SBA Answers and Explanations
Vivian A. Elwell, Jonathan M. Fishman, Rajat Chowdhury in SBAs for the MRCS Part A, 2018
Goblet cells are mucus-secreting cells, widely distributed throughout epithelial surfaces, but especially dense in the gastrointestinal and respiratory tracts. Kupffer cells have phagocytic properties and are found in the liver; they participate in the removal of ageing erythrocytes and other particulate debris. The gastric mucosa contains many cell subtypes, including acid-secreting cells (also known as parietal or oxyntic cells), pepsin-secreting cells (also known as peptic, chief, or zymogenic cells) and G-cells (gastrin-secreting cells). Peptic cells synthesize and secrete the proteolytic enzyme, pepsin. Parietal cells actively secrete hydrochloric acid into the gastric lumen, accounting for the acidic environment encountered in the stomach. However, parietal cells are also involved in the secretion of the glycoprotein, intrinsic factor.
The respiratory system
Laurie K. McCorry, Martin M. Zdanowicz, Cynthia Y. Gonnella in Essentials of Human Physiology and Pathophysiology for Pharmacy and Allied Health, 2019
All the conducting airways, the trachea up to the terminal bronchioles, are lined with pseudostratified ciliated columnar epithelium. There are approximately 300 cilia per epithelial cell. Interspersed among these epithelial cells are mucus-secreting goblet cells. Furthermore, mucus glands are found in the larger airways. Consequently, the surface of the conducting airways consists of a mucus-covered ciliated epithelium. The cilia beat upward at frequencies between 600 and 900 beats/min and continuously move the mucus away from the respiratory zone and up toward the pharynx at a rate of 1–2 cm/min. This mucociliary escalator provides an important protective mechanism that removes inhaled particles from the lungs and particles larger than about 6 μm are typically stopped from reaching the respiratory zone. Mucus that reaches the pharynx is usually swallowed or expectorated. An additional mechanism by which airway mucus protects the lungs involves the presence of immunoglobulins. These substances, also referred to as antibodies, destroy or neutralize inhaled pathogens. The activity of the immunoglobulins was discussed in detail in Chapter 3, The Immune System. Interestingly, the nicotine found in cigarette smoke paralyzes the cilia and impairs their ability to remove the many toxic substances found in smoke.
Secreted effectors of the innate mucosal barrier
Phillip D. Smith, Richard S. Blumberg, Thomas T. MacDonald in Principles of Mucosal Immunology, 2020
A fundamentally important role for goblet cells has emerged that is functionally distinct from their role in producing the secreted mucus barrier but is linked mechanistically to secretory events. Goblet cells in the small intestine sample soluble antigens from the luminal environment via exocytosis following granule release, and this antigen is then delivered by transcytosis to underlying dendritic cells closely opposed to the basal membrane of the goblet cell. This mechanism regulates antigen-specific controlled immune responses against the microbiota. In early neonatal life, this sampling function also occurs in goblet cells in the colon but is suppressed in adult life by exposure to microbial TLR ligands. The neonatal colonic goblet cell antigen transfer drives the establishment of regulatory T cells, and ablation of this function predisposes to subsequent inappropriate mucosal immune responses. Interestingly, colonic goblet cell antigen transfer is turned on in adults by suppression of the microbiota with antibiotics.
Eye Make-up Products and Dry Eye Disease: A Mini Review
Published in Current Eye Research, 2022
Mazyar Yazdani, Katja Benedikte Prestø Elgstøen, Tor Paaske Utheim
Tear fluid and particles attached to the ocular surface are drained by the nasolacrimal duct into the inferior meatus of the nose. Anatomically, the lacrimal passages are divided into bony and membranous lacrimal sections. The latter include the lacrimal canaliculi, lacrimal sac, and the nasolacrimal duct. The last two parts are lined by a double-layered epithelium containing superficial columnar cells and basal flattened cells. Goblet cells may also be present in the epithelial layer. During blinking, tears are wiped and pushed into the lacrimal puncta, small openings located in the nasal upper and lower eyelids. The punctum ends in the canaliculus, where the fluid drains into the lacrimal sac followed by the nasolacrimal duct canal before reaching the nasal cavity.31
Interactions of commensal and pathogenic microorganisms with the mucus layer in the colon
Published in Gut Microbes, 2020
Rui Cai, Chen Cheng, Jianwei Chen, Xiaoqiang Xu, Chao Ding, Bing Gu
The first line of defense against pathogenic microorganisms is the mucosal barrier, which is made up of the epithelium and a protecting overlying host-secreted mucus layer and contains commensal microorganisms.3 Colonic epithelial cells are composed of five differentiated cell types, including enterocytes, enteroendocrine cells, tuft cells, goblet cells, and microfold (M) cells, which are responsible for absorption, hormone secretion, the taste-chemosensory response, mucus production and antigen sampling, respectively.4,5 The mucus secreted by goblet cells continuously replenishes the mucus layer to lubricate and protect the epithelial cells. In recent years, increasing attention has been paid to the role of the mucus barrier owing to changes in dietary habits and lifestyles, such as the reduced consumption of fiber polysaccharides and overuse or abuse of antibiotics.6–8 Such changes in the composition of the colon microbiota may eventually cause damage to the mucus barrier, compromising the resistance to colonization by incoming pathogenic bacteria.9,10
Chemopreventive effect of α-hederin/carboplatin combination against experimental colon hyperplasia and impact on JNK signaling
Published in Toxicology Mechanisms and Methods, 2021
Hoda I. Bahr, Afaf T. Ibrahiem, Attia M. Gabr, Alaaeldeen M. Elbahaie, Hoda S. Elmahdi, Nema Soliman, Amal M. Youssef, Mohamed El-Sherbiny, Sawsan A. Zaitone
In Hx&E sections, colon of saline group showed the normal histological architecture of the mice colon. The wall of the colon was formed of mucosa, submucosa, musculosa, and serosa. The mucosa of colon showed intact surface lined by simple columnar epithelium with acidophilic cytoplasm and basal basophilic nuclei. Crypts appeared straight tubular in shape with narrow openings. The crypts were lined by simple columnar epithelium that had basal oval vesicular nuclei. Goblet cells are flask shaped with vacuolated cytoplasm and basal flattened nuclei (Figure 3(A)). The colon sections of the hyperplasia group showed severe dysplasia as the mucosa form irregular shape and elevated, distorted with crowded hyperchromatic nuclei, loss of crypt architecture, disintegration of goblet cells, and cellular infiltration in the lamina propria (stroma) (Figure 3(B)). Carboplatin group showed diffuse moderate dysplasia (grade 3) with fusion of some crypts and appearance of more goblet cells. Cellular infiltrate were seen (Figure 3(C)). α-Hederin group showed moderate degree of dysplasia (grade 2) with much more goblet cells and less cellular infiltration in lamina propria is shown in Figure 3(D). On the other side, carboplatin + α-hederin group revealed marked improvement of the pathological changes and showed mild crowed crypts with near normal cytological features and normal goblet cells except few foci still with mild degree of dysplasia (Figure 3(E)).
Related Knowledge Centers
- Apocrine
- Asthma
- Merocrine
- Microvillus
- Mucin
- Mucus
- Respiratory Epithelium
- Simple Columnar Epithelium
- Metaplasia
- Airway Basal Cell