Mentalis

• Origin: Side of the front end of the lower jaw (near the lower canine tooth in the dog and feline).

• Insertion: Skin of the front of the chin.

• Action: Pulls the chin upward, which in turn pushes the front of the lower lip upward (usually against the upper lip).

• Structure: The mentalis is located at the front of the chin (in the prominence of the chin in the horse and ox). It passes downward from its bony origin to its skin insertion. The muscle fibers of both sides unite and intermingle with fat and connective tissue. In the dog and feline, the muscle fans out as it descends.

Frontalis

• Origin: Top of the skull, between the horns, and at the base of the horn.

• Insertion: The skin of the forehead above and in front of the eye, and into the orbicularis oculi.

• Action: Lifts the region above the eye (the "eyebrow" region).

• Structure: The frontalis, present only in the ox, is a wide, thin muscle that lies on the forehead. The fibers that insert into the upper inner corner of the eye pull this region upward and rearward, resembling the function of the levator anguli oculi medialis (which is present in the others species but not in the ox).

In the horse, dog, and feline, the muscle comparable to the frontalis is the fronto-scutularis. It inserts into, and pulls, the scutiform cartilage, which is in turn attached to the ear by other muscle. It is therefore considered one of the muscles of the ear, and not a muscle that moves the eyebrow region, as in the ox.

LATERALIS NASI Upper part L otter part

OUTER WALL Of NASAL CAVITY

Muscle Thoracic Limb Horse
ORBICULARIS ORIS

LATERALIS NASI Upper part L otter part

OUTER WALL Of NASAL CAVITY

The Bones The Dog Picture

ORBICULARIS ORIS

PLATYSMA

HORSE DOG

Lateralis nasi (Dilator nasi, Dilator naris alaris)

HORSE

• Origin: Upper part: From the nasal bone, along the upper edge of the large notch at the front end of the bones of the snout (to the rear of the nostril). Lower part: Along the bone of the lower edge of the notch of the snout.

• Insertion: Both parts insert into the surface of the outer wall of the nasal cavity.

• Action: Dilates the nasal cavity by pulling the soft, outer wall of the nasal cavity outward and rearward, and assists in dilating the actual nostril opening. It does not dilate or expand the "false nostril" (nasal diverticulum), which is a narrow, elongated, dead-end pocket that lies above the true nasal cavity.

• Structure: The lateralis nasi surrounds the bony notch of the snout and converges on the surface of the outer wall of the nasal cavity. It consists of upper and lower parts. The upper part passes under the tendon of the levator labii maxillaris. This muscle is not present in the dog or feline.

• Origin: Upper part: From the edge of the top of the cartilage of the snout (in the front of the nasal bone and just behind the nostril). Lower part: Along the edge of the forwardmost projecting bone of the upper jaw (incisivus bone) and the adjacent cartilage.

• Insertion: Upper part: Upper part of the inner wing of the nostril. Lower part: Outer wing of the nostril.

• Action: Assists in dilating the nostril.

• Structure: The lateralis nasi is less developed in the ox than in the horse. It inserts directly into parts of the edges of the nostril, rather than into the outer wall of the nasal cavity.

Platysma (Cutaneous faciei & labiorum)

The platysma is the facial part of the cutaneous muscle ("skin muscle"), a thin muscular sheet that covers various parts of the body (see page 65). The platysma passes over the side of the lower jaw in the horse and inserts into the corner of the mouth, fusing with the orbicularis oris. It pulls the corner of the mouth rearward and has a strong effect on the shape of the mouth. It is least developed in the horse.

In the ox, the platysma is more developed. It pulls the corner of the mouth rearward (and also slightly downward by several inclined fibers designated the depressor anguli oris). Some fibers of the cutaneous muscle of the head transversely cross over the snout and insert into the upper part of the lateralis nasi. They assist in dilating the nostril.

