Presentation on theme: "Mrs. Ofelia Solano Saludar"— Presentation transcript:
1 Mrs. Ofelia Solano Saludar SKELETAL SYSTEM: SKULL & VISCERAL SKELETONMrs. Ofelia Solano SaludarDepartment of Natural Sciences University of St. La Salle Bacolod City
2 The vertebrate skull consists of: Neurocranium (also called endocranium, chondrocranium or primary braincase)Dermatocranium (membrane or dermal bones)Splanchnocranium (visceral skeleton)
3 1. CHONDROCRANIUM or NEUROCRANIUM Cartilaginous stage protects the brainBegins as a pair of parachordal cartilages alongside the notochord (derived from sclerotome), and the prechordal cartilages or trabeculae cranii (derived from neural crests) anterior to these.
4 Cartilages derived from neural crest also appears in the: olfactory capsules partially surrounding the nasal epithelium,otic capsule surrounding the inner ear,orbital/ optic capsules around the eyes
5 Completion of floor, walls, & roof: Parachordals join the notochord and expand to form the basal plate, floor of hindbrain, occipital condyles (1-2), and foramen magnumEthmoid plate – prechordals fuse with olfactory capsules; optic capsules remain independent
6 Basal plate - fuses with otic capsules Development of cartilaginous walls (sides of braincase) and a cartilaginous roof over the brain in cartilaginous fishesForamina remain for nerves & blood vesselsHypophyseal fenestra remains for pituitary gland and carotid arteries
7 Cartilaginous fishes - retain a cartilaginous neurocranium throughout life; completes skull by forming a cartilaginous roof (tectum) over neurocranium
8 Bony fishes, lungfishes, & most ganoids - retain highly cartilaginous neurocranium that is covered by membrane boneCyclostomes- the cartilaginous components of the embryonic neurocranium remain in adults as independent cartilages
9 Reptiles: Embryonic Development of Lizard Chondrocranium: Parachordal and trabecular cartilages grow up around brain and sense organs
10 2. DERMATOCRANIUMConsists of membrane bones that encase the chondrocranium and jaws.Formed a complete roof for the skull of extinct tetrapods, but became reduced in number through loss.Vacuities also tend to arise in the posterior part of the roof, and these temporal fossae are of importance in the evolution of the various amniotes.
12 Temporal fossae (plus mammalian zygomatic arch) provide space and surfaces in advantageous positions for accommodating the large powerful muscles (adductor, masseter, temporalis) that operate the lower jaw of amniotes.
13 Differentiation of synapsid adductor mandibulae into temporalis, superficial masseter, and deep masseter, opposed along the jaw by the pterygoideus
14 The dermatocranium lies superficial to the neurocranium & forms the bones of: Roof of the brain: nasals, frontals, parietals, post parietalsPosterior angle of skull: intertemporal, supratemporal, tabular, squamosal, quadratojugalAround orbits: lacrimal, prefrontal, postfrontal, jugal (infraorbital), postorbitalThe upper jaw: premaxilla, maxilla
15 The lower jaw: splenial, postsplenial, angular (tympanic bulla), surangular, prearticular (anterior malleus in mammals), coronoids, dentaryThe palate: para sphenoids, vomer palatines, pterygoids, ectopterygoids (cover palato quadrate)The operculum in fishes
16 PALATAL BONES – the primary palate is the floor on which the brain rests, & the roof of the oral cavity in fishes & amphibians; remain cartilaginous in sharks.Birds, mammals, some reptiles:A secondary palate (plus a soft palate in mammals) develops from processes of the premaxillae, maxillae, and palatines, creating a horizontal partition that separates the oral cavity into nasal & oral passagesAllows chewing and breathing simultaneouslyParasphenoid is lost and internal nares is displaced caudad when palate forms
17 Evolution of the mammalian bony palate: dermal bones of the margin of the oral cavity expand medially to house nasal passages from external nares to choanae.
18 3. SPLANCHNOCRANIUM Cartilage blastema origin is neural crest Consists of typically 7 gill or skeletal visceral/ branchial arches1st MANDIBULAR ARCHDorsal half forms the primitive upper jaw, the palatoquadrate or pterygoquadrateLower half forms the lower jaw, the Meckel’s cartilageThe upper jaw becomes incorporated into the skull, while the lower jaw forms a movable joint with it.
