Quiz 2-Winter Flashcards
Main functions of forelimb
Posture & support (quadrupedals), locomotion, manipulation, somatosensory organs
Relative to pelvic limbs, the thoracic limb is…?
- Shorter and straighter
- Connected to the trunk by fibro-muscular attachments
Which way does the forelimb rotate during development?
Dorsally
What bones/muscles makes up the pectoral girdle?
Scapula, coracoid, clavicle & serratus ventralis, pectoralis profundus
What is special about the clavicle in quadrupedal mammals?
The clavicle is reduced or absent; no bony attachment of limb to axial skeletal
What is the gleno-humeral joint?
The “shoulder” joint; ball and socket
- The head of the humerus inserts into the glenoid of scapula
What movements are associated with the shoulder joint?
- Cranially/Caudally
- Dorsally/Ventrally
- Rotation: glenoid moves cranially, the whole limb advances
What limits movement of the GH joint?
The muscles surrounding the joint restricts movement to sagittal excursions
How is the body advance cranially?
Deep pectoral muscles pull the body cranially when the limb is advanced and fixed
What is the shoulder suspension mechanism?
A muscular sling suspends the thorax. Muscles of the shoulder girdle (serratus ventralis and pectoralis profundus) suspend the body between the forelimbs.
They transmit the weight of the head, neck, and cranial part of the trunk to the forelimbs and prevent the thorax from collapsing.
What is the brachial plexus?
Intersection of ventral rami from C6-T2 (variable between species). Named nerves carry axons originating from multiple spinal cord levels.
**Neck injuries can affect the whole limb
C6 contributes to which nerve(s)?
Suprascapular
C7 contributes to which nerve(s)?
Suprascapular, musculocutaneous, axillary, radial
C8 contributes to which nerve(s)?
Axillary, radial, median, ulnar
T1 contributes to which nerve(s)?
Radial, median, ulnar
What parent artery supplies the right thoracic limb?
Right subclavian; branching from the brachiocephalic trunk
What parent artery supplies the left thoracic limb?
Left subclavian; branching from aortic arch
What does the axillary artery supply?
Scapula, axilla, proximal humerus
Brachial artery supplies?
Arm (brachium) and proximal forearm (antebrachium)
Common interosseous artery
Last branch of brachial a. (around elbow)
Median artery
Continuation of brachial a. into the antebrachium
Radial artery
Branches from median artery
Ulnar artery
branches from common interosseous artery
Branches of axillary artery
Subscapular
Thoracodorsal
Lateral thoracic
Branch of brachial artery?
Deep brachial
What joints make up the elbow?
Radio-humeral
Ulno-humeral
Proximal radio-ulnar
*All one synovial joint
Movement of the elbow
Flexion and extension along sagittal plane
Pronation/supination of ulna around radius
What prevents ab/adduction of elbow?
Medial and lateral collateral ligaments
What prevents over-extension of elbow?
Oblique ligament located on cranial aspect of limb
True or False: the annular ligament of the radius attaches to the ulna and the radius?
False: it runs from ulna to ulna in a circular shape
What allow the distal radius to rotate around the distal ulna?
Annular ligament of radius
What’s the path of the radial nerve in brachium?
Runs caudal to the brachial artery, then dives between long and medial tricep heads
Path of the median nerve in brachium
Travels on medial aspect of arm caudal to axillary/brachial aa.
Enters antebrachium over medial collateral ligament at elbow
Path of ulnar nerve in brachium
Travels next to or united with median nerve;
splits off towards olecranon to cross caudal aspect of the elbow joint
What are the major veins near the elbow/brachium?
Cephalic vein - superficial cranial in brachium
Brachial vein - deep medial side of brachium
Median cubital vein - connects deep and superficial vv. (brachial & cephalic)
Major neurovasculature of cubital fossa
Brachial a/v
Cephalic v
Median cubital v
Median n
Ulnar n
True or False: the carpus is made up of 1 row of carpal bones
False: there are 2 rows; the proximal and distal bones
Proximal row of carpal bones by species
Carnivores: Radial + intermediate, ulnar, accessory
Equine/Bovine: radial, intermediate, ulnar, accessory
*Accessory projects behind the carpus, palpable
Distal row of carpal bones by species
Carnivores: 1, 2, 3, 4 (medial to lateral)
Equine: 1 (small), 2, 3, 4
Bovine: 2 + 3, 4
*5th is never separate, either fused or suppressed
Joints of the wrist
Distal radioulnar joint
Antebrachiocarpal* - very mobile
Midcarpal* - somewhat mobile
Carpometacarpal* - somewhat mobile; allows for some ab/adduction
*Ginglymus joints: hinge joint with some lateral movement
Wrist joints - ungulates
Antebrachiocarpal joint - very mobile (90o)
Midcarpal level - somewhat mobile (45o)
Carpometacarpal level - NO movement
Deep Palmar ligament
Covers entire palmar surface of skeleton; hides the unevenness of bones
Superficial, transverse ligament (aka flexor retinaculum)
Completes the enclosure of the carpal canal; passes obliquely accessory carpal bone to the medial aspect of carpal
Distal ligaments of accessory bone
Join bone to the adjacent carpal and metacarpal bones; assist in preventing overextension
What is the purpose of retinacula?
