Veterinary Anatomy - The Thoracic Limb

begawayu's version from 2016-10-03 21:17

The Thoracic Limb - Components

ComponentsMade up of
Thoracic GirdleScapula, Coracoid, Clavicle
Forearm/AntebrachiumRadius & Ulna
ManusCarpus, Metacarpus & Digits

The Thoracic Limb: Thoracic Girdle

Scapulafusion with coracoid in mammals forms coracoid process; separate in birds
flat bone
has 2 surfaces - medial & lateral
has 3 borders - cranial, caudal & dorsal
has 3 angles - cranial, caudal & ventral
Claviclemay be fibrous, cartilagenous; reduced or absent
absent in horses & ox
found in the dog as a vestigial in the brachiocephalic muscle

The Thoracic Limb: Thoracic Girdle -> Scapula - Properties

Medial surfacesubscapular fossa & facies serrata
Lateral surfacedivided by spine; supraspinous (cranial) & infraspinous (caudal)
Dorsal borderscapular cartilage
Caudal borderattachment of teres minor & major m.
Ventral anglehas a neck & glenoid cavity for articulation with humerus
Scapula Spinehas a thickened ventral projection called acromium process

The Thoracic Limb: Thoracic Girdle - Scapula > Scapula Spine - Species differences

SpeciesAcromium process
Dogflattened sideways to form hamate process
Catssuprahamate process
Horsedoes NOT exist
Bovinevery prominent

The Thoracic Limb: Thoracic Girdle > Scapula - Spine & Fossas

Subscapular fossainsert. subscapularis m.
Facies serratainsert. serratus ventralis m.
Supraspinousinsert. supraspinatus m.
Infraspinousorigin infraspinous m.
Scapular cartilageinsert. rhomboideus m.
Scapular spineinsert. trapezius m. & scapular part of deltoid m.
Acromial processorigin acromial part of deltoid m.
Supraglenoid tubercleorigin. biceps brachii m
Glenoid cavityarticulates with humerus

The Thoracic Limb: Humeral/Shoulder Joint - Ball&Socket/Diarthrotic

Glenoid cavity of scapula & head of humerus
Quite stable & no collateral ligaments are associated with it
Supported by the glenohumeral ligament which attaches the glenoid cavity to the tuberosities of the humerus
Tendons of muscles that attach around the joint will act to support the joint & give stability
These muscles are
I Supraspinatus
II Infraspinatus
IV The biceps brachii

The Thoracic Limb: Arm/Brachium

Proximal extremitythe head, greater & lesser tuberosities
Shaftlateral & medial surfaces
Distal extremitycalled the condyle

The Thoracic Limb: Arm/Brachium - Humeral proximal extremity

FeaturePropertyPurposeM.InnervationM.Blood supplyAction
Headhemisperical & directed mediallyarticulation with the glenoid cavity---
Neck-connection with the shaft---
Greater tuberclelarge process craniolateral to the headinsert. deep pectoralcaudal pectoral n.-retract (flex) & adduct shoulder
-insert. supraspinatous m.suprascapular n.-extend & stabilize
Lesser tubercleprocess on the medial aspect of the headdeep pectoralcaudal pectoral n.-retract (flex) & adduct shoulder
-insert. suprasinatous m.suprascapular n.subscapula a., caudal circumflex a.extend & stabilize shoulder
-insert. coracobrachialis m.musculocutaneous n.brachialis a., cranial circumflexflex shoulder

The Thoracic Limb: Arm/Brachium - Humeral proximal extremity - Species differences

SpeciesProximal extremity
Ruminantintertuberal groove for passage of biceps brachii tendon
Horseshas an intermedediate tuberosity
Dogsnot very prominent

The Thoracic Limb: Arm/Brachium - Humeral shaft

SurfaceFeaturePurposeM.InnervationM.Blood SupplyAction
Lateralmusculospiral grooveinsert. brachialis m.musculocutaneous n.-flex elbow
tricipital line----
deltoid tuberosityinsert. of deltoid m.axillary n.-flex shoulder
Medialteres major tuberosityteres major m.axillary n.subscapula a., brachialis a, cranial circumflex a.flex shoulder

The Thoracic Limb: Arm/Brachium - Humeral distal extremity/condyle

FeaturePropertiesPurposeM.InnervationM.Blood SupplyAction
Groovescranial/radialarticulates with radius---
caudal/olecranonarticulates with olecranon process of ulna---
Articular surfacestrochlear (larger, medial)----
capitulum (smaller, lateral)----
Epicondylelateral/extensor epicondyleorigin. extensor carpi radialis m.radial n.transverse cubital a.extend carpal joint & flex elbow
-origin common digital extensor m. (humeral head)radial n.transverse cubital a.extend digits
-origin lateral digital extensor m. (on/near)radial n.transverse cubital a.extend digits
-origin lateral ulnar m.radial n.lateral radial a.flex carpal
-origin supinator m. (carnivores)radial n.-supinates paw
medial/flexor epicondyleorigin pronator teres m.median n.-pronates paw
-origin flexor carpi radialis m.median n.brachial a.flex carpus
-origin flexor carpi ularis m. (humeral head)ulnar n.-flex carpus
-origin superficial digital flexor m .ulnar n.-flex digits & carpus
Epicondylar crestlateral & medial----

