Lecture 21: Anatomy of the pelvis, perineum and female reproductive organs Flashcards
What are the innominate bones? What do they form?
Ilium, pubis and ischium
Form hip bone (os coaxae)
What are the right and left hip bones connected to?
Os sacrum
What bones form the pelvic girdle?
Os sacrum
Both hip bones
What is the acetabulum formed by? articulation?
The 3 innominate bones
Articulates with femur
What is the sacrum formed by?
Fusion of 5 sacral vertebrae
What is the coccyx formed by?
Fusion of 3 to 4 rudimentary vertebrae
What separates the greater pelvis from the lesser pelvis?
Pelvic brim
When does the ossification of the 3 hip bones occur?
At birth, these three components are separated by hyaline cartilage.
They join each other in a Y-shaped portion of cartilage in the acetabulum.
By the end of puberty the three regions will have fused together, and by the age of 25 they will have ossified
What are the joints of the pelvic girdle?
Sacroiliac joints
Pubic symphysis
Sacroiliac joint (*) - joint type, support
Synovial joints (have joint cavity and capsule)
Supported by strong ligaments
Function of sacroiliac joints
Transfer most of the body weight to the hip bones
Allow only limited movements (lateral direction)
What is the shape of the articulating surface of the ilium?
Auricle (ear shaped)
Pubic symphysis- joint type, strengthened by
cartilaginous joint
Interpubic disc
Strengthened by superior and inferior pubic ligaments
What are the differences between the female and male pelvis?
See figure
What does the sacrotuberous ligament connect to?
Connects posterolateral border of sacrum with ischial tuberosity
What does Sacrospinous ligament attach to?
Connects anterolateral border of sacrum with ischial spine
What are the major pelvic foramina?
Greater sciatic foramen
Lesser sciatic foramen
Obturator foramen
See figure
Where is the greater sciatic foramen?
*
Between the greater sciatic notch, the sacrospinous and the sacrotuberous ligament
Where is the lesser sciatic foramen?
+
Between the lesser sciatic notch and both ligaments
Where is the obturator foramen?
Surrounded by the rami of the pubic and ischial bone and closed by the obturator membrane
What is the function of the major pelvic foramina?
Provide exit pathways for vessels and nerves from the pelvic cavity to the gluteal region and the thigh
Where is the rectouterine pouch?
aka pouch of douglas
Most caudal part of the abdominopelvic cavity in women (behind uterus)
See figure
Why is the pouch of douglas clinically important?
Fluid from the abdominal organs can collect here = Can cause pelvic pain
Can sample fluid via the vagina to identify cause of pelvic pain
Can get uterine pregnancies in this space, can ultrasound the area
Where is the vesicouterine pouch?
located anterior to the uterus in women
See figure
Where is the rectovesical pouch?
Most caudal part of the abdominal cavity in men
See figure
What is the floor of the abdominopelvic cavity?
Funnel-shaped pelvic diaphragm
Musculofascial inferior closure of the abdominopelvic cavity and supports the position of the viscera
What muscles make up the pelvic floor?
Levator ani muscle and coccygeus muscle and their fascias
See figure
What muscles make up the levator ani?
Illiococcygeus muscle
Pubococcygeus muscle
Puborectalis muscle
Role of the pelvic diaphragm
supports the position of the viscera
Maintains fecal and urinary continence through tonic contraction
Relaxes during urination and defecation
Actively contracts during activities causing increased intra-abdominal pressure (coughing, sneezing, lifting heavy objects)
What is the levator hiatus?
aka urogenital hiatus
Anterior gap in the levator ani muscle
Allows passage of urethra, vagina and rectum
See figure
Female reproductive organs
Uterus
Fallopian tubes
Ovary
Vagina
See figure
What are the three layers of the uterus?
Myometrium - thick muscle layer
Endometrium - inner layer
Parametrium - surrounding connective tissue (perimetrium: peritoneal lining of fundus and corpus)
What part of the fallopian tubes have the fimbriae?
