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.
Quick Answer. Underarm lymph node swelling caused by an infection or other illness can also cause pain, according to WebMD. Lymph nodes located in the groin, behind the ears, at the back of the head or under the jaw may also swell.