Download to read offline
The Female Bony Pelvis. Description of same
- 1.
- 2. Objectives At the endof this 60 minutes presentation participants will be able to : • Define and list functions of the pelvis • Describe the bony pelvis • Dscribe the various shapes of the pelvis • Describe the conjugates of the pelvis
- 3. Definition The pelvis otherwiseknown as the bony pelvis is an incomplete basin shaped cavity made up of bones held together by ligaments and muscles The pelvis articulates with the 5th lumbar vertebra above and with the heads of the right and left femur in the corresponding acetabulum. The pelvis is the largest formation of bone in the body
- 4. Functions of thepelvis Facilitate childbirth Support and protect abdominal as well as pelvic organs Keeps body upright Allows bending and twisting at the waist
- 5. Description of thepelvic bone It is made up of 4 bones: 2 innominate bones The sacrum The coccyx
- 6. The Innominate bone(hip bone): Made up of 3 bones : Ilium Ischium Pubis
- 7. Ilium: The largestof the 3 bones. The upper inner portion is smooth & flared out, called the “iliac fossa”, which is smooth for the support of organs. The outer portion of the is rough and serves as an attachment area for muscles and ligaments The lower border of the iliac fossa terminates at the bottom at the iliopectineal line. The iliopectineal line ends at a ridge called the iliopectineal eminence.
- 8. Ilium Surmounting the iliumis the “iliac crest”, which is shaped like an elongated S. The iliac crest terminates anteriorly at the anterior superior iliac spine, 2.5 centimetres below it lies the anterior inferior iliac spine. Posteriorly, the crest terminates in the posterior superior iliac spine, 2.5 cm below, lies the posterior inferior iliac spine.
- 9. Ilium The posterior inferioriliac spines forms and marks the upper border of the greater sciatic notch through which the sciatic nerve passes. the ilium forms the upper 2/5th of the acetabulum.
- 10. Ischium: It isroughly C-shaped lower portion of the innominate bone. forms the lower 2/5th of the acetabulum. It has a thickend area or buttress of bones known as the ischial tuberosity, on which the body rests when sitting. Passing upward and outward 2.5cm from the ischial tuberosity is a projection, called the ischial spines, which divides the greater and lesser
- 11. The pubis Itis roughly v shaped, forms the anterior portion of the pelvis and is the smallest of the 3 innominate bones. forms the lowest 1/5th of the acetabulum. It has a body and 2 oar-like projections: the superior and inferior ramus The inferior ramus attaches to the ischium and the superior ramus to the ilium at the iliopectineal eminence
- 12. The pubis: Theright and left pubic bone which are square in shape meets anteriorly to form the symphysis pubis, fused together by a pad of cartilage. The 2 inferior rami going upward and inward, meets together to form a 900 angle, called the pubic arch. The pubis and the ishium meets together to form the ‘obturator foramen’. The pubis forms the upper portion and the ishium forms the lower portion.
- 13. Sacrum Is aconcave dagger shaped bone consisting of 5 fused sacral vertebrae. It lies posteriorly of the pelvis between the two innominate bones. The concaved shape of the sacrum forms a hollow called the sacral promontory. There are 4 pairs of holes, or foramina, pierce the sacrum through which sacral nerves, blood vessels and lymphatics pass
- 14. Sacrum The posteriorsurface is roughened to receive attachment of muscles It articulates at the apex with the coccxy at the sacrococcxyeal joint The sacrum articulates with the innominate bone at the sacroiliac joint. The lateral sacrum extends into wing-like projections called sacral ala.
- 15. Coccyx: It istriangular in shape with a vestigial tail Made up of 4 fused vertebrae. Its base lies uppermost and articulates with the sacrum. Muscle and ligaments are attached to its tip.
- 17. The Pelvis There arefour (4) pelvic joints: Two sacroiliac joints The symphysis pubis The sacrococcygeal joint
- 18. Sacroiliac joint (rightand left) - joins the the ala of the sacrum to the ilium and as a result connects the spine to the pelvis. Symphysis pubis - a cartilaginous joint between the anterior portions of the two pubic bones. Sacrococcygeal joint - forms where the base of the coccyx articulates with the tip of the sacrum.
