[2] Lecture 10-skeletal System 2 Flashcards by John Pate

Components of the vertebrate skull organization:

Chondrocranium:
Neurocranium and splanchnocranium

Dermatocranium

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Neurocranium forms the

Braincase

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Splanchnocranium forms the

Gill arches

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DO we have dermal bone?

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The braincase or neurocranium has 3 pairs of cartilaginous capsules housing special sensory organs [capsules]:

Olfactory
Optic
Otic

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The floor of the braincase or neurocranium forms from 2 pairs of cartilaginous plates,explain:

Parachordals: flank [side] the notochord

Prechordals: in front of notochord

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Hole spinal cord exits from braincase:

Foramen magnum

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Asso. W/ sense of smell

Olfactory

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Asso. W/ sense of sight

Optic

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Asso. W/ sense of balance

Otic

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Below the Foramen magnum

Basioccipital

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Paired; lateral to foramen

Exoccipital

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Above the Foramen magnum

Supraoccipital

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Endochondral ossifications:

Basioccipital
Exoccipital
Supraoccipital
Basisphenoid/presphenoid

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How many pairs of cartilaginous or bony arches make up splanchnocranium?

6 pairs

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1st and second arches of the splanchnocranium:

Mandibular and hyoid arch

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Dorsal and ventral part of mandibular arch:

Dorsal: palatopterygoquadrate bar- ossification=sphenoid

Ventral: meckel’s cartilage: quadrate and articular

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What does the hyoid arch do in many fishes?

It braces the palatopterygoquadrate bar against the braincase

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When the hyoid arch [derived from the 2nd gill arch] braces the upper jaw against the neurocranium

Hyostylic articulation

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When the upper jaw is fused to the brain case:

Autostylic articulation

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Ex of hyostylic jaw:

Elasmobranchs, holosteans, teleosts, and dipnoans

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Ex of autostylic jaw:

Chimaeras and lungfishes

Jaw articulation is between quadrate and articular

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Primitive tetrapods to amphibians skull:

Reduction in dermal bones,
Retention of considerable cartilage,
Paired occipital condyles,
Autostylic jaw articulation,

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Dermal skull elements of primitively tetrapods

Primitive tetrapods had a lot of dermal bones and they’re named as human bones but not really sure if they are same bone…
Many bones are no longer in human anatomy, so they were lost. But some are still there.

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Amphibian dermal series: Cheek:

Squamosal | Quadratojugal: forms cheek arch

Amphibian dermal series Tooth-bearing:

Premaxilla | Maxilla

Generalization Reptile skull:

Well ossified, Boxlike skulls->arches and openings, Dermatocranium reduced, Single median occipital condyle, Well-developed jaw muscles r/t muscle attachment on side of skull- arches and openings. Many reptilian dermal bones rate homologous w/ mammal skulls.

No arches and no additional openings

Anapsid

Ex of anapsid

Cotylosaurs [and maybe turtles]

Both lateral and dorsolateral openings- 2 arches

Diapsid -found in most reptiles

Ex of diapsid:

Sphenodon,

May be a variant of a diapsid skull | Single dorsolateral opening bounded inferiorly by postorbital and squamosal bones

Euryapsid [parapsid]

Ex of Euryapsid [parapsid]

Plesiosaurs and icthyosaurs

Found in mammal-like reptiles and mammals. | Single opening bounded inferiorly by the zygomatic arch

Synapsid-mammals----us

Reptilian emargination on superior skull:

Allows muscle to attach for strong neck attachment to head and body

One of the benefits of zygomatic arch:

Allows for increase SA of muscle to have more forcible bite

Jaw articulation in reptiles and amphibians is:

Between the articular and quadrate =autostylic

Articular is dervied from the proximal end of

Meckel's cartilage 1st branchial arch

Quadrate is derived from proximal end of

Palatopterygoquadrate cartilage 1st branchial arch

Hyomandibular is no longer need to brace upper jaw against braincase what happens to it?

It becomes the columella [stapes forms proximal portion] Extends from the tympanic membrane to fenestra ovalis

Opening into inner ear

Fenestra ovalis

1st gill slit becomes=

Eustachian tube

Amphibian and reptile jaws are

Autostylic

Amphibian vs. reptile tympanic membrane:

Amphibian-high Reptile-low

What happens in between amphibian and reptile development w/ ear?

The quadrate and articular in amphibian which is a part of the mandible becomes malleus [articular] and incus [quadrate] in reptile. Stapes became longer in reptile.

Ossifications from the palatopterygoquadrate

Epiterygoids

Floor of the braincase

Basisphenoid

Pelycosaurs braincase:

- not fused to epipterygoids | - epipterygoids do not extend to dermal roof.

Therapsids braincase:

Basisphenoid (braincase floor) fused to epiterygoids and pterygoids Epipterygoids do not extend to dermal roof

Mammal braincase:

Basisphenoid fused to epipterygoids and pterygoids Epipterygoids extend to dermal roof

Serves as sites for muscles involved in jaw movement in mammals:

Pterygoid plates

Primary palate

Floor of braincase --- Human- roof of nose

Secondary palate consists of:

Premaxillae Maxillae Palatines

Function of secondary palate:

Separate food stream from air stream

Why can cleft palate occur?

The bone is formed from the outside-in...sometimes it doesnt meet up completely.

Development of secondary palate is especially important in:

homeotherms

Zygomatic arch is formed by:

Jugal and squamosal bones

Crests for muscle attachment:

Sagittal and nuchal crest

Mammalian jaw articulation:

Crainostylic Btw Denmark and temporal bones

What happened to quadrate and articular:

Incus and malleus in middle ear

CLearly define structures at TMJ human:

Capsule Temporomandibular ligament Stylomandibular ligament

Attachment for falx celebri :

Crista Galli

4 skull sutures:

Sagittal Lambdoidal Coronal Frontal

4 fontanelles

Anterior Posterior Posterolateral Anterolateral

Superior and posterior boundary of temporal

Inferior temporal line

Anterior boundary of temporal

Frontal process of zygomatic

Inferior boundary of temporal

Zygomatic arch

Floor of temporal [4 components]:

Greater wing of sphenoid Squamous temporal Frontal parietal

What is in temporal region:

Temporalis muscle Deep temporal nerve and arteries Zygomaticus nerve

Attachment of temporalis fascia

Superior temporal line

Attachment of temporalis muscle

Inferior temporal line

Elevates and protracts mandible

Masseter

Elevates and retracts mandible

Temporalis

Protracts mandible; depresses chin[bilateral; grinding(unilateral)]

Lateral pterygoid

Elevates, protracts, grinding [unilateral]

Medial pterygoid

Between head of mandible (condyloid process) and mandibular fossa of temporal bone, what type of joint:

Synovial joint

Capsule of TMJ allows:

Mandible to protracts, retract, and elevate/depress

TMJ 3 ligaments:

Temporomandibular Stylomandibular Sphenomandibular