All About - Muscles (Part 1)

This is a big topic including Cardiac muscle, Smooth muscle and Skeletal muscle.  Muscles are made up of muscle tissue, which consists of long cells which are called muscle fibres.  These fibres are able to change their length and so produce tension or pull.  This is the function of a muscle - to move parts of the body.

Cardiac Muscle is what makes up most of the heart and what makes it beat.

Smooth Muscle is found in parts of the body such as the skin and digestive system.

Skeletal Muscle is attached to bones and is responsible for voluntary movement.  When these muscles contract they pull the bones closer together or allow parts of the body to resist force from outside. 
Skeletal muscles are attached to at least 2 bones by tendons and the muscles themselves work in pairs.   As a muscle contracts (get shorter) the bones are moved.  The bones are moved back into place by another muscle contracting!

Ligaments attach bone to bone or sometimes help to keep tendons in place. 

In this blog I am planning to cover major superficial skeletal muscles but look out for future blogs about more muscles!  Check out my skeleton blog to help with the bones mentioned below.

The main superficial muscles are listed below.

Head & Neck:

·         Masseter (jaw)

·         Rhomboideus (top of neck)

·         Splenius (neck)

·         Trapezius (bottom part of neck and around withers)

·         Sternocephalicus (throat area)

·         Brachiocephalicus (main part of neck)

Shoulder & Forearm:

·         Deltoid (shoulder area)

·         Triceps (large section at top of foreleg)

·         Superficial Pectoral (chest)

·         Radial (front of foreleg)

·         Lateral Digital Extensor (middle of foreleg)

·         Common Digital Extensor ( large part of foreleg)

·         Lateral Carpal Flexor (back of foreleg)

Back and Barrel:

·         Latissimus Dorsi (about where saddle knee rolls sit)

·         Intercostal (over ribs)

·         Longissiums Dorsi (is deeper across the back)

·         Posterior Pectoral (girth area)

Hindquarters and Hindleg:

·         Superficial Gluteal (middle of hindquarters)

·         Semitendinosus (muscled down back of hindquarters)

·         Biceps Femoris (main part of hindquarters)

·         Deep Digital Flexor (behind lateral digital extensor)

·         Long Digital Extensor (main part of hindleg)

·         Lateral Digital Extensor (middle of hindleg)

Lower Leg:

·         Suspensory Ligament

·         Lateral Digital Extensor Tendon

·         Superficial Digital Flexor Tendon

·         Common Digital Extensor Tendon

·         Deep Digital Flexor Tendon

·         The Annular Ligament - not pictured - surrounds the sesamoid bones

The lower leg is where a large percentage of lameness originates, it is a good idea to have an understanding of the structure of this and how it works together.  There are no muscles in the lower leg - the bones are connected to the muscles above the knee via long tendons (see picture).

The Deep Digital Flexor Tendon is attached to the Deep Digital Flexor Muscle.  This tendon runs over the back of the knee (held in place by a check ligament) and down the back of the cannon bone.  It lies between the Suspensory Ligament and the Superficial Flexor Tendon.  Another check ligament holds the tendon in place halfway down the cannon bone.  The Deep Digital Flexor Tendon then passes over the sesamoid bones and down to connect to the pedal bone.

The Superficial Digital Flexor Tendon similarly attaches to the Superficial Flexor Muscle (not pictured).  This tendon runs down the back of the leg (behind the Deep Digital Flexor Tendon).  As it reaches the bottom of the leg it widens(to become part of the Annular Ligament) and then divides into 2 to pass either side of the pastern bones.  These 2 branches divide again and attach to the long and short pastern bones.

The Suspensory Ligament begins at the back of the knee passing just behind the cannon bone it divides just above the fetlock.  Part of the ligament becomes part of the Annular Ligament and part attaches to each sesamoid bone, the remainder passes around the front of the long pastern and joins to the Common Digital Extensor Tendon.

This gives you a good basis for knowing about muscles.  If you get a chance Gillian Higgins of Horses Inside Out gives some fantastic demonstrations of how muscles work to help our horses achieve everything they do!

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Until next time!

Jo