Anatomy Of The Bony Pelvis Flashcards
What are the main functions of the bony pelvis?
- support of upper body when standing/sitting
- transfer weight from spine to femurs to stand/walk
- attachments of abdominal muscles and muscles of locomotion
- external genitalia attachment
- protection of pelvic organs/ vessels
- passage for childbirth
What bones are included in the bony pelvis?
- 2 hip bones (ilium/ischium/pubis)
- sacrum
- coccyx
What bone is part of the bony pelvis that is not included in the pelvic girdle?
Coccyx
What are the main bony landmarks of the ilium?
- iliac crest
- iliac fossa (where illiacus muscle attaches)
- Anterior Superior and Inferior iliac spines
- Posterior Superior and Inferior iliac spines
What are the main bony landmarks of the ischium?
- Ischiopubic Ramus (where the two bones join)
- Ischial tuberosity (bony bit that you are sitting on)
- Ischial spine (attachment of hamstring muscles)
What bony landmarks can be found on the pubis?
- ischiopubic ramus
- pubic arch and sub pubic angle
- superior pubic ramus
- Pubic tubercle (where superior pubic rami join)
Which is more superior, the pelvic inlet or outlet?
Pelvic inlet
What bones make up the pelvic inlet and line the pelvic brim?
- sacral promontory (sticks forward => prominent)
- ilium
- superior pubic ramus
- pubic symphysis
What bones make up the pelvic outlet?
Ischiopubic ramus Pubic symphysis Ischial tuberosities Sacrotuberous ligaments Coccyx
(Imagine as an oval shape around these structures)
Where is the true pelvic cavity found?
Between the pelvic inlet and pelvic floor
What is considered the “false pelvis”?
The tops of ilium bone on each side are in the “greater/false” pelvis and not included in the “lesser/true” pelvis
The pelvic cavity is continuous with the abdominal cavity. TRUE/FALSE?
TRUE
What surface landmarks of the pelvis can you palpated externally?
Anterior:
- Iliac crest
- ASIS
- Pubic tubercle
- Pubic symphysis (on deep palpation)
Posterior:
- iliac crest
- Posterior superior iliac spine (PSIS)
- Ischial tuberosity
- Coccyx
Where does the inguinal ligament attach to the ilium and pubis?
Between ASIS and pubic tubercle
Name 3 joints found in the pelvis
Hip joint
Sacroiliac joint
Pubic symphysis
What type of joint is the hip joint?
Synovial (for movement)
What type of joint is the pubic symphysis?
Secondary cartilaginous
What type of joint is the sacroiliac joint?
Anterior part = synovial
Posterior part = syndemoses => fibrous
What is the function of the large number of ligaments found in the pelvis?
Ligaments are stretched across a joint to aid in stabilisation
Where does the sacrotuberous ligament attach?
Sacrum to Ischial tuberosity
Where does the sacrospinous ligament attach?
From sacrum to Ischial spine
What are the main functions of the sacrotuberous and sacrospinous ligaments?
- Stop the inferior sacrum moving forward and superiorly when weight is suddenly transferred through the spine
- form the greater and lesser sciatic foramen
The pelvic ligaments are stiff during pregnancy. TRUE/FALSE?
FALSE - they relax during pregnancy
What covers most of the obturator foramen?
Obturator membrane
- does not cover superior aspect where the obturator canal is
What travels through the obturator canal?
Obturator Nerve and vessels
How does the pelvis normally fracture?
In more than one place due to the ring structure
What is the main concern after pelvic trauma which has caused a pelvic fracture?
Haemorrhage OR damage to pelvic organs
What make a females pelvis different from a males pelvis?
- AP and transverse diameters = larger
- Suprapubic angle and pubic arch = wider
- pelvic cavity is more shallow in height (to stop the baby’s head being surrounded by bone)
- sacrum angled more vertically to allow easier passage of baby in pregnancy
Some patients can have a persistent frontal suture. TRUE/FALSE?
TRUE
Why are the fontanelles clinically relevant during childbirth?
Target allow moulding of the foetal skull
=> bones move over each other to make skull smaller
What is the possible clinical relevance of fontanelles after birth?
Can see evidence of Raised ICP at these sites
- useful site for shunt insertion
Moulding can cause babies to be born with misshapen heads. TRUE/FALSE?
TRUE
This will return to normal after a few days
When does the anterior fontanelles typically disappear due to fusion of bones?
18 months -> 2 years
What makes up the diamond shaped vertex area of a baby’s head?
Anterior and posterior fontanelles and parietal eminences form the outline
Which diameter of the baby’s head should be largest?
Occipitofrontal diameter should be larger than biparietal diameter
Describe the AP and transverse diameter as you move from the pelvic inlet to pelvic cavity and pelvic outlet and which way the baby’s head should be orientated in each.
Pelvic inlet - transverse diameter > AP diameter
=> baby’s head faces R or L
Pelvic cavity - Baby rotates and flexes it’s head towards its chin
Pelvic outlet - AP diameter is wider than transverse => baby leaves pelvis in occipitoanterior position (facing the back)
Foetal head EXTENDS during birth
What further rotation must be carried out once a baby’s head has been delivered?
Rotated to align shoulders with larger AP diameter
R shoulder usually delivered first
L shoulder then delivered after
