SDL - Perineum and External Genitalia

Question 1

What is the perineum bounded by superiorly and inferiorly?

Answer 1

The perineum is the area inferior to the pelvic floor, bounded by the pelvic outlet and limited inferiorly by the skin.

Question 2

Where does the rectum become the anal canal?

Answer 2

At the U-shaped sling created by puborectalis (anorectal angle)

Question 3

How is the anal canal divided into 2 separate parts?

Answer 3

By the pectinate line

Question 4

What is the upper 2/3 of the anal canal derived from?

Answer 4

Derived from the embryonic hindgut (endoderm)

Question 5

Where is lower 1/3 of the anal canal derived from?

Answer 5

Derived from the ectoderm of the proctodeum.

Question 6

Describe the epithelial lining of the upper 2/3 of the anal canal?

Answer 6

Columnar epithelium (same as rectum) but mucosa organised into longitudinal folds, known as anal canals which are joined together at their inferior ends by anal valves. Above the anal valves are anal sinuses (pouches that contain glands which secrete mucus)

Question 7

Describe the epithelial lining of the lower 1/3 of the anal canal?

Answer 7

Non-keratinised stratified squamous epithelium (anal pecten).

Transitions to true skin (keratinised stratified squamous) at level of sphincteric groove

Question 8

Describe the arterial supply of the upper 2/3 of the anal canal?

Answer 8

Superior rectal artery (branch of IMA), anastomosing branches from the middle rectal artery

Question 9

Describe the arterial supply of the lower 1/3 of the anal canal?

Answer 9

Inferior rectal artery (branch of internal pudendal artery). Anastomosing branches from middle rectal artery

Question 10

Describe the venous drainage of the upper 2/3 of the anal canal?

Answer 10

Superior rectal vein which empties into inferior mesenteric vein (portal venous system)

Question 11

Describe the venous drainage of the lower 1/3 of the anal canal?

Answer 11

Inferior rectal vein which empties into internal pudendal vein (systemic venous system)

Question 12

Describe the lymphatic drainage of the upper 2/3 of the anal canal?

Answer 12

Internal iliac lymph nodes

Question 13

Describe the lymphatic drainage of the lower 1/3 of the anal canal?

Answer 13

Superficial inguinal lymph nodes

Question 14

Describe the nerve supply of the upper 2/3 of the anal canal?

Answer 14

Visceral innervation via the inferior hypogastric plexus. Sensitive to stretch.

Question 15

Describe the nerve supply of the lower 1/3 of the anal canal?

Answer 15

Somatic innervation via the inferior rectal nerves (branches of the pudendal nerves). Sensitive to pain, temperature, touch and pressure.

Question 16

What is the mucosa of the upper anal canal arranged into?

Answer 16

Longitudinal folds called anal columns

Question 17

What are the inferior ends of the anal columns linked by?

Answer 17

Ridges called anal valves

Question 18

What is the pectinate line formed by?

Answer 18

The ring formed by the anal valves is termed the pectinate line

Question 19

What does the pectinate line mark?

Answer 19

marks the approximate boundary between the embryologically different regions of the anal canal

Question 20

What surrounds the anal canal?

Answer 20

internal and external anal sphincters

Question 21

Describe the internal anal sphincter

Answer 21

around the upper two-thirds of the canal, is the thickened lower end of the circular smooth muscle of the rectum.

Question 22

Describe the external anal sphincter

Answer 22

striated muscle surrounds the lower two-thirds of the canal. It comprises subcutaneous, superficial and deep parts

Question 23

What type of muscle is the internal anal sphincter?

Answer 23

Circular smooth

Question 24

What type of muscle is the external anal sphincter?

Answer 24

Striated

Question 25

What is the deep part of the external anal sphincter closely related to?

Answer 25

related posteriorly to the fibres of puborectalis

Question 26

What is the nerve supply to the internal anal sphincter?

Answer 26

Autonomic --> Visceral innervation via the inferior hypogastric plexus.

Question 27

What is the nerve supply to the external anal sphincter?

Answer 27

Somatic --> via the inferior rectal nerves (branches of the pudendal nerves).

Question 28

What are haemorrhoids?

Answer 28

swellings containing enlarged blood vessels that are found inside or around the bottom

Question 29

What are ischioanal fossae?

Answer 29

These are wedge shaped spaces in the lateral parts of the anal triangle. They unite posteriorly, behind the anal canal, and anteriorly they extend into the urogenital triangle, above the urogenital diaphragm

Question 30

The ischioanal fossae are largely filled with fat and are a common site for infection. What can this result in?

Answer 30

Abscesses which may rupture to produce a fistula between the anal canal and ischioanal fossae

Question 31

Where do the internal pudendal vessels and nerve travel as they supply the perineum? What branches come off as the structures traverse the ischioanal fossa?

Answer 31

In the pudendal canal in the lateral wall of each ischioanal fossa as they pass anteriorly to supply the structures of the perineum. Inferior rectal artery, nerve and vein

Question 32

How and why would you carry out a pudendal nerve block?

