layer of basal cells lying on the basal lamina. Myoepithelial cells are absent. The main excretory duct is lined by a stratified epithelium with an inner layer of conical-pyramidal cells surrounded by two-three rows of basal cells. The conical-pyramidal cells show poorly developed organelles, an apical border with small short microvilli and a prominent terminal web.     

The lacrimal fascia redefined.

It has been commonly accepted that the lacrimal fascia is an intact septum, composed of connective tissue, that separates the orbital cavity into a large compartment, which contains the eyeball, and a small compartment, which contains the lacrimal sac and nasolacrimal duct. the septum, however, is not necessarily always intact. We found a circular or oval opening in the lacrimal fascia in 37 of 52 specimens (71.2%) examined. The opening, which we shall refer to as the lacrimal fascial foramen, was located at variable levels in the lacrimal fossa. The lacrimal fascial foramen was buried in fatty tissue through which passed a branch of either the inferior palpebral artery or the infraorbital artery and a vein of the nasolacrimal duct. The clinical implications of the lacrimal fascial foramen in obstruction of the nasolacrimal duct are discussed.     

CT-anatomy of the nasolacrimal sac and duct

Summary Recent developments in ophthalmology such as balloon dilatation, stent implantation, laser therapy and endoscopy of the lacrimal drainage system raise the need for a detailed anatomical knowledge of this system. In this study morphometric measurements of the lacrimal drainage system were performed with thin-section axial computed tomography (CT) examinations in 147 patients with no signs of pathology related to the lacrimal drainage system. The mean length of the nasolacrimal duct measured 11.2±2.6mm (range: 6–21 mm), the narrowest diameter was 3.7±0.7 mm (range: 2–7 mm). The mean length of the nasolacrimal sac was 11.8±2.5 mm (range: 6–18 mm). The width of the nasolacrimal sac did not exceed 4 mm unless filled with air. In 43 (29.3%) of the subjects air was visible within the nasolacrimal sac or duct. The knowledge of the morphometry of the lacrimal drainage system enables the ophthalmologist to plan intervention on the lacrimal drainage system precisely and avoid unnecessary manipulations.

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Anatomie du sac et du conduit lacrymo-nasaux en tomodensitométrie

Résumé Les récents progrès en ophtalmologie tels que la dilatation par ballonnet, la pose de sondes, les traitements au laser, l'endoscopie du système lacrymal accroissent la nécessité d'une connaissance anatomique précise de ce système ; dans cette étude morphométrique, les mesures du système de drainage lacrymal ont été réalisées par tomodensitométrie en coupes fines (CT); l'étude portait sur 147 patients indemnes de toute pathologie du système de drainage lacrymal. La longueur moyenne du conduit lacrymal était de 11,2±2,6 mm (limites : 6–21 mm) ; le diamètre le plus réduit était de 3,7±0,7 mm (limites : 2–7 mm). La longueur moyenne du sac lacrymo-nasal était de 11,8 mm±2,5 mm (limites 6–18 mm) ; la largeur du sac n'excédait pas 4 mm, en dehors d'un remplissage par l'air. La présence d'air a été décelée dans le sac ou le conduit chez 43 sujets (29,3 %). La connaissance de la morphométrie du système de drainage lacrymal permet à l'ophtalmologiste de planifier avec précision une intervention sur le système en évitant des manuvres intempestives.

     

