Pelvic Bones, Cavities, Walls, and Contents

Summary points 6-10

6. You should know the bony and ligamentous parts of the pelvic outlet. 7. The pelvis can be divided into the greater (false) pelvis and (true) lesser pelvis. 8. Pelvic joints consist of the lumbosacral, sacroiliac and pubic symphysis . 9. The walls of the true pelvis consist predominantly of bone, muscle, and ligaments. 10. Two muscles complete the walls of the pelvis: the obturator internus and piriformis.

Describe the obturator internus

A flat, fan-shaped muscle that forms a tendon that leaves the pelvic cavity through the lesser sciatic foramen, makes a 90° bend around the ischium between the ischial spine and ischial tuberosity, passes posteriorly, and crosses the hip joint to insert on the femur. In the above image, the Iliococcygenus is part of the levator ani.

What makes up the vagina?

Anterior, posterior, and two lateral fornices Upper portion of the posterior wall covered by peritoneum

What bones/muscles/ligaments make up the walls of the true pelvis?

Bone - sacrum, coccyx, and inferior half of the pelvic bones. Muscle - obturator internus and piriformis. Ligaments - sacrospinous and sacrotuberous ligaments

What are the pelvic divisions?

Greater pelvis (false pelvis, major pelvis) Lesser pelvis (true pelvis, minor pelvis)

In women, where does the uterus lie?

In women, the uterus lies between the bladder and rectum.

Where are the innominates joined?

Innominates are joined anteriorly at the pubic symphysis. Innominates articulate posteriorly with the sacrum at the sacroiliac (SI) joints.

Male vs female pelvis

Male on the right

What 3 apertures in the pelvic wall allow communication with the lower limbs?

Obturator Foramen Greater Sciatic Foramen Lesser sciatic foramen

*Key concept* What are the 2 important openings in the prostatic urethra?

The *urethral sinuses* has openings for the prostrate and the *seminal colliculus* has openings for the ejaculatory ducts.

What forms the pelvic outlet?

The anterior part of the pelvic outlet is formed by the pubic symphysis. The lateral edge is formed by the ischiopubic ramus. The sacrotuberous ligament extends from the ischial tuberosity to the coccyx and sacrum completing the pelvic outlet.

Where does the bladder sit in relation to the rectum in males?

The bladder is anterior and the rectum is posterior.

What muscles compost the largest components of the funnel shaped pelvic diaphragm?

The levator ani muscles compose the largest components of this funnel-shaped pelvic diaphragm. The anterior region of the pelvic diaphragm contains a U-shaped defect.

In the female, how is the pelvic cavity covered by the peritoneum?

The pelvic cavity is lined by peritoneum continuous with the peritoneum of the abdominal cavity that drapes over superior part of the pelvic cavity

In the male pelvic cavity, how is the pelvic cavity lined by the peritoneum?

The pelvic cavity is lined by peritoneum continuous with the peritoneum of the abdominal cavity that drapes over superior part of the pelvic cavity.

What supports the pelvic floor?

The pelvic floor is supported anteriorly by the perineal membrane and the muscles within the deep perineal pouch.

*Key concept* What does the pelvic foramina connect?

The pelvic foramina allow for Communication between the pelvis and the abdomen and lower extremity.

*Key concept* What is the overall structure of the pelvic inlet?

The pelvic inlet is heart shaped and completely ringed by bone.

*Key concept* What is the shape of the pelvic outlet?

The pelvic outlet is diamond-shaped and formed by bone and ligaments

*Key concept* What covers the superior aspect of most pelvic organs?

The peritoneum covers the superior aspect of most pelvic organs.

What is the pelvic inlet?

The posterior surface of the pelvic inlet is formed by the body of the fused sacral vertebrae. These vertebrae consist of the sacral promontory and the alae (wings). On the lateral surface is a prominent rim called the arcuate line delineating a boundary which continues anteriorly to reach the pubic bones (fused in the midline by the pubic symphysis).

*Key concept* What is the relationship between the uterine artery to the ureter?

The relationship of the uterine artery to the ureter is critically important. The ureter runs under the uterine artery. Remember that "water runs under the bloody bridge."

Where is the true pelvis continuous with the abdominal cavity?

The true pelvis is continuous with the abdominal cavity at the pelvic inlet.

*Key concept* What are the 3 openings of the urinary bladder?

The urinary bladder has 3 openings; 2 openings for the entrance of urine from the ureters and 1 opening called the urethra. Connect the 3 openings and you will see a triangular area called the trigone. *This is a frequent site of urinary bladder infections*

What supports the urinary bladder?

The urinary bladder is supported by adjacent elements of the pelvic bone and by the pelvic floor and the anal canal, which is the most posterior organ, is angled posteriorly on the rectum. This flexure is maintained by muscles of the pelvic floor and is relaxed during defecation.

*Key concept* What do the walls of the true pelvis mostly consist of?

