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Comparative Anatomy > Biomechanics > Flashcards

Biomechanics Flashcards

0
Q

Simply define biomechanics

A

Functional morphology

Effect of gravity

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1
Q

Define morphology

A

Basis of everything

Physical dimensions

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2
Q

Define energetics

A

Energetic equilibrium

Eg. Don’t starve

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3
Q

Define optimisation

A

Most efficient, energetic low cost solution for…
Morphology e.g. Musculoskeletal system
Function e.g. Contraction of muscles
Biological role e.g. Arm abduction to collect food

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4
Q

Define locomotor form

A

Morphology
= quadrupedal, bipedal, caudal

May change during an individual’s ontogenic development
e.g humans are originally quadrupedal before exclusively bipedal

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5
Q

Define locomotor type

A

Function
= walking, running, crawling, hopping, brachiating, leaping

Leaping can be bipedal (frogs) and quadrupedal (toads)

Usually decreases in number but increases in proficiency
Almost all animals use a variety - ‘trying them out’

Bipedal doesn’t conclude the type of moment
e.g walking/running/skipping

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6
Q

Cursorial animals are…

A

Animals that travel far, fast or easily on the ground

Quadrupedal cursors evolve from walkers
- predators or medium/large herbivores e.g sand lizard

Bipedal cursors balance body over the legs e.g ostrich

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7
Q

Saltatorial animals are…

A

Animals that jump or hop

Often, but not always, bipedal

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8
Q

Ricochet animals are…

A

Animals whose hindlimbs are used in unison for a succession of jumps e.g kangaroo

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9
Q

Characteristics relating to mammalian cursors are…

A

Flexion/extension of spine
Passage of hindlimbs outside forefeet
Varied position of shoulder

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10
Q

Tetrapod limbs

A

Forelimb and hindlimb

  • stylopodium (proximal)
  • zygopodium (middle)
  • autopodium (distal)

Can be further subdivided, mainly in the autopodium

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11
Q

Autopodium

A

Distal

Most variety as it is in contact with the habitat
tree/ground fast/slow powerful/not

Gravity pull

Elongated tarus in specialised leapers
Shorter digits in powerful climber

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12
Q

Characteristics of bipedal leapers

A

(Relatively:)
Short forelimbs
Long hindlimbs, elongated feet

Grip:

  • large palmar surface
  • particularly large plantar surface area
  • adduction of the hallux
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13
Q

Frogs adaptations to bipedal leaping…

A

Vertebral column is short (shorter than pelvis and ilium)
Composed of 9 vertebrae which are fused - urostyle

Short forelimbs, elongated hindlimbs (esp. autopodium)

Fibula and tibia are fused (zygopodium)
- reduced ability to rotate = increased stability

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14
Q

Amphibian and reptilian limb position

A

EG. salamander turtle lizards

Trunk is slung between limbs and frequently touches the ground

Limbs set at almost right angles to the body and digits point laterally
= not efficient

Radius/ulna tibia/fibula flexed at 90 degrees

Axes of all joints are directed parallel to the vertebral column

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15
Q

Mammalian limb position

A

ROTATION
= inline/parallel with body axis
Hindlimb - forward, forelimb - backward
More energy efficient

Limbs sagittal under or alongside trunk

POSTURE
-in late therapsids, limbs carried more under the body
=reflection of increased efficiency in locomotion

DIGIT ORIENTATION
Torsion of the humerus (rotated) and femur brought toes forward inline with the direction of travel
= efficient

SHOULDER GIRDLE
- limbs under the body so force is diverted more vertically (no need for interclavicular bone which supports sprawled postures)

PELVIC GIRDLE
rapid locomotion is common, so the orientation changes so that forward thrust of hindlimbs is more in alignment with the line of travel
= force transferred to vertebral column

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16
Q

How a cat skeleton relates to a human (limb position)

A

Forearm bones must cross to a pronated position so volar surfaces can rest on the ground
(No need in hindlimbs, thigh already rotated forward)
Essentially preserved in humans

17
Q

Body size and limb design

- basic principles

A

Muscle force = linear dimensions (power of 2)
Mass is cubed

So… Small leapers can develop relatively more muscle

Limbs bear the mass of the body
Strength is proportional to their cross sectional area
Change in body size =
10 fold increase in diameter
1000 fold increase in mass
100 fold increase in cross-sectional area
This is why gravity has a greater impact on larger animals

18
Q

Centre of mass - basic principles

A

“The single point at which the mass of the body can thought to be concentrated”

Security of stance is greater, the lower the position of the CoM is
Static equilibrium in vertebrates requires that the vertical from the CoM touches the ground within the area limits e.g forelimb - hindlimb

19
Q

Primitive traits of Hadar Hominids (Lucy)

