8. Pelvis and Pelvic Contents Flashcards
What makes up the BONY PELVIS?
HIp (coxal) bones, sacrum, coccyx
What makes up the hip bone?
ilium
ischium
Pubis
These bone fuse in late adolescence
What forms the SUPERIOR PELVIC APERTURE?? (pelvic brim, inlet)
The superior pelvic aperture (pelvic brim, inlet) is a line formed by the sacral promontory, arcuate line of the ilium and pectin pubis of the pubic bone. It divides the pelvis into the greater pelvis (pelvis major, false pelvis) above and the lesser pelvis (pelvis minor, true pelvis) below.
The true pelvis contains the pelvic contents
What forms the inferior pelvic aperture? (pelvic OUTLET)
The inferior perlvic aperture (pelvic outlet) runs from the inferior part of the pubic symphysis –> ischiopubic ramus —> sacrotuberous ligament –> tip of coccyx. The shape of inlet and outlet is important in childbirth.
*Note unlike between thoracic and abdominal cavities (diaphragm) there is no physical division between abdominal cavity and pelvic cavity
Name the Joints of the pelvis:
Pubic Symphysis: secondary cartilaginous joint (symphysis) with hyaline cartilage on the symphyseal surface and united by fibrocartilage.
Sacroiliac joints: synovial plane joints with a fibrous posterior component.
The ligaments of the SI joints are very strong and allow only limited movement of the pelvic joints. :
- Iliolumbar
- Anterior sacroiliac
- Posterior Sacroiliac
- Sacrospinous
- Sacrotuberous
- Interosseous
What is the ORIENTATION of the BONY PELVIS
When standing the ASIS and pubic tubercles are in coronal plane,
the superior symphysis pubis and coccyx are in horizontal plane
Planes of pelvic inlet about 60 degrees, outlet about 10 degrees above horizontal.
Female Vs. Male Pelvis
The female compared to male pelvis (on average) has wider superior and inferior pelvic apertures, wider pubic arch, wider greater sciatic notch, narrower depth of true pelvis and thinner, lighter bones. A female can sometimes have more ‘male’ like pelvis, and for this reason may need a caesarean.
Measurements may be made of the pelvis:
Superior pelvic aperture:
- Conjugate (anteroposterior) and transverse
Inferior perlvic aperture:
- Anteroposterior and Transverse
The True Conjugate (superior pubic symphysis to sacral promontory)
The True Conjugate (superior pubic symphysis to sacral promontory) can only be measured on radiographic films.
Normal measurement is 11cm or more.
The diagonal conjugate (inferior pubic symphysis to sacral promontory)
The diagonal conjugate (inferior pubic symphysis to sacral promontory) can be estimated using an internal examination; it is normally 11.5cm or more.
The Obstetric conjugate
The obstetric conjugate is the shortest of the three measurement (sacral promontory to the thickest part of the pubic symphysis) and measures 10cm or more. The inlet is said to be contracted when diameters are smaller than normal
The PELVIC VISCERA:
Male Main contents
Male Main Contents:
- Bladder
- Prostate
- Genital ducts- ductus deferens,
- seminal glands
- rectum
The PELVIC VISCERA:
Female Main contents
Female Main Contents:
- Bladder
- Vagina
- Uterus
- Uterine tubes
- Overies
- Rectum`
THe pelvic viscera and PERITONEUM
The pelvic viscera sit below the peritoneum, so they may be partially covered by peritoneum.
Peritoneum covers the upper parts of rectum (anterolaterally), the superior surface of bladder, most of the uterus, uterine tube and ovary.
POUCHES
The reflection of the peritoneum over the bladder, uterus and rectum creates a number of pouches or recesses.
Males have one pouch; rectovesical.
Females have two pouches: vesicouterine and rectouterine (of Douglas).
*Clinical note: these pouches are the most inferior parts of the peritoneal cavity, fluid etc can accumulate here.
Overview of blood vessels in the pelvis
Internal Iliac ::: pelvic viscera, pelvic wall, perineum and gluteal region
Inferior Mesenteric –> Superior rectal
Aorta –> ovarian artery
Bifurcation of aorta —> median sacral arteries
The RECTUM
Rectum = straight but in fact it is a curved structure.
Function: stores faeces
Starts at the rectosigmoid junction (S3) ends at the rectoanal junction (at level of pelvic diaphragm). It has no haustra, tenaiae coli (complete layer of longitudinal muscle instead), or mesentary.
