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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
Pain receptors above and below pectinate line
Above: **visceral pain receptors** Below: **somatic pain receptors**
26
What are haemorrhoids?
Abnormal (symptomatic) anal cushions
27
What are anal cushions?
3+ areas of tissues divided from a complex of venous plexus in the anus
28
Two classifications of haemorrhoids
Internal (most common) External
29
Describe internal haemorrhoids
- caused by loss of connective tissue support - above pectinate line - painless - enlarge and prolapse through anal canal - bleed bright red blood + itchy skin
30
Treatment of internal haemorrhoids
- increased hydration - high fibre diet - avoid straining - rubber band ligation (tie around base > fall off) - surgery if grade 4
31
What are the grades of internal haemorrhoids?
- **Grade 1**: no prolapse, prominent blood vessles - **Gade 2-4**: increasing degrees of prolapse
32
Describe external haemorrhoids
- below pectinate line - painful
33
Treatment of external haemorrhoids
Surgical removal
34
What is an anal fissure
Linear tear in anoderm (epithelial lining of anal canal)
35
Presentation of an anal fissure
- pain of defecation (passing glass/razor blades) - haematochezia - passing of hard stool
36
Treatment of anal fissure
- hydration - dietary fibre - analgesia - warm baths - medications to relax internal anal sphincter
37
Cause of anal fissure
High internal anal sphincter tone Reduced blood flow to anal mucosa
38
What does haematochezia indicate?
Lower GI bleeding
39
Causes of haematochezia
- diverticulitis - ulcerative colitis - colorectal cancer - anorectal disease: haemorrhoids, anal fissure - angiodysplasia
40
What is angiodysplasia?
Small vascular malformation in bowel wall
41
What is melaena?
**Black tarry offensive smelling stool** Due to upper GI bleed > haemoglobin being altered by digestive enzymes + gut bacteria
42
Causes of melaena
**Upper GI bleed** - peptic ulcer disease - variceal bleeds - upper GI malignancy - oesophageal/gastric cance
43
What does the term ‘mass movement’ describe?
The rapid movement of colonic content
44
Why are internal haemorrhoids initially painless?
They arise from above the dentate line in the anal canal
45
A patient complains that it feels like they are passing razor blades when they defacate, what is a likely diagnosis?
Anal fissure

Gastrointestinal (33 decks)

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