2 Axial Skeleton2.1 Skull3 Joints and also Ligaments3.2 Cervical Spine3.2.1 Joints3.3 Thoracic Spine (T1-T18)3.4 Costovertebral Joint3.5 Lumbar Spine3.5.1 Joints4 Myology and Neurology4.1 muscle of the Head4.1.2 Ear4.1.7 muscle of the Hyoid Apparatus and Larynx
Introduction
Equine anatomy refers to the gross and also microscopic anatomy of horses and also other equids (donkeys, and zebras).
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This web page introduces the Anatomy of equine Spine and also Head.
Axial Skeleton
The axial skeleton is composed of the skull, vertebral column, sternum, and ribs. Lot of sternebrae fuse to form one bone, attached come the 8 "true" pairs of ribs, out of a full of 18.<1>
The vertebral column has 54 bones:
7 cervical vertebrae: has the atlas (C1) and axis (C2)18-19 thoracic vertebrae5-6 lumbar vertebrae5 sacral vertebraeIn details breeds, there may be variations in these numbers.<3>
Skull
The skull contains the brain and the most necessary organs that sense.
CraniumThe Roof that the cranium is made up of frontal and also parietal bones.
The Floor is made up of sphenoid bone.
The cranium is composed of 5 orbit regions:
FrontalLacrimalPalatineSphenoidZygomaticInterparietal bone: only discovered in horse and cat.
The orbit is finish in horse and ruminants while the is incomplete in carnivores however completed through the orbit ligament.
The lacrimal fossa collection tears and also sends them through lacrimal canal right into the nasal cavity.
Bones in the steed Skull
There are 34 bones and most that them room flat. During the birth process, these bones overlap and allow the skull to compress as much as feasible to allow for parturition.
The 14 major bones are:<1>
Incisive bone (premaxillary): component of the upper jaw; wherein the incisors attachNasal bone: consist of the nasal cavityMaxillary bone: a large bone that consists of the roots of the molarsMandible: lower section of the jaw; biggest bone in the skullLacrimal bone: contains the nasolacrimal duct, which carries fluid from the surface of the eye, to the noseFrontal bone: create the forehead of the horseParietal bone: extends native the forehead to the back of the skullOccipital bone: develops the joint in between the skull and the first vertebrae that the neck (the atlas)Temporal bone: includes the eternal acoustic meatus, which transmits sound from the ear come the cochlea (eardrum)Zygomatic bone: attaches come the temporal bone to form the zygomatic arch (cheekbone)Palatine bone: forms the back of the tough palateSphenoid: developed by blend of the foetal basisphenoid and presphenoid bones, in ~ the base of the skull. Deserve to become broken in horses that behind over backwardsVomer: forms the peak of the within of the nasal cavityPterygoid: small bone attached to the sphenoid that extends downwardCavitiesThe equine skull is composed of 4 cavities:
The cranial cavity: Protects and encloses the brain, supports feeling organs. The cranium is composed of a roof comprised of the frontal and parietal bones and also a floor consisted of of the sphenoid boneThe orbit cavity: has 5 orbits: frontal, lacrimal, palatine, sphenoid and also zygomatic. That protects and also surrounds the eye.<4> Horses have both monocular and binocular vision:Monocular vision: The horse deserve to see objects through one eye. This means that the mind receives two images simultaneouslyBinocular vision: The horse can focus with both eyes as with humans and also the brain receives only one signalThe oral cavity: A passage right into the respiratory and also digestive systemThe nasal cavity: has bone the protects the mucous membrane indigenous inspired warmth airForamina the the Skull and the structures Passing Through| Infra-orbital foramen | Infra-orbital nerve. CNV |
| Maxillary foramen | |
| Cribriform foramen | Olfactory nerve. CNI |
| Optic canal | Optic nerve. CNII |
| Orbital fissure | CNVII, IV, V and also VI (ophthalmic division) |
| Round foramen | CNV (maxillary division) |
| Oval foramen | CNV (mandibular division) |
| Foramen lacerum | Internal carotid artery CN V3 (horse and also pig) |
| Internal acoustic meatus | CNVIII |
| Jugular foramen | CNIX, X, XI |
| Stylomastoid foramen | CNVII |
| Mandibular foramen | CNV (mandibular alveolar nerve) |
| Mental foramen |
Joints and Ligaments
Joints and Ligaments of the Skull
Mandibular symphysisHyoid apparatus - consists of 3 joints:Tympanohyoid cartilage- skull (syndesmosis)Interhyoid joints (synovial)
Atlanto-Occipital Joint
A condylar, modified synovial hinge joint. The articulating surfaces are the occipital condyles and also the cranial articular surfaces of the atlas (C1). There are three thickenings that strengthen the spacious joint capsule: Dorsal, Ventral, Lateral. The transverse atlantal ligament holds the dens that the axis versus the ventral arch that the atlas.<1>
Atlanto-Axial JointA pivot joint in between the atlas and also the saddle shaped surface ar of the axis (C2), i m sorry extends top top the dens. It has actually a loose joint capsule. The apical ligament that dens connects the apex of the dens to the occipital bone. Motion at this joint has rotation of the atlas and also head upon the axis and some accessory lateral flexion.<1> Rotation at this joint renders up 73 percent that cervical rotation.<6>
Cervical Spine C3-C4A planar, extensive, oval shaped joint that is obliquely oriented in transverse plane. The cranial articular processes challenge dorsomedially and also the caudal articular processes face ventrolaterally. Spinous procedure height increases caudally from C6. Lateral flexion is the primary motion at this joints (25-45 degrees each share - C1/C2 only has actually 3.9 degrees of lateral flexion).<6>
LigamentsThoracic Spine (T1-T18)
Articular processesCaudal articular processes challenge ventrally and also are positioned at the base of the spinous process. The cranial articular processes room oval facets ~ above the arch the the vertebra and face dorsally. Each thoracic vertebrae has a pair that costal facets ~ above the dorsal human body (except the last) forming the costal fovea.<1>
Anticlinal vertebrae: This is the suggest in the caudal thoracic vertebral obelisk at i m sorry the anatomic attributes of the vertebra begin to change.<7> This normally occurs in ~ the 13th vertebra in horses.
