Pelvis and external genitalia Flashcards
(85 cards)
What parts make up the pelvic brim?
The pelvic brim is formed by the continuity of the pubic crest, pectineal line of the pubis, arcuate line of the ilium, and ala and promontory of the sacrum
Sex differences between male and female pelvis?
o Male- more acute subpubic angle, females – wider subpubic angle
o In men- more prominent sacral promontory – creates heart shaped inlet, in females – it is less prominent and oval shaped inlet results
What are the walls of the pelvis?
o Pelvic floor (pelvic diaphragm) – constitute of muscles: obturator internus, piriformis, levator ani and coccygeus
o Side walls: hip bones, clad by obturator internus and its fascia
o Posterior wall: sacrum, piriformis passing laterally into the greater sciatic foramen
o Anterior wall: aponeurosis of the three abdominal muscles
What are the Ligaments of the sacroiliac joint
• The ligaments are stronger posteriorly and weak anterior
o The ventral sacroiliac ligament joins the two bones above and below the pelvic brim
It is stronger in females and indents the preauricular groove in females
o On the dorsal surface a group of ligaments constitute the interosseous sacroiliac ligament, which are attached to deep pits on the posterior surface of the lateral mass of the sacrum
The most superficial fibres constitute the dorsal sacroiliac ligaments
o The posterior rami of the spinal nerves and vessels pass between these interosseous and dorsal ligaments
What factors contribute to joint stability of the sacroiliac joint?
- Gliding movements opposed by dorsal sacroiliac ligaments and iliolumbar ligaments acting on L5
- Opposing forward rotation of the sacral promontory around the joint are the sacrotuberous and sacroiliac ligaments
- Whilst ligaments are intact along with the irregular bony surfaces, whilst intact prevent rotation and gliding – but are entirely dependant on this
- Sacroiliac ligaments soften at the end of pregnancy to permit some sacral rotation
What are the origins, insertions and anatomical relations of the Sacrotuberous ligament:
Origin: posterior border of the ilium between the superior and inferior posterior iliac spines, transverse tubercles of the sacrum below the auricular surface and upper part of the coccyx
insertion: the ischial tuberosity.
— The falciform process is a prolongation forwards of the ischial attachment onto the ischial ramus
Relations:
- ligament is the degenerated origin of the long head of biceps femoris – to which the lower part of the ligaments continues as
- is pierced by the perforating cutaneous nerves, branches of the inferior gluteal artery and the coccygeal nerves
- lowest fibres of gluteus maximus are attached to the posterior surface of the ligament
Origins, insertions and relations of the sacrospinous ligament
- Origin: attached to the base of the sacrum and the upper part of the coccyx
- Insertion: ischial tuberosity
- relations:
- – the coccygeus muscle lies on its pelvic surface
- – the sacropsinous ligament lies on the pelvic surface of the sacrotuberous ligamnet - and together they enclose the lesser sciatic foramen
Origins and insertions of the iliolumbar ligament?
Origin: transverse process of L5- from here it is shaped like a sideward V with upper and lower bands fanning outwards
Insertion:
– upper band passes to the iliac crest, giving partial origin to the quadratus lumborum and blending more lateral with the lumbar fascia
– The lower band- sometimes called the lumbosacral ligament – runs down and lateral to blend with the ventral sacroiliac ligament
Describe the ligaments and structure of the sacro-coccygeal joint?
structure: sacrum is separated from coccyx by fibrocartilage disc
ligaments:
- ventral sacrococcygeal
- two dorsal sacrococcygeal- one shorter deeper one which unite the adjecnet bones and a superficial one which closes the sacral hiatus
- lateral sacrococcygeal ligaments - run from transverse process of the coccyx each side to the inferolateral angle of the sacrum - completes the foramen for S5
What are the Origins and Insertions and relations and innervation of the piriformis muscle?
Origin: middle pieces from its own half of the sacrum and associated lateral mass, with the origin extending medially between the anterior sacral foramen
Insertion: Apex of the greater trochanter, with some fibres running along the greater trochanter to form a triangular tendon insertion with glut medius and minimus
Relations:
- completely fills greater sciatic foramen
- the sacral nerves and sacral plexus lie on the muscle
- in the buttocks its upper border lies along gluteus medius and lower along superior gemellus
Innervation: anterior rami of S1 and 2
What structure travel above and below the Piriformis in the greater sciatic foramen?
(hints infrapiriform is PIN PINS)
Supra piriform: superior gluteal nerve and vessels
Infrapiriform:
- posterior cutaneous nerve of thigh
- Inferior gluteal artery, vein and nerve
- Nerve to Quadratus femoris
- Pudendal nerve
- Internal pudendal artery and vein
- nerve to obturator internus
- sciatic nerve
Structure of the Obturator canal and its contents?
- is covered by the obturator membrane
- the obturator membrane
- the obturator canal is formed by the thickened superior edge of this ligamnet - attached to the anterior and posteriro obturator tubercles
- the obturator canal contains: obturator artery, obturator vein and obturator nerve as they pass out of the pelvis.
Origins, insertions, path and innervation of the Obturator internus muscle?
