The structure of the large intestine and its involvement in digestion (fibre/bulk waste, water absorption, vitamins B & K)

Question 1

Structure of the large intestine

Answer 1

• 1.5 m long & 5cm diameter
• Upside down U shape
• 3 sections: ascending, transverse and descending colon

Question 2

Fibre/bulk waste

Answer 2

• cellulose and fibre pass right through the large intestine without being absorbed, both being an important component of our waste

Question 3

Water absorption

Answer 3

• Absorption of water occurs in the large intestine. 90% of water is absorbed back into the blood.

Question 4

Vitamin B & K

Answer 4

Bacteria (e.coli) live here and produce vitamin B & K and folic acid and gets absorbed into the bloodstream

Question 5

Waste

Answer 5

• The large intestine prepares waste for elimination
• When waste builds up message is sent to CNS which causes elimination of waste (feces)
• Feces is brown due to bacteria breaking down bilirubin (by-product of breakdown of hemoglobin)
• Feces has an odour because of gases produced by bacterial activity