jugular (deep cervical) chain
base of the skull to the inferior border of hyoid bone
anterior to the posterior border of sternocleidomastoid (SCM) muscle
posterior to the posterior border of the submandibular glands
level IIa: anterior, lateral, or medial to the vein or posterior to the internal jugular vein and inseparable from it
level IIb: posterior to the internal jugular vein and have a fat plane separating the nodes and the vein