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Comparative Anatomy Bone

Comparative Anatomy Bone. Note Set 7 Chapters 7, 8, & 9. 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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Comparative Anatomy Bone

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  1. Comparative AnatomyBone Note Set 7 Chapters 7, 8, & 9

  2. Bone Legacy • Exoskeleton or dermal skeleton • Dermal bony armor of ostracoderms • Bony scales in ancient fish • Cranial dermal armor arose from neural crest cells

  3. Endoskeleton • Internal to skin • Where once exoskeleton • 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

  4. 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

  5. Endoskeletal Tissues • Visceral Skeleton • Jaw cartilages and ear ossicles • Weberian ossicles of fish (ear ossicles) • Derived from transverse processes of anterior most vertebrae • Somatic Skeleton • Remaining internal bones developing from mesoderm proper • Somite and scleratome • Axial Skeleton • Appendicular Skeleton

  6. Vertebrae Development • Arise from sclerotome cells of somites • Morphogenesis • Sclerotome divides into posterior and anterior halves • Halves join with segments of adjacent sclerotomes • Centrum formed from junction • Vertebrae are intersegmental • Myotome doesn’t move • Posterior segment forms costal process • Site of rib attachment

  7. Vertebrae Development Figure 9.1: (a) sclerotome divides (b) halves join with adjacent halves of next sclerotome (c) junction forms centrum. Figure 9.2: Developing vertebral column showing intersegmental position.

  8. Axial Skeleton Vertebrae • Cartilaginous or bony • From occipital region to tail • Vertebrae types based on centrum structure • Centrum is common feature in all vertebrae

  9. Centrum Structure • Acelous- flat anterior and posterior surface • Mammals • Amphicelous- concavities of anterior and posterior surfaces • Fish, primitive salamanders • Procelous- concanvity on anterior surface • Most reptiles • Opisthocelous- concavity of posterior surface • Most salamanders • Heterocelous- saddle-shaped • Neck of birds and turtles

  10. Figure 9.3: Vertebral types based on articular surface of centra.

  11. Vertebrae Evolution • Transition from crossopterygians to labyrinthodonts • Different types of vertebrae came from primitive, rachitomous labyrinthodont vertebrae • Two pleurocentra and U-shaped hypocentrum • Hypocentrum is lost and pleurocentrum enlarges and gives rise to centrum of modern amniote Figure 9.4: Modifications from labyrinthodont to modern amniote vertebrae. Hypocentrum is diagonal lines. Pleurocentrum is red.

  12. Vertebrae Grouping • Grouped according to body region • Amphibians • First to possess a cervical vertebrae Figure 9.6: Regions of vertebral column Figure 9.5: Single cervical vertebrae of anuran.

  13. Reptile Vertebrae • Atlas as 1st and axis as 2nd cervicals • Turtle: 8 cervicals, 2 sacrals, 10 dorsals, 16-30 caudals • Alligator: 8 cervicals, 11 thoracic, 5 lumbar, 2 sacrals, up to 40 caudals Figure 9.7: atlas and axis cervical vertebrae. Figure 9.8: Dorsal view of sacral vertebrae of vertebrates.

  14. Bird Vertebrae • Possess atlas and axis • 13-14 free cervicals, 4 fused thoracics, fused synsacrum, free caudals, pygostyle Figure 9.9: Pigeon vertebral column.

  15. Synsacrum • Fuses with pelvic bone • Reduction in bone mass Figure 9.11: Synsacrum and pelvic girdle left lateral (a) and ventral (b) views. Figure 9.10: Pigeon skeleton: trunk, tail, and pectoral girdle.

  16. Mammal Vertebrae • most 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

  17. Ribs • Dogfish- develop dorsal ribs • Most teleost- develop ventral ribs • Tetrapods- have dorsal and ventral ribs • Dorsal ribs lost, enlargement of head of proximal ribs • 2 portions articulate with vertebrae • Tuberculum- dorsal head • Capitulum- ventral head Figure 9.12: Rib types - Dorsal and ventral ribs.

  18. Agnathans- no ribs • Amphibians- ribs never reach sternum • Birds- flat processes extending off ribs posteriorly (unicate processes) Figure 9.13: Unicate processes of bird. Figure 9.14: Vertebrae and ribs of alligator.

  19. Sternum • Tetrapod structure • Amphibians- poorly formed • Reptiles- cartilaginous plates • Snakes, legless lizards, turtles have no sternum • Alligator- extends down belly • Ribs fused it sternum • Gastralia Figure 9.15: Ribs and gastralia of alligator.

  20. Birds- unusual, keeled sternum in carinates • Mammals- well developed sternum • Rod shaped • Segments: manubrium, sternebrae, xiphisternum and xiphoid process Figure 9.17: Tetrapod sterna. Figure 9.16: Keeled sternum of bird.

  21. Heterotopic Bone • Develop by endochondral or intramembranous ossification • In areas subject to continual stress • Ex: os cordis, rostral bone, os penis, os clitoridis

  22. 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 9.18: Heterotopic bones (book figure 7.11).

  23. Skull and Visceral Skeleton • Two functionally independent cartilaginous components derived from replacement bone 1. Neurocranium 2. Splanchnocranium Figure 9.19: Placoderm skull; neurocranium in blue; splanchnocranium in yellow.

  24. Neurocranium • Protects brain and anterior part of spinal cord • Sense organ capsules • Cartilaginous brain case is embryonic adaptation • Four ossification centers Figure 9.20: Development of cartilaginous neurocranium.

