Lecture 17 RH

Question 1

What are the divisions of the pelvis?

Answer 1

True ‘lesser’ pelvis

False ‘greater’ pelvis

Question 2

What is the difference between the pelvic divisions?

Answer 2

True pelvis is the part of the pelvis that contains most the pelvic viscera and bone anteriorly. (closed)

False pelvis is superior and has no anterior bone. (more open)

Question 3

What does the true pelvis contain?

Answer 3

True pelvis contains the termination of the GI tract, the urinary tract and genital tract.

Question 4

what divides the true and false pelvis from each other?

Answer 4

the iliopectineal line

Question 5

What are the main differences between male and female pelvises?

Answer 5

Female pelvis is wider than it is longer.

Female pelvis underneath pubic bone is wide and narrow in a male.

Males have a heart shaped inlet whereas females have a wide inlet mediolaterally.

In males ischial spine projects medially but in females it doesn’t project as far medially.

Outlet is narrow in males but both males and females have diamond shaped outlets

Question 6

What is the variation of the pelvis in females?

Answer 6

30% of females have android pelvises. (not ideally suited for childbirth and more funnel shaped)

50% of females have gynaecoid pelvis. (Inlet is wide mediolaterally)

the remaining 20% have eitehr anthropoid (similar to primates) and platypelloid ( in 2% of females and is flattened in shape)

Question 7

What is the common pelvis shape among males?

Answer 7

most males have an android pelvis. (funnel shaped going down)

Question 8

How is the sacrum and the pelvis orientated relative to the rest of the body?

Answer 8

Sacrum and upper pelvis is tilted forward so that the pubis is inferior compared to the upper part of the pelvis. Pubis is in line with lumbosacral joint.

Question 9

What is different in females compared to males about the tilt of the lumbar spine and pelvis?

Answer 9

Females have a more exaggerated lumbar lordosis and pelvic tilt than males.

Question 10

What fills the obturator foramen?

Answer 10

Obturator membrane

Question 11

What happens to the pelvic bones at the acetabulum?

Answer 11

Ischium posterior to pubis

Ilium meets the other bones at the acetabulum

Question 12

What is the function of the obturator membrane?

Answer 12

Membrane gives rise to muscles that pass through pelvic cavity and some to the lower limb.

Question 13

Why are the sciatic notches important?

Answer 13

2 sciatic notches important for transmission of nerves and blood vessels.

Question 14

What is the pelvic outlet divided into? What are the kinds of boundaries they contain?

Answer 14

outlet contains the urogenital triangle (anteriory) and the anal triangle (posteriorly).

urogenital triangle contains bony boundaries and anal triangle is ligamentous.

Question 15

What are the boundaries of the pelvic inlet?

Answer 15

from the top of the pubis to the sacroiliac joint

Question 16

What are the boundaries of the narrow pelvic plane?

Answer 16

from S4 to inferior pubis

Question 17

What is the narrow pelvic plane?

Answer 17

It is an important point that the fetus has to pass through for the pelvis

Question 18

What is the average size of the pelvic inlet and outlet in females?

Answer 18

average pelvic inlet size is 11 - 13.5cm

average pelvic outlet size is 11 - 11.5

*fetal skull is about 9.5cm in diameter

Question 19

How does the fetus present itself when moving through the narrow pelvic outlet?

Answer 19

pelvic floor rotates the fetus so that it faces anteroposteriorly in a way that makes it form the smallest possible diameter called vertex presentation.

If this doesn’t work out the skull can narrow itself to fit through outlet via fetonelles*.

Question 20

What happens to the pubic symphysis with aging?

Answer 20

ridges and grooves on pubic symphysis are smoothened with age.

Question 21

What are the arches of the pelvis and when are they important?

Answer 21

acetabuli to sacrum form the arch that bears weight during standing.

between pubic bones is important when sitting

Question 22

How does bone structure assist in weightbearing?

Answer 22

bones are organised in trabeculae from pelvis passing through upper femur which resist weightbearing forces. Other trabeculae for to the pubis to resist sitting forces.

Question 23

How is weight distributed when standing?

Answer 23

when standing weightbearing from above and below the pelvis follow the pelvic ring structure.

Question 24

Where is the center of rotation of the pelvis?

Answer 24

S2.

Question 25

What ligaments resist movement of the pelvis?

Answer 25

Sacrospinous between sacrum and ischial spine.

sacroiliac between ilium and sacrum

sacrotuberous between sacrum and ischial tuberosity

Question 26

Describe the reverse keystone effect:

Answer 26

Sacrum sinks forwards and downwards into the pelvis and posterior ligaments tighten and pull the iliac blades with them and so they stabilise the joint.

Question 27

What are the 2 joints that are important for connecting hip bones?

Answer 27

2 joints that connect hip bones:

Sacroiliac joint

Pubic symphysis

Question 28

What are the features of the sacroiliac joint?

Answer 28

part synovial (anteriorly), part fibrous (posteriory)

Contain auricular surfaces

Held together by powerful ligaments (interosseus, sacroiliac, sacrospinous, sacrotuberous ligaments, some ligaments from lumbar spine as well)

They resist nutation

Question 29

What is the degree of movement of the sacroiliac joint? When does this occur?

Answer 29

2 - 8 degrees; majority of movement at sacroiliac joint occurs when gettng up from bed.

Mothers may have a higher degree due to relaxin.

Question 30

What nerves supply the sacroiliac joints?

Answer 30

dorsal rami of L5 - S2 (posteriorly)

L3 - S1 (anteriorly)

Question 31

Where is pain from sacroiliac joint referred?

Answer 31

medial and lower buttock

Question 32

How does the posterior lumbar fascia assist in stabilising the sacroiliac joint?

Answer 32

posterior layer of lumbar fascia acts as an intermediary in transferring loads between trunk and lower limb muscle.

2 muscular slings assist in maintaining integrity of the sacroiliac joint;

Question 33

What is a potential problem on the pubic symphysis?

Answer 33

pubic symphysial joint may split during pregnancy.

Question 34

What kind of joint is the pubic symphysis?

Answer 34

secondary cartilaginous joint

Question 35

What kind of ligaments reinforce the pubic symphysis?

Answer 35

Superior (pubic), arcuate, anterior ligaments

Question 36

What muscles reinforce the pubic symphysis?

Answer 36

criss crossing fibers from rectus abdominis and transversus abdominis (+adductor longus and internal oblique)