Comparative AnatomyComparative AnatomyBoneBone

Source: Source: Kardong Kardong

Chapters 7, 8, & 9Chapters 7, 8, & 9

Organization of Skeletal TissuesOrganization of Skeletal Tissues

Figure 9.1.

Bone LegacyBone Legacy

Exoskeleton or dermal skeletonExoskeleton or dermal skeleton Dermal bony armor of ostracodermsDermal bony armor of ostracoderms Bony scales in ancient fishBony scales in ancient fish

Cranial dermal armor arose from neural crest Cranial dermal armor arose from neural crest cellscells

EndoskeletonEndoskeleton Internal to skinInternal to skin Where once exoskeleton Where once exoskeleton

Ex: clavical, nasal, frontal, and parietal boneEx: clavical, nasal, frontal, and parietal bone Other endoskeletal elements were never part of Other endoskeletal elements were never part of

the dermal skeletonthe dermal skeleton Ex: scapula, vertebrae, ribs, sternum, brain case, and Ex: scapula, vertebrae, ribs, sternum, brain case, and

extremity bonesextremity bones

Bone EvidenceBone Evidence

All bone develops from mesenchymeAll bone develops from mesenchyme Neural crest cellsNeural crest cells Membrane boneMembrane bone- arises from mesenchyme - arises from mesenchyme

without passing through cartilaginous without passing through cartilaginous intermediateintermediate exoskeletonexoskeleton

Replacement boneReplacement bone- arises from existing cartilage- arises from existing cartilage endoskeletonendoskeleton

Endoskeletal TissuesEndoskeletal Tissues Visceral SkeletonVisceral Skeleton

Jaw cartilages and ear ossiclesJaw cartilages and ear ossicles Weberian ossicles of fish (ear ossicles)Weberian ossicles of fish (ear ossicles)

Derived from transverse processes of anterior most Derived from transverse processes of anterior most vertebraevertebrae

Somatic SkeletonSomatic Skeleton Remaining internal bones developing from Remaining internal bones developing from

mesoderm propermesoderm proper Somite and scleratomeSomite and scleratome

Axial SkeletonAxial Skeleton Appendicular SkeletonAppendicular Skeleton

Vertebrae DevelopmentVertebrae Development

Arise from sclerotome cells of somitesArise from sclerotome cells of somites MorphogenesisMorphogenesis

Sclerotome divides into posterior and anterior halvesSclerotome divides into posterior and anterior halves Halves join with segments of adjacent sclerotomesHalves join with segments of adjacent sclerotomes Centrum formed from junction Centrum formed from junction Vertebrae are intersegmentalVertebrae are intersegmental Myotome doesn’t moveMyotome doesn’t move Posterior segment forms costal processPosterior segment forms costal process

Site of rib attachmentSite of rib attachment

Figure 9.3. Developing vertebral column showing intersegmental position (see book figure 8.12).

Figure 9.2. (a) sclerotome divides (b) halves join with adjacent halves of next sclerotome (c) junction forms centrum (see book figure 8.12)

Vertebrae Development (cont’d.)Vertebrae Development (cont’d.)

Axial Skeleton VertebraeAxial Skeleton Vertebrae Cartilaginous or bonyCartilaginous or bony From occipital region to tailFrom occipital region to tail Vertebrae types based on centrum structureVertebrae types based on centrum structure

Centrum is common feature in all vertebraeCentrum is common feature in all vertebrae

Centrum StructureCentrum Structure Acelous- flat anterior and posterior surfaceAcelous- flat anterior and posterior surface

MammalsMammals Amphicelous- concavities of anterior and posterior Amphicelous- concavities of anterior and posterior

surfacessurfaces Fish, primitive salamandersFish, primitive salamanders

Procelous- concanvity on anterior surfaceProcelous- concanvity on anterior surface Most reptilesMost reptiles

Opisthocelous- concavity of posterior surfaceOpisthocelous- concavity of posterior surface Most salamandersMost salamanders

Heterocelous- saddle-shapedHeterocelous- saddle-shaped Neck of birds and turtlesNeck of birds and turtles

Figure 9.4. Vertebral types based on articular surface of centra (book figure 8.4).