Characterised by transverse rectal folds which act like valves (better seen on sigmoidoscopy)
Perianal flexure
The perianal (anorectal) flexure is the junction between the anal canal and rectum. It is created by the puborectalis muscle (a pelvic floor muscle)- contributes to incontinence
Anterior relations of the rectum! in the MALE
in the MALE: - SI, - Sigmoid colon - Rectovesical pouch - Genital ducts - Prostate - Bladder Note the proximity of the prostate to rectum for rectal exam of prostate or rectal ultrasound
Anterior relations of the rectum! in the FEMALE
in the FEMALE:
- Sigmoid colon
- Small Intestine
- Rectouterine pouch
- Uterus
- Rectovaginal septum
- Posterior wall of the vagina
BLOOD supply to the rectum
Inferior mesenteric a —-> superior rectal a (supplies most of the rectum)
Internal iliac a —> middle rectal artery
Internal iliac a –> internal pudenal a —> inferior rectal artery(supplies the anal canal)
Venous Drainage of the rectum:
Drainage is mostlyby:
superior rectal vein —> inferior mesenteric vein —-> splenic v (or sup mesenteric v) —> hepatic portal vein.
Middle rectal vein —> internal iliac vein
Inferior rectal vein —> internal pudenal vein —> internal iliac vein .
** important: the internal (above pectinate line) and external rectal venous plexuses (below pectinate line) are sites of anastomoses between the superior, middle and inferior rectal veins (portal- caval anastomosis).
Although haemorrhoids can be caused by portal hypertension they also haev other common causes such as pregnancy, old age, chronic constipation, genetic and anal intercourse
Innervation of the pelvis
Sympathetic: T12- L2 mostly via lumbar splanchnics to pelvic plexus
Parasympathetic: S2-S4 pelvic splanchnics to pelvic plexus.
PAIN travels via P-S nerves
Lymphatic Drainage of the palvis
Follows the arteries;
along the superior rectal and inferior mesenteric aa. —> inferior mesenteric nodes.
Along middle rectal aa –> internal iliac nodes
anal canal –> internal iliac nodes and superficial inguinal nodes
The URINARY BLADDER
Detrusor muscle (smooth muscle), lined by transitional epithelium. The posterior surface (the base) contains the trigone, a triangle formed by the two ureters entering the bladder superiorly and one urethra exiting inferiorly.
The trigone is less expansible than the rest of the bladder so as not to damage these structures
The apex is anterior and is attached to the median umbilical ligament. The neck is inferior and leads to the urethra. It also has a superior surface and two inferolateral surfaces
Innervation of the urinary bladder
Innervation:
Sympathetic: T12- L2/L3 mostly via lumbar splanchnics to pelvic plexus.
PS: S2-S4 pelvic splanchnics to pelvic plexus
Pain: from inferior bladder travels via PS nerve, superior bladder via sympathetic nerves
Bladder relations:
Superior: peritoneal cavity, veicouterine pouch and uterus, small intestine, sigmoid colon
Inferior: prostate/pelvic and urogenital diaphragms
Posterior: rectovesical pouch, genital ducts, rectum/ cervix of uterus, vagina
Anterior: Pubic bones, rectus abdominus
Lateral: hip bone, pelvic wall
The Ureters!!
Are RETROPERITONEAL, descending into the pelvis near the bifurcation of common iliac vessels, the ureters travel through the bladder wall obliquely therefore the detrusor muscle acts like a sphincter preventing backflow up the ureter.
In the male the ureter enters the base of bladder posterolaterally between ductus deferens and seminal vesicle. In the female the ureter travels 1-2cm lateral to cervix of uterus before entering the superolateral aspect of the bladder, note the uterine vessels (ligated during a hysterectomy) cross superior to the ureter.
The URETHRA
The urethra commences at the internal urethral orifice (part of the trigone) and ends at the external urethral orifice.
The female urethra is located anterior to the vagina, 4cm long (short). It contains an external (skeletal) urethral sphincter in the pelvic diaphragm/urogenital triangle but no real internal sphincter.
The smooth muscle around the neck of the bladder is distinct from the DETRUSOR muscle as the fibres have an oblique arrangement running into the wall of the ureter, this helps maintain continence but is not a true sphincter.
The male urethra is much longer than the female urethra and has 4 parts
- Intramural (preprostatic)
- Prostatic
- Membranous
- Spongy
It has an internal urethral sphincter (smooth muscle) at the neck of the bladder and an external (voluntary) sphincter in the membranous urethra. The internal sphincter has rich sympathetic supply and it constricts during ejaculation to prevent backflow of semen into the bladder, it is not known if this sphincter is also involved in teh control of micturition. In both sexes the external sphincter allows control of micturition.
The PROSTATE
a Walnut sized gland below the bladder, it has a fibrous capsule closely adherent to the prostatic nervous plexus and venous plexus. The apex is located inferiorly, adn the base superiorly!!
It is divided into lobes (however there is considerable variation between texts also different clinical subdivisions).
A simple subdivision has an anterior lobe (isthmus) which is the fibromuscular section of the gland. The glandular portion is divided into two lateral lobes, which can be divided further.
Directly posterior to the urethra is the middle lobe (prone to benign prostatic hypertrophy). The posterio and lateral portions of the gland are most prone to cancer- note value of digital rectal exam of prostate.
The lumen of the posterior wall of the urethra contains an elevation (urethral crest), in the prostatic urehtra this is enlarged (seminal colliculus). Either side of the seminal colliculus is a groove (prostatic sinus).
