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Comparative Anatomy Bone Note Set 7 Chapters 7, 8, & 9
Bone Legacy n Exoskeleton or dermal skeleton Dermal bony armor of ostracoderms n Bony scales in ancient fish n n Cranial dermal armor arose from neural crest cells
n Endoskeleton Internal to skin n Where once exoskeleton n n Ex: clavicle, nasal, frontal, and parietal bone n Other endoskeletal elements were never part of the dermal skeleton n Ex: scapula, vertebrae, ribs, sternum, brain case, and extremity bones
Bone Evidence All bone develops from mesenchyme n Neural crest cells n Membrane bone- arises from mesenchyme without passing through cartilaginous intermediate n n n exoskeleton Replacement bone- arises from existing cartilage n endoskeleton
Endoskeletal Tissues n Visceral Skeleton n Jaw cartilages and ear ossicles n n n Weberian ossicles of fish (ear ossicles) Derived from transverse processes of anterior most vertebrae Somatic Skeleton Remaining internal bones developing from mesoderm proper n Somite and scleratome n Axial Skeleton n Appendicular Skeleton n
Vertebrae Development Arise from sclerotome cells of somites Morphogenesis n n n n 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 n Site of rib attachment
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.
Axial Skeleton Vertebrae Cartilaginous or bony From occipital region to tail Vertebrae types based on centrum structure n n Centrum is common feature in all vertebrae
Centrum Structure Acelous- flat anterior and posterior surface n n Mammals Amphicelous- concavities of anterior and posterior surfaces n n Fish, primitive salamanders Procelous- concanvity on anterior surface n n Most reptiles Opisthocelous- concavity of posterior surface n n Most salamanders Heterocelous- saddle-shaped n n Neck of birds and turtles
Figure 9. 3: Vertebral types based on articular surface of centra.
Vertebrae Evolution Transition from crossopterygians to labyrinthodonts Different types of vertebrae came from primitive, rachitomous labyrinthodont vertebrae n n 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.
Vertebrae Grouping Grouped according to body region Amphibians Figure 9. 5: Single n n n cervical vertebrae of First to possess a cervical vertebrae anuran. Figure 9. 6: Regions of vertebral column
Reptile Vertebrae n n n Atlas as 1 st and axis as 2 nd 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.
Bird Vertebrae n n Possess atlas and axis 13 -14 free cervicals, 4 fused thoracics, fused synsacrum, free caudals, pygostyle Figure 9. 9: Pigeon vertebral column.
n Synsacrum Fuses with pelvic bone n Reduction in bone mass n Figure 9. 10: Pigeon skeleton: trunk, tail, and pectoral girdle. Figure 9. 11: Synsacrum and pelvic girdle left lateral (a) and ventral (b) views.
Mammal Vertebrae most have 7 cervicals n 12 thoracic and 5 lumbar compose dorsal vertebrae n ancestral mammals possessed ~ 27 presacrals n sacrum 2 -5 fused vertebrae (ankylosed) n caudals are variable n n primates have 2 -5 fused into coccyx
Ribs Dogfish- develop dorsal ribs Most teleost- develop ventral ribs Tetrapods- have dorsal and ventral ribs n n n Dorsal ribs lost, enlargement of head of proximal ribs 2 portions articulate with vertebrae n n Tuberculum- dorsal head Capitulum- ventral head Figure 9. 12: Rib types - Dorsal and ventral ribs.
n n n 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.
Sternum n n n Tetrapod structure Amphibians- poorly formed Reptiles- cartilaginous plates n n Snakes, legless lizards, turtles have no sternum Alligator- extends down belly n n Ribs fused it sternum Gastralia Figure 9. 15: Ribs and gastralia of alligator.
n n Birds- unusual, keeled sternum in carinates Mammals- well developed sternum Rod shaped n Segments: manubrium, sternebrae, Figure xiphisternum and xiphoid process 9. 17: Tetrapod sterna. Figure 9. 16: Keeled sternum of bird. n
Heterotopic Bone n n n Develop by endochondral or intramembranous ossification In areas subject to continual stress Ex: os cordis, rostral bone, os penis, os clitoridis
Os cordis- interventricular septum in deer heart n Rostral bone- snout of pig n Os penis (baculum)- embedded in penis of lower primates n Os clitoridis- embedded in clitoris of otters n Others include falciform, sesamoid, patella, pisiform n Figure 9. 18: Heterotopic bones (book figure 7. 11).
