Anatomy and Physiology of Cats and Dogs

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Anatomy and Physiology of Cats and Dogs

• Differences Between the Species
• Part 3

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Differences in Cats and Dogs

• Cats
• skeleton has 245 bones
• Skull has large eye sockets (why?)
• Jaw is short and strong (why?)
• 26 teeth as kittens and 30 as adults
• Limited ability to grind food

• Dogs
• skeleton has 319 bones
• 3 types of skulls dolichocephalic, mesocephalic,
  and brachycephalic
• 28 teeth teeth as puppies and 42 as adults
• More teeth allows for crushing and grinding of
  meat and plant material

3
Dog Skull Types
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Dog Skull Types

• Dolichocephalic
• Sight hounds
• Wolfs cranium elongated
• Narrow, long snout

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Dog Skull Types

• Mesocephalic
• Scent hounds and pointers
• Wolfs skull shortened with broader snouts to
  accommodate larger nasal chambers

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Dog Skull Types

• Brachycephalic
• Boxers, bully breeds, Cavalier, Pug
• Short, compact skulls that often lead to health
  problems

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Brachycephalic Skull Health Problems
The change in the skull shape of the British
Bulldog over the last fifty years. Notice
particularly the extreme for-shortening of the
nasal cavity. Image courtesy of Natural History
Museum, Bern
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Brachycephalic Skull Health Problems

• Skin with shorter skulls, the skin folds over
  itself around the eyes and nose which trap
  moisture and lead to bacteria growth

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Brachycephalic Skull Health Problems

• Eyes - a flat skull causes the eye sockets to
  become shallow, which leads to the eyes
  protruding. The cornea is more exposed, causing
  it to become dry and more likely to become
  damaged

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Brachycephalic Skull Health Problems

• Respiratory
• as the skull shortens over time due to poor
  breeding practices, the amount of soft tissue in
  the nose and throat remains the same.
• soft tissues are all crammed into a smaller space
  combined with the lack of underlying nasal bones,
  causes the nostrils to become very
• this crowding inside the nose and back of the
  throat obstructs airflow
• Brachycephalic Upper Airway Obstructive Syndrome
  (BUAOS)

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Brachycephalic Skull Health Problems

• Syringomyelia (SM) / "neck scratcher's disease"
• fluid-filled cavities develop within the spinal
  cord near the brain

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Brachycephalic Skull Health Problems

• the back half of the Cavalier King Charles
  Spaniels skull is too small to accommodate all
  of the brains cerebellum, which may also be too
  large, and so it squeezes through the foramen
  magnum (hole in back of skull) partially
  blocking the flow of CSF down the spinal cord

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Brachycephalic Skull Health Problems

• Syringomyelia (continued)
• the pressure created by the abnormal flow of CSF
  is believed to create the SM cavities (syrinx)
  in the spinal cord
• Incredibly painful disease
• Up to 95 of all Cavilier King Charles Spaniels
  affected by the mutation over 50 have SM
• https//www.youtube.com/watch?vfDjxvgfUVRU

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The Feline Spine

• The shoulder blade is attached to the rest of the
  body only by muscles, not by bone
• gives shoulder blade freedom to twist and move
• allows cats to open gait for full speed (30 mph)
• small collarbones allow cats to squeeze through
  tight openings and land on their feet from
  various heights

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Cat Righting Reflex

• A vestibular apparatus in their inner ear acts as
  a balance and orientation guide
• The flexible backbone and the absence of a true
  collarbone allows the cat to right itself in the
  air by twisting its head around

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Cat Righting Reflex

• Cats have a built-in parachute (low
  body-volume-to-weight ratio)
• When falling, this allows them to slow their
  velocity by spreading out and becoming their own
  parachute (What other animal can do this?)
• https//www.youtube.com/watch?vRtWbpyjJqrUlistU
  U6107grRI4m0o2-emgoDnAAindex0featureplcp

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Cat Righting Reflex

• Data of cats falling from windows in tall
  buildings was collected by veterinarians in New
  York City
• 90 survived, but with some injuries
• Of those, over a third needed life-saving
  treatment
• Cats that fell from 7-32 stories were less likely
  to die than those that fell from 2-6 stories
  (WHY?)

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Cat Righting Reflex

• One thought is that after a certain distance a
  cat reaches maximum speed and the vestibular
  mechanism in the ear shuts off, causing the cat
  to relax (Why is relaxing important?)
• Another thought is that the greater height gives
  the cat time to change to its parachute position