Gastrointestinal physiology
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal in Principles of Physiology for the Anaesthetist, 2015
Acinar cells of the pancreas secrete enzymes and fluid into a system of ducts that produce an alkaline fluid that modifies the composition of the acinar secretion. At high rates of secretion than at lower rates, the bicarbonate content of pancreatic juice is higher. Precursors of proteolytic enzymes (trypsins) are stored as inactive zymogen granules to prevent autodigestion, and these are activated in the duodenum. Pancreatic α-amylase is secreted in its active form and digests starch to oligosaccharides in the duodenum. Several lipases present in pancreatic juice hydrolyse water-insoluble triglycerides to release free fatty acids and monoglycerides. Bile salts are necessary for this process as they form an emulsion on which the lipases can act. The control of exocrine pancreatic secretion is chiefly hormonal via secretin and CCK. The initial cephalic phase (via the vagus) and gastric phase (mediated by gastrin) make a small contribution to the secretion of pancreatic juice. About 70% of pancreatic juice secretion occurs during the intestinal phase. Secretin and CCK are released by the upper intestinal mucosa in response to products of fat and protein digestion.
Comparative Anatomy, Physiology, and Biochemistry of Mammalian Skin
David W. Hobson in Dermal and Ocular Toxicology, 2020
Sebaceous glands contain cells in various stages of differentiation. Morphologically, the gland consists of a group of lobes or acini. Three types of acinar cells have been described ultrastructurally. The structure of these cells changes progressively from the periphery to the center of each gland. The peripheral cell lies on the basement membrane that surrounds the acinus of the sebaceous gland. The second cell type is the partially differentiated cell which is actively synthesizing lipid. The third cell type is the fully differentiated cell which is large and full of lipid droplets. It is at this stage that the cell will rupture and release its entire secretion (lipid) into the sebaceous duct and then onto the surface of the skin. This process is termed holocrine secretion. The function of sebum, a complex mixture of lipids, is that of acting as an antibacterial agent. Also, in hairy mammals it may act as a waterproofing agent and may prevent moisture loss from the human epidermis.217,219,229,230 As noted by Strauss et al.,230a differences can occur in sebum composition among mammals.
Salivary Gland Tumors
Dongyou Liu in Tumors and Cancers, 2017
Structurally, a salivary gland is made up of four segments: acinus, intercalated duct, striated duct, and excretory duct, with two types of cells present in each segment: abluminal cells (as myoepithelial cells in the acinus and intercalated duct, and basal cells in the striated and excretory ducts) and luminal cells (as acinar cells in the acinus, and ductal cells in the striated duct and excretory duct). The acinar cells in the acinus may be either serous or mucous, with the serous cells producing a watery secretion containing ions, enzymes, and mucin and the mucous cells producing mucus. The parotid glands are mostly serous, the submandibular glands are mixed (predominantly serous), the sublingual glands are mixed (predominantly mucous), and the minor salivary glands are mixed (predominantly mucous).
Long-term changes of pancreatic function in patients with complicated walled-off necrosis
Published in Scandinavian Journal of Gastroenterology, 2022
Camilla Nøjgaard, Mikkel Werge, Astrid Naver, Anne Wilkens Knudsen, Nicolai J. Wewer Albrechtsen, Søren Møller, Lise Lotte Gluud, Srdan Novovic
Eighty-five percent of the pancreatic tissue is represented by the exocrine pancreas whereas only 2% is comprised of endocrine tissue [24]. Approximately, 40 acinar cells constitute an acinus which is connected by centroacinar cells to the pancreatic duct system lined by pancreatic duct cells. Nearly one million islets of Langerhans are scattered throughout the pancreas. As the acinar and Langerhans cells are closely allocated it is understandable if necrosis in the pancreas leads to both exocrine and endocrine insufficiency. In line with this, we found that the four patients with new-onset diabetes also had exocrine insufficiency. This is usually not the case in chronic pancreatitis, as these patients can either have diabetes without PEI or the opposite or both. This confirm that acute necrotizing pancreatitis and chronic pancreatitis are two different diseases with different pathogenesis.
Regenerating β cells of the pancreas – potential developments in diabetes treatment
Published in Expert Opinion on Biological Therapy, 2018
The pancreatic exocrine cells, specifically acinar cells, are located in the native environment of β cells; they are abundant; and they share pancreatic progenitors with β cells (i.e. pancreatic endoderm) during embryonic development. In addition, as discussed above, pancreatic progenitor cells exist in pancreatic exocrine including acinar and ductal tissues. Therefore, the acinar cells are logic and attractive targets to be reprogrammed into β cells. In search of an appropriate acinar-to-β reprogramming protocol, Zhou et al. have attempted to ectopically express different combinations of key transcription factors in the mouse pancreatic exocrine [104]. Their results show that a combination of Ngn3, Pdx1 and MafA, all of which are essential for embryonic β-cell development, can reprogram acinar cells into functional β cells in vivo. The regenerated β cells have similar size, shape, and ultrastructure to that of endogenous islet β cells, and they are able to ameliorate hyperglycemia in T1D mice. Interestingly, further studies show that Ngn3 alone is able to convert acinar cells into δ-like cells, whereas a combination of Ngn3 and MafA reprograms the acinar cells into α-like cells [105]. These studies suggest that acinar cells can be reprogrammed into three endocrine cell subtypes via forced expression of different transcription factors.
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.