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1 day ago · Cells in the human body vary in structure and function. True The ___________ is an organelle composed of interconnected membrane-bound sacs that provide a transport system and an attachment for ribosomes.
Mar 10, 2022 · Monocytes/macrophages are characterized by a strong plasticity and heterogeneity. Dependent on the surrounding micromilieu and the immunological context, macrophages can acquire distinct functional characteristics through a process called polarization.
- Uwe Lendeckel, Simone Venz, Carmen Wolke
- ChemTexts. 2022; 8(2): 12.
- 10.1007/s40828-022-00163-4
- 2022
Jul 14, 2022 · Macrophages are a type of white blood cell that play an integral part in the immune system with the role of phagocytosing foreign antigens, such as bacteria. They are able to present these antigens to other immune cells, such as T-cells, for further destruction.
- Macrophages can largely be categorized into two main types: M1 and M2 macrophages. The M1 type, referred to as classically-activated macrophages, a...
- Generally, macrophages play a role in destroying infectious organisms that enter the body, clearing cellular debris, and wound healing. They also p...
- Overall, macrophages are good and play a critical role in the human body. They protect our body from bacterial and viral infections by secreting an...
- Overview
- Tissue layers of the stomach
- Types of cells in the stomach
- Surface mucous cells
- Parietal cells
- Chief cells
- Neuroendocrine cells
- Summary
Various cells in the stomach secrete digestive enzymes and hydrochloric acid. These substances break down food so the body can absorb nutrients.
The stomach is a muscular organ in the upper abdomen that is part of the digestive system. The cells of the stomach are constantly exposed to digestive juices and the stomach’s contents. Therefore, to protect themselves, the cells produce a layer of mucus and constantly regenerate to keep the stomach lining healthy.
The stomach has four regions:
•Fundus: the upper rounded part of the stomach
•Cardia: the part nearest the esophagus
•Body: the main central part
•Pylorus: the lower narrow part
Besides different regions, the stomach also has four tissue layers. From the outermost layer to the innermost, these are:
The epithelium folds into the lamina propria, forming the gastric pits and glands, which contain the following specialized cells:
•surface mucous cells (foveolar cells)
•parietal cells
•chief cells
The gastric mucosa lines the stomach and contains the gastric glands, which secrete different substances. The surface of the stomach and opening of the gastric pits have a single layer of columnar epithelial cells, known as surface mucous cells or foveolar cells.
These cells secrete a thick layer of mucus that covers the stomach lining and protects it from the digestive juices. The mucus also provides a slippery surface that helps food move through the stomach.
Parietal cells are present in the gastric pits that mainly occur in the upper part of the stomach, or the fundus. They secrete hydrochloric acid, which helps break down food. Hydrochloric acid also kills bacteria and other microorganisms that may be present in food.
In addition to secreting hydrochloric acid, these cells secrete a protein known as intrinsic factor. Intrinsic factor helps the body absorb vitamin B12 in the small intestines.
Chief cells are present in the base of gastric glands, which are in the fundus. They secrete digestive enzymes that help break down food.
The chief cells secrete pepsinogen. It converts to pepsin in the presence of hydrochloric acid. Pepsin helps digest proteins into small units known as polypeptides.
Neuroendocrine cells occur in the gastric pits of the stomach. There are several subtypes that secrete various hormones:
•G-cells: These sit in the stomach’s pylorus region and produce the hormone gastrin. Gastrin can increase hydrochloric acid production by stimulating ECL-like cells to release histamine.
•ECL-like cells: These cells secrete histamine when gastrin stimulates them. Histamine binds to receptors on the parietal cells and increases hydrochloric acid secretion. These cells exist mainly in the fundus of the stomach.
•D-cells: These cells are in the pylorus of the stomach. They secrete an inhibitory molecule called somatostatin. When the stomach reaches a certain level of acidity, D-cells release somatostatin, which then suppresses gastrin and the overall production of gastric acid.
•EC-cells: These cells secrete serotonin. Serotonin is involved in regulating gastrointestinal motility and fluid secretion.
•P/D1 cells: These cells secrete the hormone ghrelin. Ghrelin is a hunger hormone that increases appetite and promotes fat storage.
The cells of the stomach are highly specialized with different and varied functions.
The surface mucous cells secrete a layer of mucus that protects the stomach lining. Parietal cells secrete hydrochloric acid that helps break down food and intrinsic factor that aids in the absorption of vitamin B12.
Chief cells secrete enzymes that support digestion. Neuroendocrine cells secrete various hormones that regulate stomach acidity, hunger, and gastrointestinal motility.
Each cell type works together to ensure that the stomach can effectively digest food and protect itself from harmful substances.
Oct 30, 2023 · The macrophages are highly specialized, multitasking immune cells that play a key role in the protection of the organism against pathogen invasion. The macrophages originate from the monocytes, a type of white blood cells that comes from the bone marrow.
- Content Manager
- 24 min
M-CSF induced cells are named M2 macrophages and have the role of phagocytosis and release of a cytokine called interleukin-10. The process by which macrophages adapt their functions and characteristics (phenotypes) in response to their environment is termed macrophage polarization.
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