Final answer:
Pre and post auricular nodes tend to be palpable before age 2 due to the developing immune system in infants. The frontal lobes are fully developed by the age of 25. During the menstrual cycle, hormonal changes in the luteal phase and during pregnancy can influence physiological responses, including those of the immune system.
Step-by-step explanation:
The pre and post auricular nodes are part of the lymphatic system, which is crucial for the body's immune response. They are typically not palpable in healthy individuals. However, they can become palpable during certain conditions or stages of life. The options provided suggest different life stages, but the palpability of lymph nodes is generally associated with reactivity to infection or inflammation rather than a specific age. Yet, in terms of the options given, lymph nodes, including pre and post auricular nodes, are most commonly palpable D) Before age 2. This is because infants' immune systems are still developing, and they are more reactive to the various new antigens they encounter. Additionally, the anterior fontanel, which is part of the infant's skull, is expected to close between nine to 18 months after birth, which reflects the rapid changes occurring in infancy including immune system development.
Regarding brain development, the frontal lobes become fully developed d) by 25 years old. This part of the brain is responsible for complex behaviors including planning, personality expression, and moderating social behaviour. Frontal lobe maturation is a lengthy process that continues well into young adulthood.
When discussing changes in lymphatic reactivity during the menstrual cycle, lymph nodes do not typically demonstrate noticeable change during this time. However, this question seems to be directed towards when the endocrine changes are happening, notably B) in the luteal phase and C) during pregnancy, where hormonal shifts can influence various physiological responses, including those in the immune system.