Pelvis Flashcards
the bony pelvis
- the pelvic girdle is the bony structure at the base of the spine which joins lower limbs to axial skeleton
- pelvic cavity bounded by bony pelvis and is an extension of the abdominal cavity
- due to orientation of pelvis, cavity projects backwards (almost at a right angle to abdominal cavity)
what divides the pelvic cavity
pelvic brim (linea terminalis)
greater (false) cavity
- region above pelvic brim
- forms lower part of abdominal cavity
- greater cavity is larger and sits superior to lesser cavity
lesser (true) cavity
- below pelvic brim
- contains pelvic inlet (pelvic brim) and pelvic outlet that is largely closed by the pelvic floor
what is the difference between the pelvic cavity in females and males
pelvic cavity in females forms the birth canal therefore it is wider and more shallow with a larger inlet and outlet than males
- subpubic angle in females >90-100 degrees
- subpubic angle in males 70 degrees
sacroiliac joint
between sacrum and ilium
pubic symphysis
joining right and left pubic bones
the pelvic floor
wide but thin muscular layer that supports the pelvic viscera and forms the inferior border of the abdominopelvic cavity
levator ani
broad muscle group situated on either side of pelvis, main pelvic floor muscle
coccygeus
- muscle that makes up posterior portion of pelvic floor
urogenital hiatus
- U-shaped opening for urethra and vagina
anal aperture
- passage for anal canal
the puborectal sling
- some fibres of levator ani form sling around the rectum
- attaches to pubic bone and wraps posteriorly around rectum forming anorectal flexure
- contraction of puborectal sling keeps rectum closed until defecation
- relaxation allows anorectal flexure to straighten during defecation
- puborectal sling can be damaged during vaginal delivery and can even be torn off from pubic insertion
pelvic peritoneum
forms roof over pelvic cavity – is continuous with parietal peritoneum of abdomen
pouches formed by pelvic peritoneum in females
vesicouterine pouch and rectouterine pouch
vesicouterine pouch
- descends from back of anterior abdominal wall onto upper surface of urinary bladder and then onto anterior surface of uterus
rectouterine pouch
continues over fundus of uterus, down its posterior wall to upper part of posterior vagina, up anterior surface of rectum
pouch formed by pelvic peritoneum in males
rectovesical pouch
rectovesical pouch
descends from back of anterior abdominal wall to superior surface of urinary bladder, passes down posterior surface of bladder and upper ends of seminal vesicles, passes anterior surface of rectum
urinary systems in the pelvis
- ureters descend into pelvic cavity and cross over common iliac arteries (site where renal stones lodge)
- pelvic ureters continue along lateral pelvic wall to enter urinary bladder posteriorly
- in males, site where ureters drain into bladder, vas deferens crosses ureter anteriorly
- in females, each ureter is crossed by uterine artery
sigmoid colon
forms S-shaped loop of variable length, lies under pelvic cavity, ending at middle of sacrum (S3) where it is continuous with the rectum
rectum
follows curvature of sacrum (sacral flexure) before turning posteriorly at anorectal flexure to end at anal canal
venous drainage of sigmoid colon and rectum
inferior mesenteric vein
vas deferens
- one of many structures found in inguinal canal
- within spermatic cord
- along with neurovascular structures
testicular artery
branch off abdominal aorta
artery to vas deferens
branch off the internal iliac artery
pampiniform plexus (of testicular veins)
network of veins that drains venous blood from testis into testicular vein
cremasteric artery
supplies the fascial coverings and muscle of the spermatic cord
ovarian arteries
- lateral paired arteries that supply the gonads
- lateral branches of abdominal aorta at level of L1
- supply ovaries and distal uterine tubes
uterine arteries
- branches of internal iliac arteries
- uterine arteries cross over ureters
- uterine arteries anastomose with ovarian artery
- vagina supplied by vaginal branches of both uterine and internal iliac arteries
- uterine arteries supply proximal uterine tubes
perineum