19 PALATOQUADRATE CARTILAGES: Unossified in tetrapods, function is taken over by dermal bonesOssifications occur only in the ascending process (epipterygoid bone), and in the otic process (quadrate bone) which becomes an immovable part of auditory region (except in streptostylic conditions which permits wide gape for swallowing large prey)MECKEL’S CARTILAGES:Anterior mentomeckelian bone of amphibiansAt the rear is the articular bone which articulates with the quadrate bone of the upper jaw (autostylic suspension)
20 2nd HYOID ARCH and other gill arches: Composed of dorsal paired hyomandibular cartilages, and lateral gill-bearing ceratohyals of elasmobranchs.The remainder and the other 5 arches contribute to the hyoid apparatus and laryngeal cartilages of tetrapods.Operculum is the fold of the hyoid arch that extends over the gill slits in holocephalans & bony fishes; in tetrapods no vestiges of opercular bones remain
21 HYOID CARTILAGESHyomandibular cartilage ossifies to form hyomandibula of fishes and suspend lower jaw (hyostylic suspension); in tetrapods, it gives rise partly to the columella of the earRemainder of hyoid arch fuse with gill arches to form hyobranchial skeleton consisting of:Hyoid apparatus - serves as support for tongue and larynx, muscle attachment, buccal respiration of amphibiansLaryngeal cartilages- support voice box chamber
22 3. FORMATION OF THE COMPLETE SKULL CENTERS OF OSSIFICATION appear which converts the chondrocranium into a complete skull that consists of:Cartilage bones ossified in the chondrocranium, sense capsules, hyoid and mandibular archesDermal bones covering the cartilage bones everywhere except on midventral surface and posterior end of the skull.Degree of ossification is greater in higher members of each group; cartilaginous skulls result from retrogressive processes.
23 OCCIPITAL CENTERSOccipital group: encircling the foramen magnum are the: basioccipital, exoccipital (2), supraoccipitalIn mammals, all 4 occipital elements typically fuse to form a single occipital bone surrounding the foramen magnum
24 Occipital condyles are projections by which the skull articulates with the atlas. Fishes and primitive tetra pods have only condyle formed by basioccipital and partly by exoccipital.2 condyles present in amphibians and mammals result from reduction of basioccipital and enlargement of exoccipital.
25 SPHENOID CENTERSPosterior sphenoid group: basisphenoid, pleurosphenoid (not the mammalian alisphenoid, epipterygoid location)Orbitosphenethmoid region: presphenoid, orbitosphenoids, mesethmoid.In mammals, the basicranial axis is occupied by: basioccipital, basisphenoid, presphenoid, mesethmoid (absent in some)
26 ETHMOID CENTERS Remain cartilaginous & form anterior to sphenoid In most mammals, the nasal chamber is large & filled with ridges from the ethmoid bones called the turbinals or ethmoturbinals.These bones are covered with olfactory epithelium in life and serve to increase the surface area for a more acute sense of smell (olfaction).Another ethmoid bone, the cribriform plate, separates the nasal chamber from the brain cavity within the skull.
27 SENSE CAPSULES:OTIC - the cartilaginous otic capsule is replaced in lower vertebrates by several bones: prootic, opisthotic, epiotic, pterotic, sphenoticOne or more of these may unite with adjacent replacement or membrane bones:Frogs & most reptiles - opisthotics fuse with exoccipitalsBirds & mammals - prootic, opisthotic, & epiotic unite to form a single petrosal (periotic or petromastoid) bone; the petrosal, in turn, sometimes fuses with the squamosal to form the temporal boneOPTIC – gives rise to sclerotic bones around pupil of reptiles and birds (absent in mammals)
29 JAW SUSPENSIONSAutostyly (left) - hyomandibula has no role in bracing the jaws (lungfish & tetrapods)Amphistyly (middle) - jaws & hyomandibula both braced directly against the braincase (extinct sharks)Hyostyly (right) - mandibular cartilage is braced against the otic capsule; jaws braced against hyomandibula (sharks & present day bony fishes)
31 CROSSOPTERYGIANS- the dermatocranium forms a series of paired and unpaired bones along mid-dorsal line of skullLABYRINTHODONTS- these unpaired bones are lost but a series of paired bones resulted (nasals, frontals, parietals, & dermoccipitals)
