Page 746 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

CHAPTER 4

GASTROINTESTINAL SYSTEM
VetBooks.ir 721

4.1 The upper gastrointestinal tract 721

Henry Tremaine

4.2 The lower gastrointestinal tract 780

Ben Sykes

4.1 The upper gastrointestinal tract

The equine alimentary tract comprises the means the use of a variety of techniques is
oral cavity and its associated structures and the required to enable the clinician to investigate
pharynx, oesophagus, stomach, small intestine, and treat thoroughly any diseases affecting
cecum, colon and rectum, and presents a the gastrointestinal (GI) system. The function
challenging field of investigation for the equine of the GI tract can be summarised as the
clinician. A detailed knowledge of the structure prehension and processing of food and water
and function of the different components of to provide water and nutrients for normal
the tract is a prerequisite for understanding metabolic activity and, therefore, any disease
disturbances present in the diseased state. The that affects the alimentary tract is liable to have
complicated anatomy, physiology and pathology far-reaching effects on other body systems.

THE ORAL CAVITY

INTRODUCTION Each tooth is composed of an exposed clinical crown
and a larger reserve crown, which is embedded in
Normal dentition and age-related the bony alveolus. Attrition at the occlusal surface
changes occurs at 2–3 mm/year and continuous eruption of
Horses have 24 deciduous teeth, which can be the reserve crown maintains approximately 2 cm of
represented by the formula 2 × (Di 3/3, Dc 0/0, exposed crown.
Dp 3/3) = 24. The formula for the permanent
dentition is represented by 2 × (I 3/3, C 1/1, P 3 Incisor teeth
or 4/3, M 3/3) = 40 or 42. The Triadan system of Incisor teeth are simple rooted or brachydont teeth.
nomenclature is now used to denote dental location Each mandible and incisive bone contain three inci-
(Fig. 4.1). There are no deciduous molars and the 1 sors, which are in close apposition to each other
st
premolar termed the ‘wolf tooth’ is variably present. arranged in an approximate semicircle. Once in