Which immune cells are most abundant and first to respond to infection?

What is a key difference between steroid and protein hormones?

Which of the following are functions of the respiratory system? (Select all that apply)

Which of the following structures are part of the upper respiratory system? (Select all that apply)

Bonus question. A person suffers a severe allergic reaction that causes widespread inflammation and swelling. Explain how the immune, respiratory, and endocrine systems respond during this event, and describe how their interactions could become life-threatening without medical intervention. 

What is the function of cilia in the respiratory tract?

What is the primary function of the alveoli in the respiratory system? 

Which structure stores and matures non-motile sperm cells?

Which cells are primarily responsible for killing virus-infected cells without prior activation?