MORPHOLOGICAL AND PATHOLOGICAL CHANGES IN THE LUNGS DUE TO COVID-19

Аннотация

The COVID-19 pandemic has significantly impacted not only global healthcare systems but also the human body. The SARS-CoV-2 virus damages both the upper and lower respiratory tracts, leading to severe inflammatory processes in the lungs. The acute and chronic phases of this disease can cause serious pathological conditions such as alveolar damage, microthrombosis,and fibrosis. This article provides a comprehensive review of the morphological and pathological changes in the lungs due to COVID-19, explaining how the virus affects alveolar cells, triggers inflammatory processes, and leads to long-term complications. Keywords: COVID-19, SARS-CoV-2, lung pathology, alveolar damage, fibrosis, thrombosis, cytokine storm, microthrombosis,diffuse alveolar damage (DAD), pulmonary fibrosis. MainSection Mechanism ofCOVID-19 Entry and Damage to theLungs COVID-19 is transmitted through airborne droplets and reaches the lungs via the upper respiratory tract. The virus binds toACE2 receptors and primarily infects alveolar epithelial cells. Thisprocess occurs in thefollowing stages: 1.Entry oftheVirus into Alveolar Cells The S-spike protein of the SARS-CoV-2 virus binds to type II pneumocytes in the alveoli.The virus enters the cells, replicates itsRNA, and destroys them. 2.Immune Responseand Inflammation Cytokines (IL-6, IL-1β, TNF-α) released by infected cells initiate an inflammatory response.Neutrophilsand macrophages migrate to thealveoli toeliminatethepathogens. 3.Microthrombosisand Vascular Damage The inflammatory process damages endothelial cells, leading to thrombosis. This disrupts blood circulation in thealveoli, causing hypoxemiaand respiratory failure. http://www.internationaljournal.co.in/index.php/jasass 151 Volume15 Issue02, February2025 Impact factor: 2019: 4.679 2020: 5.015 2021: 5.436, 2022: 5.242, 2023: 6.995, 2024 7.75 4.Pulmonary Fibrosis and Long-Term Damage After the acute inflammation phase, fibroblasts become activated in the alveoli. The accumulation of connective tissue leads to pulmonary fibrosis, resulting in long-term breathing difficulties. Morphological Changes in theLungs Due to COVID-19 COVID-19 induces various pathological processes in lung tissue. The most significant ones include: 1.DiffuseAlveolar Damage (DAD) DAD is one of the main pathological features of COVID-19 pneumonia. It progresses in three phases: Exudative Phase=> Severe inflammation and fluid accumulation in the lungs. Damage to alveolarwalls, formation ofhyaline membranes.Patients experience severe respiratory distress. Proliferative Phase=> Activation of fibroblasts leads to the regeneration of cells. Thickening of alveolarwalls but lossofelasticity. Fibrotic Phase=> Pulmonary fibrosis develops due to excess connective tissue. This impairs lung function, causing long-term complications. 2.Microthrombosisand Circulatory Disorders In 30-50%of COVID-19 patients, thrombi arefound inpulmonary capillaries. Consequences include: Pulmonary embolism: Thrombi obstruct large arteries, leading toacute respiratory failure. Impaired gas exchange: Oxygen deficiency occurs. Pulmonary hypertension: Increased vascular pressure puts strain ontheright sideoftheheart. 3.CytokineStorm and Alveolar Inflammation One of the most dangerous mechanisms of COVID-19 is the cytokine storm. The immune system overreacts, producing excessive inflammatory mediators (IL-6, IL-1β, TNF-α). Uncontrolled inflammation damages the alveoli. Patients deteriorate rapidly, often requiring mechanical ventilation. Long-Term Effectsof COVID-19 ontheLungs Thelong-term consequences ofCOVID-19 pneumonia include: http://www.internationaljournal.co.in/index.php/jasass 152 Volume15 Issue02, February2025 Impact factor: 2019: 4.679 2020: 5.015 2021: 5.436, 2022: 5.242, 2023: 6.995, 2024 7.75 1.Pulmonary Fibrosis: Loss of elastictissuedisrupts normal lung function. 2.ChronicRespiratory Failure: Alveolar dysfunction causes persistent shortness ofbreath. 3. Post-COVID Syndrome: Patients may suffer from prolonged fatigue, breathing difficulties, andcardiovascular issues. Pathological Features and Clinical Manifestations The pathological changes in the lungs due to COVID-19 can manifest in various clinical forms. Themain symptoms include: AcuteRespiratory Failure: Impaired oxygen exchange dueto alveolar tissuedamage. Hypoxemia: Reduced oxygen levels intheblooddueto impaired gas exchange. Pulmonary Fibrosis: Long-term COVID-19 pneumonia leads to scarring of lung tissue, restricting lung capacity. HemorrhagicPneumonia: Bleeding inthe alveoli and rupture ofsmall bloodvessels may occur. http://www.internationaljournal.co.in/index.php/jasass 153 Volume15 Issue02, February2025 Impact factor: 2019: 4.679 2020: 5.015 2021: 5.436, 2022: 5.242, 2023: 6.995, 2024 7.75 Lethal Pulmonary Pathology in COVID-19 1. Early Lung Damage: Alveolar edema, endothelial necrosis, microthrombosis, and endothelialitis.Progressive inflammatory vascular damage with nuclear debris andgranulocytes. 2.ExudativePhas