Veterinary Clinical Anatomy - glossary of directional and relational terms commonly used in veterinary anatomy

Abstract

The following terms are used to describe the position of individual body parts in relation to each other or to a body plane or axis. These terms are also used to describe the direction of movement or the perspective, particularly in diagnostic imaging (radiography, ultrasonography, computed tomography, magnetic resonance imaging, etc.). As all of these terms are relative, each is listed with its opposite whenever applicable.

In this article, I adhere to the anatomical terms published in the 5th edition of the Nomina Anatomica Veterinaria (NAV) in 2012. The Latin, Greek, or Old English roots are given in parentheses when possible. A brief description of the four major body planes used in veterinary clinical anatomy are provided at the end.

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Copyright © Christine M. King, 2020. All rights reserved.
VETERINARY)CLINICAL)ANATOMY)
)
Glossary(of(directional(and(relational(terms(commonly(used(in(veterinary(anatomy(
!
Christine!King!BVSc,!MANZCVS,!MVetClinStud!
!
!
The!following!terms!are!used!to!describe!the!position!of!individual!body!parts!in!relation!to!each!
other!or!to!a!body!plane!or!axis.!These!terms!are!also!used!to!describe!the!direction!of!movement!or!
the!perspective,!particularly!in!diagnostic!imaging!(radiography,!ultrasonography,!computed!
tomography,!magnetic!resonance!imaging,!etc.).!As!all!of!these!terms!are!relative,!each!is!listed!with!
its!opposite!whenever!applicable.!
!
In!this!article,!I!adhere!to!the!anatomical!terms!published!in!the!5th!edition!of!the!Nomina(
Anatomica(Veterinaria!(NAV)!in!2012.!The!Latin,!Greek,!or!Old!English!roots!are!given!in!
parentheses!when!possible.!A!brief!description!of!the!four!major!body!planes!used!in!veterinary!
clinical!anatomy!are!provided!at!the!end.!
!
Abaxial)vs.!axial!(L.!ab-,!away!or!from;!axis,!axle!or!pivot)!—!Furthest!from,!or!away!from,!the!
axis/axial!plane!of!interest.!For!example,!the!long!axis!of!the!horse’s!limb!runs!vertically!through!
the!center!of!the!limb,!so!the!abaxial!margins!of!the!proximal!sesamoid!bones!are!the!margins!
furthest!from!the!center!of!the!limb;!the!branches!of!the!suspensory!ligament!attach!in!part!to!the!
abaxial!margins!of!the!proximal!sesamoid!bones.!
!
Aboral)vs.!oral!(L.!ab-,!away!or!from;!oralis,!mouth)!—!Furthest!from,!or!away!from,!the!mouth.!For!
example,!ingesta!normally!flows!in!an!aboral!direction!through!the!digestive!tract.!
!
Afferent!vs.!efferent!(L.!ad(ferre,!carry!to)!—!Used!primarily!for!the!nervous,!circulatory,!and!
lymphatic!systems,!afferent!structures!conduct!flow!toward!the!central!components!of!the!system.!
For!example,!afferent!nerves!carry!sensory!signals!to!the!central!nervous!system!from!the!
periphery.!
!
Anterior!vs.!posterior!(L.!ante,!before)!—!Located!in!front!of!another,!or!at!the!front.!In!veterinary!
anatomy,!this!pair!of!terms!is!used!almost!exclusively!for!structures!on!the!head,!including!the!eye,!
lips,!and!inner!ear.!Where!these!terms!are!used!in!human!anatomy!to!describe!the!relative!position!
of!two!structures!in!the!standing!person!(front!vs.!back),!‘ventral’!and!‘dorsal’!are!generally!more!
appropriate!in!the!standing!animal.!
!
Apical)vs.!basilar)(L.!apex,!peak!or!tip)!—!The!apex!is!the!narrow!end!of!a!roughly!pyramidal!
structure!such!as!the!heart!or!the!proximal!sesamoid!bones!of!the!equine!limb.!For!example,!the!
ventricles!of!the!heart!narrow!to!a!rounded!point!to!form!the!apex!of!the!heart.!Apical!is!used!to!
describe!the!direction!or!aspect!toward!or!nearest!the!apex!of!the!structure.!
!