  25. Neurocranium Ossification Centers • Occiptial Region • Sphenoid Region • Ethmoid Region • Otic Region Figure 9.21: Neurocranium of human skull.

  26. Occipital Region • Basioccipital, 2 exoccipitals, suproccipital • Forms single occipital bone in mammals • Sphenoid Region • Basisphenoid, orbitosphenoid, presphenoid, laterosphenoid • Fuse to form one sphenoid bone in mammals Figure 9.22: Sphenoid bone.

  27. Figure 9.24: Sphenoid bone. Figure 9.23: Human skull (a) cribriform plate (b) crista galli (c) frontal bone (d) sphenoid bone (e) temporal bone (f) sella turcica.

  28. Ethmoid Region • Anterior to sphenoid • Cribriform plate, olfactory foramina, terminals, mesamoid • Fuse to form ethmoid in mammals • Otic Region • Three bones in tetrapods • Prootic • Opisthotic • Epiotic • Unite to form petrosal bone in birds and mammals • Forms temporal in mammals

  29. Figure 9.25: Temporal bone of human skull. Figure 9.26: Multiple nature of temporal bone of mammals.

  30. Figure 9.27: Intramembranous ossification of human skull. Embryonic, cartilaginous neurocranium is black. Neurocranial bones are red. Other is dermal mesenchyme.

  31. Splanchnocranium • Visceral skeleton • Visceral arches • Branchial region Figure 9.28: Splanchnocranium of human. Skeletal derivatives of 2nd through 5th pharyngeal arches.

  32. 1st visceral arch- mandibular • Meckel’s cartilage  malleus • Pteryoquadrate  incus • 2nd visceral arch- hyoid • hyomandibula  columella (stapes) • ceratohyal  styloid process and anterior horn of hyoid • basihyal  body of hyoid Figure 9.29: Caudal end of Meckel’s cartilage and developing middle ear cavity.

  33. Visceral-Cranial Derivatives • Alisphenoid- part of sphenoid • Malleus, incus- 1st arch • Stapes- 2nd arch • Styloid- 2nd arch • Hyoid- mainly basihyal Figure 9.30: Derivatives of the human visceral skeleton (red).

  34. Figure 9.31: Skeletal derivatives of pharyngeal arches.

  35. Dermatocranium • Membrane bone, not replacement bone • Dermal bones of skull • Upper jaw and face, palates, mandible Figure 9.32: Pattern that tetrapod dermatocrania may have evolved.

  36. Dermatocranium (cont.) Figure 9.33: Dog skull showing dermatocranium (pink), chondrocranium (blue), and splanchnocranium (yellow). Figure 9.34: Endochondral bones (red) of mammalian skull.

  37. Dermatocranial Elements • Nasal • Squamosal • Secondary palate- premaxilla, maxilla, jugal • Primary palate- vomer, palatine, pterygoid

  38. Neurocranial Elements • Cribriform • Ethmoid • Otic complex • Temporal bone

  39. Splanchnocranial Elements • Maleus, incus, stapes • Styloid process- hyoid

  40. Visceral Arches of Man • Styloid processes • Body of hyoid • Thyroid • Cricoid

  41. Middle Ear Bones • Hammer (malleus_ • Anvil (incus) • Stirrup (stapes) • Not homologous to weberian ossicles in teleost fish • Modified transverse processes of anteriormost vertebrae in some fishes.

  42. Appendicular Skeleton • Pectoral Girdle • Pelvic Girdle • Appendages • Adaptations for Speed

  43. Pectoral Girdle • 2 sets of elements: cartilage or replacement bone and membrane bone • Replacement bones • Coracoid, scapula, suprascapula • Membrane bones • Clavicle, cleithrum, supracleithrum Figure 9.35: Pectoral girdle phylogenetic lines. Dermal bones are red. Replacement bones are black.

  44. Reduction in number of bones through evolution • 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 fuse to form furcula (wishbone) (a) (b) Figure 9.36: Pectoral girdles of (a) Polypterus and (b) shark.. Dermal bones are red. Replacement bones are black..

  45. Pelvic Girdle • No dermal elements • Three replacement bones • Ilium, ischium, pubis • Triradiate pelvic girdle- alligator and dinosaur Figure 9.37: Left halves of pelvic girdles showing parallel evolution.

  46. Appendages • Single unit in both fore and hind limbs most medial • Two units in fore and hind limb distal area Figure 9.38: Dorsal view of left forelimb or forefin of Devonian tetrapods.

  47. Figure 9.40: Left pectoral fin of Devonian fish [left] and forelimb of early tetrapod [right]. Figure 9.39: Cladogram of lobe-Fin fishes and amphibians.

  48. Small set of bones at wrist and ankle • Pentameristic pattern of phalanges • Reduction in number and position of phalanges Figure 9.41: Evolution of fins to limbs.

  49. Adaptations for Speed • Plantigrade • Flat on the ground • Primates • Digitigrade • Elevated • Carnivores • Unguligrade • Reduction in digits • Two types Figure 9.42: Plantigrade, digitigrade, and unguligrade feet. Ankle bones are black. Metatarsals are grey.

  50. Unguligrade AdaptationReduction in digits • Perissodactyls • Odd toed • Mesaxanic foot • Weight on enlarged middle digit • Ex: horse • Artidodactyls • Even toed • Paraxonic foot • Weight equally distributed on 3rd and 4th digits • Ex: camel Figure 9.43: Unguligrade adaptations in horse and camel. Bones lost are white.

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