Motion:
Flexion - many flexion occurs at T17/T18; least flexion wake up at T3-T9Rib NeckHas 2 converse facets: Cranial and Caudal
Rib 1 attaches come C7, T1 and the linked IV disc
Motion: rotation that the rib, i beg your pardon is greater caudally
Costovertebral Joint
JointsThe costovertebral joints have actually two unique articulations in between most ribs and also the vertebral column:<1>
Head of the rib: Cranial and caudal costal facets of adjacent vertebrae; a ball and also socket synovial jointTubercle of the rib: Transverse process of vertebrae; a plane synovial jointLigamentsLumbar Spine
JointsHorses usually have actually 6 lumbar vertebrae (L1-L6), yet some arabian horses only have actually 5 (L1-L5).<1>
Articular processesCranial articular processes space fused through mammillary processes. They space concave dorsally and mostly in sagittal alignment. Caudal processes space convex ventrally and correspond through the convexity that the cranial articular processes. They are identified from the last thoracic vertebra by the absence of costal facets.<1>
Motion: The lumbar spine and caudal thoracic spine are the the very least mobile regions of a horse"s back.<8> Lateral flexion and rotation is very restricted especially at L4-L6 as result of intertransverse joints.<1>
Ligaments the Thoraco-Lumbar SpineLumbosacral Joint
The cranial articular procedure of the first sacral vertebra room concave and also face dorsomedially.
Motion: Flexion and Extension - 23.4 degrees<9>
Sacrum
The sacrum consists of fused sacral vertebrae and also has dorsal and ventral sacral foramina.
<10>
Myology and Neurology
Muscles the the Head
Muscles the the FaceThe muscles of face expressions are innervated by the engine fibers the CNVII (facial nerve).<1>
| M. Levator labii maxillaris | Lacrimal, Zygomatic and Maxillary bones | The maxillary lip | Elevates the Maxillary lip | |
| M. Levator nasolabialis | Nasal and also Frontal bones | The lateral wing of nostril The maxillary lip | Elevates and also retracts the angle of the mouth | |
| M. Zygomaticus | The fascia extending the Masseter | The commissure that the lips | ||
| M. Buccinator | Maxilla and also Mandible | Flattens the cheeks and thus presses food in between the teeth | ||
| M. Depressor labii mandibulars | The alveolar border that the Mandible | The mandibular lip | Depresses and also retracts the mandibular lip | |
| M. Orbicularis oris | The sphincter muscle of the skin and the muscle of the lips Corner the the mouth | Into the lips as it surrounds the mouth | Closes the mouth | |
| M. Risorius | Part that M. Cutaneous faciei | The edge of the mouth | Retracts the angle of the mouth | |
| M. Dilator naris | Alar cartillage | Alar cartillage | Dilates the nostril | |
| M. Lateralis nasi | Dorsal part | Nasal bone | Parietal cartilage | Dilates the nostril and nasal vestibule |
| Ventral part | Nasal process of Incisive bone | Lateral wall of the nasal vestibule | ||
| M. Caninus | Maxilla close come the rostral extreme of the face crest | Lateral wing of the nostril | Dilates the nose laterally | |
| M. Levator nasolabialis | Frontal and also Nasal bones | Lateral wing of the nostril | Elevates the maxillary lip and also the commissure of the mouth Dilates the nostril |
The ear is an organ of hearing and also balance. It consists of the outer, middle, and also inner ear.
