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MD3002 Week 9 > 4. Rectum and Anal Canal > Flashcards

4. Rectum and Anal Canal Flashcards

1
Q

Muscles layers of the rectal wall?

A

Complete longitudinal (instead of taenia coli) and circular muscle layers

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2
Q

The lower dilation of the rectum is called the…

A

Rectal ampulla

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3
Q

What are the rectal concavities

A

Curvatures on the lateral surface of the rectum. Forms left, right, left rectal folds/valves that are seen internally
The middle one on the RHS is more pronounced.

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4
Q

What are pararectal fossa?

A

Invaginations of peritoneum on either side of the rectum

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5
Q

Where is the first rectal concavity? Why?

A

On the left and the sigmoid leads to the rectum from the left

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6
Q

Presence of peritoneum on the rectum?

A

Upper 1/3: Front and sides
Middle 1/3: Front only
Lower 1/3: None

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7
Q

Rectum anterior relations

A

Anterior:
Pouch of douglas (Recto-uterine pouch)
Female: Uterus, cervix, vagina, RV rectum
Male: Denonvillier’s fascia (aka recto-vesical pouch), bladder, prostate, urethra, seminal vesicle

Posterior:
Mesorectum
Anococcygeal ligament

Inferior:
Pelvic floor

Lateral:

  • Urogenital nerves e.g. pelvic plexus, obturator nerve, pelvic splanchnics
  • Ureter
  • Urogenital vessels e.g. Superior vesical artery, inferior vesical artery, internal pudendal artery
  • Vas deferens
  • Prostate palpable in PR
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8
Q

What is the mesorectum?

A 
Location: Posteriorly between reflecting peritoneum, behind rectum
Contains:
-Superior rectal artery and vein
-Lymph nodes 
-Nerves
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9
Q

What is the change of innervation at the pectinate line in the anal canal?

A

Embryological and afferent nerve supply changes.

Sensitive to pain below the line

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10
Q

Where is the recto-anal junction?

A

At the pelvic floor: At the puborectalis and behind the perineal body

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11
Q

Changes in epithelium in anal canal?

A

Columnar –> stratified squamous –> Skin

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12
Q

Features of the internal sphincter?

A

Smooth muscle
Autonomic
Derived from circular muscle layer
Ends at intersphincteric groove

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13
Q

Muscle of external sphincter? Parts?

A

Striated muscle

Deep, superficial and subcutaneous parts (operates as one functional unit though)

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14
Q

Anatomical position of puborectalis?

A

Part of levator ani
Forms a sling from both pubis’ around the anorectal junction.
This draws it forward anteriorly.
**Important addition to recto-anal continence.

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15
Q

How is the anococcygeal ligament formed?

A

By fused levator ani

Then attached the anal canal to the coccyx

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16
Q

What does the external anal sphincter fuse to in the female?

A

Puborectalis
Trans. perinei
Anococcygeal ligament
Perineal body

17
Q

Name the internal features of the anal canal?

A 
Anal columns
Valves 
Pectinate line
Anal cushions at 3, 7, 11 o'clock
Anal sinuses
Glands
18
Q

What supplies the anal columns?

A

Terminal branches of superior rectal artery and vein

19
Q

Clinical relevance of the rick underlying vasculature of the anal canal?

A

Haemorrhoids

Piles

20
Q

Role of anal cushions and internal sphincter?

A

Maintains anal closure when there is no pressure or content from the rectum

21
Q

Which arteries supply the rectum and anal canal?

A

There is free anastomosis of recto-anal arteries especially the superior and inferior rectal arteries
1. SUPERIOR RECTAL from Inferior Mesenteric
2. MIDDLE RECTAL from the internal iliac
3. INFERIOR RECTAL from internal pudendal
There may be a contribution from the median sacral that may cause bleeding during surgery.

22
Q

Venous drainage of the rectum/anal canal?

A

Mirror the arteries
Also form external and internal (submucosal) venous plexuses port-systemic anastomosis
1. SUPERIOR RECTAL VEINS to inferior mesenteric to portal vein
2. MIDDLE AND INFERIOR RECTAL VEINS to internal iliac veins (systemic)

23
Q

Lymph drainage of the rectum/anal canal?