Apical!vs.!occlusal!(L.!apex,!peak!or!tip)!—!When!used!in!relation!to!the!teeth,!apical!describes!the!
direction!or!aspect!toward!or!nearest!the!terminal!portion!(tip!or!apex)!of!the!tooth!root.!
!
Axial)vs.!abaxial!(L.!axis,(axle!or!pivot)(—!Relating!to,!or!toward,!the!axis/axial!plane!of!interest.!For!
example,!the!long!axis!of!the!horse’s!limb!runs!vertically!through!the!center!of!the!limb,!so!the!axial!

Veterinary Clinical Anatomy — Glossary of directional and relational terms
Copyright © Christine M. King, 2020. All rights reserved.
margins!of!the!proximal!sesamoid!bones!are!the!margins!nearest!the!center!of!the!limb;!the!
intersesamoidean!ligament!connects!the!axial!margins!of!the!proximal!sesamoid!bones.!
!
Basilar)vs.!apical!(L.!basis,!foundation)!—!The!base!is!the!broad!end!of!a!roughly!pyramidal!
structure!such!as!the!heart!or!the!proximal!sesamoid!bones!of!the!equine!limb.!For!example,!the!
great!vessels!enter!the!atria!at!the!base!of!the!heart.!Basilar!is!used!to!describe!the!direction!or!
aspect!toward!or!nearest!the!base!of!the!structure.!(Basal!may!also!be!used!as!a!directional!term,!
although!it!is!most!often!used!when!describing!the!base!of!the!structure;!for!example,!the!great!
vessels!are!basal!structures!of!the!heart.)!
!
Bilateral!vs.!unilateral!(L.!bi-,!two;!lateralis,!side)!—!Both!sides,!in!relation!to!the!midline!of!the!
body.!Used!most!often!for!paired!structures,!such!as!the!limbs.!For!example,!bilateral!lameness!is!a!
gait!abnormality!involving!both!thoracic!or!pelvic!limb!pairs!(e.g.,(left!and!right!forelimbs)!or!a!
diagonal!limb!pair!(e.g.,(left!forelimb!and!right!hindlimb);!in!either!case,!the!lameness!involves!both!
sides!of!the!body,!left!and!right.!Similarly,!bilateral!blindness!involves!both!eyes.!
!
Buccal)vs.!lingual!or!palatal!(L.!bucca,(cheek)!—!Relating!to,!or!toward,!the!cheek.!For!example,!the!
buccal!surface!of!a!premolar!or!molar!tooth!faces!the!cheek;!the!opposite!side!of!the!tooth!faces!the!
tongue!(mandibular!teeth)!or!the!palate!(maxillary!teeth).!This!aspect!of!the!tooth!is!also!called!the!
vestibular!surface.!
!
Caudal)vs.!cranial!(L.!cauda,(tail)!—!Relating!to,!or!toward,!the!tail.!For!example,!the!lumbar!
vertebrae!are!located!caudal!to!the!thoracic!vertebrae.!On!the!proximal!limb!(above!the!carpus!or!
tarsus),!this!term!refers!to!the!back!of!the!limb,!facing!the!tail.!For!example,!the!‘hamstrings’!(the!
semimembranosus!and!semitendinosus!muscles)!are!located!on!the!caudal!aspect!of!the!thigh.!
From!the!carpus!or!tarsus!distally,!this!aspect!of!the!limb!is!termed!palmar!(forelimb)!or!plantar!
(hindlimb),!as!described!later.
!
Caudal)vs.!rostral!(L.!cauda,!tail)!—!When!referring!to!the!head,!toward!or!closest!to!the!tail.!For!
example,!the!ears!are!caudal!to!the!eyes!on!the!cat’s!head.!
!
Central!vs.!peripheral!(L.!centrum,!center)!—!Toward!or!near!the!center!of!the!body,!or!nearest!to!
the!center!of!an!organ!or!body!system.!For!example,!venous!blood!flows!in!a!central!direction!from!
the!peripheral!vasculature!to!the!heart!(the!center!of!the!cardiovascular!system).!
!