- 19. Division of ThePelvis The pelvis is divided into two parts: the false pelvis and the true pelvis: The iliopectineal line marks the false pelvis from the true pelvis. Above the iliopectineal line is the false pelvis which supports the uterus during late pregnancy and direct the foetus into the true pelvis
- 20. Pelvic Brim The superiorcircumference forms the brim of the true pelvis, which is also known as the ‘the pelvic inlet’. The brim is round except where the sacral promontory projects into it. Fixed points on the pelvic brim are known as landmarks: Sacral promontory Sacral ala/wing Sacroiliac joint
- 21. Pelvic Brim Iliopectineal line Iliopectinealeminence Superior ramus of the pubic bone The upper inner border of the body of the pubic bone The upper inner border of the symphysis pubis
- 22. Pelvic Cavity The roundpelvic cavity extends from the brim of the pelvis above, to the pelvic outlet below. The anterior wall is formed by the pubic bones and the symphysis pubis. The posterior wall is formed by the curve of the sacrum. Its lateral walls are the sides of the pelvis, covered by the obturator internus muscles.
- 23. Pelvic Outlet The lowerpotion of the true pelvis and the space enclosed by it is called the outlet. Two outlets are indicated: the anatomical and the obstetrical. However, the obstetrical is of greater significance because it includes the narrow pelvic , through which the foetus must pass. lies between the sacrococcygeal joint, the two ischial spines and the lower border of the symphysis pubis. The outlet is diamond-shaped.
- 24. Pelvic outlet The landmarksincludes • the lower border of the symphysis • the ishial spines • the sacrospinous ligament • the lower border of the sacrum
- 25. Pelvic Diameters The divisionsof the true pelvis are demarked by measurements in diameters. Knowledge of the diameters of the normal female pelvis is essential in the practice of midwifery, because contraction of any of them can result in malposition or malpresentation of the presenting part of the foetus.
- 26. Pelvic Diameters • Thethree regions of the true pelvis (the brim, the cavity and the outlet), has four principal diameters: the anteroposterior diameter (AP), the transverse diameter and the two oblique diameters (right & left).
- 27. Pelvic diameter • Theanteroposterior (AP) or conjugate diameter is measured from the sacral promontory to the uppermost point of the symphysis pubis, averages 11 cm. • The transverse diameter extends across the greatest width of the brim; its average measurement is about 13 cm.
- 28. Pelvic diameter Each obliquediameter extends from the iliopectineal eminence of one side, to the sacroiliac articulation of the opposite side; its average measurement is about 12 cm. Each takes its name from the sacroiliac joint from which it arises, so the left oblique diameter arises from the left sacroiliac joint and the right oblique from the right sacroiliac joint.
- 29. Pelvic diameter Diameters ofthe cavity • The cavity is circular in shape and the diameters are all considered to be 12 cm. Diameters of the outlet • The outlet, which is diamond-shaped, has three diameters: • the anteroposterior diameter (AP), the oblique diameter • and the transverse diameter.
- 30. Pelvic diameter The outlet •The AP diameter extends from the lower border of the symphysis pubis to the sacrococcygeal joint. It measures 13 cm; as the coccyx may be deflected backwards during labour, this diameter indicates the space available during birth. • The oblique diameter, is said to be between the obturator foramen and the sacrospinous ligament. The measurement is taken as being 12 cm.
- 31. Pelvic diameter The outlet •The transverse diameter measures 10–11 cm. It is the narrowest diameter at the pelvic outlet and is said to be at the level of the ischial spines.