A

Long , curved proximal phalanges
Thorax funnel shaped
Scapula with cranially orientated glenoid
Midthoracic vertebrate with ventrally expanded centra
Iliac blades face posteriorly

20
Q

Postcranial synapomorphies (=shared derived features) of the Hader Hominids and Homo Sapiens

A

Sacral retroflexion
Pelvis superinferiorly shortened and anteriorly rotated iliac blades
Long femoral neck
Distal femur has high bicondylar angle and elliptical lateral condyle
Calcenous has massive body
Strong transverse and longitudinal arch
Hallux is convergent and toes relatively short
Relatively small forelimbs

21
Q

Difference is mass distribution within the hindlimb

A

Humans : 62% 29% 9%
Galgo : 67% 22% 11% - Saltorial
Femur ——Feet
More muscle mass proximally makes leaping more efficient
Feet relatively heavier and longer
= increases acceleration distance, grasping

22
Q

Avatisms in the feet of horses

A

Modern horses are unguligrade (have only 1 enlarged and elongated digit on each foot)
Evolved from ancestors with 3 or 4 toes, ‘lost’ toes or remnants can rarely reappear
= evidence of presence of underlying ancestral developmental pattern

23
Q

Changes in foot postures: Plantigrady - digitigrade - unguligrade

What does this mean for the animal?

A

Lengthens the limb and increases the length of stride

24
Q

Carnivore (dog) vs Herbivore (equid): foot posture

A

DOG
requires limb flexibility and control for manipulating prey
Trunk flexion/extension
Nail is a tool

Digitigrade

EQUID
Running, grazing, standing with minimal energy expenditure
Fetlock translation

Unguligrade

25
Q

What does the navicular in horses resemble in other animals

A

Sesamoid bone like the patella in form and function

26
Q

Fetlock joints:

A

(Equids)

Energy saving mechanism
Impact bends the joint, which stretches the suspensory/springing ligaments - energy of deformation is recovered

Would take ~700KG to break the ligament

27
Q

Cursor specialisations of the Ulna

A

Especially prominent in large cursors

Rotation of the forearm lost

 - huge reduction in corresponding muscle mass 
 - ulna must be retained for elbow joint
28
Q

Cursor specialisation of the Fibula

A

Reduced as foot twisting and rotating mechanisms aren’t needed

29
Q

Cursor specialisation of the joints

A

Deeper patellar groove at distal end of femur, more marked trochlea & grooves at distal end of humerus

More block like carpals at the wrist

                                                              = joints function as hinge joints  Allow motion in the line of travel only  Compensate for bracing lost as muscles are reduced/eliminated  Guard against dislocations
30
Q

Type of muscle used if fast displacement is required?

A

Long muscle

WHY?
Point of insertion in a long muscle has a greater velocity and moves a greater distance than in a short muscle

31
Q

Cross-sectional area in pinnate muscle

A

Pinnate = oblique to line of action

This orientation permits the packing of more fibres within the same volume than parallel arrangements do

Reduces the effective distance through which the insertion can be moved - reduces the force that each fibre can direct along the line of action BUT greater overall number of fibres compensates

Suited for moving heavy loads short distances

32
Q

Distal insertion is suited to…

A

Strength

33
Q

Proximal insertion is suited to…

A

Speed

34
Q

Low gear muscle

A

The larger the distance between muscle insertion and joint centre, the lower the rate and degree of rotation leading to a reduced limb excursion

Acceleration

Semimembranousus

35
Q

High gear muscle

A

Sustaining velocity e.g gluteus medius

36
Q

Chimpanzee foot morphology

A

Flat feet that are highly dexterous
Strong thumb like opposable big toes - climbing, grasping
Additional hallux musculature
Highly flexible midfoot

37
Q

Foot morphologies specialised for bipedal leaping

A

Elongated navicular and calcenus

Opposable hallux

38
Q

Adaptations of muscle architecture - gluteal muscles - humans

A

Importance for bipedal waking, indicated by:

  • gluteus superficialis is the correct term for all species except Homo sapiens (not as large and heavy)
  • formation of classic bum shape via tilting of the pelvis
39
Q

Adaptations of muscle architecture - kangaroos - hindlimb

A

Large energy savings by elastic storage of energy in gastrocnemius and plantaris tendons

Proximal position of musculature

40
Q

Why is relative lengthening of the hindlimbs and their distal segments more extreme for saltators than cursors

A

Mass is a third power function

41
Q

Claw function of a carnivore

A

Cursors cannot fully dedicate leg morphology to speed - predation
Proximal mass concentration in thigh is compromised by claw function…
Protract - predation, retract - running

…and its associated muscles

Comparative Anatomy (8 decks)

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