Vertebrae EvolutionVertebrae Evolution Transition from crossopterygians Transition from crossopterygians

to labyrinthodontsto labyrinthodonts Different types of vertebrae came Different types of vertebrae came

from primitive, rachitomous from primitive, rachitomous labyrinthodont vertebraelabyrinthodont vertebrae

Two pleurocentra and U-shaped Two pleurocentra and U-shaped hypocentrumhypocentrum

Hypocentrum is lost and Hypocentrum is lost and pleurocentrem enlarges and gives pleurocentrem enlarges and gives rise to centrum of modern amnioterise to centrum of modern amniote

Figure 9.5. Modifications from labyrinthodont to modern amniote vertebrae. Hypocentrum is diagonal lines. Pleurocentrum is red (see book figure 8.3).

Vertebrae GroupingVertebrae Grouping Grouped according to body regionGrouped according to body region AmphibiansAmphibians

First to possess a cervical vertebraeFirst to possess a cervical vertebrae

Figure 9.6. Single cervical vertebrae of anuran (book figure 8.13).

Figure 9.7. Regions of vertebral column.

Reptile VertebraeReptile Vertebrae

Atlas as 1st and axis as Atlas as 1st and axis as 2nd cervicals2nd cervicals

Turtle: 8 cervicals, 2 Turtle: 8 cervicals, 2 sacrals, 10 dorsals, 16-sacrals, 10 dorsals, 16-30 caudals30 caudals

Alligator: 8 cervicals, 11 Alligator: 8 cervicals, 11 thoracic, 5 lumbar, 2 thoracic, 5 lumbar, 2 sacrals, up to 40 sacrals, up to 40 caudalscaudals

Figure 9.9. Dorsal view of sacral vertebrae of vertebrates.

Figure 9.8. atlas and axis cervical vertebrae.

Bird VertebraeBird Vertebrae

Possess atlas and axisPossess atlas and axis 13-14 free cervicals, 4 fused thoracics, 13-14 free cervicals, 4 fused thoracics,

fused synsacrum, free caudals, pygostylefused synsacrum, free caudals, pygostyle

Figure 9.10. Pigeon vertebral column (see book figure 8.31).

SynsacrumSynsacrum Fuses with pelvic boneFuses with pelvic bone Reduction in bone massReduction in bone mass

Figure 9.12. Synsacrum and pelvic girdle left lateral (a) and ventral (b) views (book figure 8.31).

Figure 9.11. Pigeon skeleton: trunk, tail, and pectoral girdle.

Mammal VertebraeMammal Vertebrae

Most species have 7 cervicalsMost species have 7 cervicals 12 thoracic and 5 lumbar compose dorsal 12 thoracic and 5 lumbar compose dorsal

vertebraevertebrae ancestral mammals possessed ~ 27 presacralsancestral mammals possessed ~ 27 presacrals sacrum 2-5 fused vertebrae (ankylosed)sacrum 2-5 fused vertebrae (ankylosed) caudals are variablecaudals are variable

primates have 2-5 fused into coccyxprimates have 2-5 fused into coccyx

RibsRibs Dogfish- develop dorsal ribsDogfish- develop dorsal ribs Most teleost- develop ventral ribsMost teleost- develop ventral ribs Tetrapods- have dorsal and ventral ribsTetrapods- have dorsal and ventral ribs

Current theory is that the tetrapod rib is homologous Current theory is that the tetrapod rib is homologous to the dorsal rib of fishesto the dorsal rib of fishes

Primitive tetrapods have bicipital ribs - 2 portions Primitive tetrapods have bicipital ribs - 2 portions articulate with vertebraearticulate with vertebrae

Tuberculum- dorsal headTuberculum- dorsal head Capitulum- ventral headCapitulum- ventral head

Figure 9.13. Dorsal and ventral ribs (book figure 8.6 and 8.7).

Agnathans- no ribsAgnathans- no ribs Amphibians- ribs never Amphibians- ribs never

reach sternumreach sternum Birds- flat processes Birds- flat processes

extending off ribs extending off ribs posteriorly (unicate posteriorly (unicate processes)processes)

Figure 9.14. Unicate processes of bird (see bookfigure 8.8).