Ultrastructure of the submandibular gland in the rabbit

The secretory endpieces of the rabbit submandibular gland are unusual in that they consist of seromucous acini (not demilunes) that empty into serous tubules that in turn drain into intercalated ducts. Seromucous granules consist of a moderately dense spherule in a fibrillogranular matrix. Serous granules contain a feltwork of filaments, which are liberated as a tangled skein during exocytosis. Peculiar granulated cells that have secretory granules of complex morphology are present at each end of the serous tubules. Intercalated ducts are, cytologically speaking, relatively simple, but the duct cells may contain a few oblong secretory granules. Striated ducts are typical in structure, although postfixation with ferrocyanide-reduced osmium reveals significant amounts of glycogen in the basal processes. Modified mitochondria are present in striated duct cells, but their frequency varies from rabbit to rabbit. Such mitochondria contain either an array of parallel, rigid cristae linked by intermembranous bridges, or a bundle of helical filaments within an expanded crista. Interspersed with the striated duct cells, especially near the duct origin, are some highly vacuolated cells with sparse mitochondria. Excretory ducts consisting of stratified columnar (sometimes pseudostratified) epithelium often show bleb formation of the luminal surface of the tall cells.     

The amniotic, allantoic and yolk sac epithelia of the cat: SEM and TEM studies

Summary The epithelial layers of the feline allantoamnion and yolk sac between the 23rd day and full term were studied using SEM, TEM, and light microscopical histochemistry. Amniotic, allantoic and yolk sac fluid were analysed. The attenuated and relatively inert amniotic epithelium sloughs off completely around the 54th day, the amniotic cavity is then lined by fibrous connective tissue only. The exocoelomic epithelium is regarded as the source of the abundant macrophages, rich in lysosomal enzymes, that are seen in the allantoamniotic membrane after obliteration of the exocoelomic cleft. The allantoic epithelium has been mistaken for the amniotic one by many authors. Its cuboidal, glycogen-rich cells develop coral-like luminal outgrowths after the 45th day, which contain almost all kinds of organelles. The basal cell poles form large interdigitations, and the nuclei become heavily lobulated. The changes are accompanied by drastic alterations in the ionic composition of the allantoic fluid. The yolk sac endoderm differs greatly from the allantoic endoderm. It is the most active epithelium of the accessory fetal membranes. The yolk sac mesothelium retains many long microvilli over the whole gestational period. The nutritional value of the yolk sac fluid is only higher than that of the amniotic fluid in its glycerol and cholesterol values.     

On the ultrastructure of the parotid and submandibular gland of the mongoose Herpestes edwardsi (Viverridae) (author's transl)

The parotid and submandibular glands of the mongoose are described. Essential differences between the 2 glands were recognized in the acini; however, the intra- and interlobular ducts are built up similarly. The parotid gland is acinar. Its secretory cells are filled with distinct types of granula, which show a considerable variation of size and structure of their secretory material. Organelles are found sparsely. The submandibular gland, however, is tubuloacinar. Its tubuli are capped with cells which belong to the demilunes of v. EBNER, but because of their pale granules they occupy an exceptional position. As the acinar cells of the parotid gland, they form intercellular canaliculi by their plasmalemmata. In the secretory cells of the tubules an intimate contact between the rER and the granules is observed. The intralobular duct surface is built up by an onelayered epithelial cell formation. The cytoplasm of the intercalated duct cells is rich in bundles of filaments, and these cells contain mitochondria with a particular dense matrix. Some microvilli cover the apical surface. In the cells of the striated ducts several populations of granules differing in size and electron density are found. The material of the dense granules shows a marginal plate-like condensation, sometimes it cristallizes. It is supposed that they were released by an apocrine extrusion mechanism. Terminal axons innervate the acini, the duct cells, and also the myoepithelial cells. The findings are compared with the well-known morphology of the salivary glands of the cat.     

Die Wirkung von Kupfer,TTX, Cocain und TEA auf das Ruhe- und Aktionspotential vonNitella

