ANATOMY - Forelimb Flashcards
What are cursorial vertebrates?
Cursorial vertebrates are species which have evolved to run on the ground and are structurally modified to enhance speed and endurance
What are the three main anatomical adaptations of cursorial vertebrates?
Reduced pectoral skeleton
Elongation of the proximal limbs
Elongation of the distal limbs
What are the six regions of the forelimb?
Omo
Brachium
Antebrachium
Carpus
Manus
Digit
What are the seven bones of the forelimb?
Scapula
Humerus
Radius
Ulna
Carpal bones
Metacarpal bones
Phalanges
What are the six joints of the forelimb?
Shoulder
Elbow
Carpal joint
Metacarpophalangeal joint
Proximal interphalangeal joint
Distal interphalangeal joint
In which region of the forelimb is the scapula located?
Omo region
What type of bone is the scapula?
The scapula is a flat bone
Why does the scapula have a more ventral and lateral orientation in cursorial vertebrates?
The scapula has a more vertical orientation to accommodate a longer stride length
Identify these features of the scapula (including the fossa’s)
What are the four palpable surfaces of the scapula?
Dorsal border
Cranial border
Scapular spine
Acromion process
Why is the caudal border of the scapula not palpable?
The caudal border of the scapula is covered by muscle and thus cannot be easily palpated
What are the two fossa’s on the lateral surface of the scapula?
Supraspinous fossa
Infraspinous fossa
What is the palpable landmark for the shoulder present on the lateral surface of the scapula?
Acromion process
In which species is there no acromion process?
Horses have no acromion process
What is the name of the subchondral bone of the scapula?
Glenoid cavity
Which muscle tendon originates at the supraglenoid tubercle?
Biceps brachii tendon
What is the additional bony process present proximal to the acromion process of the feline scapula?
Suprahamate process
What are the two additional features of the large animal scapula?
Tuber on the scapular spine
Cartilage extension of the dorsal border of the scapula
Where are the two centres of ossification located in the scapula?
Body of the scapula
Supraglenoid tubercle
In which region of the forelimb is the humerus located?
Brachium region
What type of bone is the humerus?
The humerus is a long bone
What is the subchondral bone at the proximal end of the humerus?
Head of the humerus
What is the palpable landmark for the shoulder present at the proximal end of the humerus?
Greater tubercle
What is the name of the tubercle located on the medial side of the proximal humerus?
Lesser tubercle
What is the name of the groove between the greater and lesser tubercle?
Intertubercular groove
Which structure runs through the intertubercular groove?
Biceps brachii tendon runs through the intertubercular groove
What is the diaphysis of the humerus known as?
Body of the humerus
What is the distal epiphysis of the humerus known as?
Condyle
What are the two projections of the condyle?
Medial epicondyle
Lateral epicondyle
What is the subchondral bone at the distal end of the humerus?
Trochlea
What is the weakest point of the humerus that is very prone to fractures?
Supratrochlear foramen
Which two structures meet to make up the supratrochlear foramen?
Radial fossa (cranial)
Ulnar fossa (caudal)
(T/F) The supratrochlear foramen is present in all domestic species
FALSE. The supratrochlear foramen is absent in large animal and feline species
Which species have a supracondyloid foramen at the distal end of their humerus?
Feline species have a supracondyloid foramen
Which two structures pass through the supracondyloid foramen present in the feline humerus?
Brachial artery
Median nerve
What are the three palpable regions of the humerus?
Greater tubercle
Medial epicondyle
Lateral epicondyle
Where are the five centres of ossification located in the humerus?
Proximal epiphysis
Body of the humerus
Medial condyle
Lateral condyle
Medial epicondyle
Which type of joint is the shoulder?
The shoulder is a synovial joint
What are the articular surfaces which make up the shoulder joint?
Glenoid cavity
Head of the humerus
What are the two palpable landmarks for the shoulder joint?
Acromion process
Greater tubercle
What is the bicipital bursa?
The bicipital bursa is an out-pouching of the shoulder joint capsule into the intertubercular groove where it envelopes the the biceps brachii tendon
Which ligament hold the bicipital bursa in place?
