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 animal 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) ROBIN PETERSON ILLUSTRATIONS 2 www.TheHorse.com THE HORSE January 2006 January 2006 THE HORSE www.TheHorse.com 3 Saudi Arabia as chief medical illustrator closer to the tail (cauda). Example: The Median Plane—This divides the horse’s for the King Faisal Specialist Hospital and horse’s back is caudal to his neck. body into right and left halves (median Research Center in Riyadh. Through the Rostral—That part of the structure means in the middle). years, he has received many honors and lo cated closer to the nose (rostrum). Sagittal Plane—Any plane parallel to the awards of excellence for his work. Ex ample: The eyes are rostral to the ears. median plane. Example: A plane dividing Kainer joined the anatomy faculty at Proximal—A location toward the the right and left sides of a hoof. Colorado State in 1961 and remained there attached end of a limb. Example: The Medial—Structures located closer to the for 27 years. He, too, has won a variety of proximal end of the cannon bone connects median plane. Example: When you look awards and honors for his work. with the knee. at a horse’s left side, you see the medial In this opening article of our 12-part Needless to say, since there are entire Distal—Indicates a location toward the surfaces of his right limbs. series on equine anat omy and physiology, books written on equid anatomy and phys- free end of a limb—the part that is farther Lateral—Structures located away from we will attempt to paint a picture of how iology, it would be impossible to address away from the body. Example: The distal the median plane. Example: When you today’s horse is constructed and what this the entire animal in one article. Therefore, end of the cannon bone connects with the look at a horse’s left side, you see the lateral means in the realm of form to function. We this month we look in-depth at the horse’s long pastern bone or third phalanx. surfaces of his left limbs. will not be quoting a lot of sources, for the largest organ, its skin, and details of the most part, because the information to be nomenclature used to discuss anatomy presented is an amalgamation of what has and physiology, as well as lightly touch on been recorded in thousands of scientific structures that will be covered in-depth papers, textbooks, and manuals as knowl- in the coming year. In the months ahead edge has been gained and disseminated we’ll have articles on joints, the foreleg, the through the years. However, we would be hind limb, the hoof, the head and neck, the remiss in not calling attention to two valu- back, muscles, tendons and ligaments, and able sources upon which we shall draw There are some similarities between human and equine anatomy, but there are a great many differ- the digestive, circulatory, respiratory, and heavily. Both are writ­­ten at the layman ences as well. For example, the human knee and the equine stifle have a lot in common. The equine re productive systems. level. They are Horses and Horsemanship radius is similar to the human forearm. The equine carpal or knee bones are similar to human wrist by the late M.E. En sminger, BS, MA, PhD, bones. And the equine splint bones compare to human fingers. A Glossary to Get You Started and The Coloring Atlas of Horse Anatomy by Colorado State University. has authored seven books, and today he We will begin this discussion of equine Robert A. Kain er, DVM, MS, and Thomas McCracken, who resigned from Colora do is president of Biographix, LLC. Early in anatomy with Kainer’s and McCracken’s O. McCracken, MS, both of whom were at State in 1994 to enter private business, his career, McCracken spent two years in explanation of terminology that is routine for veterinarians and researchers, but can be confusing to some horse owners. Along SUCCEED can help you achieve your with the two authors’ terminology, we’ll No Guts... No Glory. goals with measurable results. add examples to demonstrate how the Use SUCCEED and see the results for yourself, sometimes terminology might be employed. Under- in a matter of days. Soon, you’ll be able to measure the standing the terminology is essential when Highest scoring U.S. Dressage rider at 2006 WEG difference in the show ring. discussing various conditions with a veter- SUCCEED delivers highly specialized nutrients to support inarian. a healthy digestive tract, the fuel line to every other system in the horse’s body. Use the product that gives real Here is some terminology, accompanied results – use SUCCEED. by illustrations, to help you visualize: On Side—The horse’s left side; also called Available in oral paste, top-dress granules or SmartPaks. near side. Example: Normally, the side on which we mount and dismount. Off Side—Right side of the horse; also called far side. Example: One theory of why Congratulations Floriano trainer and rider Steffen we mount from the left is that warriors and Peters and owners Stephen and Laurelyn Browning. soldiers of old generally carried a sword on the left side and this would get in the way ® SUCCEED helps Steffen Peters get the most out of his horses. if swinging up from the right or off side of the horse. Available from tack and feed stores, Dorsal—Parts of the horse’s anatomy “SUCCEED is the best single product I’ve ever used.” or ask your veterinarian. toward his back (dorsum). Ex ample: The “With SUCCEED my horses are consistently trainable and relaxed both at home and at shows. point of the croup is dorsal to the stifle. Trainability has been the biggest factor. There was a defi nite improvement. SUCCEED will Anatomy toward the belly continue to be a part of our program.” Ventral— (venter). Example: The stallion’s reproduc- Steffen Peters; trainer of Floriano, 2006 USDF Grand Prix Horse of the Year, on SUCCEED since August 2005. tive organs are ventral to his flank. • Highest scoring U.S. rider in all three dressage events at the 2006 World Equestrian Games Cranial—That part of the horse’s struc- (WEG) in Aachen, Germany. ture above the knees and hocks located • Led the U.S. to a Bronze Medal fi nish in the team competition at WEG. • Maintained a commanding lead during the 2006 USEF National Grand Prix Championship 866-270-7939 ext.115 closer to the skull (cranium). Example: competition in Gladstone, NJ. The withers are cranial to the tail. www.SucceedDCP.com Caudal—That part of the horse’s struc- Photos © 2007, Stuart Vesty SUCCEED® and Digestive Conditioning Program® are registered trademarks of Freedom Health, LLC. ©2007. All Rights Reserved. PATENT PENDING. ture above the knees and hocks located 4 www.TheHorse.com THE HORSE January 2006 Month 2006 THE HORSE www.TheHorse.com 5 Planes of the Horse structure is located away from the axis. 5) A simple stomach followed by a long better place to start than with the skin, the small intestine and a large, complicated horse’s largest organ, ranging from 12-24% Classifying the Horse large intestine where fermentation of of the animal’s total weight depending on Cranial Dorsal Caudal Before leaving our Atlas authors, we’ll feed occurs. age. It serves a number of functions. It pass along their explanation of proper 6) Well-developed skin glands. protects underlying tissues from injury, Frontal plane ter minology for this animal we are 7) Large heart and lungs. drying, water absorption, and bacterial dis cussing, along with what they consider 8) A uterus with short horns and a relatively invasion. Another important role involves to be identifying characteristics: large body, and a prominent de pression thermoregulation (regulation of body Cranial “Horses and their close relatives, don keys in each ovary where the egg cells are temperature). The skin also excretes water Transverse Plane—Passes through the Rostral and zebras, are in the mammalian order of released. and salts through sweat glands, senses the head, trunk, or limb perpendicular to the odd-toed, hoofed animals (Perissodactyla) 9) A large, vascular penis and a complete environment, and synthesizes vitamin D in part’s long axis. Example: An ultrasound as are their distant relatives, rhinoceroses set of male accessory sex glands. response to sunlight. image gives a transverse view of the limb. and tapirs. The horse, Equus caballus, is There are similarities between human The skin consists of various cellular and Dorsal Plane—Passes through a body an equid, a member of the horse family and equine anatomy, but there are many tissue components.