Contralateral!vs.!ipsilateral!(L.!contra-,!against;!lateralis,!side)!—!Opposite!side,!in!relation!to!the!
midline!of!the!body.!Used!most!often!for!paired!structures,!such!as!the!limbs.!For!example,!when!
describing!a!quadrupedal!gait,!the!trot!is!a!basic!locomotory!pattern!in!which!the!stride!alternates!
between!contralateral!limbs!(e.g.,!left!and!right!forelimbs).!
!
Cranial)vs.!caudal!(G.(kranion,(skull)!—!Relating!to,!or!toward,!the!head.!For!example,!the!thoracic!
vertebrae!are!located!cranial!to!the!lumbar!vertebrae.!On!the!proximal!limb!(above!the!carpus!or!
tarsus),!this!term!refers!to!the!front!of!the!limb,!facing!the!head.!For!example,!the!patella!is!located!
on!the!cranial!aspect!of!the!femoropatellar!joint.!From!the!carpus!or!tarsus!distally,!this!aspect!of!
the!limb!is!termed!dorsal,!as!described!later.!
!
Deep)vs.!superficial!(Old!English!dēop)!—!Relating!to!depth!or!distance!from!the!body!surface.!For!
example,!the!deep!digital!flexor!tendon!in!the!horse!is!deep!to!the!superficial!digital!flexor!tendon,!
which!lies!closer!to!the!skin.!
!

Veterinary Clinical Anatomy — Glossary of directional and relational terms
Copyright © Christine M. King, 2020. All rights reserved.
Dexter!vs.!sinister!(L.!dexter,!on!the!right)!—!Located!on!the!right!side!of!a!structure!or!the!body!as!
a!whole.!For!example,!in!ophthalmology!the!right!eye!is!often!abbreviated!as!OD,!oculus(dexter.!
Note:!dexter!and!sinister!pertain!to!the!right!and!left!sides!of!the!animal,!rather!than!those!of!the!
observer.!
!
Distal)vs.!proximal!(L.!distare,!distant)!—!Furthest!from,!or!away!from,!the!center!of!the!body!or!
other!point!of!origin.!When!applied!to!blood!vessels!or!nerves,!it!means!away!from!the!heart!or!
central!nervous!system,!respectively.!!In!the!limbs,!it!means!away!from!the!attached!end!and!
toward!the!free!end!of!the!limb.!For!example,!the!carpus!is!distal!to!the!elbow.!
!
Distal)vs.!mesial!(L.!distare,!distant)!—!Within!the!oral!cavity,!distal!means!furthest!from,!or!away!
from,!the!midline!or!center!of!the!entire!maxillary!or!mandibular!dental!arch;!toward!the!back!of!
the!mouth.!For!example,!the!distal!surface!of!a!premolar!or!molar!tooth!faces!the!back!of!the!mouth,!
and!the!distal!surface!of!an!incisor!tooth!faces!away!from!the!center!of!the!incisor!arcade.!
!
Dorsal)vs.!ventral!(L.!dorsum,(back)!—!Relating!to,!or!toward,!the!back!or!uppermost!surface!of!the!
body!in!the!standing!animal.!This!term!applies!to!the!head!as!well!as!to!the!neck,!body,!and!tail.!For!
example,!the!nuchal!ligament!runs!along!the!dorsal!surface!of!the!neck,!and!a!horse’s!forelock!
drapes!down!over!the!dorsal!surface!of!the!head!(specifically,!the!forehead!or!face).
!
Dorsal)vs.!palmar!or!plantar!(L.!dorsum,(back)!—!In!the!distal!limb!(below!and!including!the!
carpus/tarsus),!dorsal!means!relating!to,!or!toward,!the!front!of!the!limb.!(Proximal!to!the!
carpus/tarsus,!this!aspect!of!the!limb!is!termed!‘cranial’.)!The!use!of!dorsal!to!describe!this!aspect!of!
the!distal!limb!often!confuses,!as!it!is!derived!from!human!anatomy!and!translates!poorly!to!the!
quadruped.!Bearing!in!mind!that!the!dorsum!or!dorsal!surface!of!the!human!hand!is!the!back!of!the!
hand,!the!dorsal!surface!of!the!dog’s!distal!forelimb!is!the!surface!that!is!uppermost!when!the!dog!is!
running,!and!the!forelimb!is!reaching!forward.!Similarly,!the!dorsal!surface!of!the!distal!hindlimb!is!
uppermost!when!the!hindlimb!is!brought!forward!during!the!cranial!swing!phase!of!the!stride.!
