Abstract: An access port for performing surgical procedures within an insufflated body cavity is disclosed. The port is formed from a duct that is inserted into the body cavity, the duct having a stiff sidewall to prevent collapse. The duct contains a flexible tube that has a constricted shape that forms a seal around a surgical instrument inserted through the duct. The tube has an inner membrane with a low coefficient of friction to facilitate passage of surgical instruments through the duct. The tube has an elastic outer membrane to bias it into the constricted shape. The tube may also be pressurized into the constricted shape by gas, gel or liquid. The tube itself may also form a seal in the absence of the tool, or a second seal, such as a duckbill valve, may be positioned within the duct.