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Comparative Anatomy > Lecture 10 > Flashcards

Lecture 10 Flashcards

1
Q

Generalizations of Reptilian Skull

A
  • well ossified
  • modern forms have developed arches and openings (primitive more boxlike)
  • elements of dermatocranium are reduced in modern forms
  • many reptilian dermal bones are homologous with mammal skulls
  • single median occipital condyle
  • jaw musculature well-developed:
    - related to development of increase in surface areas on sides of skill for muscle attachment and the development of the openings and arches
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2
Q

Anapsid Skull

A
  • no arches and no additional openings

- found in cotylosaurs and turtles

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3
Q

Diapsid skull

A
  • both lateral and dorsolateral openings
  • two arches
  • found in most reptiles
    - both arches are present in Sphenodon
    - lizards have lost the lower arch
    - snakes have lost both bars
    - this frees the quad rate and allows for a more movable lower jaw to give them more mobility
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4
Q

Euryapsid (Parapsid) Skull

A
  • may be variant of a Diapsid skull
  • single dorsolateral opening bounded inferiority by postorbital and squamousal bones
  • found in plesiosaurs and icthyosaurs
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5
Q

Synapsid skull

A
  • found in mammal-like reptiles and mammals

- single opening bounded inferiority by the zygomatic arch

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6
Q

Vertebrate skull in Sharks, Skates, and Rays

A

Formed entirely of cartilage; failure to replace cartilage with bone in the adult is an example of neoteny

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7
Q

Vertebrate skull organization

A

Composed of the chondrocranium and dermatocranium

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8
Q

Chondrocranium

A

Neurocranium:
-aka the brain case
Splanchnocranium:
-aka pharyngeal gill arches

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9
Q

Neurocranium

A
  • Braincase
  • cartilage and/or endochondral bone
  • Includes three pairs of cartilaginous capsules housing special sensory organs:
    - Olfactory (most anterior)
    - Optic
    - Otic (most posterior)
  • floor forms two pairs of cartilaginous plates
    - Parachordals
    - Prechordals
  • posterior wall
  • roof
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10
Q

Endochondral ossifications of neurocranium

A

Basioccipital:
- Below foramen magnum

Exoccipital:
- Paired lateral to foramen

Supraoccipital:
- Above foramen magnum

Basisphenoid (and presphenoid)

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11
Q

Splanchnocranium

A

Six pairs of cartilaginous or bony arches:
- 1st arch
-Mandibular arch:
Dorsal part= palatopterygoquadrate bar
-ossifications=epipterygoids

            Ventral part= Meckel's cartilage 
                 -ossifications=quadrate and articular -2nd arch
   -Hyoid arch 
            In many fishes, it braces the palatopterygoquadrate bar against the brain case
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12
Q

Types of jaw suspension in fishes

A

Hyostylic and Autostylic

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13
Q

Hyostylic Jaw Suspension

A

-hyoid braces upper jaw against neurocranium

Examples: Elasmobranchs, holosteans, teleosts, and dipnoans

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14
Q

Autostylic Jaw Suspension

A
  • upper jaw is fused to Braincase
  • jaw articulation is between quadrate and articular

Example: chimaeras and lungfishes

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15
Q

Modern Amphibian Skull

A
  • reduction of dermal elements
  • retention of considerable cartilage
  • paired occipital condyles
  • autostylic jaw articulation

Hyomandibular=columella

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16
Q

Dermal skull elements of primitive tetrapod

A 
Roof series:
     Nasal
     Frontal
     Parietal
     Postparietal 
Circumorbital series:
     Prefrontal
     Postorbital
     Jugal
     Lacrimal

Temporal series:
Intertemporal
Supratemporal
Tabular

Cheek series:
Squamosal
Quadratojugal
*^may form part of the zygomatic arch

Lateral tooth-bearing series:
*Forms margins of upper jaw.
Premaxillary
Maxillary bones

17
Q

Example of neoteny:

A

Failure to replace cartilage with bone in the adult

18
Q

Vertebrate skull

A

Forms the other part of the axial skeleton

  • may be formed entirely of cartilage
  • may be a combination of cartilage, dermal bone, and/or endochondral bone

In vertebrates, brain case develops in the embryo as an incomplete cartilaginous box with numerous openings (foramina) thru which pass nerves and blood vessels to and from the brain
-additional cartilaginous capsules develop to enclose the special sensory organs such as olfactory apparatus, eyes, and semicircular canals (balance)

19
Q

Reptilian skull: generalizations

A
  • well ossified
  • primitive forms had boxlike skulls, modern have developed arches and openings
  • elements of dermatocranium are reduced in modern forms
  • many reptilian dermal bones are homologous with mammal skulls
  • single median occipital condyle
  • jaw musculature well-developed
  • related to development of the increase in surface areas on sides of skull for muscle attachment and the development of the openings and a Rachel
20
Q

