Lecture 12 - Pelvic cavity and floor Flashcards
Pelvic cavity: what is it, what is it surrounded by, what is it connected with superiorly and inferiorly, and what are its contents?
Funnel-shaped space
Surrounded by the bones of the pelvic girdle, muscles and ligaments
Continuous superiorly with the abdominal cavity
Separated inferiorly from the perineum by the pelvic floor
Contents:
* Terminal part of ureters
* Urinary bladder
* Rectum
* Pelvic genital organs
* Blood vessels, lymphatics and nerves
* Some abdominal viscera – consider which parts
Pelvic girdle: what does it consist of?
- 2 os coxa (innominate/hip bones, one on either side)
- Sacrum posteriorly
- Coccyx inferiorly
Os coxa: what is it and what does it consist of?
Innominate/hip bone
Three bones fused (at birth) at the acetabulum (the place where the head of the femur sits):
* Ilium - the top part, concave structure, allows organs to sit on it
* Ischium - the part that we sit on, located posteriorly and inferiorly
* Pubis - meets medially with the pubis on the other side, located anteriorly and inferiorly
Important landmarks of the os coxa
From superior to inferior (roughly):
* Iliac tubercle - transtubercular plane passes through here
* Iliac crest - The large ridge of the iliac
* Anterior superior iliac spine
* Greater sciatic notch
* Ischial spine - quite pointed
* Lesser sciatic notch
* Superior pubic ramus
* Pubic tubercle
* Body of pubis
* Inferior pubic ramus
* Ischial ramus
* Ischial tuberosity - where we sit on, more rounded
- Obturator foramen - hole within the os coxa
Important landmarks of the Sacrum and coccyx
- Sacral promontory - the part that sticks out in the middle as lumbar vertebrae meet
- Ala - ‘wing’, the superior parts that stick out to the sides
- Anterior sacral foramina - holes within the sacrum
- Coccyx - bones fused together, painful if bruised
- Sacral hiatus - the bottom of the median sacral crest
- Posterior sacral foramina - holes within the sacrum
- Median sacral crest - the ‘feelable’ spinal projections
Joints of the pelvis: what are they and what are their key aspects?
Lumbosacral joint:
* Cartilaginous joint between bodies of L5 and S1
* Synovial plane joints between articular facets of L5 and S1
Sacroiliac joints:
* Between articular surfaces of sacrum and ilium
* Compound joints (part synovial, part fibrous)
* Allow limited movement
Symphasis pubis:
* Secondary cartilaginous joint between the bodies of the pubis
* Loosens up in pregnancy, due to relaxin, and allows for increased movement
Ligaments of the pelvis: what are they and where are they located?
- Sacroiliac ligament (anterior, posterior and lateral) - strongest, sacrum/iliac crest
- Sacrotuberous ligament - sacrum/ischial tuberosity
- Sacrospinous ligament - sacrum/iliac spine
Sacrotuberous ligament
* Extends from the posterior ilium, lateral
sacrum and the base of the coccyx to the
ischial tuberosity
* Transforms the greater sciatic notch into a
large sciatic foramen
Sacrotuberous ligament
* Extends from the posterior ilium, lateral
sacrum and the base of the coccyx to the
ischial tuberosity
* Transforms the greater sciatic notch into a
large sciatic foramen
Sacrospinous ligament
* Extends from the lateral sacrum and coccyx
to the ischial spine
* Subdivides the large sciatic foramen into
greater and lesser sciatic foramina
Sacrospinous ligament
* Extends from the lateral sacrum and coccyx
to the ischial spine
* Subdivides the large sciatic foramen into
greater and lesser sciatic foramina
Muscles of the pelvic wall
Obturator
internus
Piriformis
Obturator internus
Origin – ilium, ischium & obturator membrane
Insertion – greater trochanter of femur
Action – lateral rotation of thigh
Innervation – nerve to obturator internus (L5,
S1 & S2)
Piriformis
Origin – Sacrum, sacrotuberous ligament
Insertion – greater trochanter of femur
Action – lateral rotation & abduction of thigh
Innervation – Nerve to pirformis (S1 & S2)
- Obturator internus
Origin – ilium, ischium & obturator membrane
Insertion – greater trochanter of femur
Action – lateral rotation of thigh
Innervation – nerve to obturator internus (L5,
S1 & S2) - Piriformis
Origin – Sacrum, sacrotuberous ligament
Insertion – greater trochanter of femur
Action – lateral rotation & abduction of thigh
Innervation – Nerve to pirformis (S1 & S2)
True pelvis
False/greater pelvis –
Between the iliac crest and
the pelvic inlet
True/lesser pelvis –
Between the pelvic inlet
and the pelvic outlet
The pelvic cavity is bounded by the true pelvis
Pelvic inlet/brim
Sacral promontory
Ala
Linear
terminalis*
* Linear terminalis = arcuate line + pectineal line + pubic crest
Symphysis pubis
Pelvic outlet
Pubic
arch **
Ischial
tuberosity
Tip of coccyx Sacrotuberous ligament
** Pubic arch = ischial ramus & inferior pubic ramus of both sides + symphysis pubis
Watch leccy
Pelvic inlet/brim
Sacral promontory
Ala
Linear
terminalis*
* Linear terminalis = arcuate line + pectineal line + pubic crest
Symphysis pubis
Pelvic outlet
Pubic
arch **
Ischial
tuberosity
Tip of coccyx Sacrotuberous ligament
** Pubic arch = ischial ramus & inferior pubic ramus of both sides + symphysis pubis
Orientation of the pelvis
