The cervical vertebra 6 is a vertebra of the spinal column.

The cervical spinal nerve 6

Cervical spinal nerve 6

The cervical spinal nerve 6 is a spinal nerve of the cervical segment..It originates from the spinal column from above the cervical vertebra 6 ....

 (C6) passes out above it.

The first cricoid ring is directly opposite C6.

C6 is the vertebral level that the oesophagus

Esophagus

The esophagus is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach. During swallowing, food passes from the mouth through the pharynx into the esophagus and travels via peristalsis to the stomach...

 becomes continuous with the laryngopharynx and also where the larynx

Larynx

The larynx , commonly called the voice box, is an organ in the neck of amphibians, reptiles and mammals involved in breathing, sound production, and protecting the trachea against food aspiration. It manipulates pitch and volume...

 becomes continuous with the trachea

Vertebrate trachea

In tetrapod anatomy the trachea, or windpipe, is a tube that connects the pharynx or larynx to the lungs, allowing the passage of air. It is lined with pseudostratified ciliated columnar epithelium cells with goblet cells that produce mucus...

. It is also the level where the carotid pulse can be palpated against the transverse process of the C6 vertebrae.