This sphincter opens automatically only in connection with the act of swallowing.
The sphincter is kept in a state of tonic contraction by a nervous centre situated in the lumbar portion of the spinal cord.
If the nates present, the state of the sphincter ani will be a sure guide in ascertaining whether the child be alive or not.
Thus, Jules Aron reports from the epidemic at Joigny a case of recovery after complete paralysis of the sphincter ani.
At its posterior end it terminates in the pylorus, a fleshy ring or sphincter formed of annular muscular fibres.
These are usually fibrous when situated below, or vascular when situated above, the sphincter ani muscle.
Cases in which the perineum is apparently intact, but in which the sphincter is not united (Figs. 35, 36).
After the operation return the parts within the sphincter and cut off any tabs of redundant integument with scissors.
They also had triangular-shaped mouths which worked somewhat on the sphincter method.
The entrance into these compartments can be closed by a sphincter muscle after they are filled with water (Fig. 84).
1570s, from Middle French sphincter, from Late Latin sphincter "contractile muscle," from Greek sphinkter "band, anything that binds tight," from sphingein "to squeeze, bind," of unknown origin. First used in anatomical sense by Galen.
sphincter sphinc·ter (sfĭngk'tər)
A ringlike muscle that normally maintains constriction of a body passage or orifice and that relaxes as required by normal physiological functioning. Also called anatomical sphincter.