Forelimb Anatomy: Bones Flashcards
How is the forelimb attached?
no body attachment of forelimb to axial skeleton
attachment completed with muscles and ligaments
What kind of weight does the forelimb support?
60% of weight support by forelimbs
can reach 3,000 pounds of force in jumping horse
What are the bones of the forelimb
scapula
humerus
radius
ulna
carpal bones
metacarpal bones
phalanges
sesamoids
Describe the scapula
flat bone
cartilaginous dorsal border: incorporated into withers, increasingly calcified with age
lateral palpable spine: orientation affects conformation
scapulohumeral articulation: shoulder joint
Describe the humerus
long bone
covered by muscle
scapulohumeral articulation: shoulder joint
humeroradial and humeroulnar: elbow joint
Describe the radius and ulna
solidly attached (syndesmosis): fused in adult
radius: larger, slight dorsal convex curve
ulna: lies caudal to radius, ends half-way down radius, olecranon - point of elbow
articulations: humeroradial and humeroulnar: elbow joint
radiocarpal joint
Describe the carpus
AKA knee
7-9 bones
2 rows
3 joints
Describe the carpal bones
proximal row, medial to lateral:
radial, intermediate, ulnar, and accessory
diatal row, medial to lateral: (1st), 2nd, 3rd, 4th, (and 5th)
articulations: radiocarpal, midcarpal, carpometacarpal
Describe the accessory carpal bone
does not withstand any weight bearing forces
located caudal/palmar to ulnar carpal bone
articulated with distal radius and ulnar carpal bone
helps orient radiograph, it’s on the lateral side
Describe the 1st and 5th carpa bones
1st carpal bone (less than 50%)
5th carpal bone: rarely
can be mistaken for fracture on radiograph
Describe the metacarpal bones
Metacarpal 3 = cannon bone = MCIII
Metacarpal 2 = medial splint bone = MCII
Metacarpal 4 = lateral splint bone = MCIV
MCII and MCIV: end distally in buttons (palmar metacarpal nerves)
- carpometacarpal articulations
MCIII: oval in cross section: hind are round in cross-section
continues as digit
articulation: carpometacarpal, metacarpophalangeal (fetlock joint)
describe the phalanges
proximal phalanx = PI = long pastern
middle phalanx = PII = Short pastern
distal phalanx = PIII = coffin bone
What are the articulations of the phalanges?
metacarpophalangeal = fetlock joint
proximal interphalangeal = pastern joint
distal interphalangeal = coffin joint
Describe the sesamoids
proximal sesamoids: medial and lateral (articulated with MCII)
distal sesamoid: AKA navicular bone, articulates with PII and PIII
Describe the proximal sesamoids
anchor suspensory apparatus
reduce friction between fetlock joint, suspensory ligament, and flexor tendons
most frequently fractured forelimb bones
look like 3 - sided triangle
describe the distal sesamoids
boat-shaped, proximal to mid frog
provides greater bearing surface for DDFT
navicular bursa - between bone and DDFT
make sure to study this on paper!
