(histology described applies to nasolacrimal duct)
Rabbit
Ape
Pig
Cat

Single punctum on inner lid surface 3mm from medial canthus with short canaliculus (2mm) that opens into lacrimal sac.

Sac was slightly dilated, funnel shaped portion of duct

Average duct length 58.8 mm with variable diameter.

Duct exits within nasal vestibule several mm posterior to
 mucocutaneous junction at the alar fold

Single, large, inferior nasolacrimal punctum opens to a
 tortuous nasolacrimal duct of variable diameter

Single inferior punctum 3mm from inferior palpebral margin empties into sac.

Sac marks caudal and dorsal extremities of NLD apparatus

Duct courses rostroventromediad through nasolacrimal canal and exits just caudally to the mucocutaneous junction of the nares.

Cavernous body surrounds lacrimal sac and duct

Duct drains into inferior meatus of nasal cavity


Sac and duct lined with stratified or pseudostratified columnar epithelium with numerous goblet cells.

Submucosa composed of loose connective tissue with abundant capillaries and lymphatics.

Opening of duct into nasal vestibule transitions from columnar to stratified squamous cells.

Duct lined with stratified squamous epithelium.


Sac epithelium had a two-layered columnar appearance.

No goblet cells seen.

Sac and duct lined by single, stratified to pseudostratified columnar epithelium.

Numerous mucus-containing cells.

Proximal duct epithelium had villous folds.

Submucosa had abundant capillaries, lymphatics, and other components of loose connective tissues.


Same histology as ape.

Epithelial cells covered with microvilli (200-400 nm in length, 60-70 nm in diameter) shown by scanning electron microscopy.

Double-layered epithelium with mucin-secreting epithelial cells organized in cell groups lacking goblet cells, intraepithelial mucous glands (IMG) or subepithelial seromucous glands (SSMG).

Surrounding cavernous body (SCB) present.

Double-layered epithelium with mucin-secreting epithelial cells, SCB and SSMG, but lacking goblet cells or IMG.

Double-layered epithelium with many goblet cells but lacking IMG, SSMG or SCB.

Deer
Rat
Cat
Dog
Sheep
Goat
2 short haired domestic
14 different breeds
20
4

Duct exits below the posterior part of the inferior turbinate into the nose

Upper and lower canaliculi roughly equal in length (6-10 mm) and diameter (0.7-1.0 mm).

Sac roughly triangular, 5mm long, proximal diameter
3mm and distal diameter of 1mm

Duct 2.5-4cm long, diameter 0.7-1.5mm, proximal 1/3 smaller than distal 2/3.

Upper and lower canaliculi that consolidate into poorly developed sac

Duct has 2 distal openings, with reduced diameter in proximal third.

Dimensions of drainage system vary considerably between species

No distinct sac; just conjoining of superior and inferior canaliculi.

Duct opens 2 cm posterior to external nares on lateral
 floor of nasal cavity.

Double-layered epithelium with SCB but no goblet cells, IMG or SSMG.

Multilayered epithelium with goblet cells and
IMG lacking SSMG and SCB.

Ducts lined with multilayered epithelium consisting of larger squamous cells above and
 cuboidal cells below.


Canaliculi lined by continuous layer of
 nonkeratinized squamous epithelium.

2 parts; orbit and nasal cavity portions.

Orbital part: two lacrimal puncta, two canaliculi (7mm long), and lacrimal sac.

Distinct sac (6mm long by 5 mm wide): more expanded than duct but smaller than human sac.

Nasal cavity: formed by duct leaving the sac in the orbit and entering osseous lacrimal canal where it exits on lateral wall of the nostril.

Total duct length 105-113 mm

Similar to goat.

Upper and lower puncta, with corresponding canaliculi that converge toward medial commissure

Sac receives both canaliculi laterally and empties into duct which passes through the osseous lacrimal canal, parallels the middle meatus, and exits through the terminal fold of the ventral turbinate and opens on the nasal mucous membrane above the nostril.


Similar to goat.
Punctal margin lined with stratified squamous epithelium on eyelid border, and typical conjunctival epithelium adjacent.

Lacrimal passage epithelium: (1) stratified squamous in proximal portion of canaliculi, (2) stratified cuboidal to columnar in middle and distal regions of canaliculi, (3) stratified and pseudostratified columnar with goblet cells in lacrimal sac, and nasolacrimal duct.


No puncta

Funnel shaped sac with 1 or 2 one cm canaliculi ending blindly 0.5 cm from the medial canthus 1 mm from upper or lower lids.

Sac continuous with duct, 3-4 mm wide and 20 cm long, opens with discrete oval orifice on anterior aspect of nasal mucous membrane.

Upper and lower puncta 8-9 mm from medial canthus with corresponding canaliculi

Sac identifiable only as a slight dilation at the convergence of canaliculi before continuing as duct

Duct narrows before its exit from the bony maxilla in the lateral wall of middle nasal meatus and continues gentle spiraling course until emptying onto floor of the nasal vestibule at the mucocutaneous junction

Duct length 24-29 cm with 2-11 mm variable diameter

Ventral and dorsal puncta 4-6 mm from medial canthus, with paired canaliculi 2-4 mm in length that converge into rudimentary sac.

Duct length 11-15 cm with 2-4 mm uniform diameter that opens on floor of nasal cavity.



Few seromucous glands surrounding lower third of nasolacrimal duct.

Lamina propria of lacrimal sac and nasolacrimal duct contained abundant venous plexus resembling erectile tissue.

Sac lined by several layers of stratified columnar epithelium with goblet cells.

Duct lined by stratified columnar epithelium with basal layer rich in melanin granules and goblet cells present in middle portion increasing in number through terminal portion.