!
Efferent!vs.!afferent!(L.!ex(ferre,!carry!away!or!out)!—!Used!primarily!for!the!nervous,!circulatory,!
and!lymphatic!systems,!efferent!structures!conduct!flow!away!from!the!central!components!of!the!
system.!For!example,!efferent!nerves!carry!motor!or!effector!signals!from!the!central!nervous!
system!to!the!periphery.!
!
External)vs.!internal!(L.!exter,!outer)!—!Relating!to,!or!toward,!the!exterior!or!outer!surface!of!a!
body!part.!This!term!is!primarily!used!for!the!walls!of!hollow!organs!and!body!cavities.!For!
example,!the!external!abdominal!oblique!muscle!lies!external!to,!or!over,!the!deeper!muscles!of!the!
abdominal!wall.!
!
Inferior!vs.!superior!(L.!inferus,!low)!—!Located!below!or!in!a!lower!position!in!relation!to!another.!
In!veterinary!anatomy,!this!pair!of!terms!is!used!almost!exclusively!for!structures!on!the!head,!
including!the!eye,!lips,!and!inner!ear.!Where!these!terms!are!used!in!human!anatomy!to!describe!the!
relative!position!of!two!structures!in!the!standing!person!(below!vs.!above),!‘caudal’!and!‘cranial’!
are!generally!more!appropriate!in!the!standing!animal.!
!
Intermediate!(L.!intermedius,!between!or!middle)!—!A!structure!positioned!between!two!others!
that!are!related!as!lateral!and!medial.!For!example,!in!the!equine!carpus!the!intermediate!carpal!
bone!lies!between!the!ulnar!carpal!bone!laterally!and!the!radial!carpal!bone!medially.!
!

Veterinary Clinical Anatomy — Glossary of directional and relational terms
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Internal)vs.!external!(L.!internus,!inner!or!inward)!—!Relating!to,!or!toward,!the!interior!or!inner!
surface!of!a!body!part.!This!term!is!primarily!used!for!the!walls!of!hollow!organs!and!body!cavities.!
For!example,!the!internal!abdominal!oblique!muscle!lies!internal!to,!or!under,!the!external!
abdominal!oblique!muscle!of!the!abdominal!wall.!
!
Ipsilateral!vs.!contralateral!(L.!ipse,!self;!lateralis,!side)!—!Same!side,!in!relation!to!the!midline!of!
the!body.!Used!most!often!for!paired!structures,!such!as!the!limbs.!For!example,!when!describing!a!
quadrupedal!gait,!the!pace!is!a!variation!of!the!trot!in!which!the!ipsilateral!forelimb!and!hindlimb!
(e.g.,(left!forelimb!and!left!hindlimb)!move!in!unison.!Ipsilateral!should!not!be!confused!with!
unilateral,!which!simply!means!one!side.!Ipsilateral!describes!the!relationship!of!two!separate!
structures!or!processes!as!being!located!on!the!same!side!of!the!body,!whereas!unilateral!describes!
only!one!structure!or!process!(e.g.,!unilateral!lameness).!
!
Labial)vs.!lingual!or!palatal!(L.!labium,(lip)!—!Relating!to,!or!toward,!the!lips.!For!example,!the!labial!
surfaces!of!the!incisor!and!canine!teeth!face!the!lips;!the!opposite!side!of!these!teeth!face!the!tongue!
(mandibular!arcade)!or!palate!(maxillary!arcade).!This!aspect!of!the!tooth!is!also!called!the!
vestibular!surface.!
!
Lateral)vs.!medial!(L.!lateralis,(side)!—!Relating!to,!or!toward,!the!side!of!the!animal;!furthest!or!
away!from!the!midline!of!the!body.!For!example,!the!dog’s!outermost!or!fifth!digit!is!located!lateral!
to!the!other!four!digits.!
!
