Pluricellular organism

Question

After the phase of digestion is over next step includes the absorption which is done by cells of mucous membrane of intestine. For this task a large absorption surface can be taken as an advantage. How it is possible in small internal space of body of the  pluricellular organism in order to present a large intestinal surface?

Answer 1

Through the Evolution this problem is solved in two ways.

Simplest is long and tubular shape of the bowels which is around eight meters in extension, thus making possible that numerous small intestine loops fold closely. More proficient solutions are intestinal villi and microvilli of the mucosal membrane cells. The intestinal wall is not so smooth. The mucous membrane, all together with its submucosa, projects in the gut lumen such as glove fingers forming the invaginations and villi which increases the available surface for absorption. Additionally, the epithelial cells which  cover these villi have themselves various hairlike projections which is known as microvilli on the external face of their plasma membrane. Absorptive area of intestines is hence increased hundreds of times with the help of these solutions. In the jejunum and ileum there exist folds which have the function of increasing the absorption surface too.