32 AGNATHAChondrocranium: remains cartilaginous throughout life; skull roof is fibrous and protects brain & sensory structuresSplanchnocranium: no ancestral branchial skeleton; lingual cartilage bears horny teeth; continuous basket with branchial functionDermatocranium: no dermal armor
33 CHONDRICTHYESChondrocranium: calcified; with 2 occipital condyles and foramen magnum; otic and nasal capsules fused to neurocranium
34 Splanchnocranium: mandibular arch gives rise to palatoquadrate and Meckel’s cartilages; hyoid arch composed of hyomandibula, ceratohyal, basihyal cartilages
35 TELEOSTSNeurocranium: remain cartilaginous in chondrosteans, neopterygians, dipnoans; ossifies via the four ossification centers in most fishesDermatocranium: numerous dermal bones overlying neurocraniumSplanchnocranium: resembles that of sharks except that bone is added; anterior part of palatoquadrate ensheathed by dermal maxilla and premaxilla bones
36 Caudal ends undergo endochondral ossification & become the quadrate bone; the remainder becomes the palatine & pterygoid bones.Caudal part of Meckel’s cartilage ossifies as articular bones; remainder becomes invested by dentary and angular membrane bonesHyomandibula ossifies to become symplectic and interhyal bonesMoveable bony operculumHyostylic suspension (ray-finned fish); Autostylic suspension (Dipnoans); Amphistylic suspension (Crossopterygians)
37 AMPHIBIANSNeurocranium: remains cartilaginous except for sphenethmoid, prootics, exoccipitalsDermatocranium incomplete (lacrimals and prefrontals only)lacks temporal region2 occipital condylesSplanchnocranium: larval stages have fish-like gills supported by gill archesforms altered primary palate with large vacuities to allow retraction of eyeballs
38 Jaw suspension: Quadrate of upper jaw articulates with articular of lower jaw (autostylic suspension)Hyomandibula is no longer needed since the jaw has an autostylic suspensionIt is freed up and becomes a rudimentary stapes called the columella
39 The rest of the hyoid arch plus arches III and IV become the hyoid apparatus for tongue support Visceral arch V is no longer needed and becomes the new larynx; arches VI and VII are absent
40 REPTILES Neurocranium: Well ossified, with fewer bones, and single occipital condyleDermatocranium:Many bones, but fewer than bony fish; crocodilians retain the largest numberIn many lizards, a parietal foramen houses a median eye
41 Splanchnocranium:Similar to amphibians; snakes have vestigial branchial skeletonStapes – functional columellaHyoid apparatus: larynxQuadrate-articular joint forms autostylic suspension; forms part of the kinetic mechanism of the skullThe hyoid consists of a body and 2 or 3 horns (cornua) in the pharyngeal walls.The entoglossus, a long bony process extends from the hyoid body forward into a long darting tongue (snakes, lizards, birds).
43 Formation of partial or complete secondary palate Development of temporal fossae bounded by arches: infratemporal arch (below ventral fossa); zygomatic arch (infratemporal arch); supratemporal arch (below dorsal fossa)
44 CRANIAL KINESISIndependent movement of one or more skull bones, especially between the upper jaw and braincase; e.g., a pivoting quadrateResults from reduction or loss of arches along with presence of intracranial jointsAdvantages:provides a way to change the size and configuration of the mouth rapidlyoptimize biting and rapid feedingDisadvantages: lose force, hard to optimize apposition of occlusive surfaces
45 These fossae and arches provide room for huge chewing muscles which allows rotary chewing
47 BIRDSNeurocranium- thin, highly vaulted or domed, but basically a reptile skullDermatocranium:Modified diapsid: supratemporal arch is lost, one big opening confluent with orbitBeak instead of teeth; premaxilla & dentary elongatedSplanchnocranium- similar to reptilesPivoting quadrates allow cranial kinesis although ectopterygoids are absent, and immobile parasphenoid is fused to basisphenoid.When quadrate is pushed forward, the motion is transmitted to upper beak via a movable palate, a movable zygomatic arch, or both.