Summary There have been very few studies performed on electrolyte excretion by the isotonic-secreting lacrimal gland and none at all on the composition of its primary secretion. We have attempted both of these on the readily accessible rat exorbital lacrimal gland. From micropuncture studies we find the following electrolyte concentrations in the primary secretion which are unaltered by stimulation of gland secretion with carbachol:[Na]=139 mM±4(S.E.M.); [K]=9.0±1.2 mM; [Cl]=105±3 mM.By using fine-bore (80 m) polyethylene tubing we were able to collect samples of final lacrimal secretion from the gland main duct. Na concentrations were usually similar to those in primary fluid but K concentrations were very high (46±3 mM) and rose at low secretory rates to about 140 mM. Cl concentrations (123±1 mM) were significantly greater than those in the primary secretion and in the interstitial fluid but were independent of secretory rate. HCO₃ concentrations were also independent of secretory rate and averaged 19.6±2 mM.The results show that the lacrimal excurrent duct system plays a role in determining the composition of the final secretion. Contrary to previous studies in human and rabbit lacrimal glands, the present studies on the rat lacrimal reveal flow dependency of the concentrations of some electrolytes which may have been obscured in earlier studies where the slowly flowing lacrimal secretion was allowed to come into contact with the conjunctival epithelium before collection.A preliminary report of this work was presented to the Australian Physiological Society in May, 1972 [1].The research was supported by the National Health and Medical Research Council of Australia.Mr. Alexander held a B.Sc. (med.) studentship from the National Health and Medical Research Council of Australia in 1970–1971 and a Summer Vacation Studentship from the National Heart Foundation of Australia in 1971–1972.     

Ultrastructure of the cat sublingual gland

The sublingual gland of the cat consists primarily of branched secretory tubules that open into an abbreviated duct system. The simple epithelium that composes the secretory tubules consists of an admixture of mucous and serous cells, with the former predominating. Some secretory tubules are capped by a serous demilune. Regardless of position, almost all serous cells have prominent basal folds and border on at least one intercellular canaliculus as well as on the tubule lumen. Serous cells possess an extensive array of irregular, distended cisternae of rough-surfaced endoplasmic reticulum that frequently contain dense intracisternal granules. Serous granules are relatively few in number and rarely show evidence of substructure. Mucous cells, which lack basal folds, contain an apical mass of secretory material in the form of partially fused droplets. The duct system is somewhat less ordered than in most major salivary glands; secretory tubules empty into structures resembling intercalated ducts or may be in direct continuity with ducts intermediate in morphology between intercalated and excretory ducts. The absence of striated ducts noted in this study may be correlated with the high sodium content of cat sublingual saliva. The main excretory duct of the sublingual gland closely resembles that of the cat submandibular gland in terms of morphology, but exhibits little of the transport functions reported in the latter duct.     

Anatomy, histology, histochemistry and fine structure of the Harderian gland in the South American armadillo Chaetophractus villosus (Xenarthra, Mammalia)

The anatomical, histological, histochemical and ultrastructural characteristics of the Harderian gland of the armadillo Chaetophractus villosus were described. The gland is the largest structure in the bony orbit. It is situated in the anteroventral region of the orbit. Obvious structural differences are not observed between males and females. The gland is compound-branched tubulo-alveolar, being characterized by a single layer of columnar cells surrounded by myoepithelial cells. It possesses a single excretory duct opened into the inner canthus. All glandular cells show yellow-green autofluorescence and additionally some glandular lumen may contain dense autofluorescent solid accretions. There are two peculiar and outstanding cytoplasmic features. One is represented by the smooth endoplasmic reticulum (SER), forming a closely woven meshwork. The other one is represented by membranous bodies apparently derived from the SER, RER and cytoskeleton with a Star of David configuration situated in the supranuclear region. Three types of vesicles are detected in the cytoplasm. Histochemical staining methods reveal lipids, proteins, neutral and acidic containing glycoconjugates in secretory vesicles. The mechanism of secretion appears either merocrine or apocrine. The epithelium of the intra- and inter-lobular excretory ducts suggests secretory activity. Tubulo-acinar glands similar to those seen in the lacrimal gland and nictitans glands are found related to the intralobular and main excretory ducts. The capillary network is characterized by fenestrated endothelium. The stroma possesses unmyelinated axons and plasma cells. The normal secretion of the secretory endpieces, particularly lipids, proteins and glycoconjugates, is complemented by mucous and serous secretions released by ductal cells and glands associated to the ducts.     

