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Gastrointestinal > Rectum + Anal Canal > Flashcards

Rectum + Anal Canal Flashcards

1
Q

Describe the rectum

A
  • 12-15cm long
  • passes through pelvic floor
  • continuous band of outer longitudinal muscles (unlike taeniae coli of rest of colon)
  • cured shape anterior to sacrum
  • temporary storage for faeces
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2
Q

What stimulates the urge to defaecate?

A

Stretching of rectum

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3
Q

Function of rectum

A

Temporary storage of faeces prior to defaecation

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4
Q

Blood supply to the rectum

A

Superior rectal artery
Middle rectal artery
Inferior rectal artery

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5
Q

What does the continuous longitudinal muscles of the rectum aid?

A

Distension + contraction of the rectum before defecation

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6
Q

What is the middle rectal artery a branch of?

A

Internal iliac

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7
Q

What is the inferior rectal artery a branch of?

A

Pudendal artery

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8
Q

Venous drainage of the rectum

A

Portal drainage - superior rectal vein
Systemic drainage - internal iliac vein

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9
Q

Where is the start of the anal canal?

A

Proximal border of the anal sphincter complex

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10
Q

What is the puborectalis sling?

A

puborectalis muscle forms a sling around the lower rectum when it meets the fibers from the opposite side

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11
Q

Function of the puborectal sling

A

Maintains faecal continence by angling the anal canal posteriorly

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12
Q

What are the parts of the anal sphincter complex?

A

Internal involuntary sphincter
External anal sphincter

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13
Q

Factors required for continence

A
  • distensible rectum
  • firm bulky faeces
  • normal anorectal angle
  • anal cushions
  • normal anal sphincters
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14
Q

What is the normal anorectal angle?

A

Rectum points anteriorly
Anal canal points posterity

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15
Q

Describe the internal involntary sphincter of the anal sphincter complex

A
  • thickening of circular smooth muscle
  • under autonomical control
  • 80% of resting anal pressure
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16
Q

Describe the external anal sphincter?

A
  • striated muscle
  • under conscious control + allows for voluntary control of defaecation
  • innervated by pudenal nerve
  • 20% of resting anal pressure
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17
Q

Nerve supply to the external anal sphincter

A

Pudendal nerve

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18
Q

How much the parts of the anal sphincter complex contribute to resting anal pressure?

A

Internal involuntary sphincter 80%
External anal sphincter 20%

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19
Q

What is the defecation reflex?

A
  • stimulus: distension in rectum
  • response: contraction in rectum + sigmoid colon, relaxation of internal anal sphincter + contraction of external anal sphincter
20
Q

What happens to the anal sphincter complex during defecation reflex?

A

Relaxation of internal anal sphincter
Contraction of external anal sphincter

21
Q

What happens in defecation?

A
  • relaxation of external anal sphincter
  • relaxation of puborectalis muscle
  • forward peristalsis in rectum + sigmoid colon
  • Valsalva maneuver: increased abdominal pressure
22
Q

What is valsalva maneuver?

A
  • Forced expiation against a closed glottis
  • Increases abdominal pressure
  • Helps for defecation
23
Q

What is the dentate/pectinate line?

A

Junction of hindgut and proctodaeum (ectoderm)

24
Q

Epithelium above and below pectinate line

A

Above: columnar epithelium
Below: stratified squamous epithelia

25
Q

Pain receptors above and below pectinate line

A

Above: visceral pain receptors
Below: somatic pain receptors

26
Q

What are haemorrhoids?

A

Abnormal (symptomatic) anal cushions

27
Q

What are anal cushions?

A

3+ areas of tissues divided from a complex of venous plexus in the anus

28
Q

Two classifications of haemorrhoids

A

Internal (most common)
External

29
Q

Describe internal haemorrhoids

A
  • caused by loss of connective tissue support
  • above pectinate line
  • painless
  • enlarge and prolapse through anal canal
  • bleed bright red blood + itchy skin
30
Q

Treatment of internal haemorrhoids

A
  • increased hydration
  • high fibre diet
  • avoid straining
  • rubber band ligation (tie around base > fall off)
  • surgery if grade 4
31
Q

What are the grades of internal haemorrhoids?

A
  • Grade 1: no prolapse, prominent blood vessles
  • Gade 2-4: increasing degrees of prolapse
32
Q

Describe external haemorrhoids

A
  • below pectinate line
  • painful
33
Q

Treatment of external haemorrhoids

A

Surgical removal

34
Q

What is an anal fissure

A

Linear tear in anoderm
(epithelial lining of anal canal)

35
Q

Presentation of an anal fissure

A
  • pain of defecation (passing glass/razor blades)
  • haematochezia
  • passing of hard stool
36
Q

Treatment of anal fissure

A
  • hydration
  • dietary fibre
  • analgesia
  • warm baths
  • medications to relax internal anal sphincter
37
Q

Cause of anal fissure

A

High internal anal sphincter tone
Reduced blood flow to anal mucosa

38
Q

What does haematochezia indicate?

A

Lower GI bleeding

39
Q

Causes of haematochezia

A
  • diverticulitis
  • ulcerative colitis
  • colorectal cancer
  • anorectal disease: haemorrhoids, anal fissure
  • angiodysplasia
40
Q

What is angiodysplasia?

A

Small vascular malformation in bowel wall

41
Q

What is melaena?

A

Black tarry offensive smelling stool
Due to upper GI bleed > haemoglobin being altered by digestive enzymes + gut bacteria

42
Q

Causes of melaena

A

Upper GI bleed
- peptic ulcer disease
- variceal bleeds
- upper GI malignancy
- oesophageal/gastric cance

43
Q

What does the term ‘mass movement’ describe?

A

The rapid movement of colonic content

44
Q

Why are internal haemorrhoids initially painless?

A

They arise from above the dentate line in the anal canal

45
Q

A patient complains that it feels like they are passing razor blades when they defacate, what is a likely diagnosis?

A

Anal fissure

Gastrointestinal (28 decks)

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