BY LES SELLNOW he evolution of the horse from a tiny, four-toed an imal, T perhaps no more than one foot tall, to the variety of equines in existence today, is one of the wonders of nature. During that process of change, the horse evolved over many thousands of years from an animal that predators hunted for food to an ani- mal that became a servant and friend for mankind. Today’s horses are designed to do one of two things— pull a load with their shoulders or carry riders on their backs. The type of horses utilized for these respective tasks varies a good deal; one is large and pon d erous and the other is lighter-boned with less mu s cle mass. Even within these two types, there are significant differences. For example, the conformation of a roping or cutting This first article of a 12-part series on equine anatomy and horse is different from that of the American Saddle- physiology discusses basic terminology, the horse’s largest bred. Yet there is a basic sameness to anatomy. organ, and how horses and humans are alike (and different) DR. ROBIN PETERSON ILLUSTRATION 2 www.TheHorse.com THE HORSE DecemberJanuary 2006 DecemberJanuary 2006 2006 THE HORSE www.TheHorse.com 3 BY LES SELLNOW he evolution of the horse from a tiny, four-toed an imal, T perhaps no more than one foot tall, to the variety of equines in existence today, is one of the wonders of nature. During that process of change, the horse evolved over many thousands of years from an animal that predators hunted for food to an ani- mal that became a servant and friend for mankind. Today’s horses are designed to do one of two things— pull a load with their shoulders or carry riders on their backs. The type of horses utilized for these respective tasks varies a good deal; one is large and pon d erous and the other is lighter-boned with less mu s cle mass. Even within these two types, there are significant differences. For example, the conformation of a roping or cutting This first article of a 12-part series on equine anatomy and horse is different from that of the American Saddle- physiology discusses basic terminology, the horse’s largest bred. Yet there is a basic sameness to anatomy. organ, and how horses and humans are alike (and different) DR. ROBIN PETERSON ILLUSTRATION 2 www.TheHorse.com THE HORSE DecemberJanuary 2006 DecemberJanuary 2006 2006 THE HORSE www.TheHorse.com 3 explanation of terminology that is routine horse’s back is caudal to his neck. for veterinarians and researchers, but can Rostral—That part of the structure MembershipMembership be confusing to some horse owners. Along located closer to the nose (rostrum). Ex- with the two authors’ terminology, we’ll add ample: The eyes are rostral to the ears. examples to dem onstrate how the termi- Proximal—A location toward the at- nology might be employed. Understanding tached end of a limb. Example: The proxi- the terminology is essential when discuss- mal end of the cannon bone connects with HasHas ItsIts Benefits!Benefits! In this opening article of our 12-part ing various conditions with a veterinarian. the knee. series on equine anat omy and physiology, Here is some terminology, accompanied Distal—Indicates a location toward the we will attempt to paint a picture of how by illustrations, to help you visualize: free end of a limb—the part that is farther Become A Member of the American Association of today’s horse is constructed and what this On Side—The horse’s left side; also called away from the body. Example: The distal means in the realm of form to function. We near side. Example: Normally, the side on end of the cannon bone connects with the Equine Veterinary Technicians and Enjoy These Benets: will not be quoting a lot of sources, for the which we mount and dismount. long pastern bone or third phalanx. most part, because the information to be Off Side—Right side of the horse; also Median Plane—This divides the horse’s presented is an amalgamation of what has called far side. Example: One theory of why body into right and left halves (median • Quarterly newsletter • Member eligibility to ofce positions on the been recorded in thousands of scientific pa- we mount from the left instead of the right means in the middle). • Advance notication of regional CE events executive board, on equine specialty pers, textbooks, and manuals as knowledge is that warriors and soldiers of old gener- Sagittal Plane—Any plane parallel to the • Access to member-only section of web site which academy, or the equine certicate program has been gained and disseminated through ally carried a sword on the left side and this median plane. Example: A plane dividing the years. However, we would be remiss in would