Standing upright changed all that. Now any additional pressure on these vessels can make them swell and turn into hemorrhoids. Another theory speculates that hemorrhoids aren't swelling veins but actually sagging, blood-filled cushions. These cushions have two major functions. First, when engorged they help with continence, and second, they support the anal lining during a bowel movement.
Elastic tissue holds the cushions in place.
But due to aging, the constant downward pressure from chronic straining and the passage of hard stools, the tissue loses its elasticity, allowing the cushions to sag. Then you have hemorrhoids. Whether they're swelled veins, sagging cushions or a combination, there's plenty we can do about hemorrhoids, short of returning to our old quadruped ways. Although they can be distressing and sometimes very painful, hemorrhoids are relatively easy to treat and largely avoidable. But pain and bleeding can crop up if people persist in the habits that started the hemorrhoids in the first place.