Functions like pulleys to distribute muscle forces; keeps tendon close
Radial nerve in antebrachium
Innervates carpal and digital extensors
- Muscular branches ramify in distal brachium
- Cutaneous branch reaches dorsal surface of digits
Horse: cutaneous branch fades at carpus
Median nerve in antebrachium
Innervates most of flexor carpus/digit mm
- Enters over medial collateral ligament
- Moves caudally to pass deep to flexor carpi radialis to carpus
Ulnar nerve in antebrachium
- Branches to carpal/digital flexor mm ramify in proximal antebrachium.
- Travels down caudal antebrachium.
- Main nerve of manus; splits proximal to accessory carpal bone.
What arteries “travel” with the median nerve?
- Brachial artery (in brachium)
- Common interosseous a. just distal to elbow
- Median artery (in antebrachium)
Where/what is the carpal tunnel?
It is deep to the flexor retinaculum (palmar surface) and constrained by carpal bones. It houses the tendons of digital flexors and the median nerve.
Plantigrade
“Flat-footed”
Walks on digits, metacarpals, carpals
Digitigrade
Walks on digits (phalanges)
Unguligrade
Walks on 1 or 2 digits
Metacarpals
I - V (I is the dewclaw)
- Base is proximal, head is distal
Phalanges
3 bones for each metacarpal
- Proximal, intermediate, distal
- 3 sesamoid bones between MC & P
- Dorsal (pea), proximal x2 (banana)
- Distal phalanx has an unguicular process instead of “head” which allows for claw
Foot pads Dog vs Cat
Dog: epidermis is heavily keratinized; dermal papillae project into epidermis; hypodermis is loose CT w/ sweat glands
Cat: epidermis is not nearly as thick; dermis = CT; hypodermis = loose CT; adipose tissue; sweat glands
Main role of the muscles in the manus
Help move the foot to adjust to different surfaces
Dorsal elastic ligaments (in dogs)
- Extend from proximal end of intermediate phalanges to unguicular crests of distal phalanges on medial and lateral sides
- Keeps the claws elevated
What causes the claws to protrude?
Contraction of the flexor digitorum profundus
Retraction of claws in cats via dorsal elastic ligaments
- Medial DE ligament is longer; extends from proximal intermediate phalanx to sides of distal
- Lateral DE; extends from distal end of intermediate phalanx to unguicular crest
*The distal phalanx is oriented obliquely to the intermediate; no muscular force is needed to keep claws retracted
Where do you cut to remove a dewclaw?
Detach at metacarpo-phalangeal joint of MC/P I
Onychectomy
Amputation of distal phalanx and claw (‘declawing’)
- Removes distal phalanx by disarticulating the distal interphalangeal joint
True or False: the superficial palmar arch is more distal than the deep palmar arch.
True
True or False: the superficial/deep palmar arches are the anastomoses of the radial, ulnar, and median aa.
True; they each have deep and superficial branches that give way to the metacarpal and phalangeal aa. at the arches
What is the name of the fibrous band in horses that joins the tendons of origin and insertion of the biceps brachii?
Internal tendon:
- Allows the muscle to store energy when stretched during support phase of stride
What is the lacertus fibrosus?
Tendon that splits from internal tendon to the surface in horses. Palpable as a firm structure. Taut in standing animal, but slackens as the joint is flexed
Horse/Cow knee
Carpus (wrist in humans)
Canon portion of forelimb (EQ)
Metacarpus II, III, IV
- II and IV are splint bones
- III is the canon bone
Fetlock portion of forelimb (EQ)
- Distal end of metacarpus III
- Phalanx I
- Proximal sesamoid bones (x2)
Pastern portion of forelimb (EQ)
- Phalanx I in the upper pastern
- Phalanx II in lower
Hoof portion of forelimb (EQ)
- P II, P III, and distal sesamoid
Canon portion of forelimb (BOV)
- Metacarpus III & IV
Fetlock portion of forelimb (BOV)
- PI
- Proximal sesamoid bones (x2 each digit)
Pastern portion of forelimb (BOV)
Phalanx II
Hoof portion of forelimb (BOV)
- Phalanx III
- Distal sesamoid bone (x1 each digit)
What is the great metacarpus in ungulates?