Outer EarThe outer ear includes:<1>
Ear canalCartilage: Cartilages the the ear collect and transmit sound to the necessary organ of hearing within the temporal bone. In stimulate to attain this, they (especially the concha) must move.<1>
The muscles of external ear:<1>
RostralDorsalCaudalVentralThere are 3 cartilages:<1>
Conchal: forms the frame of the part of the ear which stands erect. It has actually a large vertical opening on one side to receive sound, and also is attached below to the annular cartilageAnnular: A little ring that gristle associated to the auditory procedure of the petrous temporal boneScutiform: A small, flat and somewhat triangular cartilaginous plate located in former of the base of concha, come which the is attachedMiddle EarThe middle ear includes:<1>
EardrumSmall, air-filled room containing 3 tiny bones: the hammer, anvil, and also stirrup. It likewise includes 2 muscles: the oval window, and also the eustachian tube.Inner EarThe inner ear is a complicated structure that has the cochlea and the vestibular system.<11>
Muscles that MasticationThe muscles of mastication space innervated by the mandibular branch that trigeminal nerve CNV.<1>
| M. Masseter | The zygomatic arch and the facial crest | The lateral border of the ramus the the mandible | Closes the mouth |
| M. Temporalis | The temporal fossa and also the temporal crest | The coronoid process of the mandible | Closes the mouth (to advanced the mandible) |
| M. Pterygoideus medialis | The crest formed by the pterygoid procedures of the basisphenoid and the palatine bones | The medial surface ar of the ramus that the mandible | |
| M. Pterygoideus lateralis | The pterygoid procedure of the sphenoid bone | Rostral border the the condyle that the mandible | Draws and moves the mandible rostrally |
| M. Digastricus | The jugular process of occipital bone | Medial surface ar of the ventral border the the molar part of the body of the mandible | Opens the mouth |
| M. Occipitomandibularis | The jugular process | The caudal border of the ramus the the mandible |
The horse tongue is comprised of twelve different muscles<14> including styloglossus, genioglossus and also hyoglossus. This muscles space covered through mucosa top top the sides and also underneath.<1>
Action: prehension, mastication (i.e. Chewing)
Innervation: Hypoglossus (CNXII)
Muscles that Pharynx and also Soft palate.| INTRINSIC MUSCLES | |||||
| M. Tensor veli palatini | Muscular process of the petrous part of the temporal bone, pterygoid bone, and also lateral lamina the the hear tube | Palatine aponeurosis | Retracts the soft palate far from the dorsal pharyngeal wall, expanding the nasopharynx and also slightly depressing it ventrad throughout inspiration | Mandibular branch that the trigeminal nerve | |
| M. Levator veli palatini | Muscular process of the petrous component of the temporal bone and also the lateral lamina the the listening tube and passes follow me the lateral wall of the nasopharynx | Soft palate dorsal come the glandular layer | Elevates the soft palate throughout swallowing | Pharyngeal branch the the Vagus nerve | |
| M. Palatinus | Caudal aspect of the palatine aponeurosis | Caudal cost-free margin of the soft palate | Shortens the soft palate and depresses it in the direction of the tongue | ||
| M. Palatopharyngeus | Palatine aponeurosis and from the palatine and pterygoid bones | Upper leaf of the thyroid cartilage | |||
| M. Stylopharyngeus | Rostral | Medial surface of the rostral end of the Stylohyoid bone | Pharyngeal raphe | Pharyngeal constrictor | Glossopharyngeal nerve |
| Caudal | Medial element of the caudal third of the Stylohyoid bone | Dorsolateral wall of the pharynx | Pharyngeal dilator | ||
| EXTRINSIC MUSCLES | |||||
| M. Genioglossus | Median aircraft of the Tongue | Oral surface ar of the Mandible | Protracts the tongue | Hypoglossal nerve | |
| M. Geniohyoideus | Medial surface of the Mandible | Basihyoid bone | Protrudes the tongue | ||
| M. Thyrohyoideus | Lateral lamina the the Thyroid cartilage | Caudal facet of the thyrohyoid bone | Moves the larynx rostrad | ||
| M. Hyoglossus | Hyoid bones | Median plane of the dorsum that the tongue | Retracts and also depresses the base of the tongue | ||
| M. Hyoepiglotticus | |||||
| M. Styloglossus | Lateral facet of the stylohyoid bone | Tip of the tongue | Retraction the the tongue | ||
| M. Sternohyoideus | Sternal manubrium | Basihyoid bone and also lingual process of the hyoid apparatus | Caudal traction | Branches the the an initial and second cervical nerves | |
| M. Sternothyroideus | Caudolateral element of the thyroid cartilage |
Muscles the the hyoid apparatus and larynx room innervated by CNX.
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The hyoid apparatus has muscular connections from the throat to the forelimbs, shoulder, and sternum. Sternohyoid and omohyoid provide a direct connection from the hyoid device to the shoulder the the equine via the ventral neck. The tongue connects to the hyoid apparatus. Tiny muscles of the hyoid apparatus affix to the TMJ and also the poll and also the TMJ articulates through the hyoid apparatus.<17><18>
LarynxIntrinsic muscles:
Cricoarytenoideus dorsalis - kidnapping of arytenoids and also tensing of vocal cordsThyroarytenoideus - adduction that arytenoidsArytenoideus transversus - adduction that arytenoids