Skulls - Components, jaws Flashcards Preview

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Flashcards in Skulls - Components, jaws Deck (33):
1

Function of branchial arches III-VII in most fish

Support gills

2

Who has modified hyostyly?

Actinopterygii

3

What does the splanchnocranium form?

7 branchial arches & their derivatives (jaws, middle ear bones)

4

What feeding method do actinopterygiians use?

Suction feeding

5

Embryonic origin of splanchnocranium

Neural crest cells (-> cartilage, ossifies in most teleostomi)

6

Describe branchial arches III-VII

Made of 5 pieces (usually)

7

Precise functions of dermatocranium

-Cover chondrocranium & brain (dorsal, ventral)
-Cover & protect gills (opercular bone)
-Cover parts of jaw splanchnocranium

8

Describe modified hyostyly

Quadrate: Articulation point of upper jaw, not fused to chondrocranium
Articular: Articulation point lower jaw
Hyomandibula & symplectic bone: suspend jaws from chondrocranium
-> Many joints = highly kinetic (suction feeding)

9

Describe paleostyly

All branchial arches used to support gills; no jaws

10

Lower jaw bone in teleostomi

Dentary (encases Meckel's cartilage except for ossified back portion; part of dermatocranium)

11

General function of dermatocranium

Form hard, protective structures

12

Function of branchial arches III-VII in amniotes

Form cartilage around trachea & larynx

13

Who has a dermatocranium?

Teleostomi (Osteichthyes, Tetrapods, not Agnathans, Chondrichthyes b/c no bone)

14

Who has paleostyly?

Agnathans

15

Adaptations of actinopterygiian skull to feed by biting prey

2° loss of cranial kinesis by bone fusion to provide strength

16

Upper jaw bones of teleostomi

Premaxilla, maxilla (dermatocranium)

17

Embryonic origin: chondrocranium

Neural crest cells, mesodermal mesenchyme

18

Describe Autostyly

Palatoquadrate: Upper jaw, fused to chondrocranium
Meckel's cartilage: lower jaw
Hyoid arch: gill support

19

Embryonic origin & final tissue type: Dermatocranium

Mesenchyme from dermatome epimere mesoderm -> Dermal bone

20

Who has hyostyly?

Most sharks

21

Describe metautostyly

Quadrate (upper) and articular (lower) form jaw joint; quadrate fused or articulates w/ chondrocranium; II -> columella in middle ear (not for jaw suspension)

22

Who has craniostyly?

mammals

23

Describe adaptations of actinopterygiian skull for suction feeding

1. Maxilla connected loosely to chondrocranium & lower jaw (rotates forward as jaw opens)
2. Premaxilla connected loosely to maxilla (can be projected forwards faster)
3. Chondrocranium rotates at spinal connection (rises as lower jaw drops)
4. Hyoid apparatus: struts in buccal cavity floor, pulled perpendicular to push out lateral walls as mouth opens
=> Creates suction

24

How does hyostyly affect feeding?

Allows jaws to swing forwards to open wider & for teeth to contact prey at same time (good for grabbing slippery prey)

25

Regions of brain protected by chondrocranium

All vertebrates: ventral, lateral, posterior
Agnathans & chondrichthyans: dorsal (-> forms entire braincase)

26

Chondrocranium tissue type

Cartilage: initially, all; remains in agnathans, chondrichthyes
Bone (replacement): teleostomi

27

Who has metautostyly?

Amphibians, sauropsids

28

Who has autostyly?

Holocephali (ratfish), dipnoi (lungfish)

29

Describe hyostyly

Palatoquadrate: Upper jaw, not fused to chondrocranium
Meckel's cartilage: lower jaw
Hyomandibula: Forms swinging bridge attaching jaw to chondrocranium
-Spiracle: reduced pharyngeal slit between mandibular & hyoid arches

30

Describe amphistyly

Palatoquadrate: upper jaw, held to chondrocranium by ligament
Meckel's cartilage: lower jaw
Hyomandibula: stabilizes back of palatoquadrate, also gill support

31

3 components of the skull

Chondrocranium, splanchnocranium, dermatocranium

32

Describe craniostyly

Entire upper jaw fused to chondrocranium
Dentary (lower) articulates with squamosal (upper)
Jaws entirely dermatocranium
I & II in middle ear
Quadrate -> Incus
Articular -> Malleus
Hyomandibula -> Stapes

33

Who has amphistyly?

6-gilled sharks