Reptilian skull arches and openings: Anapsid

A

No arches and no additional openings

Found in cotylosaurs and turtles

21
Q

Reptilian skull arches and openings: Diapsids

A

Both lateran and dorsolateral openings

2 Arches

Found in most reptiles:

  • both arches are present in Sphenodon
  • lizards have lost the lower arch
  • snakes have lost both bars:
    • this frees the quadrate and allows for more movable lower jaw
22
Q

Reptilian skull arches and openings: Euryapsid (Parapsid)

A
  • May be a variant of a diapsid skull
  • Single dorsolateral opening bounded inferiority by postorbital and squamosal bones
  • Found in plesiosaurs and icthyosaurs
23
Q

Reptilian skull arches and openings: Synapsids

A
  • Found in mammal-like reptiles and mammals

- Single opening bounded inferiority by the zygomatic arch

24
Q

Tetrapod jaw articulation

A

Jaw articulation is between the articular and quadrate

  • Autosylic
  • The articular arch is derived from the proximal end of Meckel’s cartilage (first branchial arch)
  • The quadrate is derived from the proximal end of the palatopterygoquadrate cartilage (first branchial arch)
    - the hyomandibular is no longer needed to brace the upper jaw against the braincase
    - the hyomandibular forms the columella (the stapes forms from the proximal portion)
    - the stapes extends from the tympanic membrane to the fenestra ovalis (opening into the inner ear chamber)
25
Q

Jaw articulation: Amphibians vs. Reptiles

A

Amphibian:
- Tympanic membrane high

Reptile:
- Tympanic membrane low

Both:
- Both are autostylic

26
Q

Development of braincase floor

A

Pelycosaurs:

  • floor of braincase= basisphenoid
    - not fused to epipterygoids
    - epipterygoids do not extend to dermal roof

Therapsids:

  • Basisphenoids fused to Epipterygoids and pterygoids
  • Epipterygoids do not extend to dermal roof

Mammals:

  • Basisphenoids fused to epiterygoids and pterygoids
  • Epiptergoids extend to dermal roof
27
Q

Development of secondary palate

A

-Primary palate=floor of braincase

  • Secondary palate from:
    • Premaxillae
    • Maxillae
    • Palatines

Function:
-Separates food stream from air stream

Especially important in homeotherms
Found in:
   -Crocodilians
   -Therapsids
   -Mammals
28
Q

Mammalian Skull

A
  • Synapsid
  • Contains a Zygomatic arch from jugal and squamosal bones
  • Loses some dermal elements
  • Development of crests for muscle attachment:
    • Sagittal crest
    • Nuchal crest

-Secondary palate

  • Jaw articulation
    • Craniostylic:
      • Between dentary and temporal bones
      • Quadrate becomes incus
      • Articular becomes malleus
29
Q

Temporal region of human skull

A

Boundaries:
Superior and posterior boundary:
-Inferior temporal line

Anterior boundary:
-Frontal process of zygomatic

Inferior:
-Zygomatic arch

Floor:

  • Greater wing of sphenoid
  • Squamous temporal
  • Frontal
  • Parietal

Contents:
Temporalis muscle
Deep temporal nerve and arteries
Zygomaticus nerve

30
Q

Temporal lines

A

Superior:
-for attachment of temporalis fascia

Interior:
-for attachment of temporalis muscle

31
Q

Muscles of mastication

A

All innervated by mandibular branch of CN V

Masseter
Temporalis
Lateral pterygoid
Medial pterygoid

32
Q

Masseter

A
  • Zygomatic bone to lateral surface of ramus and coronoid process
  • Elevates and protracts mandible
33
Q

Temporalis

A
  • Temporal fossa and fascia to coronoid process

- Elevates and retracts mandible

34
Q

Lateral pterygoid

A
  • Lateral pterygoid plate and sphenoid to font of mandible and TMJ
  • Protracts mandible; depresses chin (bilateral; grinding (unilateral)
35
Q

Medial pterygoid

A
  • Lateral pterygoid plate and maxilla to medial surface of mandible near angle
  • Elevates, protracts, grinding (unilateral)
36
Q

Synovial joint

A

-Between head of mandible (condyloid process) and mandibular fossa of temporal bone

  • Intervening cartilage:
    • Divides joint into superior and inferior compartments
    • Allows mandible to protract & retract as well as elevate & depress
37
Q

Ligaments of Temporomandibular Joint

A

Temporomandibular ligament:
-Base of zygomatic process to mandibular neck

Stylomandibular ligament:

  • Styloid process to angle of mandible
  • Runs between parotid and submandibular glands

Sphenomandibular ligament:

  • Sphenoid spine to mandibular lingula
  • Lies medial to TMJ

Comparative Anatomy (5 decks)

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