Ultrastructure of the principal and accessory submandibular glands of the common vampire bat

The principal and accessory submandibular glands of the common vampire bat, Desmodus rotundus, were examined by electron microscopy. The secretory endpieces of the principal gland consist of serous tubules capped at their blind ends by mucous acini. The substructure of the mucous droplets and of the serous granules varies according to the mode of specimen preparation. With ferrocyanide-reduced osmium postfixation, the mucous droplets are moderately dense and homogeneous; the serous granules often have a polygonal outline and their matrix shows clefts in which bundles of wavy filaments may be present. With conventional osmium postifixation, the mucous droplets have a finely fibrillogranular matrix; the serous granules are homogeneously dense. Mucous cells additionally contain many small, dense granules that may be small peroxisomes, as well as aggregates of 10-nm cytofilaments. Intercalated duct cells are relatively unspecialized. Striated ducts are characterized by highly folded basal membranes and vertically oriented mitochondria. Luminal surfaces of all of the secretory and duct cells have numerous microvilli, culminating in a brush borderlike affair in the striated ducts. The accessory gland has secretory endpieces consisting of mucous acini with small mucous demilunes. The acinar mucous droplets contain a large dense region; the lucent portion has punctate densities. Demilune mucous droplets lack a dense region and consist of a light matrix in which fine fibrillogranular material is suspended. A ring of junctional cells, identifiable by their complex secretory granules, separates the mucous acini from the intercalated ducts. The intercalated ducts lack specialized structure. Striated ducts resemble their counterparts in the principal gland. As in the principal gland, all luminal surfaces are covered by an array of microvilli. At least some of the features of the principal and accessory submandibular glands of the vampire bat may be structural adaptations to the exigencies posed by the exclusively sanguivorous diet of these animals and its attendant extremely high intake of sodium chloride.     

Lacrimal Duct Occlusion Is Associated with Infectious Keratitis

Background: To explore the prevalence of lacrimal duct obstruction in patients with infectious keratitis, and the necessity of lacrimal duct dredge in the treatment of human infectious keratitis.Methodology/Principle Findings: The design is prospective, non-control case series. Thirty-one eyes from twenty-eight continuous patients with infectious keratitis were included in this study. The presence/absence of lacrimal duct obstruction was determined by the lacrimal duct irrigation test. The diagnosis of infectious keratitis was made based on clinical manifestations, cornea scraping microscopic examination and bacterial/fungus culture. Diagnosis of viral keratitis was set up based on the recurrent history, deep neovascularization and typical outlook of the cornea scar. The treatment of keratitis included drugs, eye drops or surgery, while treatment of chronic dacryocystitis was lacrimal duct dredging with supporting tube implantation surgery. In the thirty-one eyes with infectious keratitis, fifteen suffered from fungal keratitis (48%), two bacterial keratitis (6%), and fourteen viral keratitis (45%). Eleven eyes (35%) from ten patients with infectious keratitis also suffered from lacrimal duct obstruction. In those cases, six eyes also suffered from lower canalicular obstruction, three nasolacrimal duct obstruction and chronic dacryocystitis, one a combination of upper and lower canalicular obstruction, one upper canalicular obstruction. After local and systemic applications of anti-bacterial, anti-viral, anti-fungal and anti-inflammatory drugs, twenty-eight eyes (90%) recovered within three weeks, while the ulceration of three patients required the lacrimal duct dredging and supporting tube implantation surgery for the healing.Conclusions: Herein, we first report that the prevalence of infectious keratitis is closely correlated to the occurrence of lacrimal duct obstruction. When both confirmed, simultaneous treatment of keratitis and lacrimal duct obstruction promptly is required. Further evaluation of mechanism, prevention and control of the diseases are warranted.     

