The given diagram is of the digestive system of the humans. The labels 'i', 'j', and 'k' represents the absorption of the products of the digestion from the small intestine and the large intestine.
'i' - This arrow represents the absorption of sugars and amino acids into the bloodstream via the villi present in the small intestine.
'j' - This arrow represents the absorption of the fatty acids into the lymphatic vessel through the lacteals present in the villi. These merge to form the lymphatic vessel.
'k' - This arrow represents the absorption of the ions and nutrients which are released by the bacteria present in the intestine.