These white blood cell-filled filters are the lymphatic system’s filtration units. They collect and destroy dangerous bacteria, viruses, and foreign particles that infiltrate the body. There are approximately 500 to 600 lymph nodes throughout the body, with clusters in the neck, underarms, chest, groin, and abdomen. The bean-shaped nodes normally range in size from a few millimeters up to 2 centimeters but may become enlarged due to the presence of a tumor. What else causes lymph nodes to swell? Discuss
Source: The Free Dictionary
Also called the motor speech center, Broca’s area is a section of the human brain involved in language processing, speech production, and comprehension. The region is named after 19th century physician Paul Broca, who located it in the frontal lobe of the cortex. Damage to the area can result in a condition called Broca’s aphasia, which renders sufferers unable to create grammatically complex sentences. In his research, Broca worked closely with a patient who could only produce what five words? 
The term sexual dimorphism describes the physical differences between males and females of the same species that arise as a consequence of sexual maturation. These differences can manifest as variations in size and color, and the presence or absence of body parts used in courtship displays or fights. In some cases, the sexual dimorphism is so striking that males and females of the same species are mistaken as members of entirely different species. What is one example of this? 
A hydraulophone is a musical instrument played via direct physical contact with a hydraulic fluid, typically water. The sound is generated from the vibration of the instrument’s liquid and changes based on the position of the fingers in relation to the finger holes. The invention of such devices led to the creation of a physics-based classification system for instruments that takes into account the state of matter that initially produces their sound. What are the five categories of this system? 
Strange animal behavior, changes in electromagnetic fields and the hydrogen content of soil, and the appearance of unusual clouds have all been cited as phenomena potentially related to impending earthquakes, yet earthquake prediction remains a controversial field. Skeptics maintain that there is little evidence linking observable factors with subsequent earthquake activity. What are the arguments against alerting people in advance if there is a chance of an earthquake? 
When their epileptic handlers experience seizures, these response dogs come to the rescue by pulling away dangerous objects, attempting to rouse them if they lose consciousness, and even summoning aid by finding another person or activating a medical alert or pre-programmed phone. Because epilepsy is such a wide-ranging condition, each dog is trained for a specific individual’s needs. Studies in which dogs were trained to anticipate their owners’ impending seizures have shown what? 
More than half of the electricity generated in the United States is produced by coal-fired power plants. Generally, only a small percentage of the coal used in those plants comes from the controversial practice of mountaintop removal mining, or MTR, which involves the use of heavy explosives to blast away up to 1,000 vertical feet of a mountain after its surface has been cleared of timber. What 1970s crises first sparked an increase in the demand for coal and triggered the widespread use of MTR? 
When negative circumstances align, accidents happen—that’s what British psychologist James T. Reason asserts with his Swiss Cheese model of accident causation, a model used in the risk analysis and risk management of human systems. Essentially, the model, which has been applied to healthcare, aviation safety, and emergency service organizations, states that a system produces a failure when all of its “holes” momentarily line up. What are the four levels of failure set forth by Reason? 
An estimated 18 percent of the world’s population is prone to sleepwalking. While most cases simply consist of sitting up in bed, there are a number of documented cases of eating, bathing, and even driving and committing murder while sleeping. The sleep disorder is more common in people with high levels of stress and anxiety and among those with a family history of sleepwalking. What tragic Shakespearean character, wracked with an overwhelming sense of guilt, is driven to sleepwalk? 
Beginning in the late 8th century, the Carolingian Renaissance was a period of literary and artistic growth during which the study of architecture, jurisprudence, and scriptures blossomed. Peaking during the reigns of Charlemagne and Louis the Pious, the era also saw the development of Medieval Latin and Carolingian minuscule, which provided a common language, writing style, and method of communication for scholars throughout Europe. Why do some dispute the legitimacy of this “renaissance”?