The platysma of the dog is quite wide; it begins on the midline on the back of the upper neck and inserts into the comer of the mouth. The platysma of the feline is the widest and most developed of the species described here. It remains wide at its inserting end on the side of the face where it attaches to several facial muscles, yet, as in the other species, its importance is in its retraction of the corner of the mouth.

Horse Facial Muscles Front

Ear muscles

Numerous muscles surround and attach to the ear, moving it forward, backward, inward (toward the midline), and outward (away from the midline), with the ear pivoting at its lower end. They also rotate the ear from a forward-facing position to a rear-facing position, directing its concave, sound-gathering "cup" outwardly as it rotates. The muscles insert directly onto the ear, or insert onto the movable scutiform cartilage, which provides origin for other muscles that then insert onto the ear.

According to Sisson and Grossman (The Anatomy of the Domestic Animals, 1975), there are 17 ear muscles in the horse, and according to Miller (Anatomy of the Dog, 1979), there are 19 ear muscles in the dog.

Because the ear muscles are so numerous, do not create surface form, and lie in layers, they are depicted here as linear axes, with an arrow indicating their direction of pull. The ear of the ox tends to be directed horizontally, rather than upright, as in the horse, dog, and feline.

S Scutiform cartilage

Scutiform Cartilage Canine

ZYGOMATIC ARCH

orbital ligament

Orbital Ligament Dog

ZYGOMATIC ARCH

orbital ligament

The Holes Formed Zygomatic Arches

ZYGOMATIC ARCH

Zygomatic Arch Horses

Temporalis

• Origin: Upper rear part of the skull, on the rounded braincase and the surrounding bony ridges.

• Insertion: Top of the upward projection of the lower jaw (continuing down the front edge of the jaw in the horse, dog, and feline).

• Action: Closes the mouth, for biting and chewing, by lifting the lower jaw up and pulling it back.

• Structure: The muscle fibers begin from a wide origin and converge deeply onto the upper tip of the lower jaw. Except for the ox, the rounded form of the muscle fills out the upper back portion of the head, especially in the dog and feline, where the muscle is well developed. In the ox, the temporalis is small and lies on the side of the cranium. In the horse, a conspicuous hollow can be seen on the surface of the muscle behind the orbit. It is called the "salt cellar."

In the horse and feline, the muscles of both sides meet at the midline toward the rear. In the dog, the muscles of both sides may or may not meet at the midline, depending on the breed. In the dog and feline, an upright bony ridge of variable development may be located between the muscles of both sides. In the dog and feline, a small band of muscle fibers arises from the rear end of the zygomatic arch and curves upward, forward, and then downward to the lower jaw, deep to the zygomatic arch, where it fuses with the rest of the muscle.

Veterinary Musculi Capitis

Masseter

• Origin: Lower edge of the zygomatic arch (continuing forward along a bony ridge of the side of the face in the horse and ox).

• Insertion: Side of the broad, upright portion of the lower jaw—up to the thickened edge in the horse, to the rear edge in the ox, and into the lower and rear edges of the lower jaw and onto the surface of the deep pterygoid muscle (beyond the rear end of the lower jaw) in the dog and feline.

• Action: Closes the mouth, for biting and chewing, by lifting the lower jaw. In the horse and ox, it also pulls the lower jaw sideways (outward)

and forward for grinding food. Because the jaw joint has a flattened upper articular surface, some gliding can occur here. The dog and feline have a more tightly hinged jaw joint, permitting basic opening and closing, with limited side motion.

• Structure: The masseter is a strong, flattened muscle in the horse and ox, bulging in the dog and feline. In the horse and ox, it stops at the edge of the lower jaw. In the dog and feline, it projects substantially beyond the lower and rear borders of the jaw. Composed of two or more layers, only a small portion of the deep layer of the masseter comes to the surface in the horse, just in front of the jaw joint.

Jaw Joint Horse

BOTTOM VIEW

HORSE

DIGASTRIC

OUTLINE OF MASSETER

BOTTOM VIEW

HORSE

Digastric

HORSE, DOG, AND FELINE

• Origin: Bony projection on the bottom of the rear part of the skull.