Answer 32

To anaesthetise the perineum – childbirth during an episiotomy.

Question 33

What is the UG triangle in males and females subdivided into and by what?

Answer 33

Into deep and superficial parts by the urogenital diaphragm

Question 34

What is the urogenital diaphragm?

Answer 34

a triangular layer of muscle and dense fascia that extends between the inferior ischiopubic rami and merges with the perineal body posteriorly.

Question 35

What is the fascial component of the urogenital diaphragm called?

Answer 35

The perineal membrane

Question 36

What does the UG diaphragm merge with posteriorly?

Answer 36

Perineal body

Question 37

How are the external urethral sphincters formed?

Answer 37

By muscles within the UG diaphragm (deep pouch)

Question 38

What is the deep artery of the clitoris/penis a branch of?

Answer 38

Internal pudendal artery

Question 39

What is the dorsal artery of the penis/clitoris a branch of?

Answer 39

Internal pudendal artery

Question 40

Describe full course of internal pudendal artery

Answer 40

It pierces the parietal pelvic fascia to exit the pelvis. It passes through the greater sciatic foramen inferior to the piriformis muscle to enter the gluteal region. It then curves around the ischial spine and sacrospinous ligament to re-enter the pelvis by passing through the lesser sciatic foramen. It then re-exits the pelvis through the pudendal canal with the internal pudendal veins and the pudendal nerve. It then runs in the lateral wall of the ischioanal fossa and the perineal region.

Question 41

What are the branches of the internal pudendal artery?

Answer 41

inferior rectal artery, deep artery of the penis/clitoris, dorsal artery of the penis/clitoris, perineal artery, posterior scrotal/labial artery, transverse perineal artery, artery to the bulb

Question 42

What does the deep artery of the penis/clitoris supply?

Answer 42

Corpus cavernosum

Question 43

What is the nerve supply to the external urethral sphincter?

Answer 43

Deep perineal branch of pudendal nerve

Question 44

Which vessel does external pudendal artery branch off? What does it supply?

Answer 44

Femoral artery Skin of scrotum and labia

Question 45

What are the branches of the internal pudendal artery?

Answer 45

Inferior rectal artery, perineal artery, posterior scrotal/labial artery, artery to bulb, deep artery of penis/clitoris, dorsal artery of penis/clitoris

Question 46

What does the superficial perineal pouch in males contain?

Answer 46

Testis, vas, root of penis

Question 47

What would a why rupture of the urethra in the bulb of the penis lead to?

Answer 47

Swelling of scrotum, penis and lower abdominal wall

Question 48

Which structures do the bulb of the penis and the crura of the corpora cavernosa attach to?

Answer 48

Perineal membrane and ischiopubic ramus

Question 49

What are the actions of bulbospongiosus and ischiocavernosus muscles? What is their nerve supply?

Answer 49

Contraction of these muscle prevents venous return, thereby allowing engorgement of the erectile tissues. Deep branch of perineal nerve

Question 50

What is the sensory nerve supply to the skin of the scrotum?

Answer 50

Ilioinguinal nerves, genital branch of genitofemoral nerves = anterior Branches of pudendal nerve, posterior scrotal nerve = posterior

Question 51

From what is the tunica vaginalis derived? How?

Answer 51

Processus vaginalis During descent of the testis, the testis pushes through a serous pouch of the peritoneum

Question 52

What is the cremasteric reflex?

Answer 52

a superficial reflex found in human males that is elicited when the inner part of the thigh is stroked. Stroking of the skin causes the cremaster muscle to contract and pull up the ipsilateral testicle toward the inguinal canal.

Question 53

What lies deep to the skin and fat of the labia majora?

Answer 53

a mass of erectile tissue called the bulb of the vestibule

Question 54

What is the bulb of vestibule attached to?

Answer 54

Perineal membrane

Question 55

What do the bulbs of vestibule partially overlie?

Answer 55

the greater vestibular glands

Question 56

What are the bulbs of vestibule covered by?

Answer 56

Bulbospongiosus muscles

Question 57

Where do the bulbs of vestibule join? What does this form?

Answer 57

Join anterior to the external opening of the urethra and pass forwards to form the glans of the clitoris

Question 58

Two other masses of erectile tissue also contribute to the formation of the clitoris. What name is given to these masses?

Answer 58

Corpora cavernosa

Question 59

Which part of the clitoris do the corpora cavernosa form?

Answer 59

Body and contribute to glans

Question 60

How is the clitoris anchored in the perineum?

Answer 60

Via crus which insert onto the ischiopubic ramus

Question 61

What is the function of the vestibular glands (also known as Bartholin’s glands)?

Answer 61

Secretion of mucus in to the vaginal during sexual arousal.

Question 62

What forms during infection of vestibular glands?

Answer 62

a Bartholin’s cyst

Question 63

To which nodes does lymph from perineal structures drain?

Answer 63

Superficial inguinal lymph nodes, the deep and then internal iliac.