The Thoracic Limb: Arm/Brachium - Humeral distal extremity/condyle – Species differences

SpeciesDistal extremity
Cats3 fossae
supracondylar foramen on the medial epicondyle for passage of median n. & brachial vessels
Dogssupratrochlear foramen bet. the olecranon process & radial fossa

The Thoracic Limb: Cubital/Elbow Joint - Ginglymus/Flexion&Extension

Distal end of humerus - Trochlear capitulum; articulates with the proximal end of radius (fovea capitis) & proximal end of the ulna (Trochlear notch)
Thin joint capsule is supported laterally by collateral ligaments
Caudally it is supprted by the tendon of muscles that attach to the olecranon process (Triceps brachii m.)
2 collateral ligaments;
I Lateral - lateral humeral epicondyle & tuberosity
II Medial - medial humeral epicondyle & tuberosity
Divided into deep & superficial parts

The Thoracic Limb: Forearm/Antebrachium > Radius

FeaturePropertyDetailPurposeM.InnervationM.Blood SupplyAction
2 surfacescranial-----
2 extremitiesproximalfovea capitis for articulation with humerus condyle----
-radial tuberosity (distal to fovea capitis, medial)insert. Bicep brachii m.musculocutaneous n.brachial a.flex elbow
distalmedial styloid process (bigger) & intermeadiate syloid process----
-3 ridges on cranial surfacepassage of extensor carpi radialis, common digital extensor & tendon of abductor digiti longus---
-medial & lateral tuberositiesinsert. of collateral ligaments---

The Thoracic Limb: Forearm/Antebrachium > Ulna

PopertyFeature PurposeM.InnervationM.Blood SupplyAction
Proximal extremityolecranoninsert. triceps m.radial n.-extend elbow
anconeal process----
Distal extremitylateral styloid process----

The Thoracic Limb: Radioulna Joint/Syndesmosis

Bet. the radius & ulna
Forms interosseous spaces
Joined by interosseous ligament which ossifies with age

The Thoracic Limb: Forearm/Antebrachium > Radius & Ulna - Species differences

Horseulna smaller than radius
proximal interosseous space only
Dogulna relatively large
radius & ulna not joined (pigs as well)
capable of pronation & supination
Oxproximal & distal interosseous spaces

The Thoracic Limb: Manus > Carpus - 2 rows

Question Answer
Proximalradial (largest), intermeadiate & ulna (smallest)
accessory – insert. of extensor/flexor carpi ulnaris
Distal4 bones – 1, 2, 3 & 4

The Thoracic Limb: Manus - Carpus - species differences

SpeciesNo. of carpal bones
Dogradial & intermediate fused; intermedial radial
Ox1st distal absent
2nd & 3rd distal bones fused
Horse8 unless 1st distal is missing/rarely a 5th one is present

The Thoracic Limb: Manus - Carpal Joint/Compound Joint

3 joints; bet. the radius & ulna (antebrachiocarpal), proximal & distal carpal bones & metacarpal bones
I Radiocarpal - the first 2 are mainly ginglymus - main movement
II Intercarpal - hinge joint - main movement
III Carpometacarpal - gliding joint
* Joints between the individual carpal joints gliding
The fibrous layers of joint capsule cover the entire joint
Each joint has a separate synovial capsule also called joint sacs
The fibrous layer of joint capsule is modified dorsally to dorsal carpal ligament / extensor retinaculum with canals for the passage of the tendons of the extensor muscles
The palmar is also thickened to form the palmar carpal ligament / flexor retinaculum with canals for the passage of the tendons flexor muscles; it forms the accessory ligament or the deep head of the deep digital flexor muscle


3 synovial sacs
Radiocarpal sac is the most voluminous
Intercarpal joint communicates with the carpometacarpal joint between the 3rd & 4th carpal bones (important for treatment of arthritis)


2 collateral ligaments; medial & lateral
There are ligament between the small bones
Accessory carpal bone articulates with the other carpal bone by 3 ligaments; the main movement of this bone is for extension & flexion

The Thoracic Limb: Manus - Metacarpus > 5 bones; 1, 2, 3, 4, 5

Oxabsentabsentfused with 4fused with 4very small
--dorsal & palmar longitudinal groovedorsal & palmar longitudinal groove-
Horseabsentreducedlong cannon bonereducedabsent
-splintgroove for suspensory ligament on palmer surfacesplint bone-

The Thoracic Limb: Manus > Digits/Phalanges – 5; 1, 2, 3, 4, 5

Each Digit has 3 phalanx – proximal, middle & distal

Palmar Sessamoid Bones – 2 bet. at the metacarpophalangeal joint; 1 bet. middle & distal phalanx

Dogyes - no middle pyesyesyesyes
dewclaw; 1 sessa2222
0dewclaw; 0 sessa33dewclaw; 0
0dewclaw; 03 sessa3dewclaw; 0
003 sessa00

Horse - Digits

Question Answer
Proximal phalanxlong pastern
Middle phalanxshort pastern
Distal phalanxcoffin bone (embedded in the hoof); extensor process on the proximal dorsal surface for insert. of common digital extensor
Proximal sessamoid bonespart of the suspensory ligament
Distal sessamoid bonenavicular bone; bet. the middle&distal phalanx bones & the tendon of the deep digital flexor (outside the tendon; not within)