Head and Neck
Rui Diogo, Drew M. Noden, Christopher M. Smith, Julia Molnar, Julia C. Boughner, Claudia Barrocas, Joana Bruno in Understanding Human Anatomy and Pathology, 2018
The tarsal glands are embedded in the posterior surface of each tarsal plate, the fibrous “skeleton” of the upper eyelid. The orbital septum is a sheet of connective tissue separating the superficial facial fascia and the contents of the orbit. The tarsal glands drain by orifices lying posteriorly to the eyelashes and secrete an oily substance onto the margin of the eyelids that prevents the overflow of tears (lacrimal fluid). The lacrimal gland lies in the lacrimal fossa of the frontal bone. The lacrimal sac lies posterior to the medial palpebral ligament, which is attached to the anterior lacrimal crest that forms the anterior border of the lacrimal groove (Plate 3.32). The lacrimal sac receives lacrimal fluid from the medial angle of the eye through the lacrimal canaliculi. When lacrimal fluid accumulates in excess and cannot be removed from the medial corner of the eye via the lacrimal canaliculi, it overflows the eyelids (visible crying or shedding of tears). Tears also drain into the nasal cavity via the lacrimal sac, resulting in a runny nose.
Lacrimal Disorders in Children
John C Watkinson, Raymond W Clarke, Christopher P Aldren, Doris-Eva Bamiou, Raymond W Clarke, Richard M Irving, Haytham Kubba, Shakeel R Saeed in Paediatrics, The Ear, Skull Base, 2018
The lacrimal system consists of a secretory portion and a drainage system. The secretory portion is made up of the lacrimal and accessory lacrimal glands which, together with the Meibomian glands and the goblet cells, secrete the components of the tear ï¬lm. The accessory lacrimal glands produce basal tear secretion, and the lacrimal gland is largely responsible for reflex tearing in response to noxious or emotional stimuli. The drainage system consists of the lacrimal puncta, canaliculi, lacrimal sac and nasolacrimal duct (Figure 25.1). This active system pumps tears from the conjunctival sac into the inferior meatus of the nose. Clinical problems with the lacrimal system in children usually relate to the reduced drainage of tears. The underproduction of tears, causing dry eyes, is rare but more serious due to the potential for sight-threatening consequences.
Anatomy and Physiology of the Autonomic Nervous System
Kenneth J. Broadley in Autonomic Pharmacology, 2017
The lacrymal or tear glands are located under each upper lateral eyelid. The tears pass through lacrymal ducts into the conjunctival sac under the upper eyelid. They flow across the eye and drain into two small lacrymal ducts on either side of the inner canthus. These remove excess tears into a lacrymal sac which is a dilated portion of the nasolacrymal duct running into the nasal cavity. Hence excessive production of lacrymal secretion due to irritation or allergy (eg hay fever) often results in the need to blow the nose. When the production of lacrymal secretion exceeds the drainage capacity, tears become visible.
Mapping Resident Immune Cells in the Murine Ocular Surface and Lacrimal Gland by Flow Cytometry
Published in Ocular Immunology and Inflammation, 2023
Baikai Ma, Yifan Zhou, Yuzhe Hu, Hongyu Duan, Zhengze Sun, Pingzhang Wang, Wei Li, Wenling Han, Hong Qi
The core ocular surface is composed of the global cornea, limbus and conjunctiva,1 providing the first barrier of the eye and promising sharp vision. Lacrimal gland, the pivot of lacrimal function unit,2 secretes the majority of aqueous tears and actively participate in ocular surface immune responses. The mucosa localized ocular surface immune system is central to maintaining a normal ocular surface microenvironment in terms of host protection and immune tolerance,3 as well as promoting pathogenic inflammation in specific conditions such as dry eye disease.4 The ocular surface immune system is delicate and complex, including tissue resident immune cells, epithelial cells, stromal cells, goblet cells, matrix and immune molecules in tear film such as interleukins and chemokines.5 Tissue resident immune cells take the core position in maintaining ocular surface immune homeostasis and mediating immune-related ocular diseases. Therefore, clarifying the resident immune cells in ocular surface tissues and lacrimal gland is the bedrock of ocular surface immunology.
Towards Lacrimal Gland Regeneration: Current Concepts and Experimental Approaches
Published in Current Eye Research, 2020
Jana Dietrich, Stefan Schrader
The lacrimal gland is a mainly serous, tubule-acinar gland. Histologically, it is composed of acinar cells, which are arranged in individual functional units (the acini) and surrounded by ductal and myoepithelial cells (Figure 1). The acinar cells are responsible for the production and secretion of the primary lacrimal fluid2, which is then conducted onto the ocular surface. On the ocular surface, the tear film is formed and improves the optical properties of the ocular surface by generating a smooth surface on the corneal epithelium, moistening and nourishing the epithelial cells of the conjunctiva and cornea, removing dust and debris and protecting against pathogens.3 The lacrimal fluid with its complex composition of inorganic salts, immunoglobulin A and various proteins is important for this purpose.4 Consequently, an interruption of lacrimal gland homeostasis resulting in a disturbance of the physiological composition and/or quantity of lacrimal fluid, may lead to the development of ADDE.
Vitamin D Replacement Improves Tear Osmolarity in Patients with Vitamin D Deficiency
Published in Seminars in Ophthalmology, 2018
Muhammed Kizilgul, Seyfullah Kan, Ozgur Ozcelik, Selvihan Beysel, Mahmut Apaydin, Bekir Ucan, Erman Cakal
Vitamin D deficiency is a common health problem worldwide. Many authors agree that a 25-hydroxy vitamin D (25(OH)D3) concentration of less than 20ng/ml is defined as vitamin D deficiency; however, a 25(OH)D3 level between 21–29 ng/mL is defined as vitamin D insufficiency.6 Dry eye is also a common health problem. An adequate tear film is required for maintaining the health and function of the eye. Sufficient production of tears, retention on the ocular surface, and balanced elimination are necessary for normal tear film vitality.7 Tears are produced mainly by the lacrimal gland under the control of the parasympathetic and sympathetic innervation.8 Recently, Lu et al. demonstrated lacrimal and accessory glands responsible for producing tear fluid containing megalin and cubilin, which are involved in vitamin D transport.9 Tear hyperosmolarity is described as an increased number of particles in the tear and is a crucial step in the development of dry eye disease.10 The principal mechanism of ocular surface inflammation, symptoms, and tissue damage is considered to be caused by tear hyperosmolarity.11
Related Knowledge Centers
- Adrenocorticotropic Hormone
- Antibody
- Crying
- Enkephalin
- Eye
- Lacrimal Gland
- Lysozyme
- Immune System
- Salt
- Lacrimal Lake