Transverse ligament
(T/F) The shoulder joint has no collateral ligaments
TRUE.
Which muscles provide lateral support to the shoulder?
Supraspinatous muscle
Infraspinatous muscle
What is the point of origin for the supraspinatous muscle?
Supraspinous fossa
What is the point of origin for the infraspinatous muscle?
Infraspinous fossa
What is the point of insertion for the supraspinatous and infraspinatous muscles?
Proximal lateral humerus
Which nerve innervates the supraspinatous and infraspinatous muscles?
Suprascapular nerve
Which muscle provides medial support to the shoulder?
Subscapularis muscle
What is the point of origin for the subscapularis muscle?
Subscapular fossa
What is the point of insertion for the subscapularis muscle?
Proximal medial humerus
Which nerve innervates the subscapularis muscle?
Subscapular nerve
What are the five extrinsic muscles of the forelimb?
Brachiocephalic muscle
Latissimus dorsi muscle
Serratus ventralis muscle
Trapezius muscle
Pectoral muscles
What are the two points of origin for the brachiocephalic muscle?
Skull
Cervical vertebrae
What is the point of insertion for the brachiocephalic muscle?
Cranial humerus
What are the functions of the brachiocephalic muscle?
The brachiocephalic muscle is a forelimb protractor and a shoulder extensor
In which species is the vestigial clavicle embedded in the brachiocephalic muscle?
Feline
What is the point of origin for the latissimus dorsi muscle?
Thoracic vertebrae
What is the point of insertion for the latissimus dorsi muscle?
Caudal humerus
What are the functions of the latissimus dorsi muscle?
The latissimus dorsi muscle is a forelimb retractor and a shoulder flexor
Which nerve innervates the latissimus dorsi muscle?
Brachial plexus
What are the two points of origin for the serratus ventralis muscle?
Cervical vertebrae
Thoracic wall
What is the point of insertion for the serratus ventralis muscle?
Cranial and caudal borders of the scapula
What are the functions of the serratus ventralis muscle?
The serratus ventralis muscle is both a forelimb retractor and protractor
Which nerve innervates the serratus ventralis muscle?
Brachial plexus
What are the two points of origin for the trapezius muscle?
Cervical vertebrae
Thoracic vertebrae
What is the point of insertion for the trapezius muscle?
Scapular spine
What is the function of the trapezius muscle?
The trapezius muscle is a forelimb abductor
What is the point of origin for the pectoral muscles?
Sternum
What is the point of insertion for the pectoral muscles?
Medial humerus
What is the function of the pectoral muscles?
The pectoral muscles are forelimb adductors
Which nerve innervates the pectoral muscles?
Brachial plexus
What are the two antagonistic pairs of the extrinsic muscles of the forelimb?
Brachiocephalic and Latissimus Dorsi muscles
Trapezius and Pectoral muscles
In which region of the forelimb are the radius and ulna located?
Antebrachium region
What type of bone are the radius and ulna?
The radius and ulna are long bones
Why is it more important to stabilise a diaphysial fracture of the radius than a diaphysial fracture to the ulna?
The radius has weight bearing function making it more important to stabilise a diaphysial fracture of the radius compared to the ulna
What is the proximal subchondral bone of the radius?
Head of the radius
What is the distal subchondral bone of the radius?
Distal radius
What is the purpose of the medial styloid process located at the distal end of the radius?
The medial styloid process is the point of attachment for the medial collateral ligament of the carpal joint
Where are the three centres of ossification located in the radius?
Proximal epiphysis
Body of the radius
Distal epiphysis
Identify these features of the ulna
What is the proximal subchondral bone of the ulna?
Trochlear notch
What is the palpable landmark for the elbow present at the proximal end of the ulna?
Olecranon process
Which species have a square shaped olecranon process?
Feline
What is the function of the anconeal process at the proximal end of the ulna?
The anconeal process is involved in stabilising the elbow joint through interdigitating with the ulnar fossa of the humerus
Where does the radius sit within the ulna?
The radius sits in the radial notch located between the medial and lateral coronoid processes
Which ligament hold the radius within the radial notch?
Annular ligament
What is the purpose of the lateral styloid process located at the distal end of the ulna?
