The origin of the mid-gut (mesenteron), outer layers become continuous, forming respectively the amnion that has no chitinous lining in the developed insect, is the disputed and the serosa (fig.
Quick Answer. Possible causes of swollen lymph nodes behind the ears include an ear infection, an abscessed tooth, a cold, the flu or another infection, according to MedlinePlus. Lymph nodes also commonly appear beneath the jaw, on the back of the head, or on the neck, armpit or groin.
Ear infections occur when one of your Eustachian tubes becomes swollen or blocked and fluid builds up in your middle ear. Eustachian tubes are small tubes that run from each ear directly to the back of the throat. The causes of Eustachian tube blockage include: 1  allergies. 2  colds.