Bony Pelvis Anatomy Flashcards
What are the functions of the bony pelvis?
Support of upper body when sitting and standing
Transference of weight from vertebral column to the femurs to allow standing and walking
Attachment for muscles of locomotion and abdo wall
Attachment for external genitalia
Protection of pelvic organs, their blood and nerve supplies, their venous and lymphatic drainage
Passage for childbirth
What makes up the bony pelvis?
2 hip bones
Sacrum
Coccyx
What is each hip bone made up of?
3 fused bones:
Ilium
Ischium
Pubis
When will the ischium, pubis and ilium fusue?
Ischium to pubis around 4-8 years
Ilium and ischium around puberty
What are the bony features of the ilium?
Iliac crest Iliac fossa ASIS Anterior inferior iliac spine Posterior superior iliac spine Posterior inferior iliac spine
What are the bony features of the ischium?
Ischiopubic ramus (anterior) Ischial spine (posterior) Ischial tuberosity (posterior)
Where do the ischium and pubic bone fuse?
Ischiopubic ramus
What are the bony features of the pubis?
Ischiopubic ramus (inferior pubic ramus) Pubic arch Sub-pubic angle Pubic tubercle Superior pubic ramus
What are the boundaries of the pelvic inlet?
Sacral promontory
Ilium
Superior pubic ramus
Pubic symphysis
What are the boundaries of the pelvic outlet?
Pubic symphysis Ischiopubic ramus Ischial tuberosities Sacrotuberous ligaments Coccyx
Where can you find the pelvic cavity?
Within the bony pelvis
Continuous with the abdominal cavity above
Lies between pelvic inlet and pelvic floor
What separates the pelvic cavity from the perineum?
Pelvic floor
What are the palpable surface landmarks of the pelvis?
Anteriorly: iliac crest, ASIS, inguinal ligament, pubic tubercle and symphysis
Posteriorly: iliac crest, PSIS, sacrum, coccyx, ischial tuberosity
Where will the inguinal ligament attach?
Between ASIS and pubic tubercle
Joints of the pelvis
SI joint
Hip joint
Pubic symphysis
What type of joint is the SI?
Synovial and syndesmoses
What type of joint is the hip joint
Synovial
What type of joint is the pubic symphysis?
Secondary cartilagionus
What is the function of the ligaments of the pelvis?
Situated across a joint to assist in stabilisation
What are the 2 main ligaments of the pelvis?
Sacrotuberous; sacrum and ischial tuberosity
Sacrospinous; sacrum and ischial spine
What are the main function of the sacrotuberous and sacrospinous ligaments?
Ensure inferior part of sacrum is not pushed superiorly when weight is transferred vertically through vertebral column e.g. jumping or late pregnancy
Will ligaments relax or tighten in pregnancy?
Relax; due to hormone relaxin
What foraminae will the sacrotuberous and sacrospinous ligaments form?
Greater and lesser sciatic foraminae
What are the contents of the greater sciatic foramen?
Piriformis muscle
Superior gluteal vessels and nerve
Inferior gluteal and internal pudendal vessels
Nerves of sacral plexus; inferior gluteal nerve, pudendal nerve, sciatic nerve, nerve to obturator internus and nerve to quadratus fermosi
What are the contents of the lesser sciatic foramen?
Pudendal nerve
Internal pudendal vessels
Obturator internus
Nerve to obturator internus
Is the obturator foramen open or closed?
Completely covered by the obturator membrane apart from small opening called obturator canal
What passes through the obturator foramen?
Obturator nerve and vessels
What major blood vessels are present in the pelvis?
Common iliac artery (internal and external branches)
Common iliac vein
Sacral nerves/ plexus
Differences between male and female pelvis?
AP and transverse diameters are larger in female both at inlet and outlet
Subpubic angle is wider in females
Pelvic cavity more shallow in female
What is “moulding” of the foetal skull?
Refers to the movement of one bone over another to allow the foetal head to pass through the pelvis during labour
Presence of fontanelles and sutures allows for this
What are the different fontanelles in a foetal skull?
Anterior and posteiror
Is there 1 or 2 frontal bones on a foetal skull?
2; suture will obliterate in later life
What is the vertex?
Area of the foetal skull between the anterior and posterior fontanelles and the parietal eminences
What is longer in a foetal skull, the occipitofrontal diameter or the biparietal diameter?
Occipitofrontal; the head is longer than it is wide
What area of the pelvis is widest at the pelvic inlet?
Transverse is wider than the AP diameter
How should the foetal enter the pelvic cavity?
Transverse direction; so the OF diameter is facing the transverse diameter
What is the station referring to in labour?
Distance of the foetal head from the ischial spines
What does a negative station mean in labour?
Head is superior to the ischial spines
What does a positive station mean in labour?
Head is inferior to the ischial spines
What will the foetal head need to do whilst descending through the pelvic cavity?
Rotate
Be in a flexed position
What diameter is largest at the pelvic outlet?
The AP is wider than transverse
In what rotation should the baby be at the pelvic outlet?
Occipitoanterior (OA) with extension of the head
What needs to occur in labour once the head is delivered?
Rotation to allow for delivery of the shoulders
