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3 - GI > Colon > Flashcards

Colon Flashcards

1
Q

What is the length of the colon and in which sex is it longer?

A

100-180cm

Females

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2
Q

What muscular arrangement distinguishes the colon?

A

3 longitudinal bands of muscle
Form taenia coli
Converge at the base of the appendix

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3
Q

What is the appearance of the colon lumen and what structures cause this appearance?
Where is this most apparent?

A

Triangular
Taenia coli
Transverse colon

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4
Q

What causes haustrations/sacculations?

A

Taenia coli are shorter than the colon

Causes a segmental appearance where the colon bulges (haustrations/sacculations)

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5
Q

What part of the GI tract does the appendix project from?

A

Caecum

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6
Q

What name is given to the start of the large intestine? What landmark denotes the start of the large intestine?

A

Ileocaecal junction

Ileocaecal valve

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7
Q

What forms the ileocaecal valve?

A

Oblique entrance and partial invagination of the ileum into the caecum

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8
Q

What complications can arise in the caecum during late bowel obstruction?

A

The caecum may dilate to the point of necrosis or perforation
Ileocaecal valve prevents back flow of excess air and colonic contents (no transit past the blockage distally or back proximal my through the valve

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9
Q

Where is the caecum located?

A

Right iliac fossa

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10
Q

What percentage of colonic rumours occur in the caecum and right side of the colon?
What presentations arise with a colonic tumour?

A

20%

Mass, change in bowel habits, iron deficiency anaemia, pain

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11
Q

Where does the appendix project from?

A

Postero-medial aspect of the caecum

~3cm below the ileocaecal valve

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12
Q

Describe the embryonic origin of the appendix and it’s movement during development.

A

Projection from the lateral side of caecum

Caecal wall overgrowth displaces the appendix medically and inferiorly

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13
Q

How commonly does appendicitis occur?

A

40,000 cases per year

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14
Q

Where does the ascending colon begin and end?

A

Begin - caecum

End - hepatic flexure

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15
Q

Where does the transverse colon begin and end?

A

Begin - hepatic flexure

End - splenic fixture

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16
Q

Why is the transverse colon difficult to navigate endoscopically?
In which sex do difficulties more commonly occur?

A

It is highly mobile

More common in females (70%)

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17
Q

At what level does the transverse colon lie at most commonly?

A

Umbilicus (L3-L4)

18
Q

How long is the descending colon?

A

22-30cm

19
Q

The sigmoid colon is very variable in length, what’s the average length and the upper limit?

A

37cm - 70cm

20
Q

What are the appendices epiploicae (epiploic appendices) and what section of the large colon has the most of these?

A

Fat-filled pouches of peritoneum

Sigmoid colon

21
Q

What is sigmoid volvulous and why is the sigmoid colon prone to it?

A

Closed loop obstruction of sigmoid colon due to twisting
Large length
Loose mesenteric attachment

22
Q

What percentage of colon cancers occur in the sigmoid colon?

A

25%

23
Q

What are colonic diverticulum? And in what section of the colon are they most common in Western society?

A

Out pouchings of bowel wall

Sigmoid colon

24
Q

What makes a bowel wall susceptible to colonic diverticulums?

A

Where the artery pierces the muscular wall causing weakness

25
Q

Where does the rectum begin and end?

A

Begin - anterior to S3

End - anal canal

26
Q

What differs between the human rectum and other mammalian rectums?

A

Human rectums are not straight

27
Q

Describe the shape of the human rectum

A

Curves anteriorly following the sacrum

Turns ~90 degrees through the pelvic diaphragm

28
Q

What are the valves of Houston?

A

3 transverse folds in the rectum which correspond with mucosal folds

29
Q

Why does the rectal lumen appear circular not triangular?

A

The thick circular muscle layer is stronger than the taeniae coli

30
Q

What percentage of colon cancers are found in the rectum?

A

50%

31
Q

How long is the anal canal?

A

~4cm

32
Q

What epithelium is found at the upper anal canal?

What is its embryonic origin?

A

Simple columnar epithelium

Hindgut

33
Q

The mid anal canal is the transition between what two embryonically derived tissues?

A

Endoderm of the hindgut (upper)

Ectoderm of proctodaeum invagination from skin

34
Q

What landmarks denote the mid anal canal?
From where do they arise?
What is the name of the line formed by the landmarks?

A

Valves of Ball
Arise from vertical columns of Morgagni
Dentate/pectineal line

35
Q

Below which landmark does the anal canal become stratified squamous epithelium?

A

Dentate/pectineal line

36
Q

What are the arterial supplies to the upper and lower rectum?

A

Upper rectum - superior rectal branch from inferior mesenteric artery
Lower rectum - inferior rectal branch from internal iliac artery

37
Q

What are the differences in pain perceived in the areas of rectum and why?

A

Upper rectum - dull pain and poorly located
Visceral Pelvic Splanchnic nerves

Lower rectum - sharp pain and well defined
Pudendal nerve

38
Q

What are the venous drains of the rectum and what do we therefore call the recall venous drainage?

A

Upper rectum - portal system via the inferior mesenteric vein
Lower rectum - systemic circulation via the internal iliac vein

A Porto-systemic anastomosis

39
Q

To which lymph nodes is lymph drained to from rectum?

A

Upper rectum - mesenteric nodes

Lower rectum - inguinal and iliac nodes

40
Q

What are haemorrhoids?

What determines whether they are painful or not?

A

Dilatations of the superior rectal veins

Whether they are above (painless) or below (painful) the dentate/pectineal line

41
Q

What kind of tumour will form in the rectum above the dentate line and what kind will form below the dentate line?

A

Above - adenocarcinoma

Below - squamous cell carcinoma

3 - GI (6 decks)

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