Anatomy of the Pelvis

Question 1

Which bones form the pelvic girdle?

Answer 1

Right and left hip bones and sacrum.

Question 2

What type of joints are the sacro-iliac joints and the pubic symphysis?

Answer 2

Sacro-iliac joints are synovial with NO MOVEMENT.

Pubic symphysis is secondary cartilaginous with no movement.

Question 3

What 3 bones fuse to form hip bone?

Answer 3

Ilium (superior), pubis (medial) and ischium (lateral).

Question 4

Contrast the male and female pelvis.

Answer 4

Male pelvic inlet is narrow and heart shaped. Female pelvic inlet is oval and round.
Male sub-pubic angle is narrow at 50-60. Female is wide: >80.
Male ischial spines project medially. Female ischial spines do not project medially.

Question 5

Why is the male internal urethral sphincter well developed?

Answer 5

Needs to close in ejaculation to prevent semen entering bladder.
Sympathetic stimulus closes the sphincter.

Question 6

What is the pelvic floor?

Answer 6

A fibromuscular structure separating the pelvic cavity from the perineum.

Question 7

Which muscles form the pelvic diaphragm?

Answer 7

The 3 parts of the levator ani (the puborectalis, the pubococcygeus and the iliococcygeus muscles) and the coccygeus muscle.

Question 8

Describe the lumbosacral joint (between L5 and the sacrum).

Answer 8

Formed by an intervertebral disc connecting the bodies of L5 and S1, and 2 zygapophysial joints which occur between adjacent inferior and superior articular facets.
The joints are reinforced by iliolumbar and lumbosacral ligaments, which extend from the transverse process of L5 to the ilium and sacrum respectively.

Question 9

What forms the pelvic inlet?

Answer 9

Promontory (of sacrum), margin of ala, arcuate line, pectin pubis, pubic crest, pubic symphysis (and again on the other side).

Question 10

Which ligaments are associated with the lateral pelvic walls?

Answer 10

The sacrospinous ligament: a triangular ligament with its apex attached to the ischial spine and its base attached to the margins of the sacrum and coccyx.

The sacrotuberous ligament: also triangular, attaching the base which extends from posterior superior iliac spine to the coccyx to the apex at the ischial tuberosity.

Question 11

What is the tunica vaginalis?

Answer 11

A closed sac of peritoneum lining the sides and anterior aspect of the testis.
Originally connected to abdominal cavity: now there is a fibrous remnant.

Question 12

What is the epididymis?

Answer 12

Head of the epididymis formed by efferent ductules merging. This sits on the posterior superior pole of the testis.
The true epididymis is a single, long, coiled duct continuing inferiorly as the body of the epididymis, enlarging to form the tail of the epididymis at the inferior pole of the testis (continuous with the ductus deferens).

Question 13

Describe the passage of the ductus deferens.

Answer 13

Begins at tail of the epididymis in the scrotum. Ascends as part of the spermatic cord and passes through the inguinal canal. After passing through the deep inguinal ring, it bends medially around the inferior epigastric artery. Crosses external iliac artery and vein at pelvic inlet to enter pelvic cavity. Continues inferomedially, crossing ureter and joined by seminal vesicle near midline to form ejaculatory duct.

Question 14

What is the ampulla of ductus deferens?

Answer 14

An expansion of the ductus deferens between crossing the ureter and the formation of the ejaculatory duct (by merger with seminal vesicles).

Question 15

Where are the bulbo-urethral glands and what do they do?

Answer 15

They are located in the deep perineal pouch, lateral to the membranous part of the urethra.
The glands contribute to lubrication of the urethra and the pre-ejaculatory emission from the penis.

Question 16

Describe how the uterine tubes attach to the ovaries.

Answer 16

The uterine tube has ends as the infundibulum, which curves around the superolateral poles of the ovaries. The margin of the infundibulum is rimmed with small finger-like projections called fimbriae.
The FIMBRULATED INFUNDIBULUM facilitates the collection of ovulated eggs from the ovary.

Question 17

What are the openings of the cervix?

Answer 17

Internal os (into uterine cavity).
External os (into fornix of vagina).

Question 18

What is the sciatic nerve?

Answer 18

The largest nerve in the body, carrying contributions from L3 to S4.
It forms on the anterior surface of the piriformis muscle and leaves the pelvic cavity through the greater sciatic foramen.

Question 19

At what level does the internal iliac artery arise?

Answer 19

Approximately at the level of the intervertebral disc between L5 and S1.

Question 20

Which passageway transmits the gluteal vessels and nerves?

Answer 20

Greater sciatic foramen.

Question 21

Which nerve causes NO release to dilate blood vessels?

Answer 21

Pelvic splanchnic parasympathetic fibres.

Question 22

What does the pampiniform venous plexus do?

Answer 22

Acts as a counter-current cooling mechanism which cools the arterial blood flowing in the testicular artery.

Question 23

What are the broad ligaments?