• Insertion: Horse: Rear edge of the lower jaw. Dog and feline: Lower edge of the rear end of the lower jaw.

• Action: Pulls the rear end of the lower jaw backward (pivoting the lower jaw at the jaw joint), which opens the mouth.

• Structure: In the horse, the digastric consists of a deep portion (not illustrated) and a shorter, more superficial portion called the occipito-mandibularis. The occipitomandibularis contributes minimally to the rear profile of the lower jaw. In the dog and feline, the digastric is a relatively thick muscle. Its front half usually projects downward beyond the lower edge of the masseter muscle to create the profile of the lower jaw in this region. In the feline, the muscle inserts farther forward than in the dog, sometimes reaching the chin. The digastric is not visible on the surface in the ox. The parotid gland lies on the side of the neck to the rear of the lower jaw, and covers the upper part of the digastric muscle.

Digastric Muscle The Dog

DIGASTRIC

OUTLINE OF MASSETER

PAROTID G [AND

PAROTID G [AND

Rear Neck Anatomy

Salivary glands

The parotid gland is a soft, sponge-like form sitting in the hollow between the back of the lower jaw and the side of the neck (wing of the atlas). It extends up to, and surrounds (except in the ox), the base of the ear. The gland spreads over the rear edge of the lower jaw and softens the definition of the anatomy in this region. When the head is extended up, the parotid gland sinks in; when the head is flexed down and the neck is arched, it bulges out. In the ox, the parotid gland is narrower and reaches up to, but does not surround, the base of the ear. The parotid gland is elongated in the horse and ox, and shorter and relatively rounder in the dog and feline.

The mandibular gland is a separate, elongated gland that lies along the rear edge of the parotid gland in the ox. In the dog and feline, the mandibular gland is an ovoid body, approximately half the size of the parotid gland, and is located below the parotid gland. It is in contact with the lower end of the parotid. The mandibular gland of the horse is mostly concealed by the parotid gland.

Brcph Brachiocephalicus; Clcer Cleidocervicalis; Mass Masseter; Myloh Mylohyoid; Omohy Omohyoid; Omotr Omotransversarius; Splen Splenius; Stcph Sternocephaticus; Stman Sternomandibularis; Stthh Stemothyrohyoid; Stthy Sternothyroid.

OBLIQUUS CAPITIS CAUDALIS

OBLIQUUS CAPITIS

Nuchal Ligament Dog

NUCHAL LIGAMENT

obliquus capitis cranialis

RECTUS CAPITIS DORSALIS MAjOR

obliquus capitis caudal is nuchal ligament

RECTUS CAPITIS DORSALIS MAjOR

HORSE DOG

TOPV1EW TOR VIEW

WING OF ATLAS

Obliquus Capitis Cranialis

RECTUS CAPITIS DORSAL IS MAJOR

HORSE DOG

TOPV1EW TOR VIEW

RECTUS CAPITIS DORSAL IS MAJOR

OBLIQUUS CAPITIS CAUDALIS

NUCHAL LIGAMENT

obliquus capitis cranialis

RECTUS CAPITIS DORSALIS MAjOR

obliquus capitis caudal is nuchal ligament

OBLIQUUS CAPITIS

WING OF ATLAS

RECTUS CAPITIS DORSALIS MAjOR

Short Neck Muscles

The following three muscles are located on the back of the neck, just behind the skull: the obliquus capitis caudalis, the obliquus capitis cranialis, and the rectus capitis dorsalis major. They are covered by narrow and wide tendons and thin muscles, yet they help create the fullness on the back of the neck, determined in large part by the width of the atlas (the first neck vertebra) and the vertical projection of the axis (the second neck vertebra).

Obliquus capitis caudalis (Large oblique muscle, Axoido-atloideus)

• Origin: Entire side of the expanded upright spine of the second neck vertebra (axis).

