Chapter 5: Pelvis & Perineum Flashcards
divided into the false pelvis and true pelvis
pelvis
the superior region and contains the upper parts of the pelvic bones and lumbar vertebrae
false pelvis
contains the inferior part of the pelvic bones, sacrum, coccyx, and pelvic outlet
true pelvis
inferior to the floor of the pelvic cavity and contains external genitalia, and opening to the genitourinary and gastrointestinal systems
perineum
Contains and supports bladder, rectum, anal canal, and reproductive tracts
pelvis
contains most of the reproductive tract in women and some of it in men
pelvic cavity
passes through the pelvic floor to the perineum where it opens externally
urethra in women
passes through the floor of the pelvic cavity to the perineum and passes into the base of the penis
urethra in men
- the site of connection between the reproductive and urinary systems
- contains major reproductive glands
pelvic cavity in men
- firmly anchored to the bony margin of the pelvic outlet and the fibrous perineal membrane
- contain erectile vascular tissue and skeletal muscle
roots of the external genitalia
bony ring formed by the sacrum, pelvic bones, and pubic symphysis
pelvic inlet
mostly formed by bone, muscle, and ligaments
pelvic walls
form most of the pelvic walls
- sacrum
- coccyx
- pelvic bones
form part of the pelvic wall and help form the greater and lesser sciatic foramina
sacrotuberous and sacrospinous ligaments
- complete the pelvic walls
- arise in the pelvis and exit through the sciatic foramen to act on the hip joint
piriformis and obturator internus muscles
formed by the bony pubic arch and the sacrotuberous ligaments
pelvic outlet
formed by muscle and fascia and separates the pelvic cavity from the perineum
pelvic floor
form most of the bowl shaped pelvic diaphragm
2 levator ani muscles
-(iliococcygeus and
pubococcygeus)
fascial sheath that fills the space between the arms of the pubic arch
perineal membrane
- continuous with the peritoneum of the abdominal cavity
- drapes over the superior aspect of the pelvic viscera and in most cases does not reach the pelvic floor
peritoneum of the pelvic cavity
lie on the midline of the pelvic cavity
pelvic viscera
divides the perineum into the urogenital triangle and the anal triangle
imaginary line
contains the roots of the external genitalia
urogenital triangle
contains the openings to the vagina and urethra
urogenital triangle in women
enclosed in erectile tissue and opens at the end of the penis
urethra in men (urogenital triangle)
what do all structures passing between the pelvic and abdominal cavities pass through?
pelvic inlet
what are the 3 apertures in the pelvic wall that communicate with the lower limb?
- Greater sciatic foramen
- Lesser sciatic foramen
- Obturator foramen
allows communication between the pelvic cavity and perineum
A gap between the pubic symphysis and the perineal membrane
what is the position of the pelvic cavity in anatomical position?
**tilted forward 50°-60°
-means the anal triangle
faces posteriorly while
the urogenital triangle
faces inferiorly
connect the kidneys to the bladder and are located on the lateral wall of the pelvic cavity
ureters
what crosses the ureter in women?
uterine artery
what crosses the ureter in men?
ductus deferens
passes through the prostate in men
urethra
what is the position of the prostate (in men)?
anterior to the rectum
largely innervated by spinal cord levels S3 to S5
perineum
innervates anterior parts of the perineum
Spinal cord level L1
predominantly innervate the lower limb
Levels from L2 and S2
provided by by spinal cord levels S2 to S4 (pudendal nerve)
Somatic skeletal muscle and sensory information of this region
- the major nerve of the perineum
- exits the pelvic cavity through the lesser sciatic foramen
pudendal nerve
closely associated to the ischial spine of the pelvis and can be accessed by palpating the ischial spine
pudenal nerve
controlled by parasympathetic fibers from spinal cord level S2-S4
Genital erection in men and women
enter the inferior hypogastric plexuses on either side
sacral spinal nerves
penetrate the pelvic floor and innervate the erectile tissues in the penis or clitoris
nerves from hypogastric plexuses
intersect with structures of the perineum at the pelvic body
structures of the pelvic floor
what are the structures that converge at the perineal body?
- Levator ani muscles
- Muscles of urogenital and anal triangles, including skeletal muscles sphincters associated with the urethra, vagina, and anus
how is the course of the urethra in men and women different?
