Abstract: An access port for use in a medical vessel comprises an inner frame (15) detachably mounted on an opening of a transparent hood (13) of the infant incubator. An outer frame (16) is slidably engaged to said inner frame (15). A flexible sheet (14) has one end connected to said inner frame (15) and another end connected to said outer frame (16). It is characterized in that a stopper (36) is carried by said outer frame (16).Another access port for use in a medical vessel comprising: a frame (52) having an opening (56); a horseshoe plate (58) pivotally supported on the frame (52) to open or close said opening (56); a lock mechanism (78) for locking said horseshoe plate (58) in situ which is closed; an inner side (66) provided on the horseshoe plate (58); a plurality of resilient pieces (72) mounted to said horseshoe plate (58) to close said inner side (66); and a holding means (74) provided on the horseshoe plate (58) to hold a member inserted through said plurality of resilient pieces (72).