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Lakshya j. kakati 10-vk-44 College of veterinary science,AAU,khanapara,ghy-22

Muscular system of horse, Equine muscular system

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Lakshya j. kakati 10-vk-44

College of veterinary

science,AAU,khanapara,ghy-22

Types of muscle

There are 3 types of muscle, all found within the equine:

Skeletal muscle: Contraction of these muscles leads to the muscle pulling a tendon, which in turn pulls a bone. Moving a bone results in either flexing or extending a joint. Skeletal muscles are usually arranged in pairs so that they oppose each other (they are "antagonists"), with one flexing the joint (a flexor muscle) and the other extending it (extensor muscle). Therefore, one muscle of the pair must be relaxed in order for the other muscle in the pair to contract and bend the joint properly. A muscle or muscles and its/their tendon(s) that operate together to cause flexion or extension of a joint are referred to respectively as a flexor unit and an extensor unit.

Cardiac: muscle which makes up the heart.

Smooth: muscle which makes up automatic systems

Build of skeletal muscle Skeletal muscle is made up of several muscle bundles,

which in turn are made up of muscle fibers. Muscle fibers have bundles of myofibrils, which are all parallel to one another, and are able to contract due to actin and myosin. Muscle is covered by a fibrous tissue called fascia, to which other muscles can attach, and muscles attach to bone via tendons

Main skeletal muscles of the horse Muscles of the neck, shoulder, chest, and back

Brachiocephalicus: originates from the temporal bone, atlas, and 3rd and 4thcervical vertebrae, and inserts on the humerus. Pulls the forelimb forward, raises scapula in collection.

Cervicalis ascendens: originates at the transverse process of the final 3-4 cervical vertebrae, inserts into the first rib.

Cutaneous coli: originates from the cariniform cartilage and inserts into the cervical fascia. Lies on the ventral parts of the neck (near the jugular groove).

Deltoideus: originates at the scapula, inserts into the humerus. Helps to flex the scapulohumeral joint.

Intertransversales lumborum: between the transverse processes of 1-4th lumbar vertebrae.

Intertransversalis colli: occurs between the transverse articular space of the vertebrae, and the lateral side of the vertebrae

Latissimus dorsi: originates at the supraspinousligament & thoracolumbar fascia, inserts in the humerus. Antagonist to brachiocephalicus. Supports the back, helps to pull the body of the horse forward when a limb is extended and placed on the ground, also helps to flex the scapulohumeral joint.

Longissimus capitis: originates on the first 2 thoracic vertebrae and the cervical vertebrae. Inserts into the atlas.

Longissimus costarum: originates on lumbar dorsal fascia, insert on caudal side of ribs, and the cervical vertebrae.

Longus colli: originates from the cervical vertebrae and the first 5-6 thoracic vertebrae.

Masseter: cheek muscle, moves the jaw open and closed and allows for chewing

Multifidus cervicis: originates on last 4-5 cervical vertebrae and first thoracic, insert into the spinous and articular processes of the cervical vertebrae.

Multifidus dorsi: originates on lateral side of sacrum, the articular processes of the lumbar and transverses processes of the thoracic vertebrae. Inserts into spinous processes of first 2 sacral vertebrae on through the final cervical vertebrae.

Obliquus capitis cranialis: originate on ventral side of wing of atlas, inserts on occipital bone.

Obliquus capitis caudalis: originates on dorsal side of spine and the articular process of the axis, insert into dorsal side of the atlas' wing.

Omohyoideus: originates from the subscapular fascia of the scapulohumeral joint, inserts in the hyoid. Allows for flexion of the jaw.

Omotransversarius: originates in the atlas and the cervical vertebrae (C2-C4), continues down dorsal to the brachiocephalicus to the point of the shoulder, then combines with the trapezius and inserts into the humerus. Helps raise the scapula and move the limb forward.

Pectoral muscles: there are 4 pectorals, and they all function in adduction of the limb. The pectoralis descendens (cranial superficial pectoral) originates from the cariniform cartilage of the sternum, and inserts into the humerus. The pectoralistransversus (transverse superficial pectoral) originates from the ventral side of the sternum and inserts on theproximal third of the horse's forearm. The largest of the pectorals, the pectoralisprofundus (caudal deep pectoral), originates on the caudal side of the sternum, and inserts into the humerus and onto the tendon of the coracobrachialis muscle. The pectoralis ascendens(caudal superficial pectoral), or the subclavius, originates on the cranial side of the sternum, and inserts into the dorsal side of the supraspinatus muscle.

Rectus capitis dorsalis major and rectus capitis dorsalisminor: originate on spinous process of axis and dorsal side of the atlas, respectively, both insert into occipital bone.

Rectus capitis ventralis minor and rectus capitis lateralis: originate from the atlas, insert into the occipital bone.