Lingual)vs.!buccal,!labial,!or!vestibular)(L.!lingua,(tongue)!—!Relating!to!the!tongue.!For!example,!
the!lingual!surface!of!a!mandibular!premolar!or!molar!tooth!faces!the!tongue;!the!opposite!side!of!
the!tooth!faces!the!cheek.!This!term!also!applies!to!the!mandibular!incisor!and!canine!teeth;!the!
opposite!side!of!these!teeth!faces!the!lower!lip.!Palatal!is!used!instead!of!lingual!when!referring!to!
the!corresponding!surfaces!of!the!maxillary!teeth!(see!definition!below).!
!
Medial)vs.!lateral!(L.!medius,!middle)!—!Relating!to,!or!toward,!the!midline!of!the!body.!For!
example,!the!dog’s!dewclaw!or!first!digit!is!located!on!the!medial!aspect!of!the!limb.!
!
Mesial)vs.!distal!(G.!mesos,!middle)!—!Within!the!oral!cavity,!mesial!means!relating!to,!or!toward,!
the!midline!or!center!of!the!entire!maxillary!or!mandibular!dental!arch;!toward!the!front!of!the!
mouth.!For!example,!the!mesial!surface!of!a!premolar!or!molar!tooth!faces!the!front!of!the!mouth,!
and!the!mesial!surface!of!an!incisor!tooth!faces!toward!the!center!of!the!incisor!arcade.!
!
Middle!(Old!English.!middel)!—!A!structure!positioned!between!two!others!that!are!related!as!
cranial!and!caudal,!dorsal!and!ventral,!superficial!and!deep,!external!and!internal,!or!proximal!and!
distal!to!each!other.!For!example,!the!middle!(second)!phalanx!is!located!between!the!proximal!
(first)!and!distal!(third)!phalanges.!The!separate!and!distinct!use!of!intermediate!for!a!position!
between!lateral!and!medial!is!not!inviolate,!however.!The!second!of!the!three!patellar!ligaments!in!
the!equine!stifle,!the!middle!patellar!ligament,!lies!between!the!lateral!and!medial!patellar!
ligaments.
!
Occlusal!vs.!apical)(L.!occlus-,!close!or!block)!—!Pertaining!in!general!to!the!surfaces!of!opposing!
teeth!that!meet!when!the!jaws!are!closed;!more!specifically,!it!pertains!to!the!masticating!surfaces!
or!‘tables’!of!the!premolar!and!molar!teeth,!and!in!horses!the!incisors!as!well.!
!

Veterinary Clinical Anatomy — Glossary of directional and relational terms
Copyright © Christine M. King, 2020. All rights reserved.
Oral)vs.!aboral!(L.!oralis,(mouth)!—!Relating!to,!or!toward,!the!mouth.!For!example,!ingesta!moves!
in!an!oral!direction!from!the!ruminoreticulum!to!the!mouth!when!a!cow!regurgitates!in!the!normal!
process!of!rumination!(to!‘chew!its!cud’).!
!
Palatal)vs.!buccal,!labial,!or!vestibular!(L.!palatum,!roof!of!the!mouth)!—!Relating!to!the!palate.!For!
example,!the!palatal!surface!of!a!maxillary!premolar!or!molar!tooth!faces!the!palate;!the!opposite!
side!of!the!tooth!faces!the!cheek.!This!term!also!applies!to!the!maxillary!incisor!and!canine!teeth;!
the!opposite!side!of!these!teeth!faces!the!upper!lip.!Lingual!is!used!instead!of!palatal!when!referring!
to!the!corresponding!surfaces!of!the!mandibular!teeth!(see!definition!above).!
!
Palmar)vs.!dorsal!(L.!palma,!palm!of!the!hand)!—!In!the!distal!forelimb!(below!and!including!the!
carpus),!palmar!means!relating!to,!or!toward,!the!back!of!the!limb!or!the!underside!of!the!foot.!
(Proximal!to!the!carpus,!this!aspect!of!the!limb!is!termed!‘caudal’.)!This!term!is!derived!from!human!
anatomy,!the!palmar!surface!of!the!hand!extending!from!the!fingertips!to!the!wrist.!Thus,!the!
palmar!surface!of!the!dog’s!distal!forelimb!includes!the!digital!pads!and!the!back!of!the!limb!up!to,!
and!including,!the!carpus.!In!ungulates!(horses,!cattle,!small!ruminants,!camelids),!this!aspect!of!the!
hoof!is!also!called!the!solar!surface!in!both!the!fore-!and!hindlimb!(see!below).!
