Bony Pelvis Anatomy Flashcards by Joanna Mitchell

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

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What makes up the bony pelvis?

2 hip bones
Sacrum
Coccyx

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What is each hip bone made up of?

3 fused bones:
Ilium
Ischium
Pubis

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When will the ischium, pubis and ilium fusue?

Ischium to pubis around 4-8 years

Ilium and ischium around puberty

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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

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What are the bony features of the ischium?

Ischiopubic ramus (anterior)
Ischial spine (posterior)
Ischial tuberosity (posterior)

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Where do the ischium and pubic bone fuse?

Ischiopubic ramus

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What are the bony features of the pubis?

Ischiopubic ramus (inferior pubic ramus)
Pubic arch
Sub-pubic angle
Pubic tubercle
Superior pubic ramus

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What are the boundaries of the pelvic inlet?

Sacral promontory
Ilium
Superior pubic ramus
Pubic symphysis

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What are the boundaries of the pelvic outlet?

Pubic symphysis
Ischiopubic ramus
Ischial tuberosities
Sacrotuberous ligaments
Coccyx

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Where can you find the pelvic cavity?

Within the bony pelvis
Continuous with the abdominal cavity above
Lies between pelvic inlet and pelvic floor

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What separates the pelvic cavity from the perineum?

Pelvic floor

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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

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Where will the inguinal ligament attach?

Between ASIS and pubic tubercle

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Joints of the pelvis

SI joint
Hip joint
Pubic symphysis

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What type of joint is the SI?

Synovial and syndesmoses

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What type of joint is the hip joint

Synovial

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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