Module 4: Basic Anatomy Of The Forelimb

Question 1

Regions of the forelimb (thoracic limb) and the bones of each region

Answer 1

Shoulder → scapula, clavicle
Brachium ( arm, upper arm) → humerus
Antebrachium (forearm) → radius and ulna
Carpus (wrist) → carpal bones
Metacarpus → metacarpal bones
Digit (finger) → proximal, middle and distal phalanges

Question 2

Scapula aka the shoulder blade

Answer 2

Flat bone → compressed laterally, triangular in shape
Attached to the body w/ help of muscles → synsarcosis= “joint” formed between a bone and the body via muscles
Medial = rough area for attachment of muscles that connect the bone to the body
Lateral aspect = spine of the scapula → divides the lateral into 2 fossae (depressions) → Supraspinous fossa (above the spine) and infraspinous fossa (below the spine)
Ventral aspect = has a shallow glenoid cavity → articulates with head of the humerus

Question 3

Scapula: species differences

Answer 3

Unguates (hoofed animals) → dorsal aspect of scapula = the scapular cartilage → increases the surface area of the shoulder for muscle attachment
All domestic species EXCEPT the horse and the pig → spine of the scapula ends in the acromion process, a prominent spinous process

Question 4

Clavicle

Answer 4

Virtually absent in domestic species
Reduced to a fibrous intersection in the brachiocephalicus muscle
Dog = a very small bone in the intersection
Cat = a small crescent-shaped clavicle in the intersection

Question 5

Brachium aka humerus

Answer 5

Long bone
Proximal end = a head → articulates with the scapula’s glenoid cavity = forms the shoulder joint
2 processes closely associated with the head: the greater tubercle (laterally) and the lesser tubercle (medially) → separated by the intertubercular groove
Shaft = twisted appearance due to presence of a groove on its surface
Distal end= articular condyle

Question 6

Humerus: species difference

Answer 6

Smaller domestic species, like the cat and the dog = articular condyle divided into a medial trochlea (articulates w/ the ulna) and the lateral capitulum (articulates w/ the radius)
All domestic species = the groove formed by the trochlea continues in caudal aspect to form the olecranon fossa → a deep fossa that accommodates the anconeal process of the ulna

Question 7

Antebrachium (radius and ulna)

Answer 7

Radius= long bone; typically stronger than the ulna in domestic spaces (some species differences
Proximal aspect (radius) = wide along transverse plane → articulates with the humerus’s distal end
Distal end (radius) = wide and presents the medial styloid process(on the medial aspect)
Ulna = much reduced in comparison to radius → in larger domestic species it is fused with the radius