The lateral styloid process is the point of attachment for the lateral collateral ligament of the carpal joint
Where are the four centres of ossification located in the ulna?
Olecranon process
Anconeal process
Body of ulna
Distal epiphysis
(T/F) The growth plate for the anconeal process should be closed in neonates
TRUE.
How can blunt force trauma to the distal epiphyseal growth plates of the radius or ulna cause angular limb deformities in young animals?
Blunt force trauma to the distal epiphyseal growth plates of the radius or ulna can cause premature closure of the growth plates which causes the distal end of the bone to stop growing. This causes the radius and ulna to grow at different rates leading to angular limb deformities
What anatomical feature allows canine and feline species to have a degree of rotation in their radius and ulna in comparison to larger species which do not?
Canine and feline species have a separate radius and ulna which allows for rotation, whereas larger domestic species have a fused radius and ulna (horses fuse proximally)
What type of joint is the elbow?
Synovial joint
What are the articular surfaces that make up the elbow joint?
Trochlea
Head of the radius
Trochlear notch
What are the three palpable landmarks of the elbow joint?
Medial humoral epicondyle
Lateral humoral epicondyle
Olecranon process
Why is lateral blunt force trauma when the elbow is in hyperflexion most likely to cause dislocation?
When the elbow is in hyperflexion, the anconeal process no longer interdigitates with the ulnar fossa of the humerus so the elbow is less stable and thus prone to dislocation
What are the five intrinsic muscles of the proximal forelimb?
Deltoideus muscle
Teres major muscle
Triceps brachii muscle
Biceps brachii muscle
Brachialis muscle
What is the point of origin for the deltoideus muscle?
Caudal scapular spine
What is the point of insertion for the deltoideus muscle?
Lateral humerus
What is the function of the deltoideus muscle?
The deltoideus muscle is a shoulder flexor
Which nerve innervates the deltoideus muscle?
Axillary nerve
What is the point of origin for the teres major muscle?
Caudal border of the scapula
What is the point of insertion for the teres major muscle?
Medial humerus
What is the function of the teres major muscle?
The teres major muscle is a shoulder flexor
Which nerve innervates the teres major muscle?
Axillary nerve
What are the four heads of the triceps brachii muscle?
Long head
Medial head
Accessory head
Lateral head
What is the point of origin for the long head of the triceps brachii muscle?
Caudal border of the scapula
What is the point of insertion for the long head of the triceps brachii muscle?
Olecranon process
What are the functions of the long head of the triceps brachii muscle?
The long head of the triceps brachii muscle is a shoulder flexor and an elbow extensor
What is the point of origin for the medial, accessory and lateral heads of the triceps brachii muscle?
Body of the humerus
What is the point of insertion for the medial, accessory and lateral heads of the triceps brachii muscle?
Olecranon process
What is the function of the medial, accessory and lateral heads of the triceps brachii muscle?
The medial, accessory and lateral heads of the triceps brachii muscle are elbow extensors
Which nerve innervates the triceps brachii muscle?
Radial nerve
What is the point of origin for the biceps brachii muscle?
Supraglenoid tubercle
What is the point of insertion for the biceps brachii muscle?
Radius
What are the functions of the biceps brachii muscle?
The biceps brachii muscle is shoulder extensor and an elbow flexor
Which nerve innervates the biceps brachii muscle?
Musculocutaneous nerve
Which anatomical structure allows the biceps brachii muscle to also be a carpal extensor in the horse?
The lacertus fibrosis is a fibrous extension from the distal biceps brachii muscle to the third metacarpal which allows the biceps brachii muscle to be a carpal extensor in the horse
What is the point of origin for the brachialis muscle?
Humerus
What is the point of insertion for the brachialis muscle?
Cranial radius
What is the function of the brachialis muscle?
The brachialis muscle is an elbow flexor
Which nerve innervates the brachialis muscle?
Musculocutaneous nerve
In which region of the forelimb are the carpal bones located?
Carpus region
Which type of bone are the carpal bones?
Carpal bones are short bones
What are the two rows of the carpal bones?
