Alcohol is distributed throughout the water in the body. Tissues including the heart, brain, and muscles are exposed to the same concentration of alcohol as the blood. The exception is the liver, where exposure is greater because blood is received directly from the stomach and small bowel via the portal vein. Alcohol diffuses rather slowly, except into organs with a rich blood supply such as the brain and lungs.
The liver will eliminate more than 90% of alcohol. Approximately, 2-5% is excreted unchanged in urine, sweat, or breath.
Once alcohol is absorbed from the stomach into the bloodstream it can freely cross out of the blood and into nerve cells of the brain. Once in the brain it causes a chemical release that leads to pleasurable feelings, and it lessens inhibitions by depressing certain frontal lobe functions. Motor pathways become overactive, and blood sugar is processed less efficiently in the brain. As more and more alcohol molecules enter the membranes of the nerve cells, sedating effects develop. The effects of alcohol intoxication are relatively predictable based on measured blood alcohol content.
The levels of enzymes that process alcohol spike in the evening and are at their lowest at lunch. A glass of wine at lunch can feel much stronger than one at dinner.