A

Inferior mesenteric nodes for SUPERIOR RECTUM

Internal iliac nodes for LOWER RECTUM and PROXIMAL ANAL CANAL

Superficial inguinal nodes for DISTAL ANAL CANAL

24
Q

Recto-anal nerve supply:
Parasympathetic?
Sympathetic?
Somatic?

A

PS:
Pelvic splanchnics (S2,3,4) to pelvic plexus
Symp:
Lumbar splanchnics
COMBINE to form the pelvic plexuses, to provide:
-Sensation
-Internal sphincter control (symp contracts, p’symp relax)

Somatic: Via pudendal nerve S2,3,4
Gives INFERIOR RECTAL BRANCHES to supply:
-External anal sphincter
-Adjacent pelvic floor muscles (puborectalis)
-Sensation to the distal anal canal

25
Q

Which structures control normal continence?

A

Levator ani and puborectalis = Recto=ana angle more acute
Internal and external sphincters
Abdominal pressure flattens anterior wall of lower rectum over upper anal canal
Anal cushions close the canal

26
Q

How does rectal pressure and detection increase and contents increase, prior to defecation?

A

The rectum can partially fill without an increase in pressure (c.f. bladder); the anal canal sensation (specialised receptors) can allow the cortex to distinguish between gas, fluid, and solid faeces; there are stretch receptors in levator ani and the tissue around the anal canal

Eventually, rectal pressure forces its contents into the anal canal, but defecation is prevented by learned, cortical inhibition; only gas may be allowed to escape; the external sphincter forces faeces back up in to the rectum

27
Q

What are the events that signal defecation?

A
  1. Cortical inhibition is release, via the corticospinal tracts
  2. Abdominal pressure in increased
  3. Puborectalis relaxes, allowing the recto-anal angle to straighten. Whilst external sphincter relaxes (SOMATIC S2,3,4)
  4. The lower colon and rectum contract, whilst the internal relaxes (via PARASYMPATHETIC PELVIC SPLANCHNICS in PELVIC PLEXUS)
28
Q

Causes for incontinence

A

Cortical or cord lesions above S2,3,4
Damage to the external sphincter during obstetric or perineal procedures
Entrapment of the pudendal nerve

29
Q

Changes in innervation, vascular supply and lymph drainage above and below pectinate line?

A

Above pectinate line:

  • Embryological endoderm
  • Autonomic innervation
  • Arteries from IMA
  • Vein to portal circulation
  • Lymph to internal iliac nodes
  • porto-systemic anastomosis*

Below pectinate line:

  • Embryological ectoderm
  • Somatic innervation (i.e. sensitive to pain)
  • Arteries from inferior rectal
  • Veins to inferior rectal
  • Lymph to superficial inguinal nodes
30
Q

What is the urogenital triange between?

A

The pubic symphysis and the ischiopubic rami

Anterior to the ischial tuberosities

31
Q

What is the anal triangle between?

A

Ischial tuberosities, the sacrotuberous ligaments and the coccyx

32
Q

What is the ischio-anal fossa?

A

Fat-filled pyramidial region.
Position: Below levator ani and either side of the anal canal. May communicate with eachother behind the anal canal
Function: Allows distension during defecation

33
Q

Where does the pudendal neurovascular bundle lie?

A

Laterally in Alcock’s canal (obturator fascia)

34
Q

Inferior rectal n.v.b. passes across apex to supply the…

A

external sphincter and anal canal sensation.

35
Q

Inferior border of ischio-anal fossa?

A

Buttock skin and fat

Gluteus maximus

36
Q

What stops bruising and extravastion of urine passing posteriory to the I-A Fossae?

A

The attachment of Colles’, perineal fascia to the perineal body and posterior edge of the perineal membrane

37
Q

Consequence of Dilatation of the venous plexuses ??

A

Giving haemorrhoids or piles

38
Q

What causes ischo-cana abscesses?

A

A sinus from the anal canal

MD3002 Week 9 (10 decks)

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