Pelvic Floor, Pelvic Organs and Perineum Flashcards
Where is the Pelvic Cavity located?
- Lies below the level of the pelvic inlet at the pelvic brim
- Bounded inferiorly by the pelvic diaphragm/floor
- Located inferoposteriorly to the abdomen and it is continuous with the abdominal
Where is the false pelvis located?
Above the pelvic brim
Where is the true pelvis located?
Below the pelvic brim
Where is the perineum located?
• Located inferior and superficial to the pelvic diaphragm and is outside the true pelvis
What is Sexual Dimorphism in the Pelvis?
- Sexual dimorphism is a result of the adaption for childbirth in the female
- The heavier build and larger muscles in male’s results in more robust bony markings
Why are the Pelvic Diameters measured?
• Clinically the diameters of the lesser pelvis are measured to determine the capacity of the pelvis for childbirth
Sexual Dimorphism in the Pelvis: Comparison between Males and Females
o The pelvic inlet is oval in female and heart shaped in male
o The female pubic arch/subpubic angle is larger and wider
o The greater sciatic notch is wider in females
o The obturator foramen is oval or triangular in females and round in males
What is the Greater Sciatic Notch?
• Greater Sciatic Foramen without the ligaments
What are the Diameters of the Pelvis?
- AP Diameter (Anterior/Posterior)
- Oblique Diameter (Diagonal)
- Transverse Diameter (Horizontal)
Measurements of the AP Diameter (Anterior/Posterior)
o Brim is shortest in this diameter o Outlet of the pelvis is wider o Cavity is 12 cm o Brim is 11 cm o Outlet is 13 cm
Measurements of the Oblique Diameter (Diagonal)
o Cavity is 12 cm
o Brim is 12 cm
o Outlet is 12 cm
Measurements of the Transverse Diameter (Horizontal)
o Brim is longer in this diameter o Outlet is the narrowest o Cavity is 12 cm o Brim is 13 cm o Outlet is 11 cm
Importance of Shape in the Female Pelvis
• Shape is important for determining the suitability for childbirth
Main Female Pelvic Shapes
Gynecoid
Android
Platypelloid
Anthropoid
Gynecoid
Typical female shaped pelvis with an oval shaped inlet
Most suitable for childbirth (43%)
Android
A masculine pelvic shape with a heartshaped inlet, prominent ishcial spines and a narrower pelvic outlet (33%)
Platypelloid
Shortened in the anteroposterior dimension of the pelvic inlet and wider in the transverse dimension (2%)
Anthropoid
Oval shaped inlet with a greatly elongated anteroposterior dimension and a shortened transverse dimension
It possesses a larger outlet (24%)
Location of the Pelvic Wall
Posteriorly and laterally
Pelvic Wall muscles
o Piriformis x 2
o Obturator Internus x2
Pelvic Floor (pelvic Diaphragm) Location
Located centrally
Pelvic Floor muscles
o Levator ani and its three parts x2
o Coccygeus x2
Location and Formation of the Sacral Plexus
- Left and right is formed by the ventral rami of spinal nerves L4-S4
- Both lies on the pelvic surface of the piriformis muscle
Major periphreal nerves arising from the sacral plexus
o Sciatic nerve
o Pudenal Nerve
Sciatic Nerve
Largest nerve in the body
Follows the piriformis muscle through the greater sciatic foramen and innervates the leg (except the thigh, this is done by the femoral nerve)
Pudendal Nerve
Passes through the greater sciatic foramen but then re-enters through the lesser sciatic foramen and innervates the structures of the perineum
Lumbosacral Plexus
• The lumbar and sacral plexus combined
Male Pelvic Organs and Structures
- Peritoneal Cavity
- Pelvic Ureters (origin at the pelvic brim)
- Urinary bladder (holds about 500mL of urine)
- Ductus deferens
- Seminal Vesicles
- Prostate gland
- Rectum
- Sigmoid Colon
- Blood Vessels
- Lymphatics
Retrovesical Pouch
- Posterior recess between the urinary bladder and rectum
- The lowest point in the abdomen in males
- The location where fluid may pool when standing upright
Male Parietal Peritoneum
• Can be seen lining the superior surface of the urinary bladder
Location of the Prostate Gland
• Located medial to the Levator ani muscles, superior to the deep perineal pouch and inferior to the urinary bladder
5 surfaces of the prostate gland
o Base/Superior Surface
o Anterior Surface
o Inferoposterior Surface
o Two lateral surfaces
What is contained within the posterior wall of the prostatic urethra
o Urethral crest and its seminal colliculus (which is a raised region on the urethra)
o Prostatic sinuses with opening of the prostatic excretory ducts
o Prostatic utricle and openings of the L and R ejaculatory ducts
What is the prostate gland composed of?