The walls of the true pelvis consist predominantly of bone, muscle, and ligaments.

Describe the piriformis

Triangular in shape and originates in the pelvic cavity and then passes laterally through the greater sciatic foramen, crosses the posterosuperior aspect of the hip joint, and inserts on the femur. In the above image, the Iliococcygenus is part of the levator ani.

What are the major features of the male bladder?

Trigone Apex Neck

*Key concept* T/F: The male and female bladders are virtually the same

True

*Key concept* What are the ligaments that are important for reinforcing the bony elements of the pelvis?

Two ligaments, the sacrospinous ligament and the sacrotuberous ligaments are important for reinforcing the bony elements of the pelvis.

*Key concept* What are the two muscles that make up the walls of the pelvis?

Two muscles complete the walls of the pelvis: the obturator internus and piriformis. These muscles originate in the pelvis but exit through the sciatic foramina to insert and act on the hip joint.

What are the contents of the male pelvic cavity?

Ureter Vas (ductus) deferens Seminal vesicles Ejaculatory ducts Prostate Rectum

*Key concept* What supports the pelvic organs?

Within the female pelvic cavity is some important connective tissue s that support the pelvic organs

Where is the lumbosacral joint?

between L5 and S1 vertebrae

How do the ovaries connect to the lateral pelvic wall?

connected to the lateral pelvic wall by the suspensory ligament of the ovary (which conveys the ovarian vessels, lymphatics, and nerves to the ovary)

What ligaments does the broad ligament of the uterus contain?

contains the round ligament of the uterus and the proper ligament of the ovary

What muscles cover the obturator foramen?

covered by obturator membrane, obturator internus and externus muscles

What kind of joint is the pubic symphysis?

fibrocartilaginous joint; reinforced by the superior and inferior pubic ligaments.

What forms the lesser sciatic foramen?

formed by the lesser sciatic notch, ischial spine, sacrospinous and sacrotuberous ligaments

What is the greater sciatic foramen?

major route of communication between the pelvic cavity and the lower limb

What are the parts of the broad ligament of the uterus?

mesosalpinx, mesovarium and mesometrium

Where do the muscles of the lateral pelvic wall originate?

originate in the pelvic cavity but attach to the femur. In the above image, the Iliococcygenus is part of the levator ani.

What is the pubic outlet bounded by?

1. Inferior margin of pubic symphysis 2. Inferior rami of pubis and ischial tuberosities 3. Sacrotuberous ligament 4. Sacrum and coccyx

What are the pelvic joints?

1. Lumbosacral 2. Sacroiliac 3. Pubic symphysis

Summary points 1-5

1. Pelvic bones transfer weight from vertebral column to lower extremities and provides attachment site for muscles. 2. The pelvis is made up of 4 bones: right and left innominates (= ilium, ischium, pubis), the sacrum and the coccyx. 3. The pelvic inlet is heart shaped and completely ringed by bone. 4. You should know the bony parts of the pelvic inlet. 5. The pelvic outlet is diamond-shaped and formed by bone and ligaments

What are the 3 parts of the male urethra?

1. Prostatic urethra 2. Membranous urethra 3. Penile spongy urethra

What bounds the pelvic inlet (a.k.a. pelvic brim)?

1. Pubic symphysis and crest 2. Pectin pubis 3. Arcuate line 4. Ala of sacrum 5. Sacral promontory

*Key concept* What are the differences between the pelvic floor and the pelvic diaphragm?

1. The pelvic floor is formed by the pelvic diaphragm, the perineal membrane and the muscles in the deep perineal pouch. 2. The pelvic diaphragm is formed by the levator ani and coccygeus muscles from both sides. 3. The pelvic floor separates the pelvic cavity, above, from the perineum, below.

What do the pelvic bones do?

1. Transfers weight from vertebral column to lower extremities 2. Provides attachment site for powerful muscles (abdominals, gluteals...)

What do the the peritoneal coverings cover in females?

1. from the anterior abdominal wall 2. to the level of the pelvic bone 3. superior surface of the urinary bladder 4. forms the vesicouterine pouch 5. covers fundus, body of the uterus; extends over posterior fornix and wall of the vagina 6. forms the rectouterine pouch 7. passes on to the front and sides of the rectum 8. becomes the sigmoid mesocolon

Describe the sacroiliac joint

strong synovial joints/ very little motion here; reinforced by the anterior and posterior sacroiliac ligaments and the interosseous sacroiliac ligament.

Where does the anal canal pass?

the anal canal passes through a posterior circular orifice in the pelvic diaphragm

What is the lateral extension and fold of the broad ligament and what does it contain?

the lateral extension and fold of the broad ligament is the suspensory ligament of the ovary, it contains the ovarian vessels and lymphatics, and autonomic nerves .

