Bacterial digestion
Fibre (\rightarrow H_2 + CH_4 + \text{short chain fatty acids})
Urea + amino acids (\rightarrow NH_4)
Bilirubin → urobilirogen
Cystine + methionine (\rightarrow H_2S)
Bile acid fermentation (\rightarrow N_2 + H_2 + CO_2)
Na+/water absorption
-
Stimulated by aldosterone
-
Cl moves paracellularly (secreted in small intestine)
-
Na+ 2nd active transport
-
Creates osmotic gradient for water
-
K+ can undergo secretion + absorption in the colon - usually net secretion
-
Balance determined by plasma [K+], aldosterone + cAMP
-
People with diarrhoea can become hypokalemic
Motility
Slow contractions squeeze contents backwards and forwards as a segment - haustration
A few times a day becomes organised into peristatic wave - mass movement
Haustra disappear during mass movement then reform