48 MAMMALS Neurocranium: Larger, fewer bones due to fusion; sutures found between skull bonesSkull increasingly domed as cerebral hemispheres increase is sizeNeurocranium is incomplete dorsally, resulting to fontanels (a bregmatic bone ossifies and forms an anomaly in human skulls)Petrosal (periotic) bones form in the otic capsules2 occipital condyles
49 Dermatocranium:Decreased number of bonesSynapsid skull; zygomatic arch varies from massive to slender, even incomplete in insectivoresAir-filled cranial sinuses: frontals sinuses extend into horns; sinusitis is a common aliment in humansPresent in Homo erectus and Mongolians, is a postparietal or Inca bone
50 Temporal complex has intramembranous and endochondral origin: Squamous portion- squamosal of lower tetrapodsTympanic bulla- unique to mammals and encloses the middle ear; tympanic bone surrounds the eardrum, entotympanic bone represents the bullaPetrous portion- ossified otic capsuleMastoid portion- new in mammals; dorsal part of hyoid arch may fuse to mastoid to form styloid processTympanic and petrous portions unite to form petrotympanic bone
52 Pterygoids become reduced as winglike processes of the sphenoid 3 pairs of turbinal bones (nasal conchae) develop in the nasal passageways: superior concha is covered with olfactory epithelium; the 2 lower conchae are covered by nasal epithelium with venous plexuses that warm the air en route to the lungs
53 Squamosal articulates with dentary bone, which is sole lower jaw bone
54 Splanchnocranium: unossified tips of palato-quadrate and Meckelian cartilages give rise to middle ear ossicles, along with the columella:quadrate becomes incusarticular becomes part of malleushyomandibula has already became stapes
57 Hyoid apparatus and larynx: Consists of a body & 2 or 3 horns (cornua);Anchors tongue, provides Attachment for some extrinsic muscles of larynxSite of attachment of muscles that aid in swallowing
58 In addition to cricoid and arytenoid cartilages common to tetrapods, mammals have thyroid cartilages arising from the 4th and 5th arches
59 ARCHSHARKTELEOSTFROGREPTILEMAMMAL1PalatoquadrateMeckel’scartilageQuadrateEpipterygoidMetapterygoidArticularAmmulus tympanicusMentomeckelianIncusAlisphenoidMalleus2HyomandibulaCeratohyalBasihyalSymplecticInterhyalEpihyalHypohyalColumella (stapes)Anterior horn of hyoidBody of hyoidEntoglossusStyloid process3PharyngobranchialEpibranchialCeratobranchialHypobranchial2nd horn of hyoid4Branchial skeletonLast horn of hyoidThyroid cartilages5Cricoid and arytenoids6Not present7
60 EVOLUTIONARY CHANGES IN MAMMALIAN SKULL: Loss of connection between head and pectoral girdle to create neck in primitive tetrapodsIncreasing skull strength through simplification by loss of bones and articulationsBraincase evolution reflecting enlarged brainChanges in sense organs (e.g., in median pineal-parietal eye complex and loss of pineal foramen)Development of secondary palate and respiratory passagesTemporal fenestration and jaw adductor differentiationChange from quadrate-articular to dentary-squamosal jaw joint with concomitant development of three middle ear bones
61 Homologies among bones are difficult to establish Sagittal section through skull of ancestral amniote and mammal to show evolution of bones that form braincase; note that the epipterygoid of the primitive amniote splanchnocranium is homologous with alisphenoid in mammals.
62 REGIONAL SERIES OF DERMATOCRANIAL BONES IN EARLY TETRAPOD
64 TEETH: teeth of vertebrates are homologous to the placoid scale of elasmobranchs. Usually of simple form and all alike among lower tetrapods, they become heterodont (several kinds), and thecodont (set in sockets in jaw bones).Borne in lower tetrapods on various jaw and palatal bones, they become limited in higher ones to the jaw margins.Teeth of mammals: incisors, canines, premolars, molars; juvenile (no molars), and permanent setsTrituberculate theory of mammalian tooth origin: 2 cusps arising from a ridge (cingulum) from neck of tooth are added to simple reptilian tooth. Teeth of upper jaw are slightly behind those of lower jaw.
65 HUMAN AND ANTHROPOID APE SKULL: large, rounded cranial portionflattened facial portion, vertical orientationcomplete separation of the orbits from the temporal fossaereduction of the nasal cavities and turbinalslarge mastoid processabsence of a tympanic bullaextensive fusions of the skull bonesunspecialized teeth: 2 incisors, slightly enlarged canines, bunodont (separated rounded cusp) molars
67 Name the bones of the neurocranium of a basal craniate, and their fused derivatives. What major steps occurred in the phylogenetic development of the “complete” cranium?Tabulate: regions of ossification in the cranium, and the bones present in each region of the teleost, amphibian, reptilian, and mammalian skulls.Tabulate: pharyngeal arches of basal vertebrate, and their homologues in teleost, amphibians, reptiles, mammalsTabulate: dermal bones in each of these regions of the teleost, amphibian, reptilian, mammalian skull: roof, upper and lower jaw, palateDescribe the phylogenetic patterns for the craniate temporal fossae, and their fuctional role in each group.Name the bones that contribute to the formation of the primary and secondary palate.List the types of jaw suspension, and their participating bones.Discuss the phylogeny of the mammalian middle ear bones.What is the functional significance of cranial kinesis?
68 THE APPENDICULAR SKELETON NEXT…THE APPENDICULAR SKELETON