Transcript Comparative Anatomy Bone

Comparative Anatomy
Bone
Kardong
Chapters 7, 8, & 9
Part 9
Organization of Skeletal Tissues
Figure 9.1.
Bone Legacy

Exoskeleton or dermal skeleton
Dermal bony armor of ostracoderms
 Bony scales in ancient fish


Cranial dermal armor arose from neural crest
cells

Endoskeleton
Internal to skin
 Where once exoskeleton


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Ex: clavicle, nasal, frontal, and parietal bone
Other endoskeletal elements were never part of
the dermal skeleton

Ex: scapula, vertebrae, ribs, sternum, brain case, and
extremity bones
Bone Evidence



All bone develops from mesenchyme
Neural crest cells
Membrane bone- arises from mesenchyme
without passing through cartilaginous
intermediate


exoskeleton
Replacement bone- arises from existing
cartilage

endoskeleton
Endoskeletal Tissues

Visceral Skeleton
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Jaw cartilages and middle ear bones

Weberian ossicles of fish (are referred to as ear ossicles)

Derived from transverse processes of anterior most vertebrae
Somatic Skeleton
Remaining internal bones developing from
mesoderm proper
 Somite and sclerotome
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Axial Skeleton
Appendicular Skeleton
Vertebrae Development
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Arise from sclerotome cells of somites
Morphogenesis
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Sclerotome divides into posterior and anterior halves
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Halves join with segments of adjacent sclerotomes
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Centrum formed from junction
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Vertebrae are intersegmental
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Myotome doesn’t move
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Posterior segment forms costal process
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Site of rib attachment
Vertebrae Development (cont’d.)
Figure 9.2. (a) sclerotome divides (b)
halves join with adjacent halves of next
sclerotome (c) junction forms centrum (see
book figure 8.12)
Figure 9.3. Developing vertebral column
showing intersegmental position
(see book figure 8.12).
Axial Skeleton Vertebrae
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Cartilaginous or bony
From occipital region to tail
Vertebrae types based on centrum structure

Centrum is common feature in all vertebrae
Centrum Structure
Acelous- flat anterior and posterior surface

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Mammals
Amphicelous- concavities of anterior and posterior
surfaces
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Fish, primitive salamanders
Procelous- concavity on anterior surface
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Most reptiles
Opisthocelous- concavity of posterior surface
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Most salamanders
Heterocelous- saddle-shaped
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Neck of birds and turtles
Figure 9.4. Vertebral types based on articular surface of centra
(book figure 8.4).
Vertebrae Evolution
Transition from
crossopterygians to
labyrinthodonts
Different types of vertebrae
came from primitive,
rachitomous labyrinthodont
vertebrae
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Two pleurocentra and U-shaped
hypocentrum
Hypocentrum is lost and
pleurocentrem enlarges and
gives rise 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 Grouping
Grouped according to body region
Amphibians
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First to possess a cervical vertebrae
Figure 9.7. Regions
of vertebral column.
Figure 9.6. Single
cervical vertebrae of
anuran (book figure
8.13).
Reptile Vertebrae
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Atlas as 1st and axis as
2nd cervicals
Turtle: 8 cervicals, 2
sacrals, 10 dorsals, 1630 caudals
Alligator: 8 cervicals, 11
thoracic, 5 lumbar, 2
sacrals, up to 40
caudals
Figure 9.8. atlas and axis cervical vertebrae.
Figure 9.9. Dorsal view of sacral vertebrae
of vertebrates.
Bird Vertebrae
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Possess atlas and axis
13-14 free cervicals, 4 fused thoracics,
fused synsacrum, free caudals, pygostyle
Figure 9.10. Pigeon vertebral column (see book figure 8.31).