- in women it is short
- in mean it is longer and has 2 angles associated with it
consists of 2 pelvic (hip) bones and the sacrum and coccyx
pelvis
- made up of 2 parts separated by the linea terminalis
- have important landmarks that include spines, tuberosity’s, notches, and tubercles
pelvic bone
forms the walls of the false pelvic cavity
pelvic bone above linea terminalis
forms the lateral wall of the true pelvis
pelvic bone below the linea terminalis
the articular socket for the head of the femur
acetabulum
have important landmarks that include spines, tuberosity’s, notches, and tubercles
pelvic bone
formed by the ilium, ischium, and pubis
each pelvic bone
most superior pelvic bone
ilium
anterior pelvic bone
pubis
posterior pelvic bone
ischium
where do the ilium, pubis, and ischium converge?
acetabulum
separates the upper and lower parts of the ilium
arcuate line
expanded into a flat “wing” shaped piece of bone
upper part of ilium (pelvic bone)
connects the pelvic bones to the sacrum
L-shaped articular surface
-an inverted triangle formed from 5 fused sacral vertebrae
sacrum
contain anterior and posterior rami
Anterior and posterior sacral foramina
has an L-shaped facet for articulating with pelvic bones
Each lateral surface of sacrum
between sacrum and LV, formed by zygapophyseal joint and an intervertebral disc
Lumbrosacral joints
synovial joints that transmit forces from the lower limbs to the vertebral column, stabilized by anterior sacro-iliac ligaments
Sacro-iliac joints
- stabilized by interosseous sacro-iliac ligaments and posterior sacro-iliac ligaments
- become fibrous with age and can become completely ossified
Sacro-iliac joints
lies anteriorly between adjacent surfaces of the pubic bones
pubic symphysis joint
covered by hyaline cartilage
each of the pubic symphysis joint surfaces
links the surfaces across the midline of the pubic symphysis joint
fibrocartilage
what are the ligaments associated with the pubic symphysis joint?
- Superiorly- superior pubic ligament
- Inferiorly- inferior pubic ligament
located in the same plane in anatomical position
anterior iliac spines and the pubic symphysis
tilted anteriorly
pelvic inlet
are positioned nearly horizontal
bodies of the pubic bones and the pubic arch
more circular in women
pelvic inlet
more acute in men (50°-60°) than in women (80°-85°)
Angle formed by the 2 pubic arches
do not project as far medially in women as in men
ischial spines
- circular opening between the abdominal and pelvic cavities
- completely surrounded by bones and joints
pelvic inlet
forms the margin of the pelvic inlet posteriorly
promontory of the sacrum forms
formed by the margin of the ala, arcuate line, pecten pubis, pubic crest, and pubic symphysis
margins of the pelvic inlet moving laterally
formed by the sacrum, coccyx, and pelvic bones inferior to the linea terminalis, 2 ligaments, and 2 muscles
walls of pelvic cavity
- ligaments of pelvic wall
- prevent upward tilting and form greater and lesser sciatic notches
sacrospinous and sacrotuberous ligaments
- muscles of the pelvic wall
- originate in the pelvic cavity but insert onto the femur
obturator internus and piriformis muscles
a fan-like muscle that makes a 90° bend around the ischium
obturator internus
is triangular in shape and passes through the greater sciatic foramen
piriformis muscles
ORIGIN:Anterolateral wall of true pelvis (deep surface of obturator membrane and surrounding bone)
obturator internus
INSERTION: Medial surface of greater trochanter of femur
obturator internus
INNERVATION: Nerve to obturator internus (L5 and S1)
obturator internus
FUNCTION: Lateral rotation of the extended hip-joint; abduction of flexed hip
obturator internus
ORIGIN: Anterior surface of sacrum between anterior sacral foramina
piriformis
INSERTION: Medial side of superior border of greater trochanter of femur
piriformis
INNERVATION: Branches from S1 and S2
piriformis
FUNCTION: Lateral rotation of the extended hip joint; abduction of flexed hip
piriformis
what are the 3 apertures of the pelvic wall?
