Ch.1 - Anatomy

Question 1

Surgical anal canal

• what are the borders?
• who has longer anal canal? Male or female?
• what is the tube within a tube model of the muscular anal canal?

Answer 1

• borders: anal verge (internal/external sphincters) to anorectal ring (puborectalis)
• males have longer anal canal
• two tubes. Outer tube: somatic muscles. Puborectalis and external sphincter
  Inner tube: visceral smooth muscle. Internal sphincter and the longitudinal layer innervates by autonomic nervous system

Question 2

What is ATZ? Where does it begin?

Dentate line marks the true division between what two embryologic layers?

How are the blood vessel/nerve supply/drainage different for parts proximal to the dentate vs. Distal to dentate?

Answer 2

Anal transition zone. 6-12mm proximal to the dentate line.

Dentate line: division between endoderm and ectoderm

Proximal to the dentate: hypogastric (internal iliac). Parasympathetic
Distal to the dentate: inferior henorrhoidal. Somatic nerves

Question 3

How long and thick is the internal sphincter?

Answer 3

2mm in thickness

35mm in length

Question 4

What are the three compartments of external anal sphincter. Even though really it’s one continuous muscle

The superficial EAS attached to what bone via what ligament?

Answer 4

Deep: most superior part of the EAS. Continuous with puborectalis and levator ani
Superficial: middle
Subcu: distal

Middle attached to the coccyx via the anococcygeal ligament
Subcu

Question 5

What innervates the external anal sphincter?

Answer 5

Inferior rectal branch of the pudendal nerve (S2-S3) and by the perineal branch of S4

Question 6

The perineal body represents the intersection of what muscles?

Answer 6

External anal sphincter

Superficial and deep transverse perinei

Bulbospongiosus

Question 7

What are the three subdivisions of levator Ani from proximal to distal?

Answer 7

Ileococcygeus
Punococcygeus
Puborectalis

Question 8

What innervates the levator Ani?

Answer 8

Pudendal nerve branches. S3-S4

Question 9

Anorectal ring is composed of what things?

Answer 9

Upper border of the internal anal sphincter + puborectalis muscle

Question 10

What is the most important factor for gross fecal continence?

Answer 10

Contraction of the puborectalis muscle causes a horizontal force that closes the pelvic diaphragm

Question 11

Which muscle of the levator is usually injured during traumatic vaginal delivery?

Answer 11

Pubococcygeus muscle

Question 12

From the anal verge, how many cm are lower, middle, and upper rectum?

Answer 12

Lower: 0-7cm
Middle 7-12cm
Upper: 12-15cm

Question 13

How do you distinguish sigmoid colon vs upper rectum?

Answer 13

Absence of taenia coli and epiploic appendages

Question 14

Supralevator or retrorectal space refers to space posterior to what structure.

Answer 14

Posterior to retrosacral fascia

Question 15

Where is denonvillier’s fascia in men and women?

Answer 15

Men: fascia between rectum and seminal vesicles
Women: rectovaginal septum, or rectovaginal fascia

Question 16

Rectocele represents a defect in [this layer] which allows rectum to bulge anteriorly

Answer 16

Rectocele: defect in rectovaginal septum/fascia or denonvillier’s fascia.

Question 17

Which anorectal space is the largest?

Answer 17

Ischioanal/ischiorectal space

Question 18

What are the borders of the ischioanal/ischiorectal space?

Answer 18

Lateral: obturator internus muscle/obturator fascia

Medial: levator Ani muscle

Posterior: lower border of the gluteus maximus and the sacrotuberous ligament

Anterior: deep and superficial transverse perinei

Caudal boundary: skin of the perineum

Question 19

What are the contents of ischioanal/ischiorectal space?

Answer 19

Pudendal nerve branches

Superficial branches of the internal pudendal vessels

Question 20

The left and the right ischiorectal space communicate through what space?

Answer 20

Through the deep postanal soace

Question 21

Which anorectal space is intraperitoneal?

Answer 21

Supralevator space

Question 22

What are the boundaries of the supralevator space?

Answer 22

Medial: rectum

Lateral: pelvic wall

Inferior: levator

Question 23

Which anorectal space allows for horseshoe abscess?