Synsacrum
Fuses with pelvic bone
 Reduction in bone mass

Figure 9.11. Pigeon skeleton: trunk, tail,
and pectoral girdle.
Figure 9.12. Synsacrum and pelvic
girdle left lateral (a) and ventral (b)
views (book figure 8.31).
Mammal Vertebrae
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Most species have 7 cervicals
12 thoracic and 5 lumbar compose dorsal
vertebrae
ancestral mammals possessed ~ 27 presacrals
sacrum 2-5 fused vertebrae (ankylosed)
caudals are variable

primates have 2-5 fused into coccyx
Ribs
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Dogfish- develop dorsal ribs
Most teleost- develop ventral ribs
Tetrapods- have dorsal and ventral ribs
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Current theory is that the tetrapod rib is homologous
to the dorsal rib of fishes
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Primitive tetrapods have bicipital ribs - 2 portions
articulate with vertebrae
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Tuberculum- dorsal head

Capitulum- ventral head
Figure 9.13. Dorsal and ventral ribs
(book figure 8.6 and 8.7).
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Agnathans- no ribs
Amphibians- ribs never
reach sternum
Birds- flat processes
extending off ribs
posteriorly (uncinate
processes)
Figure 9.14. Uncinate processes of bird (see book
figure 8.8).
Figure 9.15. Vertebrae and ribs of alligator
(book figure 8.2).
Sternum
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Strictly a tetrapod structure
Amphibians- poorly formed
Reptiles - cartilaginous plates
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Snakes, legless lizards, turtles have no sternum
Alligator- extends down belly
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Ribs fused it sternum
Gastralia
Figure 9.16. Ribs and gastralia of alligator (book figure
8.2).
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Birds- unusual, keeled sternum in
carinates
Mammals- well developed sternum
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Rod shaped
Segments: manubrium, sternebrae,
xiphisternum and xiphoid process
Figure 9.17. Keeled sternum of bird
(book figure 8.8).
Figure 9.18. Tetrapod sterna
(book figure 8.8).
Heterotopic Bone

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Develop by endochondral or intramembranous
ossification
In areas subject to continual stress
Ex: Os cordis, rostral bone, os penis, os clitoridis
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Os cordis- interventricular septum in deer
heart
Rostral bone- snout of pig
Os penis (baculum)- embedded in penis of
lower primates
Os clitoridis- embedded in clitoris of otters
Others include falciform, sesamoid, patella,
pisiform
Figure 9.19. Heterotopic
bones.
Skull and Visceral Skeleton

Two functionally independent cartilaginous components derived from
replacement bone
1. Neurocranium
(= chondrocranium)
2. Splanchnocranium
Figure 9.20. Dog skull. Sources of
the various bones are outlined:
dermatocranium (pink),
neurocranium (= chondrocranium)(blue); splanchnocranium (yellow)
Neural Crest Contributions to the Skull
Figure 9.21.
Neurocranium
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Protects brain and anterior part of spinal cord
Sense organ capsules
Cartilaginous brain case is embryonic adaptation
Four ossification centers
Figure 9.22. Development of cartilaginous
neurocranium (book figure 7.3).
Neurocranium Ossification Centers
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Occipital region
Sphenoid region
Ethmoid region
Otic region
Figure 9.23. Neurocranium of human skull.

Occipital Region
Basioccipital, 2 exoccipitals,
supraoccipital
 Forms single occipital bone in mammals
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Sphenoid Region
Basisphenoid, orbitosphenoid,
presphenoid, laterosphenoid
 Fuse to form one sphenoid
bone in mammals

Figure 9.24. Sphenoid bone.
Figure 9.26. 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.
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Ethmoid Region
Anterior to sphenoid
 Cribriform plate, olfactory foramina, terminals,
mesamoid
 Fuse to form ethmoid in mammals
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Otic Region
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Three bones in tetrapods
Prootic
 Opisthotic
 Epiotic
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Unite to form petrosal bone in birds and mammals
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Forms temporal in mammals
Figure 9.27. Temporal bone of human skull
(book figure 9.28).
Figure 9.28. Multiple nature of temporal
bone of mammals (see book figure 7.53).
Figure 9.29. Intramembranous ossification of
human skull. Embryonic, cartilaginous
neurocranium is black. Neurocranial bones are
red. Other is dermal mesenchyme.
Splanchnocranium