get in the way if swinging up from the right and left sides of a hoof. features an employment database and • Purchasing power offered through NTRA and not calling attention to two valuable sourc- the right or off side of the horse. Medial—Structures located closer to the CE announcements Blackwell Publishing es upon which we shall draw heavily. Both Dorsal—Parts of the horse’s anatomy median plane. Example: When you look at • Reduced registration fees at the annual AAEP/ • Representation at veterinary conferences are written at the layman level. They are toward his back (dorsum). Ex ample: The a horse’s left side, you see the medial sur- • Technician networking Horses and Horsemanship by the late M.E. point of the croup is dorsal to the stifle. faces of his right limbs. AAEVT meeting and regional AAEVT meetings En sminger, BS, MA, PhD, and The Coloring Ventral—Anatomy tow ard the belly (ven- Lateral—Structures located away from • Member discounts at CE events, on books/publica- • Public, industry and professional awareness Atlas of Horse Anatomy by Robert A. Kain- ter). Example: The stallion’s reproductive the median plane. Example: When you tions, and on membership renewal • Speaking opportunities er, DVM, MS, and Thomas O. McCracken, organs are ventral to his flank. look at a horse’s left side, you see the lateral • On-line CE courses MS, both of whom were at Colorado State Cranial—That part of the horse’s struc- surfaces of his left limbs. University. ture above the knees and hocks located Transverse Plane—Passes through the McCracken, who resigned from Colora- closer to the skull (cranium). Example: The head, trunk, or limb perpendicular to the do State in 1994 to enter private business, withers are cranial to the tail. part’s long axis. Example: An ultrasound has authored seven books, and today he Caudal—That part of the horse’s struc- image gives a transverse view of the limb. is president of Biographix, LLC. Early in ture above the knees and hocks located Dorsal Plane—Passes through a body his career, McCracken spent two years in closer to the tail (cauda). Example: The part parallel to its dorsal surfaces. Saudi Arabia as chief medical illustrator for the King Faisal Specialist Hospital and Research Center in Riyadh. Through the years, he has received many honors and awards of excellence for his work. Kainer joined the anatomy faculty at Colorado State in 1961 and remained there The American Association of Equine Veterinary Technicians & Assistants (AAEVT) for 27 years. He, too, has won a variety of is a sister organization to the American Association of Equine Practitioners (AAEP). awards and honors for his work. Needless to say, since there are entire We are a separate, non-prot corporation whose membership consists of technicians, assistants, books written on equid anatomy and phys- iology, it would be impossible to address practice managers and support staff from all aspects of equine veterinary medicine. the entire animal in one article. Therefore, this month we look in-depth at the horse’s Our mission is to promote the health and welfare of the horse largest organ, its skin, and details of the through the education and professional enrichment nomenclature used to discuss anatomy and physiology, as well as lightly touch on USTRATION of the equine veterinary technician and assistant. LL structures that will be covered in-depth in the coming year. In the months ahead Membership is open to all technicians, assistants, practice we’ll have articles on joints, the foreleg, the managers and paraprofessionals in the United States and Canada, hind limb, the hoof, the head and neck, the back, muscles, tendons and ligaments, and IN PETERSON I regardless of licensure or certication. Student membership is open to B the digestive, circulatory, respiratory, and O those enrolled in AVMA accredited veterinary technology schools. R re productive systems. As of 2007, international membership is also available. DR. There are some similarities between human and equine anatomy, but there are a great many differ- A Glossary to Get You Started ences as well. For example, the human knee and the equine stifle have a lot in common. The equine We will begin this discussion of equine radius is similar to the human forearm. The equine carpal or knee bones are similar to human wrist For more information and to become a member, anatomy with Kainer’s and McCracken’s bones. And the equine splint bones compare to human fingers. please visit our web site at www.aaevt.org 4 www.TheHorse.com THE HORSE December 2006 December 2006 THE HORSE www.TheHorse.com 5 explanation of terminology that is routine horse’s back is caudal to his neck.