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Colorectal > Ch.1 - Anatomy > Flashcards

Ch.1 - Anatomy Flashcards

1
Q

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?
A
  • 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
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2
Q

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?

A

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

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3
Q

How long and thick is the internal sphincter?

A

2mm in thickness

35mm in length

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4
Q

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?

A

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

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5
Q

What innervates the external anal sphincter?

A

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

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6
Q

The perineal body represents the intersection of what muscles?

A

External anal sphincter

Superficial and deep transverse perinei

Bulbospongiosus

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7
Q

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

A

Ileococcygeus
Punococcygeus
Puborectalis

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8
Q

What innervates the levator Ani?

A

Pudendal nerve branches. S3-S4

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9
Q

Anorectal ring is composed of what things?

A

Upper border of the internal anal sphincter + puborectalis muscle

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10
Q

What is the most important factor for gross fecal continence?

A

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

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11
Q

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

A

Pubococcygeus muscle

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12
Q

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

A

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

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13
Q

How do you distinguish sigmoid colon vs upper rectum?

A

Absence of taenia coli and epiploic appendages

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14
Q

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

A

Posterior to retrosacral fascia

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15
Q

Where is denonvillier’s fascia in men and women?

A

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

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16
Q

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

A

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

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17
Q

Which anorectal space is the largest?

A

Ischioanal/ischiorectal space

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18
Q

What are the borders of the ischioanal/ischiorectal space?

A

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

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19
Q

What are the contents of ischioanal/ischiorectal space?

A

Pudendal nerve branches

Superficial branches of the internal pudendal vessels

20
Q

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

A

Through the deep postanal soace

21
Q

Which anorectal space is intraperitoneal?

A

Supralevator space

22
Q

What are the boundaries of the supralevator space?

A

Medial: rectum

Lateral: pelvic wall

Inferior: levator

23
Q

Which anorectal space allows for horseshoe abscess?

A

Deep postanal space

24
Q

Deep vs. superficial postanal space

  • what separates these two?
A

Both are below levator Ani and posterior to anus

Deep postanal space: above the anococcygeal ligament

Superficial postanal space: below the anococcygeal ligament

25
Q

At what point does IMA become superior rectal artery?

Middle rectal artery originates from what?

Inferior rectal artery originates from what?

A

As the IMA crosses the left common iliac artery

Middle rectal from internal iliac

Inferior rectal from internal pudendal

26
Q

What innervates the internal anal sphincters?

A

Sympathetic L5

Parasympathetic S2-S4

27
Q

Superior rectal artery is a continuation of what artery?

After what anatomic landmark does this artery become superior rectal?

A

continuation of IMA.

After crossing the left iliac vessels

28
Q

What is the whole “lateral ligament debate?”

A

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

29
Q

What is the venous drainage of the rectum?

A

Superior rectal vein -> drains the rectum + upper anal canal into the portal system

Middle and inferior rectal vein -> systemic via internal iliac vein

30
Q

What is the lymphatic drainage of the rectum?

What about anal canal?

A

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

31
Q

Sympathetic fibers from what nerve roots innervate the rectum?

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

A

Sympathetic: L1, L2, L3

Parasympathetic: S2-S4

32
Q

What innervates the external anal sphincters?

A

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

33
Q

Which nerve mediates the anal sensation?

A

Inferior rectal branch of the pudendal nerve

34
Q

What is the generally accepted overall length of the colon?

A

150cm

35
Q

Which part of the colon is generally the longest?

A

Transverse. 45-50cm

36
Q

Which part of the colon is the narrowest?

A

Rectosigmoid junction. 2-2.5cm in diameter

37
Q

Which area represents the border of embryonic midgut and hindgut?

A

Splenic flexure.

38
Q

Does middle colic branch early or late?

What does it supply?

What does middle colic originate from?

A

Branches early

Transverse colon

Middle colic originates from the SMA

39
Q

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?

A

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

40
Q

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

A

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

41
Q

Foregut and midgut separate at what anatomic structure?

A

Pancreatic papilla

42
Q

Embryologic guy development. Explain the three stages and time course

A

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

43
Q

What is Littre’s hernia?

A

Indirect hernia containing meckel’s

44
Q

Hirschsprung disease is more common in males or females?

Does it involve the anal sphincters?

A

Males.

Internal sphincter is always involved

45
Q

How common is anal stenosis?

What % of children with anal stenosis are symptomatic?

When to do treatment?

A

25-40% of all infants

Only 25% of them are symptomatic

Dilation in the first 3-6mo of life

Colorectal (22 decks)

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