A small central depression in the seminal colliculus is called the utricle (a remnant of the embryonic uterovaginal canal). Multiple ducts from the prostate drain into the prostatic sinus. Ejaculatory ducts drain into the seminal colliculus just below the utricle.
Blood vessels of the bladder and prostate
Males: internal iliac artery —> superior and inferior vesical arteries
Females: internal iliac artery —>superior vesicle and vaginal arteries
Vesical venous plexus drains to the internal iliac veins but also anasomoses with veins of the bony pelvis and to internal vertebral plexuses
Lymphatics of bladder and prostate
Lymphatics drain to the external and internal iliac nodes. Prostatic cancer often spreads via venous system (lumbar vertebrae) as well as lymphatics
Innervation of the bladder and pelvis
Sympathetic: T12- L2/3
Parasympathetic: S2-S3 pelvic splanchnics to pelvic plexus
Pain via PS and symp (probably)
MALE GENITAL DUCTS:
Ductus deferens = the extraperitoneal course through the pelvis from the deep inguinal ring to the posterior prostate. The terminal part of the ductus deferens is dilated = ampulla.
The ductus deferens joins with the seminal glands to form the ejaculatory duct, which travels almost vertically through the prostate and enters the prostatic urethra then into the membranous urethra
Female Reproductive Organs:
The UTERUS
The inferior part of the uterus is the cervix, above the cervix is the body of the uterus (the fundus is the most superior part of the body). the opening from the vagina into the cervix is the external uterine os (opening) between the superior cervix and the body of the uterus is the internal uterine os.
The wall of the UTERUS (emale reprodductive organ)
The wall of the uterus has several layers;
- Endometrium (inner layer- mostly shed during menstruation),
- Myometrium (muscle)
- Perimetrium (a serosa formed from the peritoneum).
The mesentery of uterus (mesometrium) consists of part of the broad lig (not including the ovarian lig and mesosalpinx).
Explain the orientation of the uterus
Anteflexion- body of the uterus is bent slightly forward relative to the cervix.
Anteversion- cervix is bent forward relative to the vagina
* However the position of uterus is variable depending on the fullness of bladder and rectum (during or after pregnancy). Abnormal positions: retroversion, retroflexion, excessive anteflexion etc.
The CERVIX
The cervix is a firm cyylindrical relatively narrow structure 2.5cm in length, palpable on rectal examinaton. It can be divided into the supravaginal part above the vagina and the vaginal part which protrudes into the top of the vagina creating a narrow slit like recess between the cervix and the superior vagina- the fornix. External os, internal os (openings)
Innervation of the UTERUS
Symp: T12-L2 mainly lumbar splanchnics to pelvic plexus to uterovaginal plexus
PS: S2-4 pelvic splanchnics to pelvic plexus to uterovaginal plexus to cervix (probably)
Pain: from cervix travels via PS nerves, fundus and body via symp
VAGINA
Anterior wall is related to bladder and urethra, postrior wall related to rectum and rectouterine pouch. Anteiror, posterior, lateral fornices of vagina partially encircle the cervix. Note the peritoneal cavity can be accessed via the vagina then across the thin wall of the posterior fornix into the rectouterine pouch.
OVARIES
Paired almond shaped and sized in the elderly- smaller and with a pitted surface from multiple ovulations
Ligaments of female reproductive organs
Suspensory ligament of ovary- contains ovarian aa, vv, nn, ll. Ovarian ligament proper- attaches ovary to the uterus. The Broad Ligament is a double layer of peritoneum that extends from the uterus to lateral wall of the pelvis: parts include the
MESOMETRIUM: mesentary of the uterus
MESOVARIUM: Mesentary of the ovary
MESOSALPINX: Mesentary of the uterine tube.
The round ligament of the uterus is located in the broad ligament and travels to the deep inguinal ring, through inguinal canal to the labia majora
Innervation of ovaries
Symp: T11- L2 mostly via lumbar splanchnics to pelvic plexus to ovarian plexus
PS: S4 pelvic splanchnics to pelvic plexus to ovarian plexus
Pain: via symp
UTERINE (fallopian) tube parts
4 parts:
- Intramural
- Isthmus
- Ampulla
- Infundibullum
- Fimbriae
Blood supply of the UTERUS, UTERINE TUBE, VAGINA, OVARY
internal iliac artery ----> uterine & vaginal arteries Abdominal aorta (L2) ---> ovarian arteries
Venous plexus —> uterine veins —> internal iliac vein
Ovarian veins —> IVC —> left renal vein
Lymphatics
body of uterus, cervix, vagina—-> internal and external iliac nodes —->
Part of fundus along round ligament through inguinal canal —–> superficial inguinal nodes
Superolateral uterus, uterine tube, ovary along suspensory ligament of ovary —> lumbar nodes
Lower vagina —> superficial inguinal nodes (ie uterine carcinoma can spread via lymphatics via a number of possible lymphatic channels)
