42Look at the pelvis from the side. We will look at the muscles and ligaments on the side wall of the pelvis.You will see where the levator ani muscles originate.You will also see the critical dimensions of the pelvis.
54Look at the pelvis from the front again. Imagine a ‘coronal’ plane through the middle of the pelvis.You will see the rectum coming through the pelvis.You will see where the levator ani muscles originate.You will see which structures form the pelvic diaphragm.
77Keep looking at the pelvis from below. Imagine the anatomy as you descend below the pelvic diaphragm.The following slides show the structures encountered as you continue to descend through the pelvis.
98The following slides will demonstrate the orientation of the fetal skull as it passes through the pelvis in normal labour.
99the head flexes as the uterus contracts passengerthe head flexes as the uterus contractsthe head descends and engages in the pelvisthe leading part approaches the ischial spines
100passenger the occiput starts to rotate anteriorly the occiput reaches the pelvic floor (levator ani)internal rotation continues to achieve an occipito-anterior position
101the occiput clears the symphysis pubis the head extends to deliver passengerthe occiput clears the symphysis pubisthe head extends to deliver
102the head sits on the maternal perineum passengerthe head sits on the maternal perineum
103the fetal head realigns itself with the fetal shoulders - restitution passengerthe fetal head realigns itself with the fetal shoulders - restitution
104the head therefore continues to rotate - external rotation passengerthe shoulders contact the pelvic floor and rotate so that the bisacromial diameter lies in an anteroposterior orientationthe head therefore continues to rotate - external rotation