o Glandular tissue and consists of numerous tubuloalveolar glands
o Traditional lobar description of the prostate gland includes the anterior lobe, middle/median lobe (between the prostatic urethra and ejaculatory ducts), two lateral lobes and an Inferoposterior lobe
What does the ductus deferens and seminal vesicle unite to form?
• Ductus deferens and seminal vesicles unite to form the ejaculatory duct that drains into the prostatic urethra
Female Pelvic Organs and Structures
- Peritoneal cavity
- Peritoneal folds/ligaments
- Ovaries
- Uterine tubes
- Uterus
- Vagina
- Pelvic Ureters
- Urinary bladder
- Sigmoid colon
- Rectum
- Blood vessels
- Lymphatics
Uterovesical Pouch
- Anterior recess between the urinary bladder and uterus
* Fluid can build up and pool in this region
Rectouterine Pouch
- Posterior recess located between the uterus and the rectum
- Also called the Pouch of Douglas
- Fluid can build up and pool in this region
Parietal Peritoneum: Female
- Lining the superior surface of the urinary bladder and enveloping the uterus
- Uterus is positioned almost horizontal
Typical positioning of the uterus
• Adult uterus is typically anteverted (tipped anterior relative to the axis of the vagina) (between vagina and cervix) and anteflexed (body is flexed anterior relative to the cervix) (between cervix and body of the uterus)
Variation of the positioning of the uterus
- The uterus can be retroverted and or retroflexed
* Position can change with the distention of the urinary bladder
Uterine Tube Location
• Uterine tubes will be extending from the uterus
What does the Round Ligament Pass Through
• Round Ligament passes through the inguinal canal
Blood Supply Common to Male and Female
- Internal Iliac Arteries (x2)
- Middle/medial Sacral Artery (x1)
- Superior Rectal Artery (x2)
- Internal Pudenal Arteries (x2)
Internal Illiac Arteries
o Origin – Terminal branch of the common iliac artery
o Each internal iliac artery consists of an anterior trunk and a posterior trunk
o Anterior trunk consists of numerous intermediary branches that supply the pelvic organs
Middle/Medial Sacral Artery Origin
o Origin – Collateral branch of the posterior aspect of the abdominal aorta
Superior Rectal Artery (Origin)
o Origin – Continuous of inferior mesenteric artery
Internal Pudendal Artery (Origin)
o Origin – Terminal branch of the anterior trunk of the internal iliac artery
Blood Supply Specific to Males
Testicular Arteries (x2) o Origin – Collateral branches of the abdominal aorta o Leaves the pelvic cavity and enters the inguinal canal to then supply blood to the testes
Blood Supply Specific to Females
Ovarian Arteries (x2) o Origin – Collateral branches of the abdominal aorta o Supplies blood to the ovaries in the pelvic cavity
Boundaries of the Perineum
- Superior Boundary: Pelvic Diaphragm
- Inferior Boundary: Perineal Skin
- Each Lateral Boundary: Obturator internus and ischiopubic ramus
Perineum
- Located superficial/inferior to the muscles of the pelvic diaphragm
- Region is sexual dimorphic due to the differing external genitalia
- Perineal region forms a diamond shape, which is made up two separate triangles (the urogenital triangle anteriorly and the anal triangle posteriorly)
What is the Perineum bounded by?