The Infundibulum
Clinical significance of endometrium
Highly dynamic under the influence of sex steroid hormones
Endometrial cancer
Endometriosis
Parts of the uterus
Fundus - rounded superior part of body above oviducts, lies superior to bladder
Body - mobile part extending from cervix to fundus
Cervix - communicates with vagina (external os) and with the uterine lumen (internal os)
Parts of the uterine tubes
Infundibulum - fimbriated highly motile end that opens into the abdominal cavity; fimbriae move toward ovulating surface of ovary
Ampulla - widest and longest part
Isthmus - thick-walled art of fallopian tube that enters the uterus
Uterine part - traverses the uterine wall and opens into the uterine cavity
Clinical significance of ampulla of uterine tubes
Common location of extrauterine pregnancies
What connects the ovary to the uterus?
Ovarian ligament
See figure
What artery supplies the ovary?
Ovarian artery
Derived from the abdominal aorta
Reaches ovary through suspensory ligament of ovary (infundibulopelvic ligament)
What do the ovarian veins drain into?
Right ovarian vein drains into inferior vena cava
Left ovarian vein drains into left renal vein
How is the ovary attached to the broad ligament?
Via the mesovarium
Why do the ovaries stop higher in the abdominopelvic cavity than testis do during development?
Lack of testosterone stops ovaries from descending further
Orientation of fallopian tubes
Always reaching posteriorly
What is the broad ligament?
Peritoneal fold reaching from the lateral pelvic wall to the uterus.
Contains the uterine artery and vein and autonomous nerves.
What are the mesovarium and mesosalpinx?
Parts of the broad ligament reaching to ovary and uterine tube.
What is the suspensory ligament of the ovary?
Carries ovarian blood and lymph vessels connecting the ovary to the retroperitoneal abdominal space.
What is the function of the ovarian ligament?
is a caudal connection to the uterus.
Round ligament - where is courses, what it connects
Courses within the broad ligament
Connects the fundus of the uterus through the inguinal canal to the labia majora.
Cardinal ligament - location? Connection? Function?
Mackenrodt ligament
Below peritoneal lining
Connects uterine cervix to lateral pelvic wall
Stabilizes position of the uterus
Examination of the uterus
Angle of anteflexion (*)
Angle of anteversion (@)
Fundus points toward anterior wall
See figure
What does the vagina form around the cervix?
Two lateral fornices
What is the posterior fornix related to?
Rectouterine pouch (doulas pouch)
Functions of the fallopian tubes
Pick-up of ovulated oocytes
(infundibulum)
Transport of the maturating oocyte (infundibulum and ampulla)
Nourishment of oocyte and blastocyst (ampulla)
Sperm reservoir (isthmus)
Functions of the vagina
Forms the inferior part of the birth canal
Receives penis and ejaculate during sexual intercourse.
Functions of the ovary
Secretion of the steroid hormones
estrogen and progesterone
Production of ova
(ovarian follicles)
Functions of the uterus
Harbouring and nourishing the embryo/fetus (endometrium and myometrium)
What are the major branches of the internal iliac artery?
Parietal branches: supply pelvic wall and gluteal region
Visceral branches: supply pelvic viscera
What are the parietal branches of the internal iliac artery and what do they supply?
Iliolumbar a. – supplies iliacus, psoas and quadratus lumborum muscle
Lateral sacral a. – branches enter pelvic sacral foramina
Superior gluteal a. – runs between Lumbosacral trunk and 1. sacral nerve above the piriformis muscle, supplies gluteus medius and minimus muscle and tensor fasciae lata muscle
Obturator a. – leaves through obturator foramen; supplies obturator muscles
Internal pudendal a. – supplies perineum (skin, muscles, erectile tissues)
Inferior gluteal a. – separates 1. from 2. sacral nerve, leaves greater sciatic foramen inferior to piriformis
supplies gluteus maximus, hamstrings, quadratus femoris.
What are the visceral branches of the internal iliac artery and what do they supply?
Umbilical a. – distal part obliterated, gives rise to superior vesical artries to bladder
Superior and inferior vesical a. – supplies bladder and ureter, seminal vesicle and prostate (in men)
Middle rectal a. – supplies inferior rectum and seminal vesicles
Uterine a. – may arise from umbilical or directly from internal iliac artery
See figure
Anastomoses between uterine artery and ovarian artery
The ovarian branch of the uterine artery anastomoses with the ovarian artery which brings the main blood supply to the ovary
What does the uterine artery travel in?
