Surfactant is a complex substance containing phospholipids and a number of apoproteins. This essential fluid is produced by the Type II alveolar cells, and lines the alveoli and smallest bronchioles. Surfactant reduces surface tension throughout the lung, thereby contributing to its general compliance. It is also important because it stabilizes the alveoli.
Stagnant anoxia occurs when there is interference with the blood flow, although the blood and its oxygen-carrying abilities are normal. A common cause of general stagnant anoxia is heart disease or interference with the return of blood flow through the veins.
There are three main causes of anemia: blood loss, lower than normal levels of red blood cell (RBC) production, or higher than normal rates of RBC destruction. More than one of these factors can combine to cause anemia. Blood loss is the most common cause of anemia, particularly iron-deficiency anemia. Blood loss can be short term or persist over time. It can be caused by heavy menstrual periods, bleeding in the digestive or urinary tracts, surgery, trauma, or cancer.