- Bounded anteriorly by the pubic symphysis, anterolaterally by the ischiopubic rami, laterally by the ischial tuberosities, posterolateral by the sacrotuberous ligaments and posteriorly by the coccyx
- Externally, the perineum is bounded by the medial thigh and gluteal folds/buttocks
Urogenital Triangle
- Contains the urethra and the genitalia (sexual dimorphic)
- Both males and females have a deep perineal pouch (urogenital triangle) that attaches laterally to the ischiopubic ramus
- Urethra passes through the urogenital region in both males and females
What is the Urogenital Triangle Bounded by?
• Bounded inferiorly by a perineal membrane and forms a muscular shelf
What is contained within the urogenital triangle in males?
bulbourethral glands and the root of the penis
What is contained within the urogenital triangle in females
vagina and external genitalia
Superficial perineal pouch
• Located inferior to the deep perineal pouch and contains three paired muscles, the internal Pudenal artery and Pudenal nerve, and erectile tissue of the penis and clitoris
Perinal Body
- Median fibromuscular mass located between the anus and vagina or bulb of penis
- Muscles of the pelvic floor and perineum converge at this point
What does the Anal Triangle Contain
• Contains the anal opening (same in both sexes)
What are the four subregions between the roof and floor in the female urogenital region?
o Anterior recesses of ischiorectal fossa filled with fatty tissue
o Deep perineal pouch/urogenital diaphragm (muscular shelf)
o Superficial perineal pouch
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o Skin, superficial fascia and parts of external genitalia
external genitalia/vulva (female)
- Most of the external genitalia is located inferior to the superficial perineal pouch
- Labia majora
- Labia minora
- Vestibule of the vagina
- Clitoris
What are the four subregions between the roof and floor in the male urogenital region? (male)
o Anterior recesses of ischiorectal fossa filled with fatty tissue
o Deep perineal pouch/urogenital diaphragm
o Superficial perineal pouch
o Skin, superficial fascia and parts of external genitalia
external genitalia/vulva (male)
• External Genitalia o Testis x2 o Epididymis x2 o Spermatic Cord x2 o Tunica vaginalis (tissue surrounding testis) o Fascia and muscles
Anal Region: Roof Formation
• Roof is formed by the Levator ani muscles of the pelvic diaphragm,
Anal Region: Floor Formation
• Floor is formed by perineal skin and the lateral walls are made up of the obturator internus muscles and the ischiopubic rami
Anal Region: General
- Not sexually dimorphic
- Contents of the anal region include the anal canal and the ischiorectal/ischiorectal fossae (fatty filled spaces)
- Branches of the pudendal nerve are supplying the region
Where is the ischiorectal fossae located?
• Located lateral to the anal canal and contains fatty tissue and the pudendal canal (carrying the internal pudendal artery/vein and the pudendal nerve)
What is the ischiorectal fossae
• There are recesses of the ischiorectal fossae that extend anteriorly into the urogenital region, superior to the deep perineal pouch/urogenital diaphragm
What does the Ischiorectal fossae do?
• Fossae allow for movement of the pelvic diaphragm
Pudendal Canal Location
• Located in the deep fascia of the obturator internus muscle
What does the internal pudendal artery supply blood to
• Internal pudendal artery supplies blood to the skin, external genitalia, and muscles of the perineum
Branch of the Internal Pudendal Artery
• Inferior rectal artery is a branch of the internal pudendal artery
Anal Canal
- Terminal part of the large intestine that extends from the anorectal/perineal flexure to the anus
- Orientated posteroinferiorly and is approximately 4cm in length
What is surrounding the anal canal?
• Surrounding the anal canal is the external anal sphincter (skeletal muscle) and internal anal sphincter
Anterior Relation of the anal canal
o Bulb of the penis or vagina, deep perineal pouch/urogenital diaphragm, and the perineal body
Posterior Relation of the Anal Canal
o Anococcygeal ligament
Blood Supply of the Anal Canal: Superior Half
• Superior half of the anal canal is supplied by a branch of the inferior mesenteric artery
Blood Supply of the Anal Canal: Inferior Half
• Inferior half is supplied by branches of the internal iliac artery (including the internal pudendal artery)
Venous drainage of the anal canal
• Venous drainage follows the arterial pattern
