Large Intestine Flashcards by Anja Powell

What are the sacs in the colon called?

Haustra

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What re the 3 strips of longitudinal muscle in the large colon called?

Teneai coli

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What are the 2 bends in the large colon called and which is higher?

Hepatic flexure and splenic flexure

Splenic flexure is higher

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What are the parts of the colon from proximal to distal?

Caecum,
Ascending,
Transverse,
Descending,
Sigmoid

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Where is McBurnies point and what is it?

1/3rd of the way in from superior anterior ileac spine to umbilicus
Point of maximal tenderness in appendicitis

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What does the mesentery on the sigmoid colon put it at risk of?

Twisting around itself and cutting off its blood supply (sigmoid volvulus)

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What branches off the aorta from L1-4?1

L1: superior mesenteric artery
L2: renal arteries
L3: inferior mesenteric artery
L4: bifurcation into common ileacs

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Which artery supplies the transverse colon and what does it come from?

Middle colic

Superior mesenteric artery

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Which artery supplies the ascending colon and which artery does it originate from?

Right colic

Superior mesenteric artery

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Which artery supplies the descending colon and which artery does it originate from?

Left colic

Inferior mesenteric artery

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What is the only blood supply to the appendix?

Appendicular artery from the superior mesenteric artery

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What is the name of the arch of arteries that supplies the ascending, transverse and descending colon?

Marginal artery of Drummond

Anastomoses of right colic, middle colic and left colic

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What supplies the sigmoid colon and where does it originate from?

Sigmoid arteries

Inferior mesenteric artery

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Does the inferior mesenteric artery supply any of the rectum and anus?

The proximal part of the anal canal (superior rectal artery)

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Is there any connection between the hindgut and distal rectal blood supply?

Anastomoses between the superior, middle and inferior rectal arteries (supplied by the IMA and branches of the internal ileac)

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What are the 3 anastomoses in the portal venous system?

Skin around umbilicus
distal end of oesophagus
Rectum/anal canal

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What causes varicose veins?

Back pressure through the anastomoses between the portal and canal venous systems

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What is the gross sign of varicose veins on the abdomen?

Caput medusa

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Are polyps benign or malignant and what can they be called?

Can be either
Benign = adenoma
Malignant = adenocarcinoma

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What is the progression from normal mucosa to malignancy in the colon?

Normal mucosa 
-->
Adenoma (benign)
-->
Adenocarcinoma (malignant)

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How should adenomas in the colon be dealt with?

Removed as are pre-malignant

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What are dukes A, B and C

Staging for colorectal cancer
Dukes A = no metastasis - good prognosis
Dukes B = limited metastasis - poor prognosis
Dukes C = metastases to lymph nodes - very poor prognosis

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What is lynch syndrome?

Inherited syndrome that predisposes to lots of polyps which can develop to become malignant - presents in 50s

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What is the differences between the internal and external anal sphincter?

At the same place; internal is smooth muscle and external is skeletal muscle

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What is the purpose of the appendix?

No purpose in humans

What controls contraction and relaxation of the ileocaecal valve?

Distension of the caecum causes contraction to prevent backflow Distension of the duodenum causes relaxation to allow passage of food

How is water absorbed from the large intestine?

Absorption of Na and Cl back into the blood which causes water to follow it by osmosis

What is secreted in the large intestine?

Mucous (to form slippery surface gel) | Proteins for host defence

What mixes the contents of the large intestine?

Hautration - very slow process

What is mass movement and how often does it occur?

Contraction of large segments of the large intestine to drive faeces distally - often triggered by a meal Occurs roughly 3 times per day

What causes the need to defecate?

Faeces in the rectum cause it to stretch, when stretched enough causes relaxation of the internal anal sphincter, the external anal sphincter voluntarily controls until is convenient to defecate

What reduces the resistance to stool achieved by squatting?

Straightening out of the anal-rectal angle

How does intraabdominal pressure affect defecation?

Contraction of abdominal muscles and suspension of breathing increase intraabdominal pressure which assists defecation

Where are the most commensal bacteria in the human body present?