- part of pelvic cavity inferior to pelvic floor
- contains structures that support the urogenital and GI systems
- diamond shaped area bounded by the pubic symphysis anteriorly, ischial tuberosities laterally and coccyx posteriorly
- divided by imaginary line joining ischial tuberosities into the anal triangle posteriorly and urogenital triangle anteriorly
perineal membrane
- layer of deep fascia that contributes to stability of anterior part of pelvic floor as well as attachment for external genitalia
- divides urogenital triangle into superficial and deep pouch
- passing through perineal membrane is urethra in males and urethra and vagina in females
perineal body
attached to posterior border of perineal membrane
superficial perineal pouch
- lies superficial to perineal membrane
- contains muscle, skin, external genitalia
deep perineal pouch
- contains urogenital diaphragm, a layer of skeletal muscle composed of the external urethral sphincter and deep transverse perineal muscles
perineal body
- fibromuscular mass at center of perineum which provides attachment for muscles of perineum
- helps strengthen pelvic floor
- larger in females
ischiorectal fossa
- wedge-shaped triangular space between ischium and anal canal
- each fossa is a fat-filled space which allows for expansion of anal canal during defecation
pudendal canal
- pudendal canal on lateral wall of each ischiorectal fossa
- formed into the obturator fascia and contains the pudendal nerve and internal pudendal vessels
anal glands
located in ischiorectal fossa drain into anal canal
muscles of penis
- penis composed of 3 cylinders of erectile tissue: corpus spongiosum and corpus cavernosum
- at root of penis, 2 crura of penis are covered by ischiocavernosus muscles, bulb covered by bulbospongiosus muscles
- these voluntary skeletal muscles compress the crura and bulb during erection
- bulbospongiosus muscles compress urethra during urination and ejaculation
prepuce/foreskin
thin, loose skin that covers the glans
clitoris
- consists mainly of erectile tissues and is attached to perineal membrane by 2 crura and 2 vestibular glands
body of clitoris
right and left crus of clitoris (attached to perineal membrane) unite anteriorly to form body
glans clitoris
- located on distal portion of its body
- on each side of vaginal orifice (anchored to perineal membrane) are the vestibular bulbs which unite anteriorly to form glans clitoris
vulva/pudendum
female external genitalia
mons pubis
rounded mass of fatty tissue formed by union of labia majora
female prepuce
anterior and superior to clitoris, prepuce formed from fusion of labia minora
frenulum
anterior and inferior to clitoris, fusion of labia minora forms one frenulum
greater vestibular glands
- lie posterior to bulbs of vestibule on each side of vaginal orifice
- during sexual arousal, produce mucus carried by ducts that open at posterolateral margins of vaginal orifice
- homologous to bulbourethral glands in males
muscles of the clitoris
- structures of root of clitoris covered by perineal muscles
- 2 ischiocavernosus muscles cover crura of clitoris and 2 bulbospongiosus muscles cover bulbs of vestibules and greater vestibular glands
- these muscles compress crura of clitoris and bulbs of vestibule during erection of clitoris
umbilical artery
- transports deoxygenated blood from fetus to placenta
- after birth, proximal branches become superior vesical artery that supplies upper part of bladder
inferior vesicle artery
supplies bladder, ureters, seminal vesicles, prostate, ductus deferens
internal pudendal artery
- exits through greater sciatic foramen and enters lesser sciatic foramen to perineum through pudendal canal
- supplies skin and muscles of anal triangle, urogenital triangle associated erectile bodies
what is the main branch of the sacral plexus to the perineum
pudendal nerve (S2-4)
describe the pathway of the pudendal nerve
leaves pelvis through greater sciatic foramen, crossing ischial spine, enters perineum through lesser sciatic foramen
perineal nerve
important branch of pudendal nerve
- runs through deep perineal pouch into superficial pouch to supply sensory and motor innervation to urogenital region including external urethral sphincter
