Final answer:
Acute hepatitis is characterized by the viral infection and inflammation of hepatocytes, resulting in symptoms such as malaise, loss of appetite, and jaundice.
Step-by-step explanation:
The initial injury seen in acute hepatitis is the infection and subsequent inflammation of hepatocytes, which are the functional cells of the liver. When someone is infected with a hepatitis virus, the pathogen enters the bloodstream, also known as viremia, and can spread to several organs, including the liver. The hepatitis viruses, such as HAV, HBV, HCV, HDV, and HEV, target the liver cells, leading to replication within the hepatocytes. The process of replication and viral spread within the liver results in inflammation and liver damage. Symptoms such as malaise, loss of appetite, dark urine, and abdominal pain, specifically in the upper right quadrant, are characteristic of the inflammation during acute hepatitis. The liver's compromised function also leads to an inability to effectively break down hemoglobin, which can manifest as jaundice, characterized by yellowing of the skin and the whites of the eyes.