- 34. Types of Pelvis Fourtypes of Pelvis: Gynecoid (normal female pelvis) Android (male type pelvis) Anthropoid pelvis Platypelloid pelvis
- 35. Gynaecoid Pelvis (FemalePelvis) • Brim/Inlet: rounded • Cavity: well curved-sacrum • Outlet: Ischial spines are blunt (well rounded). • The sub-pubic angle is 90 ⁰ • Sciatic notch: rounded
- 36. Android Pelvis (MalePelvis) • The bones are heavier than the female pelvis and there are several distinctive features: • Brim: heart shaped making the pelvis very narrow. • Cavity: poorly curved-sacrum (almost straight) • Sacrum is long, giving it a deep, funnel appearance. • Outlet: narrow; Ischial spines are sharp and pointed inwards. Sub-pubic angle narrow (<90 ) ⁰ • Sciatic notch: narrow
- 37. Anthropoid Pelvis • Brim/Inlet:long oval shaped. It has a long anteroposterior diameter but a narrowed transverse diameter. • Cavity: is adequate in all diameters but is rather deep. • outlet: the Ischial spines are blunt • sub-pubic angle wide (>90 ) ⁰ • sciatic notch: wide
- 38. Platypelloid Pelvis (flatfemale pelvis) • This may due to hereditary factors,seen in african women with poor diet and customarily carries heavy weight on the head during the developmental years. • Brim: a short anteroposterior diameter and widened transverse diameter giving it a kidney shaped. • Cavity: is affected the same way as the brim but there is usually room for • the fetus head. • Outlet: Ischial spines are blunt. Sciatic notch: wide; Sub-pubic angle: >90 ⁰
- 41. Effects on theMechanism of Labour The Gynaecoid Pelvis The gynecoid pelvis is thought to be the most favorable pelvis type for a vaginal birth. This is because the pelvis is well rounded anteriorly, and the foetus presents with the most rounded part of the head (the occiput) anteriorly, which is the most favourable position at the start of labour. Therefore, the wide- open shape give the baby plenty of room during delivery and causes less to no trauma to the baby. .
- 42. Effects on theMechanism of Labour Android The narrower shape of the android pelvis can make labor difficult because the baby might move more slowly through the birth canal. Deep transverse of the head often occurs because of prominent ischial spine. There is an increased risk of forceps delivery while some pregnant women with an android pelvis may require a C- section due to its narrow outlet.
- 43. Effects on themechanism of labour Anthropoid The elongated shape of the anthropoid pelvis makes it roomier from front to back than the android pelvis. But it is still narrower than the gynecoid pelvis. This pelvis type is adequate for a vaginal birth, but the woman’s labor might last longer. Therefore the head often engages in the antero-posterior diameter, sometimes with the occiput posterior. The head descend through the pelvis in the occipito-posterior and born face to pubes.
- 44. Effects on themechanism of labour Platypelloid The shape of the platypelloid pelvis can make a vaginal birth difficult because the baby may have difficulty passing through the pelvic inlet, but once engaged, there should be no further difficulty. The long diameter of the head descends across the transverse diameter of the brim where most room is available. Because of the high head, the membranes will likely rupture early and there is the possibility of cord prolapse.
- 45. Effects on themechanism of labour Platypelloid Possible Outcomes • Asynclitism (means asymmetrical) may occur due to the fetus head being tipped towards one shoulder from being pushed to and fro by uterine contractions between the sacral promontory and symphysis pubis. This is defined as the "oblique malpresentation of the fetal head in labor".
- 46. Effects on themechanism of labour A face presentation may occur as the biparietal diameter of the fetal skull is held in the sacrocotyloid diameter of the pelvis brim, and uterine contractions cause the head to extend as it descend. Many pregnant women with a platypelloid pelvis requires a Caesarian section.
- 47. References • Marshall, J.E., & Raynor, M. D. (2020). Myles textbook for Midwives (17th ed.). Churchill Livingstone. • Verralls, S. (1997). Anatomy and physiology applied to obstetrics (3rd ed.). Edinburgh: Churchill Livingstone. • Seladi-Schulman, J. (2020, July 15). Types of pelvis shapes: 4 types and how they affect birth. Healthline. https://www.healthline.com/health/types-of-pelvis#giving-birth