Rectum and Anal Canal Flashcards

1
Q

Describe the location of the rectum

A
  • starts at rectosigmoid junction at level S3
  • follows curve of sacrum and coccyx
  • ends in front of the tip of the coccyx by piercing the pelvic diaphragm and becoming continuous with anal canal
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2
Q

Is the rectum peritoneal?

A
  • upper 1/3: covered in peritoneum anteriorly and laterally in C shape
  • middle 1/3: only covered anteriorly
  • lower 1/3: no peritoneal covering
  • peritoneum reflects off of the surfaces it covers to form pouches/fossae
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3
Q

What do the lateral reflections of peritoneum off of the rectum form?

A
  • pararectal fossa
  • lateral curvatures coinciding with rectal folds or valves internally
  • important for maintenance of continence
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4
Q

How can you distinguish the rectum from the large intestines?

A

lacks taenia, haustra or epiploic appendices

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5
Q

How are the lateral flexures of the rectum formed?

A
  • by 3 transverse rectal folds
  • forms the 3 lateral flexures:
  • superior and inferior on left side
  • intermediate on right side
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6
Q

Where is the perineal flexure/anorectal angle and how is it formed?

A
  • it is the junction between the rectum and anal canal
  • caused by anterior pull of the rectum by the puborectal muscle
  • muscle is important in maintenance of continence by preventing leakage of poop into anus
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7
Q

Describe the anatomical relations of the rectum in males

A

Posterior:

  • S3-5, coccyx and anococcygeal ligament
  • pelvic plexus
  • rectosacral fascia
  • median sacral artery

Anterior:

  • rectovesical pouch
  • bladder
  • prostate and fascia

Lateral:

  • pararectal fossae
  • pudendal plexus
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8
Q

Describe the anatomical relations of the rectum in females

A

Posterior:

  • S3-5, coccyx and anococcygeal ligament
  • pelvic plexus
  • rectosacral fascia

Lateral:

  • pararectal fossae
  • pudendal plexus

Anterior:

  • rectourterine pouch
  • vagina
  • rectovaginal fascia
  • bladder (most anterior)
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9
Q

What makes up the anorectal ring, where is it located and what is its purpose?

A
  • puborectalis sling
  • upper portions of internal and external sphincters
  • located at the junction of the anal canal and rectum
  • it stays tonically contracted throughout the day to prevent leakage of faeces into the anus/anal canal
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10
Q

Expand on the internal anal sphincter

A
  • smooth muscle
  • autonomic
  • derived from circular muscular layer
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11
Q

Expand on the external anal sphincter

A
  • striated muscle
  • one functional unit with deep, superficial and subcutaneous parts
  • fuses with puborectalis
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12
Q

Describe the anatomy of the anal columns

A
  • anal canal has longitudinal folds called anal columns in upper parts
    (house branches of superior rectal vein, artery, lymphatics and nerves)
  • unite at the bottom to form anal valves
  • superior to each valve is an anal sinus (depression)
    (location of mucous glands that lubricate faeces)
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13
Q

Describe the anatomical importance of the pectinate/dentate line

A
  • where the anal valves in the anal canal form a circle
  • above it is the haemorrhoidal zone
  • below is a transition zone called the anal pecten
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14
Q

What is the arterial supply of the rectum and anal canal?

A
  • superior 1/3: superior rectal artery (from IMA)
  • middle 1/3: middle rectal artery (from internal iliac)
  • below anorectal line: inferior rectal artery (from internal pudendal)
  • superior rectal artery
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15
Q

Describe how and where you could see the anal cushions

A
  • patient sitting at an angle with legs spread
  • 3 anal cushions:
  • 11 o’clock
  • 7 o’clock
  • 3 o’clock
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16
Q

Describe the pathology you can have in the anal cushions

A
  • haemorrhoids
  • dilated veins affecting the submucosal plexus in the rectum/anal canal
  • can be internal (above dentate line)
  • can be external (below dentate line)
17
Q

Describe the venous drainage of the rectum and anal canal

A
  • superior 1/3: superior rectal vein to inferior mesenteric to hepatic portal vein
  • middle 1/3: middle rectal to internal iliac and internal pudendal veins
  • inferior 1/3: inferior rectal to infernal iliac and internal pudendal veins
18
Q

Describe the lymphatic drainage of the rectum and anal canal

A
  • superior rectum goes to inferior mesenteric nodes
  • inferior rectum and proximal anal canal to internal iliac nodes
  • distal anal canal goes to superficial inguinal nodes
19
Q

Describe how the nerve supply of the rectum and anal canal affects the presentation of hemorrhoids

A
  • because above and below the dentate line are innervated differently and have different sensations internal and external haemorrhoids will present differently
  • internal will have little to no pain and just feel difficulty in defacating or feeling like they have something to pass, can undergo procedures easily
  • external will have a lot of pain and will not be able to go through procedures without pain or LA
20
Q

Describe the nerve supply of the rectum and anal canal

A
  • parasympathetics S2-4 pelvic splanchnic nerves to pelvic plexus
    (increase peristalsis, relax anal sphincter, visceral senses)
  • upper rectum
  • sympathetics from L1-3 by lumbar splanchnic nerves
  • somatic nerves from S2-4 pudendal nerve
  • below rectum
    (external anal sphincter and pelvic floor muscles)
21
Q

Summarise ways the body maintains faecal continence

A
  • rectosigmoid angle acts as functional sphincter
  • levator ani and puborectalis make angle more acute
  • anal canal sensation can allow cortex to distinguish between gas, fluid and solid and the stretch receptors can adjust to only allow gas out
  • rectal pressure will increase until it forces contents into anal canal but defacation prevented by cortical inhibition and external anal sphincter forces it back into rectum
22
Q

Describe the conditions which allow for defacation

A
  • cortical inhibition released
  • abdo pressure increased
  • puborectalis relaxes allowing rectoanal angle to straighten and external anal sphincter to relax (S2-4)
  • lower colon and rectum contract and internal anal sphincter relaxes