ANS 42 Lecture Notes - Lecture 4: Plantigrade, Digitigrade, Clavicle
13 Jan 2017
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Form and Function
1. Bone: skeletal strength for locomotion
a. a little bit of genetic and little bit of environment
b. your bones are strong if you use it
c. regardless of the species, one of its purposes is to withstand mechanical forces of
locomotion
d. 5-7 times stronger than force associated with normal function
2. Cats
a. Have little lateral mobility in their bones
b. Have 42 more bones than a human (in the tail)
c. Vertebrae in the back are primarily connected by muscle
i. Unlike the ligaments in a human back
d. Have a vestigial clavicle (collarbone)
i. Vestigial: greatly reduced
ii. Reduces the size of the shoulders
iii. Allows a narrower shoulder so that they can get into smaller spaces
iv. Gives it greater stride length
e. Stride length: the distance covered between footfalls
i. The greater the stride length, the more ground coverage
ii. Can reach forward, farther
iii. However, the cat cannot lie flat on its back with its legs flat out
iv. Also assists in a flexible spine
1. Enables the cat to completely extend itself
2. When the cat runs, the back legs can come in front of the front legs
3. The cat can push off with its front legs and have the back legs extend to
the front and push off and repeat
4. Spring-like motion
5. Can extend 3x of its body length
6. However, it takes a lot of energy
7. Cheetah can run up to 70 mph
a. However can only stay at that speed for 3/10 of a mile
3. Three different types of foot forms
a. Plantigrade: flat footed (squirrels, people, bears)
i. The most ground contact
ii. Extremely stable
b. Digitigrade: walking on digits (cats, dogs, birds – predator items)
i. less ground contact
ii. less stability compared to the plantigrade
iii. increases leg length
1. longer stride length
2. cover more ground
c. Unguligrade: tips of toes (dear, cows, sheep – prey items)
i. Decreased ground contact
ii. Really increased leg length
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