IgA plasma cells in biliary mucosa: a likely source of locally synthesized IgA in human hepatic bile

IgA synthesized in hepatobiliary tissues accounts for about one-half of the IgA present in human hepatic bile, but the location of the IgA synthesizing cells has been in doubt because few plasma cells are present in normal liver. Therefore, we immunocytochemically localized IgA, J chain and secretory component in bile duct tissues of six patients operated upon for biliary duct obstruction. Numerous plasma cells containing IgA and J chain were found surrounding the accessory glands of the major bile ducts and in the area just beneath the surface epithelium of the ducts. At the ultrastructural level, IgA and SC in the epithelial cells had the features characteristic of secretory component-mediated endocytic translocation of IgA. We conclude that plasma cells in biliary duct mucosa are the likely source of much of the locally synthesized IgA that is secreted into human hepatic bile. The IgA probably reaches the bile by direct transfer across biliary epithelium.     

Brunner's glands of the duckbilled platypus (Ornithorhynchus anatinus)

Brunner's glands in the platypus form a lobulated, glandular collar confined to the submucosa of the most distal portion of the stomach. The glands end immediately proximal to the gastrointestinal junction and excretory ducts empty in the region where the stratified squamous epithelium lining the stomach changes abruptly to the intestinal lining epithelium of the duodenum. An individual gland of Brunner is composed of several elongate lobules drained by intralobular ducts which often join to form a single excretory duct. Light and electron microscopic studies have shown the secretory tubules to be comprised of large, pyramidal cells limited basally by a delicate basal lamina. The ergastoplasm, cisternae of which are dilated and contain amorphous material, is associated with numerous ribosomes. In basal and perinuclear regions intercisternal granules and smooth surfaced vesicles are found. Numerous small vesicles found in supranuclear areas apparently form from the smooth membrane portions of ergastoplasm located adjacent to Golgi complexes. Membrane-bound amorphous granules of varying electron density occupy the apical cytoplasm and show a tendency to coalesce before emptying their contents into the adjacent lumen. The intralobular duct system is lined initially by a columnar epithelium which changes to a simple squamous form before the ducts combine to form a short excretory duct lined by stratified squamous epithelium. The epithelium lining the duct system contains relatively few organelles but appears to be engaged in a limited amount of synthesis and release of secretory material. Histochemical studies indicate that both the secretory tubules and the duct system elaborate a neutral mucopolysaccharide.     

Age-related alterations in the lacrimal gland of adult albino rat: A light and electron microscopic study

BackgroundAge related changes in the lacrimal gland are associated with alterations in the structural organization and functional response in the gland of diverse mammalian species. Dry eye syndrome is one of the most common ocular problems in the world especially in old age. It results when the lacrimal gland fails to secrete proteins and fluid in sufficient quantity or appropriate composition.Aim of the workThe present study is designed to demonstrate the influence of aging on the structure of the lacrimal gland of albino rat and to provide a morphological basis to explain the pathogenesis of the dry eye syndrome with ageing. It also aims to carry out a comparative analysis of age-dependent changes in male and female rats and to address how the lacrimal gland ages in each sex.Material and MethodsEighty albino rats were used in this study. The animals were divided into two age groups, young adult and senile. Tear secretion was measured using a modified Schirmer test. Corneal impression cytology of the anesthetized rats was done. The glands were subjected to gross morphologic examination, microscopic examination using H&E, PAS, Masson's trichrome and Giemsa stains. Electron microscopic examination was done in addition to quantitative histomorphometric estimations included acinar density, ductal count and mast cell count.ResultsLight microscopic examination of the lacimal glands of the senile rats revealed different pathological changes. These included acinar, ductal as well as stromal changes. Electron microscope examination of the lacrimal gland of the senile group showed a decrease in the electron dense secretory vesicles, mitochondrial swelling and lipofuscin-like inclusions were frequently seen in the cytoplasm of acinar cells in senile rats.ConclusionThe structural changes in the lacrimal glands of senile rats were associated with reduction in tear secretion as well as alterations in corneal epithelium. Gender difference in lacrimal gland structure was recorded.