Rhomboideus: originates from the nuchal and supraspinousligaments, inserts on the medial scapular cartilage, is under the trapezius. Helps to raise the shoulder toward the head, and raise the neck upward.

Scalenus: originates on the cranial and lateral side of the first rib, inserts into the transverse process of the cervical vertebrae (C4-C7).

Semispinalis capitis: originates on the cervical vertebrae and first 6-7 thoracic vertebrae. Inserts on the occipital bone, ventral to the nuchal crest.

Serratus dorsalis cranial and caudal: originates on the lumbar dorsal fascia, inserts into the lateral side of the 5-12 or 10-18th rib respectively.

Muscles of the forelimb Biceps brachii: originates from the caudal side of the

scapula and inserts into the radial tuberosity

Brachialis: originates from the caudoproximal side of the humerus, inserts into the craniomedial side of proximal radius

Tensor fasciae antebrachii: originates from the tendon of the latissimus dorsi and the caudal side of the scapula,

Triceps brachii: has three heads which originate and insert into separate places: the caudal side of the scapula and into the lateral & caudal side of the olecranon

Extensor carpi radialis: originates from the humerus, continues distally along the dorsal side of the radius, and inserts on the metacarpal tuberosity.

Common digital extensor: part originates from the humerus and travels distally, to become the common digital extensor tendon at the bottom third of the radius

Lateral digital extensor: originates from the lateral tuberosity of the radius and from the ulna, becomes the lateral digital extensor at the proximal portion of the metacarpus

Extensor carpi obliquus: originates from the radius and inserts into the top of the second metacarpal

Flexor carpi radialis: originates from the humerus and inserts into the proximal side of the second metacarpal

Ulnaris lateralis: originates on the lateral side of the humerus, inserts into the accessory carpal bone and on the proximal side of the lateral splint bone.

Superficial digital flexor: originates on the humerusand the caudal side of the radius, travels distally to become the superficial digital flexor tendon.

Deep digital flexor: has three heads. One originates from the humerus, one on the proximal side of the radius, one on the proximal side of the ulna

Muscles of the hindquarters and lower hindleg

Adductor: originates from the ventral side of the pubis and ischium.

Biceps femoris: originates from lateral sacroiliac ligaments.

Gemellus: a deep muscle that originates on lateral side of the ischium.

Gluteus superficialis: originates from the gluteal fascia and tuber coxae.

Gluteus superficialis: originates from the gluteal fascia and tuber coxae.

Gluteus medius: originates from the ilium.

Gluteus profundus: originates from the superior ischiatic spine and shaft of the ilium

Gracilis: originates from the pelvic symphysis all the way to the pubic tendon.

Iliacus: originates on ventral side of ilium.

Obturator externus: originates from the ventral side of the pubis ad ischium.

Obturator internus: originates on pelvic surface of the pubis, ischium, and ilium, and the wing of the sacrum, inserts into the trochanter fossa. Rotates femur outward.

Pectineus: originates from the prepubic tendon, the accessory ligament, and the cranial side of the pubis. Inserts into the medial side of the femur. Adducts the limb, flexes the hip joint.

Psoas minor: originates from first 4-5 lumbar and last 3 thoracic vertebrae.

Psoas major: originates on lumbar vertebrae and last 2 ribs.

Quadratus femoris: originates on ventral side of ischium (cranial to semimembranous muscle), inserts into the caudal side of the femur. Adducts the thigh, extends the hip.

Quadratus lumborum: originates on the side of the final 2 ribs, inserts into the wing of the sacrum. Allows the horse to flex laterally.

Quadriceps femoris: has four heads which include the rectus femoris(originates from ilium, inserts into base and cranial of patella), vastus medialis(originates on medial side of femur, inserts into medial side of patella), vastusintermedius (originates from cranial side of femur, inserts into medial side of patella), and vastus lateralis (originates on lateral side of femur, inserts on lateral and cranial side of patella). These four muscles extend the femoropatellar joint (stifle joint). Additionally, the vastus intermedius raises the femoropatellar capsule, and the rectus femoris flexes the hip.

Sartorius: originates from the iliac fascia and the tendon of the psoas minor, inserts into the medial patellar ligament and tuberosity of the tibia. Adducts the limb, flexes the hip.

Semimembranosus: originates from ventral side of tuber ischii and caudal side of sacrosciatic ligament. Inserts into medial epicondyle of femur. Extends the hip joint, adducts the limb.

Semitendinosus: originates from transverse processes of 1st and 2nd coccygealvertebrae and ventral side of tuber ischium. Inserts into the cranial side of the tibia and the tuber calcis. Flexes the femoropatellar joint, causes inward rotation of the leg, and extends the tarsus and hip.

Tensor fasciae latae: originates from the tuber coxae, inserts into the lateral patellar ligament, the cranial side of the tibia, and the broadaponeurosis of the patella. Helps to flex the hip and extend the femoropatellar joint.