External orifice of the uterus
Encyclopedia
The external orifice of the uterus (or ostium of uterus, or external os) is a small, depressed, somewhat circular aperture on the rounded extremity of the vaginal portion of the cervix
. Through this aperture, the cervical
cavity communicates with that of the vagina
.
The external orifice is bounded by two lips, an anterior and a posterior. The anterior is shorter and thicker, though it projects lower than the posterior because of the slope of the cervix. Normally, both lips are in contact with the posterior vaginal wall.
In the prepartum condition, or prior to pregnancy, the external orifice has a rounded shape when viewed through the vaginal canal (as through a speculum
). Following parturition, the orifice takes on an appearance more like a transverse slit or is "H-shaped".
Vaginal portion of cervix
The vaginal portion of the cervix projects free into the anterior wall of the vagina between the anterior and posterior fornices vaginae.On its rounded extremity is a small, depressed, somewhat circular aperture, the external orifice of the uterus, through which the cavity of the cervix...
. Through this aperture, the cervical
Cervix
The cervix is the lower, narrow portion of the uterus where it joins with the top end of the vagina. It is cylindrical or conical in shape and protrudes through the upper anterior vaginal wall...
cavity communicates with that of the vagina
Vagina
The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...
.
The external orifice is bounded by two lips, an anterior and a posterior. The anterior is shorter and thicker, though it projects lower than the posterior because of the slope of the cervix. Normally, both lips are in contact with the posterior vaginal wall.
In the prepartum condition, or prior to pregnancy, the external orifice has a rounded shape when viewed through the vaginal canal (as through a speculum
Speculum
The term speculum, Latin for "mirror", and its plural specula, may refer to:* Speculum , a medical tool used for examining body cavities* Speculum , a journal of medieval studies published by the Medieval Academy of America...
). Following parturition, the orifice takes on an appearance more like a transverse slit or is "H-shaped".