- obturator canal
- the greater and lesser sciatic foramina
diamond shaped and defined anteriorly predominantly by bone and posteriorly by ligaments
pelvic outlet
pass through the pelvic outlet
Terminal parts of the urinary, gastrointestinal tracts and vagina
muscular part of the pelvic floor
pelvic diaphragm
- forms the pelvic diaphragm
- made of 3 muscles
levator ani
- attaches to the pubic bone, tendinous arch, and spine of ischium
- In the midline it blends with the vagina (in females) and the anal aperture in both sexes
levator ani
form the anococcygeal ligament posteriorly
levator ani
ORIGIN: In the line around the pelvic wall beginning on the posterior aspect of the pubic bone and extending across the obturator internus muscle as a tendinous arch (thickening of the obturator internus fascia) to the ischial spine
levator ani
INSERTION: Anterior part is attached to the superior surface of the perineal membrane; the posterior part meets is partner on the other side at the perineal body, around the anal canal, and along the anococcygeal ligament
levator ani
INNERVATION: Branches directly from the anterior ramus of S4, and by the inferior rectal branch of the pudendal nerve
levator ani
FUNCTION: Contributes to the formation of the pelvic floor, which supports the pelvic viscera, maintains an angle between the rectum and anal canal; reinforces the external anal sphincter and, in women, function as a vaginal sphincter
levator ani
ORIGIN: Ischial spine and pelvic surface of the sacrospinous ligament
Coccygeus
INSERTION: Lateral margin of coccyx and related border of sacrum
Coccygeus
INNERVATION: Branches from the anterior rami of S3 and S4
Coccygeus
FUNCTION: Contributes to the formation of the pelvic floor, which supports the pelvic viscera; pulls coccyx forward after defecation
Coccygeus
- is a thick fascial triangular structure that spans the gap between the bony pelvic framework of the pubic arch
- is related to the deep perineal pouch
perineal membrane
located above the perineal membrane
deep perineal pouch
part of the pelvic floor in the urogenital hiatus
perineal membrane
penetrates the perineal membrane and passes into the deep perineum pouch
urethra
-group of muscle fibers, within the deep perineal pouch, surrounding the urethra in men and women
external urethral sphincter
what are the 2 additional groups of muscle fibers that surround the urethra and vagina in women?
- sphincter urethrovaginalis
- compressor urethrae
FUNCTION: From the inferior ramus of the pubis on each side and adjacent walls of the deep perineal pouch
External urethral sphincter
INSERTION: Surrounds membranous part of urethra
External urethral sphincter
INNERVATION: Perineal branches of the pudendal nerve (S2 to S4)
External urethral sphincter
FUNCTION: Compresses the membranous urethra; relaxes during micturition
External urethral sphincter
ORIGIN: Medial aspect of ischial ramus
Deep transverse perineal
INSERTION: Perineal body
Deep transverse perineal
INNERVATION: Perineal branches of the pudendal nerve (S2 to S4)
Deep transverse perineal
FUNCTION: Stabilizes the position of the perineal body
Deep transverse perineal
ORIGIN: Ischiopubis ramus on each side
Compressor urethrae (women only)
INSERTION: Blends with partner on other side anterior to the urethra
Compressor urethrae (women only)
INNERVATION: Perineal branches of the pudendal nerve (S2 to S4)
Compressor urethrae (women only)
FUNCTION: Functions as an accessory sphincter of the urethra
Compressor urethrae (women only)
ORIGIN: Perineal body
Sphincter urethrovaginalis (women only)
INSERTION: Passes forward lateral to the vagina to blend with partner on other side anterior to the urethra
Sphincter urethrovaginalis (women only)
INNERVATION: Perineal branches of the pudendal nerve (S2 to S4)
Sphincter urethrovaginalis (women only)
FUNCTION: Functions as an accessory sphincter of the urethra (also may facilitate closing the vagina)
Sphincter urethrovaginalis (women only)
-positioned in the midline along the posterior border of the perineal membrane, -attaches to perineal membrane
perineal body
also attaches to the perineal body
posterior end of the urogenital hiatus (levator ani muscle)
intersects the perineal body
deep transverse perineal muscle and sphincter urethrovaginalis in women
what are the pelvic viscera?