- Origin: from the margins of the obturator foramen and obturator membrane. Its insertions however also spread to the pelvic brim posteriorly, the greater sciatic notch and the falciform ridge (falciform insertion of sacrotuberous) of the ischium
- Insertion: greater trochanter and trochanteric fossa - with a tricipital tendon - formed with inferior and superior gemelli
- path: the fan shape of fibres converges at the lesser sciatic notch, and makes a right angled bend around the lesser sciatic notch to the buttocks – may leave a shallow groove
- innervation: nerve to obturator internus
Origins and insertions and innervation of gemellus inferior
- Origin: arises from the ischial tuberosity at the margin of the lesser sciatic notch
- Insertion: tricipital tendon alogn with superior gemellus and obturator internus
- — this tendon lies horizontal in teh buttock - beneath the piriformis and above the quadratis femoris
- innervation: nerve to quadratus femoris
what are the origins, insertions and innervation of the superior gemellus
- Origins: The superior gemellus arise from the ischial spine
- Insertion: tricipital tendon
- Innervations: nerve to obturator internus
What is the structure and contents of the pudendal canal?
- contents: internal pudendal artery and veins and pudendal nerve- which exit into the deep perineal pouch
- it is formed on the medial aspect of the obturator internus -by its covering with the obturator membrane
- located in the lower lateral wall of the ischiorectal fossa.
What are the muscles of the pelvic floor
1) levator ani -each muscle arise in continuity over the spine of the ischium over the “white line” of obturator internus. All insert in the coccyx and anococcygeal ligament
- iliococcygeus
- pubococcygeus
2) Coccygeus
Origins, insertions and innervation of the coccygeus muscle
- origin- the ischial spine, alongside the margin of piriformis
- path lies on top of the sacrotuberous ligament
- insertion: side of coccyx and lower sacrum
- innervation: perineal branches of S4 and 5
Origins and insertions of the levator ani
Origin: in continuity from the ischial spine to the pubis, along the arcus tendineus (the white line on the obturator fascia)
– the iliococcygeus from the posterior half of the arcu tendinus
– pubococygeus from the anterior half of the arcus tendineus and body of pubis
Insertions: side of the coccyx and anococcygeal ligament and raphe
– U shaped loops formed by insertion pattern
Innervation: perineal branches of S3 and 4, which enter the pelvic surface of the muscle
— The inferior rectal branch of the pudendal nerve (S2) supplies the external sphincter and not the levator ani, S4 does not supply the sphincter
What are the functional divisions of the Pubococcygeus muscle?
o Pubococcygeus proper: The bulk of the posterior fibres arising from the white line sweep back on the iliococcygeus in a flat sheet to insert into the coccyx, anococcygeal ligament and raphe
o Puborectalis: Those arising from more anteriorly on the white line and periosteum of the pubis swing medially and join with its other side and the posterior fibres of the deep part of the external anal sphincter in a U shaped sling
o Levator prostatae: More medially fibres pass in a U shaped sling behind the prostate into the peroneal body
In females – this is thepubovaginalis or sphincter vaginae – and inserts in the perineal body
o The most medial fibres are adjacent to the urethra and can exert ureteric action
What are the 2 rules that govern Pelvic fascia?
1) - over non expansile parts it is a strong membrane, over expansile or mobile parts it is a loosely felted areolar tissue
2) the fascia never extends over bare bone (exception is Waldeyer’s fascia
What is Waldeyer’s fascia? and how are spinal nerves and the sacral plexus related to this?
oThe fascia of Waldeyer originates from the hallow of the sacrum and sweeps downwards to attach at the ampulla of the rectum – its breaks the rule of no bony attachments
The spinal nerves lie external to this fascia on the pelvic wall, whereas the sacral plexus lie behind the fascia and in front of the perifomris and its branches do not penetrate the fascia
The superior and inferior gluteal vessels however have to pierces this fascia to reach the buttock
Structure of the rectouterine and rectovesical pouches, and relationships to nearby organs
- created by reflection of peritoneum from the rectum onto the bladder in men and uterus in women
- These pouches are the lowest parts of the peritoneal cavity 7.5cm and 5.5 cm from the anal margin in men and women –– can reach in fingertip exam
They are normally occupied by coils of small intestine or sigmoid colon
• Above the rectovesicle pouch are the upper part of the base of the bladder, and tips of seminal vesicles
o Below – is the rest of the bladder base, seminal vesicles, prostate and end of each ureter and ductus deferens
oThe rectovesical fascia (of Denonvillers) intervenes between this part of the rectum and the structures infront – in early stages of cancer- provides opportunity for spread
•In front of the rectouterine pouch is the uppermost part of vagina (the fornix with the cervix projecting into it) . Below is just the vagina
Arterial Supply to the rectum
1) primary: superior rectal artery (the continuation of the inferior mesenteric)
2) middle rectal - travel in the lateral rectal ligaments
3) inferior rectal artery - penetrate the walls of the anal canal and run upwards
4) The median sacral – makes an unimportant supply to the posterior wall at the anorectal junction – but may cause bleeding in operations