Viscerocranium, although a
misnomer.
- Visceral arches
- Branchial region
Figure 9.30. Primitive splanchnocranium.
Figure 9.31. Splanchnocranium of human.
Skeletal derivatives of 2nd through 5th
pharyngeal arches (see book Table 7.2).
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1st visceral arch- mandibular
 Meckel’s cartilage  malleus
 Palatoquadrate (quadrate)  incus
2nd visceral arch- hyoid
 hyomandibula  columella (stapes)
 ceratohyal  styloid process and anterior
horn of hyoid
 basihyal  body of hyoid
Figure 9.32. Caudal end of
Meckel’s cartilage and developing
middle ear cavity.
Viscerocranial Derivatives
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Alisphenoid- part of sphenoid
Malleus, incus- 1st arch
Stapes- 2nd arch
Styloid- 2nd arch
Hyoid- mainly basihyal
Figure 9.33. Derivatives of the human
visceral skeleton (red).
Figure 9.34. Skeletal derivatives of pharyngeal arches (book Table 7.2).
Dermatocranium
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Membrane bone, not replacement bone
Dermal bones of skull
Upper jaw and face, palates, mandible
Figure 9.35. Pattern that tetrapod dermatocrania (see book
figure 7.10).
Dermatocranium (con’t.)
Figure 9.36. Dog skull showing
dermatocranium (pink), chondrocranium
(blue), and splanchnocranium (yellow).
Figure 9.37. Hypothetical derivations of skull
bones. (Box Essay 7.1)
Dermatocranial Elements
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Nasal, frontal, parietal, squamosal (facial and roofing bones)
Dentary
Vomer, palatine, pterygoid (primary palate)
Premaxilla, maxillary, jugal (secondary palate)
Figure 9.38. Lizard skull.
Evolution of Mammalian Middle Ear Bones
Figure 9.39. (book figure 7.55).
Phylogeny of the
Splanchnocranium
Figure 9.40. (book figure 7.66).
Appendicular Skeleton
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Pectoral Girdle
Pelvic Girdle
Appendages
Adaptations for Speed
Pectoral Girdle

2 sets of elements: cartilage or replacement
bone/membrane bone
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Replacement bones
 Coracoid, scapula, suprascapula
Membrane bones
 Clavicle, cleithrum, supracleithrum

Figure 9.41. Pectoral girdle along phylogenetic lines.
Dermal bones are red. Replacement bones are
black.
Reduction in number of
bones through evolution
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Shark- only cartilagenous
components
Alligator- retains only
replacement bone elements, no
dermal bone
Mammals
 Scapula of replacement bone
 Clavicle of membrane bone
Birds- two clavicles form furcula
(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 Girdle
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No dermal elements
Three replacement bones
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Ilium, ischium, pubis
Triradiate pelvic girdlealligator and dinosaur
Figure 9.45. Left halves of pelvic girdles showing
parallel evolution.
Summary of Pelvic Girdle Evolution
Figure 9.46. (book
figure 9.21).
Appendages
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Single unit most medial in both fore and hind limbs
Two 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).
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Small set of bones at wrist and ankle
Pentameristic pattern of phalanges
Reduction in number and position of
phalanges
Figure 9.50. Evolution of fins to limbs.
Figure 9.51. Adaptations in
secondarily aquatic tetrapods.
(book figure 9.30)
Adaptations for Speed

Plantigrade
Flat on the ground
 Primates
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Digitigrade
Elevated
 Carnivores
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Unguligrade
Reduction in digits
 Two types

Figure 9.52. Plantigrade, digitigrade, and unguligrade
feet. Ankle bones are black. Metatarsals are gray.
Unguligrade Adaptations
Reduction in digits

Perissodactyl
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Odd toed
Mesaxanic foot
- Weight on enlarged middle
digit
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Ex: horse
Artidodactyl
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Even toed
Paraxonic foot
- Weight equally distributed
on 3rd and 4th digits

Ex: 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 Limbs

Serpentine
Lateral undulation
 Wave motion
 Minimum 3 contact points
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
(a)
Rectilinear
Straight line
 Scutes on belly lift
 Costocutaneous muscles
move the skin

(b)
(c)
Figure 9.55. Serpentine locomotion (a) and
rectilinear locomotion (b & c)
Locomotion Without Limbs (cont’d.)
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Sidewinding
Minimum 2 contact points
 Adaptation in sandy habitats
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Concertina
Minimum 2 contact points
 Allows snake to move up
gutter

(a)
(b)
Figure 9.56. Sidewinding locomotion (a)
and concertina locomotion (b)
Brachiation: Human Limb Engineering
Figure 9.57. (book page 354).
Five to 10 million years have passed
since distant human ancestors swung
through trees (Kardong, 2013).