GI, urinary, and reproductive systems
where are the pelvic viscera (GI, urinary, reproductive) found?
in the midline of the cavity
arises from the pelvic walls and passes medially to the organs
Neurovascular supply
continuous with the sigmoid colon above and the anal canal below
rectum
penetrates the pelvic floor and the perineum and ends as the anus
anal canal
what are the pelvic parts of the urinary system?
- distal ends of the ureters
- bladder
- proximal part of the urethra
- enter the pelvic cavity anterior to the bifurcation of the common iliac and cross the ductus deferens in men and the uterine artery in women
- enter the base of the bladder
ureters
- expands superiorly into the abdomen when full
- the most anterior element of the pelvic viscera
bladder
has a 3-sided pyramid shape with a base, apex, superior, and inferolateral surfaces
empty bladder
continues off the apex to the umbilicus
median umbilical ligament
surrounds the origin of the urethra where the 2 inferolateral surfaces and the base intersect
neck of the bladder
how is the neck of the bladder held in place?
- pubovesical ligament in women
- puboprostatic ligament in men
blends with the capsule surrounding the prostate gland
puboprostatic ligament
- about 4 cm long
- passing through the deep perineal pouch and perineal membrane
urethra in women
- about 20 cm long
- bends twice along its course
- passes through the prostate, deep perineal pouch and perineal membrane and directly into the root of the penis
urethra in men
what are the 4 parts of the urethra in men?
- preprostatic part
- prostatic part
- membranous part
- spongy part
3 to 4 cm long and surrounded by the prostate
prostatic part of urethra
marked by the urethral crest, openings of ducts, prostatic utricle, and ejaculatory ducts
lumen of the prostatic urethra
come from the male reproductive tract
Ejaculatory ducts
-has components in the abdomen, pelvis, and perineum
reproductive system in men
what are the major components of the reproductive system in men?
- testis
- epididymis
- ductus deferens
- ejaculatory tract on each side
- urethra and penis in the midline
what are some important glands in the male reproductive system?
- the single prostate
- paired seminal vesicles
- paired bulbo-urethral glands
the connection between the testis and abdomen
spermatic cord
contains the tunica vaginalis, capsule, seminiferous tubules, straight tubules, rete testis, efferent ductules, epididymis (head, body, and tail)
testes
stored in the epididymis until ejaculation
spermatozoa
- accessory glands of the male reproductive system
- formed as blind-ended outgrowths from the ductus deferens
seminal vesicles
joins the ductus deferens and forms the ejaculatory duct
duct from the seminal vesicle
found inferior to the bladder
prostate gland
passes through the prostate
urethra
found mainly in the pelvic cavity and peritoneum
reproductive system in women
what are the major components of the reproductive system in women?
- ovary on each side
- uterus
- vagina
- clitoris in the midline
- pair of greater vestibular glands
- descend from the same location as the testis in men but do not migrate through the inguinal canal
- bring their lymphatics, vessels, and nerves with them when they descend
ovaries
- assume a position in the lateral wall of the pelvic cavity
- site of oogenesis
ovaries
ovulated into the peritoneal cavity and directed to the uterine tubes by cilia
eggs
- A thick walled muscular organ
- Composed of body and cervix which joins the vagina
- fundus is rounded superior end
uterus
extend from the superior end of the uterus to the lateral pelvic wall
uterine tubes
the expanded end of the unterine tubes that wraps around the superolateral pole of the ovary
infundibulum
extend off the margins of the infundibulum
fimbriae
- Forms the inferior part of the uterus
- the end of it is dome shaped and bulges into the vagina forming the anterior and posterior fornix
cervix
opens into the vagina
external os (of cervix)
opens into the uterus
internal os (of cervix)
- copulatory organ in women
- fibromuscular tube that extends from the perineum through the pelvic floor and into the pelvic cavity
vagina
enlarged to form the vaginal vault
internal end of the vagina
formed between the margin of the cervix and vaginal walls
lateral, posterior, and anterior fornixes
separates the posterior surface of the vagina from the rectum
rectovaginal septum in women
help stabilize the uterus in the pelvic cavity
pubocervical, transverse cervical, and uterosacral ligaments
what is the most important ligament that helps stabilize the uterus in the pelvic cavity?
the transverse ligament that attaches laterally to the pelvic wall
contains the prostatic plexus of veins
prostatic fascia (in men) on the lateral and anterior surfaces of the prostate
continuous with the rectovesical septum which separates the posterior surface of the prostate and base of the bladder from the rectum
prostatic fascia
separates the posterior surface of the prostate and base of the bladder from the rectum
rectovesical septum
drapes over the pelvic viscera, covering the anterior surface of the viscera
peritoneum
what are the 2 pouches formed in women?
