Pelvis Flashcards
differentiate between the abdomen, pelvic cavity and perineum
- abdominal cavity superior until it meets the iliac crests
- then pelvic cavity: greater and lesser pelvis separated by the pelvic brim
- then perineum
What bones form the pelvis?
- hip bones (ischium, ilium, pubis)
- sacrum
- coccyx
What are the joints of the pelvis?
- pubic symphysis (secondary cartilaginous)
- sacroiliac joint (bilateral and posterior - synovial)
- hip joint (ball and socket joint - synovial)
What forms the pelvic inlet?
- pubic symphysis
- pubic crest
- pectineal line
- arcuate line of ilum
- sacral ala and sacral promontory
What are the ligaments of the pelvis?
- sacrotuberous ligament: from posterior-inferior iliac spine, sacram and coccyx to ischial tuberosity
- sacrospinous ligament: from sacrum, cocyx and sacrotuberous ligament to ischial spine
- both form greater and lesser sciatic foramina
What forms the pelvic outlet?
- pubic symphysis
- ischiopubic ramus
- ischial tuberosity
- sacrotuberous ligament
- coccyx
Describe some differences between the male and female pelvis
Females:
- thin and light
- shallow greater pelvis
- wide and shallow lesser pelvis
- inlet is oval and rounded and wide
- outlet is large
- wide pubic arch
Males:
- thick and heavy
- deep greater pelvis
- narrow and deep lesser pelvis
- inlet is heart shaped and narrow
- outlet is small
- narrow pubic arch
What forms the different pelvic walls
Antero-inferior:
- pubic symphysis
- body and rami of pubis
Postero-superior:
- sacrum
- piriformis (divides the greater sciatic foramen)
Lateral:
- obturator internus with fascia
Where is the perineum found?
inferior to the pelvic floor and divided into 2 compartments (superficial and deep) anteriorly by perineal membrane
What muscles form the pelvic diaphragm?
- levator ani (pubococcygeus, puboredctalis, iliococcygeus)
- coccygeus
What are the origins and innervations of the levator ani muscles?
- pubis
- ischial spine
- tendinous arch (formed from thickening of internal membrane of obturator internus)
- innervated by S3-4
Describe the anatomy and role of puborectalis
- originates from one side of pubis, slings round to attach to other side of pubis
- extends muscle fibres medially around anus region
- important in faecal continence
What are the divisions of pubococcygeus?
- puborectalis
- puboperineal
- pubovaginalis (female) or puboprostaticus (male)
What is the functions of the pelvic diaphragm (levator ani)?
- supports pelvic organs
- makes anorectal angle more acute and augments external anal sphincter for faecal continence
- augments urethral sphincter for urinary continence
- forms vaginal sphincter
- actively contracted coughing/sneezing/forced expiration
Where are the pelvic diaphragm muscles anchored?
- all meet in midline to form anococcygeal body (raphe of ligament) and perineal body (central tendon of perineum)
What is the lowest point in the pelvic cavity?
- rectouterine/rectovesical pouch
Describe the prevertebral plexuses
- prevertebral plexuses are formed around abdominal aorta by:
- sympathetics (T1-L2/3)
- parasympathetics (vagus or S2-4)
- condense around origins of branches of abdo aorta to form:
- coeliac plexus
- renal plexus
- superior and inferior mesenteric plexus
- superior hypogastric plexus
Describe the pelvic autonomic nerves
- sacral sympathetic trunks (motor and sensory, 4 pairs sympathetic ganglia, lumbar and sacral splanchnic nerves)
- parasympathetic fibres from S2-4 (nervi erigentes, motor and sensory)
- hypogastric plexuses (superior and inferior hypogastric plexuses)
- periarterial plexuses (postsynaptic, sympathetic, vasomotor fibres to arteries - superior rectal/ovarian/internal iliac)
Where is the superior and inferior hypogastric plexuses found?
- superior: lies in front of inferior part of abdo aorta and its bifurcation
- inferior: lies on each side of rectum, in base of bladder and vagina
What is the superior hypogastric plexus formed as?
- continuation of aortic plexus
- sympathetic fibres from L3 and L4 sympathetic ganglia
- parasympathetic fibres from pelvic splanchnic nerves
What is the inferior hypogastric plexus formed as?
- sympathetic fibres from hypogastric nerves (from superior hyogastric)
- parasympathetics from pelvic splanchnic nerves
Describe what different visceral afferents travel with
- visceral afferents conducting unconscious sensation travel with parasympathetic fibres
- visceral afferents conducting pain travel with: * sympathetics T11-12 (if organ touches peritoneum) - suprapubic pain
- parasympathetics S2-4 (any organ below peritoneum) - perineum pain
Where is the pelvic pain line?
- inferior limit of peritoneum
- middle of sigmoid colon
Where does the pudendal nerve originate and travel?
- originates S2-4
- travels through greater sciatic foramen
- curves posterior to ischial spine and sacro-spinous ligament
- runs forwards into perineum inferior to levator ani
Describe the arterial supply of the pelvis
- common iliac artery => internal iliac artery opposie sacroiliac joint at level T5 disc
- internal iliac divides into anterior and posterior trunks
- supplies buttock, medial thigh, posterior pelvic and abdo walls, pelvic viscera and perineum
Describe the venous drainage of the pelvis
- venous plexuses of pelvic viscera that drain into internal iliac or internal pudendal vein
- internal iliac drains to the artery
- joins external iliac vein to form common iliac vein
Describe the lymphatic drainage of the pelvis
- parallel with venous drainage
- common, external, internal iliac and sacral lymph nodes
- interconnected
