THE PELVIS

Question 0

What are the 3 joints of the pelvis and what type of joint is each one?

Answer 0

1) The sacroiliac (synovial)
2) Intervertebral disc (fibrous)
3) Pubic symphysis (cartilaginous)

Question 1

Which bones fuse to form the hip (innominate) bone?

Answer 1

The ilium, ischium and pubis.

Question 2

what are the superior and inferior boundaries of the true pelvis ? What does true pelvis contain?

Answer 2

superior: pelvic inlet
inferior: pelvic outlet (inferior pelvic aperture)

contains: rectum, bladder, reproductive organs

Question 3

The false pelvis is also called the ____ and lies ____ to the ________ and is flanked by the _____. it is part of the ____ and contains ______, ______ and ____

Answer 3

greater pelvis 
superior
superior pelvic aperture (pelvic brim/inlet)
Ala of iliac bones
abdomen
appendix, ileum, sigmoid colon

Question 4

pelvic outlet boundaries (4)

Answer 4

pubic symphysis

ischial tuberosities

tip of coccyx

sacrotuberous ligament

PITS

Question 5

How is the superior pelvic aperture tilted?

Answer 5

Anteriorly since the ASIS and pubic symphysis are in the same vertical plane

Question 6

What are the various diameters (conjugates) of the pelvis and between what bony landmarks do they extend?

Answer 6

1) Diagonal conjugate: sacral promontory to inferior aspect of pubis
2) obstetric (true) conjugate: 2 cm shorter than the diagonal
3) midpelvic (transverse) congugate: distance between ischial spines.

Question 7

Which one, measured per vagina, is considered critical in obstetrics? Why?

Answer 7

The diagonal conjugate is measured per vagina from which the smaller - and more critical - obstetric conjugate is derived. The shortest diameter however, is the transverse conjugate.

Question 8

Define the attachments of the sacrotuberous and sacrospinous ligaments.

Answer 8

Sacrotuberous: dorsal aspect of sacrum to ischial tuberosity

Sacrospinous: lateral aspect of the sacrum to the ischial spine.

Question 9

What two foramina are formed by these structures?

Answer 9

Greater (via sacrospinous lig.) and lesser (via sacrotuberous lig.) sciatic foramena.

Question 10

Name the muscles that form the walls of the pelvis?

Answer 10

Obturator internus and piriformis.

Question 11

What are the attachments of the muscles that form the walls of the pelvis?

Answer 11

Obturator internus: rim of obturator foramen to greater trochanter

Piriformis: vertebrae S1-3 to greater trochanter. Lateral rotator of femur

Question 12

What is the innervation of these pelvic wall muscles?

Answer 12

Obturator internus: n. to obturator internus (L5, S1.2); and piriformis: (S1,2).

Question 13

What muscles form the floor of the pelvis?

Answer 13

Coccygeus and levator ani mm. (pubococcygeus + iliococcygeus - deeper fibers of the latter = puborectalis)

Question 14

Where do the muscles of the pelvic floor arise?

Answer 14

Coccygeus: ischial spine to lateral
margin of sacrum & coccyx; and

levator ani: pubis and tendinous arch of obturator internus to coccyx.

Question 15

What is the innervation of these pelvic floor muscles?

Answer 15

S2,3,4.

Pudenal nerve

Question 16

What do these muscles form a sling around?

Answer 16

Lower rectum/upper anal canal.

Question 17

What is the perineal body?

Answer 17

A connective tissue mass. Serves as an insertion point for muscles such as levator ani

Question 18

Why is the perineal body clinically important?

Answer 18

It is either incised, or avoided, in episiotomies during childbirth.

Question 20

90% of vessels that leave pelvis pass through _____

Answer 20

greater sciatic foramen

Question 21

What is the tendonous arch?

Answer 21

A thickening of the deep investing fascia on the inner surface of the obturator internus muscle

Question 22

What is subserous fascia?

Answer 22

Loose adipose fascia that interdigitates with the endopelvic fascia and acts as packing material

Question 23

Where is the perineal body located?

Answer 23

Between the anus and the base of the scrotum in the male or the posterior aspect of the vagina in the female.

Question 24

What is Alcock’s canal? Also known as pudendal canal

Answer 24

A canal compromised of investing fascia on the outer surface of the obturator internus muscle that allows passage of the pudendal nerve and internal artery and vein

Question 25

What is the endopelvic fascia?

Answer 25

It is continuous with the transversalis fascia and lines the pelvis. It condenses to form ligaments

Question 26

What are the four ligaments that tether the inferior parts of the organs to the pelvic wall?

Answer 26

1) Transverse cervical ligaments (cardinal ligaments)
2) uterosacral ligaments
3) Pubovesicle ligaments
4) puboprostatic ligaments