Basic Anatomy
It has been said that form follows function. E. caballus is no exception. Horses are characterized by long legs in relation to other parts of their body, such as other “speed” animals, the cheetah or the greyhound (Kearns et al. 2002). Although all long-legged, not every horse body is fit for high intensity activity. This brief overview focuses on the overall body of a racehorse.
(Permission from Milfer Farms)
Head and Neck
Balance, stability, freedom of stride and agility of a horse are dependent upon the head and neck. From the front, a horse head should be triangular in appearance, narrowing at the nose. The head joins the neck to allow for the most flexion and movement and least hindrance of air passages. The neck itself is slightly arched.
Withers and Shoulders
The shoulder of a horse slopes at a 45- to 50 –degree angle with the ground. A long shoulder increases stride and absorbs concussion in the foot. The withers of a horse should be well-defined with good depth. This allows for freedom of movement and again a longer stride.
Chest
The chest houses the lungs and heart and thus, should be deep. A chest that is too wide can cause waddling and a chest that is too narrow may cause the two forelegs to be set too close together.
Body
The ribs should be felt but not seen in an athletic horse with a competitive muscle composition. The back should be straight, short, and muscular enough to support a rider.
Hindquarters
The hindquarters provide the force necessary to propel the horse forward. Therefore they should be muscular. The length of the croup, the area between the hips and the point of the buttocks, has a direct relationship with speed and endurance. The width of the croup is directly related to strength and power.
Figure 1. Skeleton of the Horse. Depicts major skeletal bones of the Equus caballus. (Permission from www.spequine.com)
Musculoskeletal System
The appendicular skeleton is characterized by long, tubular bones with epiphyses or expanded ends. An articular cartilage covers the end of each bond allowing for a smooth frictionless gliding of the joints' surfaces. It also distributes the forces placed upon a limb. The midportion of the bone is known as the diaphysis through which runs the bone marrow. Immature bones have a growth plate which is gradually lost. Below the growth plate is the mataphysis. Periosteum covers the majority of the bones surface providing blood and nerve supply. Tendons, ligaments and joint capsules surround, stabilize and connect joints. They do not produce motion but play a key role in movement. Ligaments and joint capsules both connect bone to other bone. Tendons attach muscle to bone and transmit muscular forces in motion.
Skeletal muscle accounts for 40 to 50 percent of total body weight. Primarily used for movement, muscle also serves to protect the skeleton. Muscle absorbs shock and distributes forces (Siegal 1996).