• Insertion: Rear surface of the expanded side projection, or wing, of the first neck vertebra (atlas).

• Action: Rotates the first neck vertebra (which pivots on the second neck vertebra) to the side, thereby turning the head to the side.

• Structure: Largest of the group, this thick muscle is directed forward and outward. Its rear portion is buried in muscle, but as it advances, it approaches the surface.

Obliquus capitis cranialis (Small oblique muscle, Atloido-occipitalis)

• Origin: Front surface of the wing of the first neck vertebra (atlas).

• Insertion: Rear part of the skull.

• Action: Both sides together extend the head.

• Structure: This is a short muscle which fill the space between the skull and the first neck vertebra. It is directed forward, upward, and inward.

Rectus capitis dorsalis major (Posterior straight muscle, Axoido-occipitalis)

• Origin: Upper edge of the upright spine of the second neck vertebra.

• Insertion: Rear end of the skull near the midline.

• Structure: This narrow muscle lies just to the side of, and partly under, the nuchal ligament of the neck in the horse and ox. In the dog and the feline, it lies against its fellow of the other side on the midline; the nuchal ligament begins at the rear of the second neck vertebra.

LONG I SSI M US CAPITIS

LONGISSIMUS ATiANTIS

Musculi Capitis

HORSE HORSE

FIRST NECK VERTEBRA (ATLAS)

LONGISSIMUS CAPITIS

NUCHAL LIGAMENT

SEMISPINA LIS CAPITIS

Nuchal Ligament Canine

LONGISSIMUS ATLANTIS

OMOTRANSVERSARIUS

lower edge of splenius

WING OF ATWS

LONGISSIMUS ATLANTIS

LONG I SSI M US CAPITIS

FIRST NECK VERTEBRA (ATLAS)

LONGISSIMUS ATiANTIS

LONGISSIMUS CAPITIS

OMOTRANSVERSARIUS

NUCHAL LIGAMENT

lower edge of splenius

WING OF ATWS

INSERTION OF BRACHIOCEPHALIC'S a SPLENIUS

SEMISPINA LIS CAPITIS

HORSE HORSE

Longissimus capitis and Longissimus atlantis

HORSE

• Origin: By tendinous fibers from the region of the sides of the first and second thoracic vertebrae, and by successive attachments from the upper sides of the seventh through the third neck vertebrae.

• Insertion: Longissimus capitis: base of the skull behind the ear hole. Longissimus atlantis: lower end of the expanded side projection, or wing, of the first neck vertebra (atlas).

• Action: Muscles of both sides of the body: extend the head and neck. One side only: pulls the head and neck to that side, or rotates the atlas, and therefore the head, to that side.

• Structure: The longissimus capitis and longissimus atlantis are two elongated, parallel muscles, part of the longissimus system of the vertebral column. They lie deep to the splenius. The upper (rear) muscle, the longissimus capitis, inserts into the skull by a flat tendon, in common with the splenius. This tendon may occasionally be seen on the surface passing over the wing of the atlas, as well as on its way to the skull. The lower (forward) muscle, the longissimus atlantis, inserts into the lower end of the wing of the atlas by a strong, round tendon, which can become quite prominent on the surface. This tendon inserts in common with the splenius and the omotransversarius.

The longissimus capitis and atlantis in the dog and feline do not affect surface form, but their tendons may be seen in the ox.

Several narrow or wide tendons and thin muscle pass over, or attach onto the lower end of, the wing of the atlas. The deeper structures (splenius to the wing of the atlas, omotransversarius, longissimus atlantis, longissimus capitis, and semispinalis capitis) may show through the more superficial structures (the wide, thin tendon and thin muscle of the brachiocephalicus and the wide, thin tendon of the splenius, both of which attach to the rear end of the skull). The key to understanding this region is to isolate each visible form and follow it toward its origin and insertion.

Horse 5th Thoracic Vertebra

Splenitis

HORSE

• Origin: Rear end of the cord of the nuchal ligament, and the tips of the upright spines of the third, fourth, and fifth thoracic vertebrae.