Proximal layer
Distal layer
List the proximal row of carpal bones from medial to lateral
Radial carpal bone
Intermediate carpal bone
Ulnar carpal bone
Accessory carpal bone
List the distal row of carpal bones from medial to lateral
1st carpal bone
2nd carpal bone
3rd carpal bone
4th carpal bone
Which carpal bone is palpable?
Accessory carpal bone is palpable
Which ligament originates at the accessory carpal joint?
Palmer ligament
What is the function of the palmer ligament?
The palmer ligament counteracts the forces applied to the accessory carpal bone to prevent carpal joint collapse and hyperextension
Which carpal bones are fused in carnivores?
Radial carpal bone and intermediate carpal bone are fused to form the radial intermediate carpal bone
Which carpal bone is absent in equids?
The 1st carpal bone is absent in equids
Which carpal bones are fused in equids?
2nd and 3rd carpal bones are fused in equids
Which carpal bone has more than one centre of ossification?
Accessory carpal bone
What type of joint is the carpal joint?
Synovial joint
List the three inter-carpal joints
Antebrachio-carpal joint
Middle carpal joint
Carpo-metacarpal joint
How should you position the carpal joint to collect synovial fluid?
Position the carpal joint in hyperflexion to collect a synovial fluid sample
What are the three stance classifications?
Plantigrade
Digitigrade
Unguligrade
What are plantigrade species?
Plantigrade species weight bare on the entire length of the distal limb
What are digitigrade species?
Digitigrade species weight bare on their phalanges and have protective footpads
What are unguligrade species?
Unguligrade species weight bare on their distal phalanges and have a protective hooves
What are the two divisions of unguligrade species?
Artyodactyla
Perissodactyla
What is the difference between artyodactyla and perissodactyla unguligrade species?
Artyodactyla species weight bare on an even number of distal phalanges whereas perissodactyla species weight bare on an uneven number of phalanges
In which region of the forelimb are the metacarpal bones located?
Manus region
Which type of bone are the metacarpal bones?
Metacarpal bones are long bones
Which metacarpal bones are found in carnivore species?
2nd, 3rd, 4th and 5th metacarpal bones are found in carnivore species
Which metacarpal bones are found in ruminants?
3rd and 4th metacarpal bones are found in ruminants
Which metacarpal bone is found in equids?
3rd metacarpal bone is found in equids
What is the name used to describe the 3rd metacarpal bone found in equids?
Cannon bone
What is the name used to describe the vestigial 2nd and 4th metacarpal bones found in equids?
Splint bones
Where are the two centres of ossification located in the metacarpal bones?
Body of the metacarpal
Distal epiphysis
In which region of the forelimb are the phalanges located?
Digit region
Which type of bone are the phalanges?
The phalanges are long bones
What are the three phalanx bones?
Proximal phalanx
Middle phalanx
Distal phalanx
What is the name used to describe the proximal phalanx in horses?
Pastern bone
What is the name used to describe the distal phalanx in horses?
Pedal bone
Which tendon inserts onto the extensor process present on the distal phalanx?
The common digital extensor tendon inserts onto the extensor process of the pedal bone
Which tendon inserts onto the palmer process of the distal phalanx?
The deep digital flexor tendon inserts onto the palmer process of the distal phalanx
Where are the two centres of ossification located in the phalanges?
Proximal epiphysis
Body of the phalanx
Which phalanx has only one centre of ossification?
The distal phalanx has only one centre of ossification
Which sesamoid bones are found in all species?
Proximal sesamoid bones
Where are the proximal sesamoid bones located?
The proximal sesamoid bones are located on the distal palmer/plantar surfaces of all metacarpal and metatarsal bones
Which ligament embeds the proximal sesamoid bones?
Suspensary ligament
Which two tendons are protected by the proximal sesamoid bones?
Superficial digital flexor tendon
Deep digital flexor tendon
Which sesamoid bones are only found in carnivores?
Dorsal sesamoid bones
Where are dorsal sesamoid bones located?
Dorsal sesamoid bones are located on the dorsal surface of the metacarpo-phalangeal/metatarso-phalangeal joints
Which tendon is protected by as well as embeds the dorsal sesamoid bones?
Common digital extensor tendon
Which sesamoid bone is only found in ruminants and equids?
