Modern man knows a lot about how his body functions. But it is worth remembering that in addition to large vital systems, there are small organs and glands. They are located throughout the body and play a significant role in the general condition of the body. An example is the lacrimal canals, on the work of which the condition of the eyes depends.
What is a gland?
Gland is an organ that consists of secretory cells. It serves to produce specific substances that are different in chemical nature. The gland can remove the produced secret to the outside or to the internal environment of the body. Examples of these organs include human lacrimal canals, endocrine glands, pancreas.
The organs that bring the secret out are called exocrine. Glands that produce a synthesized secret into the circulatory or lymphatic system are called endocrine glands.
The human lacrimal glands. Location
Look for the lacrimal glands just below the upper outer edge of the orbit. Specially for them in the frontal bonea lacrimal fossa was formed in the form of a shallow recess. To prevent the gland from shifting, there are fibrous cords, that is, supporting the muscles of the eye and eyelids, in addition they are held by fatty tissue. On average, in an adult, these organs measure 10x20x5 mm. One iron weighs no more than 0.8 g.
Building
The structure of the lacrimal gland is alveolar-tubular. It is formed by two unequal shares:
- orbital, which is located on top and slightly larger in volume;
- palpebral, which is called the lower lobe.
Between the lobes in which tear fluid is produced, there is an aponeurosis of the muscle responsible for lifting the upper eyelid. From each of them there are 5-6 ducts. Gradually, they are combined into one large duct.
The lower part of the gland has a gate. Arteries and veins pass through them, supplying the organ with blood, lymphatic vessels and the main duct of the gland, in which all the small tear ducts converge. The lumen of the duct is open into the conjunctiva. Its exit is located on the outer part, approximately 5 mm from the extreme point of the upper eyelid. Sometimes there is a departure of additional excretory tracts. These small ducts also terminate at the fornix of the conjunctiva. Some ducts carry the lacrimal fluid into the temporal region of the conjunctiva, some into the outer corner of the palpebral fissure. When a person closes their eyes, tears flow down the back of the eyelids, where the lacrimal stream is located, and through the lacrimal lake into the small openings at the edges of the eyelids.
The upper duct, which runs next to the orbit along the bone fossa, is called the lacrimal sac. Its walls give rise to numerous pathways through which tear fluid flows.
The lower part of the lacrimal gland lies in the subaponeurotic area under the lower eyelid. It consists of numerous connecting lobules. Usually there are 25-30 of them. All ducts from the lobules lead to the main gland.
A large nasolacrimal duct passes through the bone base of the outer wall of the nasal cavity. This lacrimal canal opens into the nasal cavity with a special gap in the region of the lower concha. The slit is covered with a flap made from a fold of mucous membrane.
Functions
The lacrimal glands produce a special fluid secretion that has many functions:
- removal of foreign bodies and dirt from the eye;
- surface drying protection;
- delivery of nutrients to the conjunctiva and cornea;
- refraction of light;
- lubrication when moving the eyelid;
- antibacterial protection.
What is a tear?
Tear fluid is a clear transudate that accumulates in serous (protein) cavities. In the chemical composition of tears, coincidences with the composition of blood are observed. However, they have a higher concentration of potassium and fluorine and a lower content of organic acids. The chemical composition of tears reacts to the state of the body and is constantly changing.
The basis of tear fluid is water. S alt (1.5% NaCl), albumin (0.5%), mucus are dissolved in it. On examination, she appears slightly alkaline.reaction. Tears can be reflexive and emotional. In the first case, the body uses the released tear to moisten and cleanse the eye. In the second case, to relieve tension and anxiety. The secretory cells of the lacrimal glands produce a small amount of a psychotropic substance that can bring relief in stressful situations. In a state of despair, the stress hormones leucine-enkephalin and prolactin appear in tears. Happy tears reduce the amount of adrenaline, which increases dramatically when overexcited. In addition, secretory cells provide the composition of the lacrimal fluid with the presence of immunoglobulins, numerous proteins, amino acids, enzyme substances, urea and other chemical elements.
Since now you have a rough idea of what tear fluid is, you understand that the ability to cry is very important for a person. Tears are not only a sign of an increased emotional background, but also an assistant to our eyes, keeping them he althy.
