This document provides information on the three types of muscle found in horses: skeletal, cardiac, and smooth muscle. It then describes in detail the main skeletal muscles of the horse's neck, shoulder, back, hindquarters, and limbs. For each muscle, it lists the origin and insertion points as well as the muscle's functions. In total, over 50 individual muscles are identified and explained.

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

2. 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

3. 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

4. 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.

5.  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 supraspinous
ligament & 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.

6.  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.

7.  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 pectoralis
transversus (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 pectoralis
profundus (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.

8.  Rectus capitis dorsalis major and rectus capitis dorsalis
minor: 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 supraspinous
ligaments, 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.

9. 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

10.  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

11.  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 humerus
and 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

12.  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

13.  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.

14.  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.


15.  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),vastus
intermedius (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 thepsoas 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 coccygeal
vertebrae 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.