Distal sesamoid
What is the other name for the distal sesamoid bone?
Navicular bone
Where is the distal sesamoid located?
The distal sesamoid is located on the palmer/plantar surface of the distal phalanx
What kind of joint is the metacarpo-phalangeal joint?
Synovial joint
What are the two pouches formed by the extensive joint capsule of the metacarpo-phalangeal joint?
Large palmer pouch
Dorsal palmer pouch
What is the function of the large palmer pouch of the metacarpo-pharyngeal joint?
The large palmer pouch incorporates the proximal sesamoids
What is the function of the dorsal palmer pouch of the metacarpo-pharyngeal joint?
The dorsal palmer pouch cushions the common digital extensor tendon
What type of joint is the proximal interphalangeal joint?
Synovial joint
What is the function of the dorsal bursa formed by the extensive joint capsule of the proximal interphalangeal joint?
The dorsal bursa cushions the common digital extensor tendon
What type of joint is the distal interphalangeal joint?
Synovial joint
What is the function of the dorsal bursa formed by the extensive joint capsule of the distal interphalangeal joint?
The dorsal bursa cushions the common digital extensor tendon
What are the functions of the impar ligament?
The impar ligament attaches the navicular bursa to the pedal bone (distal phalanx) and separates the navicular bursa from the joint capsule of the distal interphalangeal joint
What is the function of the suspensory apparatus of the distal limb?
The suspensory apparatus of the distal limb supports and prevents overextension of the metacarpophalangeal joint
What are the four components of the equine suspensory apparatus?
The suspensory apparatus is part of the equine stay apparatus
Suspensory ligament
Proximal sesamoids
Sesamoidean ligaments
Common digital extensor tendon
The suspensory apparatus is in both the forelimbs and hindlimbs
What are the functions of suspensory ligament?
The suspensory ligament stabilises the proximal sesamoid bones and prevents hyperextension of the metacarpo/tarso-phalangeal joint through acting as a sling to return the joint to its resting position
What is the point of origin for the suspensory ligament?
Proximal, palmer surface of the third metacarpal bone
Which tendon does the suspensory ligament fuse with?
Common digital extensor tendon
What is the function of the sesamoidean ligaments?
The sesamoidean ligaments stabilise the proximal sesamoid bones
What are the three main classifications of sesamoidean ligaments?
Inter-sesamoidean ligament
Collateral sesamoidean ligaments
Distal sesamoidean ligaments
Identify this sesamoidean ligament
Inter-sesamoidean ligament
What is the main function of the inter-sesamoidean ligament?
The inter-sesamoidean ligament allows for smooth passage of the superficial digital flexor tendon (SDFT) and deep digital flexor tendon (DDFT)
What are the four distal sesamoidean ligaments
Cruciate distal sesamoidean ligaments
Short distal sesamoidean ligaments
Oblique distal sesamoidean ligaments
Straight distal sesamoidean ligament
Identify the following distal sesamoidean ligaments
Which tendon does the straight sesamoidean ligament insert with?
Superficial digital flexor tendon (SDFT)
What are ‘chestnuts’ found on the equine distal limb?
‘Chesnuts’ on the equine distal limb are vestigial horn pads
What is an ‘ergot’ found on the equine distal limb?
An ‘ergot’ found on the equine distal limb is a dense fibrous cushion on the palmar aspect of the metacarpo-phalangeal joint
What are the six intrinsic muscles of the distal forelimb?
Extensor carpi radialis muscle
Common digital extensor muscle
Extensor carpi ulnaris muscle
Flexor carpi ulnaris muscle
Superficial digital extensor muscle
Deep digital extensor muscle
(T/F) All of the intrinsic muscles of the distal forelimb insert as tendons
TRUE.
What is the point of origin for the extensor carpi radialis muscle?
Lateral humoral epicondyle
What is the point of insertion for the extensor carpi radialis tendon?
Metacarpal bones
What is the function of the extensor carpi radialis muscle?
The extensor carpi radialis muscle is a carpal extensor
Which nerve innervates the extensor carpi radialis muscle?
Radial nerve
What is the point of origin for the common digital extensor muscle?
