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Goblet cells are simple columnar goblet shaped like epithelial cells that secrete gel-forming mucins, like mucin MUC5AC. The goblet cells mainly use the merocrine method of secretion, secreting vesicles into a duct, but may use
apocrine Apocrine () is a term used to classify exocrine glands in the study of histology. Cells which are classified as apocrine bud their secretions off through the plasma membrane producing extracellular membrane-bound vesicles. The apical portion of ...

apocrine
methods, budding off their secretions, when under stress. The term ''
goblet A chalice (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Rom ...
'' refers to the cell's goblet-like shape. The apical portion is shaped like a cup, as it is distended by abundant mucus laden granules; its basal portion lacks these granules and is shaped like a stem. The goblet cell is highly polarized with the nucleus and other organelles concentrated at the base of the cell and secretory granules containing mucin, at the apical surface. The apical plasma membrane projects short to give an increased surface area for secretion. Goblet cells are typically found in the respiratory, reproductive and gastrointestinal tracts and are surrounded by other columnar cells. Biased differentiation of airway basal cells in the respiratory epithelium, into goblet cells plays a key role in the excessive mucus production, known as mucus hypersecretion seen in many respiratory diseases, including chronic bronchitis, and
asthma Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, cou ...
.


Structure

Goblet cells are found scattered among the epithelial lining of organs, such as the intestinal and
respiratory tract The respiratory tract is the subdivision of the respiratory system The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animal ...

respiratory tract
s. They are found inside the
trachea The trachea, also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lung The lungs are the primary organs of the respiratory system in human Humans (''Homo sapiens'') are the most populous ...
, bronchi, and larger bronchioles in the respiratory tract, small intestines, the large intestine, and conjunctiva in the upper eyelid. In the conjunctiva goblet cells are a source of mucin in tears and they also secrete different types of mucins onto the ocular surface. In the lacrimal glands, mucus is biosynthesis, synthesized by Acinus, acinar cells instead.


Microanatomy

Goblet cells are simple columnar epithelium, simple columnar epithelial cells, having a height of four times that of their width. The cytoplasm of goblet cells tends to be displaced toward the basal end of the cell body by the large mucin granules, which accumulate near the Cell membrane#Membrane polarity, apical surface of the cell along the Golgi apparatus, which lies between the granules and the cell nucleus, nucleus. This gives the basal part of the cell a basophilic staining because of nucleic acids within the nucleus and Endoplasmic reticulum#Rough endoplasmic reticulum, rough endoplasmic reticulum staining with hematoxylin. Mucin within the granules stains pale in routine histology sections, primarily because these carbohydrate-rich proteins are washed out in the histology#Sample preparation, preparation of microscopy samples. However, they stain easily with the Periodic acid–Schiff stain, PAS staining method, which colours them magenta. In mucicarmine stains, deep red mucin is found within goblet cell bodies. Goblet cells can be seen in the examples below as the larger, more pale cells. File:Gray1062.png, An intestinal gland from the human intestine with goblet cells visible File:Gobletcell.jpg, Goblet cell in ileum File:MultiPhotonExcitation-Fig10-doi10.1186slash1475-925X-5-36.JPEG, Section of mouse intestine, mucus of goblet cells in blue File:Goblet cells.jpg, Goblet cells in large intestine


Function

The main role of goblet cells is to secrete mucus in order to protect the mucous membranes where they are found. Goblet cells accomplish this by secreting mucins, large glycoproteins formed mostly by carbohydrates. The gel-like properties of mucins are given by its glycans (bound carbohydrates) attracting relatively large quantities of water. On the inner surface of the human intestine, it forms a 200 micrometre, µm thick layer (less in other animals) that lubricates and protects the wall of the organ. Distinct forms of mucin are produced in different organs: while MUC2 is prevalent in the intestine, MUC5AC and MUC5B are the main forms found in the human respiratory tract, airway. In the airway, mucus is swept by the Cilium, cilia of the respiratory epithelium, in a process called mucociliary clearance, and propelled out of the lungs and into the pharynx, which results in the removal of debris and pathogens from the airway. MUC5AC is overexpressed in allergic lung inflammation. Mucins are continuously made and secreted by goblet cells in order to repair and replace the existing mucus layer. Mucins are stored in granules inside the goblet cells before being released to the lumen (anatomy), lumen of the organ. Mucin secretion in the airway may occur via regulated secretion. Secretion may be stimulated by irritants such as dust and smoke, especially in the respiratory tract, airway. Other stimuli are microbes such as viruses and bacteria. Anomalies in the number of goblet cells are associated with changes in the secretion of mucins, which can result in many of the abnormalities seen in asthma patients, such as clogged airways due to mucus hypersecretion, and eventual loss of lung function. Overexpression of MUC5AC alone does not result in the pathophysiology seen in
asthma Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, cou ...
patients; it is the excessive production along with the speed of secretion that leads to the formation of thick mucus that cannot be removed by cilia or coughing action. This, in addition to airway narrowing leads to the clogging of the airways, which can be detrimental to health if not treated.   There are other cells that secrete mucus (such as the foveolar cells of the stomach) but these are distinguished histology, histologically from goblet cells.


