Large Intestine Flashcards
What are the different parts of the large intestine?
- Caecum
- appendix
- Colon
- ascending
- transverse
- descending
- sigmoid
- Rectum
What are the names of the 2 flexures in the large intestines?
- Hepatic flexure (bend in relation to liver)
- Splenic flexure (bends around level of spleen)
What are Taenia coli?
- Longitudinal muscle
- Only on one side - not all the way round the tube
What are haurtra(e) or haustrations?
Little pouches
What are Appendices epiploicae?
Fatty tags
What are the 2 sphincters present in the rectum/anus?
- Internal sphincter: under involuntary control
- External sphincter: under voluntary control
What is the name of the junction where the small intestine joins with the large intestine?
The ileo-caecal junction
at junction between caecum and ascending colon
What does the fold of mucosa at the ileo-caecal junction allow?
Allows chyme to pass from SI to LI but not vice versa
What is meant when the appendix is described as vermiform?
It looks worm-like
What are the functions of the appendix and caecum?
Do not appear to have any essential function in human beings
What is the epithelium of the large intestines?
Simple columnar with goblet cells
Does the large intestine contain intestinal crypts?
Yes, contains intestinal crypts of Leiberkühn
What are the differences between large and small intestines?
- LI have no villi
- LI have an incomplete later of longitudinal muscle (Taenia coli)
- LI have a ring-like arrangement of circular muscle (haustrae)
- LI has fatty tags (appendices epiploicae)
Approximately how much chyme enters the LI from the ileum?
0.5-1.0 litres
What does the colon do and what happens if it fails to do this?
- Colon absorbs fluid and electrolytes from SI chyme
- If fails to reabsorb = diarrhoea
What are the roles of the intestinal flora in the LI?
- Ferment dietary fibre and lipid
- Gasses produces
- Synthesise some vitamins
- Vitamin B complex; vitamin K (responsible for making vitamins inside gut - need vitamin B for cell metabolism and vitamin K is essential for blood clotting)
What are the actions of motility in the large intestines and where in the LI does this mainly occur?
- Mixing movements
- Similar to segmentation in SI
- Contraction of circular muscles then contraction of longitudinal muscles
- ‘squeezing’ action of chyme
- Mainly in caecum and ascending colon
What is meant by the propulsive movements of the large intestines?
Move things from one point to another point
Where does peristalsis occur in the large intestines and what does it do?
- ‘Short range’ peristalsis in transverse and descending colon
- Propels semi-solid faecal matter towards rectum
What are the ‘mass movements’ of the large intestine?
- Infrequent, more sustained contractions
- Usually after meals
- Moves chyme/faeces from proximal colon to distal colon
- Rectal distension associated with desire to defaecate
What is mean by the word ‘defaecation’?
- Ejection of faecal matter from rectum, via anal canal
Is defaecation voluntary or involuntary reflex?
Involuntary reflex
What kind of muscle is the rectum and internal anal sphincter and what are they controlled by?
Smooth muscle, controlled by the ANS
What kind of muscle is the external anal sphincter?
Skeletal muscle
At what age is voluntary control of the external anal sphincter gained?
Around 2 years of age
Some diseases of the large bowel are managed by the removal of a portion of the colon. What is the name of these procedures?
- Ileostomy
- Colostomy
What is the opening of an ileostomy or colostomy called?
A stoma
What is diarrhoea characterised by?
- Someone going to the toilet more than 3 times a day to defecate
- Characterised by excessively watery stools
What is diarrhoea mainly caused by?
- GIT infections
- Shift in the bacterial flora
What is diarrhoea associated with?
- Failure of fluid absorption
- Reduced colonic motility
(Less mixing and less fluid absorption)
What are the results of diarrhoea on a person?
- Dehydration
- Electrolyte imbalance
What is constipation characterised by?
- Defecate less than 3 times per week
- Characterised by hard faeces, difficult to pass
What is constipation cause by?
- Due to increased fluid absorption
What is constipation associated with?
- GIT spasm
- Side effect of some drugs e.g. opiates
What can help reduce constipation?
- Dietary fibre - better fibre diet allows for better passing