Colon

Where does intestinal gas occur from?

Swallowing of air (mostly burped up) | Fermentation of certain foods

What is constipation?

Presence of hard dry faeces in the colon that are hard to defecate

What causes constipation?

Delay in defecation causing increased water to be absorbed

What is the difference between a laxative and purgative?

Laxative: assists emptying of the colon Purgative: clears the whole small and large intestine - used prior to surgery

How does a laxative work?

Softens or lubricates the stool to make it easier to pass

What is a diverticulum?

Outpouching of a mucosal tissue through the muscle wall

What is a false diverticulum?

A diverticulum that does not breach through the muscle coat, these are acquired

How is diverticulosis (the presence of diverticulums) diagnosed?

Colonoscopy | Barium enema

What is diverticulitis?

Inflammation of diverticula

What are the clinical features of diverticulitis?

Left inferior quadrant pain Sepsis Altered bowel habit

What is a fistula?

An abnormal connection between 2 epithelial surfaces

What is the treatment for diverticulitis?

Oral antibiotics, can be managed in the community

What are the two types of inflammatory bowel disease and what characterises them?

Crohns disease Ulcerative colitis Presence of ulcers in the colon

What are the 4 types of colitis?

Infective colitis, Ischaemic colti, Ulcerative coltis, Crohns colitis

What are the symptoms of colitis?

Diarrhoea (can contain blood) Abdominal cramps Dehydration Sepsis

How is colitis diagnosed?

Sigmoidoscopy (colonoscopy) + biopsy Stool cultures Barium enema

How is ulcerative colitis or crohns colitis treated?

IV fluids, IV steroids, GI rest If not better within 3/4 days, surgery

What causes large bowel obstruction?

Tumour, Stricture, Volvulus

What are the clinical signs of colonic obstruction?

Vomiting Absolute constipation Distended abdomen Pain

What causes watery diarrhoea?

Collagenous colitis, | Lymphocytic colitis

What are the 4 types of laxatives and how do they work?

Bulk laxatives: increase vol in the GI tract Osmotic laxatives: increase H2O in the GI tract Faecal softeners: lubricate stool Stimulate laxatives: stimulate ENs to increase peristalsis

What are the two types of route that water can be reabsorbed by?

Transcellular or paracellular

Which method of water reabsorption is favoured in the fed state?

Inward movement of Na (and thus water) coupled to glucose or amino acids

What is the use of bicarbonate in water reabsorption?

Mops up excess protons from Na/H exchanger

Movement of what ion is more important in water reabsorption in the fasting state?

Chlorine

Which ion channel is used for secretion of Cl across the apical membrane of enterocytes in the large intestine?

CFTR - means CF also affects water reabsorption

What is the first priority in treatment of diarrhoea?

Maintenance of fluid and electrolyte balance

What is used for treatment of diarrhoea?

Rehydration therapy - specific concentrations of fluid and electrolyte are given to optimise reabsorption of water along the colon

What types of drug (and which is the most common) are used as anti-motility agents in diarrhoea?

Opioids - Loperimide (available over the counter)

What is the key symptom of colorectal cancer?

Rectal bleeding (if painful is less likely to be cancer)

What type of cell change occurs in anal cancers and are they common?

Very uncommon | Squamous cell carcinoma

What diseases increase the risk of colorectal cancer?

IBD (Crohns disease + ulcerative colitis)

What are the symptoms of colorectal cancer?

``` Rectal bleeding, Colicky abdominal pain, Change in bowel habit, Weight loss, Iron deficiency anaemia, Abdominal mass ```

What investigations are done to investigate possible colorectal cancer and what is the gold standard?

Barium enema CT colonography Colonoscopy/Sigmoidoscopy - gold standard

What screening test is done for colorectal cancer?

FIT test - stool sample | If positive, offered colonoscopy

How is colorectal cancer usually treated and how successful is this?

Surgery - colectomy | Very successful

What is the follow up for colorectal surgery?

CT scans

Large Intestine Flashcards

(71 cards)