• Insertion: By five separate and distinct insertions into (1) a line on the rear end of the skull (from the midline above down to the mastoid process behind the ear hole), (2) the lower end of the expanded side projection of the first vertebra (atlas), (3) the sides of the third, fourth, and fifth neck vertebrae (not the second).

• Action: Both sides of the body together: Extend the head and lift the neck. One side only: Pulls the head and neck to that side.

• Structure: The splenius is a large, flat, triangular muscle located between the head, the top of the shoulder, and the neck vertebrae.

It comes to the surface in an irregular rectangular window bordered by the brachiocephalicus in front, the trapezius and a small portion of the rhomboid behind, and the neck portion of the serratus ventralis (cervicis) below. The splenius develops into five segments—the uppermost segment attaches to the skull by a wide, thin tendon, the next to the first neck vertebra by a strong tendon, and the remaining three to the sides of neck vertebrae three, four, and five directly by fleshy fibers. The lower portion of the splenius is covered by the neck portion of the serratus ventralis, whose elongated segments are oriented in a direction very similar to the segments of the splenius.

In the ox, dog, and feline, the splenius is completely covered. However, it adds a layer of muscular thickness that participates in forming the volume of the neck. It is thicker in the dog and the feline than in the ox.

Dog Serratus Ventralis

omotransversarius

Omotransversarius (Trachelo-acromialis)

HORSE

• Origin: The sides of the first four neck vertebrae.

• Insertion: Fascia on the surface of the shoulder region and outside of the upper arm toward the front of the elbow.

• Action: Pulls the neck to the side when the limb is fixed; pulls the limb forward when the neck is fixed.

• Structure: The omotransversarius is thick and muscular on the side of the neck. It widens as it descends, then it thins as it passes over the shoulder, where it fuses with the fascia on the surface of the shoulder and upper arm. The omotransversarius used to be called the cleidocervi-calis of the brachiocephalicus.

• Origin: Side of the first neck vertebra.

• Insertion: Lower end of the spine (bony ridge) of the shoulder blade, and the fascia of the shoulder.

• Structure: The omotransversarius is a narrow, straplike muscle, tapered at its upper end, located on the side of the neck. It extends from the upper end of the neck behind the skull to the shoulder blade. Its upper portion is covered by the brachiocephalicus, which crosses it on a strong diagonal line. This leaves an elongated triangular portion of the lower end of the omotransversarius exposed at the shoulder.

DOG AND FELINE

• Origin: Lower end of the side of the first neck vertebra. Feline: Also from the base of the skull.

• Insertion: Lower end (excluding the tip) of the spine of the shoulder blade, and the surface of the deltoid. The origin and insertion are often reversed in the dog and the feline when the shoulder is considered the more fixed point of attachment.

Omotransversarius Dog
omotransversarius

Brachiocephalicus (Mastoido-humeralis, Cephalo-humeral)

The brachiocephalicus ("arm-to-head" muscle) is a long, wide, straplike muscle that passes from the head and neck down to the front of the elbow region. It can be separated into upper and lower portions by a horizontal tendon, which represents the missing clavicle (a vestigial clavicle may also be present). The longer, upper portion, the cleidocephalicus, ("clavicle-to-head") is further divided in some species into two parts—the cleidomastoid ("clavicle-to-mastoid bone") and the cleidocervicalis ("clavicle-to-neck") or cleido-occipitalis ("clavicle-to-occipital bone"). The smaller lower portion, located between the shoulder and the elbow region, is called the cleidobrachialis ("clavicle-to-arm").

The clavicle is absent in the horse and the ox and is represented by a tendinous line (present in the ox, variable in the horse). In the dog and the feline, the tendinous line is present and more distinct, especially in the feline. A small, vestigial bony clavicle, lying deep to the brachiocephalicus, is fused to the inner half of this tendinous line. The clavicle does not articulate with the skeleton.

