Structure and Function of the Muscular System in Dogs

Below is information about the structure and function of the canine muscular system. We will tell you about the general structure of muscles, how muscles work in dogs, common diseases that affect the muscular system and common diagnostic tests performed in dogs to evaluate the muscular system.

What Is the Muscular System?

The muscular system is one of the largest systems in the dog’s body. It is composed of units of tissue that have the power to contract, and hence to produce movement.

Where Are Muscles Located?

Skeletal muscles are found throughout the entire skeletal system and are attached to bones, other muscles and skin. They account for about half the weight of an animal. Parts of the walls of hollow internal organs such as the heart, stomach and intestines, and blood vessels are composed of smooth muscles.

What Is the General Structure of Canine Muscles?

Most dogs are built for endurance, not speed, and their muscles reflect this. The muscle structure of the dog is much the same as its ancestor, the wolf. Muscles allow the animal to jump, run, stalk and engage in battle.

Muscles can be under voluntary or involuntary control. Voluntary muscles, such as those found in the arms and legs, can be controlled by thought. Involuntary muscles are those that are automatically controlled by the nervous system and cannot be moved at will. Examples of involuntary muscles are the muscles of the heart, diaphragm, and intestines.

There are three types of muscle tissue:

Each individual muscle is composed of many cells held together by connective tissue. Skeletal muscles attach to bones by means of connective tissue tendons, which are elastic and strong. When muscles contract, they pull on the tendons, which then pull on the bones and cause the limbs to move.

Each muscle fiber receives its own nerve impulses, which trigger various motions. Once a signal or an impulse travels down the nerve to the muscle, the muscle fiber changes chemical energy into mechanical energy, and the result is muscle contraction.

Muscles receive a generous blood supply from neighboring blood vessels. The arteries supplying a muscle enter at rather definite places and often connect within the muscle. A rich capillary (the smallest of all blood vessels) distribution helps to deliver oxygen to muscles. High intake of oxygen by the muscles is necessary for endurance running or other types of performance. Veins also accompany the arteries. During contraction, blood circulates by being forced into the larger veins.

What Is the Function of Muscles?

The primary function of muscles is to bring about movement to all or part of the dog’s body. Muscle is used to stabilize joints to prevent their collapse under a load. Smooth muscles maintain continence of the bladder and propel food through the bowel. Muscles also help to generate heat by shivering.

Voluntary muscles can contract and pull, but they cannot push, so they must work in pairs that flex and extend. Extensor muscles straighten the limbs and attach to the bones, so the bones act as levers. The flexor muscles, which bend the joints, act to pick up the limb. Their partners, the extensor muscles, in turn contract to bring the limb back down. The abductor muscles move the limbs away from the midline, and the adductor muscles move the limbs toward the midline.

What Are Common Diseases of Muscles in Dogs?

Common disease that affect muscle include:

What Types of Diagnostic Tests Are Used to Evaluate Muscles?