Base of broad ligament
Where is the perineum? What does it contain?
Diamond-shaped area beneath the pelvic floor
Harbours external genitalia
See figure
Why is the uterine artery a corkscrew shape?
So that it can stretch in pregnancy
What provides support in the area of the urogenital triangle?
Perineal membrane and associated muscular and fibrous structures
Provides support in the area of the urogenital triangle
See figure
Distance between perineal structures in women
External urethral meatus, vaginal orifice and anus are in close proximity
External genitalia of women vs men
Women: bulb of vestibule, crus of clitoris and greater vestibular (Bartholin’s) glands
Men: bulb of penis, crus of penis and bulbourethral (cowper’s) glands
See figure
What are the muscles of the perineum? Innervation?
Deep transverse perineal muscle (covered by perineal membrane)
Superficial transverse perineal muscle (inconsistent)
Bulbospongiosus muscle: covers the bulb of penis / vestibule
Ischiocavernosus muscle: covers crus penis / clitoris
External anal sphincter muscles
Innervated by pudendal nerve
See figure
Course of the pudendal nerve
Exits pelvic through greater sciatic foramen
Winds around the ischial spine and sacrospinous ligament
Enters pelvis again through the lesser sciatic foramen
Reaches perineum below the pelvic diaphragm muscles
See figure
What does the pudendal nerve innervate?
Somatic motor nerve of the perineum
Sensory supply for perineal skin (including posterior scrotum)
Motor to the external anal sphincter (inferior rectal nerve) and external urethral sphincter
Cutaneous innervation of perineal skin (pain)
Location of pudendal nerve in women
Winds around ischial spine
See figure
What is a pudendal nerve block?
Anaesthetic administered near ischial spine
What is a pudendal nerve block effective for?
Anaesthesia effective for perineal skin and lower part of vagina
Reduces perineal pain associated with the second stage of labour or with
episiotomy or the repair thereof
Not effective for cervix and upper part of vagina
What does the mother feel during pudendal nerve block?
Mother is aware of uterine contractions and associated pain
When is re-administration of pudendal nerve block a problem?
Re-administration is problematic during prolonged birth phase
Does pudendal nerve block eliminate all perineal pain?
No
See figure
Where is the lymphatic drainage of the pelvic organs
Pelvic organs: uterus, cervix, upper vagina, fallopian tubes
Internal iliac lymph nodes
External iliac lymph nodes
Where is the lymphatic drainage of the ovaries and testis?
Para-aortic lymph nodes
Where is the lymphatic drainage of the perineum?
Organs of perineum: labia major, vulva (scrotum), anus interior to pectinate line
Superficial inguinal nodes
What is the function of the rectum?
Storage and controlled release of feces
Where is the rectum located in reference to large intestine?
Distal end of large intestine
Where is the rectal ampulla? What does it transition into?
Rectal ampulla is above pelvic floor
Rectal ampulla transitions into anal canal
Arterial supply of rectum
Upper 2/3: inferior mesenteric artery
Superior rectal artery (from inferior mesenteric artery)
Left middle rectal artery (from left internal iliac artery)
Left internal pudendal artery
Left inferior rectal artery
See figure
Venous drainage of the rectum
Inferior mesenteric vein
Superior rectal vein
Left common iliac vein
Left middle rectal vein
Left internal pudendal vein
Left inferior rectal vein
Venous drainage goes to portal vein and to inferior vena cava
See figure
Anastomoses in anal region
Porto-caval venous anastomoses
What may form in portal hypertension?
Anal hemrroids
What are the anal sphincter muscles? Type of muscle?
Internal anal sphincter (smooth muscle)
External anal sphincter (striated muscle)
See figure
Control of internal and external anal sphincters
Internal: sympathetic control and normally permanently contracted to close the anal canal.
External: voluntary closure of the anus; innervated by pudendal nerve.
What is the ischioanal fossa?
Space beneath pelvic diaphragm
What pathological conditions are common to the ischioanal fossa?
Anal fissures and fistulas: extremely painful (inferior rectal nerves), can cause partial focal incontinence
Peri-anal accesses (wounds, chron’s): may be drained through the skin, can spread to other side (horseshoe-type), may spread into pelvis
