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GI System > Rectum and Anal Canal > Flashcards

Rectum and Anal Canal Flashcards

1
Q

How long is the rectum?
How is it different to the rest of the colon?
Describe its shape and position relative to Sacrum

A
  • 12-15cm
  • Continuous band of outer longitudinal muscle
  • Curved and anterior to sacrum
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2
Q

Is the Rectum Intra or extraperitoneal?

A

Some parts are Intra, some are Extra

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3
Q

Describe the arterial blood supply to the rectum

A

Superior part;
- Superior rectal artery (from IMA)

Middle part;
- Middle rectal artery (from Internal Iliac)

Inferior part;
- Inferior rectal artery (from Pudendal)

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4
Q

Describe the Venous drainage of the rectum

A
  • Superior parts: Superior rectal vein drains becomes IMV which is part of portal circulation
  • Inferior parts: Drained by Internal Iliac Vein

(Anastamoses exist between SRV and IIV)

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5
Q

What is significant about the Systemic-Portal anastomoses in the Rectum?

A

Can become varies in Portal Hypertension

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6
Q

Where does the anal canal begin?

A

At the proximal border of the anal sphincter complex

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7
Q

The rectum points anteriorly, the anal canal points posteriorly.

What muscle is responsible for this?

What is significant about this?

A
  • Puborectalis

- This is a feature of continence

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8
Q

What are 5 factors that allow the anal canal to be involved in Continence?

A
  • Distensible rectum
  • Firm bulky faeces
  • Normal anorectal angle (Via Puborectalis)
  • Anal cushions
  • Normal anal sphincters
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9
Q

What are the Anal Cushions and their function?

A
  • Network of blood vessels (usually venous)

- Which increase the sphincter mechanism of the anus, when they swell/ blood passes through

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10
Q

What are the 2 parts to the Anal Sphincter Complex?

A
  • Internal sphincter (Involuntary)

- External sphincter (Striated muscle)

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11
Q

Describe the Internal Anal Sphincter

What percentage of resting anal pressure does this contribute to?

A
  • A thickening of circular smooth muscle
  • Under autonomic control

80%, so very important in resting Anal Pressure

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12
Q

Describe the External Anal Sphincter

(20% of resting anal pressure)

What nerve innervates the sphincter?

A

3 components;

  • Superficial
  • Subcutaneous
  • Deep: Demarcates upper anal canal, mixes with fibres from Levator Ani, Joins Puborectalis-rectalis to form sling

Pudendal nerve

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13
Q

List 3 ways the Defecation Reflex leads to Increased pressure in rectum

What stimulates this reflux?

A
  • Contraction in rectum and sigmoid colon
  • Relaxation of Internal Anal Sphincter
  • Contraction of External Anal Sphincter
  • Distension of rectum
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14
Q

Increased pressure in rectum can lead to either DELAY or DEFECATION

List 4 ways it leads to Defecation

A
  • Relaxation of External Anal Sphincter
  • Relaxation of Puborectalis
  • Forward peristalsis in rectum and sigmoid colon
  • Valsalva manoeuvre (Increased ab pressure)
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15
Q

Increased pressure in rectum can lead to either DELAY or DEFECATION

List 3 ways it leads to Delay

A
  • Contraction of External Anal sphincter
  • Contraction of Puborectalis
  • Reverse peristalsis in rectum
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16
Q

The Anal Canal contains the Dentate/ Pectinate line.

What is this?

A

Junction between Hindgut and Proctodeum

17
Q

Compare the pain receptors and epithelia above and below the Dentate/ Pectinate line

A

Above;

  • Visceral pain receptors (So poorly localised, vague pain)
  • Columnar

Below;

  • Somatic pain receptors
  • Strat. Squamous
18
Q

What are Haemorrhoids?

What are the 2 classifications?

A

Symptomatic anal cushions, Internal and External

Internal- most common, above Pectinate line

19
Q

Describe Internal Haemorrhoids in 4 ways

A
  • Relatively painless (Visceral pain receptors)
  • Caused by loss of CT support
  • Enlarge and prolpase through anal canal
  • Bright red blood and Itching
20
Q

How do we treat Internal Haemorrhoids in 4 ways?

A
  • Increased hydration/ high Fibre diet
  • Avoid strain
  • Rubber band ligation (around base, will necrose and fall off)
  • Surgery
21
Q

Describe the 4 grades of Internal Haemorrhoids

A

1: No prolapse, just prominent vessels
2: Prolpase upon bearing down, spontaneous reduction
3: Prolapse upon bearing down, needs manual reduction
4: Prolapse, inability to be manually reduced

22
Q

Describe External Haemorrhoids in 3 ways

A
  • Very painful
  • Tend to thrombose
  • Good outcomes for surgery
23
Q

What is an Anal Fissure?

How does it present?

A

Linear tear in the Anoderm (Strat Squamous part of anal canal lying below Pectinate line)

  • Painful defecation
  • Haematochezia
24
Q

Anal fissures can be caused by passing a hard stool (but also after diarrhoea)

What are 2 possible underlying causes?

A
  • High internal anal sphincter tone

- Reduced blood flow to anal mucosa

25
Q

How do we treat an Anal Fissure in 3 ways?

A
  • Warm baths
  • Medication to relax internal anal sphincter
  • Hydration, Pain relief, Dietary fibre
26
Q

List 6 causes of Haematochezia

A
  • Diverticulitis
  • Colitis (IBD, Infective)
  • Angiodysplasia (small vascular malformation in bowel wall)
  • Colorectal cancer
  • Anorectal disease (Haemorrhoids, anal fissure)
  • Upper GI bleeding (Large bleed with fast transit)
27
Q

Does an Upper GI bleed present with Haematochezia or Melena?

A

Haematochezia, if it is a large bleed with fast transit

Melena, normally

28
Q

Describe Melena in 2 ways

List 3 uncommon causes

A
  • Black tarry stools
  • Offensive smelling
  • Gastritis
  • Meckel’s diverticulum
  • Iron supplements
29
Q

List 4 causes of Upper GI bleeding that would result in Melena

A
  • Varices
  • PUD (Peptic Ulcer Disease)
  • Upper GI Malignancy
  • Oesophageal/ gastric cancer

GI System (26 decks)

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