EQ: Metacarpus III
BOV: Metacarpus III/IV fused
True or false: Cows have small 1st and 2nd metacarpals.
False: They have no 1st/2nd. They do have a very small 5th on the caudal aspect
True or false: The 1st and 5th metacarpals in horses are called splint bones.
False: Horses do have splint bones but they’re made up of the 2nd and 4th metacarpals
Knee joints
Radiocarpal/ulnocarpal, intercarpal, carpometacarpal
Canon joints
NONE!!
Fetlock joints
Metacarpophalangeal
Pastern joints
Proximal interphalangeal (PI and PII)
Hoof joints
Distal interphalangeal (PII and PIII)
Dorsal intercarpal ligaments
Unite carpal bones within a row; allows for separation so the knee can flex
Palmar intercarpal ligaments
Unite carpal bones within a row as well as between rows to radius and metacarpals
Accessory ligaments
Fix the accessory bone
Ligaments of the fetlock, pastern, and hoof
Collateral articular ligaments
- Prevent the joint from bending side to side and keeps the bones together
Abaxial articular ligaments
Ligaments of the fetlock, pastern, and hoof in cattle. Lay on the most medial and lateral surfaces of leg
Axial articular ligaments
Fetlock, pastern, and hoof ligaments that lie between the digits
Insertion of common digital extensor
A. Extensor process of PIII
B. Proximal regions of PI & PII
C. External surface of the lateral cartilages
Insertion lateral digital extensor
Dorsal aspect of the proximal extremity of PI
Insertion superficial digital flexor
A. Lateral & medial surfaces of the proximal region of PII (Bov-each digit)
B. Lateral & medial aspects of PI (only EQ)
*At the proximal extremly of PI the tendon divides into 2 bands
*aka flexor perforatus (perforated)
Insertion of deep digital flexor
Semilunar line of the solar surface
*aka flexor perforans (perforating)
BOV-flexor process of PIII
Insertion of Check Ligament
Deep region of the proximal aspect of the deep digital flexor
*Reinforces the tendon of the DDF; originates on the palmar surface of the proximal extremity
*aka sub carpal ligament
Insertion of interosseous muscle/suspensory ligament
Proximal to the fetlock, divides in 2 branches that join the lateral and medial regions of the proximal sesamoid bones & PI
Insertion of distal sesamoid ligament
Palmar region of the proximal extremity of PIII
Palmar annular ligament
- Covers the palmar region of the fetlock
- Originates from the external surface of the proximal sesamoid bones
- Attaches on the superficial digital flexor
Proximal digital annular ligament
- Covers the palmar region of the proximal area of the pastern
- Originates with 2 proximal branches from the medial & lateral aspects of PI
- Attaches w/ 2 distal branches on the lateral and medial aspects of the distal end of PI & fuses w/ the superficial digital f.
Distal digital annular ligament
- Covers the deep digital flexor
- Originates at the palmar surface of PII
- Attaches proximally w/ 2 branches of PI with the distal ones of PDAL
Bovine common digital extensor
- Lateral tendon: splits at the fetlock into 2 branches between digits and inserts on extensor process of PIII in both digits
- Medial tendon: inserts dorsomedial surface of PII of 3rd digit (reinforced by axial/abaxial branches
Bovine Lateral digital extensor
- Dorsolateral surface of PII of the 4th digit (reinforced by branches of of interosseous m)
Proximal interdigital ligament
Small band located between the axial surfaces of PI (only see from palmar view)
Distal interdigital ligament
A cruciate ligament. Long proximal bands surround the joints of PI/PII. Short distal band insert on the joint of PII/PIII
Only seen from palmar view
What is the main tract of blood supply in horses in the antebrachium
Median artery to medial palmar which splits to medial digital and lateral digital aa.
Tendonititis
Bowed tendons (swelling of digital flexors)
Tendon rupture
Complete rupture of flexor tendons lead to permanent hyperextension of the fetlock
What is the purpose of the passive-stay apparatus?
Reduce muscular support while standing for long periods. Saves energy!
What things does the passive-stay apparatus combine?
The force of gravity with certain properties of the skeleton, tendons, and ligaments
What composes the suspensory apparatus?
Interosseous ligament and distal sesamoidean ligaments
Suspensory ligament/interosseous ligament origin & insertion
O: Palmar carpal ligament and MCIII and travels between splint bones
I: Inserts on the abaxial side of proximal sesamoid bones after splitting
*Proceeds along dorsal surface of the 1st phalanx to attach to the Extensor digitorum
Distal sesamoidean ligaments
Extends the suspensory apparatus to the pastern
The suspensory apparatus prevents…?
