ZOO 4910 Lecture Notes - Lecture 13: Shoulder Joint, Human Musculoskeletal System, Metacarpal Bones
2 May 2018
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Department
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Professor
Barrel-shaped trunk -supports fermentation chamber
!
Speed -long and rapid strides
!
Stamina -energy efficient motion
!
Standing -fatigue resistance at rest
!
Built for…
○
Losing the collar bone adds length
to the leg: rotation is not at shoulder
joint but half way up the shoulder
blade
"
Modified nail co-opted as a
weight-bearing component of
the musculoskeletal system
!
Changing foot posture --> the
equine hoof
"
Humerus
!
Femur
!
Fore and hind feet
!
Lengthening the bones themselves
"
*major problem with long bones is
an increased risk of fracture
"
To maximize stride length, lengthen the
legs (cover more ground in air)
!
Big heavy muscles that
power the legs are close to
the trunk
!
Hammer head is at the top
!
Disproportionate bone length saves
energy
"
Splint bone = reduced
metacarpal
!
*makes the shaft of the
hammer easier to swing
!
Losing toes saves energy
"
To maintain stride frequency, increase
moment of inertia
!
Speed = stride length*frequency
○
Long skinny legs -move animal swiftly, with stamina
and energy efficiency
!
The fermentation vat: use cellulase-producing
microbes to ferment cellulose
○
Very large gut --> fermentation of cellulose
!
Shape of Horses: *functionally integrated or correlated parts
Have enlarged stomach as the fermentation Vat
!
Ex. Cow
!
Foregut Fermenters:
Extensive modification of the dentition, caecum and
ascending colon
!
Ex. Horse
!
Hindgut Fermenters:
Back as a locomotory organ
○
Extension and flexion
○
Epaxial and hypaxial lumbar muscles, and
thoracolumbar fascia
○
Ex. Cheetah
!
See slide
○
Trunk as a truss
!
Tendons provide support from the abdomen wall
!
Rigidity & Flexibility of the Vertebral Column:
Metabolic costs differ and same speeds
○
Ex. More efficient to gallop at 7m/s than to trot
○
Walk < trot < gallop
!
External work: energy needed to move the mass of the
whole body
!
Internal work: energy needed to move parts of the
body relative to the centre of mass (e.g. energy to
swing the legs)
!
External > internal work
!
Metabolic Energy Usage
Apparent efficiency = (Wint + Wext)/(Met. Energy)
!
*highest efficiency when galloping at 8m/s
!
Energetic Efficiency:
Store and recover energy
!
Suspensory apparatus + long bones --> long springs
!
Check ligaments -tendon can be under strain but
muscle can relax
!
Intramuscular tendons -between equine biceps
!
Reciprocal apparatus -muscles are converted into
tendons
!
Folding of the leg is automatic "spring driven"
reciprocal apparatus
!
'bowed' tendons
○
Ruptured check ligaments
○
Torn suspended ligaments
○
Ex. Navicular syndrome
○
Problems with using tendons as springs:
!
Tendons and Ligaments as springs:
Anatomical Adaptations
in Ungulates
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Document Summary
Shape of horses: *functionally integrated or correlated parts. Long skinny legs - move animal swiftly, with stamina and energy efficiency. To maximize stride length, lengthen the legs (cover more ground in air) Losing the collar bone adds length to the leg: rotation is not at shoulder joint but half way up the shoulder blade. Modified nail co-opted as a weight-bearing component of the musculoskeletal system. *major problem with long bones is an increased risk of fracture. To maintain stride frequency, increase moment of inertia. Big heavy muscles that power the legs are close to the trunk. *makes the shaft of the hammer easier to swing. The fermentation vat: use cellulase-producing microbes to ferment cellulose. Extensive modification of the dentition, caecum and ascending colon. Epaxial and hypaxial lumbar muscles, and thoracolumbar fascia. More efficient to gallop at 7m/s than to trot. External work: energy needed to move the mass of the whole body.
