The Skeletal and Muscular Systems
With Sophie and Marcus, Biology & Physiology Specialist
Key Takeaways
- Pregnancy alters both systems — ligaments loosen under relaxin, the centre of gravity shifts, and the muscles of the pelvic floor and uterus are central to birth itself.
- Support, protection, movement, mineral storage, and blood cell production.
- In pregnancy, calcium is mobilised from bone to meet fetal demands — which is why adequate dietary calcium matters throughout.
- The shape and dimensions of the bony pelvis determine whether vaginal birth is mechanically possible.
- Midwives learn pelvic assessment because a contracted pelvis can necessitate caesarean section.
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Full Transcript
Sophie: Today we're covering the skeletal and muscular systems. I'm Sophie, alongside Marcus, our Biology and Physiology Specialist. Marcus, how do these systems intersect with pregnancy?
Marcus: Profoundly. Pregnancy alters both systems — ligaments loosen under relaxin, the centre of gravity shifts, and the muscles of the pelvic floor and uterus are central to birth itself.
Sophie: Let's start with the skeleton. What are its core functions?
Marcus: Support, protection, movement, mineral storage, and blood cell production. In pregnancy, calcium is mobilised from bone to meet fetal demands — which is why adequate dietary calcium matters throughout.
Sophie: And the pelvis specifically is critical in obstetrics.
Why is the skeletal and muscular systems important in midwifery practice?
Marcus: The shape and dimensions of the bony pelvis determine whether vaginal birth is mechanically possible. Midwives learn pelvic assessment because a contracted pelvis can necessitate caesarean section.
Sophie: What about the three types of muscle tissue?
Marcus: Skeletal muscle is voluntary and attaches to bone — important for posture and pushing in second stage. Smooth muscle is involuntary — it lines the uterus, blood vessels, and gut. Cardiac muscle is found only in the heart.
Sophie: The uterus being smooth muscle is significant for labour, isn't it?
Marcus: Very. Smooth muscle contracts involuntarily in response to oxytocin. Syntocinon — synthetic oxytocin — augments these contractions. Tocolytic drugs like nifedipine inhibit them to halt preterm labour.
How does the skeletal and muscular systems work in a healthcare context?
Sophie: How does relaxin affect the musculoskeletal system?
Marcus: Relaxin softens ligaments — especially the pubic symphysis and sacroiliac joints — to allow pelvic widening for birth. This can cause pelvic girdle pain, which affects around one in five pregnant women.
Sophie: And pelvic floor muscles — these come up constantly in postnatal care.
Marcus: They're the scaffold supporting the pelvic organs. Childbirth can stretch or damage them, leading to incontinence or prolapse. Pelvic floor exercises are evidence-based prevention.
Sophie: So understanding musculoskeletal anatomy directly shapes how midwives advise and support women postnatally.
What should learners understand about the skeletal and muscular systems?
Marcus: Completely. From birth positioning to postnatal recovery and physiotherapy referral — this anatomy is clinically applied every day.