- anteriorly the vesico-uterine pouch
- posteriorly the recto-uterine pouch
is a sheet-like fold of the peritoneum enclosing the uterine tube and the ovary
broad ligament
what are the 3 parts of the broad ligament?
- mesometrium
- mesovarium
- mesosalpinx
what are other ligaments of the peritoneum in the pelvis? (in women)
- suspensory
- ligament of ovary
- round
drapes over the bladder and reflects up onto the rectum
-only the rectovesical pouch between the rectum and bladder
peritoneum in men
-formed by anterior rami of S1-Co, with significant contributions from L4 and L5
sacral and coccygeal plexuses
- mainly somatic plexuses
- supply muscles of the leg, pelvis, and perineum
- Cutaneous branches supply skin of the leg, foot, and perineum
sacral and coccygeal plexuses
formed by anterior rami of S1-S4 and the lumbrosacral trunk (L4 and L5)
sacral plexus
has a ventral and dorsal division that combines with similar divisions from other levels
each anterior ramus of sacral plexus
originates from S2-S4
pelvic splanchnic nerve
a large nerve of the lower limb
sciatic nerve
innervates skin and skeletal muscle of perineum
pudendal nerve
- from the ganglia of the sympathetic trunk
- connect to each anterior rami
- carry postganglionic fibers
- destined for the periphery, to the somatic nerves
gray rami communicantes
originate from S2 to S4 and provide preganglionic parasympathetic fibers to the prevertebral hypogastric plexus
pelvic splanchnic nerves
forms the paravertebral plexus in the pelvis
sympathetic trunk
leave the paravertebral trunk
sacral splanchnic nerves
enters sympathetic trunk as bundles called hypogastric nerves
prevertebral plexus
joined by pelvic splanchnic nerves forming the inferior hypogastric plexuses
hypogastric nerves
innervates pelvic viscera and reproductive organs
- erectile tissues of the penis and clitoris and bladder control (parasympathetic) - innervates blood vessels, smooth muscle associated with reproductive tract (sympathetic)
visceral plexus
generally carry pain
Afferent fibers heading back to the CNS (from visceral plexus)
- major artery of the pelvis and perineum
- supplies the viscera, walls, floor of the pelvis, and structures of the perineum
- divides into the anterior and posterior trunk around the pelvic inlet
internal iliac
supplies the lower posterior abdominal wall, posterior pelvic wall, and gluteal region
posterior trunk of internal iliac artery
supplies the pelvic viscera, perineum, gluteal region, and the adductor region of the thigh
anterior trunk of internal iliac artery
originates off the aorta and descends down the midline
median sacral artery
- crosses the ureter as it passes medially to the cervix where it anastomoses with the vaginal artery
- major blood supply to the uterus and enlarges during pregnancy
uterine artery in women
- originate off the aorta and then descend into the pelvis
- travel through the suspensory ligament as they cross the pelvic inlet
- anastomose with the uterine arteries
gonadal (ovarian) vessels in women
- drains erectile tissue of the penis and clitoris and does not follow the same route as the deep pudendal artery
- joins the venous plexuses in the pelvis
deep dorsal vein
Within the pelvic cavity extensive venous plexuses are associated with……
- bladder
- rectum
- uterus
- vagina
drain into lymph nodes associated with the iliacs
Lymphatics from most pelvic viscera
drain into lateral aortic or lumbar nodes and then into lumbar trunks and then into the thoracic duct
lymph nodes associated with the iliacs
- A diamond shaped region inferior to the pelvic floor
- Boundaries are: the pelvic outlet (periphery)
- divided into the urogenital triangle and anal triangle
perineum
houses the openings to the urinary and reproductive systems
urogenital triangle
contains the anus and the external anal sphincter
anal triangle
the major nerve and artery of the perineum
pudendal nerve (S2 to S4) and the internal pudendal artery
forms the ischio-anal fossa
curved shape of the levator ani muscle
form the ischio-anal recesses
parts of the the ischio-anal fossa that are between the levator ani and the anal triangle
normally filled with fat
ischio-anal fossa and its recesses
formed by the levator ani muscle
ceiling of the anal triangle
major muscle of the anal triangle
external anal sphincter which surrounds the anal canal
what are the 3 parts of the external anal sphincter?