Role in oral tolerance

Immune tolerance#Acquired tolerance, Oral tolerance is the process by which the immune system is prevented from responding to antigen derived from food products, as peptides from food may pass into the bloodstream via the gut, which would in theory lead to an immune response. A paper published in ''Nature'' in 2012 has shed some light on the process and implicated goblet cells as having a role in the process. It was known that CD103-expressing dendritic cells of the lamina propria had a role to play in the induction of oral tolerance (potentially by inducing the differentiation of regulatory T cells), and this paper suggests that the goblet cells act to preferentially deliver antigen to these CD103+ dendritic cells.


Clinical significance


Allergic asthma

The excessive mucus production seen in allergic asthma patients is due to goblet cell metaplasia, the differentiation of airway epithelial cells into mucin producing goblet cells. These cells produce the thick mucins MUC5AC and Mucin 5B, MUC5B, which clog the airway, leading to the airflow obstruction characteristic of
asthma Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, cou ...
. Goblet cell metaplasia in allergic asthma is due to the action of the cytokine Interleukin 13, IL-13. Interleukin 13, IL-13 binds to the Interleukin-4 receptor, IL-4Rα receptor and initiates a STAT6 signalling response. Binding of Interleukin 13, IL-13 causes phosphorylation of tyrosine residues at the Interleukin-4 receptor, IL-4Rα. This results in docking of STAT6 monomers, which themselves are phosphorylated and then subsequently leave the receptor and congregate form STAT6 Protein dimer, homodimers in the cytoplasm. These homodimers then enter the Cell nucleus, nucleus, where they bind to regulatory elements in the DNA, which affects the Transcription (biology), transcription of certain genes involved in mucus production. Induction of STAT6 signaling by Interleukin 13, IL-13 leads to increased of expression of ALOX15, 15-lipoxygenase (15-LO-1), which is an enzyme involved in the breakdown of unsaturated fatty acids. 15-lipoxygenase acts by binding to phospholipids and yields hydroperoxy and epoxy metabolites. One such metabolite, 15-Hydroxyeicosatetraenoic acid, 15-hydroxyeicosatetranoic acid (15-HETE), is released intracellularly, where it conjugates to phosphatidylethanolamine, a phospholipid component. 15-HETE-PE induces expression of the mucin MUC5AC.


Goblet cell carcinoids

Goblet cell carcinoids are a class of rare tumors that form as a result of an excessive proliferation of both goblet and neuroendocrine cells. The majority of these tumors arise in the vermiform appendix, appendix and may present symptoms similar to the much more common acute appendicitis. The main treatment for localized goblet cells tumors is appendectomy, removal of the appendix, and sometimes colectomy, removal of the right hemicolon is also performed. Disseminated tumors may require treatment with chemotherapy in addition to surgery.


Metaplasia

Barrett's esophagus is a metaplasia of the esophagus into intestinal epithelium, characterized by the presence of goblet cells.


Treatments


Monoclonal antibodies

Studies of mice given monoclonal Antibody, antibodies for Interleukin 13, IL-13 results in decreased expression of goblet cells in
asthma Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, cou ...
patients. Some treatments that use anti-IL-13 monoclonal antibodies include tralokinumab, and lebrikizumab. These treatments have shown improvements in asthma patients, yet there are still limitations to the use of anti-IL-13 monoclonal antibodies. Dupilumab is a newer drug that targets the shared receptor of Interleukin 4, IL-4 and Interleukin 13, IL-13, Interleukin-4 receptor, IL4Rα. Since IL-4 and IL-13 have interrelated biological activities, Dupilumab is a more effective form of treatment as it targets both interleukins.


History

The cells were first noted by Friedrich Gustav Jakob Henle, Henle in 1837 when studying the lining of the small intestine, seen to be mucus producing by Franz Leydig, Leydig in 1857 (who was examining the epidermis of fish), and were given their name by Franz Eilhard Schulze, Schulze in 1867, Schulze chose the descriptive name "goblet" because of the shape of the cell, rather than a functional name, as he remained uncertain as to the mucous-producing function of the cell. Nowadays these cells are used in the laboratories to evaluate the intestinal absorption of drug targets with different kits, such as the CacoGoblet.


See also

*List of human cell types derived from the germ layers


References


External links


Goblet Cells at cvmbs.colostate.edu
{{Authority control Mucus secreting cells Epithelial cells Human cells