L46: Large Intestine Flashcards
What are the three components of the large intestine?
- Caecum;
- Colon;
- Rectum.
What are the two colic flexures (curvatures)?
- Hepatic (right);
- Splenic (left).
What are haustrae?
Sacculation of the large intestine- give rise to segmented appearance
What are appendices epiploicae?
Fatty tags
What are the two sphincters of the anal canal?
- Internal (involuntary);
- External (voluntary).
Where does the caecum end and colon begin?
Ileo-caecal junction
Where does chyme pass through into the large intestine?
Ileo-caecal valve
What prevents back flow from L.I. to S.I.?
A fold of mucosa
Where is the appendix located?
Off of the caecum
What epithelium lines the large intestine?
Simple, columnar with goblet cells
What are intestinal crypts (of Leiberkuhn)?
Intestinal glands found along the epithelium lining (invaginations), secrete intestinal juice
What are the main differences of structure between the S.I. and L.I.?
- Villi in small intestine ONLY;
- In L.I., incomplete layer of longitudinal muscle (taenia coli);
- In circular muscle, ring-like arrangement of circular muscle (haustrae);
- Fatty tags.
Why is the recto-anal junction at higher risk of cancer?
Change of epithelium from simple columnar to stratified squamous
What is the primary function of the large intestine?
Fluid and electrolyte absorption
What is the primary site of absorption in the large intestine?
Colon
How is the colon subdivided?
- Ascending;
- Transverse;
- Descending;
- Sigmoid.
What are the roles of intestinal flora?
- Ferment dietary fibre (cellulose) and lipid;
- Gas production (‘flatus’);
- Synthesis some vitamins;
- Vitamin B complex (cell metabolism);
- Vitamin K (blood clotting).
Describe the motility of the large intestine.
Caecum and ascending colon:
- Mixing movements;
- Similar segmentation to S.I.;
- Contraction of circular muscles, shortening of longitudinal muscles.
Transverse and descending colon:
- Local peristalsis (faecal matter towards rectum);
- Mass movements (moves chyme/faeces from proximal to distal colon).
What movements of the large intestine are infrequent?
Mass movements
What type of muscle is in the internal anal sphincter?
Smooth (controlled by ANS)
What type of muscle is in the external anal sphincter?
Skeletal (striated)
What is diarrhoea?
- Excessively watery stools;
- Failure of fluid absorption
- Leads to dehydration and electrolyte imbalance.
What is constipation?
- Hard faeces, difficult to pass;
- Due to increased fluid absorption;
- Side effect of some drugs, excess fibre (>70g).