Figure 9.15. Vertebrae and ribs of alligator (book figure 8.2).

SternumSternum Strictly a tetrapod structureStrictly a tetrapod structure Amphibians- poorly formedAmphibians- poorly formed Reptiles - cartilaginous platesReptiles - cartilaginous plates

Snakes, legless lizards, turtles have no sternumSnakes, legless lizards, turtles have no sternum Alligator- extends down bellyAlligator- extends down belly

Ribs fused it sternumRibs fused it sternum GastraliaGastralia

Figure 9.16. Ribs and gastralia of alligator (book figure8.2).

Birds- unusual, keeled sternum in Birds- unusual, keeled sternum in carinatescarinates

Mammals- well developed sternumMammals- well developed sternum Rod shapedRod shaped Segments: manubrium, sternebrae, Segments: manubrium, sternebrae,

xiphisternum and xiphoid processxiphisternum and xiphoid process

Figure 9.18. Tetrapod sterna (book figure 8.8).

Figure 9.17. Keeled sternum of bird (book figure 8.8).

Heterotopic BoneHeterotopic Bone

Develop by endochondral or intramembranous Develop by endochondral or intramembranous ossification ossification

In areas subject to continual stressIn areas subject to continual stressEx: Os cordis, rostral bone, os penis, os clitoridisEx: Os cordis, rostral bone, os penis, os clitoridis

Os cordis- interventricular septum in deer Os cordis- interventricular septum in deer heartheart

Rostral bone- snout of pigRostral bone- snout of pig Os penis (baculum)- embedded in penis of Os penis (baculum)- embedded in penis of

lower primateslower primates Os clitoridis- embedded in clitoris of ottersOs clitoridis- embedded in clitoris of otters Others include falciform, sesamoid, patella, Others include falciform, sesamoid, patella,

pisiformpisiform

Figure 9.19. Heterotopic bones.

Skull and Visceral SkeletonSkull and Visceral Skeleton Two functionally independent cartilaginous components derived from Two functionally independent cartilaginous components derived from

replacement bonereplacement bone1. Neurocranium 1. Neurocranium

(= chondrocranium)(= chondrocranium)2. Splanchnocranium2. Splanchnocranium

Figure 9.20. Dog skull. Sources ofthe various bones are outlined: dermatocranium (pink),neurocranium (= chondrocranium)-(blue); splanchnocranium (yellow)

Neural Crest Contributions to the Skull

Figure 9.21.

NeurocraniumNeurocranium Protects brain and anterior part of spinal cordProtects brain and anterior part of spinal cord Sense organ capsulesSense organ capsules Cartilaginous brain case is embryonic adaptationCartilaginous brain case is embryonic adaptation Four ossification centersFour ossification centers

Figure 9.22. Development of cartilaginous neurocranium (book figure 7.3).

Neurocranium Ossification CentersNeurocranium Ossification Centers

Occipital regionOccipital region Sphenoid regionSphenoid region Ethmoid regionEthmoid region Otic regionOtic region

Figure 9.23. Neurocranium of human skull.

Occipital RegionOccipital Region Basioccipital, 2 exoccipitals, suproccipitalBasioccipital, 2 exoccipitals, suproccipital Forms single occipital bone in mammalsForms single occipital bone in mammals

Sphenoid RegionSphenoid Region Basisphenoid, orbitosphenoid, Basisphenoid, orbitosphenoid,

presphenoid, laterosphenoidpresphenoid, laterosphenoid Fuse to form one sphenoid Fuse to form one sphenoid

bone in mammalsbone in mammals

Figure 9.24. Sphenoid bone.

Figure 9.25. Human skull (a) cribriform plate (b) frontal bone (c) temporal bone (d) ethmoid bone (e) sphenoid bone (f) foramen magnum.

Figure 9.26. Sphenoid bone.

