Types of Bone Endochondral = bone replaces a cartilage precursor. Intramembranous bone Dermal = bone forms in the connective tissue of the dermis. Sesamoid = bone forms in the connective tissue of a ligament. Perichondral / Periosteal bone = bone forms in connective tissue surrounding cartilage or bone.
The Skeleton Endoskeleton = forms within the body from mesoderm and sometimes neural crest (deep to the integument); bone or cartilage Exoskeleton = forms within the integument from mesoderm and mesoderm & neural crest (dermal bony scales, dermal bone); bone
Three Parts of the Cranium Chondrocranium = cartilage or endochondral bone, underlies (or surrounds) the brain. (endoskeleton) Splanchnocranium = cartilage or endochondral bone, “jaw” and gill arch skeleton. (endoskeleton) Dermatocranium = ossification of connective tissue in dermis, superficial to rest of cranium. (exoskeleton)
Chondrocranium Regions Ethmoid – between nasal/olfactory capsules, “nose” region Sphenoid – underlies brain, “eye” region and posteriorly Otic - otic capsules, “ear” region Occipital - around the foramen magnum human cranial cavity superior view (chondrocranium shaded)
Splanchnocranium Development Splanchnocranium from neural crest. Dermatocranium Development Dermatocranium from mesenchyme cells of the dermis, primarily mesoderm.
Dematocranium Nasals Frontal Parietals Maxillas Mandible/Dentaries Lacrimals Zygomatics/Jugals Vomer Palatines Pterygoid proc. of Sphenoids Squamous & Zygomatic parts of Temporals Postparietal/Interparietal portion of Occipital Chondrocranium Ethmoid Central part of Sphenoid Petrosal (Otic) portion of Temporal Supraoccipital, Exoccipitals and Basioccipital of Occipital Splanchnocranium Greater wing of Sphenoid Styloid process of Temporal Malleus, incus, & Stapes Hyoid Thyroid, Cricoid, and Arytenoid cartilages
nasal right frontal maxilla (includes premaxilla) sphenoid left frontal right frontal fontanelle
Human Secondary Palate Palatal shelves form it (maxillas & palatines); separates nasal & oral cavities Cleft palate = when fusion of the secondary palate does not occur. Cleft lip = when fusion of the maxillas (maxilla & premaxilla) doesn’t occur.
In non-mammalian gnathostomes the jaw joint is between the splanchnocranial quadrate (upper jaw) and articular (lower jaw). In all osteichthyans teeth (if present) are borne on dermatocranial bones, premaxilla & maxilla (upper jaw) dentary (lower jaw) In mammals the jaw joint is between the dermatocranial squamosal (upper jaw) and dentary (lower jaw). Jaw Elements
Tetrapod Skull frontal parietal post- parietal nasal quadratojugal squamosal maxilla pmx lacrimal jugal (zygomatic) post- orbital pre- frontal post- frontal dentary angular sur- angular italic underlined = absent in any form in human
Alligator Skull Sq QJ L PrF PO J mx pmx sur dent an nasals frontal parietal
Palatal Series vomer palatines pterygoids para- sphenoid
Amniote Orbital Series Group Pre- frontal LacrimalJugalPost- orbital Post- frontal turtlespresentabsentpresent absent lizards & snakespresent birdspresentabsentpresentabsent crocodylianspresent absent mammalsabsentpresent absent lacrimal jugal post- orbital pre- frontal post- frontal
Amniote Temporal Series Group SquamosalQuadratojugal turtlespresent lizards & snakespresentpresent in tuataras (absent in all others) birdspresent crocodylianspresent mammalsPresent (squamous part of temporal) absent quadrato- jugal squamosal
Amniote Skull Openings Space for muscle passage or flexure. No skull fenestras – turtles One skull fenestra bounded by postorbital, jugal, squamosal – mammals Two skull fenestras one bounded by postorbital, parietal, squamosal one bounded by postorbital, jugal, squamosal lizards & snakes and archosaurs (modified in most)
Amniote Skull Openings 1 opening2 openings no openings
Amniote Skull Openings no openings (turtles) 1 opening (mammals)
Amniote Skull Openings Montremata Metatheria Eutheria Testudines Lepidosauria Crocodylia Aves 1 opening 2 openings mandibular & antorbital fenestras
Nares Actinopterygiian nares Water flows in anterior naris, over olfactory epithelium, & out posterior naris.
Nares Tetrapod nares Air enters external naris flows over olfactory epithelium and exits into oral cavity through internal naris (choana).
Mammalian Compound Bones Palatines = dermopalatines + autopalatines Temporal bones = squamosals + otic bones + styloid processes (in some the styloid processes are separate) Occipital bone = supraoccipital + basioccipital + exoccipitals + fused post parietals (interparietal) (in many the interparietal is separate) Sphenoid bone = sphenoid bones (in some sep.) + alisphenoid (epipterygoid) + pterygoids (in some the pterygoids are sep.)
Secondary Palate (2º palate) = Premaxilla, maxilla, & dermopalatines separate nasal and oral cavities. Temporo-mandibular jaw joint New jaw articulation dentary/squamosal. Tympanic annulus, Malleus, & Incus Angular, articular, and quadrate become middle ear bones. Mammalian Skull