Coronavirus Disease (COVID-19) is caused by the RNA virus SARS-CoV-2. The primary receptor for the virus is most likely Angiotensin-converting enzyme 2 (ACE2), and the virus enters the body by infecting epithelial cells of the respiratory tract. Through the activation of Toll Like Receptors (TLRs), epithelial cells begin to synthesize various biologically active molecules. The pathophysiology of the COVID 19 is primarily attributed to the hyperactivation of host's immune system due to direct damage to the cells, with consequent release of proinflammatory substances, but also due to the activation of the innate immune response through the activation of alveolar macrophages and dendrite cells (DC). A strong proinflammatory reaction causes damage to alveolar epithelial cells and vascular endothelium. Respiratory epithelial cells, alveolar macrophages and DC are likely to be the most important cells involved in the innate immune response to the virus, since prolonged and excessive SARS-CoV-2-induced activation of these cells leads to the secretion of cytokines and chemokines that massively attract leukocytes and monocytes to the lungs and cause lung damage.

Introduction: Elastic fibers are constituents of the dermal extracellular matrix, determining the histoarchitecture of the
dermal connective tissue. Organization and density of elastic fibers change as skin ages. The aim of this paper was to determine the similarities and differences between the photo-aging and the physiological aging of skin by examining organization and quantifying the elastic fibers in the dermis during aging. The material included samples of photoexposed and photoprotected skin, obtained from 90 cadavers aged 0-82 years. The samples were classified into five age groups: newborns, young age, middle age, mature age and the oldest age. Skin samples were stained using the Halmi modification of Aldehyd fucshin staining method, as well as Alcian blue staining (the Spicer method). Volume density (VD) of the elastic fibers was measured using Image J program.

Results: In the skin of newborns and young age group (neck and abdomen) elastic fibers appeared to form a network structure. In the photoexposed skin of the mature age and the oldest group, elastic fibers showed tendency to fragment, while the elastic material exhibited tendency to accumulate. VD of elastic network in the skin of the neck in the middle, mature and the oldest age group was greater than VD of abdominal skin of the respective age groups (3.66±0.28%, 5.61±0.22%, 6.24±0.21% respectively). Age-related statistically significant increase in VD of the elastic network in the skin of the neck, as well as a statistically significant reduction of elastic network VD in the abdominal skin, has been observed (middle age - oldest).

Conclusion: Correlation of the organization and quantity of elastic fibers with age exhibits different pattern in photoexposed compared to photoprotected skin. A quantitative evaluation of the volume density of elastic fibers correlates with clinically visible signs of photo-aging, primarily with solar elastosis.

As a mixed exocrine and endocrine gland pancreas has a very important role in the digestive tract. The juice of his exocrine part, which is released into the duodenum, carries more than 20 pancreatic enzymes, important for a normal process of digestion. Endocrine part of the gland, which consists of the islets-insula, actively participate in the metabolism of human organism, secreting two important hormones - insulin and glucagon. Because of its location, the pancreas is an extremely inaccessible organ for a physical examination. Despite of a large number of modern clinical methods for monitoring changes in the body, the detail knowledge of morphological characteristics of this gland is still very important. The material was taken from the cadaver of the fetus and newborn at the Institute of Pathology of the Faculty of Medicine. We classified samples of pancreas into three groups, with respect to age (from 3 months to neonates) and CS length. After dehydration and the molding compositions are cut at a thickness of between 6 and 10 microns. In addition to standard staining methods, some preparations are for identification of insula, painted by Grimelijus. In this study, we determined the morphological changes of the prenatal pancreas, from the third month of intrauterine fetal development, until the end of the fetal time and determine the dynamics of changes in the parenchyma and stroma. We could distinguish functional parts of the pancreas, in 10-11th week of development. In the first trimester of pregnancy, we have noticed an increase in parenchymal elements and the reduction of the stroma, which is slightly more pronounced in interlobular area, that clearly differentiating lobules. At the beginning of the second trimester of pregnancy, in the pancreas that are developing, we observed significant changes.The lobular structure of pancreas was clearly visible. Pancreatic acini are clearly differentiated and are in very close contact, since the stroma between them very reduced. Within almost all lobulus there are clearly expressed the islets of Langerhans, which are multiplied, different sizes, separated from the exocrine part by poorly expressed connective tissue. In the group of prematurely born children, we found that the morphology of the pancreas is very similar to the pancreas at the end of the fetal period.