HORSE

• Origin: Continuous line on the rear of the skull, beginning on the midline, passing downward and forward, and ending behind and below the ear hole (on the mastoid process).

• Insertion: Line on the humerus that begins halfway down the outside of the bone and passes downward and inward on the front of the lower half of the bone.

• Action: Pulls the entire forelimb forward and extends the shoulder joint when the head and neck are fixed. Both sides of the body: Pulls the head and neck downward. One side only: Pulls the head and neck to that side.

• Structure: The brachiocephalicus is a simple, long, straplike muscle passing from the head to the arm. Its upper end develops a thin, wide tendon that attaches to the skull and allows deeper structures to show through. It descends in front of the shoulder joint. The lower end of the muscle passes between the biceps and the brachialis (completely covering the biceps) and then inserts on the humerus, in common with the pectoralis descendens. The brachiocephalicus lies in front of the omotransversarius, which used to be considered part of the brachiocephalicus, and was called the cleidocervicalis.

• Origin: Cleido-occipitalis: upper rear end of the skull and adjacent nuchal ligament on the midline of the neck. Cleidomastoideus: Base of the skull, just behind the ear hole.

• Insertion: Diagonal line on the lower part of the front of the humerus, passing downward and inward, beginning halfway down the bone toward the outside; fascia of the surface of the upper arm and the forearm.

• Structure: The upper portion of the brachiocephalicus is divisible into the cleido-occipitalis and the cleidomastoid. The two portions are distinctly separate, with their upper ends separated by a narrow interval. The upper end of the cleido-occipitalis widens as it approaches the top of the neck. The muscle as a whole narrows at the shoulder and passes in front of the shoulder joint.

DOG AND FELINE

• Origin: Cleidocervicalis: Midline on the back of the front half of the neck. In the feline it also attaches to the edge of the base of the skull for a short distance from the midline. Cleidomastoid: Base of the skull behind the ear hole.

• Insertion: Dog: Vertical line on the lower half of the front of the humerus. Feline: Inner surface of the upper end of the ulna, just below the elbow joint, in common with the brachialis.

• Structure: The upper portion of the brachiocephalicus is divided into a superficial part, the cleidocervicalis (cleidotrapezius in the feline), and a deep part, the cleidomastoid. The cleidocervicalis begins wide and thin on the back of the front half of the neck and covers a considerable portion of the neck. The cleidomastoid is deep and covered by the cleidocervicalis and the sternocephalicus. The overall muscle narrows as it descends, crossing in front of the shoulder joint. Because of its insertion past the elbow joint onto the ulna in the feline, the form of the brachiocephalicus is directed lower on the limb than in the other species.

TERMINOLOGY OF BRACHIOCEPHALICUS

LEFT SIDE OF NECK

CLEIDOCERVICALIS OR

CLEIDO-OCCIPITALIS

cleidocephalicus

CLEIDOMASTOID

BRACHIOCEPHALICUS

CLEIDOBRACHIALIS

CLAVICLE. OR TENDON REPRESENTING CLAVICLE

Brachiocephalicus Human

BRMHI0CEPHALJCU5 SEPARATED INTO ITS COMPONENTS IN THE OX AND THE DOC

Occipitalis MusclePencil Drawing Horses Anatomy

C LEI DO-OCCIPITALIS

CLEIDOMASTOIO

C IE IÜOC ERV1CALIS

c lei do brach i alis

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Responses

  • Addolorata
    Does the horse have an omotransversarius?
    8 years ago
  • ramona
    Where are the origin and insertion in a chicken wing?
    8 years ago
  • SANDRA
    Where is the nuchal muscle located?
    7 years ago
  • Angela
    Where is the brachiocephalicus muscle located on an animal?
    7 years ago
  • ubalda
    What does obliquus capitis cranialis do in horse?
    7 years ago
  • fikru
    Do horses have zygomatic?
    3 years ago
  • patrizia pisano
    How to draw wings on a horse?
    3 years ago

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