Cranial Topic 8: Appendicular Skeleton Divisions of the ... · PDF file Topic 8: Appendicular...

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Transcript of Cranial Topic 8: Appendicular Skeleton Divisions of the ... · PDF file Topic 8: Appendicular...

  • 1/9/2013

    1

    Topic 8: Appendicular Skeleton

    � What makes up the appendicular skeleton?

    � What is the pattern of serial homology of the limbs?

    � Tetrapod front limb morphology

    � Tetrapod hind limb morphology

    � How do the limbs develop?

    � What patterns of evolution have limbs undergone?

    � Transition from water to land

    � What are some specializations of the limbs?

    Divisions of the Skeleton:

    Liem et al. Fig. 8-15, 8-18; Dean 1895

    � Cranial

    � Postcranial

    � Axial

    � Appendicular

    What are the components of

    the appendicular skeleton?

    Appendicular Components

    � _____________ � Multiple elements

    � In body proper

    � _____________ � Single long bone

    � _____________ � Two long bones

    � _____________ � Many bones

    � How have these bones developed?

    Modified from Liem et al. Fig. 9-7

    Appendicular Components

    � Girdle � Variable elements (see later)

    � Stylopodium � Humerus

    � Femur

    � Zeugopodium � Radius & Ulna

    � Tibia & Fibula

    � Autopodium � Carpals, Metacarpals & Phalanges

    � Tarsals, Metatarsals & Phalanges

    Liem et al. Fig. 9-10, 9-11

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    Limb Development

    � Starts with formation of ______________

    � What germ layers are involved?

    © P Martin; ncbi.nlm.nih.gov

    Limb Development

    © E Uthman; BioDes; cmrb.eu

    � Early formation of ___________ ________________ (AER)

    � Zone of cell proliferation

    � Zone of differentiation

    � Proximal structures develop first

    � Zone of _______________ (ZPA)

    � Expresses Sonic Hedgehog to define digit polarity

    Limb Development

    � Fibroblast Growth Factor (FGF)

    � Induces AER formation

    � Proliferation of Mesoderm

    � Formation of digits

    � Bone Morphogenetic Protein (BMP)

    � Involved in apoptosis

    � Noggin gene

    � Blocks apoptosis

    © BioDes

    Limb Development

    � Limb element identity

    � _____________ expression patterns

    � Slight differences between front and hind limbs

    Hall, Fig. 7-4

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    Limb Development

    � Solid line indicates limb axis

    � Gene expression data inform us about homology

    � Are tetrapod digits homologous to radials or are they neomorphs?

    Liem et al. Focus 9-1

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    � Front limb differentiation

    � Addition of elements

    � Increased _____________

    of elements

    � Evolution of ___________

    Liem et al. Fig. 9-5, 9-6, 9-8

    Front Limb & Pectoral

    Girdle Evolution

    Liem et al. Fig. 9-5, 9-9, 9-11

    Front Limb & Pectoral

    Girdle Evolution

    Mammal

    � ______________

    � Cleithrum, supracleithrum,

    interclavicle lost

    � Clavicle remains

    � ______________

    � Scapula and coracoid increase in size

    � Coracoid lost in mammals

    � What has happened in terms of what

    elements are

    involved?

    Front Limb & Pectoral Girdle Evolution

    Basal Amphibian

    Benton 1997 pg 183; Benton Fig 4-2a; Pough et al 2004 Fig 2-2

    Panderichthys

    Bony Fish

    � Separation of front limb &

    girdle from the head skeleton

    � Why?

    Hind Limb Evolution

    Liem et al. Fig. 9-4, 9-6, 9-10; Hall 4-3

    � Very similar to front limb evolution � Evolution of autopodium

    � Evolution of digits

    � Increased robustnesss

    Pelvic Girdle Evolution

    � How does this differ

    developmentally from the pectoral girdle?

    � Bones are conserved in

    position

    � _________

    � _________

    � _________

    Liem et al. Fig. 9-4, 9-9, 9-11

    Mammal

    Pelvic Girdle Evolution

    Benton 1997 Fig 3.22; Pough et al 2004 Fig 2-2a

    Acanthostega

    Protopterus

    (African lungfish)

    � Transition in articulation of pelvic girdle

    � Fishes: ______________

    � Tetrapods: solidly articulated with vertebral column

    � Why?

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    Evolution of Limbs

    Transition from water to land

    What are the

    functional reasons for

    each change?

    Terrestrial

    Obligate Aquatic

    What morphological

    changes are involved

    in this evolutionary

    transition?

    Evolution of Limbs

    What are the

    functional reasons for

    each change?

    What morphological

    changes are involved

    in this evolutionary

    transition?

    � �

    So, how does the function of front & hind limbs differ?

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    Specialization of the Limbs

    � Limbs to Fins

    � Shortening of stylopodium & zeugopodium

    � __________________

    � Fusion of digits (not phalanges)

    Storrs, 1993

    Specialization of the Limbs - Wings

    � Digits 1-3 reduced

    � Phalanges in digit 4 elongated

    � Metacarpal 4 elongated

    Liem et al. Fig. 9-12

    ________ _____ ____

    � Loss of digits 1 & 5

    � Digits 2-4 reduced

    � Carpometacarpus

    � Elongation of radius & ulna

    � Phalanges & metacarpals in digits

    2-5 elongated

    � Digit 1 reduced

    � Radius elongated

    � Ulna reduced

    Limb Specializations

    � Limb posture and cursoriality

    � ______________

    � ______________

    � ______________

    � Fusion of tibia & fibula

    � Elongation and fusion of metatarsals

    � Fusion of phalanges

    & loss of digits

    � How does this

    improve speed?

    � What species have each posture?

    © UMMZ

    Limb Specializations

    � A dog at full gallop with long strides

    Liem et al. Fig. 9-14

    Limb Specializations

    � Human skeletal

    adaptations for endurance running

    � Narrow waist

    � Large vertebral centra

    � Relatively short _______

    � Large _______________

    � Long _______________

    � Spring-like ___________

    � Short ______________

    � Relatively ___________

    After Lieberman et al. 2009