Skull and Visceral Skeleton n Two functionally independent cartilaginous components derived from replacement bone 1. Neurocranium 2. Splanchnocranium Figure 9. 19: Placoderm skull; neurocranium in blue; splanchnocranium in yellow.
Neurocranium n n 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.
Neurocranium Ossification Centers Occiptial Region n Sphenoid Region n Ethmoid Region n Otic Region n Figure 9. 21: Neurocranium of human skull.
n Occipital Region Basioccipital, 2 exoccipitals, suproccipital n Forms single occipital bone in mammals n n Sphenoid Region Basisphenoid, orbitosphenoid, presphenoid, laterosphenoid n Fuse to form one sphenoid bone in mammals n Figure 9. 22: 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. Figure 9. 24: Sphenoid bone.
n Ethmoid Region Anterior to sphenoid n Cribriform plate, olfactory foramina, terminals, mesamoid n Fuse to form ethmoid in mammals n n Otic Region n Three bones in tetrapods n Prootic n Opisthotic n Epiotic n Unite to form petrosal bone in birds and mammals n Forms temporal in mammals
Figure 9. 25: Temporal bone of human skull. Figure 9. 26: Multiple nature of temporal bone of mammals.
Figure 9. 27: Intramembranous ossification of human skull. Embryonic, cartilaginous neurocranium is black. Neurocranial bones are red. Other is dermal mesenchyme.
Splanchnocranium n n n Visceral skeleton Visceral arches Branchial region Figure 9. 28: Splanchnocranium of human. Skeletal derivatives of 2 nd through 5 th pharyngeal arches.
n 1 st visceral arch- mandibular Meckel’s cartilage malleus n Pteryoquadrate incus n n 2 nd visceral arch- hyoid hyomandibula columella (stapes) n ceratohyal styloid process and anterior horn of hyoid n basihyal body of hyoid n Figure 9. 29: Caudal end of Meckel’s cartilage and developing middle ear cavity.
Visceral-Cranial Derivatives Alisphenoid- part of sphenoid n Malleus, incus- 1 st arch n Stapes- 2 nd arch n Styloid- 2 nd arch n Hyoid- mainly basihyal n Figure 9. 30: Derivatives of the human visceral skeleton (red).
Figure 9. 31: Skeletal derivatives of pharyngeal arches.
Dermatocranium Membrane bone, not replacement bone n Dermal bones of skull n Upper jaw and face, palates, mandible n Figure 9. 32: Pattern that tetrapod dermatocrania may have evolved.
Dermatocranium (cont. ) Figure 9. 33: Dog skull showing dermatocranium (pink), chondrocranium (blue), and splanchnocranium (yellow). Figure 9. 34: Endochondral bones (red) of mammalian skull.
Dermatocranial Elements Nasal n Squamosal n Secondary palate- premaxilla, jugal n Primary palate- vomer, palatine, pterygoid n
Neurocranial Elements Cribriform n Ethmoid n Otic complex n Temporal bone n
Splanchnocranial Elements Maleus, incus, stapes n Styloid process- hyoid n
Visceral Arches of Man Styloid processes n Body of hyoid n Thyroid n Cricoid n
Middle Ear Bones Hammer (malleus_ n Anvil (incus) n Stirrup (stapes) n n Not homologous to weberian ossicles in teleost fish n Modified transverse processes of anteriormost vertebrae in some fishes.
Appendicular Skeleton Pectoral Girdle n Pelvic Girdle n Appendages n Adaptations for Speed n
Pectoral Girdle n 2 sets of elements: cartilage or replacement bone and membrane bone n Replacement bones n n Coracoid, scapula, suprascapula Membrane bones n Clavicle, cleithrum, supracleithrum Figure 9. 35: Pectoral girdle phylogenetic lines. Dermal bones are red. Replacement bones are black.
Reduction in number of bones through evolution n Shark- only cartilagenous components Alligator- retains only replacement bone elements, no dermal bone Mammals n n n 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. .
Pelvic Girdle n n No dermal elements Three replacement bones n n Ilium, ischium, pubis Triradiate pelvic girdlealligator and dinosaur Figure 9. 37: Left halves of pelvic girdles showing parallel evolution.
Appendages n n 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.
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.
n n n 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.
Adaptations for Speed n Plantigrade Flat on the ground n Primates n n Digitigrade Elevated n Carnivores n n Unguligrade Reduction in digits n Two types n Figure 9. 42: Plantigrade, digitigrade, and unguligrade feet. Ankle bones are black. Metatarsals are grey.
Unguligrade Adaptation Reduction in digits n Perissodactyls n n n Odd toed Mesaxanic foot Weight on enlarged middle digit n n Ex: horse Artidodactyls n n n Even toed Paraxonic foot Weight equally distributed on 3 rd and 4 th digits n Ex: camel Figure 9. 43: Unguligrade adaptations in horse and camel. Bones lost are white.
n Locomotion Without Limbs Serpentine Lateral undulation n Wave motion n Minimum 3 contact points n n Rectilinear (a) Straight line n Scutes on belly lift n Costocutaneous muscles move the skin n (b) (c) Figure 9. 44: Serpentine locomotion (a) and rectilinear locomotion (b & c).
Locomotion Without Limbs (cont. ) n Sidewinding Minimum 2 contact points n Adaptation in sandy habitats n n Concertina Minimum 2 contact points n Allows snake to move up (a) (b) gutter Figure 9. 45: Sidewinding locomotion (a) and n concertina locomotion (b).
Literature Cited Figure 9. 1 - http: //www. brown. edu/Courses/BI 0032/bone/axial 2. htm Figure 9. 2, 9. 3, 9. 4, 9. 5, 9. 8, 9. 9, 9. 10, 9. 11, 9. 12, 9. 14, 9. 16, 9. 17, 9. 18, 9. 20, 9. 21, 9. 25, 9. 26, 9. 27, 9. 28, 9. 29, 9. 30, 9. 31, 9. 32, 9. 34, 9. 35, 9. 36, 9. 37, 9. 40, 9. 42 & 9. 43 - Kent, George C. and Robert K. Carr. Comparative Anatomy of the Vertebrates. 9 th ed. Mc. Graw-Hill, 2001. Figure 9. 6 - http: //www. agrabilityproject. org/assistivetech/tips/tractorseat. cfm Figure 9. 7 - http: //www. spineuniverse. com/displayarticle. php/article 2245. html Figure 9. 13 - http: //bioweb. uwlax. edu/zoolab/Table_of_Contents/Lab 9 b/Bird_Skeleton_1 c/bird_skeleton_1 c. htm Figure 9. 15 - http: //www. auburn. edu/academic/classes/zy/0301/Topic 8. html Figure 9. 19 -Kardong, K. Vertebrates: Comparative Anatomy, Function, Evolution. Mc. Graw Hill, 2002. Figure 9. 22 - http: //www. mlaphil. org/chronicle/20 n 3/fall 2002. htm Figure 9. 23 - http: //www. staneksoftware. com/anatomy_bowl_content/Sk. Skull 1. htm Figure 9. 24 - http: //www. upstate. edu/cdb/grossanat/hnsklatsb. shtml Figure 9. 33 - Kardong, K. Vertebrates: Comparative Anatomy, Function, Evolution. Mc. Graw Hill, 2002. Figure 9. 38 - http: //cas. bellarmine. edu/tietjen/images/subphylum_vertefish. htm Figure 9. 39 - http: //bss. sfsu. edu/holzman/courses/Fall%2003%20 project/CAtigersalamander. htm Figure 9. 41 - http: //pharyngula. org/~pzmyers/Myers. Lab/teaching/Bi 104/l 02/fins. html Figure 9. 44 - http: //www. worldwidesnakes. com/ri-reptile-basic-anatomy-locomotion. php Figure 9. 45 (a)- http: //folio. photosource. com/1120 Figure 9. 45 (b)- http: //voronoi. sbp. ri. cmu. edu/research/rsch_locomotion. html