IB 303- Skeleton

Exam 1 content

Ontogeny

Embryonic development

Gastrulation

the phase during embryonic development where the single-layered blastula reorganizes into a multi-layered structure called the gastrula. Creates the gut.

Neurulation

Process of forming the neural tube, after the gut formation

Organogenesis

The process of organ formation in the developing embryo, following gastrulation and neurulation.

Maturation

Process from birth/hatching to adulthood

Ectoderm

Germ layer that gives rise to the skeletal tissue

Mesoderm

Germ layer that gives rise to the muscular/cardio/reproductive tissue

Endoderm

Germ layer that gives rise to the gut/digestive tissue

Ontogeny recapitulates phylogeny

The old hypothesis for ontogeny that states embryos go through all stages of evolution while developing.

“Fish-phase”

Law of the general to the specific

The alternative hypothesis for ontogeny that states embryos are undifferentiated and later develop taxon-specific features

No “fish-phase”, all vertebrates have same general features

Pharyngeal pouches

Bays inside embryonic pharynx, becomes pharyngeal slits in fish but don’t open in terrestrial vertebrates

Biomechanics

Study of biological function: Locomotion, Feeding, Defense, Fighting, reproduction

Fusiform shape

The best shape for movement through a body of water where the widest portion is about 1/3 behind the front

Square-Cube Law/Scaling

Volume increases faster than area/consequence of growth

Stress

The force/area, which causes things to break

Isometry

Everything (biological bodies/structures) grows at the same rate

Allometry

Everything (biological bodies/structures) grows at a proportional rate

Falling

The more mass, the faster the fall and vice versa

Exoskeleton

Derives from the dermis or epidermis

Endoskeleton

Derived from the mesoderm within the body

Endochrondral Bone

The ossification of long bones and the base of the skull from hyaline cartilage

Dermal bone

Ossifies skull, jaws, and shoulder girdle directly from fibrous membranes. Similar to exoskeleton of turtles

Chondrocranium

endochondral, initially formed from cartilage and becomes bone

in cartilage fish: may mineralize but does not become bone

“Brain case”, nasal capsule, and otic capsule

Splanchnocranium

endochondral, oldest of the three structures

composed of a series of arches that originally supported the gill slits, now supports the jaw

Dermatocranium

Dermal bone that originally bony armor in early fish

encase majority of skull in amniotes, makes the pre maxilla and maxilla

reduces in modern fish and amphibians

Palatoquadrate

Splanchnocranium bone that makes up the upper palate(upper jaw)

has the Quadrate and Epipterygoid

Meckel’s Cartilage

Splanchnocranium bone that makes up the lower jaw

persists in some osteichthyans but encased in dermal bone, posterior end forming an articular

surrounded in dermal bone at jaw to become the dentary

Hyomandibula

Splanchnocranium bones that are connected to the jaw to suspend it

Serial Theory

The theory that jaws evolved from a single brachial arch

Composite Theory

The theory that jaws evolved from parts of several brachial arches

Skull Fenestration

The increase of “holes”/”openness” in the temporal region of the skull

Anapsid

No hole in temporal region of skull

Ex. Turtles

Synpsids

One hole in temporal region of skull

typically found in mammals

Some are merged with orbital opening

Diapsid

Two holes in temporal region of skull

typically found in reptiles

Can be extreme “openness”

Cranial Kinesis

The increase(or decrease(mammals)) of skull mobility

Sharpey’s fibers

How muscle attaches to bone

attaches more securely to edges, making fenestration favorable

Secondary Palate

Evolved feature that is a barrier between nasal canal and oral canal to keep air and food separate

Pterygoid Walk “tera-goid”

Mobile bones that allow disconnecting of one side of jaw bone at a time to “walk” jaw over large pray in snakes

Vertebral segments

comprise the vertebral column, arches and centra

Dorsal Arches

protect neural tube

they are neural and interneural structures