1.2.3 Pelvis Flashcards
Bony features of the pelvic girdle
- Pubic symphysis – articulation of anterior parts of left and right hip bones, a _______________ (limited movement)
- Sacroiliac joints – at the posterior aspect, the sacrum articulates with the hip bones
o Synovial joints but no movement can occur
Parts of the hip bone
- The hip bone is divided into 3 parts, ilium (biggest part), ischium and pubis
o These 3 parts originally develop separately as a foetal but then fuse together postnatal
- Fusion lines of the 3 bones form the acetabulum – _____________ allows for articulation with the head of the femur
secondary cartilaginous joint;
acetabular fossa;
Pelvic cavity – divided into false pelvis and true pelvis by the pelvic brim (red-dotted line)
- Bounded by the pelvic wall – sacrum, coccyx and hip bones
- Pelvic inlet (brim) – _____________
- Pelvic outlet – ___________, ischial tuberosities, ________________ ligaments and coccyx
- Ligaments from sacrum to the pelvic bones – sacrospinous and sacrotuberous
o Sacrospinous ligament (smaller) – attaches to the ____________ and the lateral border of the sacrum and coccyx
o Sacrotuberous ligament – ____________ to the sacrospinous ligament
§ Apex – attached to the _______________
§ Broad base – attached to the ____________ - These ligaments convert the sciatic notches (greater and lesser) into greater and lesser sciatic foramen
- Abdominal cavity and pelvic cavity is in direct continuity as there are no structures separating the 2 cavities
- The axis of the pelvic cavity is angled about 45° back
(anteroinferiorly) from the abdominal cavity
o The pelvic outlet separates the pelvic cavity from the perineum
linea terminalis
ischiopubic rami; sacrotuberous;
ischial spine;
superficial;
ischial tuberosity;
sacrum
Muscles and nerves line the pelvic cavity
o Most of the pelvic bone facing the pelvic cavity is covered by the _____________muscle and its fascia
o The _______________ of nerves (on the medial wall of the pelvic cavity) gives rise to the sciatic nerve and obturator nerve
obturator internus;
lumbosacral plexus;
Muscles of the pelvic walls – innervated by segments L5 to S2
- Piriformis muscle – on the posterior wall of the pelvis
o Originates from the anterior aspect of the sacrum and exits the pelvis through the _________________ to enter into the gluteal region, inserting into the _________________________ - Obturator internus muscle – on the lateral wall of the pelvis
o Originates from the ___________, converting into a tendon which passes through the _____________ to insert into the greater trochanter of the femur - These muscles serve in the lateral rotation of the femur
greater sciatic foramen; greater trochanter of the femur
obturator membrane; lesser sciatic foramen
Pelvic diaphragm – made up of a layer of muscles
- Diamond-shaped area – bounded anteriorly by ____________, laterally by ___________ (anterior) and ______________ ligaments (posterior), posteriorly by coccyx and inferiorly by perineal membrane (anterior half) and perineum
Pelvic floor muscles – taking origin from the pelvic wall and sacrum (innervated by ___________ (segments S2 to S4) and S4 spinal nerves)
- Levator ani – wide thin sheet of muscle with linear origin from the back of the pubic bone, tendinous arch and ischial spine
o Tendinous arch – formed from the thickening of the membrane that covers the obturator internus
o Fibres of the levator ani muscle travel downwards and medially to their insertion
Puborectalis: Muscle fibres run backwards and continues with the similar fibres of the opposite side to form a sling around the junction of rectum and anal canal – ____________ ligament
Pubococcygeus: Muscle fibres run backwards posteriorly and inserts into the anococcygeal ligament/__________________
- Coccygeus muscle – takes origin from the ________________ and inserts into the lateral border of the coccyx and sacrum
pubic symphysis;
Ischiopubic rami; sacrotuberous;
pudendal nerve;
anococcygeal;
raphe Iliococcygeus;
ischial spine
- Levator ani is pierced by various structures (2 in males, 3 in females) in the midline
o From the posterior aspect, there is the anal opening and anterior to the anal opening is the __________and further anterior is the _____________
o These openings make the pelvic diaphragm slightly weaker - The levator ani is slung from the pelvis and sacrum