!
Parietal!vs.!visceral!(L.!pariet,!wall)!—!Pertaining!to!the!wall!of!a!hollow!organ!or!body!cavity.!For!
example,!the!parietal!surface!of!the!pleura!lines!the!thoracic!wall,!whereas!the!visceral!surface,!
which!is!a!reflection!of!the!parietal!pleura,!covers!the!contents!(viscera)!of!the!thoracic!cavity.!
!
Peripheral!vs.!central!(G.!periphereia,!circumference)!—!Toward!or!near!the!body!surface,!or!
furthest!from!the!center!of!an!organ!or!body!system.!For!example,!arterial!blood!flows!from!the!
heart!(the!center!of!the!cardiovascular!system)!to!the!peripheral!vasculature.!
!
Plantar)vs.!dorsal!(L.!planta,!sole!of!the!foot)!—!In!the!distal!hindlimb!(below!and!including!the!
tarsus),!plantar!means!relating!to,!or!toward,!the!back!of!the!limb!or!the!underside!of!the!foot.!
(Proximal!to!the!tarsus,!this!aspect!of!the!limb!is!termed!‘caudal’.)!This!term!is!derived!from!human!
anatomy,!in!which!the!plantar!surface!of!the!foot!extends!from!the!underside!of!the!toes!to!the!heel.!
Thus,!the!plantar!surface!of!the!dog’s!distal!hindlimb!includes!the!digital!pads!and!the!back!of!the!
limb!up!to,!and!including,!the!tarsus.!In!ungulates!(horses,!cattle,!small!ruminants,!camelids),!this!
aspect!of!the!hoof!is!also!called!the!solar!surface!in!both!the!fore-!and!hindlimbs!(see!below).!
!
Posterior!vs.!anterior!(L.!post,!after)!—!Located!behind!another,!or!at!the!back.!In!veterinary!
anatomy,!this!pair!of!terms!is!used!almost!exclusively!for!structures!on!the!head,!including!the!eye,!
lips,!and!inner!ear.!Where!these!terms!are!used!in!human!anatomy!to!describe!the!relative!position!
of!two!structures!in!the!standing!person!(back!vs.!front),!‘dorsal’!and!‘ventral’!are!generally!more!
appropriate!in!the!standing!animal.!
!
Proximal)vs.!distal!(L.!proximus,!near!or!nearest)!—!Relating!to,!or!toward,!the!center!of!the!body!or!
other!point!of!origin.!When!applied!to!blood!vessels!or!nerves,!it!means!nearer/toward!the!heart!or!
central!nervous!system,!respectively.!In!the!limbs,!it!means!nearer/toward!the!attached!end!and!
away!from!the!free!end!of!the!limb.!For!example,!the!elbow!is!proximal!to!the!carpus.!
!
Rostral)vs.!caudal!(L.!rostrum,!beak)!—!When!referring!to!the!head,!rostral!means!relating!to,!or!
toward,!the!nose!and!mouth.!For!example,!the!eyes!are!rostral!to!the!ears!on!the!cat’s!head;!and!the!
nasolacrimal!duct!normally!drains!ocular!secretions!in!a!rostral!direction,!from!eye!to!nostril.!
!

Veterinary Clinical Anatomy — Glossary of directional and relational terms
Copyright © Christine M. King, 2020. All rights reserved.
Sinister!vs.!dexter!(L.!sinister,!on!the!left)!— Located!on!the!left!side!of!a!structure!or!the!body!as!a!
whole.!For!example,!in!ophthalmology!the!left!eye!is!often!abbreviated!as!OS,!oculus(sinister.!Note:!
sinister!and!dexter!pertain!to!the!left!and!right!sides!of!the!animal,!rather!than!those!of!the!
observer.!
!
Solar!(L.!solum,!bottom)!—!In!ungulates!(horses,!cattle,!small!ruminants,!camelids),!solar!is!used!for!
the!palmar/plantar!surface!of!the!hoof,!specifically!the!surface!in!contact!with!the!ground!when!the!
animal!is!standing.!
!
Superficial)vs.!deep)(L.!superficies,!surface)!—!Relating!to!depth!or!distance!from!the!body!surface.!