Hyperextension
What is the check apparatus composed of?
- Flexor digitorum profundus (connects via a check ligament tot he metapodial in both limbs)
- Flexor digitorum superficialis (connects via a check ligament to the radius in forelimb only)
Purpose of the accessory proximal check ligament
Forms connection from distal radius to the pastern joint. Prevents hyperextension of the carpal and fetlock joints without extra muscle tension
*Only in forelimb
Purpose of the accessory distal check ligament
Forms a connection all the way to the coffin joint from the joint capsule of the carpal/tarsal joint. Prevents hyperextension of the fetlock, pastern and coffin joints
The stay apparatus (thoracic limb) components
- Serratus ventralis
- Biceps brachi
- Lacertus fibrosus
- Extensor carpi radialis
The stay apparatus (pelvic limb) components
- Peronius tertius
- Flexor digitorum superficialis + fibrous band of gastrocnemius
*Reciprocal mechanism
Purpose of serratus ventralis in the stay apparatus
Supports the cranial part of the body and connects the costal side of the scapula to the caudal cervical vertebrae and cranial ribs
*Suspends the body once the muscles relax
How does the stay apparatus “correct” the scapula when the internal biceps brachi tendon is pulled cranially?
Via a connection to the lacertus fibrosus and the extensor carpi radialis tendon, the fixed leg causes the biceps tendon to pull distally and pulls the scapula back up in place
How are the carpals prevented from collapsing into flexion?
Force transmitted through the lacertus fibrosus and extensor carpi radialis prevents the carpal joints from collapsing
What is the reciprical mechanism?
Ensures that when the femur swings one way the, distal limb will swing the opposite way. Also ensure that when the patella and thus stifle is locked, the hock is also immobile
What’s the important muscle for the reciprocal mechanism?
Peroneous tertius: originates at the caudocranial femur and bifurcates to insert laterally on the calcaneus and 4th tarsal and dorally on the 3rd tarsal and MTIII
What happens if the peroneus tertius is ruptured?
Decoupling of the reciprical mechanism.
*Flexion of the stifle will not force subsequent flexion of the hock
What happens when the patella becomes locked?
The medial patellar ligament remains hooked over the medial trochlear ridge of the femur
Naturally occurring gaits
Walk, trot, canter, gallop
Specialized training and/or inherent
Pace - Standardbreds
Rack - Saddlebreds
Running Walk - Tennessee Walker
Tölt - Icelandic horse
Walk
4-beat gait; alternate between 2 or 3 feet on the ground; head and neck move in a slight up and down motion that helps maintain balance
Trot
2-beat gait; working gait for a horse
Canter/Tansverse gallop
controlled 3-beat gait (horse), 4-beat (dog)
Gallop/rotary gallop
A faster canter; 3-beat changes to a 4-beat in horses
What to look for with limping/lameness
- Head bobbing
- Front or back
- Right or left
- Bilateral vs unilateral
- Both rear vs. both front
- Multiple affected
Infraspinatus contracture
Degeneration of muscle fibers, replaced by fibrous tissue
Typical posture: lower limb externally rotated, elbow adducted, foot is abducted
Coxofemoral luxation
Extreme abduction of hip joint; most commonly craniodorally to acetabulum
Typical posture: thigh is adducted, stifle is rotated outward, tarsus rotated inward
Medial patellar luxation
External rotation of hip, bow-legged stance and gait
Calcanean tendon rupture
Stifle extends and tarso-crural joint hyper-flexes
Cranial cruciate ligament rupture
Usually non-weight bearing rear limb; may have some toe-touching
Gait disorder
Several disorders produce a characteristic stride pattern that is considered abnormal; usually evaluated at the walk
“Sweeny”/Suprascapular nerve injury
Nerve damaged as it curls around neck of scapula (kick injuries); muscle atrophy renders scapulohumeral joint unstable
Radial nerve injuries
Vulnerable to damage when horses are positioned in lateral recumbency
Femoral nerve paralysis
- Compression of nerve roots by calf/foal in birth or prolonged/rough pulling of hind limbs
- Prolonged stretch during general anesthesia
Stringhalt
Involuntary and exaggerated flexion of one or both hind limbs during cranial phase of the stride limb is jerked towards abdomen
-Coventianal (sporadic) vs Australian (outbreak)
Fibrotic myopathy
Semitendinosus injury leaving a dense scar restricting normal elastic property
Fixation of the Patella
Gait abnormality occurs during the initiation of the stride, leg locks in extension and is dragged behind the horse. Patella pops forward and leg jerks into flexion upon medial patellar ligament slips off medial trochlear ridge of femur
