1. OBSTETRIC ANATOMY MIDW 201 BY ESTHER A. M. ANYIDOHO 17 TH NOV., 2014

2. COURSE OBJECTIVES By the end of the course students should be able to: 1.Describe the female and male reproductive systems 2.Describe the physiology of ovulation and fertilization 3.Describe the placenta and its functions 4.Describe the various types of female pelvis and their relationship in labour and delivery

3. THE FEMALE PELVIS Objectives: By the end of the session, students should be able to: a.List the parts of the female bony pelvis b.Describe each component part of the bony pelvis c.List the types of the female bony pelvis d.List 2 effects of each type of the female bony pelvis on labour and delivery

4. Female Bony Pelvis cont’d General description:  The bony pelvis is located between the trunk and the lower limbs of the body.  It articulates superiorly with the 5 th Lumbar vertebra  It articulates inferiorly with the coccygeal vertebrae which form part of it  It articulates laterally with the left and right femoral heads in a depression called the Acetabulum

5. The Female Bony Pelvis cont’d  The anterior border is the Symphysis Pubis.  Bones of the Bony Pelvis is made up of 4 bones: 1.The Sacrum 2.The Cocyx 3.Two Innominate bones These bones together make the bony pelvis the largest bone formation in the human body

6. The Female bony Pelvis cont’d The Sacrum: It is made up of 5 fused vertebrae. It is triangular in shape with the apex pointing downwards. It lies between the right and left innominate bones It articulates with the 2 innominate bones It has 4 pairs of foraminae (windows or holes). These communicate with the sacral canal. The foraminae serve as exit for nerves from the spinal cord at the level, blood vessels and lymphatic channels as well.

7. The Female Bony Pelvis cont’d The Sacrum has a hollow which is the anterior concave surface. The concavity of the hollow increases the capacity of the pelvis. It has a widened portion on each of the first sacral vertebra which are referred to as alae (wings). The Promontory is the centre point of the upper border of the first sacral vertebra. This protrudes over the hollow with the fifth lumbar vertebra.

8. The Female bony Pelvis cont’d The Sacral canal runs longitudinally through the sacrum and opens at the level of the fifth lumbar vertebra. The spinal nerves fan out through the canal at the level of the 2 nd and 3 rd sacral vertebrae to form the Cauda equina Obstetric Importance: Anaesthetic agent is introduced through the caudal canal to relieve pain from uterine contractions during labour. This causes temporal paralysis of the nerves leading to the relief of the pains.

9. The Female Bony Pelvis cont’d The Cocyx (Tail): This is four tiny fused vertebrae. It is also triangular in shape. The base articulates superiorly with the inferior aspect of the 5th sacral vertebra. It serves as an attachment for muscles and ligaments. Obstetric importance: In the female, during the second stage of labour, the cocyx tips backwards to widen the exit of the birth canal for the head of the baby to pass through.

10. The Female Bony Pelvis cont’d  The Innominate Bones: These bones form the lateral aspects of the bony pelvis.  Each bone developed from 3 primary centres of ossification. This formed three bones thus – Ilium, Ischium and Pubis.  The 3 bones meet in cup-shaped depression called Acetabulum

11. The Female Bony Pelvis cont’d The ILIUM is the biggest and the uppermost of the innominate bones. The uppermost end is called the Iliac crest which is easily palpable (the waist) by the hands resting on the hips. It has four projections, two anterior and two posterior called spines. The ilium articulates anteriorly with the antero-superior iliac spine and posteriolry, with the postero-superior iliac spine.

12. The Female Bony Pelvis cont’d The Antero-inferior lies approximately 2.5cm below the antero-superior iliac spine. The postero-superior iliac spines are located in the dimples at the lower back of the individual. The postero-inferior iliac spines mark the upper border of the Greater Sciatic Notch through which the Sciatic Nerves pass. The ilium forms the upper two-fifth of the Acetabulum.

13. The Female Bony Pelvis cont’d The inner concave surface is smooth and the outer surface is rough for attachment of the gluteal muscles forming the buttocks. The ISCHIUM is the lowest portion of the innominate bone. It forms the lower two-fifth of the acetabulum. It has two projections called the Ischial spine and the Ischial Tuberosity respectively. The Ischial spine terminates into the Lesser Sciatic Notch.

14. The Female Bony Pelvis cont’d The Ischial Tuberosity is the thickened portion of the Ischium on which the weight of the body rests in a sitting position. The Ischial spine separates the Lesser Sciatic Notch from the Greater Sciatic Notch. The PUBIS is the smallest bone of the innominate bone. It forms the lowest one-fifth of the Acetabulum.

15. The Female Bony Pelvis cont’d There are two Pubic bones which are united anteriorly to form the a square-shaped pubic bones. The two bones are fused together by a pad of cartilage in the middle, called the Symphysis Pubis. The Superior Pubic Ramus forms the upper portion. It unites with the ilium to form the Iliopectineal eminence.

