The esophagus has an outer lining, called the "adventitia", which surrounds the muscular layers and separates the esophagus from other nearby organs. The heart is directly behind the middle esophagus, while the windpipe ("trachea") is directly in front of it. The esophagus is also very close to the liver, lungs, and major blood vessels from the heart ("aorta and venal cava"). The esophagus receives most of it's blood from the aorta and drains it to the liver and venal cava. A system of "drainage channels" runs through the esophagus, between the mucosal and muscular layers. These are called "lymph channels" and act to purify the blood serum, by transporting it to nearby "lymph nodes" (glands) where the serum is filtered. Both the blood supply, and lymph channels and glands, can act as conduits to spread infection or cancer. This spread may be along the length of the esophagus, around it's diameter, to local lymph nodes or organs, or to distant body areas.
When a person has shrinkage ("cirrhosis") of the liver due to excessive alcohol or chronic infections, it places back pressure on the blood draining from the esophagus. This results in swelling of the blood vessels in the lower esophagus, called "varices". These may spontaneously bleed when there is a lot a pressure between the liver and esophagus ("portal hypertension") and is a medical emergency. Other common problems with the esophagus (besides cancer) are "rings" or "webs"-- areas of protrusion into the normally hollow interior ("lumen") of the esophagus where food can get caught. A "stricture" is an area of narrowing of the esophagus, often from scarring from ingested chemicals (i.e. lye). Achalasia is a disease where the nerves in the esophagus don't coordinate swallowing properly, so food gets caught there. An inflammation is "esophagitis", caused by bacteria, virus, or fungi, drugs or radiation.
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