Muscle Groups and Functions

1. Rectus Capitus Lateralis: When RCL lengthens bilaterally, the head will

drop into flex (eccentric muscle work) When one side contracts

independently the head will incline to one side

Origin: Occiput.

Insertion: Atlas and axis

2. Splenius: As Splenius lengthens (eccentric muscle work) the neck can drop

into flexion. It stabilises the spine and balances the movement forwards

Origin: Fascia at withers, under the scapula and nuchal ligament.

Insertion: Transverse processes C3,4,5 and occiput

3. Multifidus cervicus: Aids in neck flexion and rotates the head to the

opposite side. It acts as a neck stabiliser and involved in fine postural

control

Origin: From C2-3 C3-4 etc. Continues to sacrum as multifidus dorsi

4. Brachiocephalicus: Flexes the neck and moves the shoulder

forward. Origin: Occiput near hinge of jaw. Insertion: deltoid tuberosity

of humerus. Runs with Omotransversarius (from wing of atlas and

transverse processes C2-4, inserts into Humerus)

5. Trapezius and Rhomboids: Elevate the shoulder, draw the scapula

upwards, forwards and backwards. Rhomboids form the crest and extend

the neck

6. . Supraspinatus: Extends the shoulder joint and stabilises the front aspect

of the shoulder. Works with subclavius muscles (Origin: Sup aspect

scapula, Insertion: 1st 4 ribs and continuation of Pectoralis Profundus

Origin:Sup aspect scapula.

Insertion: Humerus greater and lesser tubercle

Origin : T rapezius: nuchal lig ament and thoracic vertebrae.

Insertion : scapula spine ant and post

Origin : Rhomboids : Nuchal ligament.

Insertion : Sup aspect scapula

7. Infraspinatus: Rotates the foreleg outward (laterally), abducts the front leg

and stabilises the shoulder joint. Balances subscapularis muscle beneath

scapula and with Teres Minor muscle

Origin: Deep to deltoid, infrascapular fossa.

Insertion: Humerus

8. Deltoid: Flexes the shoulder joint, can also abduct shoulder

Origin: Inf. border spine of scapula, infrascapular fossa and fascia

over infraspinatus. Insertion: deltoid tubercle of humerus

9. Triceps: Flexes the shoulder joint and extends the elbow joint, locks the

elbow

Origin: Long head=rear border of

scapula

:Lat head=lat border of humerus

;med. head=med border of humeus

10. Biceps: Extends the shoulder joint, flexes the elbow, adducts foreleg.

Stabilises the shoulder.

Origin: Scapula at supraglenoid tubercle.

Insertion : Radial tuberosity of radius (only 1 head)

Insertion : Olecranon of ulna

Anterior or Descending Pectoral: Draws the foreleg forwards, adduction, cushions the

front leg on landing

Origin: Sternum, subclavius muscle and fascia.

Insertion: Humerus and radius

11. Serratus thoracis/ Ventral Serratus Muscle: When the legs are planted,

draws the trunk to the proper level. It acts to suspend the horse’s chest

between the forelegs and is important in the moment of suspension in the

horse’s natural forehand movement Origin: top underside of scapula.

Insertion: Serrated insertion at 1st-9th ribs and transverse processes

cervical spine C4C7

12. Posterior or Ascending Pectoral: Draws the foreleg backwards, forms

part of the sling which attaches the forelegs to the ribcage with subclavius

muscle

Origin: rear post aspect sternum.

Insertion: med side humerus and subclavius muscle(deep to) 4th-9th

ribs and abdominal tunic

13. Extensor Carpi Radialis: Extends the carpal joint, flexes the elbow joint

Origin: Lat epicondyle of humerus.

Insertion: below carpal joints into carpal bone and canon bone

14. Latissimus Dorsi: Lateral flexion of the spine, draws the forelimb

backwards (flexing the shoulder joint)

Origin: Thoraco lumbar fascia& supraspinous ligament.

Insertion: with teres major over post aspect of scapula & into humerus

15. Longissimus Dorsi: Allows the back to extend and lateral flexion

Origin: spinous processes of sacrum & upper surface of ilium,

connects with gluteus muscle and reinforcing fibres from lumbar and

bottom thoracic vertebrae and tops of ribs(gluteal tongue)

Insertion: Under scapula and to supraspinous ligament and cervical

spine

16. Intercostals: Support the rib cage and aid in respiration

Origin: External intercostals angle back and down- open rib

cage up and out : Internal intercostals angle forwards

and down- close rib cage

17. Obliques: Draws the hind leg under into flexion. Flexes the trunk laterally

and balances straight forward motion

Origin: last 14 ribs, lumbodorsal fascia and tubercoxae & Inguinal

ligament at pelvis Insertion: by aponeurosis at linea alba with rectus

abdominus

18. Rectus Abdominus: Supports the back and internal organs. Acts like the

bow string of a bow

Origin: 9th-4th rib cartilage and sternum.