Ethmoid RegionEthmoid Region Anterior to sphenoidAnterior to sphenoid Cribriform plate, olfactory foramina, terminals, Cribriform plate, olfactory foramina, terminals,

mesamoid mesamoid Fuse to form ethmoid in mammalsFuse to form ethmoid in mammals

Otic Region Otic Region Three bones in tetrapodsThree bones in tetrapods

ProoticProotic OpisthoticOpisthotic EpioticEpiotic

Unite to form petrosal bone in birds and mammalsUnite to form petrosal bone in birds and mammals Forms temporal in mammalsForms temporal in mammals

Figure 9.28. Multiple nature of temporal bone of mammals (see book figure 7.53).

Figure 9.27. Temporal bone of human skull (book figure 9.28).

Figure 9.29. Intramembranous ossification of human skull. Embryonic, cartilaginous neurocranium is black. Neurocranial bones are red. Other is dermal mesenchyme.

SplanchnocraniumSplanchnocranium Visceral cranium, although Visceral cranium, although

a misnomer.a misnomer.- Visceral arches- Visceral arches- Branchial region- Branchial region

Figure 9.31. Splanchnocranium of human. Skeletal derivatives of 2nd through 5th pharyngeal arches (see book Table 7.2).

Figure 9.30. Primitive splanchnocranium.

1st visceral arch- mandibular1st visceral arch- mandibular Meckel’s cartilage Meckel’s cartilage malleus malleus Palatoquadrate (quadrate) Palatoquadrate (quadrate) incus incus

2nd visceral arch- hyoid2nd visceral arch- hyoid hyomandibula hyomandibula columella (stapes) columella (stapes) ceratohyal ceratohyal styloid process and anterior styloid process and anterior

horn of hyoidhorn of hyoid basihyal basihyal body of hyoid body of hyoid

Figure 9.32. Caudal end of Meckel’s cartilage and developing middle ear cavity.

Visceral-Cranial DerivativesVisceral-Cranial Derivatives

Alisphenoid- part of sphenoidAlisphenoid- part of sphenoid Malleus, incus- 1st archMalleus, incus- 1st arch Stapes- 2nd archStapes- 2nd arch Styloid- 2nd archStyloid- 2nd arch Hyoid- mainly basihyalHyoid- mainly basihyal

Figure 9.33. Derivatives of the human visceral skeleton (red).

Figure 9.34. Skeletal derivatives of pharyngeal arches (book Table 7.2).

DermatocraniumDermatocranium Membrane bone, not replacement boneMembrane bone, not replacement bone Dermal bones of skullDermal bones of skull Upper jaw and face, palates, mandibleUpper jaw and face, palates, mandible

Figure 9.35. Pattern that tetrapod dermatocrania (see book figure 7.10).

Figure 9.37. Endochondral bones (red) of mammalian skull.

Figure 9.36. Dog skull showing dermatocranium (pink), chondrocranium (blue), and splanchnocranium (yellow).

DermatocraniumDermatocranium (con’t)(con’t)

Dermatocranial ElementsDermatocranial Elements NasalNasal SquamosalSquamosal Secondary palate- maxillary, jugalSecondary palate- maxillary, jugal Primary palate- palatine, dentaryPrimary palate- palatine, dentary

Figure 9.38. Lizard skull.

Evolution of Mammalian Middle Ear BonesEvolution of Mammalian Middle Ear Bones

Figure 9.39. (book figure 7.55).

Phylogeny of the Splanchnocranium

Figure 9.40. (book figure 7.66).

Appendicular SkeletonAppendicular Skeleton Pectoral GirdlePectoral Girdle Pelvic GirdlePelvic Girdle AppendagesAppendages Adaptations for SpeedAdaptations for Speed

Pectoral GirdlePectoral Girdle 2 sets of elements: cartilage or replacement 2 sets of elements: cartilage or replacement

bone/membrane bonebone/membrane bone

Replacement bonesReplacement bones Coracoid, scapula, suprascapulaCoracoid, scapula, suprascapula

Membrane bonesMembrane bones Clavicle, cleithrum, supracleithrumClavicle, cleithrum, supracleithrum

Figure 9.41. Pectoral girdle along phylogenetic lines. Dermal bones are red. Replacement bones are black.