For!example,!the!superficial!digital!flexor!tendon!in!the!horse!is!closer!to!the!skin!and!thus!lies!
superficial!to!the!deep!digital!flexor!tendon.!
!
Superior!vs.!inferior!(L.!super,!above)!—!Located!above!or!in!a!higher!position!in!relation!to!
another.!In!veterinary!anatomy,!this!pair!of!terms!is!used!almost!exclusively!for!structures!on!the!
head,!including!the!eye,!lips,!and!inner!ear.!Where!these!terms!are!used!in!human!anatomy!to!
describe!the!relative!position!of!two!structures!in!the!standing!person!(above!vs.!below),!‘cranial’!
and!‘caudal’!are!generally!more!appropriate!in!the!standing!animal.!
!
Unilateral!vs.!bilateral!(L.!unus-,!one;!lateralis,!side)!—!One!side,!in!relation!to!the!midline!of!the!
body.!Used!most!often!for!paired!structures,!such!as!the!limbs.!For!example,!unilateral!lameness!is!a!
gait!abnormality!involving!only!one!limb.!Similarly,!unilateral!blindness!involves!only!one!eye.!
!
Ventral)vs.!dorsal)(L.!venter,!belly)!—!Relating!to,!or!toward,!the!belly!or!underside!of!the!body!in!
the!standing!animal.!This!term!applies!to!the!head,!neck,!body,!and!tail.!For!example,!the!trachea!
extends!along!the!ventral!aspect!of!the!neck!(deep!to!the!skin);!and!the!mandibles!are!located!on!the!
ventral!aspect!of!the!head.!
!
Vestibular!vs.!lingual!or!palatal)(L.!vestibulum,!entrance!court!or!antechamber)!—!In!describing!the!
teeth,!the!surface!of!a!tooth!that!is!directed!outward,!toward!the!vestibule!of!the!mouth.!This!aspect!
is!also!called!the!buccal!(premolars,!molars)!or!labial!(incisors,!canines)!surface.!
!
Visceral!vs.!parietal!(L.!viscera,!internal!organs!of!the!body)!—)Pertaining!to!the!internal!organs.!
For!example,!the!visceral!surface!of!the!pleura!covers!the!contents!(viscera)!of!the!thoracic!cavity,!
whereas!the!parietal!surface!lines!the!thoracic!wall.!
!
Body)Planes)
!
The!four!major!body!planes!used!in!veterinary!clinical!anatomy!are!dorsal,!median,!sagittal,!and!
transverse.!These!terms!are!primarily!used!in!diagnostic!imaging!to!describe!the!orientation!of!the!
projection!(‘view’)!or!window!(‘slice’),!particularly!in!ultrasonography,!computed!tomography,!and!
magnetic!resonance!imaging.!
!
Dorsal)plane!—!Any!plane!that!runs!parallel!to!the!dorsal!surface!of!the!head,!neck,!body,!or!tail.!
!
Median)plane!—!This!plane!divides!the!head,!neck,!body,!or!tail!lengthwise!down!the!middle!
(median)!into!broadly!symmetrical!halves,!left!and!right.!For!a!limb,!this!plane!may!best!be!referred!
to!as!axial,!as!it!does!not!result!in!halves!that!are!symmetrical.!
!

Veterinary Clinical Anatomy — Glossary of directional and relational terms
Copyright © Christine M. King, 2020. All rights reserved.
Sagittal)plane!—!Any!plane!that!runs!parallel!to!the!median!plane;!in!the!limb,!parallel!to!the!long!
axis!of!the!limb.!
!
Transverse)plane!—!Any!plane!that!transects!the!head,!neck,!body,!tail,!or!limb!perpendicular!to!
its!long!axis;!simply!put,!a!cross-section!of!the!structure.!
!
In!the!three!dimensions!of!the!living!animal,!the!dorsal,!median/sagittal,!and!transverse!planes!are!
all!at!90°!to!one!another,!forming!a!three-dimensional!+.!
!
!
!
Author’s note: This chapter was written by me (Christine M. King) on commission and completed on 03 May
2018. This chapter is some of my best work to date, yet it was going to be credited to others—an act of
intellectual dishonesty I refuse to support. I am the author of this original work. I retain the copyright, and all
rights are reserved.