16. The Female Bony Pelvis cont’d The right and left descending Rami form the Pubic Arch. Its importance is during the birth of the baby, it widens out. The Ischium and the Pubis surround a foramen called the Obturator Foramen

17. The Female Pelvis cont’d Types of Pelves: The classification of the pelvis is made according to shape of the brim. The pelvic brim has measurements which allow the passage of the foetal head with no difficulty. However, if any of the measurements is reduced by 1cm, then there will be difficulty for the passage of the foetal head.

18. The Female Bony Pelvis cont’d There are four main types of pelves 1.Gynaecoid 2. Android 3.Anthropoid 4.Platypelloid  The Gynaecoid pelvis is said to be the ideal for childbearing. It is the true female pelvis

19. Female bony pelvis cont’d Features:  The Brim – rounded  Fore pelvis is generous  Cavity – the sacrum is well curved with straight walls  Outlet –Ischial spines are rounded and blunt, not prominent Effect on labour: It enables the foetus to present with its most rounded part of the head - occiput

20. The female bony pelvis cont’d Anteriorly, because of the rounded brim. This position is most favourable at the start of labour.  The Android Pelvis: This resembles the male pelvis. The bones are heavier than the that of the Gynaecoid pelvis. Features:  The Brim – heart-shaped, making the fore pelvis narrow. The transverse diameter does not cross

21. Female Bony pelvis cont’d  The centre of the Anteroposterior (AP) diameter, but it is much more nearer the sacrum. It is funnel-shaped.  The Cavity – it is deep with straight hollow of the sacrum and side walls. The sacrum is longer than that of the Gynaecoid pelvis. The Greater Sciatic Notch too is narrower than that of the Gynaecoid pelvis.  The Outlet – The available space is reduced due to the acute subpubic angle.

22. Female bony pelvis cont’d  The Ischial spines are sharp and turn inwards leading to the reduction of the transverse diameter.  Effect on labour: Because the pelvis is more rounded in the posterior angle, the foetus tends to lie with its occiput in the right or left posterior quadrant of the pelvis. This makes labour to be prolonged.

23. Female bony pelvis cont’d It may result in deep transverse arrest of the head as it is caught up in the deep posterior pelvis. Internal rotation becomes difficult, due to the prominent ischial spines. This pelvis can be found in 20% of women population.  The Anthropoid Pelvis: This is seen in very tall long-legged women; especially, the whites and South African women.

24. Female Bony Pelvis cont’d  The Brim – Oval in shape. Long AP diameter. Reduced transverse diameter.  The Cavity – It is deep. Fore pelvis is narrow, with divergent sidewalls and blunt ischial spines. Transverse diameter is reduced with wide Sciatic notch.  The Outlet is adequate in all diameters. The subpubic angle is greater than 90 degrees.

25. Female bony Pelvis cont’d Effects on labour: The foetus lies in the AP of the pelvic brim. The occiput tends to lie in the hollow of the sacrum rather than directly anterior. The foetus remains in that position till delivery. Thus unreduced occipito posterior position that is face-to-pubis instead of face- to-perineum. It has a higher incidence of OPP and breech presentation. Can be found in 25% of women.

26. Female Bony Pelvis cont’d  The Platypelloid Pelvis – Flat pelvis.  The Brim – Kidney-shaped. AP is reduced and transverse diameter is increased.  The Cavity – It is flat and shallow.  The Outlet – Subpubic angle is more acute with reduced available space, because the inferior pubic rami are in a much more sharper angle which is wider. The ischial spines are too blunt. Found in 5% of women.

27. Female bony pelvis cont’d Effect on labour: The engagement of the foetal head is difficult. The foetus usually presents with the long diameter of the head – biparietal diameter across the transverse diameter of the pelvic brim which is roomy. There is early rupture of the membranes due to the high presenting part. There is a possibility of cord prolapse. Engagement of the head may lead to lateral tilting of the head,

28. Female Bony Pelvis cont’d b. Face presentation c. Delivery by Caesarean Section as a result of the floating high head. Other types of Pelves: 1. Justo-minor Pelvis: Miniature Gynaecoid pelvis. All the diameters are proportinately reduced. Mostly found in women with small stature – 1.5m in height. They can deliver normally if the foetus is proportionate to the pelvis otherwise, is C/S.

29. Female bony pelvis cont’d 2. Robert Pelvis- The sacrum has no alae and therefore contracted in all diameters. Delivery is by C/S 3. Naegele Pelvis – The sacrum has only one ala giving it its obliquity. It may be due to congenital abnormality or injury. Delivery is C/S.

30. JOINTS AND LIGAMENTS OF THE PELVIS There are four pelvic joints with their supporting ligaments.  Two Sacro-iliac joints  The Symphysis Pubis  The Sacrococcygeal joint The Sacro-iliac joints lie between the bodies of the first and second sacral vertebrae and the articular surfaces of the ilium each side. These joints have the body weight transmitted through them and are subjected to great strain.

31. Pelvic Joints and Ligaments Supporting Ligaments- a.Strong sacro-iliac ligaments surround the joints. b.The Sacrotuberous ligament stretches from the lower border of the sacrum to ischial spine. They aid in the restriction of sacral movement.