Reduction in number of Reduction in number of bones through evolutionbones through evolution

Shark- only cartilagenous Shark- only cartilagenous componentscomponents

Alligator- retains only Alligator- retains only replacement bone elements, no replacement bone elements, no dermal bonedermal bone

Mammals Mammals Scapula of replacement bone Scapula of replacement bone Clavicle of membrane boneClavicle of membrane bone

Birds- two clavicles form furcula Birds- two clavicles form furcula (wishbone)(wishbone)

(a)

(b)

Figure 9.42. Pectoral girdles of (a) Polypterus and (b) shark.. Dermal bones are red. Replacement bones are black.

Fish – Tetrapod Transition

Figure 9.43. (book figure 9.16).

Summary of Pectoral Girdle Evolution

Figure 9.44. (book figure 9.19).

Pelvic GirdlePelvic Girdle

No dermal elementsNo dermal elements Three replacement bonesThree replacement bones

Ilium, ischium, pubisIlium, ischium, pubis Triradiate pelvic girdle- Triradiate pelvic girdle-

alligator and dinosauralligator and dinosaur

Figure 9.45. Left halves of pelvic girdles showing parallel evolution.

Summary of Pelvic Girdle Evolution

Figure 9.46. (bookfigure 9.21).

AppendagesAppendages

Single unit most medial in both fore and hind limbsSingle unit most medial in both fore and hind limbs Two units in distal region of fore and hind limbTwo units in distal region of fore and hind limb

Figure 9.47. Dorsal view of left forelimb or forefin of Devonian tetrapods.

Figure 9.48. Cladogram of lobe-Fin fishes and amphibians.

Figure 9.49. Basic organization of fore- and hindlimb (book figure 9.23).

Small set of bones at wrist and ankleSmall set of bones at wrist and ankle Pentameristic pattern of phalangesPentameristic pattern of phalanges Reduction in number and position of Reduction in number and position of

phalangesphalanges

Figure 9.50. Evolution of fins to limbs.

Figure 9.51. Adaptations in secondarily aquatic tetrapods.(book figure 9.30)

Adaptations for SpeedAdaptations for Speed

PlantigradePlantigrade Flat on the groundFlat on the ground Primates Primates

DigitigradeDigitigrade ElevatedElevated CarnivoresCarnivores

UnguligradeUnguligrade Reduction in digitsReduction in digits Two typesTwo types Figure 9.52. Plantigrade, digitigrade, and unguligrade

feet. Ankle bones are black. Metatarsals are gray.

Unguligrade AdaptationsUnguligrade Adaptations Reduction in digitsReduction in digits

PerissodactylPerissodactyl Odd toedOdd toed Mesaxanic footMesaxanic foot

- Weight on enlarged middle - Weight on enlarged middle digitdigit

Ex: horseEx: horse

ArtidodactylArtidodactyl Even toedEven toed Paraxonic footParaxonic foot

- Weight equally distributed - Weight equally distributed on 3on 3rdrd and 4 and 4thth digits digits

Ex: camelEx: camel

Figure 9.53. Unguligrade adaptations in horse and camel. Bones lost are white (see book figure 9.39).

Skeletal Adaptations for Digging

Figure 9.54. (book figure 9.58).

Locomotion Without LimbsLocomotion Without Limbs

SerpentineSerpentine Lateral undulationLateral undulation Wave motionWave motion Minimum 3 contact pointsMinimum 3 contact points

RectilinearRectilinear Straight lineStraight line Scutes on belly liftScutes on belly lift Costocutaneous muscles Costocutaneous muscles

move the skinmove the skinFigure 9.55. Serpentine locomotion (a) and rectilinear locomotion (b & c)

(a)

(b)

(c)

SidewindingSidewinding Minimum 2 contact pointsMinimum 2 contact points Adaptation in sandy habitats Adaptation in sandy habitats

ConcertinaConcertina Minimum 2 contact pointsMinimum 2 contact points Allows snake to move up Allows snake to move up

guttergutter

Locomotion Without Limbs (cont’d.)Locomotion Without Limbs (cont’d.)

(a) (b)

Figure 9.56. Sidewinding locomotion (a) and concertina locomotion (b)

Brachiation: Human Limb Engineering

Figure 9.57. (book page 354).