During a normal vaginal delivery, various muscles and structures are involved to facilitate the process. Key muscles and muscle groups include:
1. **Uterine Muscles (Myometrium)**: The smooth muscles of the uterus play a crucial role in labor. They contract rhythmically to help dilate the cervix and push the baby through the birth canal.
2. **Pelvic Floor Muscles**: These muscles support the pelvic organs and stretch significantly during childbirth to allow the passage of the baby. The primary pelvic floor muscles involved are:
– **Levator Ani**: This includes the pubococcygeus, puborectalis, and iliococcygeus muscles. The levator ani group helps support the pelvic organs and assists in the birthing process.
– **Coccygeus**: This muscle also supports pelvic organs and works with the levator ani during delivery.
3. **Abdominal Muscles**: The rectus abdominis, transverse abdominis, and oblique muscles help increase intra-abdominal pressure during the pushing phase of labor, assisting in the descent and expulsion of the baby.
4. **Perineal Muscles**: These muscles, including the bulbospongiosus and ischiocavernosus, stretch and sometimes tear during childbirth. They are part of the lower pelvic floor and play a role in the final stages of delivery.
5. **Diaphragm**: Although primarily involved in breathing, the diaphragm works in concert with the abdominal muscles to help increase intra-abdominal pressure during the pushing phase of labor.
The coordinated efforts of these muscles, along with the assistance of hormones like oxytocin, enable the baby to move through the birth canal and be delivered vaginally.
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