What Is the Lacrimal Apparatus?

Eye aid. It consists of lacrimal glands that secrete tears and lacrimal ducts that drain tears. The lacrimal gland is the size of the thumb cap and is located on the upper and outer side of the eye socket. It often secretes tears. Tears not only scrub the surface of the eyeballs to keep them clean, but also keep the cornea moist.

Eye aid. It consists of lacrimal glands that secrete tears and lacrimal ducts that drain tears. The lacrimal gland is the size of the thumb cap and is located on the upper and outer side of the eye socket. It often secretes tears. Tears not only scrub the surface of the eyeballs to keep them clean, but also keep the cornea moist.

Chinese name

Tears

Foreign name

Tears

lie in

Tears at the medial end of the upper and lower eyelid margins

Respectively

Tears up and down

Tears Overview

Lysozyme in tears can inhibit the growth and reproduction of bacteria and protect the eyes. Lacrimal ducts include lacrimal canals, lacrimal sacs, and nasolacrimal ducts. The tear fluid flows from the excretory duct of the lacrimal gland to the opening of the lacrimal gland on the conjunctiva, flows through the surface of the eyeball and concentrates into the inner and lower lacrimal ducts, and the upper and lower lacrimal ducts merge into the lacrimal sac. The lacrimal sac is located in the fossa of the lacrimal sac, and the lower end is the nasolacrimal duct, which is in communication with the nasal cavity. The lacrimal gland not only secretes tears when crying and laughing, but also constantly secretes, but the secretion is small, flowing from the nasolacrimal duct into the nasal cavity, which is not easy to attract attention. If the lacrimal passage is narrowed or blocked, the eyes are always teary, which is called tear overflow.

Lacrimal organ development

1. Development of lacrimal glands ^[1] :

All conjunctival glands (including lacrimal glands) are formed by surface ectodermal invagination. The lacrimal gland is formed by the conjunctival epithelial cells of the temporal superior fornix immersed in the mesoderm tissue. The lacrimal gland primordia can be seen when the embryo is 30 to 50 mm long, and when the embryo is 50 to 55 mm long, the cells in the central part of the lumpy structure collapse and begin to form glands and excretory lumen. Due to the development of the levator levator tendon, the lacrimal gland is divided into two parts. The orbital lacrimal gland appears earlier and the eyelid lacrimal gland appears later. At 28 weeks of the embryo, secretory granules can be seen in lacrimal gland cells. Until 10 months of the fetus, there are still many immature glandular cells. The lacrimal glands are not fully developed at birth. Usually, the lacrimal glands do not develop until 3 to 4 years old. complete. The para-lacrimal gland is also proliferated after conjunctival epithelial cells sink into the mesodermal tissue, which occurs later. Krause glands began to form when the embryo was 70 to 95 mm long; Wolfring glands began to occur when the embryo was 82 to 120 mm long. Secretory particles were visible in the para-lacrimal glands at 9 months of embryonic age, and development was not completed at birth.

2. The normal development of the lacrimal duct :

The development of the lacrimal duct is related to the development of the lateral nasal process, maxillary process, and eyelid. At the 6th week of the embryo, the maxillary process grows forward and contacts the medial and lateral nasal processes to form the embryo face. At this time, the surface ectodermal tissue sags between the lateral nasal process and maxillary process to form a groove-like structure (nasolacrimal groove), and the development of the lacrimal passage is gradually formed by this groove. Thereafter, the nasolacrimal sulcus was separated from the surface epithelium and gradually deepened, forming a thick irregular cell cord in the mesodermal leaf tissue, which was buried under the surface tissue, and this cell cord was the primordium of the lacrimal duct. Some people also found that at the end of the 6th week, there was an epithelial cell cord extending from the immature nasal cavity toward the lower end of the aforementioned cell cord to form a columnar cell structure. Later, a cavity was formed in the center of the cell column and became a lacrimal duct. The cell cord grows up into the eyelids, forming the upper and lower lacrimal ducts, and when it grows downward, it enters the nose to form the nasolacrimal duct. Some people think that the upper and lower lacrimal canaliculi originated from the same cell cord, and first develop into the lower lacrimal canaliculus, and then form the upper lacrimal canaliculus from the lower lacrimal canaliculus; others believe that the upper and lower lacrimal canaliculi occur independently. The lacrimal canaliculus formed a tube at about 3 to 4 months of the embryo, and the opening of the eyelid margin had not yet formed at 7 months of the embryo. After the formation of the upper and lower lacrimal canaliculi, the lacrimal sac and nasolacrimal duct also gradually formed. The upper end of the nasolacrimal duct is thickened to form the primordium of the lacrimal sac, and the cavity formed in the center of the cell cord of the nasolacrimal duct is initially a number of discrete short tubes. When the embryo is 6 to 7 months, Several short pipes communicate to form a pipe. When the embryo is 60 mm long, all the lacrimal ducts have formed ducts except for the upper and lower punctum and nasolacrimal duct opening. At the 7th month of the embryo, the tear spots were opened, and at the 8th month of the embryo, the lower nasolacrimal duct was opened, and the lacrimal duct was completely unobstructed before birth. There are also some nasal lacrimal duct openings that have not been developed at birth. ^[2] .

Abnormal development of lacrimal organs

1.Congenital lacrimal glands :

Rarely, because the lacrimal gland originates from the epithelium of the superior fornix conjunctiva, no lacrimal gland is more common in patients with congenital abnormalities such as no conjunctiva and no eyeball.

2. Congenital lacrimal gland prolapse and ectopic lacrimal glands :

Rarely, it is caused by developmental defects such as orbital septum and fascia, which causes the lacrimal gland to protrude from the eyelid subcutaneously, causing the upper eyelid to bulge laterally, and prolonged prolapse will cause the eyelid skin to relax and redness. The lacrimal gland is reset and the orbital septum and other fascial tissues are effectively treated by surgery. Ectopic lacrimal gland refers to the location of the lacrimal gland outside the fossa of the lacrimal gland, which is more common on the outside of the eyeball and under the conjunctiva. Rarely can occur in the eye such as the iris and choroid. Can be used for surgery to remove ectopic lacrimal glands.

3. Absence or atresia of congenital lacrimal tubules and punctum :

Rarely, it is because the upper end of the lacrimal primordium fails to differentiate, or even if it does not, no duct is formed. Among them, simple lower lacrimal atresia is more common, the lacrimal duct is normal, the surface opening is covered by epithelium, and it can also show a very small opening or complete occlusion, and it is mostly hereditary. Sometimes it can also show extra puncta and lacrimal ducts, such as deformities such as two lower lacrimal ducts and lacrimal ducts at one glance.

4. Congenital atresia of nasolacrimal duct :

It is very common clinically, due to developmental defects in the process of lacrimal duct differentiation and formation of pipes. About 6% of term infants have a nasolacrimal duct that is not fully open. Most of them are caused by obstruction of epithelial debris in the lower mouth of the nasolacrimal duct, or wrinkles and mucosal diverticula in the epithelial layer of the duct, and a few are caused by bony nasolacrimal duct obstruction. Most of the laparotomy can be cured.

5. Congenital lacrimal fistula :

More commonly, it is caused by developmental variation, which may be related to excessive growth of the lower end of the lacrimal sac. It is also believed that the skin is invaded and formed by pipeline afterwards. The most common site is the inferior lateral of the medial condylar ligament, that is, the lateral side of the nose. Can be unilateral or bilateral, often shed fluid, some discharge mucus purulent discharge, if the fistula is small, the symptoms are easy to be ignored. The treatment is surgical removal of the fistula, but the lacrimal duct must be kept open.