Pelvis and perineum Flashcards
When do the ischium, ilium and pubis fuse and where?
Adolescence and acetabulum
What type of joint is the pubic symphysis?
Secondary cartilaginous
What type of joint is the sacroiliac joint?
Plane synovial
Which two ligaments are important in stabilising the pelvis?
What two spaces do the two ligaments form?
Sacrospinous - sacrum + coccyx to ischial spine
Sacrotuberous - sacrum to ischial tuberosity
Form two foramina - greater sciatic and lesser sciatic
What structures pass through the greater sciatic foramen?
Sciatic nerve
Pudendal nerve
Superior and inferior gluteal nerves
Lateral rotator muscles of hip
Which structure does piriformis pass through? O and I
Greater sciatic foramen
Originates from sacrum and inserts on greater trochanter
What nerve provides motor and sensory supply to perineal region and external genitalia?
Pudendal nerve from sacral plexus
Course of pudendal nerve? What accompanies it?
Posterior through greater sciatic notch, anterior through lesser sciatic notch.
Courses with internal pudendal artery and vein
What does the conjugate diameter of the pelvic inlet refer to? What is it usually?
10.5-11cm from superior pubic symphysis to sacral promontory
What does the transverse diameter refer to and how is it important in fetal delivery?
Perpendicular to the conjugate diameter
13.5cm so more space for fetus head, which can turn laterally to fit through the pelvic inlet
What does the diagonal conjugate refer to? What is its significance clinically?
Used as an estimate for conjugate diameter. Insert fingers into vagina and measure length from middle finger touching sacral promontory to base of pubic symphysis
Approx 2cm greater than conjugate diameter
What is the midpelvic diameter and rough length? Significance?
Diameter between ischial spines, ~11cm
Most likely place for foetus to get arrested
What are the names of the two diameters of the pelvic outlet and what are their lengths? Significance for baby?
Intertuberous diameter (between ischail tuberosity) = 11cm Anteroposterior diameter (inferior pubic symphysis to inferior coccyx) = ~13cm
Now that A-P diameter is longer, the foetal skull needs to rotate again so that it’s facing posteriorly (foetal skull longest A-P)
Shape of male and female pelvic inlet + outlet?
Male = inlet heart shaped, outlet is narrow Female = inlet is oval (widest transverse) and wide, outlet is round
Shape of pelvic cavity female and male?
Male = funnel shaped Female = cylindrical
Subpubic angle of female and male?
Female = >80 degrees Male = <70 degrees
What are the borders of the pelvic inlet?
Posterior: Sacral promontory
Anterior: Pectineal line of pubis
Laterally: Arcuate line of ilium
What is the region above and below the pelvic inlet called, and what organs do they contain?
Above = greater pelvis, abdominal organs Below = lesser pelvis, reproductive and urinary organs
What is the pelvic floor formed by?
Muscles:
- levator ani
- coccygeus
What is the perineum and what separates it from the lesser pelvis?
Structures that lie inferior/superficial to the pelvic floor
Perineal membrane
What muscles form levator ani?
Pubococcygeus
Iliococcygeus
Innervation of pelvic diaphragm (muscles of pelvic floor)?
S3 and S4
O of levator ani?
Tendinous arc of obturator internus
What shape is the perineum and what defines the boundaries?
Diamond
Anterior: inferior pubic symphysis
Laterally: Ischial tuberosities
Posteriorly: Coccyx