When stood in the anatomical
position the anterior superior iliac
spines are in the same vertical plane
as the anterior aspect of the pubis
Orientation of the pelvis
When stood in the anatomical
position the anterior superior iliac
spines are in the same vertical plane
as the anterior aspect of the pubis
Walls of the pelvic girdle
* Anteroinferior pelvic wall
* Lateral pelvic walls x 2
* Posterior pelvic wall (posterolateral & roof)
Walls of the pelvic girdle
* Anteroinferior pelvic wall
* Lateral pelvic walls x 2
* Posterior pelvic wall (posterolateral & roof)
Anteroinferior Wall
Formed by the pubic
body, superior and
inferior pubic rami and
the symphysis pubis
Anteroinferior Wall
Formed by the pubic
body, superior and
inferior pubic rami and
the symphysis pubis
Lateral wall
Os coxa
Obturator foramen covered by the
obturator membrane
Lined by obturator internus muscle
– note gap for blood vessels and
nerves to pass through
Covered by obturator fascia – note
tendinous arch
Lateral wall
Os coxa
Obturator foramen covered by the
obturator membrane
Lined by obturator internus muscle
– note gap for blood vessels and
nerves to pass through
Covered by obturator fascia – note
tendinous arch
Posterior wall
Sacrum and coccyx
Sacroiliac, sacrospinous &
sacrotuberous ligaments
Piriformis muscles
Posterior wall
Sacrum and coccyx
Sacroiliac, sacrospinous &
sacrotuberous ligaments
Piriformis muscles
Pelvic floor
Muscular partition that separates the pelvis from the
perineum
Formed from a funnel shaped muscular sheet (pelvic
diaphragm) covered by internal and external layers of
fascia
The urogenital hiatus is a gap in the anterior aspect
which provides a passage way for the urethra and
vagina
Supports the pelvic contents, resists increases in intraabdominal pressure and involved in urinary and faecal
continence
Pelvic floor
Muscular partition that separates the pelvis from the
perineum
Formed from a funnel shaped muscular sheet (pelvic
diaphragm) covered by internal and external layers of
fascia
The urogenital hiatus is a gap in the anterior aspect
which provides a passage way for the urethra and
vagina
Supports the pelvic contents, resists increases in intraabdominal pressure and involved in urinary and faecal
continence
Muscles of the pelvic diaphragm
Levator Ani (three parts)
* Puborectalis
* Pubococcygeus
* Iliococcygeus
Coccygeus
Muscles of the pelvic diaphragm
Levator Ani (three parts)
* Puborectalis
* Pubococcygeus
* Iliococcygeus
Coccygeus
Puborectalis
Fibres attach to body of pubis on one side, extend backwards to form a sling
around the anorectal junction and pass forward to insert into pubic body on the
other side. The most medial fibres form the pubourethralis and pubovaginalis
(female) or pubourethralis and puboprostalis (male).
Plays an important role in maintaining faecal continence and urinary continence
(female)
Inferior v
Puborectalis
Fibres attach to body of pubis on one side, extend backwards to form a sling
around the anorectal junction and pass forward to insert into pubic body on the
other side. The most medial fibres form the pubourethralis and pubovaginalis
(female) or pubourethralis and puboprostalis (male).
Plays an important role in maintaining faecal continence and urinary continence
(female)
The arrangement of puborectalis around the anorectal junction forms an angle between the
rectum and anal canal. The lower end of rectum is flattened over upper aspect of the anal
canal which helps prevents descent of the faeces.
During defaecation the puborectalis relaxes and the anorectal angle straightens
Pubourethralis encircles the urethra and assists the urethral sphincter at the end of micturition
Pubococcygeus
Origin – body of pubis and anterior tendinous arch
Insertion – coccyx, perineal body, walls of vagina or prostate, rectum and anal
canal
Innervation – Ventral ramus of S3 & S4
Pubococcygeus
Origin – body of pubis and anterior tendinous arch
Insertion – coccyx, perineal body, walls of vagina or prostate, rectum and anal
canal
Innervation – Ventral ramus of S3 & S4
Iliococcygeus
Origin – posterior tendinous arch & ischial spine
Insertion – coccyx and anococcygeal body
Innervation – S3 & S4
Iliococcygeus
Origin – posterior tendinous arch & ischial spine
Insertion – coccyx and anococcygeal body
Innervation – S3 & S4
Coccygeus
Origin – ischial spine
Insertion – inferior end of sacrum
Innervation – S3 & S4
Coccygeus
Origin – ischial spine
Insertion – inferior end of sacrum
Innervation – S3 & S4
Vids to watch
3.4.1 Lower parts of the bony pelvis (4.11 min)
https://aclandanatomy.com/MultimediaPlayer.aspx?multimediaId=10528325
3.4.2 Major ligaments of the bony pelvis (3.4.2 min)
https://aclandanatomy.com/MultimediaPlayer.aspx?multimediaId=10528331
3.4.4 Muscles of the pelvic wall (2.09 min)
https://aclandanatomy.com/MultimediaPlayer.aspx?multimediaId=10528329
3.4.5 Muscles of the pelvic diaphragm from above and side (4.18 min)
https://aclandanatomy.com/MultimediaPlayer.aspx?multimediaId=10528333
3.4.5 Muscles of the pelvic diaphragm from below (3.46 min)
https://aclandanatomy.com/MultimediaPlayer.aspx?multimediaId=10528335
