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2 Gastrointestinal Function
2.1 Introduction
macrophagephagocytosis
The development of the digestive tract involves cell specialisation occurring within the different regions of the tract and in relation to the functions of these different regions. Thus, while certain cells are specialised for absorbing food in a suitably processed form, other cells are primarily protective in function or are associated with transportation and with pre‐ treatment of the food to allow its utilisation. Further specialisation has evolved in relation to the nature of the food, so that marked variations occur in the gastrointestinal anatomy in herbivores as compared to carnivores. In general, however, the tract of higher vertebrates is divided into distinct anatomical regions, namely the buccal cavity, oesophagus, stomach, small intestines, large intestines and rectum. Further subdivisions of these regions are present.
2.2 Functions of the Alimentary Tract
These may be considered under the following four principal headings: