Term
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Definition
- Radiating dermal fin rays (skeletal support for fin membranes): (1) Ceratotrichia: rods of keratin (found in elasmobranchs) (2) Lepidotrichia: rays of bone or cartilage (found in bony fishes) - At the body wall, the fins are attached to rods cartilage or bone called pterygiophores. |
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Term
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Definition
- Median (dorsal and anal): stabilizers; prevents side-to-side rocking movements - Caudal (tail): propulsion; four types: - Tetrapod Median and Caudal fins: not homologous with fish fins, but secondarily evolved. Skeletal supports are fibrous or lacking. Found in some salamanders, tadpoles, ichthyosaurs, whales, manatees. - Paired Pectoral and Pelvic Fins |
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Term
Paired Pectoral and Pelvic Fins |
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Definition
® Probably arose from lateral folds of skin (fin-fold theory: see fig. 9.5) ® Primitively: immobile; function as stabilizers ® Modern: movable; function in steering ® Homologous with tetrapod limbs |
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Term
Caudal (tail): propulsion; four types: |
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Definition
(1) Heterocercal (fig. 8.20a): Asymmetrical: notochord turns upward into the dorsal portion; probably the primitive condition. Found in placoderms, modern sharks, and primitive bony fishes (e.g., sturgeons). (2) Hypocercal: Rare; asymmetrical with the notochord turning downward into the ventral portion. Occurs in some extinct agnathans. (3) Diphycercal (fig. 8.20b): Symmetrical; vertebral column extends straight back to the tip of the body with very little upbending at the end. Found in lampreys, hagfishes, lungfishes, and chimaeras. (4) Homocercal (fig. 8.20c): Externally symmetrical, internally asymmetrical. The backbone strongly upwards at its tip. |
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Term
Pectoral Girdle General History: |
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Definition
- originated before the pelvic girdle and is more complex - Elements derived from either ancestral armor (dermal bone) or cartilage (Overview: fig. 9.18) |
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Term
Pectoral Girdle Taxonomic Comparisons: Placoderms |
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Definition
(primitive condition, see fig. 9.8b) ® Fin connects to plates of dermal bone ® Small interconnecting pieces of cartilage |
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Term
Pectoral Girdle Taxonomic Comparisons: Chondrichthyes |
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Definition
(see fig. 9.9): cartilage ® Lost bone; elaborated cartilage ® Primitively, separate left and right elements ® Later: left and right elements fused, forming the U-shaped scapulocorocoid |
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Term
Pectoral Girdle Taxonomic Comparisons: Bony fishes |
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Definition
(fig. 9.12): dermal bone plus endochondral bone ® Dermal bone (retaining primitive condition)
- Cleithrum: forms most of the girdle - Post-temporals: join the girdle to the skull - Clavicle: small bone that is lost in most modern teleosts ® Endochondral bone: small scapulocorocoid |
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Term
| Pectoral Girdle Taxonomic Comparisons: Amphibians |
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Definition
(trend: REDUCE DERMAL BONE, INCREASE ENDOCHONDRAL BONE)
->Primitive (see fig. 9.15b; compare to 9.15a):
- Retains fish dermal bones except post-temporals
- Endochondral: scapulocoroid (dorsal scapula and a ventral corocoid)
->Modern:
- Most dermal bones lost (anurans retain the clavicle)
- Endochondral: large scapulocorocoid
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Term
| Pectoral Girdle Taxonomic Comparisons: Reptiles |
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Definition
(trend: REDUCE DERMAL BONE, INCREASE ENDOCHONDRAL BONE)
-> Primitive (and monotreme mammals):
- Dermal: Retain clavicle and, sometimes, cleithrum
- Endochondral: Large scapula and corocoids
-> Modern:
- Dermal: cleithrum lost; clavicles sometimes lost
- Endochondral: large scapula and corocoid
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Term
| Pectoral Girdle Taxonomic Comparisons: Modern Birds |
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Definition
(SIMILAR TO MODERN REPTILES)
-> Dermal: clavicles (only dermal bone) fuse forming the furculum (wishbone)
-> Endochondral: Large scapula and corocoid
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Term
| Pectoral Girdle Taxonomic Comparisons: Mammals |
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Definition
(MOSTLY ENDOCHONDRAL BONE)
-> Dermal: Only the clavicle is retained
-> Endochondral: Large scapula with two processes
- acromion process: articulates with the clavicle
- corocoid process: formed from corocoid bone
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Term
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Definition
ORIGINATES FROM PTERYGIOPHORES (CARTILAGE OR ENDOCHONDRAL BONE)
-> Placoderms: a single bone if any
-> Chondrichthyans (fig. 9.10): left and right cartilaginous elements fused across the midline forming a puboischiac bar
-> Bony fishes: paired bones that may overlap or articulate with each other
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Term
| Pelvic Girdles: Tetrapods |
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Definition
ENLARGED COMPARED TO FISHES
-> Three endochondral bones contribute
- a dorsal ilium, which articulates with the sacral vertebrae
- an anterior pubis
- a posterior ischium
-> These bones may fuse on each side, forming the innominate bone
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Term
| Tetrapod limbs and the invasion of land |
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Definition
- Tetrapods evolved in humid areas with abundant water
- Early tetrapods “walked” on the bottom of their aquatic habitats with their lobe-shaped fins; some occasionally crawled onto the damp shore to escape enemies or to find food.
- The pattern of bones in the limbs of tetrapods is similar across taxa and resembles that of the pectoral girdle and fin of lobe-finned fishes (fig. 9.15a, b)
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Term
| Limb posture: Amphibians and reptiles |
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Definition
- Short limbs splayed to the side of the body; movement is energetically expensive (see fig.’s 9.31, 9.33a, and 9.34).
- Undulations of the spine (similar to that seen in fishes) twist the girdles, helping to advance the limbs (see fig. 9.27)
- Some modifications:
-> Anurans: specialized for hopping, with enlarged hind limbs and pelvic girdles
-> Dinosaurs: tended toward bipedalism. Hind limbs were rotated to a position directly beneath the body where they can support much of the weight of the body ( fig. 9.33b)
-> Therapsid reptiles (mammalian ancestors) had similar limb rotations
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Term
| Limb posture: Birds and mammals |
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Definition
- Limbs aligned directly under body (like bipedal dinosaurs), efficiently supporting the body weight
- Elongation of some bones (e.g., digits) can increase stride length (more later)
- Specializations: e.g., wings, cetacean fins
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Term
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Definition
Upper Arm (Brachium)
Humerus
Forearm (Antebrachium)
Radius and Ulna
Wrist (Carpus)
Carpals*
Palm (Metacarpus)
Metacarpals*
Digits
Phalanges*
*Bones of the manus
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Term
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Definition
- Primitive: Short, very little shaft, expanded at both ends
- Modification: More distinct shaft (occasionally, other modifications; see fig. 9.55)
- All have:
-> Proximal crests for attachment of pectoral and deltoid muscles
-> Condyles: distal expansions for attachment of forearm muscles
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Term
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Definition
- Articulates with the carpals near the thumb
- Bears most of the force transmitted from the wrist; consequently, it is large in diameter.
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Term
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Definition
- Articulates with the carpals opposite the thumb
- Usually longer (and narrower) than the radius
- Modifications:
-> Birds and mammals: extends above the elbow forming the olecranon (“funny bone”)
-> May fuse with the radius, or be vestigial or lost (e.g., frogs and bats)
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Term
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Definition
- Carpals
- Metacarpals
- Phalanges |
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Term
| Carpals (general pattern) |
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Definition
-> Proximal row: Radiale, Intermedium, Ulnare; Pisiform in mammals
-> Middle row: Centralia. Trend = decrease in number of centralia (through fusions, losses, and displacement)
-> Distal row: Distal carpals (articulate with metacarpals)
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Term
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Definition
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Term
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Definition
-> Early tetrapods: 6-8 digits (fig. 9.23b)
-> Modern amphibians, all reptiles and mammals: typically have 5 digits (Pentadactyl limb established in Devonian -- about 350 mya)
-> Birds
- Number of bones reduced
- Distal carpals fuse with the metacarpals forming a carpometacarpus
- Note: Compare bird wing bones to those of bats and pterodactyls (fig. 9.42)
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Term
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Definition
Thigh
Femur
Shank (Crus)
Tibia and Fibula
Ankle (tarsus)
Tarsals*
Instep (metatarsus)
Metatarsals*
Digits
Phalanges*
*Bones of the pes
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Term
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Definition
- Proximally: A head that articulates with the pelvis at the (“acetabulum”)
- Distally: A double-head that articulates with the tibia and fibula
- Processes on the shaft for muscle attachment: trochanters and crests
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Term
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Definition
- Distal end articulates with the inner side of the tarsus
- Main supporting element for the leg so is large in diameter
- Major ridge for muscle attachment: cnemial crest
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Term
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Definition
- Distal end articulates with the outside of the tarsus
- Usually thinner than the tibia
- Reduced in some taxa
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Term
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Definition
- Sesamoid bone found in mammals
- Insertion point for the main extensor tendon (similar function to the olecranon)
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Term
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Definition
| Tarsus, Metatarsals, and Digits |
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Term
| Tarsus (Amphibians and Reptiles) |
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Definition
(ankle) (Fig. 9.25)
-> Amphibians (Primitive condition):
- Proximal row (tibiale, intermedium, fibulare)]
- Central row (centralia)
- Distal row (distal tarsals)
-> Reptiles: Modification of the proximal row
- Fibulare is enlarged and is called the calcaneum
- Other proximal tarsals fuse, forming the astragulus (proving firm support for the tibia) |
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Term
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Definition
| -> Similar to corresponding manus bones |
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Term
| - Limb posture: Mammals - Plantigrade: |
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Definition
(Fig. 9.25g)
o most primitive posture
o all bones of the pes in contact with the substrate
o characteristic of primates
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Term
| - Limb posture: Mammals - Digitigrade |
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Definition
(Fig. 9.25.f)
o Digits form arch over foot
o Characteristic of dogs, cats, and their relatives
o Adaptation for speed
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Term
| - Limb posture: Mammals - Unguligrade |
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Definition
(Fig. 9.24e)
o Body weight is supported by tip of digit(s)
o Characteristic of ungulates (horses, cows, deer, antelope)
o Adaptation for extreme speed
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Term
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Definition
(fig. 8.1) (agnathans, placoderms, primitive extant fishes)
- Persistant notochord forming a rod
- Neural arches (dorsal): surrounds nerve cord
- Hemal arches (ventral): surrounds blood vessels
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Term
| Axial Skeleton - Modifications |
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Definition
- Bone surrounds or completely replaces the notochord (= centrum of vertebra)
- Two types of centra: (fig. 8.3)
→ Aspidospondyl (“shield” + “spine”): made of separate elements (amphibians, reptiles)
→ Holospondyl: (“whole” + spine”): made of fused elements (birds, mammals; modern fishes)
- Projections: (fig. 8.6, 8.7)
→ Neural spine: extends dorsally from neural arch
→ Hemal arch: same as on primitive vertebra; not always present
→ Transverse process: Any lateral process; called diapophyses if supporting ribs
→ Zygopophysis: extends anteriorally and posteriorally from neural spine; functions to hold adjacent vertebrae together; not always present
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Term
| Types of articulation between adjacent centra (based on shapes of centra); Fig. 8.4 |
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Definition
Acoelus (“not” + “hollow”) Amphicoelus (“both” + “hollow”) Procoelus (“front” + “hollow”) or Opisthoceolus (“behind” + “hollow”) Heterocoelus (“different” + “hollow”) |
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Term
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Definition
→ Both anterior and posterior surfaces are flat
→ Distributes pressure evenly over surface, so withstands compression
→ Often separated by an interveterbral disk (derived from notochord)
→ Ex., mammals
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Term
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Definition
→ Both anterior and posterior ends are concave
→ Allows some movement in all directions
→ Ex., fishes
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Term
| Procoelus / Opisthoceolus |
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Definition
→ Either anterior end concave and posterior end convex, or vice versa
→ Forms a ball and socket joint between adjacent vertebra; allows extensive vertical movement without twisting the nerve cord
→ Ex., amphibians and reptiles |
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Term
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Definition
→ Centrum is saddle-shaped
→ Allows vertical and lateral flexion but prevents rotation
→ Ex., necks of birds and side-necked turtles
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Term
| Types of articulation between adjacent neural arches |
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Definition
- Cartilaginous fishes (fig. 8.15d): space between neural arches is filled with interneural arches (all made of cartilage)
- Bony fishes (fig. 8.17a,b): neural spines are connected by a firm intervertebral ligament
- Tetrapods: neural spines are connected by zygopophyses
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Term
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Definition
| little regional differentiation |
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Term
| Spinal columns: - Tetrapods |
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Definition
| stresses of gravity, need for mobility and strength led to specializations |
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Term
| Spinal columns: → Labyrinthodont amphibians (fig. 8.26c): |
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Definition
| Aspidospondyl vertebrae with an intercentrum and paired pleurocentra; little regional differentiation |
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Term
| Spinal columns: → Modern amphibians |
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Definition
- Holospondyl vertebrae
- Regional specialization
--Cervical: “neck” vertebrae (1 or 2): no projections; articulates with skull occipital process
--Trunk: anterior to pelvis: salamanders/caecilians – articulates with ribs; frogs – no ribs, but large transverse processes
--Sacral: attaches to pelvis; enlarged transverse processes
--Caudal: “tail”; no projections, usually have hemal arches; frogs – fused, forming the urostyle
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Term
| Spinal columns: → Primitive reptiles (fig. 8.27a) |
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Definition
- Aspidospondyl
- First cervical vertebra: atlas, no projections
- Second cervical vertebra: axis, large neural arch
- Otherwise, similar to Labyrinthodont
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Term
| Spinal columns: → Modern reptiles (fig. 8.30) |
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Definition
- Holospondyl
- Cervical: Atlas and axis plus additional cervical vertebrae (longer necks)
- Thoracic: upper “back”, attached to ribs
- Lumbar: lower “back”, no ribs
- Sacral: 2 or more, enlarged transverse processes
- Caudal vertebrae similar to amphibians
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Term
| Spinal columns: → Modern birds (fig. 8.32) |
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Definition
- Many heterocoelus cervical vertebrae
- Synsacrum: fusion of pelvis with thoracic, lumbar, sacral, and caudal vertebrae
- Pygostyle (“pyg” = small; “style” = stalk): fused caudal vertebrae; support tail feathers
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Term
| Spinal columns: → Mammals |
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Definition
- Cervical: Most have 7 (atlas and axis plus 5 more)
- Trunk: About 20 (thoracic and lumbar)
- Sacral: 3+ fused vertebrae: forms the sacrum
- Caudal: Varying numbers
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Term
| Muscles and ligaments support the vertebral column (see fig. 8.34) |
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Definition
- The arch-shape helps to support the body’s weight
- Ligaments help the cervical vertebrae to remain arched
- The sternum and abdominal muscles (i.e., rectus abdominis) help keep the thoracic and lumbar vertebrae arched
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Term
| Cranio-Vertebral Connections: - Fishes |
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Definition
| Single occipital condyle on skull, no modifications to vertebra; little head movement |
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Term
| Cranio-Vertebral Connections: - Early amphibians |
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Definition
| Single occipital condyle on skull, no modifications to vertebra; little head movement |
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Term
| Cranio-Vertebral Connections: - Later amphibians |
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Definition
→ 2 occipital condyles
→ Atlas (first vertebra) modified with no processes and concave faces that fit into the occipital condyles like a ball-and-socket joint
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Term
| Cranio-Vertebral Connections: - Reptiles and birds |
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Definition
→ 1 occipital condyle
→ In addition to atlas, axis (second vertebra) is enlarged and forms a joint with the atlas
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Term
| Cranio-Vertebral Connections: - Mammals |
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Definition
→ 2 occipital condyles
→ Atlas (fig. 8.27g): small centrum, no dorsal/ventral processes, wing-like transverse processes;
→ Axis (fig. 8.27f): Large centrum, blade-like neural spine
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Term
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Definition
| Develops from endochondral bone, from sclerotomes |
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Term
| Ribs - Taxonomic diversity |
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Definition
→ Fishes
-No ribs: agnathans, placoderms, ratfish
-2 pairs per vertebrae (fig. 8.6): most except ray-finned fishes
- Dorsal: in horizontal septum
- Ventral: around coelom
-Ventral ribs only: ray-finned bony fishes
→ Tetrapods (fig. 8.7): Dorsal ribs only; Ribs are bicipital (“two heads”)
-Tuberculum: dorsal head, attaches to diapophysis
-Capitulum: ventral head, attaches to side of centrum
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Term
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Definition
| (tetrapods only): Attachment surface for muscles that move the forelimb; may attach to ribs |
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Term
| Primitive amphibians sternum |
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Definition
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Term
| Modern amphibians sternum |
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Definition
-Caecilians: none (but well-developed ribs)
-Frogs: sternum present (but no ribs) (fig. 8.8a)
-Salamanders: sternum present (tiny ribs; do not attach to sternum) (fig. 8.8a)
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Term
| General info about sterna/ribs of amniotes (reptiles, birds, mammals) |
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Definition
-Well-developed ribs and sterna
-Ribs in two pieces: ossified dorsally, cartilaginous ventrally (“sternal rib”)
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Term
| Special info about reptile sterna/ribs |
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Definition
-Squamates: single-headed ribs
-Snakes: no sternum
-Turtles: no sternum; ribs fused to carapace
-Crocodilians (and some others): have abdominal “ribs” called Gastralia; these are dermal bone and so are not true ribs
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Term
| Special info about sterna/ribs of modern birds |
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Definition
-Sternum is large and keeled (for attachment of huge flight muscles)
-Ribs are thin, flattened and light-weight
-Adjacent ribs are attached together with uncinate processes (Figure 8.8d)
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Term
| Special info about sterna/ribs of mammals |
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Definition
-9 (some whales) to 24 (some sloths) pairs
-First 10 ribs attach to sternum; any additional ribs are called floating ribs
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Term
| Types of Skeletal Tissues |
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Definition
(1) Loose (or areolar) connective tissue (2) Compact (or fibrous) connective tissue (3) Cartilage (4) Bone |
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Term
| Loose (or areolar) connective tissue |
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Definition
- Gelatinous protein ground substance
- Scattered fibers:
->Reticular fibers: small and branching
->Collagenous fibers: long, slender, white fibers that are nonelastic. They are formed by precursor cells called fibroblasts.
->May contain capillaries or fat (“adipose”) cells
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Term
| Compact (or fibrous) connective tissue |
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Definition
- Fibers are densely packed:
-> Reticular fibers
-> Collagenous fibers
-> Elastic fibers: coarse and yellow
- Examples:
-> Tendons: attach muscle to either cartilage or bone
-> Ligaments: connect skeletal elements together
-> Fasciae: sheets connecting various elements
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Term
|
Definition
- Matrix is a gel-like glycoprotein called chondromucin
- Cells (“chondrocytes”) dispersed in the matrix in spaces called lacunae
- Various fibers are present (see below)
- Generally no nerves or blood vessels
- The surface is a layer of closely packed cells that divide and give rise to new cells
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Term
| Development of skeletal tissues from precursor cells: |
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Definition
Mesenchyme -> Scleroblast -> Osteoblast -> Osteocyte (bone + cell)
Mesenchyme -> Scleroblast -> Chondroblast -> Chrondrocyte (cartilage + cell)
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Term
| Endochondral (or replacement) bone |
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Definition
The skeletal structure is first formed in cartilage and the cartilage is gradually replaced by bone. (Fig.’s Fig. 5.24, 5.21). -> Cartilage begins to degenerate in the center of the bone -> Blood vessels penetrate the central cartilage; osteoblasts in the blood produce bone cells (“osteocytes”) which secrete calcium phosphate, replacing the cartilage. This process is called ossification.
-> Growth is from the center toward the ends of the bones (“epiphyses”), with both the cartilage and (later) the bone moving growing outward. The shaft of the bone is called the diaphysis.
-> A marrow cavity forms in the center as endochondral bone is resorbed. |
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Term
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Definition
-> Bone forms from mesenchyme without a cartilaginous precursor
-> Growth is by application of new bone to the surface of the old bone
-> Types:
- Dermal, Sesamoid, and Periosteal bone |
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Term
| Fine Structure of Endochondral Bone (Fig. 5.23; note: the figure is not labeled) |
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Definition
- A matrix of fibers enclosed in a hard, opaque calcified material (primarily calcium phosphate)
- The matrix is secreted by osteocytes which are dispersed in spaces called lacunae
- In early development, the osteocytes develop projections called canaliculi. The protoplasmic processes retract, but the canaliculi are persistent.
- Blood vessels penetrate via Haversian canals and nutrients are transmitted via the canaliculi. |
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Term
| Phylogeny of the bony skeleton |
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Definition
- The completely cartilaginous skeletons of extant agnathans and chondrichthyans is not the retention of a primitive trait (early vertebrates had bone, at least around their skulls)
- Instead, these skeletons are secondarily reduced, retaining the embryonic condition (an example of paedomorphosis)
- The loss of bone was probably an adaptation to increase buoyancy because these fishes lack a swim bladder. |
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Term
|
Definition
- Types of cartilage:
-> Hyaline (fig. 5.20a): translucent and smooth with few fibers; caps the bones at movable joints where it is important for lubrication
-> Fibrous (fig. 5.20b): A heavy meshwork of collagen fibers; cushion-like and tough; separates the vertebrae of the lower back
-> Elastic (fig. 5.20c): many elastic fibers; flexible and resilient; found in the external ear
-> Calcified: deposits of calcium salts make it hard and firm; common in elasmobranch skeletons |
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Term
| Tarsus (Birds and Mammals) |
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Definition
(ankle) (Fig. 9.25)
-> Birds: highly modified by fusions
- No free tarsal bones
- Proximal tarsals fuse with tibia, forming the tibiotarsus
- Distal tarsals fuse with the metatarsals forming the tarsometatarsus
-> Mammals: variation on the reptile pattern
- Calcaneum developes a “heel” projection. Calf muscles attach to the heel via the Achilles tendon
- Astragulus develops a head that articulates with the tibia, forming a hinge joint that resists twisting. |
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Term
|
Definition
- Dermal bone (derived from mesoderm in the dermis): includes many outer bones of the skull and pectoral girdle; integumental bone (e.g., fish scales)
- Sesamoid bone: forms within tendons; includes the patella of the knee and one of the wrist bones called the pisiform bone
- Periosteal bone forms around endochondral bone, such as around the diaphysis of long bones. If the bone forms around cartilage it is called Perichondrial bone. |
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Term
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Definition
In many vertebrates, the Haversian canals and their associated canaliculi and osteoblasts are arranged in a Haversian system (or osteon) that resembles a tree trunk. Dermal bone does not have this appearance. In many non-mammal vertebrates, it is common to see bone tissue that is acellular, with new bone being produced seasonally, forming growth rings.
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Term
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Definition
The external layer of bone around the diaphysis of vertebrate long bones is Periosteum (a type of dermal bone). This layer is densely packed with cells and may furnish new osteocytes to the underlying layers. |
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Term
| Differences of ecto/endothermic endochondral (or replacement) bone |
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Definition
-> In ectothermic vertebrates (fishes, amphibians, and reptiles), the epiphyses remain cartilaginous. Growth is indeterminate, continuing throughout their life (although slowing in later years)
-> In endotherms (birds and mammals), secondary centers of ossification develop from the epiphyses, completely ossifying the articular surfaces. Growth is determinate, ceasing at or near maturity when a band of cartilage near the epiphysis becomes ossified. |
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