How does the vagina and urethra pass from the pelvic cavity to the perineum?

the vagina and the urethra penetrate the pelvic floor to pass from the pelvic cavity to the perineum.

What does the obturator foramen transmit?

transmits obturator nerve and artery through obturator canal.

What does the lesser sciatic foramen transmit?

transmits the obturator internus muscle, pudendal nerve and internal pudendal vessels

What does the greater sciatic foramen transmit?

transmits the superior and inferior gluteal nerves and vessels, piriformis muscle, sciatic nerve, pudendal nerve, internal pudendal vessels, posterior femoral cutaneous nerves, and the nerves to the obturator internus and quadratus femoris muscles

How may layers of peritoneum does the broad ligament of the uterus have?

two layers of peritoneum

Where is the uterine tube in the broad ligament?

uterine tube is contained within its free margin

Describe the urethra in females

very simple and short

What are the parts of the uterus?

• Body - upper two thirds • Fundus - rounded part of the body that lies superior to the orifices of the uterine tubes • Isthmus - constricted region just above the cervix • Cervix - narrow, inferior portion that protrudes into the uppermost vagina

Where does the ureter lie in females?

• Crosses the pelvic brim anterior to the common iliac artery. • Runs medial to the obturator vessels. • Posterior to the ovary.

Where is the ureter in males?

• Crosses the pelvic brim anterior to the common iliac artery. • Runs medial to the obturator vessels. • Posterior to the ovary.

List of things the obturator foramen transmits

1.Obturator nerve 2.Obturator vessels

List of things the lesser sciatic foramen transmits

1.obturator internus mm 2.nerve to obturator internus 3.internal pudendal vessels 4.pudendal nerve

List of things that the greater sciatic foramen transmits

1.piriformis mm 2.sup/inferior gluteal vessels and nerves 3.Internal pudendal vessels 4.pudendal nerve 5.sciatic nerve 6.post cutaneous nerve of the thigh

Summary points 11-14

11. The walls of the true pelvis consist predominantly of bone, muscle and ligaments. 12. The muscles of the lateral pelvic wall originate in the pelvic cavity but attach to the femur. 13. The pelvic foramina allow for communication between the pelvis and the abdomen and lower extremity. 14. There are differences between the pelvic floor and the pelvic diaphragm. • The pelvic floor is formed by the pelvic diaphragm, the perineal membrane and the muscles in the deep perineal pouch. • The pelvic diaphragm is formed by the levator ani and coccygeus muscles from both sides. • The pelvic floor separates the pelvic cavity, above, from the perineum, below.

What are the parts of the uterine tube (fallopian tube)

• Infundibulum - funnel shaped distal end, opens into the peritoneal cavity • Ampulla - widest and longest part, oocytes usually fertilized here • Isthmus - thick walled part, enters the uterus horn • Uterine part - short segment that passes through the uterine wall and opens through the uterine cavity

What 4 bones make up the pelvis?

• Right and left innominates (each innominate = ilium, ischium, pubis) • Sacrum • Coccyx

What does the peritoneal lining cover?

• from the anterior abdominal wall to the level of the pubic bone, • Superior surface of the urinary bladder • Posterior surface of the bladder • Caps the seminal vesicles • Lines the rectovesical fossa (pouch) • Envelops the sides of the rectum (upper 1/3) • Becomes the sigmoid mesocolon

Summary points 15-17

15. The peritoneum covers the superior aspect of most pelvic organs. 16. The male urethra has 3 parts: the prostatic, membranous and penile spongy urethra. 17. The broad ligament of the uterus is composed of 2 layers of peritoneum which can be further subdivided into the mesosalpinx, mesovarium and mesometrium

Where is the lesser pelvis, and what does it hold?

•Between pelvic inlet and outlet •inlet is open - pelvic floor separates the pelvic cavity from the perineum •pelvic viscera

Where is the greater pelvis, and what does it hold?

•Superior to the pelvic inlet •abdominal viscera (ileum, sigmoid colon)

Where does the ureter lie?

•anterior to the common iliac artery - medial to the obturator vessels •posterior and inferior to the vas deferens

Where is the prostate?

•base of the urinary bladder •receives the ejaculatory duct

Summary points 18-20

18. The relationship of the uterine artery to the ureter is critically important. The uterine artery runs under the uterine artery. Remember that "water runs under the bloody bridge." 19. Within the female pelvic cavity is some important connective tissue s that support the pelvic organs. 20. You should be able to list differences between male and female pelvic cavities.

Where does the vas (ductus) deferens lie?

•enters the pelvis at the deep inguinal ring •lateral to the inferior epigastric vessels - anterior (and superior) to the ureter •terminal portion of the vas expands to form the ampulla

Where are the seminal vesicles?

•lateral to the ampulla of the vas deferens

Where are the ejaculatory ducts?

•union of vas deferens and ducts of seminal vesicles •open into the prostatic urethra of the seminal colliculus (future lecture)