The lining of the anal canal contains three soft, spongy pads of tissue that act as an extra seal to keep the canal closed until you go to the lavatory. The lining of the gut is very slimy (so that faeces can pass along easily); the extra seal stops the slime (mucus) from leaking out. The pads contain a network of tiny blood vessels. These pads are also important in contributing to one’s ability to distinguish between solid, liquid or gas in this area.

 

 

 

Abutment:

n engineering, abutment refers to the substructure at the ends of a bridge span or dam whereon the structure's superstructure rests or contacts.^[1] Single-span bridges have abutments at each end which provide vertical and lateral support for the bridge, as well as acting as retaining walls to resist lateral movement of the earthen fill of the bridge approach. Multi-span bridges require piers to support ends of spans unsupported by abutments. Dam abutments are generally the natural valley walls but may be artificial in order to support arch dams such as Kurobe Dam in Japan.

The term may also refer to the structure supporting one side of an arch,^[] or masonry used to resist the lateral forces of a vault.^] The word derives from the verb "abut", meaning to "touch by means of a mutual border