Unit 2: Comparative Anatomy Flashcards
Skull - Mandible
2 sides of mandible united by fibrocartilage…
Fused in horse
Thoracic/Pectoral: Scapula
Define in cat and dog
Shortened in cow/horse (because they have cartilage at the top that carnivores don’t)
Thoracic/Pectoral: Radius/ulna
Separate bones in cat/dog (can supinate - rotate wrist)
Fused in horses (can’t supinate)
Thoracic/Pectoral: Carpus
Generally made of 8 bones
In dog/cat located where foot flexes
- Radial and intermediate fused
In horse/cow located up high (you may think it is knee)
- Cows have no 1st, 2nd and 3rd fused
- Horse have just 3rd (remember ‘horse is giving you the finger’)
*only specific bone needed to memorize is accessory
Thoracic/Pectoral: Metacarpal
Carnivores: MC1 reduced (declaw), non-weight bearing
Cows: MC1 + 2 missing, 3 + 4 fused = ‘cannon bone’, 5 vestigial (no digit)
Horse: MC 1 + 5 missing, 2 + 4 greatly reduced - splint bone, 3 is weight bearing ‘cannon bone’
Thoracic: Digits
Carnivores: 4 bear weight (2, 3, 4, 5)
Cow: 2 bear weight (3 4), 2 dewclaws that are vestigial remnants of 2 5
Horse: only 3 bears weight (phalanges can be called long pastern, short pastern, and coffin bone)
Cow vs horse sesamoids
Irregular small bones located in a tendon, help joint have smooth motion
Cow: 2 proximal sesamoids per digit, distal 1 per digit
Horse: 2 proximal sesamoids on each limb, distal = ‘navicular’
- Located in fetlock
Pelvic Limb: Femur
Acetabulum = socket
Trochlear tubercule = very prominent in horse, part of ‘stay apparatus’ AKA patellar lock mechanism
- An arrangement of patella ligaments and lower distal limb ligaments that lock it from collapsing when there is more weight on it (they are bearing all their weight on 4 toes). They rotate their patella medially so they walk on trochlear ridge, specialized tendons support that limb so stifle and hock move as one movement (can’t independently flex knee). Shift their weight between limbs when standing to allow for rest. Limit energy needed to stand when standing still.
Greater trochanter in horse divided into cranial and caudal
Pelvic Limb: Tibia/Fibula
Carnivores: 2 separate bones
Cows: fibula poorly developed, head fused to tibia but separate at distal end
Horse: fibula poorly developed, head separate but distal end fused
Pelvic Limb: Tarsus
Hock AKA ankle
- Tarsus = joint & group, tarsal = individual
2 rows of bones, some fused some separate, won’t need to name all
* only need to know calcaneus (attachment site for calf muscles, allows hock to flex)
Pelvic Limb: Metatarsal
Similar to metacarpals
Carnivores: MT 1 is even smaller, most dogs don’t have hind dew claw
Cows: 5 absent, 3 4 fused
Cat: much longer than metacarpals
Pelvic Limb: Digits
Same as thoracic, except
Horse: coffin bone longer and less rounded
What goes wrong: Skull
Dolicocephalic: long (collie)
Mesocephalic: moderate (lab)
Brachycephalic: short (pug)
- Overcrowded teeth, hard time breathing, shallow eye sockets (bulging eyes), dystocia (difficult birth)
- Also in persian cats, same problems
Cows: frontal sinus extends into the horn (cornual process) when mature, if dehorned the sinus is exposed to external environment -> infection (must be done young)
What goes wrong: spine
DEVELOPMENTAL LESIONS (born w/it)
1. Spina bifida: rare, cleft/space in the dorsal part of vertebrae column
- Hemi vertebrae: failure of vertebral body to ossify resulting in improperly formed vertebrae
- 3 kinds of…. ?
Kypohosis: dorsal curvature of vertebral column
Lordosis: ventral curvature
Scoliosis: lateral curvature. - Wobblers (Cervical Vertebral Instability) common in great danes and horses. Narrowing of spinal cord, compresses. Important for these dogs to grow slow. Sign of onset = ataxia (uncoordination, drunken gait), can progress to paralysis.
What goes wrong: Thoracic limb
Angular Limb Deformities of Foals
- Congenital or acquired in early neonatal life
- Frequently carpus affected (angled out, think ‘knock-kneed’)
……
Premature Closure of the Physis
- Most common in radius and ulna, bowing of limb which then causes changes in joints
- Often happens when young growing dogs jump out of cars and cause trauma to the cartilage
