Atelectasis from the outside (tumor, lymph node, tubercle). Another cause is poor surfactant spreading during inspiration, causing the surface tension to be at its highest which tends to collapse smaller alveoli. Atelectasis may also occur during suction, as along with sputum, air is withdrawn from the lungs. There are several types of atelectasis according to their underlying mechanisms or the distribution of alveolar collapse; resorption, compression, microatelectasis and contraction atelectasis. Relaxation atelectasis (also called passive atelectasis) is when a pleural effusion or a pneumothorax disrupts the contact between the parietal and visceral pleurae. Risk factors associated with increased likelihood of the
Cold and heat adaptations in humans Stress from extreme external temperature can cause the human body to shut down. Hypothermia can set in when the core temperature drops to 35 °C (95 °F). Hyperthermia can set in when the core body temperature rises above 37.5-38.3 °C (99.5-100.9 °F). These temperatures commonly result in mortality. Humans have adapted to living in climates where hypothermia and hyperthermia are common primarily through culture and technology, such as the use of clothing and shelter. Modern humans emerged from Africa approximately 40,000 years ago during a period of unstable climate, leading to a variety of new traits among the population. Evidence