Answer 23

Transverse mesenteries joining the uterus to the pelvic walls. Contain the uterine tubes and uterine arteries.

Question 24

What is the function of the cervical ligaments and which is the most important of the 3?

Answer 24

Function is to anchor the cervix in position to prevent the uterus from prolapsing through the vagina.
Most important is the transverse cervical ligament (it is the strongest).

Question 25

What are the compartments of the uterus and uterine tubes?

Answer 25

Uterus consists of fundus, body, lower segment and cervix.

Uterine tubes consist of infundibulum, ampulla, isthmus and uterine parts.

Question 26

Describe how the angles of the body of the uterus, cervix and vagina are related.

Answer 26

Body of the uterus is antiflexed on the cervix.

Cervix is anteverted on the vagina.

Question 27

Which structures are palpable through the vaginal wall?

Answer 27

Cervix, ischial spine, sacral promontory, uterine artery pulse (at lateral fornix), ovary.

Question 28

What structures does the uterine artery supply?

Answer 28

Uterus (enlarges in pregnancy).
Ascending branch supplies uterine tube and ovary.
Descending branch supplies vagina.

Question 29

Why do women have the compressor urethrae and sphincter urethrovaginalis muscles?

Answer 29

As their internal urethral sphincters are not well developed hence a more intricate external urethral sphincter is required for maintaining urinary continence.

Question 30

What is the hymen?

Answer 30

A mucosal fold, often partially perforated at centre, present in vaginal orifice of virgins.

Question 31

What structures are present in the superficial perineal pouch in women?

Answer 31

The vulva (external genitalia) which includes:
Mons pubis, labia majora and minora, clitoris, vestibule of vagina, vestibular bulbs and vestibular glands.

Question 32

Describe the lymph drainage of the pelvis.

Answer 32

Pelvic organs drain to external and internal ILIAC nodes.
Ovary and testis drain to PARA-AORTIC nodes (think blood supply).
Perineum and external genitalia drain to superficial INGUINAL nodes.

Question 33

Where is the iliac tubercle?

Answer 33

Located 5cm posterior to ASIS.

Question 34

What runs in the inguinal canal?

Answer 34

Ilio-ingunal nerve.

Spermatic cord in men; round ligament of uterus in women.

Question 35

Where are the deep and superficial inguinal rings?

Answer 35

Deep inguinal ring is 1.5cm above midpoint between ASIS and pubic symphysis (the mid-inguinal point).
Superficial inguinal ring is superior to the pubic tubercle.

Question 36

What are the measures of the pelvic inlet (pelvimetry)?

Answer 36

Width between ischial spines.

From promontory to superior surface of pubic symphysis.

Question 37

What are the main branches of the pudendal nerve?

Answer 37

Inferior rectal, perineal nerve and dorsal nerve of penis/clitoris.

Question 38

Which nerves pass through the inguinal canal?

Answer 38

Genital branch of genitofemoral nerve and testicular nerve (in the spermatic duct). Ilioinguinal nerve also passes through the inguinal canal, alongside the spermatic duct.

Question 39

Describe what varicocele is.

Answer 39

Caused by abnormal enlargement and dilation of pampiniform plexus. Painless, described as feeling like a “bag of worms”.

Question 40

What forms the pudendal canal?

Answer 40

The fascia of obturator internus.

Question 41

Where is a pudendal block administered?

Answer 41

Where the pudendal nerve crosses the lateral aspect of the sacrospinous ligament near its attachment to the ischial spine.

Question 42

What are the boundaries of the ischio-anal fossae?

Answer 42

Base: skin over anal region.
Medial wall: anal canal and levator ani muscle.
Lateral wall: obturator internus and ischial tuberosity.

Question 43

What is the dartos muscle and what does it do?

Answer 43

It is a muscle in the scrotum which wrinkles the skin to increase heat loss. Supplied by genital branch of genitofemoral nerve.

Question 44

What is significant about the rectouterine pouch?

Answer 44

It is an extension of the peritoneal cavity between the rectum and posterior wall of the uterus which, when the patient is in the supine position, is the lowest portion of the abdominopelvic cavity. A site where fluid and infection collect.

Question 45

What epithelia is present in the endocervix and ectocervix?

Answer 45

Endocervix (cervical canal): mucus-secreting columnar epithelium.
Ectocervix (vaginal surface): stratified squamous non-keratinised epithelium.

Question 46

Which ligaments, part of the pelvic fascia, hold the uterus in position to prevent prolapse?

Answer 46

Pubocervical, uterosacral and transverse cervical.

Question 47

What forms the borders of the inguinal canal?

Answer 47

Roof = 2 Muscles: internal oblique and transversus abdominus.
Anterior wall = 2 Aponeuroses: internal and external oblique aponeuroses.
Floor = 2 Ligaments: inguinal and lacunar ligaments
Posterior wall = 2Ts: transversalis fascia and conjoint tendon.