Answer 23

Deep postanal space

Question 24

Deep vs. superficial postanal space

• what separates these two?

Answer 24

Both are below levator Ani and posterior to anus

Deep postanal space: above the anococcygeal ligament

Superficial postanal space: below the anococcygeal ligament

Question 25

At what point does IMA become superior rectal artery? Middle rectal artery originates from what? Inferior rectal artery originates from what?

Answer 25

As the IMA crosses the left common iliac artery Middle rectal from internal iliac Inferior rectal from internal pudendal

Question 26

What innervates the internal anal sphincters?

Answer 26

Sympathetic L5 | Parasympathetic S2-S4

Question 27

Superior rectal artery is a continuation of what artery? After what anatomic landmark does this artery become superior rectal?

Answer 27

continuation of IMA. After crossing the left iliac vessels

Question 28

What is the whole "lateral ligament debate?"

Answer 28

The debate is: 1) does it actually exist? Well yes 2) what do they contain? Initially middle rectal artery was thought to be in this. But it actually runs posterior to the lateral ligament and the nervi recti fibers (which originate from the inferior hypogastric plexus) course transversely under the lateral ligament to the rectal wall

Question 29

What is the venous drainage of the rectum?

Answer 29

Superior rectal vein -> drains the rectum + upper anal canal into the portal system Middle and inferior rectal vein -> systemic via internal iliac vein

Question 30

What is the lymphatic drainage of the rectum? What about anal canal?

Answer 30

Upper 2/3 -> inferior mesenteric nodes -> para-aortic lymph nodes Lower 1/3 -> along the superior rectal artery and laterally along the middle rectal -> internal iliac lymph nodes Anal canal above the dentate -> inferior mesenteric and internal iliac Anal canal below the dentate -> along the inferior rectal lymphatics -> superficial inguinal nodes

Question 31

Sympathetic fibers from what nerve roots innervate the rectum? Parasympathetic fibers from what nerve roots innervate the rectum and anal canal?

Answer 31

Sympathetic: L1, L2, L3 Parasympathetic: S2-S4

Question 32

What innervates the external anal sphincters?

Answer 32

Inferior rectal branch of the internal pudendal nerve (S2, S3) And by the perineal branch of S4

Question 33

Which nerve mediates the anal sensation?

Answer 33

Inferior rectal branch of the pudendal nerve

Question 34

What is the generally accepted overall length of the colon?

Answer 34

150cm

Question 35

Which part of the colon is generally the longest?

Answer 35

Transverse. 45-50cm

Question 36

Which part of the colon is the narrowest?

Answer 36

Rectosigmoid junction. 2-2.5cm in diameter

Question 37

Which area represents the border of embryonic midgut and hindgut?

Answer 37

Splenic flexure.

Question 38

Does middle colic branch early or late? What does it supply? What does middle colic originate from?

Answer 38

Branches early Transverse colon Middle colic originates from the SMA

Question 39

The true right colic artery is present in what % of the time? When present typically arises from what? But can rise from what? Middle colic arises where?

Answer 39

80%. Absent up to 20% of the time From SMA typically but alternatively from ileocolic or middle colicmiddle colic rises from the SMA near the inferior border of the pancreas

Question 40

Marginal artery of drummond can be absent at the splenic flexure in what % of the time?

Answer 40

Up to 50% of the time. Griffith's point

Question 41

Foregut and midgut separate at what anatomic structure?

Answer 41

Pancreatic papilla

Question 42

Embryologic guy development. Explain the three stages and time course

Answer 42

Stage I: physiologic herniation. Between 6-8 wks Stage II: return to the abdomen during 10th wk. Guts move back in, counterclock fashion 180 degrees Stage III: Fixation of midgut 12-13wks. Results in duodenum, right and left colon sticking to retroperitoneum

Question 43

What is Littre's hernia?

Answer 43

Indirect hernia containing meckel's

Question 44

Hirschsprung disease is more common in males or females? Does it involve the anal sphincters?

Answer 44

Males. Internal sphincter is always involved

Question 45

How common is anal stenosis? What % of children with anal stenosis are symptomatic? When to do treatment?

Answer 45

25-40% of all infants Only 25% of them are symptomatic Dilation in the first 3-6mo of life