2)i think it should be macrophages and B lymphocytes which act as APC's for transfer to lymph node and antibody class switch to IgG.. which is present in the periodontal pockets... since it is established periodontitis, more likely answer should be lymphocytes.. since T cells would also be present...not sure 
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3) should be through IX ann X...
Anyone????
Peripheral chemoreceptors act principally to detect variation of the 
oxygen concentration in the 
arterial blood, whilst also monitoring arterial 
carbon dioxide and 
pH. They are located in the 
aortic body and 
carotid body, on the 
arch of the aorta and on the 
common carotid artery, respectively. The carotid bodies are most sensitive to changes in partial pressure of arterial oxygen and pH. The aortic bodies are most sensitive to the content of arterial oxygen. In contrast, the 
central chemoreceptors are relatively insensitive to oxygen concentration, and thus to 
hypoxia.
A continual signal is sent, via 
cranial nerves IX and 
X, from the peripheral chemoreceptors to the 
brainstem. With a decrease in arterial oxygen tension and content or drop in plasma pH, the signal intensifies, and results in an increase in 
ventilation rate