Insertion : Pubic symphisis

19. Gluteus; Hind end action and impulsion into forward movement

Gluteus superficialis: Flexes hip and abducts femur

Gluteus medius: Extends hip and abducts femur

Gluteus profundus: Medially rotates femur

Gluteus superficialis Origin: From gluteal fascia & tuber coxae

Insertion: Into external trochanter of femur

Gluteus medius: Origin: From gluteal fascia, the ileum,

aponeurosis of longissimus dorsi and the sacroiliac ligament

Inserts: Gter trochanter of femur

20. Semimembranosus: Extends the hip and hock, pushes the body forwards

in the stance stage of the stride, adducts femur

Origin: Ischial tuberosity and sacro sciatic ligament.

Insertion :medial condyle of femur and medial tibia,part then joins

semitendinosus tendon to tuber calcis

21. Semitendinosus: In the stance phase it allows hip and hock extension

working with biceps femoris. In the swing phase it flexes the stifle, medially

rotates the hind leg and abducts hind leg

Origin: Sacrum and 1st tail vertebrae and ischial tuberosity.

Insertion: post and medial femur, patella and fascia, forms accessory

tendon which joins with Biceps femoris and gastrocnemius into tuber

calcis at hock

22. Biceps femoris: Extends the hip and hock- abducts the hind leg,, flexes

and extends the stifle depending on which head is used and in what position

the hind leg is held

Origin: Spinous and transverse processes of sacrum, sacrotuberous

ligament and ischial tuberosity.

Insertion: Post and med aspect femur and patella and fascia and as a

tendon with semitendinosus into tuber calcis

23/24.Tensor Fascia and Tensor Fascia Latae with quadriceps group deep:

Allows the stifle to extend and the hip to flex

Origin: tubercoxae & fascia and gluteus muscle.

Insertion: patella with some bands onto tibis. Deep to TFL is the quads

group with rectus femoris at the lower end and psoas and iliacus at the

upper end.

25. Long Digital Extensor: Extends the stifle and flexes the hock

Origin: With tibialis muscle, lat and anterior border of tibia and lower

lateral femur. Insertion: below tarsus on cannon bone and into 3rd phalanx

Lower layer of muscles of the horse

1. Masseter

2. Depressor of the Lower Lip

3. Buccinator

4. Zygomaticus

5. Orbicular of the Mouth

6. Lateral Dilator

7. Levator of Upper Lip and Nostril

8. Levator of Upper Lip

9. Superior Dilator

10. Corrugator of the Eyebrow

11. Common Muscle of the Ear

12. Posterior Oblique of the Head

13. Longissimus Atlantis

14. Longissimus capitis

15. Complexus

16. Cervical Ligament

17. Rhombiodeus

18. Rectus Capitis

19. omo-Hyoid

20. Jugular Vein

21. Sterno-Cephalicus

22. Multitidius Cervicis

23. Anterior Deep Pectoral

24. Supraspinatus

25. Infraspinatus

26. Infraspinatus

27. Teres Minor

28. Biceps Brachii

29. Anterior Superficial Pectoral

30. Brachialis

31. External Radial Extensor

32. Common Digital Extensor

33. Triceps Brachii

34. Perforans

35. External Flexor

36. Lateral Digital Extensor

37. Oblique Extensor

38. Common Digital Extensor

39. Lateral Digital Extensor

40. Perforatus

41. Suspensory Ligament

42. Perforatus

43. Common Digital Extensor

44. Internal Flexor

45. Middle Flexor

46. Suspensory Ligament

47. Rhomboideus

48. Longissimus Dorsi

49. transversalis Costarum

50. External Intercostals

51. Serratus Thoracis

52. External Rhoracic Vein

53. Posterior Deep Pectoral

54. External Oblique of Abdomen

55. Serratus Posterior

56. Onternal Oblique of Abdomen

57. Iliacus

58. Rectus Femoris

59. External Vastus

60. Middle Glutaeus

61. Muscles of the Tail

62. Semitendin

63. Semimembranosus

64. Semimembranosus

65. Gastrocnemius

66. Soleus

67. Long Digital Extensor

68. Lateral Digital Extensor

69. Deep Flexor (Perforans)

70. Semitendinosus

71. Internal Vastus

72. Sartorius

73. Gracilis

74. Long Digital Extensor

75. Anterior Tibial Extensor

76. Long Digital Extensor

77. Suspensory Ligament

78. Perforans

79. Perforatus

80. Suspensory Ligament 81. Lateral Extensor

82. Suspensory Ligament