- Below the ______________ is the perineum containing voluntary sphincters and external genitalia
vaginal opening;
urethral opening;
pelvic diaphragm
Urinary apparatus
- The lower part of the urinary system lies within the pelvic cavity– the urinary bladder sits on the ________________
Male pelvis
- Urinary bladder leads out through the urethra passing through the erectile tissue of the penis to the external urethral orifice
- Prostate gland – at the lower end of the urinary bladder, an accessory organ in the male reproductive system
- Rectum and anal canal are posterior to the urinary bladder
Inferior: Prostate gland, _____________ (with internal urethral sphincter)
Posterior: Rectum, anal canal
Also inferior: ___________, _____________ (fat-filled areas)
pelvic diaphragm muscles;
urogenital diaphragm;
Levator ani; ischioanal fossae
Urethra – 20 cm long and is divided into 4 parts
- Pre-prostaticpart: Before the prostate
gland
- Prostatic part: Passing between the prostate gland (with ________________)
- Membranous part: Crosses the _______________ – shortest part
- Spongy part: Within the erectile tissue (corpus spongiosum)
- The 2 sphincters controlling the urethra in males are internal urethral sphincter (smooth muscle) at the ___________________ and external urethral sphincter (skeletal muscle – voluntary) in the _____________ above the perineal membrane
verumontanum;
perineal membrane;
neck of the urinary bladder;
deep perineal pouch
Female pelvis – main organs are the rectum, uterus and urinary bladder
- Urinary bladder is anterior to the uterus – similar to that in the males but the urethra is much shorter (4 cm)
- Peritoneal pouches in the female pelvis
o Rectouterine pouch* –between rectum and ___________ surface of the uterus
o Vesicouterine pouch – _______ to uterus and on the ___________ aspect of the urinary bladder
- Other structures in the pelvis include the ovary, Fallopian tube, ureters coming from the kidneys (posterior wall of the pelvic cavity)
- In females, the _____________________ is not well developed compared to in males
o The external urethral sphincter is a skeletal muscle surrounding the urethra in the deep perineal pouch
o There are 2 additional groups of muscles in females that help with urinary continence – ______________ and _________________ (both are part of the levator ani)
posterior;
anterior; posterior;
internal urethral sphincter
sphincter urethrovaginalis; compressor urethrae
Urinary bladder – tetrahedral shaped (superior, right and left inferolateral, and posterior sides)
- Made of smooth muscle, each corner of the tetrahedral has a structure arising
Posterior: 2 ureters enter the ____________ of the urinary bladder
Inferior: Origin of the _________
Anterior: _____________
- The urinary bladder assumes the tetrahedral shape when it is empty – balloons up and becomes round when full
- The superior surface of the urinary bladder is covered by peritoneum but not the other sides of the bladder
o When the urinary bladder fills up, it expands between the ______________ and the lining peritoneum - The smooth muscle sphincter (vesicae) is at the neck of the bladder while the skeletal muscle sphincter (urethrae) is found in the perineum
fundus; urethra; Median umbilical ligament;
transversalis fascia;
Rectum and anal canal
Rectum – begins at S3, has a double-S bend, pierces the _____________ to pass into the perineum to become the anal canal
- The rectum descends within the concavity of the sacrum and shows 3 lateral curvatures
- The wall of the rectum is made of smooth muscles while the external sphincters of the rectum that are skeletal muscles
- Guarded by 2 sphincters – external anal sphincter (voluntary) and internal anal sphincter (involuntary)
- The rectum is supplied by the ____________________, corresponding to the various parts of the rectum
- The anal canal is supplied by the ________________
o The superior and middle rectal arteries come from the inferior mesenteric artery from the abdominal aorta
o The inferior rectal artery is a systemic artery which arise from the _______________ from the internal iliac artery
- The rectum becomes the anal canal at the anorectal junction
o The whole of the rectum is supplied by the autonomic nervous system – mainly sensitive to stretching of the rectum
o The anal canal is supplied by the somatic nerves – mainly sensitive to injury (sharp sensations)