Lateral humoral epicondyle
What is the point of insertion for the common digital extensor tendon?
Extensor process of the distal phalanges
What are the functions of the common digital extensor muscle?
The common digital extensor muscle is a carpal extensor and a digital extensor
Which nerve innervates the common digital extensor muscle?
Radial nerve
What is the point of origin for the extensor carpi ulnaris muscle?
Lateral humoral epicondyle
What are the two points of insertion for the extensor carpi ulnaris tendon?
Accessory carpal bone
Metacarpal bones
What are the functions of the extensor carpi ulnaris muscle?
The extensor capri ulnaris muscle is both a carpal extensor and flexor
Which nerve innervates the extensor carpi ulnaris muscle?
Radial nerve
What are the two points of origin for the flexor carpi ulnaris muscle?
Medial humoral epicondyle
Olecranon process
What is the point of insertion for the flexor carpi ulnaris tendon?
Accessory carpal bone
What is the function of the flexor carpi ulnaris muscle?
The flexor capri ulnaris muscle is a carpal flexor
Which two nerves innervate the flexor carpi ulnaris muscle?
Median nerve
Ulnar nerve
What is the point of origin for the superficial digital flexor muscle?
Medial humoral epicondyle
What is the point of insertion for the superficial digital flexor tendon?
Palmer surface of the middle phalanx
What are the functions of the superficial digital flexor muscle?
The superficial digital flexor muscle is a carpal flexor and digital flexor
Which two nerves innervate the superficial digital flexor tendon?
Median nerve
Ulnar nerve
Why does the superficial digital flexor tendon branch at the distal end?
The superficial digital flexor tendon branches distally to allow the passage of the deep digital flexor tendon
What are the three points of origin for the deep digital flexor muscle?
Medial humoral epicondyle
Radius
Ulna
What is the point of insertion of the deep digital flexor tendon?
Palmer process of the distal phalanx
What are the functions of the deep digital flexor muscle?
The deep digital flexor muscle is a carpal flexor and digital flexor
Which two nerves innervate the deep digital flexor muscle?
Median nerve
Ulnar nerve
Which four structures run through the carpal canal?
Superficial digital flexor tendon
Deep digital flexor tendon
Blood vessels
Nerves
What are the dorsal, lateral and palmer boundaries of the carpal canal?
Dorsal: Carpal joint capsule
Lateral: Accessory carpal bone
Palmer: Retinaculum
Which structure protects the superficial and deep digital flexor tendons as they pass through the carpal canal?
Tendon sheaths
What is the function of the accessory check ligaments in equids?
The accessory check ligaments prevent excessive lengthening of the superficial and deep digital flexor tendons
What is the equine stay apparatus?
The equine stay apparatus is an arrangement of muscles, tendons and ligaments that work together to allow an animal to stand with limited muscular effort through maintaining the joints in extension whilst preventing hyperextension
Which muscle within the equine stay apparatus suspends the weight of the trunk between the forelimbs?
Serratus ventralis muscle suspends the weight of the trunk between the forelimbs
Which muscle within the equine stay apparatus prevents the shoulder from collapsing into flexion?
Biceps brachii muscle prevents the shoulder from collapsing into flexion
Which ligaments within the equine stay apparatus prevent the elbow from collapsing into flexion?
Collateral ligaments of the elbow provide passive support to prevent the elbow from collapsing into flexion
Which structure within the equine stay apparatus prevents the carpal joint from collasping into flexion?
Lacertus fibrosis
Which structures within the equine stay apparatus prevent the hyperextension of the carpal joint?
Superficial digital flexor tendon
SDFT Accessory check ligament
Retinaculum
Which structures within the equine stay apparatus prevent the hyperextension of the metacarpophalangeal joint, proximal interphalangeal joint and distal interphalangeal joint?
Superficial digital flexor tendon
SDFT Accessory check ligament
Deep digital flexor tendon
DDFT Accesory check ligament
Annular ligaments
Which additional apparatus prevents hyperextension of the metacarpophalangeal joint?
Suspensory apparatus
Identify the structures on this long axis ultrasound of the equine distal limb
Identify the structures on this short axis ultrasound of the equine distal limb
