Chapter 16 The horse
The horse appeared in its earliest form 55 million years ago as Eohippus, a small, multitoed mammal about 30 cm high. It had four toes on the fore limb and three on the hind limb and a weight- bearing pad under the central toe on each foot. Its teeth were capable of chewing succulent leaves. During its evolution over a period of many millions of years the number of toes reduced and the central third toe became encased in a simple hoof. This species was sequentially replaced by several others with similar skeletal structures and increasingly efficient teeth suitable for eating grass.
The skeletal system
The equine skeleton (Fig. 16.1) consists of two separate sections:

Fig. 16.1 The skeleton of the horse.
(With permission from Aspinall V 2006. The complete textbook of veterinary nursing. Butterworth- Heinemann, London, p 134.)
The skull

Fig. 16.2 The equine skull. A Lateral view. B Dorsal view.
(With permission from Aspinall V 2006. The complete textbook of veterinary nursing. Butterworth-Heinemann, London, p 135.)
The functions of the skull are:
The vertebral column
The function of the vertebral column is:
The ribs and sternum
The appendicular skeleton
The forelimb
The bones of the forelimb (Fig. 16.4) are:


Fig. 16.4 The equine forelimb.
(With permission from Aspinall V. 2006. The complete textbook of veterinary nursing. Butterworth-Heinemann, London, p 136.)
Pelvis
The muscular system
Soft tissues of the equine lower leg
The horse has evolved from a three- to four-toed, dog-like animal into the large animal taking its weight on one digit that we recognise today. The central digit is encased in a hoof while the outer toes are reduced to vestigial appendages that no longer reach the ground. This arrangement adds to the horse’s ability to run fast.
Ligaments and tendons
Important tendons found within the lower leg (Fig. 16.9) include:

Fig. 16.10 The stay apparatus and suspensory apparatus of the hindlimb.
(With permission from Aspinall V 2006. The complete textbook of veterinary nursing. Butterworth-Heinemann, London, p 141.)
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