External anal sphincter – deep, superficial and subcutaneous groups of muscles which bring continence of the anal canal
- The skeletal muscle sphincter that surrounds the anal canal is less important to faecal continence than the _____________ (part of the levator ani) sling
- Puborectalis sling – forms a sharp angle at the anorectal junction, the main functional sphincter
o When the puborectalis muscle contracts, it keeps the rectum at a sharp bend, preventing faeces form passing through and thus maintaining continence
o If the pelvic diaphragm is damaged e.g. episiotomy – surgical cut in the muscular area between the vagina and anus during childbirth to enlarge the vaginal opening, it can affect the puborectalis and cause faecal incontinence
levator ani;
superior and middle rectal arteries; inferior rectal artery;
internal pudendal artery
puborectalis
Comparison of rectum and anal canal
- embryological origin of rectum is _____, while anal canal is _________
- arterial supply of rectum is ______, while anal canal is ____________
- Rectum has _____ cells; anal canal has ________________
- lymphatic drainage: _____ for rectum and ______ for anal canal
- Nervous supply:
Rectum: Sympathetic – ____________; Parasympathetic – S2 to S4
Anal canal: Somatic nerves – inferior rectal branches of the pudendal nerve (S2 to S4). Pudendal nerve supplies the pelvic diaphragm muscles and is also sensory to the anal canal - Haemorrhoids: Internal – not painful (visceral); External – painful (somatic pain)
endoderm; ectoderm
superior rectal artery; inferior and middle rectal arteries
simple columnar; stratified squamous
internal iliac; superficial inguinal
L1 to L2 (hypogastric plexus)
The main artery of the pelvic structures is the internal iliac artery which is a branch of the common iliac artery
Internal iliac artery – has 2 divisions, anterior and posterior
- Anterior division – gives branches to most of the visceral structures of the pelvic cavity (urinary bladder, uterus and rectum)
o The anterior branch gives vesical arteries
for the bladder, uterine arteries for the uterus and
cervix, and the __________________ for the lower part of the rectum
- Posterior division – supplies most of the gluteal muscles via the _______________________
Posterior division – supplies lower posterior abdominal wall, medial compartment of thigh
- _____________ artery: Body wall
- Lateral sacral artery
- ___________________: Muscles in the gluteal region
Anterior division – supplies pelvic viscera, perineum, gluteal region, medial compartment of thigh
- Superior vesical artery and Inferior vesical artery: Urinary bladder
- Obturator artery: Enters the medial compartment of the thigh to supply muscles
- Middle rectal artery: Part of the rectum
- Uterine artery: Uterus
- Vaginal artery: Vagina
- _________________ artery: Perineal structures
Inferior gluteal artery* Muscles in the gluteal region
- Origin of the inferior gluteal artery is highly variable between the anterior or posterior divisions
middle rectal artery;
superior and inferior gluteal arteries;
Iliolumbar; Superior gluteal artery;
Inferior pudendal
Folds of the rectum
- Anterior-posterior – double ‘S’ shaped bends
o The rectum follows the curvature of the sacrum and coccyx (bending backwards first then forward)
- Lateral – one _________ and _____________ curvatures (formed by the reduplication of the mucous membrane containing submucous tissue and thickening of circular smooth muscle of the rectal wall)
o On the luminal aspect, these three curves are marked by semi-circular folds (Houston’s valves)
right-sided; two left-sided
Rectum, peritoneum and relations
- In the upper third of the rectum, its front and sides are
covered by peritoneum
o In its middle third, only the front is covered by
peritoneum
o Its lower third is devoid of peritoneum
- In males, the peritoneum dips down till the middle third of the rectum, reflecting up and covering the bladder o \_\_\_\_\_\_\_\_\_\_\_\_ (rectoprostatic fascia) – base of the rectovesical pouch - In females, the peritoneum dips down till the middle third of the rectum, reflecting up to cover the uterus and bladder o Rectouterine pouch (\_\_\_\_\_\_\_\_\_\_) – deepest point of the peritoneal cavity when supine and thus a likely site for fluid accumulation
Denoviller’s fascia;
Douglas pouch