- deep
- superficial
- subcutaneous
Contains the roots of the genitalia and the openings of the urogenital systems
urogenital triangle
- lies between the perineal membrane and a layer of superficial fascia
- contains the erectile tissues of the penis and clitoris and associated skeletal muscle
superficial perineal pouch
- homologues
- provide secretions during sexual arousal
greater vestibular and bulbo-urethral glands
what are the muscles of the superficial perineal pouch?
- ischiocavernosus
- bulbospongiosus
- superficial transverse perineal muscles
function in the movement of blood into the erectile tissues and ejaculation in men
- ischiocavernosus
- bulbospongiosus
- superficial transverse perineal muscles
ORIGIN: Ischial tuberosity and ramus
Ischiocavernosus muscle
INSERTION: crus of penis or clitoris
Ischiocavernosus muscle
INNERVATION: Pudendal nerve (S2-S4)
- ischiocavernosus
- bulbospongiosus
- superficial transverse perineal muscles
FUNCTION: Move blood from crura into the body of the erect penis or clitoris
Ischiocavernosus muscle
ORIGIN: In women: perineal body. In men: perineal body and midline raphe
Bulbospongiosus muscle
INSERTION: In women: bulb of vestibule, perineal membrane, body of clitoris, and corpus cavernosum. In men: bulbospongiosus, perineal membrane, corpus cavernosum
Bulbospongiosus muscle
FUNCTION: Move blood from attached parts of the clitoris and penis into the glans. In men: removal of residual urine from urethra after urination; pulsatile emission of semen during ejaculation
Bulbospongiosus muscle
ORIGIN: Ischial tuberosity and ramus
Superficial transverse perineal muscle
INSERTION: perineal body
Superficial transverse perineal muscle
FUNCTION: stabilize the perineal body
Superficial transverse perineal muscle
form the vulva (in women)
- vestibule apparatus
- clitoris
- a number of skin and tissue folds
- are found lateral to the vestibule
- minora unite anteriorly to form the frenulum of the clitoris and posteriorly to form the fourchette
labia minora
surrounded by the hymen which may completely close the opening
vaginal opening
superficial components of the genitals in men
- scrotum
- penis
homologues with the labia majora
scrotum
covered by the glans penis
tip of the body of the penis
normally covered with a prepuce (foreskin)
glans penis
-continuous with similar fascia of the abdominal wall
superficial fascia of the urogenital triangle
- membranous layer attaches to the perineal membrane and therefore does not extend onto the anal triangle
- attaches onto the ischiopubic rami and therefore does extend onto the thigh
superficial fascia of the urogenital triangle
- major somatic nerve of the perineum
- leaves the pelvic cavity through the greater sciatic foramen
- enters the perineum by passing medially through the lesser sciatic foramen
pudendal nerve
what are the 3 major terminal branches of the pudenal nerve in the perineum?
- inferior rectal nerve
- perineal nerve
- dorsal nerve of penis/clitoris
most significant artery to the perineum
pudendal artery
what are the Terminal branches of the internal pudendal artery in men?
- artery of the bulb of the penis
- urethral artery
- deep artery of the penis
- dorsal artery of the penis
what are the Terminal branches of the internal pudendal artery in women?
- arteries to bulb of the vestibule
- deep arteries of the clitoris
- dorsal arteries of the clitoris
follows the internal pudendal artery
internal pudendal vein
drains into the venous plexus associated with the prostate/bladder
deep dorsal vein
accompany the internal pudendal artery to the internal iliac nodes
Lymphatics from deep parts of the perineum
drain into the superficial inguinal nodes
Lymphatics from superficial parts of the perineum
drain into the deep inguinal and external iliac nodes
- glans penis
- glans clitoris
- labia minora
